text stringlengths 454 608k | url stringlengths 17 896 | dump stringclasses 91
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Enis Soztutar commented on HBASE-13260:
---------------------------------------
It is mostly in the 1M regions jira, and some offline discussion with Stack.
> Bootstrap Tables for fun and profit
> ------------------------------------
>
> Key: HBASE-13260
> URL:
> Project: HBase
> Issue Type: Bug
> Reporter: Enis Soztutar
> Assignee: Enis Soztutar
> Fix For: 2.0.0, 1.1.0
>
> Attachments: hbase-13260_bench.patch, hbase-13260_prototype.patch
>
>
> Over at the ProcV2 discussions(HBASE-12439) and elsewhere I was mentioning an idea where
we may want to use regular old regions to store/persist some data needed for HBase master
to operate.
> We regularly use system tables for storing system data. acl, meta, namespace, quota are
some examples. We also store the table state in meta now. Some data is persisted in zk only
(replication peers and replication state, etc). We are moving away from zk as a permanent
storage. As any self-respecting database does, we should store almost all of our data in HBase
itself.
> However, we have an "availability" dependency between different kinds of data. For example
all system tables need meta to be assigned first. All master operations need ns table to be
assigned, etc.
> For at least two types of data, (1) procedure v2 states, (2) RS groups in HBASE-6721
we cannot depend on meta being assigned since "assignment" itself will depend on accessing
this data. The solution in (1) is to implement a custom WAL format, and custom recover lease
and WAL recovery. The solution in (2) is to have the table to store this data, but also cache
it in zk for bootrapping initial assignments.
> For solving both of the above (and possible future use cases if any), I propose we add
a "boostrap table" concept, which is:
> - A set of predefined tables hosted in a separate dir in HDFS.
> - A table is only 1 region, not splittable
> - Not assigned through regular assignment
> - Hosted only on 1 server (typically master)
> - Has a dedicated WAL.
> - A service does WAL recovery + fencing for these tables.
> This has the benefit of using a region to keep the data, but frees us to re-implement
caching and we can use the same WAL / Memstore / Recovery mechanisms that are battle-tested.
>
--
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How to Rename Package Name in Android Studio?
A package is a namespace that combines a set of relevant classes and interfaces. Conceptually one can consider packages as being similar to various folders on your computer. One might have HTML pages in one folder, images in another, and scripts or applications in yet another. Because in android, software written in the Java/Kotlin programming language can be made of hundreds or thousands of different classes, it makes sense to keep things organized by placing related classes and interfaces into packages.
A package is basically the directory (folder) in which source code resides. Normally, this is a directory structure that uniquely distinguishes the android application; such as com.example.app. Then the developer can build packages within the application package that divides the code; such as com.example.app.ui or com.example.app.data. The package for each android application resides within the src/main/java directory of the application module. The developer could put a different package within the application package to separate each “layer” of the application architecture.
There might be many situations when the developer wants to change the package name of the App in Android Studio. The developer might have download source code from the internet and requires to rename the package name according to his/her Application details. Here in this article, we are going to discuss step by step how to rename/change package name in Android Studio:
Step by Step Implementation
Step 1: To rename package name in Android studio open your project in Android mode first as shown in the below image.
Step 2: Now click on the setting gear icon and deselect Compact Middle Packages.
Step 3: Now the packages folder is broken into parts as shown in the below image.
Step 4: Now right-click on the first package name (com) and Refactor > Rename. A warning message will be displayed but go ahead and click on the Rename current button.
Step 5: Rename the directory name as your requirement and click on the Refactor button.
Note: Go to Build > Rebuild Project to display the updated name.
Now you can see your directory name changes from com -> gfg as shown in the below image.
Step 6: Do the same for the domain extension and App folder name according to your requirement.
Now you can see the package name has been changed from com.example.pulltorefreshwithlistview to gfg.geeksforgeeks.listview as shown in the below image.
Step 7: Now go to the build.gradle (Module: app) in Gradle Scripts. Here change the applicationId and click on Sync Now. And you are successfully renamed your package name. | https://www.geeksforgeeks.org/how-to-rename-package-name-in-android-studio/ | CC-MAIN-2022-21 | refinedweb | 444 | 56.55 |
The dos and don’ts of modeling
Recently I was asked to talk about modeling with our developers. What does modeling really mean? And how should you approach modeling? And how can you learn how to read models?
Prolog
In one of my previous jobs, I was a newly hired IT architect at mid size telecom company. Before this I had been programming and creating software solutions for about 15 years, but this was my first job as a “real architect”. One of the first things that ended up in my lap was this huge information model that a consultant had made for the company a year earlier. This model was really huge and it was all on just one page! And it contained these strange arrows that I had never seen before. I had to print it out in A3 size to be able to read the text and get the overview at the same time. I spent months (even years?) trying to get into this model, and really understand its implications.
About the same time, I was asked to create a systems overview of the IT architecture. Inspired by that big information model, I decided to crank it all into the same picture. I mean, that must be the way since you get both details and overview at the same time? I had multiple workshops with people who knew the details and spent weeks composing it all into one huge system model. I was really proud and felt like a real architect! When I presented the model, people looked a bit overwhelmed but I thought that it was normal and that they would learn how to read the model.
Back to the information model that I had been given before. When I finally had some really clever questions and really needed some answers, I called the consultant who had made the model and asked him. And he didn’t know the answers, because the model was too complex even for him. He actually started suggesting that the model needed to be expanded even more. That’s when I realized that there must be a better way.
Don’t crank everything into the same picture!
The problem with those big one-page models is that the only person who will ever understand them is the architect who made it. If you ever want someone else to understand your models, you need to break them up into smaller pieces. A good way to do this is to think about Resolution, Perspective and Target audience.
The idea here is that different people have different needs, and the models are created to meet those needs (they are not created just because an architect need to have something to do). If we take the Pointy Haired Boss, he will need something on a high level without too much detail (resolution), probably oriented around thing that cost (perspective), while our friend Alice the Project Manager need more details about things that need to be done and things that affect others. Dilbert the Developer needs the most detail since he will be implementing the system.
One person who realized this a long time ago was John A. Zachman. He made up his own framework called the Zachman framework. Although the Zachman framework is valuable, I believe that it is too complex for most situations. In my experience, the following Zachman “Light” approach covers most needs.
The idea with a framework like this is that you can choose what cell you want to create a model for. That model will be valuable to people who have the matching needs.
Let’s explain the framework by using an example. The classic Pet Store!
Let’s say that we are developing a web shop for the Pet Store. How would the models in each framework cell look?
Pet Store Models
Information domains
Resolution: Overview
Perspective: Information
Target audience: Everybody
The purpose of this model is to give a brief overview of the domain objects that are relevant to the business. It could also serve as a starting page for further drill down into the information models. The model does not conform to any formal modeling language.
Information domain model
Resolution: Specific
Perspective: Information
Target audience: Project management, team leads
In this area I chose to draw two different models, one ER model and one Concept model. I think both these modeling languages are very powerful, but have slightly different usages. The strength of the ER model is to explain the relationships between the domain objects, in terms of “one-to-one”, “one-to-many” and “many-to-many” relationships.
On the other hand, the Concept model is handy for describing more verbal relations such as “an Owner has a Pet” and “a Cat is a Pet”. Both of these modeling languages are easy to learn and are thus great tools to use in workshops with non-techy people.
Information class diagram
Resolution: Detailed
Perspective: Information
Target audience: Developers
The class diagram is almost as detailed as the programming code and may or may not be helpful. Once you get down to this level of detail, you need to be careful to not over do it, since the model may be obsolete very fast.
But I still think this is a valuable tool, especially when you want to explain something to someone else and it’s too complex to just look at the code.
A note about the modeling language UML. I have certainly struggled over the years to understand UML since it has a very different terminology than the one used when programming in an object oriented language. For example, when a programmer talks about Inheritance, the corresponding UML term is Generalization. I guess this is something we have to live with until someone invents a new modeling language that is more closely related to programming concepts.
System Context View
Resolution: Overview
Perspective: System
Target audience: Everybody
In this model, the objective is simply to place our target system on a map to see what relevant neighbours it has. What user groups it has, and what other systems it communicates with.
System Containers View
Resolution: Specific
Perspective: System
Target audience: Project management, team leads, developers
The purpose of this model is to drill down into the system and specify its major building blocks and how they relate to each other. The term Container is used since these are the building blocks that contain the code that we are going to develop.
Don’t get too technical here, it is more important to understand the relationships and information flow between the containers, than to worry about protocols and port numbers.
System Components View
Resolution: Detailed
Perspective: System
Target audience: Developers
In this model, we have drilled down into one of the containers in the previous model to show its most important parts. So what is a component then? Well, it is of course depending on what technology you are using, but if it’s Java or C# I would say that a component is a group of classes within a package/namespace, with a well defined interface in front. A component should have a purpose and it should be able to fulfil the tasks given to it. The arrows in the component view illustrates the direction of the method calls, which directly corresponds to the dependency order of the components.
Process Overview
Resolution: Overview
Perspective: Process
Target audience: Everybody
Here’s another high level model, this one represents the core process of the business that we are supporting, i.e. the Pet Store. It really looks like some kind of management fluff, and it is. But it can actually be useful as a starting point for understanding what people actually do in the business, and in what order.
Process Workflow
Resolution: Specific
Perspective: Process
Target audience: Project management, team leads, developers, UX
In this model, we have drilled down into the Sell Pets process in the overview and started to describe how we present our product to the user in the web shop, how the user picks a pet to buy and how she proceeds to perform the purchase. This model could be a great input to the UX team, since they are the ones that should detail the look&feel of each screen, and make sure that it has a logical and user friendly flow. Actually, it may very well be that the UX team draws this model to describe the flow to the development team.
Sequence Diagram
Resolution: Detailed
Perspective: Process
Target audience: Developers
This model is closely related to the Container and Component diagrams, but with a time perspective, and the purpose is to describe how the Containers or Components communicate in order to solve a specific task. In this example we have come to the Checkout flow where the customer purchase the pet and the system converts the purchase into an order in our ERP system. It also sends a confirmation email to the customer.
Conclusion
Now we have seen how a business and a system can be described by drawing several different models with different perspective and resolution. You may find that some of them are really useful, and some are not so useful. Which ones you use are really up to you. I certainly have my favourites! I hope that having read this article, you will find it a little bit easier to decide what type of model you should create in order to communicate just the thing you have been thinking of.
Further reading
I can truly recommend that you read the book Software Architecture for Developers by Simon Brown. It’s a real down-to-earth book about things that most developers care about. The Context, Containers and Components model that I use in the System perspective all come from this book. | https://medium.com/apegroup-texts/the-do-s-and-don-t-s-of-modeling-47aacdce55c8?source=collection_home---5------23----------------------- | CC-MAIN-2019-51 | refinedweb | 1,641 | 60.14 |
Opened 10 years ago
Closed 9 years ago
Last modified 5 years ago
#9678 closed task (fixed)
Rewrite interrupt handling
Description (last modified by )
There are lots of things to be improved in the interrupt handling routines in c_lib/src/interrupt.c and c_lib/include/interrupt.h.
Major changes planned:
- DONE: make
sig_on()have function syntax so that we can declare it
cdef int sig_on() except 0. See #10115 for the syntax changes.
- DONE: do not save signals in
sigsetjmp()(by giving a second argument of 0 instead of 1). This speeds up a sig_on/sig_off loop from 382 clock cycles to 30 clock cycles on a Core(TM)2 Duo CPU T5870 @ 2.00GHz running Linux 2.6.34 glibc 2.11.2.
- DONE: using
sigaction()instead of
signal()since that has more well-defined semantics.
- DONE: handle SIGINT differently from other signals (other signals are urgent and cannot be ignored. SIGINT on the other hand does not need to handled immediately, but we have to be careful for race conditions).
- DONE: allow
sig_on()and
sig_off()to be nested.
- DONE: implement
sig_retry()for retrying failed computations (this is useful for PARI, see #10018).
- DONE: have an interface for more general errors which are not signals. This can then be used by PARI, NTL and possibly other C libraries (various tickets).
- DONE: clean up old, unused code.
- DONE: testing interrupt handling: #10030.
- DONE: fix breakage because of this patch: #10061.
- DONE: documentation: #10109.
- DONE: Block interrupts during malloc: #10258.
- DONE: eliminate race condition when a SIGINT arrives before
sig_on()or during
sig_on().
Other potentially related tickets:
- #800 (make _sig_on and _sig_off faster when stacked)
- #9640 (Change PARI error catching mechanism)
- #9564 (libsingular exponentiation can not be interrupted)
- #7879 (Remove unnecessary signal handling for low prec mpfr operations) --- hopefully
sig_on()and
sig_off()can be made very fast such that this shouldn't be an issue anymore.
- #7794 (
PolynomialRing_integral_domainignores Ctrl-C and segfaults)
- #5313 (patch singular so that when it runs out of memory the error message says "singular" in it)
- #7702 (Handle interrupts better in the notebook)
- #3423 (Make Pari error messages more informative)
- #10126 (Fix error handing in Matrix_rational_dense._invert_pari())
- #10818 (EclLib? should allow signals to make LISP code interruptable)
Attachments (1)
Change History (47)
comment:1 Changed 10 years ago by
- Component changed from misc to c_lib
- Owner changed from jason to tba
comment:2 Changed 10 years ago by
- Cc leif added
comment:3 Changed 9 years ago by
comment:4 Changed
comment:18 Changed 9 years ago by
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comment:27 Changed 9 years ago by
comment:28 Changed 9 years ago by
- Milestone changed from sage-feature to sage-4.6.2
- Status changed from needs_work to needs_review
comment:29 Changed 9 years ago by
Changed 9 years ago by
comment:30 follow-up: ↓ 32 Changed 9 years ago by
- Status changed from needs_review to positive_review
Definite improvement! We should put it in the very next Sage-4.6.2.alpha to give it as much exposure as possible since it touches a couple of core C files.
comment:31 Changed 9 years ago by
- Reviewers set to Volker Braun
comment:32 in reply to: ↑ 30 Changed 9 years ago by
Definite improvement! We should put it in the very next Sage-4.6.2.alpha to give it as much exposure as possible since it touches a couple of core C files.
Alternatively, I am considering making 4.6.2 a pretty straightforward release and then putting various "big" tickets such as this one, #9433, #10572 in the next release which would then be sage-4.7.
comment:33 Changed 9 years ago by
- Milestone changed from sage-4.6.2 to sage-4.7
comment:34 Changed 9 years ago by
- Priority changed from major to blocker
comment:35 Changed 9 years ago by
I'm trying out Sage-4.6.2.rc0 in Fedora 14 i386 inside
VirtualBox, and it doesn't catch the SIGILL. Bactrace is below. Everything else works fine. Also, no such issue on my native Fedora 14 x86_64.
I'm not sure who is to blame here, could be something with the virtual machine. I did write a SIGILL handler in Perl and that works, so
VirtualBox is at least in principle able to have guests raise and handle SIGILL. Though there is also some forking involved...
The only thing thats special about SIGILL that comes to mind is that it might not be automatically be reset to SIG_DFL upon entrance. But I don't see how that could cause this. Here is my testcase:
[vbraun@localhost ~]$ sage -gdb ---------------------------------------------------------------------- | Sage Version 4.6.2.rc0, Release Date: 2011-02-18 | | Type notebook() for the GUI, and license() for information. | ---------------------------------------------------------------------- ********************************************************************** * * * Warning: this is a prerelease version, and it may be unstable. * * * ********************************************************************** /home/vbraun/Sage/sage/local/bin/sage-ipython GNU gdb (GDB) Fedora (7.2-41.fc14) /mnt/sage/vbraun/sage-4.6.2.rc0/local/bin/python...done. [Thread debugging using libthread_db enabled] Python 2.6.4 (r264:75706, Feb 19 2011, 16:56:24) [GCC 4.5.1 20100924 (Red Hat 4.5.1-4)] on linux2 Type "help", "copyright", "credits" or "license" for more information. Traceback (most recent call last): File "/usr/share/gdb/auto-load/usr/lib/libstdc++.so.6.0.14-gdb.py", line 59, in <module> from libstdcxx.v6.printers import register_libstdcxx_printers File "/usr/lib/../share/gcc-4.5.1/python/libstdcxx/v6/printers.py", line 19, in <module> import itertools ImportError: No module named itertools Detaching after fork from child process 10247.
So far, so good. Now run:
sage: import sage.tests.interrupt sage: sage.tests.interrupt.test_signal_ill() Detaching after fork from child process 10248. Program received signal SIGILL, Illegal instruction. 192 _signals.sig_on_count++; Missing separate debuginfos, use: debuginfo-install expat-2.0.1-10.fc13.i686 fontconfig-2.8.0-2.fc14.i686 glibc-2.13-1.i686 keyutils-libs-1.2-6.fc12.i686 krb5-libs-1.8.2-8.fc14.i686 libcom_err-1.41.12-6.fc14.i686 libgcc-4.5.1-4.fc14.i686 libgfortran-4.5.1-4.fc14.i686 libselinux-2.0.96-6.fc14.1.i686 libstdc++-4.5.1-4.fc14.i686 ncurses-libs-5.7-9.20100703.fc14.i686 nss-softokn-freebl-3.12.9-2.fc14.i686 openssl-1.0.0d-1.fc14.i686 (gdb) l 187 fprintf(stderr, "sig_on (counter = %i) at %s:%i\n", _signals.sig_on_count+1, file, line); 188 fflush(stderr); 189 #endif 190 if (_signals.sig_on_count > 0) 191 { 192 _signals.sig_on_count++; 193 return 1; 194 } 195 196 /* At this point, _signals.sig_on_count == 0 */ (gdb) bt #0 #1 __pyx_pf_4sage_5tests_9interrupt_test_signal_ill (__pyx_self=<value optimized out>, __pyx_args=0xb7fa702c, __pyx_kwds=0x0) at sage/tests/interrupt.c:2878 #2 0x0017c398 in PyCFunction_Call (func=0xaad686c, arg=0xb7fa702c, kw=0x0) at Objects/methodobject.c:85 #3 0x001de9dd in call_function (f=0x820c4d4, throwflag=0) at Python/ceval.c:3706 #4 PyEval_EvalFrameEx (f=0x820c4d4, throwflag=0) at Python/ceval.c:2389 #5 0x001e06e7 in PyEval_EvalCodeEx (co=0xaa5fd58, globals=0x83cf3e4, locals=0x83cf3e4, args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:2968 #6 0x001e0803 in PyEval_EvalCode (co=0xaa5fd58, globals=0x83cf3e4, locals=0x83cf3e4) at Python/ceval.c:522 #7 0x001deccb in exec_statement (f=0x81630ec, throwflag=0) at Python/ceval.c:4401 #8 PyEval_EvalFrameEx (f=0x81630ec, throwflag=0) at Python/ceval.c:1717 #9 0x001e06e7 in PyEval_EvalCodeEx (co=0x837aa88, globals=0x8370714, locals=0x0, args=0x8162c08, argcount=2, kws=0x8162c10, kwcount=0, defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:2968 #10 0x001dea92 in fast_function (f=0x8162abc, throwflag=0) at Python/ceval.c:3802
comment:36 Changed 9 years ago by
Volker, do you have
strace installed? If so, you could try
$ mkdir trace $ strace -ff -o trace/sage ./sage -c 'import sage.tests.interrupt; sage.tests.interrupt.test_signal_ill()'
and send me the
trace/ directory.
And maybe do the same for
test_signal_bus() to compare with.
comment:37 Changed 9 years ago by
Sure, no problem. I did strace ill, bus, and fpe and uploaded the trace/ directory to
comment:38 Changed 9 years ago by
Hold your horses! Its working now, and SIGILL is caught correctly. I did rebuild the sage library in the meantime, so I probably miscompiled something before.
comment:39 Changed 9 years ago by
In any case, based on your trace, it looks like everything is working correctly. I see the following:
--- SIGILL (Illegal instruction) @ 0 (0) --- rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0 write(2, "Traceback (most recent call last"..., 35) = 35 write(2, " File \"/home/vbraun/Sage/sage/l"..., 74) = 74
So, the program receives
SIGILL and prints a Traceback, which is exactly what should happen.
I cannot understand why at some point it did not work for you...
comment:40 follow-up: ↓ 41.
Since we don't use PPL's floating point arithmetics I'll make sure to configure it in a way that it does not test for SSE availability.
comment:41 in reply to: ↑ 40.
I consider this to be a bug in PPL. Using
sigaction() or
signal(), it is possible to save an existing signal handler and then restore it afterwards.
comment:42 Changed 9 years ago by
I agree and will report it upstream.
comment:43 Changed 9 years ago by
- Merged in set to sage-4.7.alpha1
- Resolution set to fixed
- Status changed from positive_review to closed
Author of what? ;-) | https://trac.sagemath.org/ticket/9678 | CC-MAIN-2020-16 | refinedweb | 1,624 | 58.28 |
pre-commit is a pre-commit hook installer for git. It will ensure that your npm test (or other specified scripts) passes before you can commit your changes. This all conveniently configured in your package.json. But don't worry, you can still force a commit by telling git to skip the pre-commit hooks by simply committing using --no-verify.git hooks npm pre-commit precommit run test development
Lambda-local lets you test Amazon Lambda functions on your local machine with sample event data. The context of the Lambda function is already loaded so you do not have to worry about it. You can pass any event JSON object as you please. You can use Lambda-local as a command line tool.amazon-lambda aws-sdk lambda nodejs amazon aws local run
JXA is JavaScript for Automation on macOS. Requires macOS 10.10 or later.Returns a Promise for the value returned from input.jxa osascript run mac execute code script automation
Plan a series of concrete steps and display their output in a beautiful way.Ever wanted to write a simple CLI that run a series of tasks with beautiful output? I did and I always ended up doing a thin wrapper repeatedly. This library provides a concise way to define these tasks while offering a handful of reporters to output the progress in a variety of ways.plan step steps phase phases cli task runner run
A test compiling WebVR (with A-Frame) to GearVR as a native application.Unlike a simple web page, which requires disabling GearVR service and setting up Chrome Dev, this approach intends to make a WebVR application that can be distributed through the Oculus Store.gearvr oculus run test webvr web vr
Since npm 2.0, you can pass arguments to scripts... wait... what if you could use that for creating CLIs? Homerun is a little experiment that lets you just do that. If you need more, I highly recommend minimist.And of course, while you develop, you can still use npm run add -- 1 2 to test your command.npm run package cli scripts
npm-path will get you a PATH with all of the executables available to npm scripts, without booting up all of npm(1).Calling npm-path from the commandline is the equivalent of executing an npm script with the body echo $PATH, but without all of the overhead of booting or depending on npm.npm run executable
Use npm-run to ensure you're using the same version of a package on the command-line and in package.json scripts.Any executable available to an npm lifecycle script is available to npm-run.nodejs npm npm-scripts command-line path executable .bin run
Use npm-which to locate executables which may be installed in the local 'node_modules/.bin', or in a parent 'node_modules/.bin' directory.npm-which runs in the context of an npm lifecycle script with its npm-modified PATH.npm path executable run
Run a command from every installed npm package under a certain scope. Useful in combination with district.Where <namespace> is the package namespace to use, and <command...> is a command to run from your shell in each scoped package.scoped package module npm tool cli batch bulk run command
We have large collection of open source products. Follow the tags from
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Add Projects. | https://www.findbestopensource.com/tagged/run | CC-MAIN-2020-45 | refinedweb | 584 | 65.93 |
").
Has anybody seen Larry Wall's new Slashdot interview that looks like it got posted today?
I always find Larry's interviews entertaining, this one is no exception.
No, I don't mean to use y instead of x, having an XY Problem. This is about a silly module - but a rather handy one.
I'm presenting just the POD of it. I'm not posting the entire module because... see the COPYRIGHT AND LICENSE block. WARNING: insane code ahead.
NAME
y - your own toolbox
SYNOPSIS
$ export PERL5LIB=$HOME/priv/lib
$ perl -My=mail,A,:date,frob -le '...'
Unimplemented at -e line 1.
[download]
$ export PERL5LIB=$HOME/priv/lib
$ perl -My=mail,A,:date,frob -le '...'
Unimplemented at -e line 1.
[download]
SEE ALSO
x
eow
umble
imimi
...
I18N
The german version of this module is named eins.pm. The spanish and italian versions are io.pm proper.
The german version of this module is named eins.pm. The spanish and italian versions are io.pm proper.
AUTHOR
You.
You.
This library is concealed software; you should not redistribute it and/or coerce
it on your coworkers under the same terms as Perl itself, neither Perl version 5.18.2 nor,
at your option, any later version of Perl 5 you may have available.
This library is concealed software; you should not redistribute it and/or coerce
it on your coworkers under the same terms as Perl itself, neither Perl version 5.18.2 nor,
at your option, any later version of Perl 5 you may have available.
=cut
Is that copyright ok for you? Did I miss any important wrongdoing? Nonwithstanding the distribution of the whole module being discouraged, it is ok to post snippets that fit nicely into y.pm, e.g.
my($m,$z);
$m=pack"B32",pop=~'/'x$';
printf"$` network %vd broadcast %vd netmask %vd\n",($z=eval$`)&$m,$z|~
+$m,$m
[download]
... not sure if it's too late to be still accepted
Emacs offers even more ways to do it than Perl's TIMTOWTDI ..
For starters: Overview of Emacs goodies (and some myth-busting)
open source
available on all development platforms
runs in windows and TTY
start-up time and memory consumption comparable to Vim ( != vi)
just try emacs -nw -Q
package management for a huge universe of extensions
CUA shortcut emulations for "modern" applications (C-x C-v C-z C-a
...)
VIM command emulation evil-mode (includes text objects)
regional undo Undo only in selected text.
Out-of-The-Box support
What comes already builtin for Perl?
** cperl-mode
The Standard mode for Perl features, including
imenu
easy navigation for subs
auto indentation
code transformation
prettifying regex convert postfix <-> prefix for "if" , "unless", etc
compile options
formatting options akin to perltidy
documentation display
** perldb
Perl debugger integration, stepping through original file
** flymake-mode
Interactive syntax check while typing by running "perl -c" in
background
** dabbrev-mode
avoid typos of identifiers by expanding from dynamic abbreviation
dictionary
Recommended Extension Packages
**.
Visions
**.
What comes already builtin for Perl?
** cperl-mode
The Standard mode for Perl features, including
Perl debugger integration, stepping through original file
** flymake-mode
Interactive syntax check while typing by running "perl -c" in
background
** dabbrev-mode
avoid typos of identifiers by expanding from dynamic abbreviation
dictionary
**.
Cheers Rolf
(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!
I'm on Windows 7 with a perl 5.24 install in C:/strawberry
I lost so many hours trying to understand why dmake always failed with undefined reference, that I thougt usefull to give a recipe to others when I finaly found a workaround. Here it goes:
From the cpan shell, the command looks perl_module is another way to open a subshell in the corresponding build/module_folder
Repeat this change for the files:
gobject-2.0.pc
pango.pc
gtk+-2.0.pc
[download]
perl Makefile.pl INC="-IC:/strawberry/c/include/freetype2 -IC:/prog/gt
+k+/include/cairo -IC:/prog/gtk+/include/ -I. -I.\build"
[download]
dmake
dmake test
dmake install
[download]
perl Makefile.pl INC="-IC:\prog\gtk+\include\glib-2.0 -IC:\prog\Gtk+\l
+ib\glib-2.0\include -I. -I./build"
dmake
dmake test
dmake install
[download]
perl Makefile.pl INC="-IC:\prog\gtk+\include -IC:/prog/gtk+/include/f
+reetype2 -IC:/prog/Gtk+/include/cairo -IC:\prog\Gtk+\include\Pango-1.
+0 -IC:\prog\Gtk+\include\glib-2.0 -IC:\prog\Gtk+\lib\glib-2.0\include
+ -I. -I./build -IC:\strawberry\perl\site\lib\Glib\Install -IC:\strawb
+erry\perl\site\lib\Cairo\Install"
dmake
dmake test
dmake install
[download]
perl Makefile.pl INC="-IC:\strawberry\perl\site\lib\Glib\Install -IC:\
+strawberry\perl\site\lib\Pango\Install -IC:\strawberry\perl\site\lib\
+Cairo\Install -IC:\prog\gtk+\include -IC:\prog\Gtk+\include\glib-2.0
+-IC:\prog\gtk+\include\pango-1.0 -IC:\prog\Gtk+\include\cairo -IC:\pr
+og\Gtk+\include\atk-1.0 -IC:\prog\gtk+\include\gdk-pixbuf-2.0 -IC:\pr
+og\gtk+\include\gtk-2.0 -IC:\prog\gtk+\include\freetype2 -IC:\prog\Gt
+k+\lib\glib-2.0\include -IC:\prog\Gtk+\lib\gtk-2.0\include -I. -I./bu
+ild"
dmake
dmake test
dmake install
[download]
Notes:
The command given above for perl Makefile.PL has been used for the gtk+-bundle_2.24.10
A newer version could contains new libraries and this would cause dmake to fail with filex.h not found
In that case, you have to add the path to the missing file with -Ic:/this/is/where/thatmissing/file/is in the INC arg given to Makefile.PL.
Perl modules already installed have this header file in
And external libraries to uninstalled perl modules have their header files somewhere in
C:\prog\gtk+\include
C:\prog\Gtk+\include\xxx
C:\prog\Gtk+\lib\xxx\include
[download]
perl Makefile.PL INC="changed to include the new path"
dmake
[download]
until dmake gives no error.
Now if you change the path where your gtk+ libraries have been unzipped (or if you remove C:/prog/gtk+/bin from your PATH environment variable, your perl scripts using Gtk2 will crash.
To gain independance from C:/prog/gtk+/bin, you need to copy some dll from this folder to your perl tree directory. This small script does this (the dll list hold for gtk+-bundle_2.24.10):
use strict;
use warnings;
use File::Copy;
my $from= "C:/prog/gtk+/bin/";
my %fm=('C:/strawberry/perl/site/lib/auto/Glib/' => [qw(
libglib-2.0-0.dll
intl.dll
libgthread-2.0-0.dll
libgobject-2.0-0.dll
)],
'C:/strawberry/perl/site/lib/auto/Cairo/' => [ qw(
libcairo-2.dll
libexpat-1.dll
freetype6.dll
libpng14-14.dll
libfontconfig-1.dll
zlib1.dll
)],
'C:/strawberry/perl/site/lib/auto/Pango/' => [qw(
libgmodule-2.0-0.dll
libpango-1.0-0.dll
libpangocairo-1.0-0.dll
libpangoft2-1.0-0.dll
libpangowin32-1.0-0.dll
)],
'C:/strawberry/perl/site/lib/auto/Gtk2/' => [ qw(
libgtk-win32-2.0-0.dll
libgio-2.0-0.dll
libgdk_pixbuf-2.0-0.dll
libatk-1.0-0.dll
libgdk-win32-2.0-0.dll
)]);
foreach my $dest (keys %fm){
my $files = $fm{$dest};
foreach my $file (@$files){
print "will copy $from$file to $dest/$file\n";
copy("$from$file", "$dest/$file") or die("failed... : $!");
}
}
[download]
HTH !
frazap
Dear Monks
I thought I share this small Perl program demonstrating the possibility to do PWM (Pulse Wide Modulation) on Raspberry Pi in order to control the intensity of a led. This is a common introduction example to try for people learning about electronics on Raspberry Pi. Well documented examples for python exists, but not for Perl.
The reason I share this here, is that the current CPAN module Device::BCM2835 doesn't define the necessary function to do this (that I see). So it took me some tinkering before I could control the PWM from Perl. Novice users of Perl may find this example code the thing they need.
The solution I apply is the use of the Inline::C module to call some small wrapper functions I wrote in C around an existing C example I found on the internet. They call in turn the bcm2835 functions needed. This is tested on a raspberry pi B, revision 2 unit, using a single led and a single resistor.
This code assumes you have installed the Inline::C module, Time::HiRes module, and the bcm2835 C library on your device. See Device::BCM2835 module for the appropriate links to the C library. It is not installed by default. Run as root on Raspberry Pi because you need to have access to some low level functions.
Today I'm not proficient in XSLoader to update the Device::BCM2835 module itself, but if I have some spare time, I will look into it. Would be a nice additional skill to master.
Any thoughts or comments appreciated.
Martell
My work currently involves doing ETL (data-munging) using Perl. Because some of the data may have private information (PII), I'm doing my work on a remote desktop, which at this organization is Azure (Windows). It's not really my choice of platform -- but at least I'm able to use the excellent git-bash package to get (more or less) back to a Linux type command line.
The issue I'm having is that transferring files from my volume to the volume where my output is carried on to the next step is unreliable, and I'm wondering if anyone else has come across the same challenge. I also want to check the existing files, as I append a version number to the end of my files so that new files don't overwrite existing files.
The solution I've finally hit on (this is my work in progress) is to use chdir to go into the directory in question, and then glob to get a list of the files. It still takes ten seconds to get a list of files, but I guess that's the best I can do right now.
Thoughts, comments, ideas are welcome. Thanks!
Alex / talexb / Toronto
Thanks PJ. We owe you so much. Groklaw -- RIP -- 2003 to 2013.
Hello everyone,
A recent thread reminded me of a script I wrote years ago while learning about the flip-flop operator (aka the range operator in scalar context), and I thought I'd share it in case it helps someone else.
The script, which I've included below the output, runs through a sequence of true/false values, tests whether the right-hand-side and/or left-hand-side of the operator is evaluated (marked by an asterisk in the table), gets the return value of the operator, and outputs all that in the following handy table. I hope it illustrates the difference between the .. (two-dot) and ... (three-dot) versions of the operator: two dots will immediately evaluate the RHS if the LHS is true, three dots will wait until the next evaluation.
*** Demonstration of the Flip-Flop Operators ***
__A______B____X___ __A______B____X___
0* .. 0 = 0* ... 0 =
0* .. 1 = 0* ... 1 =
0* .. 0 = 0* ... 0 =
1* .. 0* = 1 1* ... 0 = 1
0 .. 0* = 2 0 ... 0* = 2
0 .. 0* = 3 0 ... 0* = 3
0 .. 1* = 4E0 0 ... 1* = 4E0
0* .. 0 = 0* ... 0 =
0* .. 0 = 0* ... 0 =
1* .. 1* = 1E0 1* ... 1 = 1
0* .. 0 = 0 ... 0* = 2
0* .. 0 = 0 ... 0* = 3
1* .. 0* = 1 1 ... 0* = 4
0 .. 0* = 2 0 ... 0* = 5
0 .. 1* = 3E0 0 ... 1* = 6E0
0* .. 1 = 0* ... 1 =
1* .. 1* = 1E0 1* ... 1 = 1
1* .. 0* = 1 1 ... 0* = 2
0 .. 0* = 2 0 ... 0* = 3
0 .. 1* = 3E0 0 ... 1* = 4E0
0* .. 0 = 0* ... 0 =
1* .. 1* = 1E0 1* ... 1 = 1
1* .. 1* = 1E0 1 ... 1* = 2E0
1* .. 1* = 1E0 1* ... 1 = 1
0* .. 0 = 0 ... 0* = 2
0* .. 1 = 0 ... 1* = 3E0
0* .. 0 = 0* ... 0 =
(* = Evaluated)
[download]
Regards,-- Hauke D
Back in 2005 I asked why the execution order of subexpression was undefined (in Perl; but it's inherited from C); and over a long and twisted thread I was shouted down by all-comers, accused of smoking waccy baccy etc. I don't think there was a single person that agreed with me that EO should be defined.
12 years later and the C++ Evolution Working Group have finally caught up, and C++17 will probably get a defined order of subexpression evaluation.(pdf)
Perl 6 could have stolen the march. Just sayin'.
In the 5 days since The significance of 2010-03-16? one hundred and seventy five of you have chosen to down vote one of my posts, (or 25 of you 7 of them; or ... ), for a total of -175(*) downvotes.
(*Within the limitations of what the site architect permits me to discover.)
The affect of that collective, heartfelt ire towards me, (or perhaps the subject matter), is that my XP has gone from 161809 on that day to 161936 this morning: +127.
So, if the rating system is perfect; thank you all. And if its not; thank you anyway!
Tipping anyway.
Most failures were caused by the new hash randomisation (see Hash order randomization is coming, are you ready?). As we use Test::Spec, most failures can be solved easily by turning an array reference into a bag:
# Old:
cmp_deeply($obj->method, [ $result1, $result2 ]);
# New:
cmp_deeply($obj->method, bag($result1, $result2));
[download]
We use Moose in most of the code, which makes mocking a bit harder because of type constraints. Imagine you have the following code you need to test:
use warnings;
use strict;
{ package Person;
use Moose;
use namespace::autoclean;
has name => ( is => 'rw',
isa => 'Str',
required => 1,
);
has id => ( is => 'ro',
isa => 'Str',
required => 1,
);
__PACKAGE__->meta->make_immutable;
}
{ package Position;
use Moose;
use namespace::autoclean;
has person => ( is => 'rw',
isa => 'Person',
);
has title => ( is => 'ro',
isa => 'Str',
);
__PACKAGE__->meta->make_immutable;
}
[download]
When testing the Position, we don't care about the details of the Person. We only want to stub an object with the needed methods implemented, which can even be none:
use Test::Spec;
describe 'position' => sub {
it 'instantiates' => sub {
my $person = stub();
my $position = 'Position'->new(person => $person);
isa_ok($position, 'Position');
cmp_deeply([ $position->person ], bag($person));
};
};
[download]
(The last line doesn't make much sense in this context, but imagine more complex objects. We need to use the bag function somewhere to show the problem.)
This would work under plain OO, but it doesn't for us; Moose complains:
Attribute (person) does not pass the type constraint because: Validati
+on failed for 'Person' with value Test::Spec::Mocks::MockObject={ }
[download]
The common trick to solve this, appearing all over the code base, has been to stub the isa method of the object to always return 1. Moose's got happy when checking the object type, and no one else has cared:
my $person = stub( isa => 1 );
[download]
But alas, this trick doesn't work in the newer Test::Deep. Here's the failure message:
Found a special comparison in $data
You can only use specials in the expects structure at /home/choroba/pe
+rl5/lib/perl5/Test/Deep.pm line 346.
[download]
Pretty informative, don't you think? It took me several hours to find the exact reason; the indicated line was changed in May 2011 in the following way:
# Old:
if (! $Expects and ref($d1) and UNIVERSAL::isa($d1, "Test::Deep::Cmp")
+)
# New:
if (! $Expects and Scalar::Util::blessed($d1) and $d1->isa("Test::Deep
+::Cmp"))
[download]
So, returning 1 from the isa method now makes Test::Deep believe the stubbed object is its special construct that shouldn't appear on the left hand side of the comparison.
To verify that's actually the problem, I tried to modify the isa in a more sophisticated way:
my $person = stub( isa => sub { $_[1] !~ /Test/ } );
[download]
and yes, it started to work again. Moose asks for Person , so isa returns 1, the testing framework asks for Test::Deep::Cmp and therefore gets 0.
But it's an ugly hack. Some other modules might get confused by such a mocking, as they might check for other classes not containing Test , or, worse, we also have several classes whose namespace contains Test somewhere.
So, I created a helper function
sub mock_isa { my ($class) = @_; isa => sub { $_[1] eq $class } }
[download]
which can be used as
my $person = stub(mock_isa('Person'));
[download]
Not as short as the original trick, but still easier than reimplementing the whole inheritance logic. What tricks do you use?
($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,
[download]
Hi all,
I'm sure we've all wished for a concatenation operator that would prepend a string to a string in the same way the .= operator appends.
So why isn't there one?
It's silly that you can write:
$foo .= 'bar';
[download]
$baz =. 'qux';
[download]
$baz = 'qux' . $baz;
[download]
Today I got to wondering if I had missed that such an operator had been introduced in some recent Perl version so I ran the code, and to my surprise Perl said:
Reversed .= operator at -e line 5.
syntax error at -e line 5, near "=."
[download]
Can any guts gurus shed any light?
. | http://www.perlmonks.org/?showspoiler=993848-9;node_id=480 | CC-MAIN-2016-30 | refinedweb | 2,896 | 65.32 |
Now that we’ve looked at a bunch of myths about when finalizers are required to run, let’s consider when they are required to not run:
Myth: Keeping a reference to an object in a variable prevents the finalizer from running while the variable is alive; a local variable is always alive at least until control leaves the block in which the local was declared.
{ Foo foo = new Foo(); Blah(foo); // Last read of foo Bar(); // We require that foo not be finalized before Bar(); // Since foo is in scope until the end of the block, // it will not be finalized until this point, right? }
The C# specification states that the runtime is permitted broad latitude to detect when storage containing a reference is never going to be accessed again, and to stop treating that storage as a root of the garbage collector. For example, suppose we have a local variable
foo and a reference is written into it at the top of the block. If the jitter knows that a particular read is the last read of that variable, the variable can legally be removed from the set of GC roots immediately; it doesn’t have to wait until control leaves the scope of the variable. If that variable contained the last reference then the GC can detect that the object is unreachable and put it on the finalizer queue immediately. Use
GC.KeepAlive to avoid this.
Why does the jitter have this latitude? Suppose the local variable is enregistered into the register needed to pass the value to
Blah(). If
foo is in a register that
Bar() needs to use, there’s no point in saving the value of the never-to-be-read-again
foo on the stack before
Bar() is called. (If the actual details of the code generated by the jitter is of interest to you, see Raymond Chen’s deeper analysis of this issue.)
Extra bonus fun: the runtime uses less aggressive code generation and less aggressive garbage collection when running the program in the debugger, because it is a bad debugging experience to have objects that you are debugging suddenly disappear even though the variable referring to the object is in scope. That means that if you have a bug where an object is being finalized too early, you probably cannot reproduce that bug in the debugger!
See the last point in this article for an even more horrid version of this problem.
Myth: Finalizers run no more than once.
Suppose you have an object that is in the process of being finalized and is therefore no longer a candidate for finalization, or you have suppressed finalization. The aptly-named
ReRegisterForFinalize method tells the runtime that you would like the object to be finalized. This can cause an object to be finalized more than once.
Why on earth would you want to do that? The most common usage case is that you have a pool of objects that are very expensive for some reason. Perhaps they are producing collection pressure if they are allocated too often, or perhaps they are for some reason expensive to allocate but cheap to re-use. In this case you can have a “pool” of living objects. When you need an object, you remove it from the pool. When you’re done with the object, you put it back in the pool. What if you forget to put the object back in the pool? (This is analogous to forgetting to dispose of an object that has an unmanaged resource.) In that case, the finalizer can put the object being finalized back in the pool, so it is no longer dead. Of course the object now needs to be finalized again, should the user take it out of the pool and again forget to finalize it.
I do not recommend resurrecting dead objects unless you really know what you are doing and you have a clearly unacceptable performance problem that this technique solves. In the case of Roslyn we identified very early on that the compiler allocates a gazillion small objects, some of them very short-lived and reusable, and that we had a performance problem directly attributable to excess collection pressure. We used a pooling strategy for the cases where our performance tests indicated that it would be a win.
Myth: An object being finalized is a dead object.
The GC must identify an object as dead — no living references — in order to place it on the finalizer queue, but the finalizer queue is itself a living object, so objects on the finalizer queue are technically alive as far as the GC is concerned. Which is good; if the GC runs for a second time while the objects identified the previous time are still on the finalization queue, they should not be reclaimed, and they certainly should not be placed on the finalization queue again!
Myth: An object being finalized is guaranteed to be unreachable from code outside the finalization queue.
There could be two objects both determined by the GC to be dead, both with references to each other. When one is finalized, it decides to keep itself alive an copies its “this” to a static field, which is clearly reachable by user code. Since the now-reachable object has a reference to another object, that object is also reachable, so user code could be running in it while it is being finalized.
Again, I strongly recommend against resurrecting dead objects unless you really know what you are doing and have a truly excellent reason for doing this crazy thing.
Myth: Finalizers run on the thread that created the object.
The finalizer typically runs on its own thread. If you have an object that is in some way has affinity to a particular thread — perhaps it uses thread local storage, or perhaps it is an apartment threaded object — then you must do whatever threading magic is necessary to use the object safely from the finalizer thread, preferably without blocking the finalizer thread indefinitely.
Myth: Finalizers run on the garbage collector thread.
The finalizer and the garbage collector typically have their own threads. This is not a requirement of all versions of the CLR, but it is the typical case.
Myth: Finalizers run as the garbage collector determines that objects are dead.
As we’ve discussed, the GC determines that the object is dead and needs finalization, and puts it on the finalizer queue. The GC then keeps on doing what it does best: looking for dead objects.
Myth: Finalizers never deadlock
We can certainly force a finalizer to deadlock, illustrating that the myth is false:
class Deadlock { ~Deadlock() { System.Threading.Monitor.Enter(this); } static void Main() { Deadlock d = new Deadlock(); System.Threading.Monitor.Enter(d); d = null; System.GC.Collect(); System.GC.WaitForPendingFinalizers(); } }
This is obviously unrealistic, but realistic deadlocks are in particular possible in scenarios like I mentioned above: where a call must be marshalled to the correct thread for an object that has some sort of thread affinity. Here’s a link to a typical example. (Note that the article leads with “finalizers are dangerous and you should avoid them at all costs”. This is good advice.)
Myth: Finalizers run in a predictable order
Suppose we have a tree of objects, all finalizable, and all on the finalizer queue. There is no requirement whatsoever that the tree be finalized from the root to the leaves, from the leaves to the root, or any other order.
Myth: An object being finalized can safely access another object.
This myth follows directly from the previous. If you have a tree of objects and you are finalizing the root, then the children are still alive — because the root is alive, because it is on the finalization queue, and so the children have a living reference — but the children may have already been finalized, and are in no particularly good state to have their methods or data accessed.
Myth: Running a finalizer frees the memory associated with the object.
The finalizer thread runs the finalizers, the GC thread identifies dead objects that do not need finalization, and reclaims their memory. The finalizer thread does not try to do the GC’s job for it.
Myth: An object being finalized was fully constructed.
I’ve saved the worst for last. This is in my opinion the truly nastiest of all the issues with finalizers. I’ll give you two scenarios, both horrible.
sealed class Nasty : IDisposable { IntPtr foo; IntPtr bar; public Nasty() { foo = AllocateFoo(); // Suppose a thread abort exception is thrown right here. bar = AllocateBar(); } ~Nasty() { Dispose(false); } public void Dispose() { Dispose(true); } private void Dispose(bool disposing) { DeallocateFoo(foo); DeallocateBar(bar); } }
In C++, destructors don’t run if a constructor throws, but in C# an object becomes eligible for finalization the moment that it is created. If a thread abort exception is thrown after
foo is initialized then
bar is still zero when the finalizer runs, and zero might not be a valid input to
DeallocateBar.
Now let’s combine that with the first point in today’s episode: that a finalizer can run earlier than you think.
sealed class Horrid : IDisposable { IntPtr foo; public Horrid() { foo = AllocateFoo(); Bar.Blah(); // static method } ~Horrid() { Dispose(false); } public void Dispose() { Dispose(true); } private void Dispose(bool disposing) {
OK, what are the possible scenarios at this point? Plainly a thread abort exception could have been thrown before, during or after the execution of
Blah(), so we cannot rely on any invariant set up by
Blah() in the finalizer. But we can at least rely on the fact that there are only three possibilities:
Blah() was never run,
Blah() threw, or
Blah() completed normally, right?
No; there is a fourth possibility:
Blah() is still running on the user thread, the GC has identified that the
this is never read, so the object is a candidate for finalization, and therefore it is possible that the finalizer and constructor are running concurrently. (Why you would create an object and then never read the reference I do not know, but people do strange things.)
And finally, I described an even more horrid version of this scenario in a previous blog entry.
Read the title of this article again: everything you know is wrong. In a finalizer you have no guarantee that anything happened other than the object was allocated, and that the GC at one time believed it to be dead. You have no guarantee that any invariant set up by the constructor is valid, and the constructor (or any other method of the object) could still be running when the finalizer is called, provided that the runtime knows that local copies of the reference will never be read again.
It is therefore very difficult indeed to write a correct finalizer, and the best advice I can give you is to not try.
Next time on FAIC: A far-too-detailed analysis of a copy-paste bug. But not in code this time!
Before there was SafeHandle, the bug you described in the last blog post and mention here was relatively common.
People would have a handle to some win32 resource as a member variable, and finalizer would dealocate/free it. They would ‘read’ that handle and pass it to some unmanaged api.
Meanwhile handle would get dealocated.
First time I debugged this was painful. From then on, when I hear about sporadic win32 failures and knew exactly what to look for 🙂
“In C++, destructors don’t run if a constructor throws”
I fear that this may confuse some people (it certainly confused me until I realised what you meant). As far as I know, destructors for all fully constructed objects (temporaries within the constructor body before an exception is thrown, or within the initialiser list, or implicitly initialised members); but any destructor corresponding to a constructor on the unwinding stack won’t be called.
“We used a pooling strategy”
So, I get the reasoning behind using a pooling strategy. I also (sort of) get the motivation behind trying to write a finalizer-based pooling strategy as a sort of backstop for one’s pooling strategy.
Are you saying that in Roslyn, that was actually the decision made? I.e. for some reason, it was deemed justified to backstop your pooling strategy with a finalizer-based implementation?
If so, could you please clarify on why this made sense for Roslyn, even as this is clearly a bad idea in most other scenarios?
It looks like your Horrid example is incomplete…
A myth related to the idea of finalizers running on the GC thread: when using stop-the-world GC, finalizers run while most of the world is stopped. Until I found out how the finalizer queues work, I thought finalizers were called directly from the GC (in which case it would make sense to have severe limits on finalizers’ ability to access any kind of outside objects).
As for the idea that finalized objects are unreachable from outside the freachable queue, it’s possible given any object reference to construct a long weak reference to it which will remain valid as long as the target still exists in any form and a strong rooted reference exists to the long weak reference. If a long weak reference exists to an object but no other strong rooted reference exists, then such an object may get queued for finalization at any time, and strong rooted references may be formed at any time. Consequently, a finalizable object that never makes use of resurrection will generally have no way to guard against the possibility of outside code manipulating references to it so as to cause its finalizer to run while the strongly-rooted references to the object are being used by outside code.
“It is therefore very difficult indeed to write a correct finalizer, and the best advice I can give you is to not try.”. This sentence near the end of your post has me confused. How do I reconcile it with the advice to have a finalizer (destructor) when I’m using unmanaged resources? For example this sentence from ():
“However, when your application encapsulates unmanaged resources such as windows, files, and network connections, you should use destructors to free those resources. When the object is eligible for destruction, the garbage collector runs the Finalize method of the object.”
would seem to indicate I should have a finalizer, at least when I have unmanaged resources? Are you suggesting a different pattern for cleaning up unmanaged resources, and if so, what? Or, does one need a finalizer (destructor) if using unmanaged resources?
Thanks,
Dave
I remember first reading about finalizers in the Java documentation, back in the mid 1990’s, and being confused and re-reading the whole section about five times. They’re both complex and counterintuitive, which is not a great combination.
Over the years, I’ve written hundreds of thousands (millions?) of lines of code, in many languages, and never had any need to write a finalizer. Or maybe I would have, if I’d been smarter, but it seems weird to write a method which is super easy to screw up, virtually impossible to test, and may never run at all.
I’d love to hear the flip side of all this: why on earth would anyone ever legitimately want to write a finalizer?
I think this whole article series could be condensed without losing meaning:
“Myth: adding finalizers to the C# language was a good idea
Clearly not.”
The .NET framework borrowed the `Finalize` concept from Java; later versions of Java added a concept calls “phantom reference” which, as implemented in Java is a bit clunky, but encapsulates the idea that resource cleanup should not be handled by the object holding the resources, but rather by another object which the first creates to watch over it, and which should avoid holding any strong references to anything not needed for cleanup.
Under such a design, cyclic reference chains between cleanup objects and the objects that they’re guarding can prevent such objects from ever becoming eligible for cleanup or collection, and even non-cyclic chains will increase the number of GC cycles required for cleanup and collection. On the flip side, however, such a design would eliminate many complications associated with intentional or unintentional resurrection, since the cleanup code wouldn’t run until after the guarded object was well and truly dead.
There are a few things which finalizers can do semantically which a design using separate cleanup objects could not (finalizable objects may hold references to each other and even use such references in their cleanup, though there is no guarantee of the order in which finalizers will run). I don’t know how often such abilities can be used to accomplish anything that couldn’t be done as practically without them.
is there actually any compelling reason to use a finalizer (except within the Disposable pattern, and even that is questionable, if it is disposable it should have been disposed in the first place) ever?
Stefan
There are some types that use resources which are plentiful and fungible but not unlimited, and whose consumers will often be abandoned outside their control. A prime example of such a type is “WeakReference”, which encapsulates a GCHandle. When a WeakReference is abandoned, the handle must be freed; there are a variety of object-abandonment-notification approaches a framework could provide which would allow the handles to be cleaned up when objects holding weak references get abandoned, but I think `Finalize` is the only one .NET provides that would really work well.
Well, in Java, WeakReference does not encapsulate a special handle and thus, does not need such special action. It would be a true nightmare if that class that should be an alternative to finalization (for some use cases) would be subject of all these problems associated with finalization. If a WeakReference is abandoned in Java, it gets collected like and other ordinary object and no special action will be taken.
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Just a note, I managed to reproduce the behavior of running the finalizer before the ctor completes (and this wasn’t that hard), but this does not happen if, at the last line of the ctor, the is a reference to “this”, like “this._handle = handle” or even “this.ToString()”, so, this myth isn’t all that bad.
The last one literally blew me away. You truly saved the worst for last!
Regarding aggressive GC of local vars before they’re out of scope – this can also occur with respect to the “this” reference. An object instance can be collected while an instance method is still running, as long as the method is past the point that no instance data is required (i.e. the “this” reference is no longer required). As an example, consider this code:
1. public class Looper
2. {
3. private readonly int _numLoops;
5.
6. public Looper(int numLoops)
7. {
8. _numLoops = numLoops;
9. }
10.
11. public void Go()
12. {
13. int numLoops = _numLoops;
14. for (int i = 0; i < numLoops; i++)
15. {
16. Console.Out.WriteLine("Loop #" + i);
17. }
18. }
19. }
20.
21. class Program
22. {
23. static void Main()
24. {
25. var looper = new Looper(1000000);
26. looper.Go();
27. }
28. }
What is the earliest point (i.e. line number during program execution) at which the instance "looper" in the Main() function could be collected by the garbage collector? The answer is line 14, while it's still executing the Go() method. No instance data is required after that point. You can see this by adding a finalizer that outputs a message. When you run, sometimes you'll see that message before the looping is finished (must be a release build).
Another good reason for the collection of local vars before they are out of scope is that this can help in some situations under memory pressure. For example, I could write a method that has this:
var a = new double[HUGE_SIZE];
var b = new double[HUGE_SIZE];
var c = new double[HUGE_SIZE];
…
This could continue indefinitely. With aggressive GC, you'll never run out of memory even though all the variables are always in scope. If they're not referenced after instantiation, they can be collected.
C++ has none of this complexity. If only C# had RAII !
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Excellent series, thank you Eric for these blogs.
If there were 2 things I would add to C#, they would be as such:
A#1) Multiple Inheritance.
2) Make C# construction/destruction have an option to 100% behave like C++.
The above said, I do have a solution for anyone needing 100% control over C# construction/destruction, and that is, run a separate process, it is the only way. Even AppDomain’s “Unload”, to unload a DLL and supposedly free all resources used by the DLL does not truly work.
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Overview
I recently delivered an introductory talk about Scala at an internal geek’s event at SAP. In this talk, I used an example complex numbers class to illustrate important language concepts and features. In many respects, this is a classical example that can be found in many other introductory materials about Scala, for example in this Scala Tutorial for Java Programmers. Nevertheless, I thought it’s a wonderful example worthy of another try. During the talk, I started with a very simple one-liner and gradually added more capabilities to it, while at the same time introducing the language features that made them possible. I ended up with a more or less complete and usable complex numbers implementation in just a few lines of code, which nevertheless allowed things that
would not be possible with other languages (Java), such as operator arithmetics, seamless conversion between complex and real numbers, and “free” equality and comparison.
In this post, I would like to reproduce this part of my talk. If you are interested in Scala, but haven’t mastered the language yet, this can be a good introduction to the conciseness and power of this remarkable programming language.
Starting Point
Our starting point is quite simple:
class Complex(val re: Double, val im: Double)
The single line above is the entire class definition. It has two
Double fields, which are public (as this is the default in Scala) and immutable (due to the
val keyword). The above line also defines implicitly a default two-argument constructor, so that
Complex instances can already be created and initialised. Let’s do this in the Scala interpreter:
scala> val x = new Complex(1, 2) x: Complex = [email protected]
If you compare this class definition to the code that would be needed to achieve the same in Java, it becomes evident that Scala is much more concise and elegant here, letting you express your intent clearly in the fewest possible lines of code.
Overriding Methods
The default string representation of
Complex above is rather unfriendly. It would have been much better if it contained the class members in a format suitable for a complex number. To achieve this, we will of course override the
toString method which our class inherits from
Any, the root of the Scala class hierarchy.
class Complex(val re: Double, val im: Double) { override def toString = re + (if (im < 0) "-" + -im else "+" + im) + "*i" }
Note that the
override keyword is mandatory in Scala. It has to be used when you override something, otherwise you get a complier error. This is one of the many ways Scala helps you as a programmer to avoid silly mistakes, in this case accidental overrides. Now, if you create a
Complex instance in the interpreter, you will get:
scala> val x = new Complex(1, 2) x: Complex = 1.0+2.0*i
Adding Methods and Operators
Since complex numbers are numbers, one thing we would like to be able to do with them are arithmetic operations such as addition. One way to achieve this would be to define a new
add method:
class Complex(val re: Double, val im: Double) { def add(c: Complex) = new Complex(re + c.re, im + c.im) ... }
With the above definition, we can add complex numbers by invoking our new method using the familiar notation:
scala> val x = new Complex(1, 2) x: Complex = 1.0+2.0*i scala> val y = new Complex(3, 4) y: Complex = 3.0+4.0*i scala> x.add(y) res0: Complex = 4.0+6.0*i
In Scala, we could also invoke our method, as well as in fact any method, using an operator notation, with the same result:
scala> x add y res1: Complex = 4.0+6.0*i
And since we have operator notation, we could as well call our method
+, and not
add. Yes, this is possible in Scala.
class Complex(val re: Double, val im: Double) { def +(c: Complex) = new Complex(re + c.re, im + c.im) ... }
Now, adding x and y can be expressed simply as:
scala> x + y res2: Complex = 4.0+6.0*i
If you are familiar with languages like C++, this may seem a lot like operator overloading. But in fact, it is not really correct to say that Scala has operator overloading. Instead, Scala doesn’t really have operators at all. Every operator-looking construct, including arithmetic operations on simple types, is in fact a method call. This is of course much more consistent and easier to use than traditional operator overloading, which treats operators as a special case. In the final version of our
Complex class, we will add the operator methods -, *, and / for the other arithmetic operations.
Overloading Constructors and Methods
Complex numbers with a zero imaginary part are in fact real numbers, and so real numbers can be seen simply as a special type of complex numbers. Therefore it should be possible to seamlessly convert between these two kinds of numbers and mix them in arithmetic expressions. To achieve this in our example class, we will overload the existing constructor and
+ method so that they accept
Double instead of
Complex:
class Complex(val re: Double, val im: Double) { def this(re: Double) = this(re, 0) ... def +(d: Double) = new Complex(re + d, im) ... }
Now, we can create
Complex instances by specifying just their real parts, and add real numbers to them:
scala> val y = new Complex(2) y: Complex = 2.0+0.0*i scala> y + 2 res3: Complex = 4.0+0.0*i
Constructor and method overloading in Scala is similar to what can be found in Java and other languages. Constructor overloading is somewhat more restrictive, however. To ensure consistency and help avoid common errors, every overloaded constructor has to call the default constructor in its first statement, and only the default constructor is allowed to call a superclass constructor.
Implicit Conversions
If instead of
y + 2 above we execute
2 + y we will get an error, since none of the Scala simple types has a method
+ accepting
Complex as an argument. To improve the situation, we can define an implicit conversion from
Double to
Complex:
implicit def fromDouble(d: Double) = new Complex(d)
With this conversion in place, adding a
Complex instance to a double becomes possible:
scala> 2 + y res3: Complex = 4.0+0.0*i
Implicit conversions are a powerful mechanism to make incompatible types interoperate seamlessly with each other. It almost renders other similar features such as method overloading obsolete. In fact, with the above conversion, we don’t need to overload the
+ method anymore. There are indeed strong reasons to prefer implicit conversions to method overloading, as explained in Why Method Overloading Sucks in Scala. In the final version of our
Complex class, we will add implicit conversions from the other simple types as well.
Access Modifiers
As a true object-oriented language, Scala offers powerful access control features which can help you ensure proper encapsulation. Among them are the familiar
private and
protected access modifiers which you can use on fields and methods to restrict their visibility. In our
Complex class, we could use a private field to hold the absolute value, or modulus of a complex number:
class Complex(val re: Double, val im: Double) { private val modulus = sqrt(pow(re, 2) + pow(im, 2)) ... }
Trying to access
modulus from the outside will of course result in an error.
Unary Operators
To allow clients to get the modulus of a
Complex instance, we will add a new method that returns it. Since modulus is a very common operation, it would be nice to be able to invoke it again as an operator. However, this has to be a unary operator this time. Fortunately, Scala helpfully allows us to define this kind of operators as well:
class Complex(val re: Double, val im: Double) { private val modulus = sqrt(pow(re, 2) + pow(im, 2)) ... def unary_! = modulus ... }
Methods starting with
unary_ can be invoked as unary operators:
scala> val y = new Complex(3, 4) y: Complex = 3.0+4.0*i scala> !y res2: Double = 5.0
In the final version of our
Complex class, we will add unary operators for the
+ and
- signs and for the complex conjugate.
Companion Objects
Besides traditional classes, Scala also allows defining objects with the
object keyword, which essentially defines a singleton class and its single instance at the same time. If an object has the same name as a class defined in the same source file, it becomes a companion object of that class. Companion objects have a special relationship to the classes they accompany, in particular they can access private methods and fields of that class.
Scala has no
static keyword, because the language creators felt that it contradicts true object orientation. Therefore, companion objects in Scala are the place to put members that you would define as static in other languages, for example constants, factory methods, and implicit conversions. Let’s define the following companion object for our
Complex class:
object Complex { val i = new Complex(0, 1) def apply(re: Double, im: Double) = new Complex(re, im) def apply(re: Double) = new Complex(re) implicit def fromDouble(d: Double) = new Complex(d) }
Our companion object has the following members:
iis a constant for the imaginary unit
- The two
applymethods are factory methods which allow creating
Complexinstances by invoking
Complex(...)instead of the less convenient
new Complex(...).
- The implicit conversion
fromDoubleis the one introduced above.
With the companion object in place, we can now write expressions such as:
scala> 2 + i + Complex(1, 2) res3: Complex = 3.0+3.0*i
Traits
Strictly speaking, complex numbers are not comparable to each other. Nevertheless, for practical purposes it would be useful to introduce a natural ordering based on their modulus. We would like of course to be able to compare complex numbers with the same operators <, <=, >, and >= that are used to compare other numeric types.
One way to achieve this would be to define all these 4 methods. However, this would introduce some boilerplate as the methods <=, >, and >= will of course all call the < method. In Scala, this can be avoided by using the powerful feature known as traits.
Traits are similar to interfaces in Java, since they are used to define object types by specifying the signature of the supported methods. Unlike Java, Scala allows traits to be partially implemented, so it is possible to define default implementations for some methods, similarly to Java 8 default methods. In Scala, a class can extend, or mix-in multiple traits due to mixin class composition.
For our example, we will mix-in the
Ordered trait into our
Complex class. This trait provides implementations of all 4 comparison operators, which all call the abstract method
compare. Therefore, to get all comparison operations “for free” all we need to do is provide a concrete implementation of this method.
class Complex(val re: Double, val im: Double) extends Ordered[Complex] { ... def compare(that: Complex) = !this compare !that ... }
Now, we can compare complex numbers as desired:
scala> Complex(1, 2) > Complex(3, 4) res4: Boolean = false scala> Complex(1, 2) < Complex(3, 4) res5: Boolean = true
Case Classes and Pattern Matching
Interestingly, comparing
Complex instances for equality still doesn’t work as expected:
scala> Complex(1, 2) == Complex(1, 2) res6: Boolean = false
This is because the
== method invokes the
equals method, which implements reference equality by default. One way to fix this would be to override the
equals method appropriately for our class. Of course, overriding
equals means overriding
hashCode as well. Although that would be rather trivial, it would add an unwelcome bit of boilerplate.
In Scala, we can skip all this if we define our class as a case class by adding the keyword
case. This adds automatically several useful capabilities, among them the following:
- adequate
equalsand
hashCodeimplementations
- a companion object with an
applyfactory method
- class parameters are implicitly defined as
val
case class Complex(re: Double, im: Double) ... }
Now, comparing for equality works as expected:
scala> i == Complex(0, 1) res6: Boolean = true
But the most important capability of case classes is that they can be used in pattern matching, another unique and powerful Scala feature. To illustrate it, let’s consider the following
toString implementation:
override def toString() = this match { case Complex.i => "i" case Complex(re, 0) => re.toString case Complex(0, im) => im.toString + "*i" case _ => asString } private def asString = re + (if (im < 0) "-" + -im else "+" + im) + "*i"
The above code matches
this against several patterns representing the constant
i, a real number, a pure imaginary number, and everything else. Although it could be written without pattern matching as well, this way is shorter and easier to understand. Pattern matching becomes really invaluable if you need to process complex object trees, as it provides a much more elegant and concise alternative to the Visitor design pattern typically used in such cases.
Wrap-up
The final version of our
Complex class looks as follows:
import scala.math._ case class Complex(re: Double, im: Double) extends Ordered[Complex] { private val modulus = sqrt(pow(re, 2) + pow(im, 2)) // Constructors def this(re: Double) = this(re, 0) // Unary operators def unary_+ = this def unary_- = new Complex(-re, -im) def unary_~ = new Complex(re, -im) // conjugate def unary_! = modulus // Comparison def compare(that: Complex) = !this compare !that // Arithmetic operations def +(c: Complex) = new Complex(re + c.re, im + c.im) def -(c: Complex) = this + -c def *(c: Complex) = new Complex(re * c.re - im * c.im, im * c.re + re * c.im) def /(c: Complex) = { require(c.re != 0 || c.im != 0) val d = pow(c.re, 2) + pow(c.im, 2) new Complex((re * c.re + im * c.im) / d, (im * c.re - re * c.im) / d) } // String representation override def toString() = this match { case Complex.i => "i" case Complex(re, 0) => re.toString case Complex(0, im) => im.toString + "*i" case _ => asString } private def asString = re + (if (im < 0) "-" + -im else "+" + im) + "*i" } object Complex { // Constants val i = new Complex(0, 1) // Factory methods def apply(re: Double) = new Complex(re) // Implicit conversions implicit def fromDouble(d: Double) = new Complex(d) implicit def fromFloat(f: Float) = new Complex(f) implicit def fromLong(l: Long) = new Complex(l) implicit def fromInt(i: Int) = new Complex(i) implicit def fromShort(s: Short) = new Complex(s) } import Complex._
With this remarkably short and elegant implementation we can do all the things described above, and a few more:
- create instances with
Complex(...)
- get the modulus with
!xand the conjugate with
~x
- perform arithmetic operations with the usual operators +, -, *, and /
- mix complex, real, and integer numbers freely in arithmetic expressions
- compare for equality with == and !=
- compare modulus-based with <, <=, >, and >=
- get the most natural string representation
If you are inclined for some experimentation, I would encourage you to paste the above code in the Scala interpreter (using
:paste first) and play around with these capabilities to get a better feeling.
Conclusion
Scala is considered by many to be a rather complex language. Perhaps this is why it’s so suitable for complex numbers … Puns aside, where some people see complexity I see unmatched elegance and power. I hope that this post illustrated this nicely. I am myself still learning Scala and far from being an expert. Are you aware of better ways to implement the above capabilities? I would love to hear about that.
Reference: Complex Numbers in Scala from our JCG partner Stoyan Rachev at the Stoyan Rachev’s Blog blog.
Nice introduction to Scala concepts. Looking at the final shape of your class, there are two things:
(1) Implicit conversions. You should only include the conversion from `Double`. Scala already provides an implicit mechanism called numeric widening which makes the implicit functions for `Short`, `Int`, `Float`, and even `Long` (something that can be argued about) superfluous.
(2) Avoiding overloading is usually a good thing. I don’t see any need for your secondary constructor (`def this(re: Double)`). Furthermore, employing default arguments you can also leave out the overloaded `apply` method in the companion object. Just use `
case class Complex(re: Double, im: Double = 0.0)`.
Interesting and fun little exercise. I have a couple of nits.
As someone already pointed out, a default argument in the constructor is preferable to an alternate constructor.
In the modulus calculation, you have
sqrt(pow(re, 2) + pow(im, 2))
I think just using sqrt(re * re + im * im) is cleaner and possibly more efficient. The “pow” function may take logarithms, which is unnecessary.
You don’t need the “new” in your + operator.
Is it standard to compare by modulus? I was not aware of that.
Thanks for your comments. You are right abut pow and new. No, comparing by modulus is not standard. In fact, there is no standard comparison for complex numbers. I picked this way of comparing for the sake of example only. | https://www.javacodegeeks.com/2013/02/complex-numbers-in-scala.html?ModPagespeed=noscript | CC-MAIN-2017-04 | refinedweb | 2,830 | 53.92 |
Hi, In this instructable, we’ll see how to use the Pyserial library in Python in order to make a serial connection via a COM Port (in our example COM3) and receive the temperature and humidity values from an MSP430 Microcontroller which is programmed to obtain data from a DHT11 sensor.
In addition to this, we’ll see how to write these serial output to a text file and then we’ll use matplotlib and numpy libraries to process the data from the text file and plot temperature & humidity change by time.
Step 1: Circuit Setup
In order to see how to obtain the value from the MSP430 microcontroller and send them to the serial port you can use the following instructables:……
You can also use other microcontroller boards such as Arduino, in that case the only thing you’ll need to pay attention is the COM port that you’re using and the speed (baudrate) of the connection.
Step 2: Installing Pyserial Library
We’ll use the following command in the command prompt (Windows) for installing Pyserial Library:
python -m pip install pyserial
Step 3: Python Code Using Serial Library
In this step, we’ll write the code that opens a serial connection, prints the received messages to the terminal (command prompt) and at the same time to a text file that we specify. You can change the port and baudrate settings with (ser.port and ser.baudrate)
While writing to the text file, the code also puts timestamps in the beginning of the line in order to log when the measurement was received.
Code:
import serial
from time import localtime, strftime
ser = serial.Serial()
ser.port = ‘COM3’
ser.baudrate = 19200
ser.open()
temp_file = open(‘temp_humid.txt’, ‘a’, encoding = ‘utf-8’)
while(True):
line = ser.readline()
print(line)
temp_file.write(strftime(“%d %b %Y %H%M%S “, localtime()))
temp_file.write(line.decode())
Step 4: Plotting Temperature and Humidity Change
In this final step, using the log file that we created in the previous step, we’ll plot the temperature and humidity change over time. In order to plot temperature, you need to set the line y = matrix_data[:,6] . In order to plot humidity, you need to set the line y = matrix_data[:,-2] (6 and -2 correspond to the colums representing temperature and humidity values respectively, you can check for the text file, first column having the indice 0)
Code:
import numpy as np
import sys
import matplotlib.pyplot as plt
np.set_printoptions(threshold=sys.maxsize)
read_file=input(‘Please enter file name to read: ‘)
test2_file=open(read_file, ‘r’, encoding = ‘utf-8’)
matrix_data = np.genfromtxt(test2_file)
x = matrix_data[:,3]
y = matrix_data[:,-2]
plt.plot(x,y)
plt.show()
Thank you for your time..
Source: Connecting to Microcontroller With Pyserial Library – Python | https://atmega32-avr.com/connecting-to-microcontroller-with-pyserial-library-python/ | CC-MAIN-2021-31 | refinedweb | 460 | 52.49 |
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Discrete Event Simulation CS1316: Representing Structure and Behavior
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Story Discrete event simulation Simulation time != real time Key ideas: A Queue A Queue is a queue, no matter how implemented. Different kinds of random Straightening time Inserting it into the right place Sorting it afterwards Building a discrete event simulation Graphics as the representation, not the real thing: The Model and the View
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Imagine the simulation… There are three Trucks that bring product from the Factory. On average, they take 3 days to arrive. Each truck brings somewhere between 10 and 20 products—all equally likely. We’ve got five Distributors who pick up product from the Factory with orders. Usually they want from 5 to 25 products, all equally likely. It takes the Distributors an average of 2 days to get back to the market, and an average of 5 days to deliver the products. Question we might wonder: How much product gets sold like this?
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Don’t use a Continuous Simulation We don’t want to wait that number of days in real time. We don’t even care about every day. There will certainly be timesteps (days) when nothing happens of interest. We’re dealing with different probability distributions. Some uniform, some normally distributed. Things can get out of synch A Truck may go back to the factory and get more product before a Distributor gets back. A Distributor may have to wait for multiple trucks to fulfill orders (and other Distributors might end up waiting in line)
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We use a Discrete Event Simulation We don’t simulate every moment continuously. We simulate discrete events.
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What’s the difference? No time loop In a discrete event simulation: There is no time loop. There are events that are scheduled. At each run step, the next scheduled event with the lowest time gets processed. The current time is then that time, the time that that event is supposed to occur. Key: We have to keep the list of scheduled events sorted (in order)
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What’s the difference? Agents don’t act() In a discrete event simulations, agents don’t act(). Instead, they wait for events to occur. They schedule new events to correspond to the next thing that they’re going to do. Key: Events get scheduled according to different probabilities.
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What’s the difference? Agents get blocked Agents can’t do everything that they want to do. If they want product (for example) and there isn’t any, they get blocked. They can’t schedule any new events until they get unblocked. Many agents may get blocked awaiting the same resource. More than one Distributor may be awaiting arrival of Trucks Key: We have to keep track of the Distributors waiting in line (in the queue)
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Key Ideas A Queue A Queue is a queue, no matter how implemented. Different kinds of random Straightening time Inserting it into the right place Sorting it afterwards
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Key idea #1: Introducing a Queue First-In-First-Out List First person in line is first person served I got here first! I got here second! I got here third! This is the front or head of the queue This is the tail of the queue
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First-in-First-out New items only get added to the tail. Never in the middle Items only get removed from the head. I got here first! I got here second! I got here third! This is the front or head of the queue This is the tail of the queue
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As items leave, the head shifts I got here first! AND NOW I’M UP! I got here second! I got here third! Now, this is the front or head of the queue This is the tail of the queue Served!
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As new items come in, the tail shifts I got here second! I got here third! Now, this is the front or head of the queue Now, this is the tail of the queue I got here fourth!
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What can we do with queues? push(anObject): Tack a new object onto the tail of the queue pop(): Pull the end (head) object off the queue. peek(): Get the head of the queue, but don’t remove it from the queue. size(): Return the size of the queue
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Building a Queue > Queue line = new Queue(); > line.push("Fred"); > line.push("Mary"); > line.push("Jose"); > line.size() 3
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Accessing a Queue > line.peek() "Fred" > line.pop() "Fred" > line.peek() "Mary" > line.pop() "Mary" > line.peek() "Jose" > line.pop() "Jose" > line.pop() java.util.NoSuchElementException: We don’t really want to peek() or pop() an empty queue, so we should probably check its size first.
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Building a Queue import java.util.*; // LinkedList representation /** * Implements a simple queue **/ public class Queue { /** Where we'll store our elements */ public LinkedList elements; /// Constructor public Queue(){ elements = new LinkedList(); }
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Queue methods /// Methods /** Push an object onto the Queue */ public void push(Object element){ elements.addFirst(element); } /** Peek at, but don't remove, top of queue */ public Object peek(){ return elements.getLast();} /** Pop an object from the Queue */ public Object pop(){ Object toReturn = this.peek(); elements.removeLast(); return toReturn; } /** Return the size of a queue */ public int size() { return elements.size();} We’re using a linked list to implement the Queue. The front of the LinkedList is the tail. The last of the LinkedList is the head.
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A queue is a queue, no matter what lies beneath. Our description of the queue minus the implementation is an example of an abstract data type (ADT). An abstract type is a description of the methods that a data structure knows and what the methods do. We can actually write programs that use the abstract data type without specifying the implementation. There are actually many implementations that will work for the given ADT. Some are better than others.
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Array-oriented Queue /** * Implements a simple queue **/ public class Queue2 { private static int ARRAYSIZE = 20; /** Where we'll store our elements */ private Object[] elements; /** The indices of the head and tail */ private int head; private int tail;
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Queue = array + head index + tail index /// Constructor public Queue2(){ elements = new Object[ARRAYSIZE]; head = 0; tail = 0; }
22
Queue2 methods /** Push an object onto the Queue */ public void push(Object element){ if ((tail + 1) >= ARRAYSIZE) { System.out.println("Queue underlying implementation failed"); } else { // Store at the tail, // then increment to a new open position elements[tail] = element; tail++; } } /** Peek at, but don't remove, top of queue */ public Object peek(){ return elements[head];} /** Pop an object from the Queue */ public Object pop(){ Object toReturn = this.peek(); if (((head + 1) >= ARRAYSIZE) || (head > tail)) { System.out.println("Queue underlying implementation failed."); return toReturn; } else { // Increment the head forward, too. head++; return toReturn;}} /** Return the size of a queue */ public int size() { return tail-head;} As the queue gets pushed and popped, it moves down the array.
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Same methods, same behavior Welcome to DrJava. > Queue2 line = new Queue2(); > line.push("Mary") > line.push("Kim") > line.push("Ron") > line.peek() "Mary" > line.pop() "Mary" > line.peek() "Kim" > line.size() 2 > line.pop() "Kim" > line.pop() "Ron" But can only handle up to 20 elements in the queue! Less if pushing and popping. Could shift elements to always allow 20. Not as good an implementation as the linked list implementation. (But uses less memory.)
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Key idea #2: Different kinds of random We’ve been dealing with uniform random distributions up until now, but those are the least likely random distribution in real life. How can we generate some other distributions, including some that are more realistic?
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Visualizing a uniform distribution import java.util.*; // Need this for Random import java.io.*; // For BufferedWriter public class GenerateUniform { public static void main(String[] args) { Random rng = new Random(); // Random Number Generator BufferedWriter output=null; // file for writing // Try to open the file try { // create a writer output = new BufferedWriter(new FileWriter("D:/cs1316/uniform.txt")); } catch (Exception ex) { System.out.println("Trouble opening the file."); } // Fill it with 500 numbers between 0.0 and 1.0, uniformly distributed for (int i=0; i < 500; i++){ try{ output.write("\t"+rng.nextFloat()); output.newLine(); } catch (Exception ex) { System.out.println("Couldn't write the data!"); System.out.println(ex.getMessage()); } // Close the file try{ output.close();} catch (Exception ex) {System.out.println("Something went wrong closing the file");} } By writing out a tab and the integer, we don’t have to do the string conversion.
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How do we view a distribution? A Histogram
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A Uniform Distribution
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A Normal Distribution // Fill it with 500 numbers between -1.0 and 1.0, normally distributed for (int i=0; i < 500; i++){ try{ output.write("\t"+rng.nextGaussian()); output.newLine(); } catch (Exception ex) { System.out.println("Couldn't write the data!"); System.out.println(ex.getMessage()); }
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Graphing the normal distribution The end aren’t actually high— the tails go further.
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How do we shift the distribution where we want it? // Fill it with 500 numbers with a mean of 5.0 and a //larger spread, normally distributed for (int i=0; i < 500; i++){ try{ output.write("\t"+((range * rng.nextGaussian())+mean)); output.newLine(); } catch (Exception ex) { System.out.println("Couldn't write the data!"); System.out.println(ex.getMessage()); } Multiply the random nextGaussian() by the range you want, then add the mean to shift it where you want it.
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A new normal distribution
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Key idea #3: Straightening Time Straightening time Inserting it into the right place Sorting it afterwards We’ll actually do these in reverse order: We’ll add a new event, then sort it. Then we’ll insert it into the right place.
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Exercising an EventQueue public class EventQueueExercisor { public static void main(String[] args){ // Make an EventQueue EventQueue queue = new EventQueue(); // Now, stuff it full of events, out of order. SimEvent event = new SimEvent(); event.setTime(5.0); queue.add(event); event = new SimEvent(); event.setTime(2.0); queue.add(event); event = new SimEvent(); event.setTime(7.0); queue.add(event); event = new SimEvent(); event.setTime(0.5); queue.add(event); event = new SimEvent(); event.setTime(1.0); queue.add(event); // Get the events back, hopefull in order! for (int i=0; i < 5; i++) { event = queue.pop(); System.out.println("Popped event time:"+event.getTime()); } We’re stuffing the EventQueue with events whose times are out of order.
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If it works right, should look like this: Welcome to DrJava. > java EventQueueExercisor Popped event time:0.5 Popped event time:1.0 Popped event time:2.0 Popped event time:5.0 Popped event time:7.0
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Implementing an EventQueue import java.util.*; /** * EventQueue * It's called an event "queue," but it's not really. * Instead, it's a list (could be an array, could be a linked list) * that always keeps its elements in time sorted order. * When you get the nextEvent, you KNOW that it's the one * with the lowest time in the EventQueue **/ public class EventQueue { private LinkedList elements; /// Constructor public EventQueue(){ elements = new LinkedList(); }
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Mostly, it’s a queue public SimEvent peek(){ return (SimEvent) elements.getFirst();} public SimEvent pop(){ SimEvent toReturn = this.peek(); elements.removeFirst(); return toReturn;} public int size(){return elements.size();} public boolean empty(){return this.size()==0;}
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Two options for add() /** * Add the event. * The Queue MUST remain in order, from lowest time to highest. **/ public void add(SimEvent myEvent){ // Option one: Add then sort elements.add(myEvent); this.sort(); //Option two: Insert into order //this.insertInOrder(myEvent); }
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There are lots of sorts! Lots of ways to keep things in order. Some are faster – best are O(n log n) Some are slower – they’re always O(n 2 ) Some are O(n 2 ) in the worst case, but on average, they’re better than that. We’re going to try an insertion sort
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How an insertion sort works Consider the event at some position (1..n) Compare it to all the events before that position backwards—towards 0. If the comparison event time is LESS THAN the considered event time, then shift the comparison event down to make room. Wherever we stop, that’s where the considered event goes. Consider the next event…until done
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Insertion Sort public void sort(){ // Perform an insertion sort // For comparing to elements at smaller indices SimEvent considered = null; SimEvent compareEvent = null; // Just for use in loop // Smaller index we're comparing to int compare; // Start out assuming that position 0 is "sorted" // When position==1, compare elements at indices 0 and 1 // When position==2, compare at indices 0, 1, and 2, etc. for (int position=1; position < elements.size(); position++){ considered = (SimEvent) elements.get(position); // Now, we look at "considered" versus the elements // less than "compare" compare = position; // While the considered event is greater than the compared event, // it's in the wrong place, so move the elements up one. compareEvent = (SimEvent) elements.get(compare-1); while (compareEvent.getTime() > considered.getTime()) { elements.set(compare,elements.get(compar e-1)); compare = compare-1; // If we get to the end of the array, stop if (compare <= 0) {break;} // else get ready for the next time through the loop else {compareEvent = (SimEvent) elements.get(compare-1);} } // Wherever we stopped, this is where "considered" belongs elements.set(compare,considered); } // for all positions 1 to the end } // end of sort() Trace this out to convince yourself it works!
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Useful Links on Sorting /PLDS210/sorting.html /PLDS210/sorting.html a/sorting-demo.html a/sorting-demo.html /sorters/insertsort.html /sorters/insertsort.html These include animations that help to see how it’s all working Recommended
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Option #2: Put it in the right place /** * Add the event. * The Queue MUST remain in order, from lowest time to highest. **/ public void add(SimEvent myEvent){ // Option one: Add then sort //elements.add(myEvent); //this.sort(); //Option two: Insert into order this.insertInOrder(myEvent); }
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insertInOrder() /** * Put thisEvent into elements, assuming * that it's already in order. **/ public void insertInOrder(SimEvent thisEvent){ SimEvent comparison = null; // Have we inserted yet? boolean inserted = false; for (int i=0; i < elements.size(); i++){ comparison = (SimEvent) elements.get(i); // Assume elements from 0..i are less than thisEvent // If the element time is GREATER, insert here and // shift the rest down if (thisEvent.getTime() < comparison.getTime()) { //Insert it here inserted = true; elements.add(i,thisEvent); break; // We can stop the search loop } } // end for // Did we get through the list without finding something // greater? Must be greater than any currently there! if (!inserted) { // Insert it at the end elements.addLast(thisEvent);} } Again, trace it out to convince yourself that it works!
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Finally: A Discrete Event Simulation Now, we can assemble queues, different kinds of random, and a sorted EventQueue to create a discrete event simulation.
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Running a DESimulation Welcome to DrJava. > FactorySimulation fs = new FactorySimulation(); > fs.openFrames("D:/temp/"); > fs.run(25.0)
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What we see (not much)
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The detail tells the story Time:1.7078547183397625Distributor: 0 Arrived at warehouse Time:1.7078547183397625Distributor: 0 is blocking >>> Timestep: 1 Time:1.727166341118611Distributor: 3 Arrived at warehouse Time:1.727166341118611Distributor: 3 is blocking >>> Timestep: 1 Time:1.8778754913001443Distributor: 4 Arrived at warehouse Time:1.8778754913001443Distributor: 4 is blocking >>> Timestep: 1 Time:1.889475045031698Distributor: 2 Arrived at warehouse Time:1.889475045031698Distributor: 2 is blocking >>> Timestep: 1 Time:3.064560375192933Distributor: 1 Arrived at warehouse Time:3.064560375192933Distributor: 1 is blocking >>> Timestep: 3 Time:3.444420374970288Truck: 2 Arrived at warehouse with load 13 Time:3.444420374970288Distributor: 0 unblocked! Time:3.444420374970288Distributor: 0 Gathered product for orders of 11 >>> Timestep: 3 Time:3.8869697922832698Truck: 0 Arrived at warehouse with load 18 Time:3.8869697922832698Distributor: 3 unblocked! Time:3.8869697922832698Distributor: 3 Gathered product for orders of 12 >>> Timestep: 3 Time:4.095930381479024Distributor: 0 Arrived at market >>> Timestep: 4 Time:4.572840072576855Truck: 1 Arrived at warehouse with load 20 Time:4.572840072576855Distributor: 4 unblocked! Time:4.572840072576855Distributor: 4 Gathered product for orders of 19 Notice that time 2 never occurs!
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What questions we can answer How long do distributors wait? Subtract the time that they unblock from the time that they block How much product sits in the warehouse? At each time a distributor leaves, figure out how much is left in the warehouse. How long does the line get at the warehouse? At each block, count the size of the queue. Can we move more product by having more distributors or more trucks? Try it!
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How DESimulation works
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FactorySimulation: Extend a few classes
52.
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What a DESimulation does: // While we're not yet at the stop time, // and there are more events to process while ((now < stopTime) && (!events.empty())) { topEvent = events.pop(); // Whatever event is next, that time is now now = topEvent.getTime(); // Let the agent now that its event has occurred topAgent = topEvent.getAgent(); topAgent.processEvent(topEvent.getMessage()); // repaint the world to show the movement // IF there is a world if (world != null) { world.repaint();} // Do the end of step processing this.endStep((int) now); } As long as there are events in the queue, and we’re not at the stopTime: Grab an event. Make it’s time “now” Process the event.
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What’s an Event (SimEvent)? /** * SimulationEvent (SimEvent) -- an event that occurs in a simulation, * like a truck arriving at a factory, or a salesperson leaving the * market **/ public class SimEvent{ /// Fields /// /** When does this event occur? */ public double time; /** To whom does it occur? Who should be informed when it occurred? */ public DEAgent whom; /** What is the event? We'll use integers to represent the meaning * of the event -- the "message" of the event. * Each agent will know the meaning of the integer for themselves. **/ public int message; It’s a time, an Agent, and an integer that the Agent will understand as a message
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DEAgent: Process events, block if needed DEAgents define!
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An Example: A Truck /** * Truck -- delivers product from Factory * to Warehouse. **/ public class Truck extends DEAgent { /////// Constants for Messages public static final int FACTORY_ARRIVE = 0; public static final int WAREHOUSE_ARRIVE = 1; ////// Fields ///// /** * Amount of product being carried **/ public int load;
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How Trucks start /** * Set up the truck * Start out at the factory **/ public void init(Simulation thisSim){ // Do the default init super.init(thisSim); this.setPenDown(false); // Pen up this.setBodyColor(Color.green); // Let green deliver! // Show the truck at the factory this.moveTo(30,350); // Load up at the factory, and set off for the warehouse load = this.newLoad(); ((DESimulation) thisSim).addEvent( new SimEvent(this,tripTime(),WAREHOUSE_ARRIVE)); } The truck gets a load, then schedules itself to arrive at the Warehouse.
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tripTime() uses the normal distribution /** A trip distance averages 3 days */ public double tripTime(){ double delay = randNumGen.nextGaussian()+3; if (delay < 1) // Must take at least one day {return 1.0+((DESimulation) simulation).getTime();} else {return delay+((DESimulation) simulation).getTime();} }
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newLoad() uses uniform /** A new load is between 10 and 20 on a uniform distribution */ public int newLoad(){ return 10+randNumGen.nextInt(11); }
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How a Truck processes Events /** * Process an event. * Default is to do nothing with it. **/ public void processEvent(int message){ switch(message){ case FACTORY_ARRIVE: // Show the truck at the factory ((DESimulation) simulation).log(this.getName()+"\t Arrived at factory"); this.moveTo(30,350); // Load up at the factory, and set off for the warehouse load = this.newLoad(); ((DESimulation) simulation).addEvent( new SimEvent(this,tripTime(),WAREHOUSE_ARRIVE)); break;
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Truck Arriving at the Warehouse case WAREHOUSE_ARRIVE: // Show the truck at the warehouse ((DESimulation) simulation).log(this.getName()+"\t Arrived at warehouse with load \t"+load); this.moveTo(50,50); // Unload product -- takes zero time (unrealistic!) ((FactorySimulation) simulation).getProduct().add(load); load = 0; // Head back to factory ((DESimulation) simulation).addEvent( new SimEvent(this,tripTime(),FACTORY_ARRIVE)); break;
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What Resources do They keep track of what amount they have available (of whatever the resource is). They keep a queue of agents that are blocked on this resource. They can add to the resource, or have it consume(d). When more resource comes in, the head of the queue gets asked if it’s enough. If so, it can unblock.
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How Resources alert agents /** * Add more produced resource. * Is there enough to unblock the first * Agent in the Queue? **/ public void add(int production) { amount = amount + production; if (!blocked.empty()){ // Ask the next Agent in the queue if it can be unblocked DEAgent topOne = (DEAgent) blocked.peek(); // Is it ready to run given this resource? if (topOne.isReady(this)) { // Remove it from the queue topOne = (DEAgent) blocked.pop(); // And tell it it’s unblocked topOne.unblocked(this); }
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An example blocking agent: Distributor /** * Distributor -- takes orders from Market to Warehouse, * fills them, and returns with product. **/ public class Distributor extends DEAgent { /////// Constants for Messages public static final int MARKET_ARRIVE = 0; public static final int MARKET_LEAVE = 1; public static final int WAREHOUSE_ARRIVE = 2; /** AmountOrdered so-far */ int amountOrdered;
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Distributors start in the Market public void init(Simulation thisSim){ //First, do the normal stuff super.init(thisSim); this.setPenDown(false); // Pen up this.setBodyColor(Color.blue); // Go Blue! // Show the distributor in the market this.moveTo(600,460); // At far right // Get the orders, and set off for the warehouse amountOrdered = this.newOrders(); ((DESimulation) thisSim).addEvent( new SimEvent(this,tripTime(),WAREHOUSE_ARRIVE)); }
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Distributors have 3 events Arrive in Market: Schedule how long it’ll take to deliver. Leave Market: Schedule arrive at the Factory Arrive at Warehouse: Is there enough product available? If not, block and wait for trucks to bring enough product.
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Processing Distributor Events /** * Process an event. * Default is to do nothing with it. **/ public void processEvent(int message){ switch(message){ case MARKET_ARRIVE: // Show the distributor at the market, far left ((DESimulation) simulation).log(this.getName()+"\t Arrived at market"); this.moveTo(210,460); // Schedule time to deliver ((DESimulation) simulation).addEvent( new SimEvent(this,timeToDeliver(),MARKET_LEAVE)); break;
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Leaving the Market case MARKET_LEAVE: // Show the distributor at the market, far right ((DESimulation) simulation).log(this.getName()+"\t Leaving market"); this.moveTo(600,460); // Get the orders, and set off for the warehouse amountOrdered = this.newOrders(); ((DESimulation) simulation).addEvent( new SimEvent(this,tripTime(),WAREHOUSE_ARRIVE)); break;
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Arriving at the Warehouse case WAREHOUSE_ARRIVE: // Show the distributor at the warehouse ((DESimulation) simulation).log(this.getName()+"\t Arrived at warehouse"); this.moveTo(600,50); // Is there enough product available? Resource warehouseProduct = ((FactorySimulation) simulation).getProduct(); if (warehouseProduct.amountAvailable() >= amountOrdered) { // Consume the resource for the orders warehouseProduct.consume(amountOrdered); // Zero time to load? ((DESimulation) simulation).log(this.getName()+"\t Gathered product for orders of \t"+amountOrdered); // Schedule myself to arrive at the Market ((DESimulation) simulation).addEvent( new SimEvent(this,tripTime(),MARKET_ARRIVE)); } else {// We have to wait until more product arrives! ((DESimulation) simulation).log(this.getName()+"\t is blocking"); waitFor(((FactorySimulation) simulation).getProduct());} break;
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Is there enough product? /** Are we ready to be unlocked? */ public boolean isReady(Resource res) { // Is the amount in the factory more than our orders? return ((FactorySimulation) simulation).getProduct().amountAvailable() >= amountOrdered;}
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If so, we’ll be unblocked /** * I've been unblocked! * @param resource the desired resource **/ public void unblocked(Resource resource){ super.unblocked(resource); // Consume the resource for the orders ((DESimulation) simulation).log(this.getName()+"\t unblocked!"); resource.consume(amountOrdered); // Zero time to load? ((DESimulation) simulation).log(this.getName()+"\t Gathered product for orders of \t"+amountOrdered); // Schedule myself to arrive at the Market ((DESimulation) simulation).addEvent( new SimEvent(this,tripTime(),MARKET_ARRIVE)); }
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The Overall Factory Simulation /** * FactorySimulation -- set up the whole simulation, * including creation of the Trucks and Distributors. **/ public class FactorySimulation extends DESimulation { private Resource product; /** * Accessor for factory **/ public FactoryProduct getFactory(){return factory;}
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Setting up the Factory Simulation public void setUp(){ // Let the world be setup super.setUp(); // Give the world a reasonable background FileChooser.setMediaPath("D:/cs1316/MediaSources/"); world.setPicture(new Picture( FileChooser.getMediaPath("EconomyBackground.jpg")) ); // Create a warehouse resource product = new Resource(); //Track product // Create three trucks Truck myTruck = null; for (int i=0; i<3; i++){ myTruck = new Truck(world,this); myTruck.setName("Truck: "+i);} // Create five Distributors Distributor sales = null; for (int i=0; i<5; i++){ sales = new Distributor(world,this); sales.setName("Distributor: "+i);} }
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The Master Data Structure List: We use almost everything here! Queues: For storing the agents waiting in line. EventQueues: For storing the events scheduled to occur. LinkedList: For storing all the agents.
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I can run normal HTML pages, but no .aspx files. If I call the aspx page directly I get a 404 - file not found - error message. This only happens with .aspx files.
I open the page yesterday, it is working fine,, but today I am getting this error...Parser Error Message: Ambiguous match found.Source Error:
Line 1: <%@ Register TagPrefix="NetMenu" Namespace="CYBERAKT.WebControls.Navigation" Assembly="ASPnetMenu" %>
Line 2: <%@ Page language="c#" Codebehind="ClientDetails.aspx.cs" AutoEventWireup="false"
[code]...
I have textbox with search button the result it's show , but if there is a way to count how many rows was found were cathing the data form database. I'm using gridview + ado.net + gridview i handle all the events manually....
protected void btnSearch_Click(object sender, EventArgs e) {
if (txtSearch.Text == "") {
lblMessage.Text = "";
lblMessage.Text = "Empty charchter, Try Again";
[code]....
I am trying to use the autocomplete extender but it won't fetch the data. Why is it not working?
<cc1:AutoCompleteExtender
</cc1:AutoCompleteExtender>
public partial class Controls_EmployeeByName : System.Web.UI.UserControl
[Code] ....?
I just tested a new aspx-website and in the debug mode it works fine.
But when I publish it on the server 2003 with IIS6 then it works first and after several requests I get an error message page not found.
The page itself exists and I think that it is only unavailable on the server.
when I put a break point i get this error message:
Error 1 The type or namespace name 'X509Certificate' could not be found (are you missing a using directive or an assembly reference?) D:UsersatttDesktop
fre
etetrtDefault.aspx.cs 7 53 D:...attt | http://asp.net.bigresource.com/AJAX-AutoCompleteExtender-Display-No-records-found-message-when-no-matches-found-DOEJQ.html | CC-MAIN-2018-34 | refinedweb | 1,533 | 66.74 |
Klaus Schmidinger schrieb: > On 02/02/08 16:27, Klaus Schmidinger wrote: >>). >> [ .. ] > > Nevermind, I just found it myself: it must be +5 instead of +4 in > > inline int TsPayloadOffset(const uchar *Data) > { > return (Data[3] & ADAPT_FIELD) ? Data[4] + 5 : 4; > } > > Now it works - and Transfer-Mode never switched as fast as this :-) I don't know what causes this issue, but with this patch enabled, VDR refuses to play radio-channel (audio) with the radio-plugin (with RDS enabled). When i disable the radio-plugin, audio works; when i remove the patch, audio works with the plugin enabled. -> i removed this patch. regards, Friedhelm. | http://www.linuxtv.org/pipermail/vdr/2008-February/015663.html | CC-MAIN-2014-42 | refinedweb | 104 | 61.06 |
Whether you’re starting from scratch, or looking at a migration, deploying Live@edu can quickly become a very big deal if you don’t plan for the future. Since joining the UK Education Team here at Microsoft I’ve had a lot of opportunities to speak to customers who have been through the process. Recently I visited Llantwit Major School in South Wales to help hands-on with their deployment of Live@edu. I spent time discussing the options for deployment and helping them plan; now I’ll share what I’ve learned with you so that you can plan your Live@edu deployment more effectively.
I can’t have a single conversation about deploying ‘cloud’ services these days without talking about ID management. When you provision users in Live@edu you immediately begin creating another island of identity to manage. How you decide to manage that is very important. Some food for thought:
How will you provision your users? The most popular ways are by using a CSV file, or a piece of software like Identity Lifecycle Manager (ILM) with Outlook Live Directory Sync. The CSV file option either through PowerShell or the Exchange Control Panel is free, but is the most manual way to manage identity and requires the most amount of on-going time to configure. ILM, however, is very automated and the process for managing your joiners and leavers can be simplified greatly using software like this to manage that task.
How will you manage passwords? It is possible to make use of the Password Change Notification Service (PCNS) with ILM to synchronise passwords, making it much easier for your end users as they only need to manage one password. This can reduce the impact on your helpdesk and is less confusing for your users. By default there is no synchronisation of passwords between your on-premise directory and Live@edu; without PCNS users would have to manage two sets of credentials. Single-Sign-On (SSO) is also an option; integrating Live@edu into a portal or VLE such as Moodle or SharePoint using the SSO Toolkit removes the need for users to know their Live@Edu password, or their username!
Which namespace will you use? Many schools have a single namespace, for example “@larchschool.co.uk”, with both staff and students having email addresses in this format. Equally, many schools opt to migrate their students first, keeping their staff on-premise. This presents a big question: who keeps their existing email address, and who gets a new one? The good news is that it is possible to share an SMTP namespace between two mail servers, so your users can be split between your local mail server and Live@edu while still keeping their existing email addresses. If you’re not looking at doing an all-in jump to the ‘cloud’ this shared-address-space scenario will make it far easier for your users as they can keep their already established identity while taking advantage of the enhanced features of Live@edu.
These are just four things that you should consider when thinking about the identity management of your Live@edu deployment. There are many more things that may be peculiar to your institution, and the points above are by no means exhaustive but they are worth giving a few moments thought as a good, well thought out, deployment will benefit you and your users much more in the longer term than a hasty one.
If you’re looking at deploying Live@edu why not check out, a great forum where you can ask questions and get advice from other Live@edu users as well as Microsoft staff. | http://blogs.msdn.com/b/ukeducloud/archive/2011/04/11/tips-amp-considerations-when-deploying-live-edu.aspx | CC-MAIN-2015-22 | refinedweb | 613 | 57.2 |
This series explores aspects of technology that are shaping Java™ development now and in the future. The premise of Java development 2.0 is that development is happening at a more rapid pace, thanks to both a burst of innovation in the open source world and the commoditization of hardware. You can rent or borrow someone else's hardware platform to host your application (largely assembled from open source libraries, tools, and frameworks) at a fraction of the cost of acquiring and maintaining your own infrastructure.
The first series installment, "Hello Google App Engine," examined the notion of borrowing Google's infrastructure to host your Java application for free, but at some cost in terms of flexibility. In subsequent articles, you learned the differences between App Engine and Amazon's EC2. Last month's column ("REST up with CouchDB and Groovy's RESTClient") surveyed an up-and-coming alternative to relational databases: CouchDB. CouchDB's lack of a schema and its document-oriented nature might have seemed new to you, but you already saw another schemaless datastore in action with Google App Engine.
This article takes the series full circle, back to Google App Engine. The open source world has already jumped on the App Engine bandwagon, with frameworks starting to emerge that facilitate developing applications targeted for the platform. You'll see how an open source project called Gaelyk is making it even easier to build applications that leverage many of technologies the series has covered to this point.
Lightweight is the new rapid
Although Google's infrastructure is largely free to use (remember, it costs you money once you reach 500MB of storage and the bandwidth for serving about 5 million page views a month), it does come at a cost in terms of flexibility. Google's infrastructure supports Java technology, but not all core Java libraries and related open source libraries. The App Engine is a platform — you must develop to it. Unsurprisingly, though, open source innovations are helping to overcome what may be perceived as barriers to adoption of Google App Engine.
One such upstart project, dubbed Gaelyk, is a slick framework that facilitates the development of lightweight applications, written in Groovy, that properly leverage the Model-View-Controller (MVC) pattern. And through the magic of Groovy, Gaelyk throws in a few ease-of-use facilities on top of the App Engine's APIs. Moreover, you can use Gaelyk alongside the Google App Engine plug-in for Eclipse. Rapid development and deployment of Google App Engine applications couldn't get any easier.
"REST up with CouchDB and Groovy's RESTClient" leveraged a parking-ticketing system to demonstrate the nature of a document-oriented database. Following suit, in this article I'm going to create a Web application that enables the creation, update, and removal of parking tickets. The Google persistence architecture isn't a document-oriented one, but its schemaless nature permits a rather flexible model. Thus the Web application will try to model a parking ticket as closely as possible by capturing:
- Officer's name
- Date
- Location
- Offense
- Any associated notes
I'll just leave the location as a generic text box, because someone can represent where an offense has occurred in a variety of ways — such as in the parking lot of Best Buy or at the corner of 18th St. and D St. In essence, I won't try to delineate a specific format, because it isn't necessarily germane to the domain anyway.
In order to get started, you need to have the Google App Engine plug-in for Eclipse installed (see "Hello Google App Engine" for instructions). You also need to download the Gaelyk JAR file from the project's Web site (see Resources). Remember where this download resides, because you'll need to move it into a specific directory shortly.
The Gaelyk framework relies on Groovy, so you also need the latest Groovy release: a simple JAR file, groovy-all-1.6.5.jar at the time of this writing (see Resources). Lastly, you need to create an application ID via the Google App Engine admin panel. (You can reuse the one you created in "Hello Google App Engine" if you like.)
Next, create a new Google Web Application Project within Eclipse, click the Next button, and fill out the appropriate information. Be sure to uncheck the Use Google Web Toolkit option, as I've done in Figure 1, because you don't need it:
Figure 1. Creating a Google Apps Project in Eclipse
Click the Finish button, and you'll have yourself the beginnings of a code base.
Now copy both the Groovy and Gaelyk JARs into your newly created project's war/WEB-INF/lib directory, shown in Figure 2:
Figure 2. Gaelyk's required libraries
In order to configure Gaelyk, you need to provide Google App Engine with some additional information by editing the WEB-INF/appengine-web.xml file. Place your application ID in the application section at the top of this file, and add the bit of XML shown in Listing 1:
Listing 1. Required updates to App Engine's configuration
<static-files> <exclude path="/WEB-INF/**.groovy" /> <exclude path="**.gtpl" /> </static-files>
This addition prevents Google App Engine from serving up various files statically that you'll end up creating as a part of using Gaelyk. As you'll see, Gaelyk leverages a templating model. Thus, files ending in .gtpl will act like JavaServer Pages (JSPs) and will be processed via the framework rather than by App Engine.
Next, open up the web.xml file, also found in the WEB-INF directory. This is the standard Web application configuration file we've all come to love over the years. (You worked with this file when you first visited both App Engine and EC2.) This file needs to map various patterns to particular servlets, so make your file look like Listing 2:
Listing 2. Updated web.xml file
<?xml version="1.0" encoding="utf-8"?> <web-app xmlns: <servlet> <servlet-name>GroovletServlet</servlet-name> <servlet-class>groovyx.gaelyk.GaelykServlet</servlet-class> </servlet> <servlet> <servlet-name>TemplateServlet</servlet-name> <servlet-class>groovyx.gaelyk.GaelykTemplateServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>GroovletServlet</servlet-name> <url-pattern>*.groovy</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>TemplateServlet</servlet-name> <url-pattern>*.gtpl</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.gtpl</welcome-file> </welcome-file-list> </web-app>
Note that the web.xml file specifies that the welcome file be index.gtpl; thus, rename the index.html file that the Eclipse plug-in generated for you to index.gtpl. (Just select the file and hit F2, if you are on Windows®.)
With the proper libraries in place and both XML files configured correctly, you can verify things are working by editing the index.gtpl file to match the contents of Listing 3:
Listing 3. A simple GTPL file
<html> <head><title>A Simple GTPL</title></head> <body> <b><% print "Hello Gaelyk!".replace(" ", " from ") %></b> <p> <ol> <% def wrd = "Groovy" wrd.each{ letter -> %> <li><%= letter %></li> <% } %> </ol> </p> </body> </html>
As you can see, GTPL files (or Gaelyk/Groovy templates) in Gaelyk are just like JSPs: you can add behavior in scriptlets (in this case, the behavior is Groovy). Note that you can use closures and reference variables later too.
Save your index.gtpl file and then select the project's base directory in Eclipse, right-click, select Run As, and select the Web Application option that contains a blue G logo, as shown in Figure 3:
Figure 3. Running as a Google Web application
By default, this launcher starts a local instance of Jetty on port 8080. If you'd like to change ports, select the Run Configurations option and configure the port via the options panel provided by the plug-in.
Now that a local instance of your Gaelyk Web application is running, open a Web browser and go to. The output of your lovely index.gtpl should look like Figure 4:
Figure 4. Hello world!
That was easy, wasn't it?
Easy persistence
The ticketing system is simple. It' offers a Web form for creating tickets and a list functionality to view, delete, and edit tickets. I'll start things off by creating a simple HTML form via a Gaelyk template, and I'll call it createticket.gtpl. This form, shown in Figure 5, tries to capture relevant data associated with an individual parking ticket:
Figure 5. A simple ticket form
The form will submit to a groovlet; accordingly, create a groovy folder inside the WEB-INF directory in your project. This is where you'll place your groovlets. (You did this in "Hello Google App Engine" too.) The create-ticket form will submit to a createticket.groovy file. Create this file in the newly created groovy directory.
You can certainly use JDO and Java Persistence API (JPA) code in Gaelyk, but there's
another handy way to interface with the underlying datastore: by using Google's
Entity object. The Gaelyk team has enhanced the
Entity object via some Groovy magic to make working with persistent objects amazingly simple.
In this case, I'd like to capture the form elements submitted via the createticket.gtpl page and create a new ticket in the system. By using the
Entity class, I don't need to define a POJO-like object to represent a ticket (as I did in "Hello Google App Engine" when I created a
Triathlon JDO object). I can simply model a ticket in a Groovy fashion and save it almost as effortlessly.
Consequently, I can grab the parameters submitted by the form via Gaelyk's handy
params object (which, by the way, Grails also offers) and create an
Entity instance, as shown in Listing 4:
Listing 4. Creating an
Entity
def formatter = new SimpleDateFormat("MM/dd/yyyy") def offensedate = formatter.parse("${params.of_month}/${params.of_day}/${params.of_year}") def ticket = new Entity("ticket") ticket.officer = params.officer ticket.license = params.plate ticket.issuseDate = offensedate ticket.location = params.location ticket.notes = params.notes ticket.offense = params.offense
Note that the
ticket variable is an instance of
Entity. The
"ticket" String represents the kind of entity this is. This'll become handy in searching for tickets. Next, I automagically assign property values to the
Entity instance associated with tickets. Now
ticket.officer represents the value of the
officer parameter submitted via the Web page form. Because the form contains three fields for date, I also create a date instance using a
SimpleDateFormat and set that value to
issueDate.
At this point, I've got an object that represents a ticket. All I need to do now is save it with:
ticket.save()
Now that I've persisted a ticket, I'll forward users to a page where they can view the ticket. That's easy too. I simply forward to a view-ticket Groovlet (for processing):
redirect "viewticket.groovy?id=${ticket.key.id}"
As you can see, I've created a parameter dubbed
id and set it to the key of the saved ticket instance, which Google App Engine generated. Accordingly, the create-ticket Groovlet is terse yet highly functional — all of it facilitated by Gaelyk.
Easy views
In the preceding example, after I created the
ticket instance, I proceeded to redirect the request to another Groovlet — one that facilitates viewing a ticket. In this Groovlet, I've coded a Google App Engine read, so to speak. The
id that was passed along is then used to find the newly created instance. In this case, I'm using Google's
KeyFactory, which is used to create an instance of Google's
Key object. The
Key then is used to find the corresponding ticket instance via the
datastoreService, which Gaelyk has automatically added to the binding of any Groovlet instance within the framework, as you can seeing Listing 5:
Listing 5. Viewing an
Entity
import com.google.appengine.api.datastore.KeyFactory if (params["id"]) { def id = Long.parseLong(params["id"]) try { def key = KeyFactory.createKey("ticket", id) def ticket = datastoreService.get(key) request.setAttribute "ticket", ticket forward "viewticket.gtpl" } catch (Throwable t) { //forward to some error page... } } else { forward "index.gtpl" }
Once the corresponding
ticket is found, the ticket is placed into the HTTP
request object (which is already present in a Groovlet) and then processing is forwarded to the viewticket.gtpl page. Just like any other JSP in a Web application, this Web page displays the corresponding attributes associated with the passed-in ticket.
As you can see in Listing 6, Gaelyk supports includes. That is, in your .gtpl
files, you can include other files, just as you can in normal JSPs. Likewise, all .gtpl files have an instance of the HTTP
Request object handy (via the
request variable).
Listing 6. Viewing a single
Entity GTPL
<% include "/WEB-INF/includes/header.gtpl" %> <% def ticket = request.getAttribute("ticket") %> <div class="info"> <h2>Parking Ticket</h2> </div> <table> <tr> <th>Issuing Officer</th> <th>Vehicle Plate</th> <th>Date</th> <th>Offense</th> <th>Location</th> <th>Notes</th> </tr> <tr> <td>${ticket.officer} </td> <td>${ticket.license}</td> <td>${ticket.issuseDate}</td> <td>${ticket.offense}</td> <td>${ticket.location}</td> <td>${ticket.notes}</td> </tr> </table> <% include "/WEB-INF/includes/footer.gtpl" %>
As you can probably see by this point, Gaelyk makes building lightweight Web applications on Google App Engine a breeze. And working with the App Engine's persistence store couldn't be easier. The low-level API you use when working with
Entity objects does take a bit of getting used to. Queries require some thinking (kind of like querying with CouchDB, in a way). For instance, viewing a list of created tickets requires some code like Listing 7:
Listing 7. Viewing a collection of
Entitys
import com.google.appengine.api.datastore.Query import static com.google.appengine.api.datastore.FetchOptions.Builder.withLimit try { def query = new Query("ticket") query.addSort("issuseDate", Query.SortDirection.DESCENDING) def preparedQuery = datastoreService.prepare(query) def tickets = preparedQuery.asList( withLimit(10) ) request.setAttribute "tickets", tickets forward "index.gtpl" } catch (Throwable t) { forward "index.gtpl" }
Listing 7 leverages App Engine's
Query object. As you can see, you can add sort-like features to queries and even limit how many results are returned. No SQL is used, but rest assured that data is being stored and can be retrieved, albeit just a bit differently.
Just as in "Hello Google App Engine," deployment into the cloud is a breeze. Via the plug-in, simply click the Deploy App Engine Project and let Google take it from there. In fact, you can download the code for this article and do just that. The code will fill in some gaps that I didn't have space to cover in a single article. For example, I've implemented removing tickets, and the user interaction with the ticketing system is slightly enhanced, so you'll see a bit more of Gaelyk in action.
Fast development made easy
The cloud and schemaless datastores, bolstered by open source innovations, are certainly part of the future of Java development. Both have a low barrier to adoption; in this article's example, both the hardware and the software are completely free. And once Google does start to charge you money, you're bound to be making your own — 5 million hits a month is a tremendous amount of traffic. The Gaelyk framework brings an even faster pace to Web development. Java development just keeps getting better and better, don't you think?
Download
Resources
Learn
- Gaelyk: Learn more about this lightweight Groovy toolkit for Google App Engine for Java.
- Google App Engine: Visit home base for Google's App Engine.
- "Java development 2.0: Hello Google App Engine" (Andrew Glover, developerWorks, August 2009): Understand Java development 2.0 and how you can bring its concepts to fruition quickly with Google's App Engine for Java.
- Practically Groovy (Andrew Glover and Scott Davis, developerWorks): This series explores the practical uses of Groovy, helping you learn when and how to apply them successfully.
- Cloud Computing: Visit IBM® Cloud Computing Central for a wealth of cloud resources.
- Browse the technology bookstore for books on these and other technical topics.
- developerWorks Java technology zone: Find hundreds of articles about every aspect of Java programming.
Get products and technologies
- Gaelyk: Download the latest Gaelyk JAR.
- Groovy: Download Groovy today.
- The Google Plugin for Eclipse: Download the Eclipse plug-in for Google App Engine.
- developerWorks Cloud Computing Resource Center: Access IBM software products in the Amazon Elastic Compute Cloud (EC2) virtual environment. | http://www.ibm.com/developerworks/java/library/j-javadev2-6/ | CC-MAIN-2016-44 | refinedweb | 2,768 | 56.45 |
Type: Posts; User: Luis G
Why not print in one portion of the screen and input in another?
Look for conio.h or ncurses.h, dunno if there's a C++ equivalent.
I found out. The correct code is:
#ifdef _MSC_VER
friend CMatriz<TG> operator+(const TG &op1,const CMatriz<TG> &op2); // objeto TG + CMatriz
friend CMatriz<TG> operator+(const double...
Many thanks for the help, I've done what you said but it still gives the same errors.
This is how it looks now:
template<class TG> class CMatriz;
template<class TG> ostream& operator<<...
For the record, I solved the ostream << problem by adding:
template<class TG> class CMatriz;
template<class TG> ostream& operator<< (ostream & os, const CMatriz<TG> &op);
Before declaring...
First of all, this code does compile with g++ 3.3.5. But with g++ 4.0.2 it gives me a few errors. g++ enters the #else portion. The _MSC_VER is meant to be able to compile it in VC++ 5
#ifdef...
This guy presents a technical report and gives C++ code for a file compressor using arithmetic coding and an adaptive order-0 model
I know you're searching for C...
So basically I want to do the following operations:
CMatriz<sometype> matrix1;
sometype tg1;
matrix1+tg1;
matrix1+5.0;
However:
Too bad there's no way (or easy way) to keep the natural syntax I want and make it efficient.
I was thinking I should implement those operators just as you suggested.
Thanks again for the...
Thanks for the quick reply.
I'm researching as to how to do a copy constructor, it's been a while since I did some basic programming in C++ and I don't remember ever coming into that.
To make it...
The template declaration:
template<class TG> class CMatriz
{
public:
CMatriz(unsigned int j,unsigned int k=1);
~CMatriz();
CMatriz<TG> T(void);
void inserta(unsigned int j,unsigned int...
I've heard of an undelete tool for Linux, try searching freshmeat.net
Research about semaphores.
I've used them with parent and child process, not sure about their behaviour with threads.
semget(), semctl() and semfree() (not sure about the last one)
Ohh i found the error, i should not use "Connect()" method, i guess it should just be used for SOCK_STREAM.
I'm using CAsyncSocket btw :D
A bit of background of the program i'm doing:
My ISP...
I was about to post the same question.
I've done Create and Connect on both ends, but SendTo and ReceiveFrom, seem to not work.
Well, i'm doing the ReceiveFrom in the OnReceive() function, if i...
If the other peer is receiving the packets, then we have two possibilities:
- The other peer is not sending a response, firewalls tend to ignore incoming ICMP packets.
- You are not receiving...
Homework, huh? :D
Visual C++ as well as many other compilers have debugging tools, why don't you insert breakpoints or run it step by step so you can find what the problem is?
If you did a good...
ok, i might not tell the right answer, but just a small thought i had when i saw the coordinates.
why don't you change them to
(-1,0,1)-front left
(1,0,1)-front right
(-1,0,-1)-rear left...
ow, i was thinking something like "receive from", or force the assigning of a "well known" port to the connections.
Is there a way to make a socket connection (TCP) between to peers without using a listen port?
Right now i'm using CAsyncSocket, but i could change that.
Thanks in advance.
that code should work.
Just for the sake of it, try this piece of C code
#include <stdio.h>
int main()
I should have been more clear, 'cause "that looks like C to me" is a little vague, I should have said, that is C code.
You'd be surprised by the ammount of books and teachers that confuse C with...
i'm definitively not a big fan of C++, but i can tell you that you're not programming in C++, that looks like C to me.
Eli Gassert, those are not raw sockets. Proof:
sListen = socket(AF_INET, SOCK_STREAM, IPPROTO_IP);
SOCK_STREAM is TCP.
As far as i know there was no way to programm true raw sockets in...
You could try to open each port, on ports already in use the listen function should return an error code.
Other way would be to manually attempt connections to 127.0.0.1 (localhost) at port X, if...
Thanks a lot, right now i'm reading other questions of that FAQ, a couple of tests using that approach reduced the cpu utilization to 15% (instead of 100%), and most of that 15% is used by prog2.
... | http://forums.codeguru.com/search.php?s=c93b1cc7e4d5b485a3c34b3a1eae04fc&searchid=7208803 | CC-MAIN-2015-27 | refinedweb | 799 | 74.39 |
Request to allow refining the return type of a method in a subtype.
We may be able to accomodate this as a beneficial side effect of genericity
See
Done in the upcoming release.
I suggest that the JLS be modified to allow a method to be overridden with a different return type, provided the return type of
the overriding method is assignable to the return type of the method it is overriding. Specifically, section 8.4.6.3 would be
changed from
If a method declaration overrides or hides the declaration of another method, then a compile-time error occurs if they have
different return types or if one has a return type and the other is void.
to
If a method declaration overrides or hides the declaration of another method, then a compile-time error occurs if the return
type of the
overriding method is not assignable to the return type of the overriden method, or if one has a return type and the other is void.
That is, for instance, the method Object clone() from the class java.lang.Object could be overridden with, for instance
public ThisClass clone(){
return (ThisClass)super.clone();
}
because ThisClass is assignable to Object.
(Review ID: 32255)
======================================================================
Lots of casting. Ewwww!
======================================================================
Maybe as part of a generic types proposal we could deal with this. See comments.
xxxxx@xxxxx 1998-06-01
Done.
xxxxx@xxxxx 2004-08-30
There is a true lack of covariant return types.
This possibility should be added without delay in
Java. Typecasting is boring...
Please do not add C++ style code bloat generics to
deal with this. 'Beta' style inheritance generics
would be great. Covariant return types would fit
well with Beta style generics.
This feature MUST be added as soon as possible. Both practical and
theoretical arguments can be adduced (see A Theory of Objects -
Abaldi, Cardelli - Springer). For example, it could be useful to
create sub-interface of Enumeration associated to non-polymorphic
containers in large data structure libraries. This could be useful to
avoid at least one cast for each Enumeration cycle. The adapter
solution is both inelegant and impractical, because
1- an Enumeration can be argument to a polymorphic function
2- all the code written with generic old-style enumerations must be
rewritten.
The JDSL (Java Data Structure Library) Developers Group.
This request is a duplicate of 4150774. These
two requests should be combined along with their
votes.
There is another workaround, as described in
#4150774. Unfortunately, it is even uglier then
casts. Rather then use a return value, throw an
exception.
Very, very ugly!!! Which is one of the best
arguments why this should be supported by the
language.
RFE 4106143 is similar to this one and has 11 votes. Maybe it should be closed
as duplicated of this one.
Furthermore, covariant return types are explicitly supported by the JVM for
reasons of binary compatibility. (Changing the return type of an overriding
method to a subtype and recompiling does not break the binaries of its
supertypes.)
What is the argument against covariant return types? It increases flexibility
without introducing new syntax or requiring VM spec modifications. It seems
like a no-brainer.
Yummy. This will require a rewrite of every JVM
and classloader on the planet. It's an ideal
opportunity to use that "required JVM version"
thing that's new to the compiler.
As well as an overriding function being able to
narrow it's return type, it also ought to be able
to widen its parameters.
Genericity should solve the problem, but even without it, this needs addressed.
There should also be covariant throw clauses.
The problem is worse than just casting. Sometimes it breaks would-be good
code.
For example:
public interface View
{
View getParent();
}
public class ComponentView
extends Component
implements View
{
public ComponentView getParent()
{
return (ComponentView)super.getParent();
}
}
This would be fine as long as the parent was a ComponentView.
At present in Java, implement the interface above is strictly illegal.
To amplify my previous comment,
This ought to be OK in the language
class X {
Integer a(Integer b) throws Ex1, Ex2;
}
class Y extends X {
PositiveInteger a(Number b) throws Ex1;
}
Any possible call to X.a() can be handled by
the overriding function Y.a()
If you do this
X foo = new Y();
then foo.a() will always be ok. However, if you
then go
Y bar = (Y) foo;
You get access to the more restrictive return and
the less restrictive argument that comes of
knowing that foo is actually an instance of Y,
without having to cast bar.a() every time you
call it. Note also that the broadening of the
argument type is not possible with java as it now
stands, unless you use a "delegation" function to
handle it.
covariance is not without its problems (in Eiffel
it makes the language type un-safe).
According Sun Engineer, polymorphism is "perfectly type safe". If a
method return a Number, an overrided method may only change the return type for
a Integer, a Float or stuff like that (which are Number). Please see bug
#4106143 for details.
I suppose covariance of argument types would conflict
somewhat with method overloading...
A POSSIBLE WORK AROUND?
I don't know if this works consistantly
across all compilers and JVMs. The second
argument of the self method stops my compiler
from complaining - effectively tricking the
compiler/JVM to perform covariance (or
something like it) and serves no other purpose.
Please tell me if this works elsewhere too.
class AA
{
public AA self(int i, AA a)
{
return this;
}
public static void main(String args[])
{
// AA.self(int, AA) returns AA and
// AA does not have a test() method
AA a = new AA().self(0, null);
// We know this simulated covariance
// worked because test() is no a method
// of AA, yet it can be called from
// the return value of self()
BB b = new BB().self(0, null).test();
}
}
class BB extends AA
{
public BB self(int i, BB b)
{
return this;
}
public BB test()
{
System.out.println("Hello World!");
return this;
}
}
Unfortunatly, the Hoggy's code (from the previous comment) is not a work
around.
It doesn't override the "self" method; it just overload it. sefl(int,
AA) and self(int,BB)
are two independants methods. The code "AA bb=new BB(); bb.self(int,
null)" will
never call "BB.self(int,BB)". In Java, the method's signatures need
to be absolutly
identical in order to override a method.
I disagree that a JVM change would be necessary to support
covariant return types.
A method with a covariant return type could be compiled as
if it had the same return type as the method it's
overloading. Then, when that method is called, the compiler
inserts a cast if the method is called through a reference
to the class that contains the covariant return type
method.
To give an example, let's say I have a class MyClass that
overrides the clone() method to return a MyClass reference.
This clone() method would return an Object reference, as far
as the JVM is concerned, because it overrides Object's
clone() method, which returns an Object. Thus, there is no
incompatability with old JVMs.
If I have the code
Object o = new MyClass();
Object s = o.clone()
The returned Object reference would *not* be cast to a
MyClass, because the o reference could point to any kind
of Object. The fact that o points to a MyClass object is
ignored.
But in the following code:
MyClass m = new MyClass();
MyClass c = m.clone();
The compiler would compile the second line as:
MyClass c = (MyClass) m.clone();
The cast is inserted because I'm calling the clone() method
with a MyClass reference, and MyClass declares clone() as
returning a MyClass reference.
Java already has covariance of throws clauses and
accessibility. Adding covariance of return type seems easy
and makes the language *more* type-safe because it
reduces the number of casts needed, and these casts can
always throw ClassCastException.
The claims that the JVM already supports covariant return
types and that it requires no JVMS changes do not hold. An
invokevirtual instruction explicitly states the name and
descriptor (indicating parameter types _and_ return type) of
the method to be invoked. According to the JVMS, a method
with matching name and descriptor is searched for during
dynamic method lookup for invokevirtual. In other words, a
method with differing return type would not be considered a
candidate for execution by a given invokevirtual
instruction.
Note: I'm not saying that allowing covariant return types
for overriding methods would be unsound or cannot be
supported; it just doesn't fit with the current JVMS (2nd
ed.).
In reply to Schaepel's April 28 message: That isn't
covariance, that's just hiding the ugly cast by making the
compiler do it for you. The case is still there and still
exacts a run-time overhead.
What are "'Beta' style inheritance generics"?
Nooo...the *cast* is still there! Stupid thing changed my
What is Eiffel?
What does it matter if the cast is "still there"? This way
of implementing covariant return types is just like the way
generics are being added to Java: containers still contain
Object references, but the compiler hides the ugly casts
from you when you retrieve them.
The JVM will not support generics, but Java will
support generics at the source code level. Likewise, with
the method I proposed, the JVM will not support covariant
return types, but Java will support it at the source code
level. Isn't that what really matters, anyway?
It may be true that there's another way to implement
covariant return types that's faster, but as far as I can
tell, speed is the only disadvantage to the casting method.
If the casting method doesn't "really" support covariance,
then do you also think that Java will not "really" support
generics, since that method uses casting as well?
Request to allow addition of a return type to a method in a subtype.
I suggest that if the overridden has return type void,
the overriding method is allowed to define a different return type.
Reason:
The method can still be called without a return value.
While covariance (as requested in this RFE) is not supported
by the JVM/ClassLoader, there is no sensible reason not to
do this as it is clearly a completely safe operation.
(Covariance is more troublesome when it comes to assignable
things like array indices or C++ references - in fact,
anything that can go on the LHS of an assignment - but we're
not after that here.) Because it is safe operation, it
should not require a cast; casts should be regarded as
indications that you're doing something ugly and which is
forced upon you by the horrors of working with real-world
problems, and not as something you should be using for
everyday programming. Casts are where you are fighting
against the language, and not working with it. (Which is
why I support both this RFE and the generics one; because
they remove casts.)
That cast removal also improves the performance of Java
programs is doubly a good thing...
I just discovered that the GJ compiler implements covariance
in a way that does not require a change in the JVM, and also
does not require a runtime cast. It depends on the fact that
the JVM allows two methods with identical names and
argument to have different return types (although the Java
language does not allow this type of overloading). You can
read about it by going to
and reading the tutorial.
Could this also apply to widening type signatures when
implementing abstract methods? For example:
class SuperA { ... }
class SubA extends SuperA { ... }
abstract class SuperB {
abstract void foo(SubA arg);
}
class SubB extends SuperB {
void foo(SuperA arg) { ... }
}
As written, SubB will not compile, because it does not
implement the abstract method with the same type signature
as is in SuperB. However, if SubB were not extending
SuperB, then passing a SubA to the method foo would be
legal, as the compiler notices it can widen SubA to the
specified SuperA. It is annoying to make this case work
with an extra overloaded method:
class SubB extends SuperB {
void foo(SuperA arg) { /* handle the generic case */ }
void foo(SubA arg) { foo((SuperA)arg); } // satisfy the
compiler
}
In general, each method should accept as parameters the
widest type of objects it can handle, and return the
narrowest type it can, so that there is less typecasting.
Eiffel supports this feature and it sure is helpful.
OOSC 2 (Bertrand Meyer) explains how this should work
in explicit detail.
in reply to schapel (Fri May 05 06:56:04 PDT 2000),
inserting a cast in someting to avoid, because it generates
a runtime check and a performance hit.
It's very very simple. Returning a narrower type is safe. I
want the compiler and classloader to be relaxed about this,
so that I don't have to cast the result of the clone()
method etc.
As far as I know, there are three options available for
implementing covariant return types in Java: add methods
that are overloaded on return type (as GJ does), cast the
returned reference (as I suggest), or make a change to the
JVM.
I've never seen a proposal for a change to the JVM that
would allow this feature. So, we're left with either an
additional cast or a method call, each of which has a
run-time penalty.
If you'd like to propose a way of implementing this feature
without any run-time overhead, you're more than welcome to
do so. But the disadvantage of a change to the JVM is that
covariant return types would not be available on older JVMs.
One of the most widely-criticized aspects of
the C language was always the reliance on void*
pointers and the casting that this leads to.
"Object" serves the same purpose in Java that
void* serves in C, and over-reliance leads to
excessive casting, which reduces overall code
quality.
Permitting covariant return types would dramatically
reduce the amount of casting, even without a template
or generic types system. It's a minor language change
which would dramatically improve the language.
> We may be able to accomodate this as a beneficial side
effect of genericity
No. Don't give me complicated solution for that. The simple
solution (allow covariant return type) will solve a big
piece of problem. Just relax the compiler to do the safe
works. Even better, it doesn't break backward compatiblity.
please relieve us from many of castings.
Also, no reason for convariant return type doesn't co-exist
with generic type. And, I don't need, (even don't want)
generic type. It is very very painful and unsafe to adapt
any "object factory" and "factory method" pattern without
covariant return type.
In short, please do it now. Don't wait please. I waited
long enough. please........
Sun, just do it. You know you need to do it. Its a backwards compatible change, and it improves code
quality dramatically. What possible reason can you give for not supporting this in your next release?
I agree with "dleuck". Sooner the better. It is probably
the most important single feature currently lacking from
the language (after Swing performance :-) )
The generic types proposal URL at the top of this page is broken.
An excellent idea that would solve design problems I run into almost daily. I
hope this is added to Java ASAP.
Just a thought: would this allow constructor inheritance to
work more tidily?
Hmmm... "constructor inheritance"? I'm not sure what that
is, because constructors are not inherited in Java.
Anyway, I'm all for this RFE, but I think "just do it" is
not the right attitude for adding this change to the Java
language. There are at least two ways of supporting
covariant return types, and there are problems with each
way.
As part of GJ
there's a proposal for adding covariant return types that
I believe could be used independently of the "generic types"
features of GJ. However, as the authors of GJ point out,
the reflection API is underspecified and would have to be
modified in order to work with GJ. Even if the reflection
API is updated, think of all the code that uses the
reflection API that assumes overriding methods have the same
return type the overridden method. With this proposal, there
is some Java code that will break.
The other proposal is one I came up with that simply casts
the returned reference. This approach is compatible with
the current reflection API, and thus wouldn't break any
existing code. But if generic types are added to Java
later, there could be incompatibilities at that time.
If you're eager for covariant return types in Java, you can
use the GJ compiler today. It's available for free at the
above URL.
Just do it!
I would luurve to be able tpo implement a
FooList extends ArrayList {
put(Object o) {
if(!(o instanceof Foo)) throw IDontThinkSoException();
super.put(o);
Foo get(int i) {
return (Foo) get(i);
}
}
At the moment, you just can't. I don't know what generic
types are and I suspect I don't need them. And I prefer not
to have hidden casts in the compiled code.
Is java going to fossilise into a mess of bug-compatible
missing features? Is it going to bloat? Just change the JLS
and the JVM spec on this one tiny tiny change.
We would like to implement a class hierarchy with EJBs.
However, we are left with lots of();
}
etc., we plan to have at least several hundred EJB services
and this is untenable. We want to have a base EJB with
derived EJBs with a shared interface; however, we need this
feature enacted to do this. Otherwise, the create() method
(required to be defined in the Home interface) cannot
be overridden and we cannot call create() polymorphically.
Adding covariance of return type to the JVM is absolutely
not a tiny change! If you disagree, please post a proposal
for changes to be made to the JVM to allow this feature.
Keep in mind that JVM byte code allows methods to have
identical names and arguments, but different return types,
and that Java is not the only language that is compiled to
byte codes. Any change should be compatible with all older
JVMs. Specify the exact behavior of the invokevirtual,
invokeinterface, and invokespecial instructions. Discuss
the interaction with binary compatibility (i.e. in what
situations is changing the return type of a method a binary
compatibile change?). Finally, convince JVM implementors
that adding covariant behavior would not impact the speed
of these instructions.
Even if this proposal does turn out to be simple, it would
still be incompatible with all current JVMs! So far, there
have not been any changes to the JVM that haven't also been
tied to changes in the API.
If you need covariance of return types, don't hold your
breath for Sun to include it. Simply download the free GJ
compiler, and you can use the feature today with all JVMs!
A case can be made for narrowing the return type - but
widening would defeat the behavior of the compiler to
detect contract violations. E.G.,
class SuperA { ... }
class SubA extends SuperA { ... }
abstract class SuperB {
abstract SubA foo();
}
class SubB extends SuperB {
SuperA foo() { ... }
}
Why exactly is SubB extending SuperB? If this is the
entire declaration, then SubB is *not* a SuperB, it merely
has a method of the same name. Now the compiler has no way
to guarantee that SubB conforms to the contract of SuperB.
What happens here:
void whatever(SuberB b)
{
SubA a = b.foo();
}
This code will break sometimes - whenever the passed-in
object is actually a SubB. The Java philosophy is that
subclasses should *never* break the interface of a
superclass/interface.
Code like:();
}
is just plain ugly and if this is what your design forces
you to then it is quite frankly no good. In my experience
I have yet to be forced to code this way.
Here is a simple workaround which is compatible and follows
a pattern (or idiom) established by StringTokenizer:
'create a new method which specifies the different return
type and is available only in the derived class.'
E.G.,
interface Enumeration {
Object nextElement();
}
class StringTokenizer implements Enumeration {
Object nextElement() { return nextToken(); }
String nextToken() { return ...; }
}
The assumption is that you only need the services of the
derived type if you know you have one, as in:
StringTokenizer st = new StringTokenizer();
String s = st.nextToken();
Where the new method is easily accessible. In this case:
Ennumeration enu = new StringTokenizer();
String val = ( (StringTokenizer) enu).nextToken();
Is evidence of a worse design than one that requires
casting of return types.
One final word - type casting is not neccessarily a result
of language limitations, sometimes (usually) it exposes
design flaws (especially if it happens alot).
Allowing an int return type to override a long would be much more difficult to implement than allowing a Spartan to override an Apple. I suggest this just be done for Objects,
not primitives.
I completely disagree with that. The great benefit of Java
over Smalltalk and other languages with weak typing is
STRONG typing which allows to elliminate a high percentage
of errors in compile time.
If you are bored from type casting - you don't know Java or
have no taste - use interfaces instead of types and never
cast types. In ideal world you should never put class name
in method declaration - instead you use interfaces
everywhere, and real classes only when you create instances.
Don't destroy beauty of Java - interfaces are excellent!
Great advantage over Smalltalk!
MaximSenin, what are you wibbling about?
If I've got an object of type Foo and I want to clone it,
the new object's return type is Object, and I have to cast
it to get it to be a Foo, despite the fact that everyone
knows cloning returns the same type of object. There are a
number of other similar problems strewn throughout the
standard libraries. Using interfaces everywhere does not
help; it is completely orthogonal to the problem.
If it weren't for the fact that I know academics are more
grounded than you, I'd tell you to go back in your ivory
tower and not come hence until you've gained a clue about
real programs...
And it's acedemics who gave us the GJ language and compiler,
which support covariance of return type.
At you can find
a compiler that implements this feature (as well as generic
types, of course!) with current JVMs. If you're tired of
casting, you might give it a try.
This feature would be a lifesaver in countless cases, but I
must point out one problem. I was reading a native library
tutorial the other day and remember seeing a reference to
the way java methods are called from native code - with the
return type included in the signature (which is passed as a
string to a java "interface" function in C). I suppose this
would not hurt classes that are already written and will not
be changed, but it could introduce complications in case
that the C code uses a subtype of a class to call a method
that, although it returns a subtype of the same method in
its superclass, has a different signature.
Somebody please correct me if I am dead wrong here (as I
have never actually written any sort of native library on my
own). I wish I hadn't thought of this potential problem,
because this would be a *wonderful* feature to have.
Relax. There's nothing about the JVM or native method calls
that makes covariance of return type impossible or even hard
to implement. Java bytecodes also include the return type in
method calls, and as I so often point out, the GJ compiler
implements covariance of return type with current and older
JVMs. If you haven't already, go to
and download the GJ compiler and documentation for further
details. If nothing else, it makes a great additional free
compiler. I always run my production code through javac,
oldjavac, jikes, and gjc to ensure that I haven't taken
advantage of bugs in any compiler or gray areas of the
Java language.
The easy way round is to generate a dummy method in the
subclass (B) that has the same return type as the superclass
(A) and which just passes everything on to the real method
and just returns the result after widening its type. (For
sanity, you could ask the compiler to ensure that any
subsubclasses (C, etc.) overriding the method must do so by
being at least as restrictive as the method in the subclass
(B).)
I'm not completely familiar with the internals of Generic
Java. But it seems to me that one of the main reasons that
a language would support covariant return types and
generics is to avoid the cast at all -- because of the
overhead involved. A cast from what I understand is very
expensive.
Does Generic Java still do these casts when it compiles the
code -- effectively eliminating any performance advantage,
or does it actually create macro/template classes which
return the truly covariant type? Does anyone know?
It just seems like everyone is solely concentrating on the
advantage of 'not having to cast within your code', when it
seems to me that the other huge advantage for a covariant
override is to speed up/optimize your code as well.
Thanks for any comments.
-- Rick
One way to think about this proposed feature is that it allows casts to be moved from the method calls to
the method body.
public Class Rabbit implements Cloneable {
public Rabbit Clone() {
return (Rabbit)super.clone(); // cast in method body--callers need not cast the return type
} }
public class RabbitVector extends java.util.Vector {
public Rabbit firstElement() {
return (Rabbit)super.firstElement(); // ditto
} }
This seems like a win because casts are ugly and now there's only one per method instead of one per
method-call. So all of the many <code>Rabbit r = (Rabbit)v.firstElement();</code> casts in the code can be
changed to <code>Rabbit r = rv.firstElement();</code>. (Note: This is not a performance win, there's still
the same number of casts at runtime, they've just been factored-out.)
I find that most of the time I'm using a Vector (or any Collection), I populate it homogeneously. That is, all
the objects I put in it are of the same type, or at least have a common supertype that is not Object. So if
this feature were implemented, I would gladly write class RabbitVector (heck, it's only 4 lines) and use that
instead of a java.util.Vector. It just seems cleaner.
But it's not that simple. If Marshmallow is a subclass of GroceryItem, it's dangerous to think of
BagOfMarshmallow as a subclass of BagOfGroceryItem because then a new Cabbage() could be add()ed to
an instance of BagOfMarshmallow, in which case it wouldn't really be a bag of marshmallows anymore. An
example using RabbitVector would be:
RabbitVector rv = new RabbitVector();
rv.add(System.out); // can add() any Object, not just rabbits
Rabbit r = rv.firstElement(); // will cause a ClassCastException at runtime
While I agree that allowing covariant return types in type-safe in theory, I also think the most common
place in which they would be used would be with Collection types (such as RabbitVector), and would
therefore be encouraging quasi-type-unsafe design practices. Comments?
RabbitVector could be "improved" by overriding the add(o), add(n, o), addElement(o), insertElementAt(o, n),
set(n, o), and setElementAt(o, n) methods to not allow non-Rabbit objects to be inserted. (Take a look at
what pmurray wrote on Nov/12/2000 to see how to do this.) This is pretty ugly. First, that's a lot of
methods to have to override, each one with a instanceOf operation, which in some ways is as bad as a
cast. Second, that leaves the addAll(c), addAll(n, c), and copyInto(a) methods, which could be much
harder to deal with.
I'm not necessarily against this RFE, but I'm against hurrying it. Better I think to think everything through.
I'm not sure which of the three proposed implementations I like best:
1. Alter the JVM spec: Older VMs wouldn't be able to run new code, so shouldn't be done lightly.
2. Compiler generates implicit casts: No runtime performance improvement, which is too bad, though I think
getting rid of the actual casts in the source code is more important.
3. Generate an extra method for each return type, a la GJ: I haven't taken a look at GJ, but the idea rubs
me the wrong way. (How large is each dup method?)
Maybe a more modest approach would be better. Maybe something like:
4. Augment the JLS to include a new cast-equals operator: A symbol would have to be chosen, but I'll
borrow Pascal's := for now. <code>x := y;</code> would be syntactic sugar for <code>x = (typeof
x)y;</code>. (Not C's typeof operator, but the actual compile-time type of x.)
This doesn't attempt to allow covariance or improve performance. All it does is make the source code look
slightly better by removing explicit casts if they precede an assignment.
This would be a very good update. I wonder if Sun would be
able to handle it. Do they still have the people who
created Java?
You only need a single dup method for each method in the
subclass that has a return type smaller than the method in
the superclass, and all that method does is pass in the args
to the smaller method and expand the type and pass back the
result.
I don't like that ':=' as it encourages sloppy thinking.
When you are narrowing types, you should be aware that you
are doing this. It just shouldn't be necessary to narrow
types quite as often in Java as is currently the case, and
return-type covariance will go a long way towards fixing
this. (That it allows things like your RabbitVector, well,
it is unavoidable; you can get yourself in the same mess now
except for having to have a cast on the caller's side as
well. RTcV opens no holes in the typesystem; it just lets
you express things that the programmer knew and assumed
already, like the fact that clone() copies an object...)
pmuarray also suggests widening the argument types, I
believe this is called contravariance of argument types.
Method overloading I think interferes with this and makes
it less necessary.
Correct me if I am wrong, but the JVM has
method "overloading" on the return types which would cause
similar interference but the language specs never allow us
to use the "overloaded" return types. Thus implementing
covariant return types at worst would require a recompile.
The covariant types would not really help with
the "RabbitVector" problem but would help with
a "RabbitIterator". I'm personally tired of writing the
following Javadoc: "This method returns an Iterator where
every element is of type Foo."
I think that we got covariant returns as part of generics spec. I would expect this bug to get closed soon.
There's a prototype open-source Java compiler that supports
covariance of return type available at
The run-time system (jdk1.1.8) already supports this. Compile these files:
public class Base {
}
public class Derived extends Base {
}
public class BaseReturner {
public Base getValue() {
return new Derived();
}
}
public class DerivedReturner extends BaseReturner {
public Base getValue() {
return new Derived();
}
}
Make a copy of 'BaseReturner.class'. Now change the return type of 'getValue()' of both 'BaseReturner' and
'DerivedReturner' to 'Derived'. Compile 'BaseReturner.java' and 'DerivedReturner.java'. Restore the copy of
'BaseReturner.class'. Then compile the following test program:
public class CovarianceTest {
public static void main(String[] args) {
BaseReturner br;
DerivedReturner dr;
Base b;
Derived d;
dr = new DerivedReturner();
br = dr;
d = dr.getValue();
b = br.getValue();
}
}
Supporting contravariance of argument type would change many
existing overloaded methods into overriding methods. This
change would cause millions of lines of Java code to break.
I don't see a way of adding contravariance of arguments to
Java in a backwards compatible way. For this reason, I don't
think this feature will ever be added to the Java language.
In contrast, adding covariance of return type does not break
any existing Java code and is scheduled to be added to JDK
1.5, aka Tiger.
I've been thinking about contravariance for arguments, but I don't think there is an unambiguous strategy for
choosing which method overrides the base class' method. Take a look at these types:
interface Base1 {
}
class Base 2 {
}
class Derived extends Base2 implements Base1 {
}
class DerivedUser {
void doIt(Derived d) {
System.out.println("Doing it on derived");
}
}
class BaseUser extends DerivedUser {
void doIt(Base1 b1) {
System.out.println("Doing it on base 1");
}
void doIt(Base2 b2) {
System.out.println("Doing it on base 2");
}
}
Both 'doIt' methods in 'BaseUser' are contravariant 'doIt' in 'DerivedUser'. Which one should be executed
when someone invokes 'doIt' on a 'BaseUser' reference to an actual 'DerivedUser'?
One option is to chose 'doIt(Base2 b2)' because this is the class inheritance path and this must be single, so
ambiguity can not occur.
If you have any thoughts on the subject, please let me know.
I just had a look at the generic type compiler and this is
how future code would look like:
"public class IdentityHashMap<K,V>
extends AbstractMap<A,B>
implements Map<K,V>"
I can understand that the proposal guys rely on some
template like structures to make things type-safe, but I
always hated templates in C++ and don't want them in Java.
Well.. probably I start playing around with the generic
compiler and hope that I get used to the new code style
easily. But from the first glance I would reject this
covariant types add-on.
In response to jstuyts trick-workaround by modifying the
superclass (June 10, 2001) without recompiling the narrowed
base class. It fails being truly covariant when
considering the following case:
BaseReturner returner = new DerivedReturner();
Derived d = returner.getValue();
would throw a compile time error saying an explicit cast
was required. what the proposed run-time example was doing
in fact was creating a subclass with an overloaded return
type rather than a covariant one.
Possible workaround example:
public class RabbitIterator implements Iterator {
public Rabbit nextRabbit() {...}
public Object next() {return nextRabbit();}
}
Code which wishes to use the covariance of a "Rabbit
iterator" would then use the nextRabbit() method. Not
ideal but it seems to work.
I have had a bit of a looksee at the generic stuff, and
there are two problems.
Firstly, it looks like it is a compile solution, that
probably generates bytecodes with bunches of casting. This
is a performance hit.
More impotantly - genericity must be built into the base
class. You can't simply override a method and declare the
return type as being narrower.
And, it's really quite a heavyweight solution for what we
are trying to do here - real language bloat. All we want is
to be abe to declare a MyClassCollection, which overrides
iterator() to return a MyClassIterator, which overrides next
() to return a MyClass.
I'm sure there's some deep computer-science reason for it,
but I cant for the life of me work out why this would break
the type-safety of the language.
Return-type-narrowing needs a compiler change but can be
done without any JVM changes. You need a compiler change
because for each method that you narrow the return type for,
you need an adaptor method to widen it so that people
assuming you've got the superclass can still find the
method. The compiler will also need to be smarter about
detecting existing narrowings (obviously!) You do not need
a JVM change because methods are currently looked up by
return type as well; this is probably why narrowing is not
currently supported, but it doesn't get in the way.
I *think* that only the class that does the narrowing will
need an adaptor method in it, and subclasses will be able to
use the superclass's adaptor (since they will need to be at
least as narrow, for sanity's sake if nothing else!)
There is, of course, some issue with documentation of this
narrowing process, but that should be resolvable.
This enhancement will help greatly, moreover it would fully
support "substitution by subtype" principle. Typecasting is
not an elegant solution. I think it should implemented as
soon as possible.
Hrm. Why are people still putting all of their bug votes on
this issue, when it (as part of the generic types proposal)
is an active Java Specification Request, it's already had a
public specification review, and it's been stated that it's
going to happen quite soon (e.g. JDK 1.5)? Your bug votes
would be doing more good if they were moved to some other
bug proposal that is less certain to get fixed, so that
other proposals get brought to the attention of Sun.
Personally, I'd like to see enums (actually, strongly-typed
integers) and 'const' added to the language. You may have
some other requested change or bug fix that is nearer and
dearer to your heart. I suggest moving your bug votes to
that, instead of to here.
"And, it's really quite a heavyweight solution for what we
are trying to do here - real language bloat." -- pmurray
WED AUG 29 10:45 P.M. 2001
I totally agree with you, pmurray. I want a simply
solution, not a bloat. Generics type is an overkill, and I
am only interested in covariant return type.
If there is "vote againts", all my three votes will go
*against* having generics type in Java.
All my votes go to this REF currently.
I love to have covariant return type in Java. However, I
would rather that Java never supports it, then using
generic type to solve my problem.
Good point, Ixchel!
Removed.
I really don't get it, ThomasYip. What do you have so badly
against generics, and what does it have to do with
covariant return types?
If Java does get them both in the same release, as
expected, there's no reason to imagine that you'll have to
use generics in order to have covariant returns. Even if
you'd rather tear your eyes out than use generics, it has
no impact on this RFE.
I would like to ask if anyone is willing, to maybe shift one
or two votes to 4466510 because although the idea of
generics and covariant return types is great, it isn't
exactly something that effects every type of application
written (although i'm sure you could use that in any type of
application). 4466510 is in reference to memory footprint,
and being that all applications use the JVM and consume
memory, perhaps some of you could find it in your heart to
transfer a few votes to this (arguably) more pressing problem.
Thank you.
-Chris
Just cast the darn object you rebel scum. I want to vote
_against_ this.
(First time poster, go easy :o)
Type safe is one thing, complicating the design is entirely
another. What happens to subclasses of that class? What
should they return?
e.g.
class Heaven{
Heaven returnMe(){return new Heaven;}
}
class World extends Heaven{
World returnMe(){return new World();}
}
class Hell extends World{
???? returnMe(){return new ????();}
}
Solution 1: Allow superclass to be returned
i.e. ??? = "Heaven"
But now (of course) someone referencing a world component
that is actually the subtype Hell, may not get back a World
object. Cannot allow this, since it is illegal.
i.e. World w = new Hell();
w = w.returnMe();
Solution 2: Only allow new restricted type. (the obvious
choice)
Now the actual implementation of that method is potentially
hidden in ALL the superclasses of this object. While this
is not a paradox, it confuses things from a design point of
view.
To find out what the current implementation of a method are
on the object, you have to check each superclass for the
closest return-type restricition.
Also, if a subtype class now wants to return the superclass
component and can't, because of a return-type restriction,
you are stumped. The alternative now is to go back and
remove this restriction, editing all referring code to the
casted type. Just another design choice that has to be made
before implementation, with the cost in man-hours being the
penalty.
A subtle problem, to be sure, but the benefits are only to
save a few casts in your code? Is it worth it?
(Let's not even mention the changes to all the CASE tools
etc)
I realise this: assuming you don't find it in the immediate
superclass, you must check up the heirarchy until you do.
...which still means you have to search up the tree to find
the closest one, meaning you cannot be sure anymore that
simply because you see that a superclasses member returns a
particular type, that your inherited member can.
Again, a subtle and small problem, with a simple solution,
but an annoying one nonetheless.
As to it being the same as today, it is most definitely
not.
E.g. (usual example with easy solution)
Today if I have a Component, I know that any subclass of
Component returns a Dimension Object from the getSize()
method. So my Component, no matter what/where it is, can
return a Dimension for getSize() and be happy.
Now What if some bright spark has written a Component (e.g.
My3DComponent) that returns a subclass of Dimension that is
a 3D dimension (with a depth also - called Dimension3D),
then restricts the return type of getSize() to this new
subclass..
The difference is subtle and easily solvable, but annoying.
E.g. (without easy solution):
Complicate the issue further, what if this new Dimension3D
and Component3D subtype are in another package? And what if
the Dimension3D has a protected constructor and is a final
class?
Therefore: I have access to subclass the Component3D, but
not to the return my own getSize() because I do not have
access to create a Dimension3D object.
In current Java, it still works, because I simply return
the supertype - Dimension.
In the new version, I am forced to either:
1) Make my component part of this package or,
2) Try and use the superclass's getSize() method to return
the size I want - which is probably incorrect, so not
really a solution.
Solution 1) may not really be possible wince I want to use
protected members from my own package.
Again, a subtle problem that wont affect most people, but
it is still there.
"To find out what the current implementation of a method are
on the object, you have to check each superclass for the
closest return-type restricition."
No, you only have to check the closest superclass where the
method is declared. This is always the most restrictive
return type. Actually this is exactly the same as today, no
additional restrictions are made.
ok...in my proposed scenario you are aware of the correct
inheritance but cannot comply with the creation of the new,
restricted return type because it has been made a package-
access class.
Incorrect inheritance, along with other bad programming
techniques, will always be a feature of code - no matter
what you do.
e.g.
If you allow restricted the return types, you will have
people over-using this feature to save themselves a few
casts. (Leading to design issues later.)
I have also ignored the simple fact that this small
conceptual change will lead to rather large (or at least
fundamental) changes to design tools, IDES etc.
Actually I dont think it's a problem at all. If you are
inheriting from a class you should be aware of the methods
you are inheriting otherwise you are in deep water. The
easiest way to check which methods you inherit is to walk up
(not down) the inheritance tree. Exactly like today.
Incorrect inheritance is the root of much evil. Composition
is often a better choice.
Actually
World w = new Hell();
w = w.returnMe();
Is perfectly legal in Java and would compile and run just
fine if you declared the returnMe() as:
public Heaven returnMe()
{
return this.getClass().newInstance();
}
in your Heaven class.
Then you could do:
Hell hell = new Hell();
World w1;
Heaven h1 = w1 = hell.returnMe(); (note that you don't even
have to cast here).
But you've missed the point of this whole thread (and by
posting this so do I)...
Otherwise the covariant return types will be the second best
thing that will happen to Java after the generics become
part of the language.
I haven't missed the point. (which is actually quite a
simple one so I would have to be pretty stupid!)
I was just pointing out this suggestion IS changing the
language, not simply allowing some "extra feature" that
does not effect the way the language works at all. (this
has become one of the premises of the argument, if you
remember)
I also realise that making the class a public one would fix
the problem - although it is my experience that these sorts
of classes usually tend to be inner classes or protected
classes, not designed to be used outside of the package.
However, this point is irrelavent, since it was merely an
EXAMPLE of how situations could arise that change the way
the language is used.
Covarientce would also introduce the problem of "over-
restriction", in which programmers start setting arbitary
return type restrictions to save a few casts, with this
having repercussions later on.
I am not saying this is a bad idea oveall, actually I would
use it if available myself. However, it is not a silver
bullet with no side effects as some people have been trying
to say. If a change is made, let it be made on facts, not
fantasy.
While the proposd change is subtle and wont bring anyone's
project to a grinding halt, is covarience going to save
anything more than some casting? Is this worth the
compounded effort to implement?
I would disagree with this.
Covariance is a wonderful feature in a language purist
sense.
In practical terms the only real benefits in Java would be
less castes to type and execute. Given the larger issues
on this enhancement list (e.g. 4466510) and ongoing quality
of implementation issues (e.g. HTTP client library issues,
quality of Java Plug-In delivery, etc, etc) I would put
such an "ivory tower" request at the bottom of the list!!!
I think what it comes down to is that what an object
actually is and what the compiler thinks it is are very
seperate entities. Casting, despite how verbose it is
and how automatic it could be in some situations, is
provided by the programmer to concretely let the compiler
know what it can and cannot do with an object.
I agree with all of you who've said they would prefer
a bit of casting as opposed to negotiating the logistics
of covariant return types.
I think SUN engineers knew what they were doing when they
drafted the language specifications and made methods to be
functions of their inputs only and not as functions of their
output containers.
Such is the price of late binding.
P.S. For 99% of applications, casting overhead is the least
of your problems (unless, of course, you're casting several
billion objects per second.)
I can't believe some of you people. This really isn't that
hard.
> Solution 1: Allow superclass to be returned
> i.e. ??? = "Heaven"
No, it's overriding a method that returns World, so it must
return some form of World. Either it returns World like its
parent, or it returns Hell which is a World. In either
case, client code knows that it will be getting a World.
Unless you're arguing that a Hell isn't a Heaven, in which
case it's your class hierarchy that's at fault.
> Now the actual implementation of that method is
potentially
> hidden in ALL the superclasses of this object. While this
> is not a paradox, it confuses things from a design point
of
> view.
No, it simplifies things from a design point of view. The
whole point of object oriented programming is that
implementations are hidden. You don't know the internals of
an object, you just know its interface.
> To find out what the current implementation of a method
are
> on the object, you have to check each superclass for the
> closest return-type restricition.
No, you trust the return type that you are told. The return
type isn't free, it's covariant. A World is a World,
whether it's a Hell or not. The return type of the type
you believe it is will always be the most restricted return
type you can trust.
>.
Correct. A 3D component should always have a 3D size. If
you return a 2D size, as is currently allowed, then you are
making a mistake. With covariance you are forced to only
do the thing that makes sense, returning a 3D size for your
3D component.
> And what if the Dimension3D has a protected
> constructor and is a final class?
Then that is the developer of Dimension3D's way of
deliberately preventing you from making one. It's not an
accidental error, it's a deliberate restriction.
> In practical terms the only real benefits in Java would
be
> less castes to type and execute.
My project would be significantly aided by the use of
covariance. I have a superclass (with company-sensitive
stuff hidden, of course):
class Doodad {
Doodad modifyMe() { ... }
}
And lots of subclasses that look like:
class Doodad3 extends Doodad {
Doodad3 modifyMe() { ... }
}
And I need the option to call both:
Doodad3 d3 = doodad3.modifyMe();
Doodad d = doodad.modifyMe();
At present, I have to use a method with a different name
like superModifyMe(); See how annoying that is? And
there's lots more like it.
Shrik, you have missed the point entirely - it is a theoretical foray into various scenarios that could arise from this change. I am trying to address three related points that were brought up:
1) The change DOES effect the language in a fundamental and there ARE differences in implementation. These are subtle, but they are still there.
2) This change could create annoying and subtle situations that are not noticed till much later in the design process.
3) "Over-restricting" return types will auite probably become a "new" programming antipattern, to replace the one this solution solves.
In reference to your reply:
>No, it's overriding a method that returns World....
The first solution was set up as a "straw man" to illustrate a non-viable alternative. Of course I know it is not a valid option!
> The whole point of object oriented programming is that implementations are hidden.
Not when it is part of the PUBLIC interface and the type that this PUBLIC interface returns, it is NOT the point at all.
>No, you trust the return type that you are told.
Which you find out by......oh look....searching each superclass to find the closest restricted return type. (Which is what I said in the first place)
>Correct. A 3D component should always have a 3D size.
Not neccessarily, I may want to create my own 3D size class that is not a child of the programmer's 3d size. At any rate, the example is not suppose to be a specific problem to be solved, it is trying to illustrate a scenario where restricted return types cause a gotcha. (I know there are ways around it, that is not even remotely close to the point I was making)
>It's not an accidental error, it's a deliberate restriction.
It may have been a programmer simply trying to save themselves a few casts, which seems to be one of the main reasons many people have given for this change so far - therefore far more likely.
>Doodad3 d3 = doodad3.modifyMe();
>Doodad d = doodad.modifyMe();.
There's nothing wrong with the code, if you are willing to
accept runtime type checks instead of compile time type
checks. But Java is a (mostly) strictly typed language
(unlike Python, Smalltalk, Ruby etc.) and I think it's a
huge advantage if the compiler can type check as much as
possible. It saves lots of time spent tracking down type
casting bugs.
I'm with megagurka. What's wrong with that code is that I
have to use a cast, when I already know what the return
type will always be.
There will be situations when programmers restrict what you
can do with their classes. That's the right of anybody who
publishes classes - they get to decide on the types and
interfaces. If they make a mistake, then that's their
fault, but nothing will prevent bad programmers. A good
programmer can make use of this to provide exactly the
right scope for future use, and to prevent future mis-use.
Aside from being a non-optimal solution, will
compiler-inserted casts even work? The compiler can figure
things out when it's dealing with all the files involved,
but what about when you're dealing with a pre-compiled
library? The method signature of the derived-class's method
will still be the same, right? And since it doesn't have
access to the original source code, the only way for the
compiler to figure out that covariance is being used is by
analyzing the method's bytecode.
A more fundamental change (one at a lower level than the
compiler) seems necessary.
One more reason to provide it:
C-Shrap doesnt have it.
Someone asked:
"Type safe is one thing, complicating the design is entirely
another. What happens to subclasses of that class? What
should they return?"
Of course, any subclass's return type must be at least as
narrow as its parents.
spau008's argument that people (well, programmers ;^)) could
misuse return type narrowing seems a little odd to me. I'm
of the opinion that any time you can supply more information
to the computer about the real intention behind the code,
the more likely it is that the machine will be able to find
any stupid errors that are there. Right now, the contract
on the behaviour of, say, the clone() method only explicitly
states that it returns an object (that the object is of the
same type as the object being cloned is merely an informal
thing that goes on behind the compiler's back) and this
forces every developer that uses it to clone a Foo object to
deal with the fact that the system might decide to return an
int[][] instead just because it felt like a bit of a
chuckle. Why can't I constrain the contract further?
Simple. It's a *compiler* restriction (and one that can be
eased without any bytecode changes.)
"Somebody might misuse it"? Might as well also remove
sockets, file-system access and GUIs, because they're all
susceptible to (much more serious) misuse...
yet another person who thinks this is a far cleaner and
theoretically better solution than generics....
Hm, to extent a collection with covariants you need to add 2
lines:
[code]public class MyCollection extends java.util.ArrayList {
public void add(MyObject o) { super.add(o); }
public MyObject get(int index) { return (MyObject)
super.get(index); }
}[/code]
Is it so hard? Explain me, please, why should java be
terminated with hostle generics synthax, memory footprint
overuse, 10% performance fall, cardinal changes in compiler
and JVM, loosing embedded device sector. And all of this to
satisfy ambtions of lasy persons who can't write 2 lines of
text? How to stop generics?
Please understand that this is NOT a replacement for generic
types! valjok, you seem to think you can replace generics
with covariant return types, which is not correct. In your
example you can still add Object's to MyCollection, which
breaks type safety. I think both generics and covariant
return types are valuable additions to the Java language.
> Explain me, please, why should java be terminated with
> hostle generics synthax, memory footprint overuse,
> 10% performance fall, cardinal changes in compiler
> and JVM...
I will, as soon as you explain to me why generic syntax is
"hostile," generics will either increase memory footprint or
decrease performance, or a JVM change is needed for
generics. As far as I can tell, none of these are true. If
you actually try the generics prototype compiler, you'll see
for yourself! And you'll also see that covariant return
types is not a replacement for generics, but instead another
useful change that will reduce the number of casts in source
code, thus increasing type safety.
valjok, you get it other way.
Currently proposed generics solution does not require jvm
changes. It also does not provide any overhead on runtime
(except maybe a bit longer signatures). It is your solution
which would be a kill for embedded solutions - because for
every specialization of container, you would like to create
separate class, replicating all tables and structures which
are needed to define it (and collections are certainly not
lightweight).
I support this suggestion strongly.
Dammit! It's been FIVE YEARS since Jun 1998, when this
minor change to the JLS was suggested!
I'll bet it's political - who "owns" this area of java? Someone
badly wants generics, and is opposing this change because
they know it would drastically ease the demand for them. God
Damn generics to hell! They're ugly in C++ and they'll be ugly
in java.
Please Sun! I'm gasping for air here! Just one, really, really,
tiny change! Just one! A method's return type must be the
same primitive type as the one it overloads, or an assignment-
compatible object type. The JLS, the compiler, and the class
loader. Jeeze - this is way simpler than adding assert, which
everyone was hot to do. It'd take an afternoon - if that.
To those who think it is a bad idea to allow co-variance as
described, would you prefer some sort of mark-up to make it
explicit, as proposed for generics and arrays?
Been poking around the web recently and have come to some
tentative conclusions:
jsdk 1.5 will have the change to the JLS we want as "part of
generics". I found this on the section describing the
enhanced-for loop
d-for.html
It looks like the change we want (i.e. JLS change with
bridge/adapter methods, no JVM change, no behind the
scenes casting) is coming through along with the Generics
which some people are dubious over.
From my reading, it appears that those who hate generics will
still be able to use the covariant return types without
incurring any behind the scenes casting costs.
Covariance will provide type-safety on iterators. For type-
safety on collections we'll need to summon the generic beast
to insert behind the scenes casts. There will be the runtime
performance hit but not the runtime risk of class cast
exceptions because the behind the scenes casts will be
provably safe at compile time.
Please, the language is broken without this. A simple
example. Say I want a Money class that combines BigDecimal
(to get proper handling of the pennies) and a Country object
(for exchange rates), so I can add Pounds Sterling and US
Dollars. This is a real requirement in some international
investment funds.
I want to have Money as a subclass of BigDecimal, so I can
override add(), subtract() and so forth. Now I can define
Money.add(Money) because it has a new method signature. But
I can't can't handle the exchange rate calculation properly.
There I have say the USD to GBP converion of today 1.68.
So I want Money.multiply(BigDecimal), and that currently
MUST return BigDecimal. The only way I can get Money back
is with a cast. Which is horrible.
Paul Gover
Perhaps I'm just being dumb, but why would Money inherit
from BigInteger? That seems like the Inappropriate
Inheritance Anti-Pattern to me...
Oops! BigDecimal, not BigInteger. My bad.
Tell me more, rfwan. Is "Note that that they rely on
covariant return types, which will be introduced as a part
of support for generics (JSR-14)" all we have so far? Or are
there more details on this aspect of JSR-14 out there?
Yes, hallelujah, it is part of the JSR-14 public draft.
"3.2 Overriding
<snip>
This specification requires that the result type of a method
is a subtype of the result types of all methods it
overrides. This is more general than previous specifications
of the Java programming language, which require the result
types to be identical. See Section 6.2 for an implementation
scheme to support this generalization."
You can see the public draft of JSR-14 via
It's catty of me, but I would still like to have seen this
RFE done in its own right, not simply as a side-effect
because its needed for something else.
Oh, by the way. It would be cool if the language spec would
accept those unicode big angle brackets to delimit generics.
PS it's still not included in the generics prototype! :-(
This is REALLY ESSENTIAL to be included with the upcomming
generics as this little programm shows:
public class Bug
{ public static void main(String[] args)
{ A<Object> a = new B<Object>(); // expected
error: Object is no Comparable
A<String> aa = new B<String>(); // expected no
error
A<Object> aaa = new B<String>(); // this should
work, shouldn't it? But it doesn't.
}
}
class A<T>
{}
class B<TT extends Comparable>
extends A<TT>
{}
This is a small bug reprodution program. The initial idea was
to built
binary trees and binary search trees, where a
BinarySearchTree<String>
was to be assigned to a BinaryTree<Object> or to be a
parameter for a
method like
public int countElements(BinaryTree<Object> tree) {...}
I just tried the following in Intellij (using EAP generics
support)
class X
{
public Exception getException() {...}
}
class Y extends X
{
public RuntimeException getException() {...} // compiler
now accepts this
}
Client code:
X x = new X();
Y y = new Y();
Exception e1 = x.getException();
RuntimeException e2 = y.getException(); // Look, no cast!
It works sweetly!
So assuming this feature is staying (it's difficult to
imagine generics working without it), someone from Sun could
put a few developers out of their collective missery by
stating that the problem has been resolved.
Nowdays it is indeed a serious tendency to use (and
most important to REUSE) a generic code. For a
small company sometime it can reduce investments
in development/support up to 10 times or more. In big
part the success of script languages like Python is
based on their ability to deal with generic code. So
everything which can reduce the amount of code to
write and maintain has a tremendous significance.
This is not about lazyness but about efficiency.
If I had 10000 votes I'd spend 9990 on this one!
We neded this 5 years ago!
There is a big issue with covariant throws in combination
with unchecked casts. Please have a look at
The examples shows taht you can trick the JVM and throw any
unchecked exception, not just RuntimeExceptions
That forum thread is irrelevant and stems from a belief
that Foo<Bar> must be a supertype of Foo<Object>. It
is hard to see how someone could become so
confused as to believe that to be the case!
As long as the return-type is a *strict* subtype of the
return-type in the superclass, a narrowing of the return-
type is guaranteed to be safe.
(Now, should RuntimeException have been a subtype
of Exception? I think not, but that's a mistake made
years ago now...)
> That forum thread is irrelevant and stems from a belief
> that Foo<Bar> must be a supertype of Foo<Object>.
In contrary, the example uses unchecked casts just to show
that with a throw statement, a Foo<Exception> illegally can
be treated like a Foo<RuntimeException>.
For methods with generic-typed return values an implicit
cast is used, which prevents illegal assignments. The issue
is that the thrown exception is not type-checked at compile
time not runtime.
Either the thrown exception must be type-checked (a JVM
issue?) or the unchecked cast mechanism must be improved to
solve this issue.
This feature can be helpful in using Stateless Sesion EJBs too, consider that you can have a generic Home interface with a create method,
And then you can have a factory for them, without need of reflection,
This feature must be added asap.
Absolutely Horrid Idea. There is no way to determine to determine which one to call. That's why you write A Wrapper Method.
more flexibility
This is a great Idea, now, support for future releases, another story. I would suggest the class should be allowed to provide a way to declair if this is permissable, with some sort of functionality similar to Template classes in C++.
Limiting the use of covariants makes absolutely no sense, nor does "writing a wrapper for it". I think a lot of people commenting on covariant return types don't actually understand what is implied.
Sun, thanks for providing this enhancment! | http://bugs.sun.com/bugdatabase/view_bug.do%3Fbug_id=4144488 | crawl-002 | refinedweb | 11,025 | 63.39 |
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Description
Example
This is the top of the tree, representing an unnamed level; it is A single period (.) or a period used at the sometimes shown as two empty quotation marks (""), end of a name, such as indicating a null value. When used in a DNS domain name, it is “example.microsoft). A name used to indicate a country/region or the type of organization using a name. Variable-length names registered to an individual or organization for use on the Internet. These names are always based upon an appropriate top-level domain, depending on the type of organization or geographic location where a name is used. Additional names that an organization can create that are derived from the registered second-level domain name. These include names added to grow the DNS tree of names in an organization and divide it into departments or geographic locations. Names that represent a leaf in the DNS tree of names and identify a specific resource. Typically, the leftmost label of a DNS domain name identifies a specific computer on the network. For example, if a name at this level is used in a host (A) RR, it is used to look up the IP address of computer based on its host name. ““.com”, which indicates a name registered to a business for commercial use on the Internet. ““microsoft.com. ”, which is the secondlevel domain name registered to Microsoft by the Internet DNS domain name registrar. ““example.microsoft.com. ”, which is a fictitious subdomain assigned by Microsoft for use in documentation example names.
Top level domain Second level domain
Subdomain
Host or resource name
““host-a.example.microsoft.com.”, where the first label (“host-a”) is the DNS host name for a specific computer on the network.letter and three-letter abbreviations used for countries/regions are shown in the following table: Some DNS Top-level Domain Names (TLDs)
DNS Domain Name com edu org net gov
Type of Organization Commercial organizations Educational institutions Non-profit organizations Networks (the backbone of the Internet) Non-military government organizations
mil arpa “xx”
Military government organizations Reverse DNS Two-letter country code (i.e. us, au, ca, fr)
Description Start of Authority
Class
Time To Live (TTL)
Type SOA
Data Owner Name Primary Name Server DNS Name, Serial Number Refresh Interval Retry Interval Expire Time Minimum TTL Owner Name (Host DNS Name) Host IP Address Owner Name Name Server DNS Name Owner Name Mail Exchange Server DNS Name, Preference Number Owner Name (Alias Name) Host DNS Name
Internet (IN) Default TTL is 60 minutes
Host Name Server Mail Exchanger
Internet (IN) Record-specific TTL if present, or else zone (SOA) TTL Internet (IN) Record-specific TTL if present, or else zone (SOA) TTL Internet (IN) Record-specific TTL if present, or else zone (SOA) TTL
A NS MX
Canonical Name Internet (IN) Record-specific TTL if present, or else (an alias) zone (SOA) TTL
CNAME
Distributing the DNS:
•
A need to delegate management of a DNS domain to a number of organizations or departments within an organization.
•
A need to distribute the load of maintaining one large DNS database among multiple DNS servers to improve the name resolution performance as well as create a DNS fault tolerant environment.
•
•:
• • •
Primary Secondary Stub
Primary is a zone to which all updates for the records that belong to that zone are made.. As mentioned above, a DNS server can host multiple zones. A DNS server can therefore.
Note
•
A secondary or stub zone cannot be hosted on a DNS server that hosts a primary zone for the same domain name.
Zone Transfer The process of replicating a zone file to multiple DNS servers is called zone transfer.Zone transfer:
•
The master DNS server sends a notification (RFC 1996) to one or more secondary DNS servers of a change in the zone file.
•:
• •
Recursive Iterative
A recursivequery. For more information about forwarders, see “Forwarding” later in this document. following figure shows an example of both types of queries. DNS Query Types
As shown in the graphic above, a number of queries were used to determine the IP address for. The query sequence is described below: 1. 2. 3.. 4. 5. 6. 7. 8... Note
•:
• • • • •
Message types DNS query message format DNS query message header DNS query question entries DNS resource records
• • • • • •
Name query message Name query response Reverse name query message DNS update message format DNS update message flags Dynamic update response message
Message Types There are three types of DNS messages:
• • • Message Format DNS Header (fixed length) Question Entries (variable length) Answer Resource Records (variable length) Authority Resource Records (variable length) Additional Resource Records(variable length) DNS Query Message Header The DNS message header contains the following fields, in the following order: DNS Query Message Header Fields
Field Name Transaction ID
Description A 16-bit field identifying a specific DNS transaction. The transaction ID is created by the message originator and is copied by the responder into its response message. Using the transaction ID, the DNS client can match responses to its requests. A 16-bit field containing various service flags that are communicated between the DNS client and the DNS server, including:
Flags:
Request/response Operation code Authoritative answer Truncation
1-bit field set to 0 to represent a name service request or set to 1 to represent a name service response. 4-bit field represents the name service operation of the packet: 0x0 is a query. 1-bit field represents that the responder is authoritative for the domain name in the query message. 1-bit field that is set to 1 if the total number of responses exceeded the User Datagram Protocol (UDP) datagram. Unless UDP datagrams larger than 512 bytes or EDNS0 are enabled, only the first 512 bytes of the UDP reply are returned. 1-bit field set to 1 to indicate a recursive query and 0 for iterative queries. If a DNS server receives a query message with this field set to 0 it returns a list of other DNS servers that the client can choose to contact. This list is populated from local cache data. 1-bit field set by a DNS server to 1 to represent that the DNS server can handle recursive queries. If recursion is disabled, the DNS server sets the field appropriately. 3-bit field that is reserved and set to 0. 4-bit field holding the return code:
Recursion desired
Recursion available Reserved Return code
• •
0 is a successful response (query answer is in the query response).
0x3 is a name error, indicating that an authoritative DNS server responded that the
domain name in the query message does not exist. For more information about return codes, see “Related Information" at the end of this document.
Question Resource Record count Answer Resource Record count Authority Resource Record count Additional Resource Record count
A 16-bit field representing the number of entries in the question section of the DNS message. A 16-bit field representing the number of entries in the answer section of the DNS message. A 16-bit field representing the number of authority resource records in the DNS message. A 16-bit field representing the number of additional resource records in the DNS message.
DNS Query Question Entries The DNS message’s Question Entries section contains the domain name that is being queried and has the following three fields: DNS Query Question Entry Fields
Field Name Description Question Name The domain name that is being queried. DNS domain names are expressed as a series of labels, such as microsoft.com, but in the Question Name field the domain name is encoded as a series of length-value pairs consisting of a 1-byte file that indicates the length of the value, followed by the value (the label). For example, the domain microsoft.com is expressed as 0x09microsoft0x03com0x00, where the hexadecimal digits represent the length of each label, the ASCII characters indicate the individual labels, and the final 0 indicates the end of the name. Uses a 16-bit integer to represents the resource record type that should be returned, as expressed below: Record(s) Returned Host (A) record Name server (NS) record Alias (CNAME) record
Question Type Type value 0x01 0x02 0x05
0x0C (12) 0x0F (15) 0x21 (33) 0xFB (251) 0xFC (252) 0xFF (255) Question Class
Reverse-lookup (PTR) record Mail exchange (MX) record Service (SRV) record Incremental zone transfer (IXFR) record Standard zone transfer (AXFR) record All records Represents the IN (Internet) question class and is normally set to 0x0001.
DNS Resource Records The answer, authority, and additional information sections of a DNS response message can contain resource records that answer the query message question section. Resource records are formatted as follows: DNS Resource Record Message Fields
Field Name Resource record name Resource record type Resource record class Time-to-live Resource data length Resource data
Description The DNS domain name recorded as a variable-length field following the same formatting as the Question Name field. The resource record type value. The resource record class code, the Internet class, 0x0001. The TTL expressed in seconds as a 32-bit unsigned field. 2-byte field indicating the length of the resource data. Variable-length data corresponding to the resource record type.
Field Name Query identifier (Transaction ID) Flags Question count Question entry
Description Set to a unique number to enable the DNS client resolver to match the response to the query. The query response transaction ID always matches the query request transaction ID. Set to indicate a standard query with recursion enabled. Set to 1. Set to the domain name queried and the resource record type to return.
Name Query Response A Name Query Response message format is the same as the DNS message format described above. In a typical Name Query message, the DNS message fields would be set as follows: DNS Name Query Response Fields
Field Name Query identifier (Transaction ID) Flags Question count Question entry
Description Set to a unique number to enable the DNS client resolver to match the response to the query. Set to indicate a standard query with recursion enabled. Set to 1. Set to the domain name queried and the resource record type to return.
Reverse Name Query Message Reverse name query messages use the common message format with the following differences:
•
The DNS client resolver constructs the domain name in the in-addr.arpa domain based on the IP address that is queried.
•:
•
Identification. A 16-bit identifier assigned by the DNS client requestor. This identifier is copied in the corresponding reply and can be used by the requestor to match replies to outstanding requests, or by the server to detect duplicated requests from some requestor.
•
Flags. A 16-bit DNS update message flags field. For a description of each flag, see “DNS Update Message Flags” below.
• •
Number of zone entries. The number of resource records in the Zone entry section. Number of prerequisite resource records. The number of resource records in the Prerequisite resource records section.
• •
Number of update resource records. The number of resource records in the Update resource records section. Number of additional resource records. The number of resource records in the Additional resource records section.
•.
•
Prerequisite resource records. Contains a set of resource record prerequisites which must be satisfied at the time the update message is received by the master DNS server. There are five possible sets of values that can be expressed:
•
Resource record set exists (value independent). At least one resource record with a specified name and
type (in the zone and class specified by the Zone Section) must exist.
•
Resource record set exists (value dependent). A set of resource records with a specified name and type
exists and has the same members with the same data as the resource record set specified in this section.
•
Resource record set does not exist. No resource records with a specified name and type (in the zone and
class denoted by the Zone section) exist.
•
Name is in use. At least one resource record with a specified name (in the zone and class specified by the
Zone section) exists. This prerequisite is not satisfied by empty nonterminals.
•
Name is not in use. No resource record of any type is owned by a specified name. This prerequisite is
satisfied by empty nonterminals.
•
Update resource records. Contains the resource records that are to be added or deleted from the zone. One of four operations are performed during the update:
• • • • •:
• • • •
Result Code Value Description 0 (NOERROR) 1 (FORMERR) 0x2 (SERVFAIL) 0x3 (NXDOMAIN) 0x4 (NOTIMP) 0x5 (REFUSED) 0x6 (YXDOMAIN) No error; successful update. Format error; DNS server did not understand the update request. DNS server encountered an internal error, such as a forwarding timeout A name that should exist does not exist. DNS server does not support the specified Operation code. DNS server refuses to perform the update because A name that should not exist does exist.
0x7 (YXRRSET) 0x8 (NXRRSET) 0x9 (NOTAUTH) 0xA (NOTZONE)
A resource record set that should not exist does exist. A resource record set that should exist does not exist. DNS server is not authoritative for the zone named in the Zone section. A name used in the Prerequisite or Update sections is not within the zone specified by the Zone section.:
• • • • • •.
• •
Maintains connection-specific domain name suffixes. Prioritizes which DNS servers it uses according to whether they respond to a query if multiple DNS server are configured on the client.
• • XP, Windows 2000 and Windows Server 2003 DNS client configuration involves the following settings in the TCP/IP properties for each computer:
•
Domain Names. Domain names are to form the fully qualified domain name (FQDN) for DNS clients.
•
Host names. A DNS computer or host name for each computer. For example, in the fully qualified domain name (FQDN) wkstn1.example.microsoft.com., the DNS computer name is the leftmost label client1.
•
Primary DNS suffixes. A primary DNS suffix for the computer, which is placed after the computer or host name to form the FQDN. Using the previous example, the primary DNS suffix would be example.microsoft.com.
•
Connection-specific names. Each network connections of a multihomed computer can be configured with a connection-specific DNS domain name
• •.
•, described in the previous section..:
•
A primary full computer name, which applies as the default full computer name for the computer and all of its configured network connections.
• create a restricted list of allowed suffixes by creating the msDSAllowedDNSSuffixes attribute in the domain object container. This attribute is created and managed by the domain administrator using Active Directory Service Interfaces (ADSI) or the Lightweight Directory Access Protocol (LDAP). Connection-specific Names As shown in the following figure, a multihomed server computer named “host-a” can be named according to both its primary and connection-specific DNS domain names. Connection-specific DNS Names:
•
The name “host-a.public.example.microsoft.com” provides access using LAN connection 1 over Subnet 1, a lowerspeed (10 megabit) Ethernet LAN, for normal access to users who have typical file and print service needs.
•
The name “host-a.backup.example.microsoft.com” provides access using LAN connection 2 over Subnet 2, a higher-speed (100 megabit) Ethernet LAN, for reserved access by server applications and administrators who have
special needs, such as troubleshooting server networking problems, performing network-based backup, or replicating
DNS Name host-a.example.microsoft.com
IP Addresses Description 10.1.1.11, 10.2.2.22 10.1.1.11 Primary DNS name for computer. The computer registers A and PTR resource records for all configured IP addresses under this name in the “example.microsoft.com” zone. Connection-specific DNS name for LAN connection 1, which registers A and PTR resource records for IP address 10.1.1.11 in the “public.example.microsoft.com” zone. Connection-specific DNS name for LAN connection 2, which registers A and PTR resource records for IP address 10.2.2.22 in the “backup.example.microsoft.com” zone.
hosta.public.example.microsoft.com hosta.backup.example.microsoft.com
10.2.2.22. Note
•
•
•
Name Type NetBIOS name
Description necessary to make the name 15 bytes long, plus the service identifier. For example, a NetBIOS name might be Client1. The host name is the first label of a FQDN. For example, the first label of the FQDN client1.example.com is client1. Every Windows XP and Windows Server 2003 computer can be assigned a primary DNS suffix to be used in name resolution and name registration. You can view the primary DNS suffix for your computer from the Computer Name tab of SystemProperties. The primary DNS suffix is also known as the primary domain name. For example, the FQDN client1.example.com has the primary DNS suffix example.com.
Host name Primary DNS suffix
ConnectionThe connection-specific DNS suffix is a DNS suffix that is assigned to a network connection. The specific DNS suffix connection-specific DNS suffix is also known as an adapter-specific DNS suffix. For example, a connection-specific DNS suffix might be acquired01-ext.com. Fully Qualified Domain Name (FQDN) Full computer name. The full computer name is the FQDN for a Windows XP, Windows 2000 or Windows Server 2003 computer. It is the concatenation of the host name and primary DNS suffix (or host name and connection-specific DNS suffix).
DNS Servers List XP and Windows Server 2003. DNS Suffix Search List. Once. Name Restrictions for Hosts and Domains Different DNS implementations allow different characters and lengths, and differ from NetBIOS naming restrictions. The following table shows the restrictions for standard DNS names, DNS names in Windows Server 2003 and NetBIOS Names.
Restriction Characters
Standard DNS (Including Windows NT 4.0)
DNS in Windows Server 2003
NetBIOS Permits Unicode characters, numbers, white space, symbols: ! @ $ % ^ & ) ( . _{}~ Permits 16 bytes for a host name
Supports RFC 1123, which Several different configurations are permits “A” to Z, “a” to “z”, “0” to possible, as described at the end of “9”, and the hyphen (-) this section Permits 63 bytes per label and 255 bytes for an FQDN Permits 63 bytes per label and 255 bytes for an FQDN; the FQDN for an Active Directory domain name is limited to 64 bytes
Fully qualified domain name length Note
•:
•
Some third-party DNS client software supports only the characters listed in RFC 1123. Third-party DNS client software may not able to resolve the DNS names of computers with names that use characters outside the set supported by RFC 1123.
•.
•
•:
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IN A IN A IN A
172.16.64.11 172.17.64.22 172.18.64.33
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Note
IN A IN A IN A
172.17.64.22 172.16.64.11 172.18.64.33
•:
• • • •:
•
Servers can send referral answers, which are an immediate response to the requesting client with a list of resource records for other DNS servers that it knows about that appear to be closer or more likely to be of help in resolving the queried name.
•. Note
•
If you disable recursion on the DNS server, you will not be able to use forwarders on the same server. For more information about forwarders, see “Forwarding” later in this document.
Round Robin:
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multihomed
IN
A
10.0.0.1
multihomed multihomed
IN IN
A A
10.0.0.2 10.0.0.3
The first DNS client that queries the server to resolve this host’s name receives the list in default order. When a second client sends a subsequent query to resolve this name, the list is rotated as follows:
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multihomed multihomed multihomed: 1. The DNS Server service determines if local subnet prioritization is necessary. 2. For each RR in the matched answer list, the DNS Server service determines which records (if any) match the subnet location of the requesting client. 3. The DNS Server service reorders the answer list so that A RRs which match the local subnet of the requesting client are placed first in the answer list. 4. Prioritized by subnet order, the answer list is returned to the requesting client.
IN IN IN
A A A
10.0.0.2 10.0.0.3 10.0.0.1
Simple example: Local network prioritizing:
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multihomed multihomed multihomed:
IN IN IN
A A A
192.168.1.27 10.0.0.14 172.16.20.4
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multihomed multihomed multihomed
IN IN IN
A A A
10.0.0.14 192.168.1.27 172.16.20.4
If the IP address of the requesting client has no local network match with any of the RRs in the answer list, then the list is not prioritized. Complex example: Local subnet prioritizing In Windows Server 2003,:
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multihomed multihomed multihomed multihomed
IN IN IN IN
A A A A
192.168.1.27 172.16.22.4 10.0.0.14 172.16.31.5:
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multihomed multihomed multihomed multihomed
Note
IN IN IN IN
A A A A
172.16.22.4 172.16.31.5 192.168.1.27 10.0.0.14
•
Value
Description
Disable recursion Determines whether or not. Sets the DNS server to parse files strictly.
Fail on load if
bad zone data
By default, the DNS Server service logs data errors, ignore any erred data in zone files, and continue to load a zone. This option can be reconfigured using the DNS console so that the DNS Server service logs errors and fails to load a zone file containing records data that is determined to have errors. Determines whether the DNS server uses round robin to rotate and reorder a list of resource records (RRs) if multiple RRs exist of the same type exisit for a query answer. Determines whether the DNS server reorders A resource records within the same resource record set in its response to a query based on the IP address of the source of the query. or not where this feature is enabled for use.
Enable round robin Enable netmask ordering Secure cache against pollution
Resource Records in DNS. Authority Records Zones are based on a concept of server authority. When a DNS server is configured to load a zone, it uses two types of resource records to determine the authoritative properties of the zone:
•
First, the start of authority (SOA) resource record indicates the name of origin for the zone and contains the name of the server that is the primary source for information about the zone. It also indicates other basic properties of the zone.
• SOA resource record. The SOA resource record contains the following information: SOA Resource Record Fields
Field Primary server
Description The host name for the primary DNS server for the zone.
(owner) Responsible person Serial number The e-mail address of the person responsible for administering the zone. A period (.) is used instead of an at sign (@) in this e-mail name. The revision number of the zone file. This number increases each time a resource record in the zone changes. It is important that this value increase each time the zone is changed, so that either partial zone changes or the fully revised zone can be replicated to other secondary servers during subsequent transfers.). The time, in seconds, a secondary server waits before retrying a failed zone transfer. Normally, this time is less than the refresh interval. The default value is 600 seconds (10 minutes).). The default Time-To-Live (TTL) of the zone and the maximum interval for caching negative answers to name queries. The default value is 3,600 seconds (1 hour).
Refresh interval
Retry interval Expire interval
Minimum (default) TTL
The following is an example of a default SOA resource record:
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@ IN SOA nameserver.example.microsoft.com. postmaster.example.microsoft.com. ( 1 ; serial number 3600 ; refresh [1h] 600 ; retry [10m] 86400 ; expire [1d] 3600 ) ; min TTL [1h]
In the example SOA record shown above,. The NS resource record Name server (NS) resource records can be used to assign authority to specified servers for a DNS domain name in two ways:
•
By establishing a list of authoritative servers for the domain so that those servers can be made known to others that request information about this domain (zone).
• Name Server Resource Record
Description: Used to map a DNS domain name as specified in owner to the name of hosts operating DNS servers specified in the name_server_domain_name field. Syntax: owner ttl IN NS name_server_domain_name. Example:
example.microsoft.com.
IN NS nameserver1.example.microsoft.com
Other Important Records After a zone is created, additional resource records need to be added to it. The following table lists the most common resource records (RRs) to be added. Common DNS Resource Records
Resource Record Description Host (A) Alias (CNAME) Mail Exchanger (MX) Pointer (PTR) Service location (SRV) For mapping a DNS domain name to an IP address used by a computer. For mapping an alias DNS domain name to another primary or canonical name. For mapping a DNS domain name to the name of a computer that exchanges or forwards mail. For mapping a reverse DNS domain name based on the IP address of a computer that points to the forward DNS domain name of that computer. For mapping a DNS domain name to a specified list of DNS host computers that offer a specific type of service, such as Active Directory domain controllers.:
• •
When a host specified in an A RR in the same zone needs to be renamed. When a generic name for a well-known server such as www needs to resolve to a group of individual computers (each with individual A RRs) that provide:
• • •.
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ftp www
IN IN
host-a IN CNAME host-a CNAME host-a
A
10.0.0.20:
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host-b ftp www
IN IN IN
host-a IN A A 10.0.0.21 CNAME host-b CNAME host-a
10.0.0.20
Mail exchanger (MX) resource records.
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mail_domain_name IN MX preference mailserver_host.
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@ @ IN MX 2
IN MX 1 mailserver1
mailserver0
Note that the use of the at sign (@) in the records indicates that the mailer DNS domain name is the same as the name of origin (example.microsoft.com) for the zone. Pointer (PTR) resource records:
•
You can manually create a PTR RR for a static TCP/IP client computer using the DNS , either as a separate procedure or as part of the procedure for creating an A RR.
•
Computers use the DHCP Client service to dynamically register and update their PTR RR in DNS when an IP configuration change occurs.
•.
•
The computer operating your DNS server is running on another platform, such as UNIX, and cannot accept or recognize dynamic updates.
•
A DNS server at this computer that is not the DNS Server service provided with the Windows Server 2003 operating system is authoritative for the primary zone corresponding to the DNS domain name for your Active Directory domain.
•
The DNS server supports the SRV RR, as defined in the Internet draft, “A DNS RR specifying the location of services (DNS SRV)”, but does not support dynamic updates.
•.
File Boot
Description zone file. This file can appear at a DNS server if it is configured as a root server for your network. Used when a standard zone (either primary or secondary) is added and configured for the server. Files of this type are not created or used for primary type zones that are directory-integrated, which are stored in the Active Directory database.
Cache.dns
Root.dns zone_name.dns
These files can be found in the systemroot\System32\Dns folder on the server computer. Zones and Zone Transfer DNS distributes the DNS namespace database using DNS zones, which store name information about one or more DNS domains. There are three types of DNS zones supported in Windows Server 2003:
• •
Primary zone. Original copy of a zone where all resource records are added, modified, and deleted. Secondary zone. Read-only copy of the primary zone that is created and updated by transferring zone data from the primary zone.
•
Stub zone. Read-only copy of the primary zone containing only the DNS resource records for the DNS servers listed in the zone (SOA, NS, and glue A resource records).
Difference Between Zones and Domains A zone starts as a storage database for a single DNS domain name. If other domains are added below the domain used to create the zone, these domains can either be part of the same zone or belong to another zone. Once a subdomain is added, it can then either be:
• •. Why Zone Replication and Zone Transfers Are Needed 2003, the DNS service supports incremental zone transfer, a revised DNS zone transfer process for intermediate changes. Domain Delegation:
•
A need to delegate management of part of your DNS namespace to another location or department within your organization.
• •:
•
Additional DNS servers provide zone redundancy, enabling DNS names in the zone to be resolved for clients if a primary server for the zone stops responding.
•
Additional DNS servers can be placed so as to reduce DNS network traffic. For example, adding a DNS server to the opposing side of a low-speed wide area network (WAN) link can be useful in managing and reducing network traffic.
•
Additional DNS. Delegating a Subdomain. These RRs include:
•
An NS RR to effect the delegation. This RR is used to advertise that the server named ns1.na.example.microsoft.com is an authoritative server for the delegated subdomain.
•
•:
• • • •. Zone transfer process As shown in the following figure, zone transfers between servers follow an ordered process. This process varies depending on whether a zone has been previously replicated, or if initial replication of a new zone is being performed. Zone Transfer Process
1.
During new configuration, the destination server sends an initial “all zone” transfer (AXFR) request to the master DNS server configured as its source for the zone.
2..
3.
When the refresh interval expires, an SOA query is used by the destination server to request renewal of the zone from the source server.
4. needed.
5.
If the destination server concludes that the zone has changed, it sends an IXFR query to the source server, containing its current local value for the serial number in the SOA record for the zone.
6.
The source server responds with either an incremental or full transfer of the zone. If the source server supports incremental transfer by maintaining a history of recent incremental zone changes for modified resource records, it can answer with an incremental zone transfer (IXFR) of the zone. If the source server does not support incremental transfer, or does not have a history of zone changes, it can answer with a full (AXFR) transfer of the zone instead.
Note
•:
•.
• •
•:
•
The start of authority (SOA) resource record, name server (NS) resource records, and the glue A resource records for the delegated zone.
• Stub zone updates involve the following conditions:
•
When a DNS server loads a stub zone, it queries the zone’s master server for the SOA resource record, NS resource records at the zone’s root, and glue A resource records.
•
During updates to the stub zone, the master server is queried by the DNS server hosting the stub zone for the same resource record types requested during the loading of the stub zone.
•
The Refresh interval of the SOA resource record determines when the DNS server hosting the stub zone will attempt a zone transfer (update).
• •:
• •. Note
•
If you are operating internal root servers, do not use root hints. Instead, delete the Cache.dns file entirely for any of your root servers.
EDNS0. Windows Server 2003
Name FORMERR SERVFAIL NOTIMPL
Value 1 2 4
Description Format Error. The name server did not interpret the OPT resource record. Server Failure. The name server did not process the query because of a problem with the name server. Not Implemented. The name server does not support the kind of query requested.
(The RCODE field, or response code field, is a 4-bit field set in the header section as part of responses.) In this situation (as a requester), the DNS server identifies that the server does not support EDNS0 and caches this information. Note
•. the “DNS Resource Records Reference” later in this document. For more information about related RFCs, see “Related Information” at the end of this document.. Note
•:
•
DNS replication is performed by Active Directory, so there is no need to support a separate replication topology for DNS servers.
• • •
•:
• was “example.microsoft.com.”
•and zones stored in Active Directory. Note
•
•
Changing the startup type is not recommended and could result in DNS infrastructure errors.
How the DNS Server Loads Zones, Root Hints, and Parameters
Task
Load Data On Startup Set To:
Load Data On Startup Set To: From Registry
Load Data On Startup Set To: From Active Directory and
From File Read root hints from: Root hints file
Registry If available, the root hints file. If the directory is available and Otherwise, if the Directory is available contains root hints, from the and contains root hints, the directory directory. Otherwise, from the root hints file Root hints file If the directory is available, the directory The directory (for Active Directory– integrated zones) and the registry Registry and, if the zone is Active Directory–integrated, the directory The directory (for Active Directory– integrated zones) and the registry The directory (for Active Directory– integrated zones) and the registry
Write root hints to: Read zones from:
Root hints file
Boot file, to get list Registry of zones, then from zone files Boot file and the registry Boot file and the registry Boot file and the registry Registry and, if the zone is Active Directory–integrated, the directory Registry and (for Active Directory– integrated zones) the directory Registry (for all zones) and (for Active Directory–integrated zones) the directory
Write zones to: Read server and zones parameters from: Write server and zones parameters to::
• • Active Directory. The following are examples of Active Directory service class objects:
• • • •
•
Active Directory Storage Option Domain partition
Description Active Directory domain partition for each domain in the forest. DNS zones stored in this partition are replicated to all domain controllers in the domain. This is the only Active Directory storage option for DNS zones that are replicated to domain controllers running Windows 2000 Server. DNS application directory partition for the entire forest. DNS zones stored in this application directory partition are replicated to all DNS servers running on domain controllers in the forest. This DNS application directory partition is created when you install the DNS Server service on the first Windows Server 2003 domain controller in the forest. DNS application directory partition for each domain in the forest. DNS zones stored in this application directory partition are replicated to all DNS servers running on domain controllers in the domain. For the forest root domain, this DNS application directory partition is created when you first install the DNS Server service on a Windows Server 2003 domain controller in the forest. For each new domain in the forest (child domain), this DNS application directory partition is created when you first install the DNS Server service on a Windows Server 2003 domain controller for the new domain. DNS application directory partition for any domain controller that is enlisted in its replication scope. This type of DNS application directory partition does not exist by default and must be created. DNS zones stored in this application directory partition are replicated to all DNS servers running on domain controller that enlist in the partition.
Forest-wide DNS application directory partition
Domain-wide DNS application directory partition
Custom DNS application directory partition Note
•
Object DnsZone DnsNode DnsRecord DnsProperty
Description Container created when a zone is stored in Active Directory. Leaf object used to map and associate a name in the zone to resource data. Multivalued attribute of a dnsNode object used to store the resource records associated with the named node object.:
• •:
• • •
@, which signifies that the node has the same name as the dnsZone object. delegated, a delegated subdomain. host.notdelegated, a host in the domain not delegated.example.com, a domain that is controlled by the zone on example.com.
• • • •
• When a DNS client needs to look up a name used in a program, it queries DNS servers to resolve the name. Each query message the client sends contains three pieces of information, specifying a question for the server to answer: 1. 2. 3. A specified DNS domain name, stated as a fully qualified domain name. A specified query type, which can either specify a resource record by type or a specialized type of query operation. A specified class for the DNS domain name. For Windows DNS servers, this should always be specified as the Internet (IN) class. For example, the name specified could be the FQDN for a computer, such as ““host-a.example.microsoft.com.””, and the query type specified to look for an address (A) resource record by that name. Think of a DNS query as a client asking a server a two-part question, such as “Do you have any A resource records for a computer named ‘host using cached information obtained from a previous query. The DNS server can use its own cache of resource record information to answer a query. A DNS server can also query or contact other DNS servers on behalf of the requesting client to fully resolve the name,:
• •: DNS Client Service Resolver The following figure shows an overview of the complete DNS query process. Overview of:
•
If a Hosts file is configured locally, any host name-to-address mappings from that file are preloaded into the cache when the DNS Client service is started.
•. Part 2: Querying a DNS Server As indicated in the previous figure, the client queries a preferred DNS server. The actual resource record in local zone information, the server answers authoritatively, using this information to resolve the queried name. If no zone information exists for the queried name, the server then checks to see if it can resolve the name using locally cached information from previous queries. If a match is found here, the server answers with this information. Again, if the preferred server can answer with a positive matched response from its cache to the requesting client, the query is completed. If the queried name does not find a matched answer at its preferred server — either from its cache or zone information — the query process can continue, using recursion to fully resolve the name. This involves assistance from other DNS servers to help resolve the name. By default, the DNS Client service asks the server to use a process of recursion to fully resolve names on behalf of the client before returning an answer..
By using root hints to find root servers, a DNS server is able to complete the use of recursion. In theory, this process enables any DNS server to locate the servers that are authoritative for any other DNS domain name used at any level in the namespace tree. For example, consider the use of the recursion process to locate the name “host-b.example.microsoft.com.” when the client queries a single DNS server. The process occurs when a DNS server and client are first started and have no locally cached information available to help resolve a name query. It assumes that the name queried by the client is for a domain name of which the server has no local knowledge, based on its configured zones. First, the preferred server parses the full name and determines that it needs the location of the server that is authoritative for the top-level domain, “com”. It then uses an iterative query to the “com” DNS server to obtain a referral to the “microsoft.com” server. Next, a referral answer comes from the “microsoft.com” server to the DNS server for “example.microsoft.com”. Finally, the “example.microsoft.com.” server is contacted. Because this server contains the queried name as part of its configured zones, it responds authoritatively back to the original server that initiated recursion. When the original server receives the response indicating that an authoritative answer was obtained to the requested query, it forwards this answer back to the requesting client and the recursive query process is completed. Although the recursive query process can be resource-intensive when performed as described above, it has some performance advantages for the DNS server. For example, during the recursion process, the DNS server performing the recursive lookup obtains information about the DNS domain namespace. This information is cached by the server and can be used again to help speed the answering of subsequent queries that use or match it. Over time, this cached information can grow to occupy a significant portion of server memory resources, although it is cleared whenever the DNS service is cycled on and off.: 1. The DNS Client service sends the name query to the first DNS server on the preferred adapter’s list of DNS servers and waits one second for a response. 2. If the DNS Client service does not receive a response from the first DNS server within one second, it sends the name query to the first DNS servers on all adapters that are still under consideration and waits two seconds for a response. 3. If the DNS Client service does not receive a response from any DNS server within two seconds, the DNS Client service sends the query to all DNS servers on all adapters that are still under consideration and waits another two seconds for a response. 4. If the DNS Client service still does not receive a response from any DNS server, it sends the name query to all DNS servers on all adapters that are still under consideration and waits four seconds for a response.
5.:
• • • •
An authoritative answer A positive answer A referral answer (used by the Windows Server 2003 DNS Server service only) A negative answer
An authoritative answer is a positive answer returned to the client and delivered with the authority bit set in the DNS message to indicate the answer was obtained from a server with direct authority for the queried name. A positive response can consist of the queried RR or a list of RRs (also known as an RRset) that fits the queried DNS domain name and record type specified in the query message.
A referral answer contains additional RRs not specified by name or type in the query. This type of answer is returned to the client if the recursion process is not supported. The records are meant to act as helpful reference answers that the client can use to continue the query using iteration. A referral answer contains additional data such as RRs that are other than the type queried. For example, if the queried host name was “www” and no A RRs for this name were found in this zone but a CNAME RR for “www” was found instead, the DNS server can include that information when responding to the client. If the client is able to use iteration, it can make additional queries using the referral information in an attempt to fully resolve the name for itself. A negative response from the server can indicate that one of two possible results was encountered while the server attempted to process and recursively resolve the query fully and authoritatively:
• •
An authoritative server reported that the queried name does not exist in the DNS namespace. An authoritative server reported that the queried name exists but no records of the specified type exist for that name.
The resolver passes the results of the query, in the form of either a positive or negative response, back to the requesting program and caches the response. If the resultant answer to a query is too long to be sent and resolved in a single UDP message packet, the DNS server can initiate a failover response over TCP port 53 to answer the client fully in a TCP connected session. Disabling the use of recursion on a DNS server is generally done when DNS clients are being limited to resolving names to a specific DNS server, such as one located on your intranet. Recursion might also be disabled when the DNS server is incapable of resolving external DNS names, and clients are expected to fail over to another DNS server for resolution of these names. If you disable recursion on the DNS server, you will not be able to use forwarders on the same server. By default, DNS servers use several default timings when performing a recursive query and contacting other DNS servers. These defaults include:
•
A recursion retry interval of 3 seconds. This is the length of time the DNS service waits before retrying a query made during a recursive lookup.
•
A recursion time-out interval of 15 seconds. This is the length of time the DNS service waits before failing a recursive lookup that has been retried.
Under most circumstances, these parameters do not need adjustment. However, if you are using recursive lookups over a slow-speed WAN link, you might be able to improve server performance and query completion by making slight adjustments to the settings. How Iteration Works Iteration is the type of name resolution used between DNS clients and servers when the following conditions are in effect:
• •.
The Windows Server 2003 DNS Client service does not perform recursion. in the zone’s start of authority (SOA) resource record. By default, the minimum TTL is 3,600 seconds (one hour) but can be adjusted or, if needed, individual caching TTLs can be set at each RR. Note
•
•: 1.. 2. Once located, the authoritative DNS server for “20.1.168.192.in-addr.arpa” can respond with the PTR record information. This includes the DNS domain name for “host-a”, completing the reverse lookup
•.: 1. When the DNS server receives a query, it attempts to resolve this query using the primary and secondary zones that it hosts and its cache. 2. If the query cannot be resolved using this local data, then it will forward the query to the DNS server designated as a forwarder. 3.
•:
•
By default, the DNS client on Windows XP does not attempt dynamic update over a Remote Access Service or virtual private network connection. To modify this configuration, you can modify the advanced TCP/IP settings of the particular network connection or modify the registry.
•
By default, the DNS client does not attempt dynamic update of top-level domain (TLD) zones. Any zone named with a single-label name is considered a TLD zone, for example, com, edu, blank, my-company.
•).
Dynamic updates can be sent for any of the following reasons or events:
•
An IP address is added, removed, or modified in the TCP/IP properties configuration for any one of the installed network connections.
•
An IP address lease changes or renews with the DHCP server any one of the installed network connections. For example, when the computer is started or if the ipconfig /renew command is used.
• • •
The ipconfig /registerdns command is used to manually force a refresh of the client name registration in DNS.:
Computer name DNS domain name of computer Full computer name
oldhost example.microsoft.com oldhost.example.microsoft.com
In this example, no connection-specific DNS domain names are configured for the computer. Later, the computer is renamed from “oldhost” to “newhost”, resulting in the following name changes on the system:
Computer name DNS domain name of computer Full computer name
newhost example.microsoft.com newhost.example.microsoft.com
Once the name change is applied in System properties, you are prompted to restart the computer. When the computer restarts Windows, the DHCP Client service performs the following sequence to update DNS: 1.. 2.. 3.:
• • • •.
•
After the SOA query is resolved, the client sends a dynamic update to the server specified in the returned SOA record.
• •
If the update succeeds, no further action is taken. If this update fails, then the client repeats the SOA query process by sending to the next DNS server listed in the response.
4.
Field Code Len Flags
Explanation Specifies the code for this option (81). Specifies the length, in octets, of this option (minimum of 4). Can be one of the following values: 0. Client wants to register the A resource record and requests that the server update the PTR resource record. 1. Client wants server to register the A and PTR resource records. 3. DHCP server registers the A and PTR resource records regardless of the request of the client. The DHCP server uses these fields to specify the response code from the A and PTR resource records registrations performed on the client’s behalf and to indicate whether it attempted the update before sending DHCPACK. Specifies the FQDN of the client.
RCODE1 and RCODE 2 Domain Name:
•.
•:
• •.
•:
•.
•:
•.
•:
•
To initiate a secure dynamic update, the DNS client first initiates the security context negotiation process, during which the tokens are passed between client and server using TKEY resource records. At the end of the negotiation process the security context is established.
•.
•:
1..
2..
3. 4.
The DNS client and DNS server begin TKEY negotiation. First, the DNS client and DNS server negotiate an underlying security mechanism. Windows dynamic update clients and DNS servers can only use the Kerberos protocol.
5.
Next, by using the security mechanism, the DNS client and DNS server verify their respective identities and establish the security context.
6..
7.
The DNS server attempts to add, delete, or modify resource records in Active Directory. Whether or not it can make the update depends on whether the DNS client has the proper permissions to make the update and whether the prerequisites have been satisfied.
8.
•.
• with the account credentials under the following circumstances:
• • • command (netsh dhcp server set dnscredentials). Note
•
If the supplied credentials belong to an object (such as a computer) that is a member of the DnsUpdateProxy security group, the next object to register the same name record in DNS will become the record owner.
•:
•
If a large number of stale RRs remain in server zones, they can eventually take up server disk space and cause unnecessarily long zone transfers.
•
DNS servers loading zones with stale RRs might use outdated information to answer client queries, potentially causing the client’s to experience name resolution problems on the network.
• •:
•
Time stamping, based on the current date and time set at the server computer, for any RRs added dynamically to primary-type zones. In addition, time stamps are recorded in standard primary zones where aging/scavenging is enabled.
•
For RRs that you add manually, a time stamp value of zero is used, indicating that they are not affected by the aging process and can remain without limitation in zone data unless you otherwise change their time stamp or delete them.
•
Aging of RRs in local data, based on a specified refresh time period, for any eligible zones. Only primary type zones that are loaded by the DNS Server service are eligible to participate in this process.
•
Scavenging for any RRs that persist beyond the specified refresh period. When a. Note
• and Scavenging Before the aging and scavenging features of DNS can be used, several conditions must be met: 1. Scavenging and aging must be enabled both at the DNS server and on the zone. By default, aging and scavenging of resource records is disabled. 2. Resource records must either be dynamically added to zones or manually modified to be
•:
•
The date and time when the record was last refreshed and its time stamp set.
•:
•
When a computer is restarted on the network and, if at startup, its name and IP address information are consistent with the same name and address information it used prior to being shut down, it sends a refresh to renew its associated resource records for this information.
• •.
•:
•
When a new computer is added to the network and, at startup, it sends an update to register its resource records for the first time with its configured zone.
•
When a computer with existing records in the zone has a change in IP address, causing updates to be sent for its revised name-to-address mappings in DNS zone data.
•
When the Net Logon service registers a new Active Directory domain controller.
Refresh interval An interval of time, determined for each zone, as bounded by the following two distinct events:
• •:
• •
Dynamic updates are enabled for the zone. A change in the state of the Scavenge stale resource records check box is applied. You can use the DNS console to modify this setting at either an applicable DNS server or one of its primary zones.
•
The DNS server loads a primary zone enabled to use scavenging. This can occur when the server computer is started or when the DNS Server service is started.
•. 1. A sample DNS host, “host-a.example.microsoft.com”, registers its host (A) resource record at the DNS server for a zone where aging/scavenging is enabled for use. 2.. 3.. 4. During and after the refresh period, if the server receives a refresh for the record, it processes it. This resets the time stamp for the record based on the method described in step 2.
5.
•
If the value of this sum is greater than current server time, no action is taken and the record continues to age in the zone.
•
If:
• •:
• •
Any binary string can be used in a DNS name. (RFC 2181) DNS servers must be able to compare names in a case-insensitive way. (RFC 1035)
•:
• •:
•.
• • •.
•
•. In general, all DNS queries are sent from a high-numbered source port (above 1023) to destination port 53, and responses are sent from source port 53 to a high-numbered destination port. The following table lists the UDP and TCP ports used for different DNS message types. UDP and TCP Port Assignments for DNS Servers
Traffic Type Queries from local DNS server Responses to local DNS server Queries from remote DNS server Responses to remote DNS server Note
Source of Transmission Local DNS server Any remote DNS server Any remote DNS server Local DNS server
Source Port Any port number above 1023 53 Any port number above 1023 53
Destination of Transmission Any remote DNS server Local DNS server Local DNS server Any remote DNS server
Destination Port 53 Any port number above 1023 53 Any port number above 1023
• and scales its response to contain as many resource records as are allowed in the maximum UDP packet size specified by the requestor.
•
Windows Server 2003 DNS support for EDNS0 is enabled by default. It can be disabled using the registry. Locate the following registry subkey:
• •
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\DNS\Parameters Add the entry EnableEDNSProbes to the subkey. Give the entry a DWORD value and set it to 0x0 to disable EDNS0.
•
Use extreme caution when editing the registry Modifications to the registry are not validated by the registry editor or by Windows before they are applied, and as a result, incorrect values can be stored. This can result in unrecoverable errors in the system..
• • • • • • • • • • • •:
• • • •)
•.
•
•
Field Owner Time to Live (TTL)
Description Indicates the DNS domain name that owns a resource record. This name is the same as that of the console tree node where a resource record is located. For most resource records, this field is optional. resource record examples below, the TTL field is omitted wherever it is optional. The TTL field is included in the syntax for each record to indicate where it may be added. Contains standard mnemonic text indicating the class of the resource record. For example, a setting of “IN” indicates that the resource record belongs to the Internet class, which is the only class supported by Windows Server 2003 DNS. This field is required. Contains standard mnemonic text indicating the type of resource record. For example, a mnemonic of “A” indicates that the resource record stores host address information. This field is required. A required, variable-length field that contains information describing the resource. The format of this information varies according to the type and class of the resource record.
Class
Type Recordspecific data
DNS Resource Records (Alphabetical List) A
Description: Host address (A) resource record. Maps a DNS domain name to an Internet Protocol (IP) version 4 32-bit
address. For more information, see RFC 1035. Syntax:: owner class ttl A IP_v4_address Example: Copy Code
host1.example.microsoft.com.
AAAA
IN A 127.0.0.1
Description: IPv6 host address (AAAA) resource record. Maps a DNS domain name to an Internet Protocol (IP) version 6 128-bit address. For more information, see RFC 1886. Syntax: owner class ttl AAAA IP_v6_address Example: Copy Code
ipv6_host1.example.microsoft.com.
AFSDB
IN AAAA 4321:0:1:2:3:4:567:89ab:
• •
A value of 1 to indicate that the server is an AFS version 3.0 volume location server for the named AFS cell. A value of 2 to indicate that the server is an authenticated name server holding the cell-root directory node for
the server that uses either Open Software Foundation’s (OSF) DCE authenticated cell-naming system or HP/Apollo’s Network Computing Architecture (NCA). For more information, see RFC 1183. Syntax:: owner ttl class AFSDB subtype server_host_name Example: Copy Code
example.microsoft.com.
ATMA
AFSDB
1 afs-server1.example.microsoft.com.. Syntax: owner ttl class ATMA atm_address Example: Copy Code
atm-host
CNAME
ATMA
47.0079.00010200000000000000.00a03e000002.00. Syntax: owner ttl class CNAME canonical_name Example: Copy Code
aliasname.example.microsoft.com.
HINFO
CNAME
truename.example.microsoft.com.
Description: Host. Syntax: owner ttl class HINFO cpu_type os_type Example: Copy Code
my-computer-name.example.microsoft.com.
ISDN
HINFO
INTEL-386 WIN32. Syntax: owner ttl class ISDN isdn_address sub_address Example: Copy Code
my-isdn-host.example.microsoft.com.
KEY
ISDN
141555555539699 002
Description: Public key resource record. Contains a public key that is associated with a zone. In full then retrieve the zone’s KEY record. For more information, see RFC 2535. Syntax: owner class KEY protocol digital_signature_algorithm (DSA) public_key Example: Copy Code. Syntax: owner ttl class MINFO responsible_mailbox error_mailbox
Example: Copy Code
administrator.example.microsoft.com. mbox.example.microsoft.com
MX
MINFO resp-mbox.example.microsoft.com err-. Syntax: owner ttl class MX preference mail_exchanger_host Example: Copy Code
example.microsoft.com. MX 10 mailserver1.example.microsoft.com
NS
Description: Used to map a DNS domain name as specified in owner to the name of hosts operating DNS servers specified in the name_server_domain_name field. Syntax: owner ttl IN NS name_server_domain_name Example: Copy Code
example.microsoft.com.
NXT
IN NS nameserver1.example.microsoft.com
Description: Next resource record. NXT resource records indicate the nonexistence of a name in a zone by creating a chain of all of the literal owner names in that zone. They also indicate what resource record types are present for an existing name. For more information, see RFC 2535. Syntax: owner class NXT next_domain_name last_record_type NXT Example: Copy Code
east.widgets.microsoft.com. IN NXT. A NXT
OPT
Description: Option. Syntax: name OPT class ttl rdlen rdata Example: Copy Code. Syntax: owner ttl class PTR targeted_domain_name Example: Copy Code
1.0.0.10.in-addr.arpa.
RP
PTR host.example.microsoft.com.. Syntax: owner ttl class RP mailbox_name text_record_name Example: Copy Code
example.microsoft.com. RP admin.example.microsoft.com. admin-info.example.microsoft.com. admin-info.example.microsoft.com. TXT “Joe Administrator, (555) 555-0110”
SIG
Description: Signature resource record. Encrypts an RRset to a signer’s (RRset’s zone owner) domain name and a validity interval. For more information, see RFC 2535. Syntax: owner class SIG ttl signature_expiration signature_inception key_identifier signer_name{digital_signature} Example: Copy Code example below, the owner (primary DNS server) is specified as “@” because the domain name is the same as the origin of all data in the zone (example.microsoft.com.). This is a standard notation convention for resource records and is most often seen in the SOA record. Syntax: owner class SOA name_server responsible_person (serial_number refresh_interval retry_interval expiration minimum_time_to_live)
Example: Copy Code
@ 2003 DNS, it provides the meanspreferred. For more information, see the Internet draft “A DNS RR for specifying the location of services (DNS SRV).” Syntax: service.protocol.name ttl class SRV preference weight port target Example: Copy. Syntax: owner ttl class TXT text_string Example: Copy Code
example.microsoft.com. information.”
WKS
TXT
“This is an example of additional domain name. Syntax: owner ttl class WKS address protocol service_list Example: Copy Code
example.microsoft.com.
X25
WKS 10.0.0.1 TCP ( telnet smtp ftp ). Syntax: owner ttl class X25 psdn_number Example: Copy Code
example.microsoft.com.
X25 52204455506
Event ID 2
Description The DNS server has started. This message generally appears at startup when either the server computer is started or the DNS Server service is manually started. The DNS server has shut down. This message generally appears when either the server computer is shut down or the DNS Server service is stopped manually. The DNS server could not open.
3
408
413
Typically, limiting the DNS server to using only its configured DNS port for sending queries to other DNS servers is the response to this event. This configuration is performed using the DNS console’s server properties Interfaces tab as follows:
1.
Either select All IP addresses to enable the DNS server to listen on all configured server IP
addresses
2.
Or, if you continue to select and use Only the following IP addresses, limit the IP address
list to a single server IP address.
414
The. In general, the DNS server should be reconfigured with a full DNS computer name appropriate for its domain or workgroup use on your network. The DNS server did not detect any zones of either primary or secondary type. It will run as a caching-only server but will not be authoritative for any zones. The DNS server wrote a new version of zone zonename to file filename. You can view the new version number in the DNS manager Zone Properties dialog box, Serial Number field. This event should only appear if the DNS server is configured to operate as a root server. Zone zonename expired before it could obtain a successful zone transfer or update from a master server acting as its source for the zone. The zone has been shut down. This event ID might appear when the DNS server is configured to host a secondary copy of the zone from another DNS server acting as its source or master server. It is always a good practice to verify that this server has network connectivity to its configured master server. If the problem were to continue, one or more of the following options is avaialble: 1. Delete the zone and recreate it, specifying either a different master server, or an updated and
708 3150
6527
corrected IP address for the same master server. 2. If zone expiration continues, consider adjusting the expire interval. | https://www.scribd.com/document/29161826/How-DNS-Works | CC-MAIN-2018-13 | refinedweb | 10,607 | 52.7 |
As the title states I am trying to use the previous rank to filter out the current
Here’s an example of my starting df
df = pd.DataFrame({ 'rank': [1, 1, 2, 2, 3, 3], 'x': [0, 3, 0, 3, 4, 2], 'y': [0, 4, 0, 4, 5, 5], 'z': [1, 3, 1.2, 2.95, 3, 6], }) print(df) # rank x y z # 0 1 0 0 1.00 # 1 1 3 4 3.00 # 2 2 0 0 1.20 # 3 2 3 4 2.95 # 4 3 4 5 3.00 # 5 3 2 5 6.00
Here’s what I want the output to be
output = pd.DataFrame({ 'rank': [1, 1, 2, 3], 'x': [0, 3, 0, 2], 'y': [0, 4, 0, 5], 'z': [1, 3, 1.2, 6], }) print(output) # rank x y z # 0 1 0 0 1.0 # 1 1 3 4 3.0 # 2 2 0 0 1.2 # 5 3 2 5 6.00
basically what I want to happen is if the previous rank has any rows with x, y (+- 1 both ways) AND z (+- .1) to remove it.
So for the rows rank 1 ANY rows in rank 2 that have any combo of x = (-1-1), y = (-1-1), z= (.9-1.1) OR x = (2-5), y = (3-5), z= (2.9-3.1) I want it to be removed
Thanks for all help in advance!
Answer
This is a bit tricky as your need to access the previous group. You can compute the groups using
groupby first, and then iterate over the elements and perform your check with a custom function:
def check_previous_group(rank, d, groups): if not rank-1 in groups.groups: # check is a previous group exists, else flag all rows False (i.e. not to be dropped) return pd.Series(False, index=d1.index) else: # get previous group (rank-1) d_prev = groups.get_group(rank-1) # get the absolute difference per row with the whole dataset # of the previous group: abs(d_prev-s) # if all differences are within 1/1/0.1 for x/y/z # for at least one rows of the previous group # then flag the row to be dropped (True) return d.apply(lambda s: abs(d_prev-s)[['x', 'y', 'z']].le([1,1,0.1]).all(1).any(), axis=1) groups = df.groupby('rank') mask = pd.concat([check_previous_group(rank, d, groups) for rank,d in groups]) df[~mask]
output:
rank x y z 0 1 0 0 1.0 1 1 3 4 3.0 2 2 0 0 1.2 5 3 2 5 6.0 | https://www.tutorialguruji.com/python/pandas-using-the-previous-rank-values-to-filter-out-current-row/ | CC-MAIN-2021-43 | refinedweb | 437 | 94.05 |
Language Bindings for the C++ API: Mid-term Report and Third Quarter Goals
The following objects have at least partial bindings:
At the moment, some of the classes are not very usable; they’re necessary because other objects inherit from them. They will later be expanded to allow creation of custom objects based on them, so users could subclass a Looper or a View the same way they can now subclass Application and Window.
Python has a minimal test program that uses Application, Window, and Button, but the other objects have not been tested. It would be helpful if interested Python programmers could start coding (and thereby discovering bugs). In addition, I get a large number of warnings about multi-character constants when compiling. Despite following the instructions in the documentation, I cannot get the installer to pass options to the compiler to turn these off. There are also a few other warnings I’m working on eliminating, but the extensions successfully compile and the test program works.
For the time being, the Python objects are all named Haiku.
Object instead of Haiku.
Kit.
Object. This allows me to split up the kits into different extensions; since an extension does not know what kit a foreign object is defined in, the kit name cannot be part of the object name. Since this naming scheme is apparently not good Python practice, I am still looking into alternatives; currently I am considering either placing everything into a single extension or adding some data to my definition files that lets an extension know what kit/extension a foreign object belongs to.
Perl has the minimal test program and it also has a slightly more complex test program (a small Person viewer app). There are also a few compiler warnings I’m still working on eliminating.
The bindings can be found at. The downloadable files are under “Files”; there are also Forums and a Wiki, and (under “Issues”) a bug tracker. Anyone can download the files and look at the content, but if you want to report bugs, post to the forums, or edit the wiki, you need to be added to the project. Interested users with an OsDrawer.net account can email me or post a comment here, and I will add you as a member of the project.
There may be some trial and error involved in adding members; OsDrawer.net has defined some roles for members of a project, but I can’t find any documentation on what permissions each role has. There is a role called “Reporter” that I assume lets the user post new bugs, and there’s one called “Wiki editor” that’s self-explanatory. But there’s no role for Forum poster, so I assume one or more of the other roles has that permission included. But I don’t know which one(s).
Okay, let’s take a look at my second-quarter goals:
- Bring the Python bindings to minimal functionality (Done)
- Write a minimal Python test program (Done)
- Continue to test threading issues (See below)
- Expand preliminary bindings and add new bindings (Done)
- Write test programs for the bindings (Partially done)
- Write documentation for the bindings (See below)
- If there is sufficient time, select a third target language (Insufficient time)
Threading: I have found several issues I thought might be threading issues, but upon closer examination, they were not. I did find one genuine threading issue - but it was because I forgot to lock a window before updating data.
Documentation: I have written some documentation and I am working on programmatically adding it to the bindings. Python has fields in the underlying C++ structures to add documentation, and Perl allows documentation to be mixed in with the code.
Now for my upcoming goals. In general, during the next quarter I will continue to keep an eye out for threading issues, add new bindings, and fix reported bugs. There are also a few more specific things I want to work on:
There are a number of methods that haven’t been implemented yet because they have structs as input or output, and the bindings do not handle structs yet. It should not be too difficult to map these to appropriate data types in the target language (Perl hash, Python dictionary).
I’m not sure what to do about globals like
be_app and
be_clipboard; on the one hand, they could be treated like constants and restricted to a particular namespace, in order to not pollute the global namespace. This is the way I’m leaning right now. On the other hand, there are relatively few of them, and so it would probably not result in a great deal of pollution if I were to put them in the global namespace.
Several of the C++ objects have overloaded operators. I would like to expand the bindings to support these overloaded operators. I’m not sure how much time I want to spend on this issue right now, though. It depends on how much users want this feature.
- Continue to test threading issues
- Expand existing bindings and add new bindings
- Fix bugs reported by users
- Enable structs
- Expose globals
- Add documentation
- Write additional and more complex test programs
- If there is sufficient time, select a third target language
- If there is sufficient time and user interest, work on overloaded operators
Blog-O-Sphere
- [GSoC 2018 - TrackGit] Progress Report 6
- [GSoC 2018: SDHCI MMC Driver]: Week #5
- Haiku monthly activity report - 05/2018 (ft. LibreOffice!)
- [GSoC 2018: XFS support] Week #6
- [GSoC 2018 - TrackGit] Progress Report 5
- [GSoC 2018: SDHCI MMC Driver]: Week #4
- [GSoC 2018: SDHCI MMC Driver]: Week #3
- [GSoC 2018 - TrackGit] Progress Report 4
- [GSoC 2018 - TrackGit] Progress Report 3
- Rune - Haiku Images on ARM | https://www.haiku-os.org/blog/jalopeura/2011-07-09_language_bindings_c_api_midterm_report_and_third_quarter_goals | CC-MAIN-2018-26 | refinedweb | 958 | 56.18 |
Investors in iShares Inc. - iShares MSCI Canada ETF (Symbol: EWC) saw new options become available today, for the December 20th expiration. One of the key data points EWC options chain for the new December 20th contracts and identified one put and one call contract of particular interest.
The put contract at the $27.00 strike price has a current bid of 70 cents. If an investor was to sell-to-open that put contract, they are committing to purchase the stock at $27.00, but will also collect the premium, putting the cost basis of the shares at $26.30 (before broker commissions). To an investor already interested in purchasing shares of EWC, that could represent an attractive alternative to paying $28.34/share today.
Because the $27.59% return on the cash commitment, or 3.98% annualized — at Stock Options Channel we call this the YieldBoost.
Below is a chart showing the trailing twelve month trading history for iShares Inc. - iShares MSCI Canada ETF, and highlighting in green where the $27.00 strike is located relative to that history:
Turning to the calls side of the option chain, the call contract at the $29.00 strike price has a current bid of 65 cents. If an investor was to purchase shares of EWC stock at the current price level of $28.34/share, and then sell-to-open that call contract as a "covered call," they are committing to sell the stock at $29.00. Considering the call seller will also collect the premium, that would drive a total return (excluding dividends, if any) of 4.62% if the stock gets called away at the December 20th expiration (before broker commissions). Of course, a lot of upside could potentially be left on the table if EWC shares really soar, which is why looking at the trailing twelve month trading history for iShares Inc. - iShares MSCI Canada ETF, as well as studying the business fundamentals becomes important. Below is a chart showing EWC's trailing twelve month trading history, with the $29.00 strike highlighted in red:
Considering the fact that the .29% boost of extra return to the investor, or 3.52% annualized, which we refer to as the YieldBoost.
The implied volatility in the put contract example is 23%, while the implied volatility in the call contract example is 16%.
Meanwhile, we calculate the actual trailing twelve month volatility (considering the last 251 trading day closing values as well as today's price of $28.34) to be 14%. For more put and call options contract ideas worth looking at, visit StockOptionsChannel.com.
Top YieldBoost Calls of the S&P 500 » | https://www.nasdaq.com/articles/ewc-december-20th-options-begin-trading-2019-04-26 | CC-MAIN-2020-16 | refinedweb | 443 | 66.23 |
Planning Council/December 01 2010
< Planning Council
Revision as of 18:38, 29 November 2010 by David williams.acm.org (Talk | contribs) (→Indigo Plan and Schedule)
Contents
Logistics
Attendees
Inactive
Announcements
- ?
Maintenance Schedule
Helios SR2
2/25/2011 (Fourth Friday of February)
For detailed RC schedules, see Service Release Schedule in master plan
Indigo Status
- nearing M4. Is everyone one? Any known exceptions?
Indigo Plan and Schedule
- Discuss "namespace" issues discussed in bug 330312 and elsewhere.
- Discuss issue (from last year) ... to what extent should Sim. Rel. materials (checklist) be part of official release docuware.
- Suggestions during (previous) meeting:
- The req. doc was deemed?
- Discussed "once in always in".
- | http://wiki.eclipse.org/index.php?title=Planning_Council/December_01_2010&oldid=230023 | CC-MAIN-2018-09 | refinedweb | 109 | 54.29 |
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#!
# This is statement is required by the build system to query build info
if __name__ == '__build__':
raise Exception
import string
__version__ = string.split('$Revision: 1.1.1.1 $')[1]
__date__ = string.join(string.split('$Date: 2007/02/15 19:25:21 $')[1:3], ' ')
__author__ = 'Tarn Weisner Burton <twburton@users.sourceforge.net>'
#
# Ported to PyOpenGL 2.0 by Tarn Weisner Burton 10May2001
# This code was created by Richard Campbell '99 (ported to Python/PyOpenGL by John Ferguson 2000)
# The port was based on the lesson5 tutorial module by Tony Colston (tonetheman@hotmail.com).
# If you've found this code useful, please let me know (email John Ferguson at hakuin@voicenet.com).
# See original source and C based tutorial at http:#nehe.gamedev.net
# Note:
# -----
# Now, I assume you've read the prior tutorial notes and know the deal here. The one major, new requirement
# is to have a working version of PIL (Python Image Library) on your machine.
# General Users:
# --------------
# I think to use textures at all you need Nunmeric Python, I tried without it and BAM Python didn't "like" the texture API.
# Win32 Users:
# ------------
# Well, here's the install I used to get it working:
# [1] py152.exe - include the TCL install!
# [2] PyOpenGL.EXE - probably the latest, the Vaults notes should give you a clue.
# [3] Distutils-0.9.win32.exe for step #4
# [4] Numerical-15.3.tgz - run the setup.py (need VC++ on your machine, otherwise, have fun with #3, it looks fixable to use gCC).
# Win98 users (yes Win98, I have Mandrake on the other partition okay?), you need to the Tcl bin directory in your PATH, not PYTHONPATH,
# just the DOS PATH.
# BTW, since this is Python make sure you use tabs or spaces to indent, I had numerous problems since I
# was using editors that were not sensitive to Python.
from OpenGL.GL import *
from OpenGL.GLUT import *
from OpenGL.GLU import *
import sys
from Image import *
# Some api in the chain is translating the keystrokes to this octal string
# so instead of saying: ESCAPE = 27, we use the following.
ESCAPE = '\033'
# Number of the glut window.
window = 0
# Rotations for cube.
xrot = yrot = zrot = 0.0
texture = 0
def LoadTextures():
#global texture
image = open("NeHe.bmp")
ix = image.size[0]
iy = image.size[1]
image = image.tostring("raw", "RGBX", 0, -1)
# Create Texture
glBindTexture(GL_TEXTURE_2D, glGenTextures(1)) # 2d texture (x and y size)
glPixelStorei(GL_UNPACK_ALIGNMENT,1)
glTexImage2D(GL_TEXTURE_2D, 0, 3, ix, iy, 0, GL_RGBA, GL_UNSIGNED_BYTE, image)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP)
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP))
# A general OpenGL initialization function. Sets all of the initial parameters.
def InitGL(Width, Height): # We call this right after our OpenGL window is created.
LoadTextures()
glEnable(GL_TEXTURE_2D)
glClearColor(0.0, 0.0, 0.0, 0.0) #
# Calculate The Aspect Ratio Of The Window
gluPerspective(45.0, float(Width)/float(Height), 0.1, 100.0)
glMatrixMode(GL_MODELVIEW)
# The function called when our window is resized (which shouldn't happen if you enable fullscreen, below)
def ReSizeGLScene(Width, Height):
if Height == 0: # Prevent A Divide By Zero If The Window Is Too Small
Height = 1
glViewport(0, 0, Width, Height) # Reset The Current Viewport And Perspective Transformation
glLoadIdentity()
# The main drawing function.
def DrawGLScene():
global xrot, yrot, zrot, texture
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT) # Clear The Screen And The Depth Buffer
glLoadIdentity() # Reset The View
glTranslatef(0.0,0.0,-5.0) # Move Into The Screen
glRotatef(xrot,1.0,0.0,0.0) # Rotate The Cube On It's X Axis
glRotatef(yrot,0.0,1.0,0.0) # Rotate The Cube On It's Y Axis
glRotatef(zrot,0.0,0.0,1.0) # Rotate The Cube On It's Z Axis
# Note there does not seem to be support for this call.
#glBindTexture(GL_TEXTURE_2D,texture) # Rotate The Pyramid On It's Y Axis
glBegin(GL_QUADS) # Start Drawing The Cube
# Front Face (note that the texture's corners have to match the quad's corners)
# Back Face
# Top Face
# Bottom Face
# Right face
glTexCoord2f(1.0, 0.0); glVertex3f( 1.0, -1.0, -1.0) # Bottom Right Of The Texture and Quad
glTexCoord2f(0.0, 1.0); glVertex3f( 1.0, 1.0, 1.0) # Top Left Of The Texture and Quad
# Left Face
glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, -1.0, -1.0) # Bottom Left Of The Texture and Quad
glTexCoord2f(1.0, 1.0); glVertex3f(-1.0, 1.0, 1.0) # Top Right Of The Texture and Quad
glEnd(); # Done Drawing The Cube
xrot = xrot + 0.2 # X rotation
yrot = yrot + 0.2 # Y rotation
zrot = zrot + 0.2 # Z rotation
# since this is double buffered, swap the buffers to display what just got drawn.
glutSwapBuffers()
# The function called whenever a key is pressed. Note the use of Python tuples to pass in: (key, x, y)
def keyPressed(*args):
# If escape is pressed, kill everything.
if args[0] == ESCAPE:
sys.exit()
def main():
global window
glutInit(sys.argv)
# Select type of Display mode:
# Double buffer
# RGBA color
# Alpha components supported
# Depth buffer
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH)
# get a 640 x 480 window
glutInitWindowSize(640, 480)
# the window starts at the upper left corner of the screen
glutInitWindowPosition(0, 0)
# Okay, like the C version we retain the window id to use when closing, but for those of you new
# to Python (like myself), remember this assignment would make the variable local and not global
# if it weren't for the global declaration at the start of main.
window = glutCreateWindow("Jeff Molofee's GL Code Tutorial ... NeHe '99")
# Register the drawing function with glut, BUT in Python land, at least using PyOpenGL, we need to
# set the function pointer and invoke a function to actually register the callback, otherwise it
# would be very much like the C version of the code.
glutDisplayFunc(DrawGLScene)
# Uncomment this line to get full screen.
# glutFullScreen()
# When we are doing nothing, redraw the scene.
glutIdleFunc(DrawGLScene)
# Register the function called when our window is resized.
glutReshapeFunc(ReSizeGLScene)
# Register the function called when the keyboard is pressed.
glutKeyboardFunc(keyPressed)
# Initialize our window.
InitGL(640, 480)
# Start Event Processing Engine
glutMainLoop()
# Print message to console, and kick off the main to get it rolling.
print "Hit ESC key to quit."
main() | http://forge.cbp.ens-lyon.fr/redmine/projects/pyopengl4dummies/repository/revisions/1/entry/PyOpenGL-Demo/NeHe/lesson6.py | CC-MAIN-2020-34 | refinedweb | 1,045 | 57.87 |
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
TextIO.putln("Hello World!");
TextIO.putln("What is your age?");
int age = TextIO.getInt();
TextIO.getInt();
TextIO.put("Your age is ");
TextIO.putInt(age);
}
}
This was really my first attempt at problem solving in java and I hope it wasn't to painful for those of you that helped! So thanks and bear with my posts in the future!
I am using Eclipse and missed the what should have been obvious reminder about the syntax error.
Mansukhdeep Thind wrote:
I am using Eclipse and missed the what should have been obvious reminder about the syntax error.
If these are the first few of your tryouts at writing Java code, as you said, then my suggestion would be get rid of the IDE for now. Use a simple text editor to write the code yourself. Starting from package statements to imports, defining classes, methods instance variables etc. The reason is IDEs like Eclipse assist you with many things. So, you will never fully understand what is really happening under the hood. Write the code yourself in the editor, compile it and run from the command prompt. Make mistakes and get your hands dirty. Then you can home in on the exceptions and errors. It will not only teach you Java coding as such, but many other things that are a must know for a novice like classpaths, jar file issues etc.. Which book are you referring to by the way?
I like the writing. Seems straight forward without talking down to me. Get what I mean?
I'd like to find an IDE that is more lightweight than Eclipse to run on my slow netbook. Any suggestions?
Campbell Ritchie wrote:Probably better to go back to the command line.
Campbell Ritchie wrote:you have to put so much effort into learning the IDE, which would be better used for learning Java
Jayeemsuh Allen wrote:I checked out both DrJava and JEdit and I'm going to give DrJava a try for a little while.
That's all "noname" IDEs to me. I've never used any of these before and didn't even hear any suggestions to start using it.
If you plan to start with IDE, it would be wiser to invest your time in learning popular and proven IDE.
surlac surlacovich wrote: . . . Is it really needs to be double instead of float, int instead of short (byte)? . . .
surlac surlacovich wrote: . . . Can you opt out of TextIO custom class, to make folks from the ranch understand the code?
Personally I like to stick to standard APIs to show the code (otherwise dependent I need to share dependent classes).
Agree it would be better to write your own utility class for text input and simply use System.out and System.err for output
That is not at all a good suggestion; floating‑point arithmetic is done with doubles as a default and integer arithmetic with ints. In the days when memory was expensive, it might have been worth being economical with it, but that has not been the case for, probably, twenty years. | http://coderanch.com/t/606909/java/java/TextIO-getInt-simple-age-program | CC-MAIN-2015-22 | refinedweb | 525 | 74.29 |
Created on 2019-12-20 08:56 by xtreak, last changed 2020-12-11 19:59 by paul.j3. This issue is now closed.
I came across this idea while working on error messages for click at. Currently for unknown arguments which could in some case be typos argparse throws an error but doesn't make any suggestions. It could do some heuristic to suggest matches. The unrecognized argument error prints all unrecognized arguments so in that case it will be less useful to mix match suggestions. It can be helpful for single argument usages. argparse is performance sensitive since it's used in cli environments so I feel the tradeoff to do simple match to make suggestions as a good user experience.
# ssl_helper.py
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--include-ssl', action='store_true')
namespace = parser.parse_args()
No suggestions are included currently
$ python3.8 ssl_helper.py --include-ssll
usage: ssl_helper.py [-h] [--include-ssl]
ssl_helper.py: error: unrecognized arguments: --include-ssll
Include suggestions based when one of the option starts with the argument supplied similar to click
$ ./python.exe ssl_helper.py --include-ssll
usage: ssl_helper.py [-h] [--include-ssl]
ssl_helper.py: error: unrecognized argument: --include-ssll . Did you mean --include-ssl?
difflib.get_close_matches could also provide better suggestions in some cases but comes at import cost and could be imported only during error messages as proposed in the click issue
./python.exe ssl_helper.py --exclude-ssl
usage: ssl_helper.py [-h] [--include-ssl]
ssl_helper.py: error: unrecognized argument: --exclude-ssl . Did you mean --include-ssl?
Attached is a simple patch of the implementation with startswith which is more simple and difflib.get_close_matches
diff --git Lib/argparse.py Lib/argparse.py
index 5d3ce2ad70..e10a4f0c9b 100644
--- Lib/argparse.py
+++ Lib/argparse.py
@@ -1818,8 +1818,29 @@ class ArgumentParser(_AttributeHolder, _ActionsContainer):
def parse_args(self, args=None, namespace=None):
args, argv = self.parse_known_args(args, namespace)
if argv:
- msg = _('unrecognized arguments: %s')
- self.error(msg % ' '.join(argv))
+ suggestion = None
+ if len(argv) == 1:
+ argument = argv[0]
+
+ # simple startswith
+ for option in self._option_string_actions:
+ if argument.startswith(option):
+ suggestion = option
+ break
+
+ # difflib impl
+ import difflib
+ try:
+ suggestion = difflib.get_close_matches(argv[0], self._option_string_actions, n=1)[0]
+ except IndexError:
+ pass
+
+ if suggestion:
+ msg = _('unrecognized argument: %s . Did you mean %s?')
+ self.error(msg % (' '.join(argv), suggestion))
+ else:
+ msg = _('unrecognized arguments: %s')
+ self.error(msg % ' '.join(argv))
return args
def parse_known_args(self, args=None, namespace=None):
-1 Given an unknown argument, we really can't know what the user intended. The usage string already lists all available options and -h --help gives more detail when requested.
I checked some other common clis and it is show all right available options too. So I thought the argparse's help function is good enough too ;)
```
$ ps -etest
error: TTY could not be found
Usage:
ps [options]
Try 'ps --help <simple|list|output|threads|misc|all>'
or 'ps --help <s|l|o|t|m|a>'
for additional help text.
For more details see ps(1).
```
```
$ top test
top: unknown option 't'
Usage:
top -hv | -bcHiOSs -d secs -n max -u|U user -p pid(s) -o field -w [cols]
```
Thanks for the feedback. Closing it as rejected.
I don't think this should have been closed.
[1] If the user is using sub_parser, the options are not even displayed. For example in our project:
```
$ tfds build mnist --overwritte
usage: tfds [-h] [--helpfull] [--version] {build,new} ...
tfds: error: unrecognized arguments: --overwritte
```
[2] For some programs, there can be 20+ options and having to scroll through the list is not user friendly at all.
[3] Other CLI, like Google absl.flags has this option too and it is very convenient.
In the subparser example, it's the `build` subparser that puts '--overwritte' in the unrecognized list. That is then passed back to the main parser, which then issues the 'unrecognized' error, along with its own usage.
The subparser is called with `parse_known_args` while the proposed patch is run in the `parse_args` method of the main parser. It doesn't have access to the subparser's arguments. So implementing the proposed matching will be much harder.
For some types of error, such as type or choices, the subparser itself raises the error, with the appropriate usage.
===
[argparse] Bad error message formatting when using custom usage text
is another case where error messages produced by the subparser differ from messages produced by the main. In this case the unrecognized error usage message is clearer since it is produced by the main parser.
===
I didn't close this issue, but it does feel like an enhancement that's too big for the bug/issues forum. The proposed patch could be developed as a separate 'parser.parse_args_with_hints' method, and distributed as a pypi addition. During development and testing, the regular 'parser.parse_args()' does not need to be touched. | https://bugs.python.org/issue39106 | CC-MAIN-2021-17 | refinedweb | 805 | 59.9 |
I’m trying to show looped videos with MovieStim3, and I have noticed that the video lags when it loops.
It probably has something to do with
seek(0) at the begining of the loop - ffmpeg is slow at seeking particular frames. Is there a workaround?
Below is the code example and frame intervals plot with highlighted lags.
psychopy 2020.1.2, pyglet 1.5
Win10x64, nvidia gtx1050. Python runs on Nvidia graphics card, Vsync on
import sys from psychopy import visual, core, event, data, gui,logging, prefs from matplotlib import pyplot as plt win = visual.Window(fullscr=True, rgb='black', size=[1920,1080], winType='pyglet') win.recordFrameIntervals = True video = visual.MovieStim3(win, filename=r"./video.mp4", loop=True, noAudio=True) while 1: if 'escape' in event.getKeys(): win.close() plt.plot(win.frameIntervals, 'o') plt.show() sys.exit() video.draw() # draw other irrelevant stuff win.flip()
video used: | https://discourse.psychopy.org/t/moviestim3-looped-video-lags/11548 | CC-MAIN-2021-39 | refinedweb | 149 | 62.14 |
The following figure illustrates the most common thread states, and what happens to move a thread into each state
Here a list of all the available thread states
Taken from the MSDN ThreadState page
In this section I will include some code that examines some of threading areas mentioned above. I will not cover all of them, but I'll try and cover most of them.
The
Join method (without any parameters) blocks the calling thread until the current thread
is terminated. It should be noted that the caller will block indefinitely if
the current thread does not terminate. If the thread has already terminated
when
Join method is called, the method returns immediately.
The
Join method has an override, which lets you set the number of
milliseconds to wait on the thread to finish. If thread has not
finished when the timer expires,
Join exits and returns control to the
calling thread (and the joined thread continues to execute).
This method changes the state of the calling thread to include
WaitSleepJoin
(according to the MSDN documentation)
This method is quite useful if one thread depends on another thread.
Let see a small example (attached demo ThreadJoin project)
In this small example we have 2 threads, I want the 1st thread to run first
and the second thread to run after the 1st thread is completed.
using System; using System.Threading; namespace ThreadJoin { class Program { public static Thread T1; public static Thread T2; public static void Main(string[] args) { T1 = new Thread(new ThreadStart(First)); T2 = new Thread(new ThreadStart(Second)); T1.Name = "T1"; T2.Name = "T2"; T1.Start(); T2.Start(); Console.ReadLine(); } //thread T1 threadStart private static void First() { for (int i = 0; i < 5; i++) { Console.WriteLine( "T1 state [{0}], T1 showing {1}", T1.ThreadState, i.ToString()); } } //thread T2 threadStart private static void Second() { //what the state of both threads Console.WriteLine( "T2 state [{0}] just about to Join, T1 state [{1}], CurrentThreadName={2}", T2.ThreadState, T1.ThreadState, Thread.CurrentThread.Name); //join T1 T1.Join(); Console.WriteLine( "T2 state [{0}] T2 just joined T1, T1 state [{1}], CurrentThreadName={2}", T2.ThreadState, T1.ThreadState, Thread.CurrentThread.Name); for (int i = 5; i < 10; i++) { Console.WriteLine( "T2 state [{0}], T1 state [{1}], CurrentThreadName={2} showing {3}", T2.ThreadState, T1.ThreadState, Thread.CurrentThread.Name, i.ToString()); } Console.WriteLine( "T2 state [{0}], T1 state [{1}], CurrentThreadName={2}", T2.ThreadState, T1.ThreadState, Thread.CurrentThread.Name); } } }
And here is the output from this small program, where we can indeed see that thread T1 completes and then the thread T2 operations run.
Note : Thread T1 continues to run and then stops and then the operations that thread T2 specified are run.
Sleep
The static
Thread.Sleep method available on the
Thread
class is fairly simple, it simply Suspends the current thread for a specified
time. Consider the following example, where 2 threads are started that run 2
seperate counter methods, the 1st thread (T1) counts from 0-50 and the 2nd thread
(T2) counts from 51-100.
Thread T1 will go to sleep for 1 second when it reaches 10, and thread T2 will go to sleep for 5 seconds when it reaches 70.
Let see a small example (attached demo ThreadSleep project)
using System; using System.Threading; namespace ThreadSleep { class Program { public static Thread T1; public static Thread T2; public static void Main(string[] args) { Console.WriteLine("Enter Main method"); T1 = new Thread(new ThreadStart(Count1)); T2 = new Thread(new ThreadStart(Count2)); T1.Start(); T2.Start(); Console.WriteLine("Exit Main method"); Console.ReadLine(); } //thread T1 threadStart private static void Count1() { Console.WriteLine("Enter T1 counter"); for (int i = 0; i < 50; i++) { Console.Write(i + " "); if (i == 10) Thread.Sleep(1000); } Console.WriteLine("Exit T1 counter"); } //thread T2 threadStart private static void Count2() { Console.WriteLine("Enter T2 counter"); for (int i = 51; i < 100; i++) { Console.Write(i + " "); if (i == 70) Thread.Sleep(5000); } Console.WriteLine("Exit T2 counter"); } } }
The output may be as follows
In this example, thread T1 is run 1st, so starts its counter (as we will see
later, T1 may not necessarily be the thread to start 1st) and counts up to 10,
at which point T1 sleeps for 1 second and is placed in the
WaitSleepJoin
state. At this point T2 runs so starts its counter, gets to 70 and is put to
sleep (and is placed in the
WaitSleepJoin state) at which point
T1 is awoken and run to completion. T2 is then awoken and is able to complete
(as T1 has completed, so there is only T2 work left to do).
Interrupt
When a thread is put to sleep, the thread goes into the
WaitSleepJoin
state. If the thread is in this state it may be placed back in the scheduling
queue by the use of the
Interrupt method. Calling Interrupt when
a thread is in the
WaitSleepJoin state will cause a
ThreadInterruptedException
to be thrown, so any code that is written needs to catch this.
If this thread is not currently blocked in a wait, sleep, or join state, it
will be interrupted when it next begins to block.
Let see a small example (attached demo ThreadInterrupt project)
using System; using System.Threading; namespace ThreadInterrupt { class Program { public static Thread sleeper; public static Thread waker; public static void Main(string[] args) { Console.WriteLine("Enter Main method"); sleeper = new Thread(new ThreadStart(PutThreadToSleep)); waker = new Thread(new ThreadStart(WakeThread)); sleeper.Start(); waker.Start(); Console.WriteLine("Exiting Main method"); Console.ReadLine(); } //thread sleeper threadStart private static void PutThreadToSleep() { for (int i = 0; i < 50; i++) { Console.Write(i + " "); if (i == 10 || i == 20 || i == 30) { try { Console.WriteLine("Sleep, Going to sleep at {0}", i.ToString()); Thread.Sleep(20); } catch (ThreadInterruptedException e) { Console.WriteLine("Forcibly "); } Console.WriteLine("woken"); } } } //thread waker threadStart private static void WakeThread() { for (int i = 51; i < 100; i++) { Console.Write(i + " "); if (sleeper.ThreadState == ThreadState.WaitSleepJoin) { Console.WriteLine("Interrupting sleeper"); sleeper.Interrupt(); } } } } }
Which may produce this output
It can be seen from this output that the sleeper thread starts normally, and
when it gets to 10, is put to sleep so goes into the
WaitSleepJoin
state. Then the waker thread starts and immediately tries to
Interrupt
the sleeper (which is in the
WaitSleepJoin state, so the
ThreadInterruptedException
is thrown and caught). However as the initial sleeper threads sleep time elapses,
it is again allowed to run until completion.
I personally haven't really had to use the
Interrupt method that
often, but I do consider interrupting threads to be fairly dangerous, as you
just cant gaurentee where a thread is.
wasn't designed to be interrupted (with appropriate cleanup code in finally blocks) objects could be left in an unusable state, or resources incompletely released.
Interrupting a thread is safe when you know exactly where the thread is."
Threading in C#, Joseph Albahari.
Pause
There used to be a way to pause threads using the Pause() method. But this is now deprecated, so you must use alternative methods, such as WaitHandles. To demonstrate this there is a combined application that covers Pause/Resume and Abort of background threads
Resume
There used to be a way to pause threads using the Resume() method. But this is now deprecated, so you must use alternative methods, such as WaitHandles. To demonstrate this there is a combined application that covers Pause/Resume and Abort of background threads
Abort
First let me state that there is an Abort() method, but this is not something you should use likely (an in my own opinion at all). I would just like to first quote 2 reputable sources on the dangers of using the Abort() method
"A blocked thread can also be forcibly released via its Abort method. This has an effect similar to calling Interrupt, except that a ThreadAbortException is thrown instead of a ThreadInterruptedException. Furthermore, the exception will be re-thrown at the end of the catch block (in an attempt to terminate the thread for good) unless Thread.ResetAbort is called within the catch block. In the interim, the thread has a ThreadState of AbortRequested.
The big difference, though, between Interrupt and Abort, is what happens when it's called on a thread that is not blocked. While Interrupt waits until the thread next blocks before doing anything, Abort throws an exception on the thread right where it's executing – maybe not even in your code. Aborting a non-blocked thread can have significant consequences"
Threading in C#, Joseph Albahari.
"
A common question that emerges once you have kicked off some concurrent work is: how do I stop it? Here are two popular reasons for wanting to stop some work in progress:
You need to shut down the program. The user cancelled the operation.. "
How To Stop a Thread in .NET (and Why Thread.Abort is Evil), Ian Griffiths.
So with all this in mind, I have created a small application which I believe to be a well behaved worker thread, that allows the user to carry out some background work, and Pause/Resume and Cancel it, all safely and easily. Its not the only way to do this, but it's a way.
Let see a small example (attached demo ThreadResumePause_StopUsingEventArgs project)
Unfortunately I had to include some UI code here, to allow the user to click on different buttons for Pause/Resume etc etc, but I shall only include the parts of the UI code that I feel are relevant to explaining the subject
So first here is the worker thread class, one important thing to note is the usage of the
volatile keyword..
using System; using System.ComponentModel; using System.Threading; namespace ThreadResumePause_StopUsingEventArgs { public delegate void ReportWorkDoneEventhandler(object sender, WorkDoneCancelEventArgs e); /// <summary> /// This class provides a background worker that finds prime numbers, that /// are reported to the UI via the ReportWorkDone event. The UI may pause /// the worker by calling the Pause() method, and may resume the worker by /// calling the Resume() method. The UI may also cancel the worker by setting /// the ReportWorkDone events event args Cancel property to true. /// </summary> public class WorkerThread { private Thread worker; public event ReportWorkDoneEventhandler ReportWorkDone; private volatile bool cancel = false; private ManualResetEvent trigger = new ManualResetEvent(true); //ctor public WorkerThread() { } //Do the work, start the thread public void Start(long primeNumberLoopToFind) { worker = new Thread(new ParameterizedThreadStart(DoWork)); worker.Start(primeNumberLoopToFind); } //Thread start method private void DoWork(object data) { long primeNumberLoopToFind = (long)data; int divisorsFound = 0; int startDivisor = 1; for (int i = 0; i < primeNumberLoopToFind; i++) { //wait for trigger trigger.WaitOne(); divisorsFound = 0; startDivisor = 1; //check for prime numbers, and if we find one raise //the ReportWorkDone event while (startDivisor <= i) { if (i % startDivisor == 0) divisorsFound++; startDivisor++; } if (divisorsFound == 2) { WorkDoneCancelEventArgs e = new WorkDoneCancelEventArgs(i); OnReportWorkDone(e); cancel = e.Cancel; //check whether thread should carry on, //perhaps user cancelled it if (cancel) return; } } } /// <summary> /// make the worker thread wait on the ManualResetEvent /// </summary> public void Pause() { trigger.Reset(); } /// <summary> /// signal the worker thread, raise signal on /// the ManualResetEvent /// </summary> public void Resume() { trigger.Set(); } /// <summary> /// Raise the ReportWorkDone event /// </summary> protected virtual void OnReportWorkDone(WorkDoneCancelEventArgs e) { if (ReportWorkDone != null) { ReportWorkDone(this, e); } } } //Simple cancellable EventArgs, that also exposes //current prime number found to UI public class WorkDoneCancelEventArgs : CancelEventArgs { public int PrimeFound { get; private set; } public WorkDoneCancelEventArgs(int primeFound) { this.PrimeFound = primeFound; } } }
And here is the relevant parts of the UI code (Winforms C#). Note that I have not checked whether an Invoke is actually required before doing an Invoke.
MSDN says the following about the
Control.InvokeRequired Property :
Gets a value indicating whether the caller must call an invoke method when making method calls to the control because the caller is on a different thread than the one the control was created on..
So one could use this to determine if an
Invoke is actually required. Calling
InvokeRequired/Invoke/BeginInvoke/EndInvoke are all thread safe
using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Threading; namespace ThreadResumePause_StopUsingEventArgs { public partial class Form1 : Form { private WorkerThread wt = new WorkerThread(); private SynchronizationContext context; private bool primeThreadCancel = false; public Form1() { InitializeComponent(); //obtain the current SynchronizationContext context = SynchronizationContext.Current; } void wt_ReportWorkDone(object sender, WorkDoneCancelEventArgs e) { //+++++++++++++++++++++++++++++++++++++++++++++++++++++ //NOTE : This would also work to marshal call to UI thread //+++++++++++++++++++++++++++++++++++++++++++++++++++++ //this.Invoke(new EventHandler(delegate //{ // lstItems.Items.Add(e.PrimeFound.ToString()); //})); //marshal call to UI thread context.Post(new SendOrPostCallback(delegate(object state) { this.lstItems.Items.Add(e.PrimeFound.ToString()); }), null); //should worker thread be caneclled, has user clicked cancel button? e.Cancel = primeThreadCancel; } private void btnStart_Click(object sender, EventArgs e) { //start the worker and listen to its ReportWorkDone event wt.Start(100000); wt.ReportWorkDone += new ReportWorkDoneEventhandler(wt_ReportWorkDone); primeThreadCancel= false; } private void btnCancel_Click(object sender, EventArgs e) { primeThreadCancel= true; } private void btnPause_Click(object sender, EventArgs e) { wt.Pause(); } private void btnResume_Click(object sender, EventArgs e) { wt.Resume(); } } }
And when run this looks like this
So how does all this work. There are a few things in here that I has hoping not to get on to until part4, but there is simply no way they could be avoided so Ill try and cover them just enough. There are a couple of key concepts here, such as
I will try and explain each of these parts in turn
This is easily acheived by the use of a
ParameterizedThreadStart where you simply start the thread, passing in an input parameter like
worker.Start(primeNumberLoopToFind) and
then in the actual
private void DoWork(object data) method you can get the parameter value by using the data parameter, like
long primeNumberLoopToFind = (long)data
The worker thread raises the ReportWorkDone event which is used by the UI, but when the UI attempts to use this ReportWorkDone EventArg object properties to add items to the UI owned ListBox control, you will get a cross thread violation, unless you do something to marshal the thread to the UI thread. This is know as Thread affinity, the thread that creates the UI controls owns the contols, so any calls to the UI controls must go through the UI thread.
There are several ways of doing this, I am using the .NET 2.0 version of this which makes use of a class called
SynchronizationContext whicn I obtain with the Forms constructor. Then I am free to marshall the
worker threads results to the UI thread so that that may be added to the UIs controls. This is done as follows
context.Post(new SendOrPostCallback(delegate(object state) { this.lstItems.Items.Add(e.PrimeFound.ToString()); }), null);
To pause the worker threac I make use of a Threading object called a
ManualResetEvent which may be used to cause a thread to both wait and resume its operation, depending on the signal state
of the
ManualResetEvent. Basically in a signalled state, the thread that is waiting on the
ManualResetEvent will be allowed to continue, and in a non signalled state
the thread that is waiting on the
ManualResetEvent will be forced to wait. If we examine the relavent parts of the
WorkerThread clas
We declare a new
ManualResetEvent which starts in signalled state
private ManualResetEvent trigger = new ManualResetEvent(true);
We then attempt to wait for the signalled state in the
workerThread DoWork method. As the
ManualResetEvent started out in the signalled state
the thread proceeds to run
for (int i = 0; i< primeNumberLoopToFind; i++) { //wait for trigger trigger.WaitOne(); .... ....
So for the pause all we need to do, is put the
ManualResetEvent in the non signalled state (using the
Reset method) which causes
the worker to wait for the
ManualResetEvent to be put into a signalled state again
trigger.Reset();
The resume is easy, all we need to do, is put the
ManualResetEvent in the signalled state (using the
Set method) which causes
the worker to longer wait for the
ManualResetEvent, as it is in a signalled state again
trigger.Set();
If you read Ian Griffiths article that I quoted above, you'll know that he simply suggests keep things as simple as possible, bu the use of a boolean
flag that is visible to both the UI and the worker thread. I have also done this but I use a
CancelEventArgs. Which allows the user to a cancel state for the worker thread directly into the
CancelEventArgs, such that the worker thread can use this to see if it should be cancelled. Its works like this
CancelEventArgs
CancelEventArgscancel is set
CancelEventArgscancel is set, so breaks out of its work
I just feel this is a little safer than using the
Abort() method
There are some very obvious threading opportunities, which are as follows:
If a task can successfully be run in the background, then it is a candidate for threading. For example think of a search that needs to search 1000nds of items for matching items, this would be an excellent choice for a background thread to do.
Another example may be when you are using an external resource such as a database/web service/ remote file system, where there may be a performance penalty to pay for accessing these resources. By threading access to these sorts of things, you are alleviating some of the overhead incurred by accessing these resources within a single thread.
We can imagine that we have a User Interface (UI) that allows the user to do various tasks. Some of these tasks may taks quite a long time to complete. To put it in a real world context, let us say that the app is a email client application that allows users to create / fetch emails. Fetching emails may take a while to complete, as the fetching of emails must interact with a mail server to obtain the current users emails. Threading the fetch emails code would help to keep the UI resposive to further user interactions. If we dont thread tasks that take a long time in UIs and simply rely on the main thread, we could easily end up in a situation where the UI is fairly unresponsive. So this is a prime candidate for threading. As will see in a subsequent article, there is the issue of Thread Affinity that needs to be considered when dealing with UIs, but I'll save that discussion for the subsequent article.
If you have ever done any Socket programming you may have had to create a Server that was able to accept Clients. A typical arrangement of this may be a chat application where the Server is able to accept n-many clients and is able to read from Clients and write to Clients. This is largely achieved by Threads. Though I am aware that there is an asycnronous socket API available within .NET, so you may choose to use that instead of manually created threads. Sockets are still a valid threading example.
The best example of this that I have seen is located here at this link. The basic idea when working with sockets is that you have a Server and n-many Clients. The server is run (main thread is active) and then for each client connection request that is made, a new thread is created to deal with the Client. At the Client end it is typical that a Client should be able to receive messages from another Client (via the server) and the Client should also allow the Client user to type messages.
Let us just think about the Client for a minute, the Client is able to send messages to other Clients (via the Server), so that implies that there is a thread that needs to be able to respond to data that the user enters. The Client should also be able to show messages from other Clients (via the Server), so this also implies that this also needs to be on a Thread. If we use the same Thread to listen to incoming messages from other Clients, we would block the ability to type new data to send to other Clients.
I don't won't to labour on this example as it's not the main drive of this article, but I thought it may me worth talking about, just so you can see what sort of things you are up against when you start to use Threads, and how they can actually be helpful
In this section I will discuss some common traps, when working with Threads. This is by no means all the traps, rather some of the most common errors.
If we consider the following code example (attached demo ThreadTrap1 project)
using System; using System.Threading; namespace ThreadTrap1 { /// <summary> /// This example shows a threading Trap, you simply can't /// rely on threads executing in the order in which they /// are started. /// </summary> class Program {}", Thread.CurrentThread.Name); WriteDone(Thread.CurrentThread.Name); } private static void WriteDone(string threadName) { switch (threadName) { case "T1" : Console.WriteLine("T1 Finished"); break; case "T2": Console.WriteLine("T2 Finished"); break; } } } }
From looking at this code, one would assume that the Thread named T1 would always finish 1st, as it is the one that is started 1st. However this is not the case, it may finish 1st sometimes, and other times it may not. See the 2 screen shots below that were taken from 2 different runs of this same code
In this screen shot T1 did finish 1st
In this screen shot T2 finished 1st
So this is a trap, never assume the threads run in the order you start them in
If we consider the following code example (attached demo ThreadTrap2 project)
using System; using System.Threading; namespace ThreadTrap2 { /// <summary> /// This example shows a threading Trap, you simply can't /// rely on threads executing in the order in which they /// are started. And also what happens when access to a /// shared field in not synchronized /// </summary> class Program { protected static long sharedField = 0;}, Shared value ={1}", Thread.CurrentThread.Name, sharedField.ToString()); sharedField++; WriteDone(Thread.CurrentThread.Name); } private static void WriteDone(string threadName) { switch (threadName) { case "T1": Console.WriteLine("T1 Finished, Shared value ={0}", sharedField.ToString()); break; case "T2": Console.WriteLine("T2 Finished, Shared value ={0}", sharedField.ToString()); break; } } } }
This code is simliar to the previous example, we still can't rely on the execution order of the threads. Things are also a little worse this time as I introduced a shared field that the 2 threads have access to. It can be seen in the screen shots below that we get different values on different runs of the code. This is failr bad news, imagine this was your bank account. We can solve these issues using "Synchronization" as we will see in a future article in this series.
This screen shot shows the result of 1 run, and we get these end results
This screen shot shows the result of another run, and we get different end results. Oh o, bad news
So this is a trap, never assume threads and shared data play well together, because they don't
Consider the following problem. "The system must send an invioce to each user who has placed an order. This process should run in the background and should not have any adverse affect on the user interface".
If we consider the following code example (attached demo ThreadTrap3 project.)
DONT RUN THIS, ITS JUST TO SHOW A BAD EXAMPLE
using System; using System.Collections.Generic; using System.Threading; namespace ThreadTrap3 { /// <summary> /// This code is bad as it starts a new thread for each invoice that it /// has to send to a Customer. This could be 1000nds of threads, that will /// all incur some overhead when the CPU has to context switch between the /// threads.For this example it probably will not occur as the threads work is /// so small, but for longer running operations there could be issues. /// </summary> class Program { static void Main(string[] args) { List<Customer> custs = new List<Customer>(); custs.Add(new Customer { CustomerEmail = "fred@gmail.com", InvoiceNo = 1, Name = "fred" }); custs.Add(new Customer { CustomerEmail = "same@gmail.com", InvoiceNo = 2, Name = "sam" }); custs.Add(new Customer { CustomerEmail = "john@gmail.com", InvoiceNo = 3, Name = "john" }); custs.Add(new Customer { CustomerEmail = "ted@gmail.com", InvoiceNo = 4, Name = "ted" }); InvoiceThread.CreateAllInvoices(custs); Console.ReadLine(); } } public class InvoiceThread { private static Customer currentCustomer; public static void CreateAllInvoices(List<Customer> customers) { //Create a new thread for every Invoice we need to send. Bad news foreach (Customer cust in customers) { currentCustomer=cust; Thread thread = new Thread(new ThreadStart(SendCustomerInvoice)); thread.Start(); } } private static void SendCustomerInvoice() { //Simulate sending an invoice Console.WriteLine("Send invoice {0}, to Customer {1}", currentCustomer.InvoiceNo.ToString(), currentCustomer.Name); } } /// <summary> /// Simple data class /// </summary> public class Customer { public string Name { get; set; } public string CustomerEmail { get; set; } public int InvoiceNo { get; set; } } }
This example is bad as it creates a new thread for every customer that it needs to send an invoice to
foreach (Customer cust in customers) { currentCustomer=cust; Thread thread = new Thread(new ThreadStart(SendCustomerInvoice)); thread.Start(); }
But just why is this so bad? It seems to make some sort of sense, after all it could take quite a while to send a invoice off using email. So why not thread it? When we create a new thread within a loop as I have done here, each thread needs to be allocated some CPU time, and as such teh CPU will spend so much time context switching (A context switch consists of storing context information from the CPU (registers) to the current thread's kernel stack, and loading the context information to the CPU from the kernel stack of the thread selected for execution) to allow each thread some CPU time that very little of the actual thread instructions will be performed, the system may even lock up.
Thats one thing, there is also quite a lot of overhead with creating a thread to begin with. This is why a ThreadPool class exists. We will be seeing that in a later article.
What would make more sense is to have a single background thread and use that to send out ALL the invoices, or use a thread pool, where once a thread it finished it can go back into a shared pool. We will be looking at thread pools in a subsequent article in this series
We have not covered locks yet (part3 will talk about these) so I don't want to spend too much time on this one, but I will just briefly mention them
We can imagine 2 or more threads sharing some common data, which we need to ensure is kept safe, now in .NET there are various ways of doing this, one of which is by using the "lock" keyword (we will cover this in part3) which ensures mutually exclusive access to the code within the "lock" section. One possibly problem may be that a programmer locks an entire method to try and ensure the shared data is kept safe, but really they only needed to lock a couple of lines of code that dealt with the shared data. I think a good decsription I once heard for this called it "Lock Granularity" which I think sums it up quite well. Basically only lock what you really need to lock.
Well thats all I wanted to say this time. Threading is a complex subject, and as such this series will be quite hard, but I think worth a read.
Next time we will be looking at Synchronization.
Could I just ask, if you liked this article could you please vote for it, as that will tell me whether this Threading crusade that I am about to embark on will be worth creating articles for.
I thank you very much
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from
Richard Alex Durante
Plus
This is the unofficial video for Myke Flow's "Feel My Vision". The original version can be found here: youtube.com/watch?v=cBm5ubQb3P8
mykeflow.com
My thanks to the director, Nic Domaguing of London Productions, for allowing me to shoot and make my own personal edit of the video, and giving me the opportunity to DP. Also a big thanks to Marshall Moses of Big & Slim Productions for helping with the grip and camera assistance. And lastly, a thanks to Myke Flow for allowing us to shoot this video. No thanks given to that family who stood in our shot, oblivious to their surroundings and clueless of the music video we were so obviously shooting. I hope they enjoyed San Francisco, and I hope they never return (because they enjoyed it so much and they don't want to spoil "the magic"). | https://vimeo.com/groups/fs100/videos/53488378 | CC-MAIN-2017-09 | refinedweb | 159 | 69.11 |
Chapter 12In this chapter:
SOAP
Starting Out
Setting Up
Getting Dirty
Going Further
What's Next?
SOAP is the Simple Object Access Protocol. If you haven't heard of it by now, you've probably been living under a rock somewhere. It's become the newest craze in web programming, and is integral to the web services fanaticism that has taken hold of the latest generation of web development. If you've heard of .NET from Microsoft or the peer-to-peer "revolution," then you've heard about technologies that rely on SOAP (even if you don't know it). There's not one but two SOAP implementations going on over at Apache, and Microsoft has hundreds of pages on their MSDN web site devoted to it ().
In this chapter, I explain what SOAP is, and why it is such an important part of where the web development paradigm is moving. That will help you get the fundamentals down, and prepare you for actually working with a SOAP toolkit. From there, I briefly run over the SOAP projects currently available, and then delve into the Apache implementation. This chapter is not meant to be the complete picture on SOAP; the next chapter fills in lots of gaps. Take this as the first part of a miniseries; many of your questions at the end of this chapter will be answered in the next.
Starting Out make it more attractive in many cases than the other choices for a distributed protocol.[1] Additionally, SOAP provides a high degree of interoperability with other applications, which I delve into more completely in the next chapter. For now, I want to focus on the basic pieces of SOAP.
The Envelopeattribute) whether it can read the incoming message situated within the
Bodyelement. Be sure to get the SOAP envelope namespace correct, or SOAP servers that receive your message will trigger version mismatch errors, and you won't be able to interoperate with them.
Encoding
The second major element that SOAP brings to the table is a simple means of encoding user-defined datatypes.ypestructure discussed way back in Chapter 2), and those new types can be easily represented in XML as part of a SOAP payload. Because of this integration with XML Schema, you can encode any datatype in a SOAP message that you can logically describe in an XML schema.
Invocationobject,.
With that brief introduction, you probably know enough to want to get on with the fun stuff. Let me show you the SOAP implementation I'm going to use, explain why I made that choice, and get to some code.
Setting Up Version 2.2 release, you can download it from the Apache web site. That's the version and project I use for the examples throughout this chapter.
Other Options.
What about IBM SOAP4J?.
Isn't Microsoft a player?
Yes. Without a doubt, Microsoft and its it off, at least in this particular regard. If you need to communicate with COM or Visual Basic components, I highly recommend checking out the Microsoft SOAP toolkit, found online at along with a lot of other SOAP resources.
What's Axis?.
Installation.
The client.
NOTE: Ensure your XML parser is JAXP-compatible and namespace-aware. Your parser, unless it's a very special case, probably meets both of these requirements. If you have problems, go back to using Xerces.
NOTE: Use a recent version of Xerces; Version 1.4 or greater should suffice. There are a number of issues with SOAP and Xerces 1.3(.1), so I'd avoid that combination like the plague.
Expand both the JavaMail and JAF packages, and then add the included jar files to your classpath, as well as the soap.jar library. Each of these jar files is either in the root directory or in the lib/ directory of the relevant installation. At the end, your classpath should look something like this:
$ examples. I cover setup for specific examples in this chapter as I get to them.
The server
To build a SOAP-capable set of server components, you first need a servlet engine. As in earlier chapters, I'll use Apache Tomcat (available from) throughout this chapter for examples. examples), you'll need to put bsf.jar (available online at) and js.jar (available from) in the same directory. are loaded prior to any other parser or JAXP implementation.
Now restart your servlet engine, and you're ready to write SOAP server components.
The router servlet and admin client simple; just take the soap.war file in the soap-2_2/webapps directory, and drop it in your $TOMCAT_HOME/webapps directory. That's it! To test the installation, point your web browser to. You should get a response like that shown in Figure 12-2..
Getting Dirty
There need to write the client for this service, and watch things take off.
RPC or Messaging?.
Like most design issues, the actual process of making this decision is left up to you. Look at your application and determine exactly what you want SOAP to do for you. If you have a server and a set of clients that just need to perform tasks remotely, then RPC is probably well suited for your needs. However, in larger systems that are exchanging data rather than performing specific business functions on request, SOAP's messaging capabilities may be a better match.
An RPC Service
With the formalities out of the way, it's time to get going, fast and furious. As you'll recall from the last chapter, in RPC you need a class that is going to have its methods invoked remotely.
Code artifacts
I'll start by showing you some code artifacts to have available on the server. These artifacts are classes with methods that are exposed to RPC clients.[2] Rather than use the simple class from last chapter, I offer a slightly more complex example to show you what SOAP can do. In that vein, Example 12-4 is a class that stores a CD inventory, such as an application for an online music store might use. I'm introducing a basic version here, and will add to it later in the chapter. forJava type, much as XML-RPC did.
Compile this class, and make sure you've got everything typed in (or downloaded, if you choose) correctly. Notice that the
CDCatalogclass has no knowledge about SOAP. This means you can take your existing Java classes and expose them through SOAP-RPC, which reduces the work required on your end to move to a SOAP-based architecture if needed.
Deployment descriptors
With the Java coding done, you now need to define a deployment descriptor. This specifies several key things to a SOAP server:
- The URN of the SOAP service for clients to access
- The method or methods available to clients
- The serialization and deserialization handlers for any custom classes. The third is a means of telling the SOAP serverserviceattribute. This should be something unique across services, and descriptive of the service. I showed about as much originality in naming the service as Dave Matthews did with his band, but it gets the job done. Then, I specified through the
javaelement the class to expose, including its package name (through the
classattribute), and indicated that the methods being exposed were not static ones (through the
staticattribute).
Next, I specified a fault listener implementation to use. Apache's SOAP implementation provides two; Iin most cases.
Deploying the service.
With your service class (or classes) accessible by your SOAP server, you can now deploy the service, using Apache SOAP's
org.apache.soap.server.ServiceManagerutility class:.
An RPC Client:
- Create the SOAP-RPC call
- Set up any type mappings for custom parameters
- Set the URI of the SOAP service to use
- Specify the method to invoke
- Specify the encoding to use
- Add any parameters to the call
- Connect to the SOAP service
- Receive and interpret a response
That may seem like a lot, but most of the operations are one- or two-line method invocations. In other words, talking to a SOAP service is generally a piece of cake. Example 12-6 shows the code for the
CDAdderclass, which allows you to add a new CD to the catalog. Take a look at the code, and then I'll walk you through the juicy bits.object, on which all the interesting interaction occurs. The target URI of the SOAP service and the method to invoke are set on the call, and both match up to values from the service's deployment descriptor from Example 12-5. Next, the encoding is set, which should always be the constant
Constants.NS_URI_SOAP_ENCunless you have very unique encoding needs.
The program creates a new
Vectorpopulated with SOAP
Parameterobjects. Each of these represents a parameter to the specified method, and since the
addCD( )method takes two
Stringvalues, this is pretty simple. Supply the name of the parameter (for use in the XML and debugging), the class for the parameter, and the value. The fourth argument is an optional encoding, if a single parameter needs a special encoding. For no special treatment, the value
nullsuffices. The resulting
Vectoris then added to the
Callobject.
Once your call is set up, use the
invoke( )method on that object. The return value from this method is an
org.apache.soap.Responseinstance, which is queried for any problems that resulted. This is fairly self-explanatory, so I'll leave it to you to walk through the code. Once you've compiled your client and followed the instructions earlier in this chapter for setting up your classpath, run the example as follows: a reinforcement of what I've already talked about.class is that the
Responseobject has a return value (the
Hashtablefrom the
list( )method). This is returned as a
Parameterobject,.
Going Further.
Custom Parameter Types
The most limiting thing with the CD catalog, at least at this point, is that it stores only the title and artist for a given CD. It is much more realistic to have an object (or set of objects) that represents a CD with the title, artist, label, track listings, perhaps a genre, and all sorts of other information. I'm not going to build this entire structure, but will move from a title and artist to a
CDobject with a title, artist, and label. This object needs to be passed from the client to the server and back, and demonstrates how SOAP can handle these custom types. Example 12-8 shows this new class.class as well. Example 12-9 shows a modified version of this class with the changes that use the new
CDsupport class highlighted.;
}
}
In addition to the obvious changes, I've also updated the old
getArtist(String
title)method to
getCD(String title), and made the return value a
CDobject. This means the SOAP server will need to serialize and deserialize this new class, and the client will be updated. First, I look at an updated deployment descriptor that details the serialization issues related to this custom type. Add the following lines to the deployment descriptor for the CD catalog, as well as changing the available method names to match the updated
CDCatalogclass:
class. First, define a
mapelement for each custom parameter type. For the
encodingStyleattribute,attribute, supply the actual Java class name:
javaxml2.CDin this case. Finally, the magic occurs in the
java2XMLClassNameand
xml2JavaClassNameattributes. These specify a class to convert from Java to XML and from XML to Java, respectively. I've used the incredibly handy
BeanSerializerclass,class), and expose all the data in that class through
setXXXand
getXXXstyle methods. Since the
CDclass fits the bill here, the
BeanSerializerworks perfectly.
NOTE: It's no accident that the
CDclass follows the JavaBean conventions. Most data classes fit easily into this format, and I knew I wanted to avoid writing my own custom serializer and deserializer. These are a pain to write (not overly difficult, but easy to mess up), and I recommend you go to great lengths to try and use the Bean conventions in your own custom parameters. In many cases, the Bean conventions only require that a default constructor (with no arguments) is present in your class.
Now recreate your service jar file. Then, redeploy your service:
activate the new classes for the SOAP service, and redeploy the service.
At this point, all that's left is modifying the client to use the new class and methods. Example 12-10 is an updated version of the client class
CDAdder. The changes from the previous version of the class are highlighted.class:
//class could be used to handle parameters in the JavaBean format, such as the
CDclass. To specify that to the server, I used the deployment descriptor; however, now I need to let the client know to use this serializer and deserializer. This is what the
SOAPMappingRegistryclass allows. The
mapTypes( )method takes in an encoding string (again, using the constant
NS_URI_SOAP_ENCis the best idea here), and information about the parameter type a special serialization should be used for. First, a
QNameis supplied. This is why the odd namespacing was used back in the deployment descriptor; you need to specify the same URN here, as well as the local name of the element (in this case "CD"), then the Java
Classobject of the class to be serialized (
CD.class), and finally the class instance for serialization and deserialization. In the case of the
BeanSerializer, the same instance works for both. Once all this is set up in the registry, let the
Callobject know about it through the
setSOAPMapping-Registry( )method.class in the same fashion, and the downloadable samples have this updated class as well.
NOTE: work.
Better Error Handling, and a whole lot of other problems can arise. Until now, I just used the
fault.getString( )method to report errors. But this method isn't always very helpful. To see it in action, comment out the following line in the
CDCatalogconstructor:occurs when the class constructor tries to add a CD to an uninitialized
Hashtable. Running the client will let you know an error has occurred, but not in a very meaningful way:
you specified as the value of the
faultListenerelement? This is where it comes into play. The returned
Faultobject in the case of a problem (as in this one) contains a DOM
org.w3c.dom.Elementwith detailed error information. First, add an import statement for
java.util.Iteratorto your client source code:contained within each entry. Essentially, here's the XML you are working through:
<SOAP-ENV:Fault>
<faultcode>SOAP-ENV:Server.BadTargetObjectURI</faultcode>
<faultstring>Unable to resolve target object: null</faultstring>
<stacktrace>Here's what we want!</stackTrace>
</SOAP-ENV:Fault>
In other words, the
Faultobject gives you access to the portion of the SOAP envelope that deals with errors. Additionally, Apache SOAP provides a Java stack trace if errors occur, and that provides the detailed information needed to troubleshoot problems. By grabbing the
stackTraceelement and printing the
Textnode's value from that
Element, your client will now print out the stack trace from the server. Compile these changes and rerun the client. You should get the following output:occurred,class back to a version that won't cause these errors before moving on!
What's Next?.
1. There's a lot of talk about running SOAP over other protocols, like SMTP (or even Jabber). This isn't part of the SOAP standard, but it may be added in the future. Don't be surprised if you see it discussed.
2. You can use scripts through the Bean Scripting Framework, but for the sake of space I won't cover that here. Check out the upcoming O'Reilly SOAP book, as well as the online documentation at, for more details on script support in SOAP.
Back to: Java & XML, 2nd Edition
© 2001, O'Reilly & Associates, Inc.
webmaster@oreilly.com | http://oreilly.com/catalog/javaxml2/chapter/ch12.html | crawl-002 | refinedweb | 2,651 | 63.9 |
CMDSH(3) OpenBSD Programmer's Manual RCMDSH(3)
NAME
rcmdsh - return a stream to a remote command without superuser
SYNOPSIS
#include <unistd.h>
int
rcmdsh(char **ahost, int inport, const char *locuser,
const char *remuser, const char *cmd, char *rshprog);
DESCRIPTION
The rcmdsh() function is used by normal users to execute a command on a
remote machine using an authentication scheme based on reserved port num-
bers using rshd(8) or the value of rshprog (if non-null).
The rcmdsh() function looks up the host *ahost using gethostbyname(3),
returning -1 if the host does not exist. Otherwise *ahost is set to the
standard name of the host and a connection is established to a server re-
siding.
DIAGNOSTICS
The rcmdsh() function returns a valid socket descriptor on success. It
returns -1 on error and prints a diagnostic message on the standard er-
ror.
SEE ALSO
rsh(1), socketpair(2), rcmd(3), rshd(8)
BUGS
If rsh(1) gets an error a file descriptor is still returned instead of
-1.
HISTORY
The rcmdsh() function first appeared in OpenBSD 2.0.
OpenBSD 2.6 September 1, 1996 1 | http://www.rocketaware.com/man/man3/rcmdsh.3.htm | CC-MAIN-2015-11 | refinedweb | 187 | 52.09 |
Qt Quick 2 Scatter Example
Using Scatter3D in a QML application.
The Qt Quick 2 scatter example shows how to make a simple scatter graph visualization using Scatter3D and Qt Quick 2.
For instructions about how to interact with the graph, see this page.
For instructions how to create a new Qt Quick 2 application of your own, see Qt Creator help.
Running the Example
To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.
Application Basics
Before diving into the QML code, let's take a look at the application
main.cpp.
This application implements a 'Quit' button in the UI, so we want to connect the QQmlEngine::quit() signal to our application's QWindow::close() slot:
QObject::connect(viewer.engine(), &QQmlEngine::quit, &viewer, &QWindow::close);
To make deployment little simpler, we gather all of the application's
.qml files to a resource file (
qmlscatter.qrc):
<RCC> <qresource prefix="/"> <file>qml/qmlscatter/Data.qml</file> <file>qml/qmlscatter/main.qml</file> </qresource> </RCC>
This also requires us to set the
main.qml to be read from the resource (
qrc:):
Lastly, we want the application to run in a maximized window:
viewer.showMaximized();
Setting up the Graph
First we'll import all the QML modules we need:
import QtQuick import QtQuick.Layouts import QtQuick.Controls import QtDataVisualization 1.2 import "."
The last
import just imports all the qml files in the same directory as our
main.qml, because that's where
Data.qml is.
Then we create our main
Item and call it
mainView:
Then we'll add another
Item inside the main
Item, and call it
dataView. This will be the item to hold the Scatter3D graph. We'll anchor it to the parent bottom:
Next we're ready to add the Scatter3D graph itself. We'll add it inside the
dataView and name it
scatterGraph. Let's make it fill the
dataView:
Now the graph is ready for use, but has no data. It also has the default axes and visual properties.
Let's modify some visual properties first by adding the following inside
scatterGraph:
theme: themeIsabelle shadowQuality: AbstractGraph3D.ShadowQualitySoftLow
We added a customized theme and changed the shadow quality. We're happy with the other visual properties, so we won't change them.
The custom theme is based on a predefined theme, but we change the font in it:
Theme3D { id: themeIsabelle type: Theme3D.ThemeIsabelle font.family: "Lucida Handwriting" font.pointSize: 40 }
Then it's time to start feeding the graph some data.
Adding Data to the Graph
Let's create a
Data item inside the
mainView and name it
seriesData:
Data { id: seriesData }
The
seriesData item contains the data models for all three series we use in this example.
This is the component that holds our data in
Data.qml. It has an
Item as the main component.
In the main component we'll add the data itself in a
ListModel and name it
dataModel:
ListModel { id: dataModel ListElement{ xPos: -10.0; yPos: 5.0; zPos: -5.0 } ...
We'll add two more of these for the other two series, and name them
dataModelTwo and
dataModelThree.
Then we need to expose the data models to be usable from
main.qml. We do this by defining them as aliases in the main data component:
property alias model: dataModel property alias modelTwo: dataModelTwo property alias modelThree: dataModelThree
Now we can use the data from
Data.qml with
scatterGraph in
main.qml. First we'll add a Scatter3DSeries and call it
scatterSeries:
Scatter3DSeries { id: scatterSeries
Then we'll set up selection label format for the series:
itemLabelFormat: "Series 1: X:@xLabel Y:@yLabel Z:@zLabel"
And finally the data for series one in a ItemModelScatterDataProxy. We set the data itself as
itemModel for the proxy:
ItemModelScatterDataProxy { itemModel: seriesData.model xPosRole: "xPos" yPosRole: "yPos" zPosRole: "zPos" }
We'll add the other two series in the same way, but modify some series-specific details a bit:
Scatter3DSeries { id: scatterSeriesTwo itemLabelFormat: "Series 2: X:@xLabel Y:@yLabel Z:@zLabel" itemSize: 0.1 mesh: Abstract3DSeries.MeshCube ...
Then we'll modify the properties of the default axes in
scatterGraph a bit:
axisX.segmentCount: 3 axisX.subSegmentCount: 2 axisX.labelFormat: "%.2f" axisZ.segmentCount: 2 axisZ.subSegmentCount: 2 axisZ.labelFormat: "%.2f" axisY.segmentCount: 2 axisY.subSegmentCount: 2 axisY.labelFormat: "%.2f"
After that we'll just add a few buttons to the
mainView to control the graph. We'll only show one as an example:
Button { id: shadowToggle Layout.fillHeight: true Layout.fillWidth: true text: scatterGraph.shadowsSupported ? "Hide Shadows" : "Shadows not supported" enabled: scatterGraph.shadowsSupported onClicked: { if (scatterGraph.shadowQuality === AbstractGraph3D.ShadowQualityNone) { scatterGraph.shadowQuality = AbstractGraph3D.ShadowQualitySoftLow; text = "Hide Shadows"; } else { scatterGraph.shadowQuality = AbstractGraph3D.ShadowQualityNone; text = "Show Shadows"; } } }
Then we'll modify
dataView to make room for the buttons at the top:
Item { id: dataView anchors.bottom: parent.bottom width: parent.width height: parent.height - buttonLayout.height ...
And we're done!
Example Contents. | https://doc-snapshots.qt.io/qt6-6.1/qtdatavisualization-qmlscatter-example.html | CC-MAIN-2021-39 | refinedweb | 830 | 51.04 |
I just started getting this message as I was creating custom fields in TFS 2013...
I changed a custom field name from enhancementpriority to enhancement priority and it said that I can not save it, but it allowed me to save and now I keep getting this error
Warning 2 Cannot find a schema that defines target namespace '', schema validation skipped. C:\Users\snassiri\Desktop\Feature_test5.wit.diagram 2 2 Miscellaneous Files
how can I get rid of it?
Hi,
The TFS forums can be found over here:
Good luck.
Don't retire TechNet! -
(Don't give up yet - 13,085+ strong and growing) | https://social.microsoft.com/Forums/en-US/f671f618-ff01-408d-bbdd-3a6133437f87/cannot-find-a-schema-that-defines-target-namespace?forum=whatforum | CC-MAIN-2018-17 | refinedweb | 104 | 63.9 |
Hide Forgot
Description of problem:
getpwnam does not return good value on 64-bit RHEL6.1 when built with -m32.
Version-Release number of selected component (if applicable):
both 6.0 and 6.1 have this issue. The issue does not exist for earlier RHEL4/5.
How reproducible:
always.
Steps to Reproduce:
1. source code (save it as testget.cpp)
#include <sys/types.h>
#include <pwd.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
main()
{
char *lgn;
struct passwd *pw;
if ((lgn = getlogin()) == NULL || (pw = getpwnam("cluster")) == NULL) {
fprintf(stderr, "Get of user information failed.\n"); exit(1);
}
printf("\nThe user name is: %s\n", pw->pw_name);
printf("The user id is: %u\n", pw->pw_uid);
printf("The group id is: %u\n", pw->pw_gid);
printf("The initial directory is: %s\n", pw->pw_dir);
printf("The initial user program is: %s\n", pw->pw_shell);
}
2. do `g++ -m32 testget.cpp -o testget32` on a RHEL6.x/x64 machine
3. run testget32
Actual results:
[root@beethoven ~]# ~petr/tcpp/testget32
Get of user information failed.
Expected results:
[root@beethoven ~]# ~petr/tcpp/testget64
The user name is: cluster
The user id is: 8579
The group id is: 10
The initial directory is: /User/cluster
The initial user program is: /bin/bash
Additional info:
Removing -m32 (building 64-bit native app), the problem is gone..
Then can this be addressed in 6.2 release?
Make sure you have all configured NSS modules installed.
Hi, Andreas,
How do you check my NSS modules? `rpm -qa`? Let me know.
From commandline:
[root@gershwin ~]# getent passwd allen
allen:*:1004:301:Allen Zhao:/User/allen:/bin/bash
Our box is integrated with a Windows server with LDAP/Kerberos5. Above shows the LDAP user info is ok. Of course, the getent must be 64-bit here. `kinit` also works ok. So I do not see a NSS issue here.
If this is indeed NSS module installation issue, well, the only thing I know is that we selected workstation during installation, nothing was disabled. I know this probably does not answer your question, but it is just a background info.
Also, if it is indeed NSS modules, when the same code compiled in 64-bit mode works, but compiled in 32-bit mode (-m32) simply fail?
See /etc/nsswitch.conf.
we used sss:
related entries in /etc/nsswitch.conf
passwd: files sss
shadow: files sss
group: files sss
the /etc/sssd/sssd.conf entries:
services = nss, pam
domains = default
[domain/default]
id_provider = ldap
ldap_uri = ldap://xxxx.gtisoft.com,ldap://yyyy.gtisoft.com
ldap_search_base = dc=gtisoft,dc=com
ldap_default_bind_dn = cn=ldapadmin,cn=Users,dc=gtisoft,dc=com
ldap_default_authtok_type = password
ldap_default_authtok = whatever
auth_provider = krb5
chpass_provider = krb5
krb5_kpasswd = xxxx.gtisoft.com,yyyy.gtisoft.com
krb5_server = xxxx.gtisoft.com,yyyy.gtisoft.com
krb5_realm = GTISOFT.COM
krb5_kdcip = xxxx.gtisoft.com,yyyy.gtisoft.com
cache_credentials = True
ldap_user_object_class = person
ldap_user_uid_number = uidNumber
ldap_user_gid_number = gidNumber
ldap_user_principal = userPrincipalName
ldap_user_home_directory = unixHomeDirectory
ldap_user_name = sAMAccountName
ldap_group_object_class = group
ldap_group_name = sAMAccountName
ldap_group_gid_number = gidNumber
ldap_force_upper_case_realm = True
ldap_id_use_start_tls = False
ldap_tls_cacertdir = /etc/openldap/cacerts
As I just asked in previous reply, if commandline `getent passwd allen` works fine, what else could be missing? We have no user login issue, it is only when we compile the code snip with '-m32', things fall apart.
Can you reproduce the issue in your system? (with -m32 compiler option).
Make sure /lib/libnss_sss.so.* is installed.
I do not see /lib/libnss_sss.so.* at all.
All I have (as part of the default system installation):
[root@gershwin ~]# ls -al /lib/libnss_
libnss_compat-2.12.so libnss_files-2.12.so libnss_nis-2.12.so
libnss_compat.so.2 libnss_files.so.2 libnss_nisplus-2.12.so
libnss_dns-2.12.so libnss_hesiod-2.12.so libnss_nisplus.so.2
libnss_dns.so.2 libnss_hesiod.so.2 libnss_nis.so.2
which rpm has this file? I have checked that RHEL6.0 and RHEL6.1 installation both have 32-bit libnss_sss.so.* missing. On the other hand, the /lib64/libnss_sss.so.2 does exist.
So, this is a system installation issue?
I just checked my RHEL6.1 DVD, sssd-client-1.5.1-34.el6.i686.rpm is there. But the dependency on 32-bit PAM subsystem is a lot of work.
[root@gershwin Packages]# rpm -i sssd-client-1.5.1-34.el6.i686.rpm
warning: sssd-client-1.5.1-34.el6.i686.rpm: Header V3 RSA/SHA256 Signature, key ID fd431d51: NOKEY
error: Failed dependencies:
libpam.so.0 is needed by sssd-client-1.5.1-34.el6.i686
libpam.so.0(LIBPAM_1.0) is needed by sssd-client-1.5.1-34.el6.i686
libpam.so.0(LIBPAM_EXTENSION_1.0) is needed by sssd-client-1.5.1-34.el6.i686
libpam.so.0(LIBPAM_MODUTIL_1.0) is needed by sssd-client-1.5.1-34.el6.i686
[root@gershwin Packages]# rpm -i pam-1.1.1-8.el6.i686.rpm
warning: pam-1.1.1-8.el6.i686.rpm: Header V3 RSA/SHA256 Signature, key ID fd431d51: NOKEY
error: Failed dependencies:
libaudit.so.1 is needed by pam-1.1.1-8.el6.i686
libcrack.so.2 is needed by pam-1.1.1-8.el6.i686
libdb-4.7.so is needed by pam-1.1.1-8.el6.i686
libselinux.so.1 is needed by pam-1.1.1-8.el6.i686
Is there a reason why RH does not make the 32-bit PAM/SSSD part of the default installation? This is a really bad installation, comparing with the current SLES 11.x installation.
I guess you can close this bug. I do feel that a bug should be logged in the RHEL installer to resolve this. We are shipping some 32-bit daemons to our customers for the foreseeable future. If we have to let customers to go through all these troubles (actually we already have enough trouble with RHEL6.x for removing some crucial 32-bit C++ runtimes), it is very very bad.
yum install sssd-client.i686 | https://bugzilla.redhat.com/show_bug.cgi?id=732805 | CC-MAIN-2019-39 | refinedweb | 988 | 53.88 |
We believe in nothing..
The factory should probably be a standalone class, rather than a subclass of MyClass. Then you can make the factory public and MyClass private, and then you're free to do whatever the heck you want with MyClass (including renaming it or deleting it).
At least as long as it's not binary serializable, anyway.
Good call, Miral.
This all fits in to the more general statement of "future proofing is hard". :-)
Hooah! The world is sane after all.
Thanks man. Great post.
---
I have to write too much code for my code to be future proof so therefore I write non future proof code because I have the foresight to see the future for this code?!?
Or alternatively, you gamble on the odds of needing future proof code.
Why can't we have a language where we can write simple code that is future proof?
Then we don't need to have these daft arguments about "good" code design / rules.
I think its worth remembering these aren't good design principles, these things are "hacks" around language difficulties. Don't get me wrong, It's not that these ideas are without merit, they certainly help you work within the bounds of C#, but its worth keeping it in mind that they are simply hacks and the "rules/guidance" would disappear if the language allowed you to express what you wanted.
"Constructors lock you in to a type. If you really want binary compatibility, you should stop providing ctors, and start providing factory methods:"
public class MyClass
{
MyClass() { }
public static MyClass New() { return new MyClass(); }
}
You don't need to do this. Just use Constructor Injection to push in IMyClass instances into the dependent classes, then use an IoC tool if you want to do the mechanical work.
You'll end up with potentially more flexibility without having to go out of your way when you're building classes. | http://blogs.msdn.com/jaybaz_ms/archive/2007/02/08/properties-vs-fields-again.aspx | crawl-002 | refinedweb | 323 | 69.72 |
Feature #9118
In Enumerable#to_a, use size to set array capa when possible
Description
Cross-post from.
Enumerable#to_a works by creating an empty array with small capacity, then populating it and expanding the capacity as it goes. For large enumerables, this causes several resizes, which can hurt performance. When an enumerable exposes a size method, we can guess that the resulting array's size will usually be equal to the enumerable's size. If we're right, we only have to set capacity once, and if we're wrong, we don't lose anything.
The attached file (or linked PR) adjusts enum.c's to_a method to take advantage of the size method when it's there. In my tests this makes Range#to_a about 10% faster, and doesn't have any significant effect on a vanilla enum with no size method. I couldn't find any existing benchmark that this consistently made better or worse.
If you like this idea, this could also be done in other classes with custom to_a, like Hash.
History
#1
Updated by Hans Mackowiak over 1 year ago
enum.size can return Float::Infinity maybe for [1,2,3].cycle.size you need to check that too
#2
Updated by Aaron Weiner over 1 year ago
Ah, right! This seems like an opportunity to improve on existing behavior: right now that just silently hangs forever. Do you think we should warn, then hang, or just raise? I'd lean towards the warn because it's possible size is returning the wrong thing.
#3
Updated by Yusuke Endoh over 1 year ago
I think the proposal will break the compatibility of the following code:
class C
include Enumerable
def size
to_a.size
end
def each
end
end
C.new.size #=> expected: 0, with the proposal: stack level too deep
Examples in the wild:
-
-
-
-
In addition, #each and #size does not necessarily have a common semantics.
In fact, IO#each yields strings in lines, but IO#size returns a count in bytes.
Yusuke Endoh mame@tsg.ne.jp
#4
Updated by Aaron Weiner over 1 year ago
It definitely breaks that usage, but that's bad usage--we're supposed to use Enumerable#count for that, not size.
In cases where size doesn't correctly predict the array, this doesn't really break anything, it just switches out one bad guess at capa for another.
#5
Updated by Hans Mackowiak over 1 year ago
Enumerable#count may not a good idea, better would be Enumerator#size
Also available in: Atom PDF | https://bugs.ruby-lang.org/issues/9118 | CC-MAIN-2015-11 | refinedweb | 426 | 63.49 |
I wrote a shortest path algorithm about a year ago using Python and later on port it into JavaScript, I recently revisit the algorithm and port it into Golang and compare the performance of three versions on two different hardware platforms.
Shortest Path Algorithm with Python and Raspberry Pi
In my previous article that published almost a year ago, I wrote about How to create an interactive transport system map with shortest path algorithm. The algorithm was written in Python, and was fairly optimized based on Python code (or rather I don’t know what I could do to further optimize it). It tooks any where from a few hundred milliseconds to roughly about 2 seconds to calculation the shortest path between two nodes (two subway stations) over about 100 nodes on my MacBook Pro which is a late 2011 model with a 2.4Hz Intel Core i5 CPU.
Python version
def shortest_path(graph, start, end, path=[]): if start not in graph.keys(): return None path = path + [start] if start == end: return path shortest = None for node in graph[start]: if node not in path: new_path = shortest_path(graph, node, end, path) if new_path: if not shortest or len(new_path) < len(shortest): shortest = new_path return shortest
As you probably awared that I run this blog on a Raspberry Pi 3 model B which has an ARMv7-based Brodcom BCM2837 SoC running at 1.2GHz. When I load the very same algorithm to the Raspberry Pi, the algorithm took 8 times longer to calculate the same shortest path than when running on my MacBook Pro. A 2 seconds calculation would became 16 seconds or longer to finish. This is obviously not practical and not a good user experience for a web application.
Porting Shortest Path Algorithm to JavaScript
So I port the algorithm to JavaScript with the assumption that any computer out there, desktop or notebook, or even a mobile phone nowsaday, would be more powerful and therefore faster than a Raspberry Pi.
JavaScript version
function calShortestPath(graph, start, end, path=[]) { if (!graph.hasOwnProperty(start)) { return []; } path = path.concat(start); if (start == end) { return path; } let shortest = []; for (let node of graph[start]) { if (path.indexOf(node) == -1) { let newPath = calShortestPath(graph, node, end, path); if (newPath.length > 0) { if ( shortest.length == 0 | (newPath.length < shortest.length) ) { shortest = newPath; } } } }; return shortest; }
Moving the algorithm from backend (running Python) to frontend (with JavaScript) sort of solved the performance problem, but I have to give up one of the features that was available in the Python web application (not directly related to the algorithm though). When I create the Interfactive map web application, I imagine that you could query the server through a GET request with an API through an endpoint like
/api/v1/?start=ns1/ew24&end=ew2/dt2, and the server will return a shortest path JSON object that consists of a list of stations that formed the short test path between the two stations
ns1/ew24 and
ew2/dt2. The JavaScript solution works well for most of the cases, but the performance varies from user to user, depend on the machine/device he/she is using, for example, if you are using a relative old phone such as iPhone5, the performance is still a little bit too slow for what I consider a good user experience. So I always consider this as a short term solution and want to solve this problem, but I didn’t do anything until recently.
Shortest Path Algorithm with Golang
Unlike Python and JavaScript, that are interpreted high-level programming languages, Golang or Go is a compiled programming language, designed with improving programming productivity (shorter build time) and runtime efficiency in mind. I recently start to tinkering with Golang and decided to revisit the shortest path algorithm with Golang.
Porting the algorithm from Python to Golang is kind of travia and the finished code looks still quite similar to the Python version, except that Golang does not have a build-in function for checking if a slice contains an element, such as Object.prototype.hasOwnProperty() in JavaScript, or accessing the view object of a Python Dictionary. For Golang, I have to create a custom type with a method to do that. The Golang code for the shortest algorithm with the helper method for the custom type is listed here:
Golang version
package main import ( "fmt" ) type Array []string func (arr Array) hasPropertyOf(str string) bool { for _, v := range arr { if str == v { return true } } return false } func ShortestPath(graph map[string][]string, start string, end string, path Array) []string { if _, exist := graph[start]; !exist { return path } path = append(path, start) if start == end { return path } shortest := make([]string, 0) for _, node := range graph[start] { if !path.hasPropertyOf(node) { newPath := ShortestPath(graph, node, end, path) if len(newPath) > 0 { if (len(shortest) == 0 || (len(newPath) < len(shortest))) { shortest = newPath } } } } return shortest }
Performance Comparison
I’m ready to do some performance comparison between Python, JavaScript and Golang. I wrote a simple program for each of the languages to test the time taken for calculating the shortest path. To not dupliate the code that already shown above, The following codes are ignore the function of each shortest path implementation, and only show the codes realted to load the graph data structure, and the code for testing in Python, Nodejs (for JavaScript) and Golang. The complete version of the codes are available at my github repo.
Python test
import json import time def load_graph(file_name): with open(file_name) as f: data = json.load(f) return data stations = load_graph('./data/stations_sg.json') s = time.time() route = shortest_path(stations, "ns1/ew24", "ew2/dt32") elapsed = time.time() - s print(elapsed) print(route)
Nodejs test
var fs = require('fs'); var s = "ns1/ew24"; var e = "ew2/dt32"; var p = []; var graph = JSON.parse(fs.readFileSync('./data/stations_sg.json', 'utf8')); const t = new Date(); var sp = calShortestPath(g, s, e, p); const elapsed = new Date() - t; console.log(elapsed); console.log(sp);
Golang test
package main import ( "fmt" "time" "encoding/json" "io/ioutil" "os" ) func ReadStationsData () map[string][]string { var stations map[string][]string jsonFile, err := os.Open("./data/stations_sg.json") defer jsonFile.Close() if err != nil { fmt.Println(err) } jsonBytes, _ := ioutil.ReadAll(jsonFile) json.Unmarshal([]byte(jsonBytes), &stations) return stations } func main() { graph := ReadStationsData() var s string = "ns1/ew24" var e string = "ew2/dt32" var path = make([]string, 0 , 50) startTime := time.Now() shortestPath := ShortestPath(graph, s, e, path) elapsed := time.Since(startTime) fmt.Println(shortestPath) fmt.Println(elapsed) }
I picked two nodes (i.e. stations on the map) that are far apart and there are multiple paths available between the nodes, the starting node
ns1/ew24 and the ending node
ew2/dt32 and the shortest path can be visually seen on the following picture. I run each program 10 times and record the time taken for the algorithm to calculate the shortest path.
To run the Golang test code:
go run shortest.go
To run the Nodejs test code:
node shortest.js
To run the Python test code:
python3 shortest.py
The chart shows that when running on Macbook Pro, Golang algorithm on average took 393ms to calculate the shortest path, versus 1.191s for Nodejs and 2.25s for Python. In another word, Golang is about 3 times faster than Nodejs and about 5.7 times faster than Python.
The test on Raspberry Pi shown a similar result where Golang took 1.99s versus Nodejs’ 6.953s, versus Python’s 16.698s, it is 3.313 time faster than Nodejs, and 8.391 times faster than Python on Raspberry Pi.
On same programming language comparison on the two different platforms, Golang is roughly 5 times faster on MacBook Pro than Raspberry Pi, Nodejs is about 5.5 times faster on MacBook Pro than Raspberry Pi. For Python, MacBook Pro’s result is 7.4 times faster than Raspberry Pi.
The tests give me a better understanding of Golang’s performance on Raspberry Pi, and I will definitely consider to use Golang on Raspberry Pi for my future projects or even build a web service or web site using Golang in future.
Source codes
All source codes for the 3 implementations are available on my github Shortest Path Algorithm. | https://www.e-tinkers.com/2019/06/shortest-path-algorithm-revisit-with-golang/ | CC-MAIN-2020-16 | refinedweb | 1,380 | 61.26 |
In the Lotto, two numbers, one from 1 - 30 and a second from 31 - 60 are chosen, with each choice independent from the other and each of the possible numbers is equally likely to be chosen. If you match one number you receive $5 and if you match both numbers you receive $500. It costs $1 per play. Write a program that simulates playing the Lotto one million times. At the end of the simulation, print out the following:
1) The number of times exactly one number was matched.
2) The number of times exactly two numbers were matched.
3) The amount of money lost after buying the million lotto tickets.
For your simulation, you'll choose one winning lotto combination. Then, you'll simulate randomly choosing a million tickets, tallying up the winnings of each ticket.
Note: If you write the simulation properly, there is virtually no chance that you'll make money.
Sample Program Run:
You matched 1 number 64222 times.
You matched 2 numbers 1107 times.
You lost $125390.
I have this so far:
import random Match_One_Number = $5 Match_Two_Numbers = $500 Cost_Per_Play = $1 MAX_LOTTO_NUM1 = 30 MAX_LOTTO_NUM2 = 60 NUM_LOTTO_TRIALS = 1000000 def main(): # Seed the random number generator. random.seed() count = 0 total = 0 # Run the game NUM_LOTTO_TRIALS times. # def playLotto(): # Get first Lotto number. LOTTO_NUM1 = random.randint (1, MAX_LOTTO_NUM1) # Get second Lotto number. LOTTO_NUM2 = random.randint (31, MAX_LOTTO_NUM2) | http://www.dreamincode.net/forums/topic/292014-problem-with-how-to-use-the-program/page__pid__1702762__st__0 | CC-MAIN-2016-07 | refinedweb | 229 | 67.35 |
February 2019
Volume 34 Number 2
[Data Points]
Exploring the Multi-Model Capability of Azure Cosmos DB Using Its API for MongoDB
By Julie Lerman
In last month’s column (msdn.com/magazine/mt848702), and quite a few before that, I discussed different ways of working with Azure Cosmos DB, the globally distributed, multi-model database service supporting various NoSQL APIs. In all of my work thus far, however, I’ve used only one particular API—the SQL API—which allows you to interact with the data using SQL as the query language. One of the other models lets you interact with a Cosmos DB database using most of the tools and APIs available for MongoDB. This model also benefits from the BSON document format, a binary serialization format that’s compact, efficient and provides concise data type encoding. But how is it possible for a single database to be accessed through these and the other models (Cassandra, Gremlin and Table)? The answer is found in the underlying database engine, which is based on what’s called the atom-record-sequence (ARS) data model, enabling it to natively support a number of different APIs and data models. Each of the APIs is wire protocol-compatible to a popular NoSQL engine and data structure, such as JSON, by which you interact with the data.
It’s important to understand that the multi-model APIs are currently not interchangeable. Cosmos DB databases are contained in a Cosmos DB Account. You can have multiple Cosmos DB accounts in your Azure subscription, but when you create an account, you select which API you’ll be using for the databases in that account. Once selected, that’s the only API you can use for its databases. Azure documentation uses terms like “currently” when discussing this, so the expectation is that at some point there will be more flexibility along these lines.
I’ve been curious about trying out another API. Except from some exploration of Azure Table Storage a while ago (see my July 2010 article at msdn.com/magazine/ff796231), which is aligned with the Table API in Azure Cosmos DB, I haven’t ever used the other types of databases anyway. MongoDB is one of the most commonly used APIs, so that’s the one I decided to investigate, and I’ve been having fun with my first explorations. I’ll share some of what I’ve learned here, but please keep in mind that this is not intended as a “Getting Started with MongoDB” article. I’d recommend checking out Nuri Halperin’s Pluralsight courses (bit.ly/2SI2Vxw), which include beginner and expert MongoDB content. You’ll find links to many other resources within the article, as well.
The MongoDB support is targeted more toward developers and systems that are already using MongoDB, because Azure provides a lot of benefits. There’s even a guide for migrating data from existing MongoDB databases to Azure Cosmos DB (bit.ly/2FhzmPi).
The first benefit I was able to realize is that using MongoDB allows you to have a local instance of the database on your laptop to work with during development. While this is possible on Windows for the SQL and MongoDB APIs using the Cosmos DB Emulator (bit.ly/2sHNsAn), that emulator only runs on Windows. But you can install MongoDB—I’m using the Community Edition—on a variety of OSes, including macOS. This allows you to emulate the basic features of a Mongo DB API-driven Cosmos DB database locally. I’ll start by working locally, getting a feel for MongoDB and then switching to an Azure database.
You can find installation instructions for all supported platforms in the official MongoDB documents at bit.ly/2S96ywj. Alternatively, you can pull a Docker image for running MongoDB on macOS, Linux or Windows from hub.docker.com/_/mongo.
Once it’s installed, you start the process using the mongod.exe command. Unless otherwise specified, MongoDB expects you to have the directory /data/db created and to have permission to access. You can create this in the default location (for example, c:\data\db in Windows or in macOS, in the root folder where the Application, Library and Users folders live), or specify the location as a parameter of the “mongod” command. Because I’m just testing things out on my dev machine, I used “sudo mongod” to ensure that the service had the needed permissions. The Community Edition will run by default at localhost, port 27017, that is, 127.0.0.1:27017.
There are quite a few ways to interact with MongoDB. While I’m most interested in the C# API, I find it useful to start by working as close to “metal” as possible and then graduate to one of the APIs. If you’re totally new to MongoDB, you might want to start by using its shell (installed along with the service) to do some work at the command line. You can start the shell just by typing “mongo.” MongoDB installs three system databases: local, admin and config. In the shell, type “show dbs” to see them listed.
MongoDB doesn’t have an explicit command to create a new database in the shell or other APIs. Instead, you use a database and the first time you insert data into it, if it doesn’t exist, it will be created. Try this out with:
use myNewDatabase
If you call “show dbs” right afterward, you won’t see myNewDatabase yet.
The shell uses a shortcut “db” to work with the current database object even if the actual database doesn’t yet exist.
Now you need to insert a document. You create documents as JSON and the API will store them into MongoDB in its binary BSON format. Here’s a sample document:
{ firstname : "Julie", lastname : "Lerman" }
But documents don’t go directly in the database; they need to be stored in a collection. MongoDB follows the same behavior with collections as it does for the database: If you refer to a collection that doesn’t yet exist, it will create it for you when insert-ing data into that collection. Therefore, you can reference a new collection while inserting a new document. Note that every-thing is case-sensitive. I’ll use the insertOne method on a new collection called MyCollection to insert the document. Another document is returned that acknowledges that my document was inserted, and MongoDB provides a unique id key to my inserted document using its own data type, ObjectId:
> db.MyCollection.insertOne({firstname:"Julie",lastname:"Lerman"}) { "acknowledged" : true, "insertedId" : ObjectId("5c169d4f603846f26944937f") }
Now “show dbs” will include myNewDatabase in its list and I can query the database with the “find” command of the collec-tion object. I won’t pass any filtering or sorting parameters, so it will return every document (in my case, only one):
>db.MyCollection.find() { "_id" : ObjectId("5c169d4f603846f26944937f"), "firstname" : "Julie", "lastname" : "Lerman" }
I’ve barely scratched the surface of the capabilities, but it’s time to move on. Exit the mongo shell by typing “exit” at the prompt.
Using the Visual Studio Code Cosmos DB Extension
Now that you’ve created a new database and done a little work in the shell, let’s benefit from some tooling. First, I’ll use the Azure Cosmos DB extension in Visual Studio Code. If you don’t have VS Code, install it from code.visualstudio.com. You can then install the extension from the VS Code extensions pane.
To open the local MongoDB instance in the extension, right-click on Attached Database Accounts and choose “Attach Database Account.” You’ll be prompted to choose from the Cosmos DB APIs. Select MongoDB. The next prompt is for the address where the database should be found. This will default to the MongoDB default: mongodb://127.0.0.1:27017. Once connected, you should be able to see the databases in the Cosmos DB explorer, including the one created in the shell with its collection and document, as shown in Figure 1.
Figure 1 Exploring the MongoDB Server, Databases and Data
.png)
If you edit an opened document, the extension will prompt you to update it to the server. This will happen whether you’re connected to a local or to a cloud database.
MongoDB in a .NET Core App
Now let’s step it up another notch and use the MongoDB database in a .NET Core app. One of the various drivers available is a .NET driver (bit.ly/2BvUEFl). The current version, 2.7, is compatible with .NET Framework 4.5 and 4.6, as well as .NET Core 1.0 and 2.0 (including minor versions). I’m using the latest .NET Core SDK (2.2) and will start by creating a new console project in a folder I named MongoTest, using the dotnet command-line interface (CLI) command:
dotnet new console
Next, I’ll use the CLI to add a reference to the .NET driver for MongoDB, called mongocsharpdriver, into the project:
dotnet add package mongocsharpdriver
I’ll create a simple app, leaning on last month’s model with some classes related to the book and TV show, “The Expanse.” I have two classes, Ship and Character:
public Ship() { Crew=new List<Character>(); } public string Name { get; set; } public Guid Id { get; set; } public List<Character> Crew{ get; set;} } public class Character { public string Name { get; set; } public string Bio {get;set;} }
Notice that Ship has a Guid named Id. By convention, MongoDB will associate that with its required _id property. Character has no Id. I’ve made a modeling decision. In the context of interacting with ship data, I always want to see the characters on that ship. Storing them together makes retrieval easy. Perhaps, however, you’re maintaining more details about characters elsewhere. You could embed an object that only has a reference to character Id’s, for example:
public List<Guid> Crew{ get; set;}
But that means having to go find them whenever you want a ship with its list of characters. A hybrid alternative would be to add an Id property to Character, enabling me to cross-reference as needed. As a sub-document, the Character’s Id would be just a random property. MongoDB requires only a root document to have an Id. But I’ve decided not to worry about the Id of Character for my first explorations.
There are many decisions to be made when modeling. Most importantly, if your brain defaults to relational database concepts, where you need to do a lot of translation between the relational data and your objects, you’ll need to stop and consider the document database patterns and merits. I find this guidance on modeling document data for NoSQL database in the Azure Cosmos DB docs to be very helpful: bit.ly/2kpF46A.
There are a few more points to understand about the Ids. If you don’t supply a value to the ship’s Id property, MongoDB will create the value for you, just as SQL Server or other databases would. If the root document doesn’t have any property that maps to the _id of the stored document (by convention or your own mapping rules), it will fail when attempting to serialize results where the _id is included.
Working with the mongocsharpdriver API
The .NET driver’s API starts with a MongoClient instance and you work from there to interact with the database and collection and documents. The API reflects some of the concepts I already demonstrated with the shell. For example, a database and collection can be created on the fly by inserting data. Here’s an example of that using the new API:
private static void InsertShip () { var mongoClient = new MongoClient (); var db = mongoClient.GetDatabase ("ExpanseDatabase"); var coll = db.GetCollection<Ship> ("Ships"); var ship = new Ship { Name = "Donnager" }; ship.Characters.dd(new Character { Name = "Bobbie Draper", Bio="Fierce Marine"}); coll.InsertOne (ship); }
Where I used the command “use database” in the shell, I now call GetDatabase on the MongoClient object. The database object has a generic GetCollection<T> method. I’m specifying Ship as the type. The string “Ships” is the name of the collection in the database. Once that’s defined, I can InsertOne or InsertMany, just like in the shell. The .NET API also provides asynchronous counterparts, such as InsertOneAsync.
The first time I ran the InsertShip method, the new database and collection were created along with the new document. If I hadn’t inserted the new document and had only referenced the database and collection, they wouldn’t have been created on the fly. As with the shell, there’s no explicit command for creating a database.
Here’s the document that was created in the database:
{ "_id": { "$binary": "TbKPi3+tLUK9b68lJkGaww==", "$type": "3" }, "Name": "Donnager", "Characters": [ { "Name": "Bobbie Draper", Bio: "Fierce Marine" } ] }
What’s more interesting (to me), however, is the typed collection (GetCollection<Ship>). The MongoDB documentation describes a collection as “analogous to tables in relational databases” (bit.ly/2QZcOcD), which is an interesting description for a document database where you can store random, unrelated documents into a collection. Still, tying a collection to a particular type, as with the “ships” collection, does suggest that I’m enforcing the schema of the ship type in this collection. But this is for the Collection instance, not the physical collection in the database. It informs the particular instance how to serialize and deserialize objects, given that you can store data from any object into a single collection. As of version 3.2, MongoDB did add a feature that enforces schema validation rules, though that’s not the default.
I can use the same Ships collection for other types:
var collChar = db.GetCollection<SomeOtherTypeWithAnId> ("Ships");
However, this would create a problem when it’s time to retrieve data. You’d need a way to identify document types in the collection. If you read last month’s article about the Cosmos DB provider for EF Core (which uses the SQL API), you may recall that when EF Core inserts documents into Cosmos DB, it adds a Discriminator property so you can always be sure what type a document aligns to. You could do the same for the MongoDB API, but that would be a bit of a hack because MongoDB uses type discriminators for specifying object inheritance (bit.ly/2sbHvgA). I’ve added a new class, DecommissionedShip, that inherits from Ship:
public class DecomissionedShip : Ship { public DateTime Date { get; set; } }
The API has a class called BsonClassMap used to specify custom mappings, including its SetDiscriminatorIsRequired method. This will inject the class name by default. Because you’ll be overriding the default mapping, you need to add in the Automap method, as well.
I’ve added a new method, ApplyMappings, into program.cs and am calling it as the first line of the Main method. This specifically instructs the API to add discriminators for Ship and DecommissionedShip:
private static void ApplyMappings () { BsonClassMap.RegisterClassMap<Ship> (cm => { cm.AutoMap (); cm.SetDiscriminatorIsRequired (true); }); BsonClassMap.RegisterClassMap<DecommissionedShip> (cm => { cm.AutoMap (); cm.SetDiscriminatorIsRequired (true); }); }
I’ve modified the InsertShip method to additionally create a new DecommissionedShip. Because it inherits from Ship, I can use a single Ship collection instance and its InsertMany command to add both ships to the database:
var decommissionedShip=new DecommissionedShip{Name="Canterbury", Date=new DateTime(2350,1,1)}; coll.InsertMany(new[]{ship,decommissionedShip});
Both documents are inserted into in the Ships collection and each has a discriminator added as property “_t.” Here’s the DecommissionedShip:
{ "_id": { "$binary": "D1my7H9MrkmGzzJGSHOZfA==", "$type": "3" }, "_t": "DecommissionedShip", "Name": "Canterbury", "Characters": [], "Date": { "$date": "2350-01-01T05:00:00.000Z" } }
When retrieving the data from a collection typed to Ship, as in this GetShip method:
private static void GetShips () { var coll = db.GetCollection<Ship> ("Ships"); var ships = coll.AsQueryable ().ToList (); }
the API reads the discriminators and materializes both the Ship and DecommissionedShip objects with all of their data intact, including the Date assigned to the DecommissionedShip.
Another path for mapping is to use a BsonDocument typed collection object that isn’t dependent on a particular type. Check my blog post, “A Few Coding Patterns with the MongoDB C# API”, to see how to use BsonDocuments, as well as how to encapsulate the MongoClient, Database and Collection for more readable code.
Use LINQ for Querying
You can retrieve documents with the .NET API using API methods or LINQ. The API uses a very rich Find method (similar to the shell’s find method), which returns a cursor. You can pass in filters, project properties and return objects using one of its execution or aggregation methods—many of which look like LINQ methods. The .NET API Find method requires a filter, so to get any and all documents, you can filter on new (empty) BsonDocument, which is a filter matching any document. For LINQ, you first need to transform a collection to an IQueryable (using AsQueryable()) and then use the familiar LINQ methods to filter, sort and execute. If you didn’t include or map the _id property in your classes, you’ll need to use projection logic to take that into account as it will be returned from the query. You can refer to the documentation or to other articles (such as the great series by Peter Mbanugo at bit.ly/2Lqqw2J) to learn more of these details.
Switching to Azure Cosmos DB
After you’ve worked out your persistence logic locally against the MongoDB instance, eventually you’ll want to move it to the cloud-based Cosmos DB. Visual Studio Code’s Azure Cosmos DB extension makes it easy to create a new Cosmos DB account if you don’t have one yet, although you’ll likely want to tweak its settings in the portal. If you’re using Visual Studio, the Cloud Explorer for VS2017 extension has features for browsing but not creating databases, so in that case you’ll need to use the Azure CLI or work in the portal.
Here’s how you can create a new instance with the Azure Cosmos DB API for MongoDB from scratch using the VS Code extension.
First, you’ll need VS Code to be connected to your Azure subscription. This requires the Azure Account extension (bit.ly/2k1phdp), which, once installed, will help you connect. And once connected, the Cosmos DB extension will display your subscriptions and any existing databases. As with the MongoDB local connection shown in Figure 1, you can drill into your Cosmos DB accounts, databases, collections and documents (the Cosmos DB terms for these are containers and items). To create a brand-new account, right-click on the plus sign at the top of the extension’s explorer. The workflow will be similar to creating a local MongoDB database, as I did earlier. You’ll be prompted to enter an account name. I’ll use datapointsmongodbs. Next, choose MongoDB from the available APIs and either create a new Azure resource or choose an existing one to tie to the account. I created a new one so that I can cleanly delete the resource and the test database as needed. After this, you have to select from among the datacenter regions where this one should be hosted. I live in the eastern United States so I’ll pick the East US location. Given that Cosmos DB is a global database, you can control the use of regions in the portal or other apps, but I won’t need that for my demo. At this point, you’ll need to wait a few minutes while the account is created.
Once the new account is created, it will show up in the explorer. Right-click the account and select the “Copy Connection String” option. You can use this to change the MongoDB driver to point to the Azure Cosmos DB instance instead of pointing to the default local instance, as I’ve done here:
var connString= "mongodb://datapointsmongodbs:****.documents.azure.com:10255/?ssl=true"; ExpanseDb=new MongoClient(connString).GetDatabase("ExpanseDatabase");
I’ll run a refactored version of the method that inserts a new Ship and a new DecommissionedShip into the Ships collection of the ExpanseDatabase. After refreshing the database in the explorer, the explorer displays the newly created database in my Azure account, collection and documents in the Cosmos DB database, as shown in Figure 2.
Figure 2 The Newly Created Database, Collection and Documents in the Cosmos DB Database
.png)
Not a Mongo DB Expert, but a Better Understanding of Multi-Model
The availability of this API is not meant to convince users like me with decades of experience with SQL to switch to using MongoDB for my Cosmos DB databases. There would be so much for me to learn. The real goal is to enable the myriad developers and teams who already use MongoDB to have a familiar experience while gaining from the many benefits that Azure Cosmos DB has to offer. I undertook my own exploration into the Azure Cosmos DB API for MongoDB to gain a better understanding of the Cosmos DB multi-model capability, as well as to have a little fun checking out a new database. And, hopefully, my experience here will provide some high-level guidance for other developers or clients in the future..
Thanks to the following technical expert for reviewing this article: Nuri Halperin (Plus N Consulting)
Discuss this article in the MSDN Magazine forum | https://docs.microsoft.com/en-us/archive/msdn-magazine/2019/february/data-points-exploring-the-multi-model-capability-of-azure-cosmos-db-using-its-api-for-mongodb | CC-MAIN-2020-24 | refinedweb | 3,578 | 54.02 |
_browseinfoA structure
Contains parameters for the SHBrowseForFolder function and receives information about the folder selected by the user.
Syntax
typedef struct _browseinfoA { HWND hwndOwner; PCIDLIST_ABSOLUTE pidlRoot; LPSTR pszDisplayName; LPCSTR lpszTitle; UINT ulFlags; BFFCALLBACK lpfn; LPARAM lParam; int iImage; } BROWSEINFOA, *PBROWSEINFOA, *LPBROWSEINFOA;
hwndOwner
Type: HWND
A handle to the owner window for the dialog box.
pidlRoot
Type: PCIDLIST_ABSOLUTE
A PIDL that specifies the location of the root folder from which to start browsing. Only the specified folder and its subfolders in the namespace hierarchy appear in the dialog box. This member can be NULL; in that case, a default location is used.
pszDisplayName
Type: LPTSTR
Pointer to a buffer to receive the display name of the folder selected by the user. The size of this buffer is assumed to be MAX_PATH characters.
lpszTitle
Type: LPCTSTR
Pointer to a null-terminated string that is displayed above the tree view control in the dialog box. This string can be used to specify instructions to the user.
ulFlags
Type: UINT (0x00000001)
0x00000001. Only return file system directories. If the user selects folders that are not part of the file system, the OK button is grayed.
BIF_DONTGOBELOWDOMAIN (0x00000002)
0x00000002. Do not include network folders below the domain level in the dialog box's tree view control.
BIF_STATUSTEXT (0x00000004)
0x00000004. Include a status area in the dialog box. The callback function can set the status text by sending messages to the dialog box. This flag is not supported when BIF_NEWDIALOGSTYLE is specified.
BIF_RETURNFSANCESTORS (0x00000008)
0 (0x00000010)
0x00000010. Version 4.71. Include an edit control in the browse dialog box that allows the user to type the name of an item.
BIF_VALIDATE (0x00000020)
0 (0x00000040)
0.
BIF_BROWSEINCLUDEURLS (0x00000080)
0UI
Version 5.0. Use the new user interface, including an edit box. This flag is equivalent to BIF_EDITBOX | BIF_NEWDIALOGSTYLE.
BIF_UAHINT (0x00000100)
0x00000100. Version 6.0. When combined with BIF_NEWDIALOGSTYLE, adds a usage hint to the dialog box, in place of the edit box. BIF_EDITBOX overrides this flag.
BIF_NONEWFOLDERBUTTON (0x00000200)
0x00000200. Version 6.0. Do not include the New Folder button in the browse dialog box.
BIF_NOTRANSLATETARGETS (0x00000400)
0x00000400. Version 6.0. When the selected item is a shortcut, return the PIDL of the shortcut itself rather than its target.
BIF_BROWSEFORCOMPUTER (0x00001000)
0x00001000. Only return computers. If the user selects anything other than a computer, the OK button is grayed.
BIF_BROWSEFORPRINTER (0x00002000)
0x00002000. Only allow the selection of printers. If the user selects anything other than a printer, the OK button is grayed.
In Windows XP and later systems, the best practice is to use a Windows XP-style dialog, setting the root of the dialog to the Printers and Faxes folder (CSIDL_PRINTERS).
BIF_BROWSEINCLUDEFILES (0x00004000)
0x00004000. Version 4.71. The browse dialog box displays files as well as folders.
BIF_SHAREABLE (0x00008000)
0x00008000. Version 5.0. The browse dialog box can display sharable resources on remote systems. This is intended for applications that want to expose remote shares on a local system. The BIF_NEWDIALOGSTYLE flag must also be set.
BIF_BROWSEFILEJUNCTIONS (0x00010000)
0x00010000. Windows 7 and later. Allow folder junctions such as a library or a compressed file with a .zip file name extension to be browsed.
lpfn
Type: BFFCALLBACK
Pointer to an application-defined function that the dialog box calls when an event occurs. For more information, see the BrowseCallbackProc function. This member can be NULL.
lParam
Type: LPARAM
An application-defined value that the dialog box passes to the callback function, if one is specified in lpfn.
iImage
Type: int
An integer value that receives the index of the image associated with the selected folder, stored in the system image list. | https://docs.microsoft.com/en-us/windows/desktop/api/shlobj_core/ns-shlobj_core-_browseinfoa | CC-MAIN-2018-43 | refinedweb | 602 | 60.21 |
Today's Little Program adds a folder to the Documents library. Remember that Little Programs do little to no error checking.
Today's smart pointer library is… (rolls dice)… nothing! We're going with raw pointers.
->Release(); CoUninitialize(); return 0; }
This program uses some helper functions for manipulating libraries.
The
SHLoadLibraryFromKnownFolder
function
is a shorthand for
CoCreateInstance(CLSID_ followed by
IShellLibrary::,
and the
SHAddFolderPathToLibrary function
is a shorthand for
SHCreateItemFromParsingName
followed by
IShellLibrary::.
Run this program with the full path (or paths) to the folders you want to add to the Documents Library, and… nothing happens.
Ah, because there's a gotcha with libraries: After you make a change to a library, you need to commit your changes. So let's fix that:
->Commit(); // add this line library->Release(); CoUninitialize(); return 0; }
Okay, let's try it again. Run this program with the full path (or paths) to the folders you want to add to the Documents Library, and hooray! the folders are added to the Documents Library.
Makes one wonder. Is there a sane use-case where one would want to AddFolderPathsToLibrary, but not commit afterwards?
I think the Commit is a performance thing. Rebuilding the library after each individual Add would create wasted work if you were adding more than one.
Ah, makes sense. Thanks!
Well, they could commit on the final release, but doing important work when cleaning up is bad design.
Somebody totally needs to actually create a Smart Pointer Library Die to give to Raymond for Christmas.
Psst. Here’s a secret: The dice are loaded.
That just means we need to make an easy way to weight them.
I would totally buy some for my coworkers for Christmas, if any of them read this blog.
I’m pretty much certain that the last place I worked at actually had a ‘Delimiter of the day’ dice…
…and no. Chr(0) is NOT a good choice for joining strings! (I wish I was joking!)
There is plenty of precedence for using ‘\0’ to separate strings, such as environment blocks and REG_MULTI_SZ. It’s actually not particularly inconvenient in C with C-style strings.
I love the pointer dice roll (even if no actual dice are involved).
Same. Unfortunately it’s one of those things I enjoy that if I tried to show and explain it to anyone else I know they’d think I was weird.
Why is this API available? Only the user himself (through Explorer) should be able to organize the Libraries, by exactly the argument as for the pin-to-taskbar feature.
Speaking of sane use-cases…. what would be the use case for a software (most likely during the installation process) to create document storage outside the user profiles document directory and adding that to the library instead of creating a directory INSIDE the users regular documents folder?
Wouldn’t this circumvent all of windows’ profile management? Like, those additional directories would not be backuped along with the rest of the users profile*, it would not be moved to a data partition if a user tries to split up his system in a OS and data partition**
Where would be a suggested location for an additional application data directory that could be added to the document library? (in a safe and clean way)
* if not specified separately
** assuming as somehow sane that some user data will always be stored within the OS partition
OneDrive, Dropbox, and SharePoint document libraries come to mind. You don’t really want them to roam with a user’s profile because, hey, they already roam a different way, and if you have a greedy synchronization stack (“up to date even before you log in!”) you don’t want them to invalidate a user’s profile. You may even want a different set of permissions (to line up with permissions on the remote site) that wouldn’t be reset by an overzealous “fix” to the user’s profile folder.
Granted, you could easily accomplish all this and more with a shell namespace extension, but COM is hard, so let’s just create an icon overlay and go shopping! | https://blogs.msdn.microsoft.com/oldnewthing/20161107-00/?p=94655 | CC-MAIN-2018-22 | refinedweb | 690 | 62.68 |
combine2xlsx is a utility to combine multi Microsoft Excel files into a large one(.xlsx). Currently it only supports xls and xlsx files as input.
Go to combine2xlsx in pypi.
The maximum row number of xls is only 65536. Thus, you cannot merge it as an xls file. And the xlwt module doesn’t support the xls format.
Secondly, the pandas module’s API seems to be simple enough, but it is quite slow, and memory-inefficient.
First, you can install it via
$ pip3 install combine2xlsx
Example:
import combine2xlsx combine2xlsx.combine(['input1.xls', 'input2.xlsx'], 'outputname.xlsx')
If you’d like to have a development environment for combine2xlsx, you should create a virtualenv and then do pip install -e . from within the. | https://pypi.org/project/combine2xlsx/ | CC-MAIN-2017-04 | refinedweb | 122 | 60.11 |
Stability of LoPy in nano gateway mode?
Hi,
I am running two LoPy devices since some days and one is the nano gateway. The first time I was able to run the gateway about a day and the second time I was able to run it about three days.
Then it stopped. The blue LED did no more blink, the telnet server was no more reachable. After a reset all is fine again.
I run the last firmware or the second last one on the gateway. I think the second last and the last on my node.
Is this a known issue?
What is about opening UDP port for everyone? That may be the cause and I should open it only for the ttn network :-)
Thanks, Lothar
@lollisoft Thanks for this information! I'll try this!
@harix I have initially opened the udp port in my firewall and thus, it might be any hacking trials coming in to the port. After removing the rule, all worked well since some months. So be aware of this and it is probably to the limited amount of RAM available in the device. The firewall knows what incoming IP addresses are allowed to pass due to prior outgoing traffic to that server and thus allows udp packages from that server only flow back. For me that is a reasonable explanation.
I am experiencing the same problem. After around 3000 packets received (sender sends every 2 sec) the nano gateway stops working. I have modified the nano-gateway code to run without ACK each packet received. Even a "soft reboot" did not solve the issue. A power off / power on cycle was necessary to get it receiving again. I have tested with the latest firmware 1.7
@jmarcelino Maybe it was the open UDP port. Actually, with a closed port I still receive Pull Ack and Push Ack messages. So I learned a bit more about UDP and firewalls :-)
If it runs stable, then there was some foreign traffic, the system could not work with and probably freezed.
I'll see.
@lollisoft
Sadly that is a MPSSE cable, I think - but not 100% sure - the FTDI chip inside is set to MPSSE mode (JTAG,I2C,etc) mode and so the UART mode you need is disabled.
@jmarcelino I think, I can use my FPGA ZPU programming cable (C232HM-DDHSL-0). I used that for the CPU programming within my FPGA and that is a 3V3 Xilinx Spartan 6 based chip. I am pretty sure, that this is usable.
@lollisoft
You can find USB Serial TTL adapters for about 5 Euros, try looking on Ebay for example. Look for CP2104 for example (CP2102 also works but not as good). Make sure it supports 3.3V
Then just set to 3.3V connect RX, TX, GND
I really recommend having something to monitor the serial port of the Pycom boards, many errors happen at the low level (ESP-IDF) and outside the control of the MicroPython. If not the baseboard (easiest) then one of these adapters.
@jmarcelino said in Stability of LoPy in nano gateway mode?:
@lollisoft
Did you add the suggested capacitors to your 78S05? That said I don't think power is your issue especially as you're powering from 5V which gets regulated again.
In front I have a 220 uF and on both sides I have also 100nF. I may add some more to the LoPy as the breadboard is likely the case for the spikes (long copper wires and two breadboards).
Here is my crappy work:
You should monitor the serial console for errors.
No base board. I have only one. I need a plain dil chip to enable usb to serial functionality. It is a bit too much prototype :-)
I also don't think the LoPy Nanogateway is "bulletproof" code, it's more proof of concept and the first version. I remember Daniel writing here they were working on improvements.
At least I tried to improve a bit the memory consumption by moving buffer creation into the udp_lock code block.
I also tried to use the WDT class, but that is not available at the LoPy. Will it be available and if, when?
Also I think of buying a ttn gateway, if that makes sense (more users, reach and ROI).
I am planning a project around code generating the python code and infrastructure code around an IoT solution as a practical reference project for my open source project, I regularly post about in twitter :-)
That's the ROI factor..
I am using a Fritz Box router and I am not aware of the firewall capabilities but now trying without that open udp port. I'll see it soon or later.
@lollisoft
Did you add the suggested capacitors to your 78S05? That said I don't think power is your issue especially as you're powering from 5V which gets regulated again.
You should monitor the serial console for errors.
I also don't think the LoPy Nanogateway is "bulletproof" code, it's more proof of concept and the first version. I remember Daniel writing here they were working on improvements..
Here is the powersupply measured with my DSM203. The toggling signal is my blinker from a CMOS 4060 circuit.
The signal seems to get some spikes, that also may cause a freeze :-)
I need to tell more about my simple gateway implementation - hardware wise.
I have implemented a power supply with a simple 78S05 and feeding the 5V into the corresponding inputs of the LoPy board. I have only one wire from the 3V3 open to save boot occasionally. Else this wire is open. The obvious next connection is the LoRa antenna. That's it.
My question: Could it be that any remaining pin on my breadboard must be applied with a proper GND or 3V3 level or with the help of some pull ups? Can it be that I make the LoPy stable by not doing that correctly?
I have bought the twin pack and the base board is running my node and maybe the base board keeps the containing LoPy stable.
@RobTuDelft Actually I have updated the gateway and it still freezes. Meanwhile I have monitored the free memory for some minutes and sometimes it drops down to below 5000 bytes. At the last freeze it did not dropped that low, but that is not a save answer to what actually happened.
The gateway code does not only watching for LoRa nodes sending data, but also sends a stat package every minute and also a pull data alarm every 25 seconds.
These two alarms may be the cause to drop the free memory as they may be running in paralell at some point in time.
Can this be optimized or is that exthaustly tested to not be a problem?
@livius Yes, meanwhile I have found these functions in micro python documentation.
I found that my gateway has an average of free memory between 30000 and 50000 bytes. But sometimes it drops below 10000 and even 5000.
I have inspected the code and I did not yet found any suspectible code I could try to improve. Even the UDP receive port gets only 1024 bytes and could not be a cause for a memory flood from any hacker in the world trying to send oversized UDP packets to my port 1700. I'll restrict my firewall to only ttn servers in the future.
How could I forward the memory stats as a node (of the gateway itself)?
I have seen, that every 60 seconds a stats packet is send. Can I attach any values as extra fields, such as free_mem?
@lollisoft
Memory monitoring you can do by calling
import gc print(str(gc.mem_free()))
you also can collect garbages by:
gc.collect()
@RobTuDelft Seems to be at least a candidate. I'll do that at the weekend. Thanks
- RobTuDelft last edited by
@lollisoft Start by upgrading the firmware to latest versions on both devices I would say. Latest version is 1.6.12.b1.
No, I was not debugging the device yet at all. Running on Mac OS X most of the time and if programming at LoPy I jump to my Windows machine and connect with Atom and PyMakr plugin via telnet.
I have two ideas: One is the open port worldwide that is not a good idea but for the start the easyest. And a memory issue. The memory issue is not anymore likely the cause, because the second run was the three day run.
I probably log something to a unix log server and also monitor the memory consumption via ttn.
How can I implement both (logging and memory monitoring)?
I am really new to python.
- RobTuDelft last edited by
Can you still see what's happening during the freeze via the usb-com connection? Maybe add some debugging statements in your code and see what's happening. | https://forum.pycom.io/topic/1107/stability-of-lopy-in-nano-gateway-mode | CC-MAIN-2018-47 | refinedweb | 1,491 | 73.58 |
Typescript and JavaScript are two widely known languages in the Software development companies, but what are their differences and what use cases are better suited for one over the other? In this blog, we will have a look at both of these languages and understand how they relate to one another, discuss their primary differences, and outline the benefits of each.
Table of Content
What is Javascript?
JavaScript is a scripting language which helps you to create interactive web pages. It follows rules of client-side programming, so it runs in the user's web browser without the need of any resource forms the web server. You can also use Javascript with another.
What is Typescript?
Javascript developmentlanguage. It is a stagnantly compiled language to write clear and simple Javascript code. It can be run on Node.js or any other browsers which supports ECMAScript 3 or newer versions.
Typescript provides optional static typing, classes, and interface. For a large JavaScript project adopting Typescript can bring you more robust software and easily deployable with a regular JavaScript application.
Read More: Top 5 Trending Javascript Framework 2018
History of Javascript and TypescriptHistory of Javascript
Netscape Communications Corporation programmer Brendan Eich created Javascript. It was meant to working Netscape navigator. However, after becoming a popular scripting tool, it has become LiveScript. Later on, it was renamed as JavaScript to reflect Netscape's support of Java within its browser.
Let’s see an important landmark in the history of Javascript:
- It was launched in September 1995, and It took just ten days to develop
It is an open-source programming language. It is designed by Anders Hejlsberg, designer of C# at Microsoft. It is licensed under Apache 2. We can call it a superset of Javascript. It is designed and developed especially for large application and Trans compile to Javascript. It means that Typescript is JavaScript with some extra loaded features.
Let’s see important landmarks from the History of Typescript:
- The typescript was first made public in the year 2012
- After two years of internal development, Typescript 0.9, released in 2013 at Microsoft.
- Additional support for generics Typescript 1.0 was released at Build 2014
- In July 2014, a new Typescript compiler came which is five times faster then it's previous version
- In July 2015, support for ES6 modules, namespace keyword, decorators added in Typescript
- In November 2016, an added feature like key and lookup types mapped types, and rest added in Typescript
- On 27 March, 2018 conditional types, the improved key and it’s intersection types supports added in the Typescript.
Difference between features of JavaScript and TypeScriptFeatures of Javascript
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- It is a cross-platform language.
- It is used for client side and server side.
- It is a flexible, powerful and dynamic language.
- It has huge active community of developers which makes it more popular language.
- It has extension of .js
- It has Strong Testing Workflow.
- Added Dependencies.
- It is a light weight and interpreted programming language.
- Features of Typescript
- It supports Static Typing.
- It supports optional parameter function.
- Better choice for large coding projects.
- Offers great productivity for developers.
- It is specially used in Client side.
- It has extension of .ts and .tsx.
- Code navigation and bug prevention.
- Code 'discoverability' & refactoring
- Additional Features for Functions
- Supports interfaces, sub-interfaces, classes, and subclasses
- Scalable HTML5 client-side development
- Rich IDE available with autocomplete and code navigation features.
- Class-based object-oriented with the inheritance of private members and interfaces.
- Typescript is a strongly type object oriented compile language.
- Typescript code is not understandable by any browsers and that’s why it is compiled and converted in to Javascript. | https://www.ifourtechnolab.com/blog/what-is-the-difference-between-typescript-and-javascript | CC-MAIN-2020-50 | refinedweb | 616 | 57.98 |
tag:blogger.com,1999:blog-40844588603812425162017-09-27T01:04:00.897-07:00Putting the tea into teamIvan Moore pipeline support for Consumer Driven ContractsWhen developing a system composed of services (maybe microservices) some services will depend on other services in order to work. In this article I use the terminology "consumer"<span style="font-size: x-small;">[1]</span> to mean a service which depends on another service, and "provider" to mean a service being depended upon. This article only addresses consumers and providers developed within the same company. I'm not considering external consumers here. <br /><br />This article is about what we did at <a href="">Springer Nature</a> to make it easy to run CDCs - there is more written about CDCs <a href="">elsewhere</a>.<br /><h2>CDCs - the basics</h2>CDCs (<a href="">Consumer Driven Contracts</a>) can show the developers of a provider service that they haven't broken any of their consumer services.<br /><br />Consider a provider service called Users which has two consumers, called Accounting and Tea. Accounting sends bills to users, and Tea delivers cups of tea to users.<br /><br /). <br /><h2>How we used to run CDCs</h2>We. <br /><h2>How we run them now</h2>Our <a href="">automated pipeline system</a> allows consumers to define CDCs in their own repository and declare which providers they depend upon in their pipeline metadata file. Using this information, the automated pipeline system adds a stage to the consumer's pipeline to run its "CDCs" against its providers, and also <i><b>in the provider's pipeline</b></i> to run its consumers' CDCs against itself. In our simple example earlier this means the pipelines for Users, Accounting, Tea and Marketing will be something like this:<br /><br /><b>Users:</b><br /><b><a href="" imageanchor="1"><img border="0" height="69" src="" width="320" /></a></b><br /><b>Accounting:</b><br /><a href="" imageanchor="1"><img border="0" height="69" src="" width="320" /></a><br /><b>Tea:</b><br /><a href="" imageanchor="1"><img border="0" height="68" src="" width="320" /></a><br /><br />i.e. Users runs Accounting and Tea CDCs <i>against itself</i> (in parallel) after it has been deployed. Accounting and Tea run their CDCs against Users before they deploy.<br /><br />This means that:<br /><ul><li>when a change is made to a consumer (e.g. Tea), its pipeline checks that its providers are still providing what is needed. This is quite standard and easy to arrange.</li><li>when a change is made to a provider (e.g. Users), its pipeline checks that it still provides what its consumers require. This is the clever bit that is harder to arrange. This is the point of CDCs.</li></ul><h2>Benefits of automation</h2>By automating this setup, providers don't need to do anything in order to incorporate their consumers' CDCs into their pipeline. The providers also don't have to do anything in order to get updated versions of their consumers' CDCs.<br /><br />The effort of setting up CDCs rests with the teams who have the dependency, i.e. the consumers. The consumers need to declare their provider (dependency) in their metadata file and define and maintain their CDCs.<br /><h2>Subtleties</h2>There are a few subtleties involved in this system as it is currently implemented.<br /><ul><li.</li><li.</li><li.</li><li.</li></ul><h2>Implementation notes</h2>The implementation of a consumer running its CDCs against its provider is relatively straightforward. The difficulties are when a provider runs its consumers' CDCs against itself.<br /><br /.<br /><br /.<br /><br /.<br /><br /><br /><sup>1</sup> Other terminology in use for consumer is "downstream" and for provider is "upstream". A consumer is a dependant of a provider. A provider is a dependency of a consumer. I sometimes use the word producer instead of provider.<br /><br />Copyright © 2016 Ivan MooreIvan Moore of automatically setting up pipelinesTo explain <a href="">automatically setting up pipelines</a>, I've prepared example code (<a href="">available here</a> - see the <a href="">license</a>) for <a href="">GoCD</a> using <a href="">gomatic</a> and made a <a href="">video showing the code running</a> - which I will refer to throughout the article. I could possibly have done this all by narrating the video - maybe I will in the future.<br /><h2>Inception creation</h2>The example includes a script (called <span style="font-family: Courier New, Courier, monospace;">create_inception_pipeline.py</span>) which creates the pipeline that will create the pipelines (you run this only once):<br /><br /><pre>from gomatic import GoCdConfigurator, HostRestClient, ExecTask, GitMaterial<br /><br />configurator = GoCdConfigurator(HostRestClient("localhost:8153"))<br /><br />pipeline = configurator\<br /> .ensure_pipeline_group("inception")\<br /> .ensure_replacement_of_pipeline("inception")\<br /> .set_git_material(GitMaterial("",<br /> polling=False))\<br /> .set_timer("0 0 * * * ?") # run on the hour, every hour<br />inception_job = pipeline.ensure_stage("inception").ensure_job("inception")<br />inception_job.ensure_task(ExecTask(["python", "inception.py"]))<br /><br />configurator.save_updated_config()<br /></pre><br />This creates a pipeline in GoCD (here running on <span style="font-family: Courier New, Courier, monospace;">localhost</span>) which runs <span style="font-family: Courier New, Courier, monospace;">inception.py</span> on a timer.<br /><br />The video starts with this script being run, and the "inception" pipeline has been created by time 0:19.<br /><h2>Inception</h2>The <span style="font-family: Courier New, Courier, monospace;">inception.py</span> script creates a pipeline for every repo of a particular github user. For a real system, you might want to do something more sophisticated; this example has been kept deliberately simple.<br /><br /><pre>from gomatic import GoCdConfigurator, HostRestClient, ExecTask<br />from github import Github, GithubException<br /><br />github = Github()<br />me = github.get_user("teamoptimization")<br />for repo in me.get_repos():<br /> try:<br /> print "configuring", repo.name<br /> configurator = GoCdConfigurator(HostRestClient("localhost:8153"))<br /><br /> pipeline = configurator\<br /> .ensure_pipeline_group("auto-created")\<br /> .ensure_pipeline(repo.name)\<br /> .set_git_url(repo.clone_url)<br /> job = pipeline\<br /> .ensure_initial_stage("bootstrap")\<br /> .ensure_job("configure-pipeline")<br />bootstrap.py</span> script described later, passing it the name of the repo/pipeline as an argument.<br /><br />In the video, the "inception" pipeline is triggered manually at time 0:20 (rather than waiting for the timer) and has finished by time 1:03 (and has no affect yet as the relevant user has no repositories).<br /><h2>The bootstrap stage</h2>In this example, the <span style="font-family: Courier New, Courier, monospace;">bootstrap.py</span> script creates a stage for every line of a file (called <span style="font-family: Courier New, Courier, monospace;">commands.txt</span><span style="font-family: inherit;">); this</span> <span style="font-family: 'Courier New', Courier, monospace;">commands.txt</span><span style="font-family: inherit;"> then they will be removed from the pipeline. Note that because of how gomatic works, if there is no difference as a result of removing then re-adding the stages, then no </span><span style="font-family: Courier New, Courier, monospace;">POST</span><span style="font-family: inherit;"> request will be sent to GoCD, i.e. it would be entirely </span>unaffected<span style="font-family: inherit;">.</span><br /><br /><pre>import sys<br />from gomatic import GoCdConfigurator, HostRestClient, ExecTask<br /><br />configurator = GoCdConfigurator(HostRestClient("localhost:8153"))<br /><br />pipeline_name = sys.argv[1]<br /><br />pipeline = configurator\<br /> .ensure_pipeline_group("auto-created")\<br /> .find_pipeline(pipeline_name)<br /><br />for stage in pipeline.stages()[1:]:<br /> pipeline.ensure_removal_of_stage(stage.name())<br /><br />commands = open("commands.txt").readlines()<br />for command in commands:<br /> command_name, thing_to_execute = command.strip().split('=')<br /> pipeline\<br /> .ensure_stage(command_name)\<br /> .ensure_job(command_name)\<br /> .ensure_task(ExecTask(thing_to_execute.split(" ")))<br /><br />configurator.save_updated_config()<br /></pre><br />A real bootstrap script might be much more sophisticated, for example, creating a build stage automatically for any repo which contains a certain file (e.g. <span style="font-family: Courier New, Courier, monospace;">build.xml</span> or <span style="font-family: Courier New, Courier, monospace;">maven.pom</span>) and creating deployment stage(s) automatically. The example <span style="font-family: Courier New, Courier, monospace;">bootstrap.py</span> script is as short as I could make it for the purposes of demonstrating the approach.<br /><br />In the video, the user creates a repository (from time 1:04 - 1:39) and then creates a <span style="font-family: Courier New, Courier, monospace;">commands.txt</span> file, commits and pushes (up to time 2:18). Rather than waiting for the timer, the "inception" pipeline is manually triggered at time 2:22 and by 2:43 the pipeline is created for "project1"<span style="font-family: inherit;">. Rather than wait for GoCD to run the new pipeline (which it would after a minute or so) it is manually triggered at time 2:54, and when it runs, it creates the stage defined in </span><span style="font-family: Courier New, Courier, monospace;">commands.txt</span><span style="font-family: inherit;">.</span><br /><span style="font-family: inherit;"><br /></span><span style="font-family: inherit;">In the video, at time 3:54 the user adds another line to </span><span style="font-family: Courier New, Courier, monospace;">commands.txt</span><span style="font-family: inherit;"> and commits and pushes. </span>Rather than wait for GoCD to run the pipeline (which it would after a minute or so) it is manually triggered at time 4:27, and when it runs, it adds the new stage defined in <span style="font-family: Courier New, Courier, monospace;">commands.txt</span>.<br /><span style="font-family: 'Courier New', Courier, monospace;"><br /></span>Copyright © 2015 Ivan Moore<br /><br />Ivan Moore setting up pipelinesScripting the set up your continuous integration (CI) server is better than <a href="">clicky clicky</a>, but it might be possible to do even better. If you have many pipelines that are very similar then you might be able to fully automate their set up. A bit like having your own, in house version of <a href="">Travis CI</a>.<br /><br />This article will use the <a href="">GoCD</a> terms "pipeline" and "stage" (a pipeline is somewhat like a "job" Jenkins, and a pipeline comprises one or more stages).<br /><br />This article describes (at a very high level) the system my colleague <a href="">Hilverd Reker</a> and I have set up to automatically create pipelines. This has built on experience I gained doing something similar with <a href="">Ran Fan</a> at a previous client, and being the "customer" of an automated CI configuration system at another previous client.<br /><h2>Inception</h2>We have a pipeline in our CI server to automatically create the pipelines we want. We have called this "inception", after <a href="">the film</a> - I think Ran Fan came up with the name.<br /><br />The inception pipeline looks for new things to build in new repositories, and sub directories within existing repositories, and creates pipelines as appropriate (using <a href="">gomatic</a>). (The inception process that Ran Fan and I wrote previously, looked for new things to build within "one large repo" (maybe the subject of a future blog article), and new branches of that repository).<br /><br />The advantage of having this fully automated, compared to having to run a script to get the pipeline set up, is that it ensures that all pipelines get set up: none are forgotten and no effort is required.<br /><br />Our inception job sets up a pipeline with only one stage, the bootstrap stage, which configures the rest of the pipeline. This keeps the inception job simple.<br /><h2>The bootstrap stage</h2>Some.<br /><h2>Implementation notes</h2>Our.<br /><h2>Example </h2>What would help right now would be an example - but that'll take time to prepare; watch this space (patiently) ...<br /><br />Copyright ©2015 Ivan Moore Ivan Moore the configuration of your CI server<h2>How do you configure your CI server?</h2>Most people configure their CI server using a web based UI. You can confirm this by searching for "<a href="">setting up Jenkins job</a>", "<a href="">setting up TeamCity build configuration</a>", "<a href="">setup ThoughtWorks Go pipeline</a>" etc. The results will tell you to configure the appropriate CI server through a web based UI, probably with no mention that this is not the only way.<br /><br />One of my serial ex-colleagues, <a href="">Nick Pomfret</a>,.<br /><h2>What is wrong with clicky-clicky? </h2>Clicky-clicky can be useful for quick experiments, or maybe if you only have one job to set up, but has some serious drawbacks. <br /><h2>It works - don't change it</h2>Once. <br /><h2>Lovingly hand crafted, each one unique</h2>Another.<br /><h2>Can't see the wood for the tabs </h2>Furthermore, web UIs often don't make it easy to see everything about the configuration of a job a compact format - some CI servers are better than others for that.<br /><h2>The right way - scripting</h2>If.<br /><br />In some cases a script for setting up a job can be much more readable than the UI because it is often more compact and everything is together rather than spread over one or more screens.<br /><h2>Fully automated configuration of jobs</h2>It can be very useful to script the setup of jobs so it is totally automatic; i.e. when a new project is created (e.g. a new repo is created, or a new directory containing a particular file, e.g. a <code class="filename">build.gradle</code> file,.<br /><br />There are some subtleties about setting up fully automated jobs which I won't go into here - maybe a future blog article.<br /><h2>Tools for scripting</h2>For GoCD, see <a href="">gomatic</a>. For other CI servers, please add a comment if you know of anything that is any good!<br /><br />Copyright ©2015 Ivan Moore Ivan Moore - scripting of GoCD configuration<a href="">Gomatic</a> has been released - it is a Python API for configuring ThoughtWorks <a href="">GoCD</a>. I worked on it with my colleague <a href="">Hilverd Reker</a>. There isn't any documentation yet - we'll add some. For the moment, I thought I'd just post a very brief article here to announce it and to show a simple example of using it.<br /><h2>Limitations</h2>We wrote it for our purposes and find it very useful; however, it has limitations (e.g. only really supports "Custom Command" task type) and allows you to <i>try</i> to configure GoCD incorrectly (which GoCD will refuse to allow). We will continue to work on it and will address its current limitations.<br /><br />It has only been tested using GoCD version<span class="version"> 14.2.0-377 - I think it doesn't yet work with other versions.</span><span class="revision-link"></span> <br /><h2>Install </h2>We've written it using Python 2 (for the moment - should be simple to port to Python 3 - which we might do in the future). You can install it using "pip":<br /><br /><span style="font-family: "Courier New",Courier,monospace;">sudo pip install gomatic</span><br /><h2>Create a pipeline </h2>If you wanted to configure a pipeline something like that shown in the <a href="">GoCD documentation</a> then you could run the following script:<br /><br /><span style="font-family: "Courier New",Courier,monospace; font-size: x-small;">#!/usr/bin/env python<br />from gomatic import *<br /><br />go_server = GoServerConfigurator(HostRestClient("localhost:8153"))<br />pipeline = go_server \<br /> .ensure_pipeline_group("Group") \<br /> .ensure_replacement_of_pipeline("first_pipeline") \<br /> .set_git_url("")<br />stage = pipeline.ensure_stage("a_stage")<br />job = stage.ensure_job("a_job")<br />job.add_task(ExecTask(['thing']))<br /><br />go_server.save_updated_config()</span><br /><h2>Reverse engineer a pipeline</h2>Gomatic can reverse engineer a gomatic script for an existing pipeline.<br /><br />If you run the following (we will make it easier to run this rather than having to write a script):<br /><br /><span style="font-family: "Courier New",Courier,monospace; font-size: x-small;">#!/usr/bin/env python<br />from gomatic import *<br />go_server = GoServerConfigurator(HostRestClient("localhost:8153"))<br />pipeline = go_server\<br /> .ensure_pipeline_group("Group")\<br /> .find_pipeline("first_pipeline")<br />print go_server.as_python(pipeline)</span><br /><br />this will print out the following text:<br /><br /><span style="font-family: "Courier New",Courier,monospace; font-size: x-small;">#!/usr/bin/env python<br />from gomatic import *<br /><br />go_server_configurator = GoServerConfigurator(HostRestClient("localhost:8153"))<br />pipeline = go_server_configurator\<br /> .ensure_pipeline_group("Group")\<br /> .ensure_replacement_of_pipeline("first_pipeline")\<br /> .set_git_url("")<br />stage = pipeline.ensure_stage("a_stage")<br />job = stage.ensure_job("a_job")<br />job.add_task(ExecTask(['thing']))<br /><br />go_server_configurator.save_updated_config(save_config_locally=True, dry_run=True)</span><br />This produces a script which does a "dry run" so you can run it to see what changes it will make before running it for real.<br /><h2>So what?</h2>I don't have time to write about why this is a Good Idea, or the consequences of being able to script the configuration of your CI server - but will do soon.<br /><br />[This article slightly updated as a result of a new release of gomatic] <br /><br />Copyright © 2014 Ivan MooreIvan Moore life easier for future software archaeologistsYesterday I went to "<a href="">The First International Conference on Software Archaeology</a>" run by <a href="">Robert Chatley</a> and <a href="">Duncan McGregor</a> - it was excellent. There were "lightning talks" run by <a href="">Tim Mackinnon</a> - here is a blog version of my talk.<br /><h2>Intro</h2>If you have worked on a piece of software that is running in production, but hasn't been changed for a while, you may have had to do some software archaeology to work out how to make changes to it.<br /><br />In this article, I list some problems that I've encountered when doing software archaeology, and some suggestions for making life easier for future software archaeologists.<br /><br />My suggestions are not always applicable - but please consider them carefully. It is valuable to your client to make it easier for future software archaeologists to work with your systems. If your systems are any good they will probably be used for much longer than you think.<br /><h2>Where's the source?</h2>Sometimes source code is lost (e.g. because of a VCS migration and some repositories don't get converted because nobody thinks they are needed any more). For Java projects there is a simple way to avoid losing the source code - include the source in your binary jars.<br /><h2>Where is the documentation?</h2>Although it is possible that the source code will be lost, more commonly, source code repositories do survive. However, documentation systems (for example wikis) are likely to be decommissioned sooner.<br /><br />Even if a documentation system isn't decommissioned, the information related to old projects can get deleted, become out of date or inconsistent with the version actually running.<br /><br />In order to keep documentation consistent with the system, please commit it to the same VCS repository as the code. Depending on the VCS system used, you might be able to <a href="">serve documentation to users directly from your source control system</a>.<br /><h2>Where are the dependencies?</h2.<br /><h2>How do I build the software?</h2.<br /><h2>How do I work on the software?</h2).<br /><br />Include (at the very least) instructions for how to set up a suitable development environment. Even better, commit the development tools and any setup scripts.<br /><h2>How do I run the code in the production environment?</h2>For a large system, it can be difficult to work out how the production servers are meant to be set up. Therefore, include instructions, or even better, scripts (like Puppet or Chef), for setting up any servers etc.<br /><h2>How did it get to be like it is?</h2>When looking at an old system, can be useful to see the history of decisions about how a system got to be like it is. It can be useful to have a changelog checked into the source code repository. In my lightning talk, <a href="">Nat Pryce</a> said that for a home project, he committed the complete bug tracker system; that could be very useful for a future archaeologist.<br /><h2>In conclusion</h2>F.<br /><br />Copyright © 2014 Ivan MooreIvan Moore! Learn how to use source control properlyThis article was prompted by a tweet by <a href="">Nat Pryce</a>: <br /><blockquote class="twitter-tweet">I wonder if there’d be interest in a grumpy but informative tutorial entitled something like “FFS! Learn how to use make properly”<br />— Nat Pryce (@natpryce) <a href="">May 9, 2013</a></blockquote><script async="" charset="utf-8" src="//platform.twitter.com/widgets.js"></script> I thought - similarly - how about source control?<br /><br /. <br /><h1>What everyone agrees on (right?)</h1><b>All files needed to run the build should be in source control</b>,).<br /><h1>Don't make me think about which files should or shouldn't be committed</h1><b>All files generated by your build should be ignored by source control.</b>That is, having run a build, if I haven't added any files myself, I shouldn't see any files available for adding to source control. That is so I don't accidentally commit files that shouldn't be committed.<br /><br /><b>Running the build should not modify any files that are in source control.</b>That is, having run a build, if I haven't modified any files myself, I shouldn't see any file modifications available for committing to source control. That is so I can see only the changes I've actually made and commit all of them.<br /><h1>Every-day use of source control</h1><b>Before committing, a developer should update and run the build to check that it is safe to commit.</b> ).<br /><br /><b>Commit everything</b> - <i>can </i. <br /><h1>Finally</h1>There are many different ways to use source control that are perfectly acceptable. Please comment if you disagree with the things I have written in this article.<br /><br />Copyright © 2013 Ivan MooreIvan Moore what works for youI've received literally no emails complaining that my <a href="">"do the right thing" methodology</a> is too prescriptive, so I've come up with a new methodology called "do what works for you" which I hope will work for those people who find the "do the right thing" methodology too prescriptive.<br /><br />What you do in this methodology is whatever works for you.<br /><br />Copyright © 2011 Ivan MooreIvan Moore 2011<a href="">My favourite conference (SPA)</a> is open for <a href="">registrations</a> and <a href="">session proposals</a>.<br /><br />This year I'm honoured to be conference co-chair with <a href="">Mike Hill</a>. The programme will be organised by <a href="">Willem Van Den Ende</a> and <a href="">Rob Bowley</a>.<br /><br />Please <a href="">book your place</a>, or <a href="">propose a session</a> (do that real soon - you'll have some time to improve your session once it is submitted).<br /><br />Copyright © 2011 Ivan MooreIvan Moore plural of anecdote is not dataI've just finished reading "<a href="">Bad Science</a>" and it made me think of how little science has been done about software development.<br /><br />The only two areas where there has been some research that I can think of <span style="opacity:0.5;filter:alpha(opacity=50)">(off the top of my head - without doing any research about research) (and that seems very relevant to my day-to-day work)</span> are about <a href="">pair programming</a> and <a href="">test driven development</a>.<br /><br />While I think it is commendable that people have done some research for these topics - it's just not enough (in particular, not by enough different groups or people).<br /><br />So - what good science is there about software development? Comments welcome.<br /><br />Copyright © 2010 Ivan MooreIvan Moore effecting codeI don't write Java code exactly the same as I used to. Some of the ways my code has changed are due to using an <a href="">excellent IDE</a>.<br /><br />One of these I mention in a <a href="">previous article</a> was about having fields public in some circumstances - I won't repeat the arguments here, I just want to mention that one reason I'd now make a field public when before I would have had a getter/setter is that it is trivial to convert a public field into a getter/setter when you need to (a refactoring called "encapsulate field"** in IDEA). (I still prefer not to have the internals of a class public whether accessed by fields or getters/setters though - <a href="">tell don't ask</a>.)<br /><br />Another example is that now I only introduce an interface when it's really needed and not in anticipation of it being needed. Again, it's trivial to introduce the interface when it's needed using the "extract interface" refactoring of the IDE.<br /><br />I was chatting to <a href="">Nat Pryce</a> about this and he was agreeing that using an <a href="">excellent IDE</a> has also changed the way he writes Java. I hope he and others will add comments to mention other ways their programming style has changed as a result of better IDEs.<br /><br />I know for some people the idea of changing your programming style as a result of what a tool supports is heresy - but I think good development practice means using the tools and language so they work well together.<br /><br />The examples given above refer to Java development where the team owns all the code rather than when writing an API - I'm not addressing API design here.<br /><br />** BTW, I think calling the refactoring "encapsulate" is a bit of an exaggeration - really it is just replacing one form of non-encapsulation with another.<br /><br />Copyright © 2010 Ivan MooreIvan Moore 2010 - Friday September 10th - BCS London<a href="">Mike Hill</a> and I have been volunteered to co-chair the miniSPA conference.<br /><br /><a href="">SPA</a> is a fantastic conference - miniSPA is a condensed (and free!) version - it'll be great - all the places will go, so book now.<br /><br />Here's the announcement and <a href="">registration link</a> (sorry the registration system is really horrible):<br /><blockquote><br />Experience some of the most popular sessions from this year's BCS SPA conference, for free, at miniSPA2010 on Friday September 10th at BCS London (near Covent Garden).<br /><br />The miniSPA2010 one-day programme features five sessions, in two streams, that give an excellent guide to the variety and quality you'll find at every SPA conference.<br /><br />We hope that attending miniSPA will encourage you to submit a session proposal for SPA2011, which will be taking place from June 12-15 (also at BCS London).<br /><br />For more information visit <a href=""></a>. Booking is essential. Places are limited so reserve yours now.<br /><br />See <a href=""></a> for details of our programme of regular events.<br /><br />©2010 BCS SPA | 5 Southampton Street | London | WC2E 7HA<br /></blockquote><br /><br />Copyright © 2010 Ivan MooreIvan Moore't just put your documentation in source controlIn the <a href="">GS04</a> course at <a href="">UCL</a> I told the students to put everything into <a href="">source control</a>; not just source code but also things like documentation and configuration files.<br /><br />That's all very well, but my current project at work has made me realise that you can do even better. You should not just put your documentation in source control, you should serve it from source control.<br /><br />On my current project we have all our documentation served directly from our <a href="">subversion</a> repository, mostly as html.<br /><br /><span style="font-weight: bold;font-size:130%;" >What about Wikis?</span><br /><br />I used to be a big fan of having a project <a href="">wiki</a>.<br /><br />A wiki can be great but:<br /><ol><li>they do have a tendency to get out of date easily</li><li>they can accumulate lots of garbage</li><li>they can be difficult to version control well (difficult to keep in sync with the project's source code repository - I know there are things like <a href="">Trac</a> but in a lot of companies you don't get to choose what systems you use)</li><li).</li></ol>Wikis still have their place - when collaboration with lots of people is needed, but for developer written documentation I'm happier to have it in the same source control system as the code it refers to.<br /><br /><span style="font-weight: bold;font-size:130%;" >Taking my own advice</span><br /><br />I've updated my semi-abandoned project <a href="">build-o-matic</a>, so its web site is now served directly from its source code repository. It's now <span style="font-style: italic;">so </span>much easier to update the web site (just edit and commit) that I might even get the web site up-to-date.<br /><br />But there again, the <a href="">World Cup</a> is on TV today ...<br /><br />Copyright © 2010 Ivan MooreIvan Moore nullMy colleagues told me of some code they came across which included the statement: "throw null".<br /><br />I'd never seen that before - I didn't know what it would do or even if it was valid.<br /><br />I'll let you think about it. Have a go if you want to check your answer:<br /><pre><br />public class Surprise {<br /> public static void main(String[] args) {<br /> throw null;<br /> }<br />}<br /></pre><br /><br />Copyright © 2010 Ivan MooreIvan Moore and Environments - SCM and CIWhen I taught source control and continuous integration in 2007 (for the <a href="">GS04</a> course at <a href="">UCL</a>) I used <a href="">Subversion</a> for the source control lab and <a href="">build-o-matic</a> for the continuous integration lab.<br /><br />In the labs this year, I'll be using <a href="">Mercurial</a> instead of Subversion, and <a href="">Hudson</a> instead of build-o-matic.<br /><br />What would you choose for teaching source control and continuous integration (and for bonus marks, why)?<br /><br />Copyright © 2009 Ivan MooreIvan Moore and Environments<a href="">Steve Freeman</a> and I are teaching a course at <a href="">UCL</a> called "Tools and Environments".<br /><span style="font-style: italic;">The course we wish we’d had in college, only we didn’t know it at the time.</span><br /><br />We cover subjects such as source control systems, automated builds, automated testing and continuous integration.<br /><br />In preparing for the course, I've been reminded of how few books there are which we can use as a "course text". There are plenty of books for specific tools (e.g. Ant) once you know that you need those tools, but few books which explain the sorts of things that you need for real software development projects, and why you need them.<br /><br />The book we're using for our "course text" is <a href="">Practical Development Environments</a> (and we'll also be recommending <a href="">Continuous Integration</a> as that also covers much of the material of the course).<br /><br />If you have other recommendations please add a comment!<br /><br />Copyright © 2009 Ivan MooreIvan Moore heresies<div>I encourage people to think for themselves rather than following cargo cults. You might or might not agree with the three heresies I've written about here, but do at least think about them.<br /><br /><strong><span style="font-size:130%;">Public fields</span></strong><br /><br />In Java code, instead of having a public getter and public setter for a field, why not just make the field public? It's much simpler and less code. If you later need a getter and setter for some reason you can always refactor to that (and many IDEs will give you help doing it). There is a comment by Richard Gomes at the end of this <a href="">previous article</a> on the subject of public fields for data objects. I think public fields make most sense for NOJOs (data objects) (in the rare case where a NOJO is useful - not very often) but maybe it would sometimes make sense for other sorts of classes too?<br /><br />Note that having public access to a field is not what I'm trying to encourage. The point I'm making is that if you <span style="font-style: italic;">do </span>have public access to a field then it doesn't matter much whether it is by getter/setter or making the field public, so you might as well use a public field as it is simpler. (But please, <a href="">tell don't ask</a> instead.)<br /><br /><strong><span style="font-size:130%;">Magic values instead of constants (in build files)</span></strong><br /><br />Instead of always factoring out magic values as properties in your build file, consider just using the magic value where it makes sense. For example, maybe instead of "${src}" just use "src" (and get rid of the property) - this was suggested by <a href="">Jeffrey Fredrick</a> at <a href="">CITCON Paris 2009</a>. I think there is a lot of merit in this approach. What are the chances that you'd be able to just modify the value of the "src" property and everything would still work? Probably quite low - you'd probably do a text file search for "src" anyway. What are the chances that you'll want to change it anyway? I think it's worth thinking about whether it's better or worse to factor out constants in some cases.<br /><br /><span style="font-weight: bold;font-size:130%;" >Make the CI build fail fast rather than run all the tests</span><br /><br />Rather than running all the tests in your CI build, how about have the build fail as soon as any test fails? That way, a failing build uses less of your build farm's capacity. If your build farm capacity is limited, then this approach may result in getting a passing build sooner (as when the fix is committed there may be a build agent available for running the build with that commit sooner because it's time isn't being taken running a build which will eventually fail anyway). I think it's often more important to know which commit broke the build than which tests failed in order to know both who should fix the build and what caused the build breakage. This approach might not be so good if you have a <a href="">flickering build</a> (i.e. randomly failing tests) - however, making the build reliable can be achieved and is worthwhile anyway.<br /><br /><span style="font-weight: bold;font-size:130%;" >More heresies to follow</span><br /><br />I have other heresies to write about. Please suggest your own in the comments.<br /><br />Copyright © 2009 Ivan Moore </div>Ivan Moore Enums with constant-specific methodsOne of my colleagues introduced me to this handy language feature of Java 1.5 and I wanted to write an article about it because I hadn't seen this before.<br /><br />Using google reveals that it is already well documented if you RTFM, but I will repeat it here because talking to other Java developers indicates that it isn't as well known as it deserves to be. Here's a slightly reworded extract from the first hit on google or bing for "<a href="">java enum</a>":<br /><br />You can declare abstract methods in an enum and override them with a concrete method in each constant. Such methods are known as constant-specific methods. Here is an example using this technique:<br /><pre><br />public enum Operation {<br /> PLUS { double eval(double x, double y) { return x + y; } },<br /> MINUS { double eval(double x, double y) { return x - y; } },<br /> TIMES { double eval(double x, double y) { return x * y; } },<br /> DIVIDE { double eval(double x, double y) { return x / y; } };<br /><br /> // Do arithmetic op represented by this constant<br /> abstract double eval(double x, double y);<br />}<br /></pre><br />Copyright © 2009 Ivan MooreIvan Moore version of Jester releasedIt's been a while since I last updated <a href="">Jester</a> (a mutation testing tool).<br /><br />Today I released a new version of Jester - not much changed - but hopefully a bit easier to get it to work, based on my <a href="">experiences of trying to use Jester</a> when I haven't tried for a while.<br /><br />It now doesn't read configuration files from the classpath - instead you specify the relevant files on the command line.<br /><br />Copyright © 2009 Ivan MooreIvan Moore London, 7th & 8th December 2009It's <a href="">XpDay</a> soon - <a href="">book your place now</a>. The <a href="">Keynotes</a> look particularly good this year.<br /><br />On Monday there's an experience report that looks very interesting "<a href="">When Agile Might Not Be The Best Solution</a>" - it's good to see this sort of experience report on the programme because there's probably more to learn from it than one which goes something like "we did XP and it worked".<br /><br />There are lots of other <a href="">interesting looking sessions</a> too - plus lots of open space sessions which can be excellent.<br /><br />Copyright © 2009 Ivan MooreIvan Moore Programming interviews/auditionsI have done a lot of pair programming interviews for my client. I enjoy doing them and I think they are extremely valuable.<br /><br />Hiring is probably the most important thing to get right, and I think that pair programming interviews (or "auditions" as some like to call them) are usually <a href="">the best way to interview</a> developers.<br /><br /><span style="font-weight: bold;font-size:130%;" >Setting up a pair programming interview</span><br /><br />For interviewing Java developers, I have a machine set up with a choice of <a href="">IntelliJ IDEA</a> and <a href="">Eclipse</a>.<br /><br />I allow one hour for these interviews - I have found that is long enough to get a good idea about the suitability of a candidate.<br /><br /><span style="font-size:130%;"><span style="font-weight: bold;">Choosing a problem</span></span><br /><br / <a href="">this article</a>.<br /><br / <a href="">WeakHashMap </a>from scratch if you are hiring for a typical enterprise IT project.<br /><br /><span style="font-weight: bold;font-size:130%;" >What </span><span style="font-weight: bold;font-size:130%;" >pair programming interviews demonstrate</span><br /><br /.<br /><br /.<br /><br /><span style="font-size:130%;"><span style="font-weight: bold;">Being realistic</span></span><br /><br /.<br /><br /><span style="font-weight: bold;font-size:130%;" >Giving something back</span><br /><br />I try to teach the candidates something new in a pair programming interview where possible. Often this is something like an IDE shortcut but is occasionally a language feature or a "<a href="">programming in the small</a>" style discussion. I like candidates to get something back for giving up their time to come in for an interview, and a pair programming interview can be very daunting for candidates not used to pair programming.<br /><span style="font-weight: bold;font-size:130%;" ><br />Does it work?<br /></span><br />As far as I can tell, all candidates that I have "passed" using a pair programming interview have turned out to be worth hiring.<br /><br />However, that doesn't include those candidates that I've "passed" who didn't take the job and I don't know whether any of those candidates that I've "failed" would have been good either.<br /><br />My suspicion is that it is a technique which is slightly more prone to "failing" good candidates than hiring poor candidates, but that really is just a gut feeling. If anyone knows any studies on pair programming interviews I'd be very interested to hear more.<br /><br /><span style="font-size:130%;"><span style="font-weight: bold;">Where it probably doesn't work</span></span><br /><br />I guess that interviewing people for research or work which requires solving deep and difficult problems probably requires a different approach. Also, for hiring people with limited programming experience who you want to train up it might not be suitable.<br /><br />Copyright © 2009 Ivan MooreIvan Moore codeI recommend the book "<a href="">Clean Code</a>" - <a href="">I completely agree with its philosophy</a> and have written a few articles of my own about "<a href="">programming in the small</a>".<br /><br /><a href="">Mike Hill</a> and I presented a session on "programming in the small" at the "<a href="">Software Craftsmanship</a>" conference 2009 in London and at <a href="">QCON London</a> 2009 - and one of or examples was taken from "Clean Code".<br /><br /><span style="font-weight: bold;font-size:130%;" >Clean Code</span><br /><br />One of the examples in "Clean Code" is some code for parsing command line arguments, written in Java by Bob Martin. It is shown as an example of code which has already been made clean. There is <a href="">an article</a> (separate from the book) by Bob Martin about the code we use for this example. The source code is available from github:<br /><br />git clone git://github.com/unclebob/javaargs.git<br /><br />Mike and I chose this code because we wanted to take code which was already quite clean and show how even good code can sometimes be cleaned up even more - we wanted to push the cleanliness as far as possible in the session.<br /><br />Just looking at the "Args" class only, this method seemed the one most wanting some further work (sorry, formatting is ugly - reformatted to fit blog page width):<br /><pre><br />private void parseSchemaElement(String element)<br /> throws ArgsException {<br /> char elementId = element.charAt(0);<br /> String elementTail = element.substring(1);<br /> validateSchemaElementId(elementId);<br /> if (elementTail.length() == 0)<br /> marshalers.put(elementId,<br /> new BooleanArgumentMarshaler());<br /> else if (elementTail.equals("*"))<br /> marshalers.put(elementId,<br /> new StringArgumentMarshaler());<br /> else if (elementTail.equals("#"))<br /> marshalers.put(elementId,<br /> new IntegerArgumentMarshaler());<br /> else if (elementTail.equals("##"))<br /> marshalers.put(elementId,<br /> new DoubleArgumentMarshaler());<br /> else if (elementTail.equals("[*]"))<br /> marshalers.put(elementId,<br /> new StringArrayArgumentMarshaler());<br /> else<br /> throw new ArgsException(INVALID_ARGUMENT_FORMAT,<br /> elementId, elementTail);<br />}<br /></pre><br />So - what could be better? What struck Mike and I was the duplication of "<span style="font-family:courier new;">marshalers.put(elementId, new XXX());</span>"<br /><br />To remove this duplication, first extract a variable called argumentMarshaler of type ArgumentMarshaler in each of the branches, then move the expression "<span style="font-family:courier new;">marshalers.put(elementId, argumentMarshaler);</span>" outside of the if statement, and the declaration of the variable "argumentMarshaler" before the if statement. You end up with:<br /><pre><br />private void parseSchemaElement(String element)<br /> throws ArgsException {<br /> char elementId = element.charAt(0);<br /> String elementTail = element.substring(1);<br /> validateSchemaElementId(elementId);<br /> ArgumentMarshaler argumentMarshaler;<br /> if (elementTail.length() == 0) {<br /> argumentMarshaler =<br /> new BooleanArgumentMarshaler();<br /> } else if (elementTail.equals("*")) {<br /> argumentMarshaler =<br /> new StringArgumentMarshaler();<br /> } else if (elementTail.equals("#")) {<br /> argumentMarshaler =<br /> new IntegerArgumentMarshaler();<br /> } else if (elementTail.equals("##")) {<br /> argumentMarshaler =<br /> new DoubleArgumentMarshaler();<br /> } else if (elementTail.equals("[*]")) {<br /> argumentMarshaler =<br /> new StringArrayArgumentMarshaler();<br /> } else<br /> throw new ArgsException(INVALID_ARGUMENT_FORMAT,<br /> elementId, elementTail);<br /> marshalers.put(elementId, argumentMarshaler);<br />}<br /></pre><br />Now it's clearer that this method is doing too many things - one of those things being to find the relevant marshaler. We can extract a method for finding the marshaler and, having been extracted can improve it further by removing unnecessary structured programmingness, ending up with:<br /><pre><br />private void parseSchemaElement(String element)<br /> throws ArgsException {<br /> char elementId = element.charAt(0);<br /> String elementTail = element.substring(1);<br /> validateSchemaElementId(elementId);<br /> marshalers.put(elementId,<br /> findAppropriateArgumentMarshaler(elementId,<br /> elementTail));<br />}<br /><br />private ArgumentMarshaler findAppropriateArgumentMarshaler(<br /> char elementId, String elementTail)<br /> throws ArgsException {<br /> if (elementTail.length() == 0) {<br /> return new BooleanArgumentMarshaler();<br /> } else if (elementTail.equals("*")) {<br /> return new StringArgumentMarshaler();<br /> } else if (elementTail.equals("#")) {<br /> return new IntegerArgumentMarshaler();<br /> } else if (elementTail.equals("##")) {<br /> return new DoubleArgumentMarshaler();<br /> } else if (elementTail.equals("[*]")) {<br /> return new StringArrayArgumentMarshaler();<br /> } else<br /> throw new ArgsException(INVALID_ARGUMENT_FORMAT,<br /> elementId, elementTail);<br />}<br /></pre><br />Notice that "elementId" is only used for the exception to throw if an appropriate ArgumentMarshaler cannot be found. Further investigation shows that actually this parameter isn't used in ArgsException for an "INVALID_ARGUMENT_FORMAT" and we can just delete this argument (and hence the "elementId" parameter of "findAppropriateArgumentMarshaler") with no change to the behaviour of the code!<br /><br />There is more that can be done with the Args class - but that is beyond the scope of this article.<br /><br /><span style="font-weight: bold;font-size:130%;" >Conclusion</span><br /><br />I hope this has shown that even clean code can be made cleaner - without having to do anything too clever or drastic. It's often easier to see such opportunities in other people's code or code you haven't seen for a while - even the best programmers can miss opportunities for making code simpler.<br /><br />Copyright © 2009 Ivan MooreIvan Moore management lessons - commitmentHave you ever heard (or said) something like "you've got to work [long hours/weekends] because the customer has been promised [some system/feature] by [some date]"?<br /><br /><span style="font-weight: bold;font-size:130%;" >Commitments can be made but not assigned</span><br /><br / <a href="">"death march" project</a>.<br /><br /><span style="font-weight: bold;font-size:130%;" >Estimates are not commitments</span><br /><br />As a project manager, you have to understand the <a href="">difference between an estimate and a quote</a>. <a href="">previous article</a> is "extreme planning".<br /><span style="font-weight: bold;font-size:130%;" ><br />Commitment can work wonders</span><br /><br /.<br /><br /.<br /><br /.<br /><br />There are lots of other factors involved in motivation - I might write more in a future article - if I can be bothered. :-)<br /><br /><span style="font-weight: bold;font-size:130%;" >Bike ride commitment</span><br /><br />As an example of commitment - I said I'd do the <a href="">London to Aachen bike ride</a> and people <a href="">sponsored me</a> to do it (many thanks), so I felt a commitment to do it. If I hadn't felt any commitment then I wouldn't have done it because, frankly, it wasn't much fun. Here's a quick summary of how it turned out:<br /><br />Day 1 - Gatwick to Dover/Dunkerque (85 miles cycling) - it wasn't too bad - a bit of drizzle, nice scenery and the cycling was not too tough. (We then got a ferry to Dunkerque - the staff at <a href="">Norfolk line ferries</a> were great, putting on a fantastic meal, and a tour of the bridge, specially for us).<br /><br / <span style="font-style: italic;">brutal</span>..<br /><br / "<a href="">Amstel Gold</a>" race), we cycled through a thunder storm - we had hail, torrential rain (consequently very bad visibility), thunderbolts and lightning (very very frightening).<br /><br />Copyright © 2009 Ivan MooreIvan Moore, I won't be going to <a href="">XP 2009</a> - I'm sure it'll be great - enjoy it if you're going.<br /><br />While training for the <a href="">London to Aachen bike ride</a> (<a href="">sponsor me</a>) I regularly cycle past a couple of signs that somehow make me think of the XP conferences:<br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href=""><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 240px; height: 320px;" src="" alt="Welcome to Kent" id="BLOGGER_PHOTO_ID_5336786314264081810" border="0" /></a><br /><br /><a onblur="try {parent.deselectBloggerImageGracefully();} catch(e) {}" href=""><img style="margin: 0px auto 10px; display: block; text-align: center; cursor: pointer; width: 320px; height: 240px;" src="" alt="Beck Way" id="BLOGGER_PHOTO_ID_5336786452625790850" border="0" /></a><br /><br />Copyright © 2009 Ivan MooreIvan Moore management lessonsI signed up for the <a href="">National Autistic Society's</a> <a href="">London to Aachen bike ride</a>. When I signed up it was 3 days, with the longest day being the second at about 100 miles (it was noted that this event hadn't been run before so the itinerary might not be 100% accurate).<br /><br />A few weeks later, I got an update on the itinerary - I was told that the organizer had done a recce (reconnaissance) of the route and the second day would now be 120 miles (last day longer too but not too bad).<br /><br /.<br /><br />Therefore, of course, you should <a href="">sponsor me</a>. Also it gives me a good example of the sort of thing that happens with software projects very frequently; so here are some relevant lessons using this as an example.<br /><br /><span style="font-size:130%;"><span style="font-weight: bold;">How to handle estimation</span></span><br /><br />Most people are rubbish at estimating - not only software developers about code, but lots of people about lots of other things too. The three most obvious reactions to that are (a) get better at estimating (b) take bad estimating into account (c) <a href="">don't estimate</a> (or at least, not quite like most people do). I have found "extreme planning" (see <a href="">Planning Extreme Programming</a> and <a href="">Agile Estimating and Planning</a>) to work very well - however it is only really relevant to an incremental project. Quite literally, YMMV!<br /><br /).<br /><br /><span style="font-size:130%;"><span style="font-weight: bold;">Admit when you have screwed up and don't know the answers</span></span><br /><br />The first change to the itinerary was not entirely unexpected - I knew the route hadn't been done before - my expectations had been set that this was an estimate.<br /><br /.<br /><span style="font-size:130%;"><br /><span style="font-weight: bold;">Mitigating risk</span></span><br /><br /!).<br /><br /><span style="font-size:130%;"><span style="font-weight: bold;">Some things you just can't predict - but maybe everything will work out OK anyway</span></span><br /><br />Unfortunately, my bike has developed a fault with the gears which may make it financially non-viable to repair so I may have to get a new bike - but given the new increased mileage that may be worthwhile even if my current bike can be fixed.<br /><br />I'm disappointed that the event doesn't appear as well prepared as the <a href="">London to Paris bike ride</a> that I did in 2007 and that I haven't raised as much money (yet) as in 2007, but <a href="">you can help with that</a>!<br /><br />Copyright © 2009 Ivan MooreIvan Moore | http://puttingtheteaintoteam.blogspot.com/feeds/posts/default | CC-MAIN-2017-43 | refinedweb | 8,670 | 51.78 |
Let's look at bulk content creation. We're going to use a DOS Batch file to quickly generate multiple SWFs containing different text, sound, images etc. but which follow a template defined by us.
I must admit, I am a SWF lover. You hear a lot these days about HTML5 and other emerging technologies that will somehow put the good old SWF out of business, but I will be one of those developers clinging to my beloved SWF for as long as I can. Over the past 14 years or so, the SWF has been unique in its ability to deliver rich media content over the web, way before any other technologies could come even close.
For elearning, the SWF is still pretty much the standard, and is something I use throughout all of my lesson content. I use it for everything from virtual tutor videos to vector images, vector text, and interactive activities of all kinds.
For doing bulk content creation, I've found that nothing works quite as quickly and powerfully as a good DOS Batch file. You can quickly write and modify a batch file to do all kinds of interesting things, and if you are working with a large amount of images, text, and audio, a batch file can quickly turn that into multimedia content in the form of a SWF.
Reasons you may like to do this include:
- You don't have Flash installed on the PC where you are working
- You want to create SWFs in bulk
- You want to create SWFs from the command line
The only tool in Windows that you need other than your code editor is the Flex SDK, and optionally an open source ASCII to UTF-8 converting application called iconv from the GnuWin project, if you plan to use international characters or accent marks in your text.
Final Result Preview
Let's take a look at the final result we will be working towards
Step 1: Determine Your SWF Type
Bulk creation means that all of your SWFs will follow the same template, so decide what kind of items you have a need for: vector text, image, audio, etc.
Step 2: Organize Assets and Fonts
Name your files appropriately: each text, image, and audio file should have matching names, as well as case. If your files are disorganized, you may want to download a file utility program to batch rename them, convert to lowercase, etc. One such program I found is called Useful File Utilities.
You may want to open a text file and keep a list of absolute paths to these items, including any fonts you plan to embed.
In the source/utility folder of your download for this tutorial, you'll find some small batch scripts that can help you create a master wordlist to use with your SWF creation. If your file names contain more than one word, please use a dash between words [-]. Dashes are already accommodated for in my main .bat file which creates the SWFs. When using dashes, they are converted to numbers and later converted back to dashes with another small utility file, as otherwise your AS3 class files will fail to compile.
Step 3: Create AS3 Class File Template
Open up your code editor (I always use Notepad++ for multi language coding, it's an amazing open source application).
In the following steps, I will sketch out possible elements for you to add to your class file definition, which will be used by your DOS file to generate all of your SWFs.
If you'd like to follow along by examining the class file I used for these snippets, open the source/lago.as file in your download package for this tutorial.
We begin by adding a generic package layout in AS3, which without any functions would look something like this:
package { import flash.display.Sprite; import flash.display.*; public class lago extends Sprite { } }
Now let's add some actual items to our SWF!
Step 4: Embedding an MP3
As always, you begin by importing the necessary class files:
import flash.media.Sound; import flash.media.SoundChannel;
Here is code to embed a sound at a static location. You'll notice when we come to create our DOS file, we use the variables for our folder and file name instead.
[Embed(source="C:/Users/You/Desktop/sound/lago.mp3")] public var soundClass:Class; var sndChannel:SoundChannel; var smallSound:Sound = new soundClass() as Sound;
Step 5: Embedding an Image
Here is code to embed an image:
[Embed(source="C:/Users/You/Desktop/images/lago.swf")] public var Picture:Class; var pic:Sprite = new Picture();
In my file I first create a Sprite, which I add the image to, but if you want to add the picture directly to the stage you would just use:
addChild(pic);
Step 6: Embedding a Font
As I am using international characters, I embed my font by specifying which Unicode characters to include:
[Embed(mimeType="application/x-font", unicodeRange='U+0061-U+007A,U+00E1-U+00E1,U+00E9-U+00E9,U+00ED-U+00ED,U+00F1-U+00F1,U+003F-U+003F,U+00FA-U+00FA,U+00E1-U+00E1,U+00F3-U+00F3,U+00BF-U+00BF,U+00A1-U+00A1', source="C:/Users/You/Desktop/BradBunR.ttf",fontName="Brady")] private var terminatorFontClass:Class;
To see which characters you need, you can check this chart here, found at the University of Wisconsin-Madison's Space, Science, and Engineering Website. In Windows, you can also open up your charmap.exe program and look at the values for the characters you need.
Step 7: Using
textFormat to Style Your Text
Begin by importing the necessary classes:
import flash.text.*; import flash.text.TextFormat; import flash.text.AntiAliasType;
Now create a
textField and attach a
textFormat to it:
var __text_tf:TextField = new TextField(),__format:TextFormat = new TextFormat();
Now let's apply some styling to our text. I used a size for the text below, but in my actual file I adjust the size based on string length, so this size line would not be used.
__format.size = 30; __format.font="Brady"; __format.letterSpacing=6; __format.align = TextFormatAlign.CENTER; __text_tf.width=500; __text_tf.embedFonts = true; __text_tf.wordWrap = true; __text_tf.defaultTextFormat = __format; __text_tf.autoSize="center"; __text_tf.text = str;
Step 8: Changing Font Size According to String Length
This was a bit of a tricky piece of code, but if you are trying to create bulk SWFs of phrases and even sentences rather than just single words, you'll find that it's necessary to accommodate for different string lengths. Otherwise some of your words will be either too big, or too small.
if (str.length <= 9) { __format.size = 70; } else if (str.length >= 14 && str.length <= 22) { __format.size = 50; __text_tf.defaultTextFormat = __format; } else if (str.length >= 28 && str.length <= 48) { __format.size = 40; __text_tf.defaultTextFormat = __format; } else { __format.size = 50; }
Of course you can change these values according to your own content needs.
Step 9: Centering Text in a
textField
This line eluded me at first, and was crucial for getting my text to center properly in the
textField.
__text_tf.autoSize="center";
Step 10: Centering and Proportionately Resizing an Image
This code took the better part of a day to get right, and is the only way I found to properly resize and center a SWF. You can change the x, y,
targetHeight, and
targetWidth values depending on the size of your own SWFs, but otherwise this code can help you achieve centering and resizing:
var ratio:Number; var wide:Number; var targetWidth:Number = 400; var targetHeight:Number = 250; if (pic.width < targetWidth) { ratio = targetWidth / pic.width; pic.width = targetWidth; pic.height *= ratio; wide = pic.width*ratio; } if (pic.height < targetHeight) { ratio = targetHeight / pic.height; pic.width *= ratio; pic.height = targetHeight; wide = pic.width*ratio; } if (pic.width > targetWidth) { ratio = targetWidth / pic.width; pic.width *= ratio; pic.height *= ratio; wide = pic.width*ratio; } if (pic.height > targetHeight) { ratio = targetHeight / pic.height; pic.width *= ratio; pic.height *= ratio; wide = pic.width*ratio; } pic.y = 110; pic.x = 250 - wide/2 ; pic.scaleX = pic.scaleY; square.addChild(pic);
}
Step 11: DOS Version of Your AS3 Class File
Please take a look at the sample file source/lago.as if you need more help crafting your class file template, as now it's time to create the DOS version of your file.
Open up the lago.bat.txt file in your download's source directory, and save the name to just lago.bat. If you are using a code editor such as Notepad++, you should have a Batch highlighting syntax which will now be applied. While not necessary, syntax highlighting does make Batch coding a lot easier.
Remember that DOS needs you to escape certain characters by prefixing them with a caret [^] (or sometimes a double-caret [^^], including:
- (
- )
- >
-
- &
Also, remember the following things:
- Each line must begin with
echoso that it will be included
- Each line must end with
>> !fileoutta!so that it will be appended to our SWF creator .bat file
Use a program like Notepad++ to run a RegEx search and replace, first escaping the necessary characters, then adding the
echo commands at the beginning of lines, or where \n is found, and adding the
>> !fileoutta! before returns, or where \r is found. For example:
Find:
\n
Replace with:
\n
echo
And
Find:
\r
Replace with:
>> !fileoutta!\r
Finally save this DOS version of your file, i.e. myclass.bat.
Step 12: Begin Crafting Your DOS Batch File
To better follow along, open up the following file from your download's source directory: batch_create_swfs_word_picture_w_audio.bat.txt. Change the file ending to just .bat and save.
Points about this .bat file:
- It will run in the folder where you place it
- It will use the folder name as a variable
- It will expect any images to be in an /images subdirectory
- It will expect any audio files to be in a /sound subdirectory
- The absolute paths to the Flex compiler, any fonts you want to embed, and optionally the iconv.exe program are needed
I use a master word list file to create my SWFs, which is found in source/glossary/glossary.txt. To create such a file from a folder of files, you can use one of my utility .bat files found in the source/utility folder.
Keep in mind that batch processing requires you to be very conscientious when naming any assets. The best approach is to give any image and audio assets intended for the same SWF the exact same name, then put them in the correct subfolders -- for example:
sound/lago.mp3
images/lago.swf
The glossary/glossary.txt file to create only the SWF for lago would simply read
lago
The beauty of my system is that my glossary.txt file can contain an unlimited amount of words - in fact I've run it with 1000+ words, with no problems at all! But the assets you are attempting to embed must exist, and be in the correct location, named correctly, or the SWF for that word will fail to compile.
Step 13: Replace Your File and Directory References
Look again at the batch_create_swfs_word_picture_w_audio.bat file. Scroll down to the section below the REM 1 title, and you'll find the beginning of the area where you can add the DOS version of the custom AS3 class file you created in Step 11.
One thing to note is that I use the variable
!myvar! for the folder name, so that I can drop this .bat file into any folder within a main directory on my computer, and the paths to the files will still be correct as long as I use the /images and /sound subdirectories. Examine my code before pasting your own in, so that you can make the proper replacements.
The sections titled REM 1, REM 2, REM 3, and REM 4 all require you to customize based on your own folder paths.
Step 14: Optional Customize iconv UTF-8 Converter Path
Open up the utf_convert.bat.txt file and rename it to utf_convert.bat. Find the REM 1 and REM 2 sections, and fill in the correct paths for your files.
Step 15: Organize Your Files for a Trial Run
Time to get compiling! Find the master directory you've used for all your paths, and create a new folder called trialrun. Open up the download folder for this tutorial, and copy the subfolders from source/trialrun and paste them into the trialrun folder you just created in your master directory.
Step 16: Copy and Paste .bat Files
Copy batch_create_swfs_word_picture_w_audio.bat and optionally the utf_convert.bat files to the trialrun directory you just created.
Step 17: Click on the Main .bat File
Time to give batch SWF creation a try! Click on batch_create_swfs_word_picture_w_audio.bat This will create the AS3 class files that will be used to generate individual SWFs.
Step 18: Click on the UTF-8 Creation .bat Files
You'll be given instructions in the Command Line Console to click on the utf_convert.bat and the utf_click_to_convert.bat files, in that order. This will convert all of your AS3 class files to UTF-8 compatible files before running the Flex AS3 compiler.
Step 19: Continue Batch Creation by Clicking Any Key
After the UTF-8 conversion is done, the Command Line Console will wait for you to click any key, before resuming. Once you do that, the actual SWF compiling will begin. For the trial operation, 3 SWF files will be created in the trialrun/word_scripts_sp_au_utf8 directory.
Step 20: Check Your SWFs
Open up the trialrun/word_scripts_sp_au_utf8 directory and see if your SWF files are there. Alongside the .as class files, you should see: lago.swf, nieve.swf, and hielo.swf.
When you run your own wordlists for batch SWF creation, you may have long filenames that need to be renamed in batch. As you cannot have dashes in your AS3 class names, I use numbers to replace them when necessary, then I run a small utility .bat found in utility/rename_long_swfs.bat.txt of your download folder. Rename the extension of this file to .bat, then copy it into the word_scripts_sp_au_utf8 folder where your finished SWFs reside in order to do this renaming on a group of SWFs.
Conclusion
I hope this tutorial will help some of you to enjoy the wonders and true programming bliss that can come with SWF batch creation through DOS. To see hundreds of perfect multimedia SWFs created with just a few clicks is quite a great feeling! Thanks very much for giving this tutorial a read, and I look forward to any comments or questions that you may have.
Note: It's worth noting that ANT is often considered a worthy alternative for batch file creation, particularly for Mac users. Check out Jesse Freeman's Introduction to AntPile to find out more.
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UFDC Home myUFDC Home | Help | RSS Group Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings Title: P2.73 - Two-fluid model for 1D simulations of water hammer induced by condensation of hot vapor on the horizontally stratified flow ALL VOLUMES CITATION THUMBNAILS PAGE IMAGE ZOOMABLE Full Citation STANDARD VIEW MARC VIEW Permanent Link: Material Information Title: P2.73 - Two-fluid model for 1D simulations of water hammer induced by condensation of hot vapor on the horizontally stratified flow Multiphase Flows with Heat and Mass Transfer Series Title: 7th International Conference on Multiphase Flow - ICMF 2010 Proceedings Physical Description: Conference Papers Creator: Tiselj, I.Martin, C.S. Publisher: International Conference on Multiphase Flow (ICMF) Publication Date: June 4, 2010 Subjects Subject: condensation induced water hammer1D two-fluid model Notes -22oC and -48oC and hot vapor temperatures around 15oC.506 Source Institution: University of Florida Holding Location: University of Florida Rights Management: All rights reserved by the source institution and holding location. Resource Identifier: P273-Tiselj-ICMF2010.pdf Full Text 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 Two-fluid model for 1D simulations of water hammer induced by condensation of hot vapor on the horizontally stratified flow I. Tiselj* and C. Samuel Martin** Reactor Engineering Division, Jo2ef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia iztok.tiselj@ijs.si **School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA csammartin@ comcast.net Keywords: condensation induced water hammer, 1D two-fluid model -220C and -480C and hot vapor temperatures around 150C.. Introduction Condensation-induced water hammer research at Jo2ef Stefan Institute has been performed as a part of the EU research project NURESIM (NUclear REactor SImulations) and is being continued within the currently running EU project NURISP (NUclear Reactor Simulation Platform). Research is related to the simulations of stratified flows in horizontal pipes. Main attention within NURESIM project was paid to the CIWH scenario, where cold liquid was slowly flooding a horizontal pipe filled with hot steam (Strubelj et. al., 2010). Another type of CIWH scenario assumes injection of hot steam into horizontal pipe partially filled with cold liquid: this scenario is the main topic of JSI research within NURISP project. 1) First type of CIWH can appear when the pipe filed with hot steam is slowly flooded with cold water. This type of the CIWH was shown to be a stochastic and thus very unpredictable phenomena (Bjorge and Griffith, 1984, Strubelj et. al., 2010). Models used to simulate Type 1 of the CIWH were 1D two-fluid models and various 3D codes also based on two-fluid models. Calculated results were compared to experimental data from Hungarian KFKI-PMK2 device. It was shown that neither 1D model nor 3D CFD model could accurately predict where and when the slug will form, or if the slug will form at all. 2) Second type of CIWH can appear when hot steam enters a pipe that is partially filled with cold liquid. The most unstable part of the interface is always near the steam inlet into the pipe, thus, it is more or less known where the slug will be born. Experimental results for this type of the CIWH were obtained by C.S. Martin (Georgia Tech, 2007). Since the position of the slug formation is known, this type of CIWH is less stochastic and more predictable than the type I Paper No 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 of the CIWH. In the present paper computer code WAHA is used as a platform for 1D simulations. The code is solving 6 equation 1D two-fluid model. WAHA code is using a special type of numerical scheme that aims particularly at the fast transients (like CIWH). Models that require verification and validation are criteria that trigger transition from horizontally stratified into slug regime of two-phase flow. These models are required in 1D two-fluid models where horizontally stratified flows are described with different set of correlations than dispersed flows. The existing WAHA code physical models were upgraded with correlations for steam condensation on the cold walls of the horizontal pipes. Inter-phase heat, mass and momentum exchange models in horizontally stratified flows are already available in WAHA. However these models require fine tuning for accurate description of the CIWH with vapor injection. Nomenclature pipe c pipe c pipe c interfa matrix matrix ross-section [m2] ross-section change due to elasticity [m2] ross-section covered by phase k [m2] cial area concentration - temporal derivatives - spatial derivatives A Ae Ak agf A B C, CD Cvm CVMI D d do E e Ffwall Fk fk g Htk hk* kk Nuk P P. Re Qk S SR Tk t Uk v Verit Vr X Xsat x Greek l a vapor volume fraction [m3/m3] Cld~p ahV modified vapor volume fraction [m3/m3] modified vapor volume fraction [m3/m3] vector independent variables p density [kg/m3] Tg 0 0 Subsripts f li vapor source term [kg/(s m )] inclination of the pipe relaxation time quid g vapor k liquid or vapor m mixture s saturation i interface Experimental Facility An apparatus was designed by Martin et.al. (2007) to simulate an industrial environment whereby ammonia liquid is standing in a partially-filled horizontal pipe in thermal equilibrium with ammonia gas above it. The essential elements of the test setup consist of a horizontal pipe and a high pressure tank containing hot ammonia gas as shown in Fig. 1. The test pipe was a nominal 150 mm diameter, 6 m long schedule 80 carbon steel pipe, having internal diameter of 146.3 mm, and wall thickness 11 mm. The pressure tank contained ammonia gas on top of liquid in thermal equilibrium at ambient conditions inasmuch as the entire test facility was outdoors. Between the pressure tank and test pipe were three valves angle valve, solenoid valve, and throttle valve -- and a metering orifice. The angle valve remained fully open, while flow was initiated by a solenoid valve for a given position of the throttle valve. The flow of hot gas was controlled by manually positioning the throttle valve for the existing ambient hot gas pressure. The ammonia in the insulated test pipe was introduced from an ancillary system containing a compressor, an auxiliary tank, and another tank for purging non-condensible gases. For each test, care was exercised to transfer ammonia liquid to or from the test pipe to establish the desired depth and equilibrium temperature. The principal measurements were (1) receiver gas pressure (ambient temperature), (2) orifice-metered gas flow (up to 0.45 kg/s), (3) static temperature and pressure of saturated liquid and gas in test section (225-250 K, -0.45-1.6 bar), (4) dynamic gas pressures and shock pressures in test section that reached up to 50 bar. Fig. 2 shows schematic description of the condensation-induced water hammer phenomena. Top of the Fig. 2 shows initial conditions in the system cooled to 225-250 K. Initial depth of the liquid and initial temperature and corresponding saturation pressure were modified in different experimental runs. When the valve on the hot gas inlet pipe is opened, hot gas enters the test section and can induce slugging if the relative velocity between phases is high enough. Gas velocity above the liquid interface depends on inlet mass flow rate and on the condensation rate of the gas on the cold walls of the pipe and cold surface of the liquid. Once the slug is formed, very efficient heat transfer at the head of the slug causes pressure difference between the tail and the head of the slug and pushes the slug towards the closed end. During the slug propagation the mass of the liquid inside the slug grows and the water hammer pressure Paper No inter-phase drag coefficient [kg/m4] dimensionless interfacial friction coefficient virtual mass coefficient [kg/m3] virtual mass term [N/m3] pipe diameter [m] pipe wall thickness [m] average droplet diameter [m] pipe elasticity modulus of the material [N/m2] specific total energy [J/kg] wall friction forces [N/m3] drag force on phase k [N/m3] dimensionless friction factor gravity [m/s2] volumetric heat transfer coefficient [W/(m3 K)] specific internal enthalpy [J/kg] thermal conductivity [W/(m K)) Nusselt number pressure [Pa] interfacial pressure [Pa] Reynolds number volumetric heat flux to phase k [W/m3] stratification factor source term vector non-relaxation source term vector relaxation source term vector temperature [K] time [s] specific internal energy of phase k [J/kg] velocity [m/s] critical velocity [m/s] relative velocity [m/s] vapor quality vapor quality at saturation spatial coordinate [m] letters 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 surge is registered when the slug hits the closed pipe end. TRANSDUCERS Static Pressure: PT(Gage); Pl; P2; PACE1; PACE2; PACE3; PACE4; PACE5 Dynamic Pressure: PCB1; PCB2; PCB3; PCB4 Static Temperature: RTD1; RTD2; RTD3; RTD4; RTD5 Dynamic Temperature: Thermocouples TC1; TC2; TC3; TC4; TC5 Fig. 1: Schematic of test pipe, orifice and pressure tank I hot steam inlet closed end slug head Fig. 2: Typical transient: red hot gas, blue cold liquid, top - initial state, bottom slug. Two-Phase Flow Model Of The WAHA Code Mathematical model of the WAHA code is ID six-equation two-fluid model similar to the models of RELAP5 (Carlson et al, 1990) or CATHARE (Bestion, 1990) computer codes. The basic equations are mass, momentum and energy balances for vapor and liquid, with terms for pipe elasticity and without terms for wall-to-fluid heat transfer. Continuity equations for liquid and vapor (gas) phase are: (1-a) + -p, ap +( I(1-a) p,v, 8a(t i-a) p + x 8t 8t 8x OA(1-a) p v St 8A(1-a)p pv/ ap +A(1-a)-- 8 x 8x aa A*CVM Ap, =AC, v, v, 8x -AF v, +A(1-a)p, gcos0 -AF, SAa pv, Aa pggv +Aap + at 8x ax aa +A* CVM+Ap,- =-AC, Iv,v, + ax +AFgv, +Aap,gcosO-AFg,, Internal energy balance equations for both phases are: u 8 u f uf 9a p ot ox 8t 8t +(1 a) s--t I a) Pf Vx p-+p(l -)K + a(l-a)vf ap +P- +p(l-a)vfK K= 8x 8x 1 dA(x) Qf -r,(u -u)+v,F,w-(1 -a)vpA d(x A(x) dx 8ug 8ug 8a 8p aavg a P a --+ap v--+p--+paK +p- a+ S8t 8x 8t 8t 8x +pavgK d= dA(x) g g g g+vF,^ -avp dx A(x) dx +(1-a) pfvK f ax 1 dA(x) -Fg -(1-a) Pv Ax) dx A(x) dx (1) Specific total energy of liquid or gas is: aapg a p +aapgvg ap --ps +ap K +--p-v+ap, v,K 1P at a 8t 8x x sx g 1 dA(x) S A(x) dx (2) where the temporal changes of cross-section A(x,t) are neglected in the denominators of the last term of equations (1) and (2) (and also in Eqs. (5) and (6)). Momentum balance equations for both phases are: e=u+v2/2 (7) Differential terms are collected on the left-hand side of the equations and the non-differential terms are collected on the right-hand side. Terms that include constant K in Eqs. from (1) to (6) are due to the elasticity of the pipe walls. According to Wylie and Streeter (1978), speed c of a small pressure wave in 1D elastic pipe filled with single-phase fluid should be reduced. The following modification is thus introduced. Pipe Paper No Solenoid HEV Angle Volve Paper No cross-section A(x,t) can vary along the coordinate function of initial pipe geometry A(x) and due to the change A,(p(x,t)). A(x,t) = A(x) + A (p(x,t)) The pressure pulse changes the pipe cross-sec accordance with linear relation: dAe D dp =K-dp A(x,t) d E where D is diameter, d is thickness and E is Young's n of the elasticity of the pipe. Closure relations The WAHA code uses several different; non-differential closure relations. Closure relati two-phase flow are used to describe interfacial hea and momentum transfer, wall friction, interfacial p virtual mass term, equations of state etc. The equa state for each phase k, where k is f for fluid and g fo are: dp,-(a P d =- -- aP d, Derivatives on the right-hand side of the Eq. ( determined by the ammonia property subroutines de for the WAHA code using pressure and tempera specific internal energy as input. Ammonia propel pre-tabulated with subroutines developed on the I IAPWS recommendations (Bukes, Dooley, 2001), an at approximately 300 pressures (0 bar 2500 bar) temperatures (195.5 K 1714 K). The virtual mass term CVM in Eqs. (3) and (4) is obtain hyperbolicity of the system: av, t ax at gv Value of the coefficient Cv, was tuned to ens hyperbolicity of the two-fluid model equations. virtual mass term does not ensure uncon hyperbolicity of the equations. For very large velocities (comparable to sonic velocity) c eigenvalues may appear, however these velocities relevant in realistic two-phase flows. In dispersed flow it is assumed that the pressure phases is the same. The water surface in hori stratified flow can be wavy, therefore the interfacial termp, is applied to describe pressure gradients: x as a pressure (8) tion in 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 interface heat transfer terms (Q,, Q,). Terms due to the variable pipe cross-section. Terms with wall friction (Ffwai, Fg,wai). Term with volumetric forces (g cosO). Sources from the points 1. and 2. are the so-called relaxation source terms. They play crucial role in the case of condensation-induced water hammer and therefore their detailed description is given in the next section. Other, non-relaxation source terms are terms with wall friction and volumetric forces. (9) Relaxation source terms Relaxation source terms are inter-phase mass, momentum, nodulus and energy exchange terms, which tend to establish thermal and mechanical equilibrium between the phases. Characteristic time scale of relaxation source terms can be much shorter than the characteristic time scale of the acoustic al and waves (terms are stiff and need special numerical treatment). ons in Relaxation source terms are flow regime dependent. it, mass Avery crude flow regime map (described below) has been pressure, applied in the WAHA code, which is actually nothing more tions of than search for the best fit of the macroscopic data, and is ir steam open for improvement with the further comparison with the experimental data. More detailed flow regime maps were abandoned as they are developed for the steady-state flow regimes. The accuracy of the existing more detailed flow (10) regime maps in the area of fast transients comparing to our crude flow regime map, is in our opinion not significantly 10) are higher, and does not justify their use in the WAHA code. The veloped main goal of the WAHA correlations is to have correct iture or correlations in the limit of high and low vapor volume ties are fractions with their smooth transition into the single-phase basis of flow, with possibility of their further tuning on the basis of d saved the experiments. It is important to note that even the and 350 "standard" single-phase wall friction correlations (RELAP, CATHARE) turn out to be insufficient in the area of the fast used to transients. The WAHA code offers an option of the "unsteady wall friction model" that takes into account additional wall friction due to the unsteadiness of the flow. 9 The WAHA code distinguishes two flow regimes (Fig. 3): ) 1 dispersed flow with stratification factor S= 0 and horizontally 11 stratified flow with S=1. There is also transition area between both regimes with 0 ure the divided into bubbly flow (a< 0.5), droplet flow (a > 0.95) and Applied transitional bubbly-to-droplet flow. utiuInal relative complexx are not of both zontally pressure p, = Sa(1 a)(pf p,)gD (12) where S presents the stratification factor. Terms that don't include derivatives are source terms and they are flow regime dependent. Source terms in Eqs. (1)-(6) are: Terms with inter-phase drag (C,). Terms with inter-phase exchange of mass and energy: vapor generation rate (Fg), Dispersed flow Horizontally stratified Transitional area S= Transitional area flow ow 1 > S > > 0 95 Droplet flow S = 1 0 95 > a > 05 Transitional flow a< 0 5 Bubbly flow 0.5 Vcnt Vent 0 Vr Fig. 3: WAHA flow regime map. Flow is dispersed with S= 0 if at relative velocity v, is larger than the critical velocity: l"vr "c rt J ia (1-a)1 vcrit= gD(pf pg) + S gP 9 ) (13) This expression is an approximation based on the Kelvin-Helmholtz instability. This critical velocity is at the 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 same time maximum relative velocity, where two-fluid model with applied interfacial pressure term and without virtual mass term, is still hyperbolic. Flow is horizontally stratified with stratification factor S = for vr < vcr,,rc/2 . Flow is transitional between dispersed and horizontally stratified, if v ..I ,/2< Ivv, Stratification factor S is linearly interpolated between 0 and 1 in such case. This approach is similar to the well-known Taitel-Dukler correlation for transition from stratified to slug flow (Taitel, Dukler 1976). From the standpoint of condensation-induced water hammer modelling, this model represents a possible area of the future work, however it was not changed in the present study. The most important set of correlations for the present research are stratified flow correlations that are crucial for accurate description of the initial phase of the transient including the formation of the slug. Slug formation means transition in different flow regime that requires different set of correlations. Despite the fact that this work considers modelling of 1D slug flow with two-fluid models, existing slug flow correlations (see Lin, Hanratty 1986, or Issa, Kempf, 2003 for example) are not directly applicable as they give an averaged heat, mass and momentum transfer correlations instead of instantaneous local values needed for the present study. A single slug is being explicitly followed in the present study with 1D two-fluid model. Such tasks are expected to be performed with multidimensional CFD analysis using some of the free surface tracking algorithms and not in 1D two-fluid models. However, while the current CFD codes might be able to describe the stratified flow with condensation and also slug formation and development, one can certainly expected problems with modelling of the thin condensate film on the walls and water hammer shock waves followed by the flashing of the liquid. And while we do intend to test CFD models for condensation-induced water hammer in the future, our present goal represents development of the suitable 1D two-fluid model. Inter-phase momentum transfer The interfacial friction coefficient C, in momentum equations is calculated from correlations, which are valid for two-phase flow water-vapor and for two-component flow water-ideal gas (similar to RELAP5 model). The original WAHA correlations remain unchanged for the present simulations and analyses have shown rather low sensitivity of the results to the inter-phase friction coefficients in stratified, dispersed and transitional flow. Horizontally stratified flow interfacial friction coefficient is calculated from the equation, which states that magnitude of the drag force of the gas on the liquid is equal to the drag force of the liquid on gas: F,= F = C, (v -v ) (14) interfacial friction coefficient is then calculated as: 1 (, v)2 ( Pf, V)2 k =g,f the vapor volume fraction a: 1. a < 0.5 (Bubbly flow): C, pCaf 8 with drag coefficient of the slug: C = 24(1 + 0.1Re 75)/Re and interfacial area concentration: ad = 3.6ab,, /do where abb is modified vapor volume fraction, do is average slug diameter and Re is Reynolds number. 2. a > 0.95 (Droplet flow): C, =maxlp,gCag, 0. 1 (19) (8 with the drag coefficient of the droplet: C, =min(24(l+0.1Re 75)/Re, 0.5) and the interfacial area concentration: ag. = 3 .'I.,i. 10 4)/d0 where adp is modified liquid volume fraction and do is average droplet diameter. 3. 0.5 inter-phase friction coefficient is calculated with interpolation: =(c- bubbly" (c droplet)( q) (22) with exponent q: ( 0.95-a q 0.95-0.5) that was chosen to ensure smooth transition between correlations in Eq. (16). and Eq. (19). Dispersed-to-horizontally stratified interfacial friction coefficient is calculated with interpolation: C, =S(C,sied) + (1-S)(Cdpe) (24) Inter-phase heat and mass transfer Calculation of inter-phase heat and mass transfer were significantly modified for the present condensation-induced water hammer research. Original WAHA correlations do not take into account wall heat transfer, which is an important mechanism for the present work. are valid only for water-vapor two-phase flow. The "standard" inter-phase mass transfer (vapor generation rate F ) is calculated as: where fk are friction factors, v, is interface velocity and a g is interfacial area. Dispersed flow coefficients are further divided according F -f + ,g g h -hf 9 f where hk are specific enthalpies and Q,k are Paper No Paper No liquid-to-interface and gas-to-interface heat fluxes. The volumetric heat fluxes are calculated as: Q,, = H,,(T -T, ) k fg The heat transfer coefficients Hk depend on flow regime. Beside the interphase heat and mass transfer, condensation on the wall is taken into account as: 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 if slug head identified: H,f = -Ca(1- a) Va f(T, Tg) v, c3 else H, -0 enf = endif IfT Tf T I C4 f(Tf,ITg)= f T- "4 Tgr iS Fg wal H,g-wao (Twall- T,) F g wall : * h* -h 9 T ;T > T using Chato-Dobson correlation (Dobson, Chato, 1998) for condensation rate in the horizontal pipe: Nu = NU +( -(l f /rT)Nfod = 0.23Re'o2 Ga Pr 025 1+1.11x28 Ja +(1- ,/;7T)0.0195Re8 Pr4qI4 fA(X,) 4k H,g wall = Nulm D4 - 4k (28) 4k H, =(1 -O /,r),Nfo~Cd D2 The first term in Chato-Dobson correlation represents part of the coefficient, which represents contribution of the film condensation on the wall and the second term represents contribution of the forced-convective condensation on the liquid-gas interface. The following variables are used in Eq. (28): Rego Gas only Reynolds number, Ga Galilei number, Ja Jacob number, <(/Xd) function of turbulent-turbulent Lockhart-Martinelli parameter given in Dobson, Chato, 1998. Each term of Chato-Dobson correlation is used separately: film condensation term in Eq. (27) and forced-convection inter-phase exchange coefficient in Eq. (26). The vapor heat transfer coefficient H,g is calculated as (similar in the RELAP5 code): k H,g = a, g 0.023Re8 (29) D Dispersed flow heat transfer is actually not present during the transient the closest "approximation" of dispersed flow can be seen at the head of the slug, where wave breaking appears and causes much more efficient inter-facial heat transfer than predicted by Chato-Dobson correlation. This phenomena can be seen from the air-water experiments and simulations of Bartosiewitz (2008) and experiment of Vall6e et. al. (2010). Thus a very crude inter-phase heat and mass transfer is used at the location of the slug head: Values C1=1.5, C2=1, C3=0, C4=1, C5=1 were used in the calculations collected in the Table 1 below. Head of the slug is located with the gradient of the liquid superficial velocity: if V((1- a)vv) < -0.05, slug head identified (31) This is rather unusual approach for 1D two-fluid model and actually represents some kind of inter-phase tracking within the 1D two-fluid model. However, according to our experience, this is the best way to perform condensation-induced water hammer simulations with 1D two-fluid model. If the slug, and especially the head of the slug (where stratified heat and mass transfer correlations are not applicable) is not successfully recognized and condensation rate increased in that area, the simulations exhibit rather poor results. The vapor heat transfer coefficient H,g in dispersed flow is calculated similar in the RELAP5 code, with a single goal to almost instantaneously bring vapor to equilibrium: H = (1+ 7.(100+ 25. 7)), (32) where 77= max(-2,T, -7T) . Unlike the standard WAHA code where transition between horizontally stratified and dispersed flow (stratification factor 0 < S <1) inter-phase heat transfer coefficients are calculated with interpolation: Hk =S(Hk-stried) +(1-S)(Hk-diped) (33) the modified heat transfer coefficients are calculated as: H, = max(H,k-satfied Hk-dspersed) Inter-phase exchange correlations described with Eqs. (25)- (34) are applied in WAHA code with minor correction factors, that act at very low vapor or liquid volume fractions and prevent negative values or extremely large values of heat transfer coefficients. Numerical Method The system of six-equations model (Eqs. (1) written in vectorial form: - t &x (6)) can be where represents the non-conservative vector of the independent variables: vy = (p,a,f,vg,uf,u ) (36) Paper No further A and B are matrices of the system, and S is a vector with non-differential terms in the equations. Non-conservative schemes are known to converge to the wrong solutions when shocks are present in the flow field, however according to our experience (Tiselj, Petelin, 1997, Tiselj et. al., 2004), non-conservative scheme does not seem to be a big deficiency for short transients like water hammer events. The numerical scheme of the WAHA code is based on the two step operator splitting and characteristic upwind method; i.e. convection with non-relaxation source terms and relaxation sources in Eq. (35) are treated separately: A + B SN-R t -x A d -t Each step of the operator splitting is performed with second order accuracy. The applied operator splitting method is formally first-order accurate. However, the numerical tests showed, that despite the formally lower order of accuracy, the results are practically the same as with the second-order Strang operator splitting method. Results and Discussion Result of two simulations that were performed only with stratified flow correlations for heat and mass transfer in Figs. 4. and 5. show a reasonable agreement between the pressure measured in the experiments and simulation. First experiment shown in Fig. 4 is case 03.01.01-13 with strong pressure peak of 51 bar (see Table 1 for details of all experimental runs and main results of the simulations). The case 11.14.00-13 (Fig. 5) is experiment without recorded pressure peak. Result in Fig. 4 shows that Chato-Dobson correlation predicts reasonable condensation rate in the horizontal test section, which results in a reasonable pressure prediction. According to the calculations, slug is formed in both cases due to the sufficiently large relative velocity 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 between the phases. However, since only stratified flow correlations are used, the condensation rates ahead and behind the slug are more or less the same and the slug is not accelerated towards the closed end, but approaches the end very slowly. Experiment 11.14.00-13 (Fig. 5) shows rather smooth pressure growth, which means that liquid slug did not develop in that experiment and that slug predicted by the 1D two-fluid model does not exist. As is also shown later, the existing 1D two-fluid model is not very accurate for the experimental cases with small initial amount of the liquid. It should be noted that static pressure measurement shown in Fig. 4 does not include pressure peaks of the water hammer, only some pressure fluctuations right behind and after the pressure surge of the case 03.01.01-13 pressure are visible. It is interesting to note that in the case 03.01.01-13 pressure growth is stopped at time -1.4 s when the slug is formed and stronger condensation at the head of the slug starts. However, after the bubble behind the slug rapidly condenses and water hammer peak is over (-1.9 s), the condensation rate remains similar as in the Chato-Dobson based calculation. 2UUUUU 0 1 2 3 4 5 6 Fig. 4: Pressure (Pa) vs. time (s) at PACE3 static gas pressure sensor: measurement (dashed) and calculation (solid line) for test case 03.01.01.13. Table 1: Overview of the selected experimental cases and corresponding simulations. Times of pressure peaks are given with respect to the start of the gas injection. Times in Figures are given with respect to the starting time of the measurements. experiment initial initial initial approximate hot gas measured time of calculated time of pressure temperature vapor hot gas temperature pressure measured pressure calculated in the in the test volume mass flow (K) peak pressure peak (bar) pressure test section (K) fraction rate (kg/s) (bar) peak (s) peak (s) section (bar) 03.01.01-13 0.51 226.8 0.4736 0.31 293 51 0.58 56 0.58 03.01.01-14 0.55 228.6 0.4736 0.11 293 20 2.39 29 1.01 03.01.01-16 1.36 244.8 0.4736 0.32 295 27 0.63 17 0.92 05.21.01-12 0.45 224.8 0.4736 0.081 296 22 1.94 27 1.12 05.21.01-14 0.50 225.1 0.4736 0.15 296 44 0.81 43 0.83 11.13.00-31 0.52 227.8 0.4736 0.14 288 41 0.88 39 0.85 11.14.00-11 0.53 231.7 0.793 0.34 286 no shock / 47 0.76 11.14.00-12 0.57 232.1 0.793 0.42 287 25 0.98 48 0.66 11.14.00-13 0.65 233.9 0.883 0.43 287 no shock / 21 0.76 Paper No 350000 300000 250000 200000 150000 100000 50000 1-r---- ---- 0 05 1 15 2 25 3 35 4 45 5 Fig. 5: Pressure (Pa) vs. time (s) at PACE3 static gas pressure sensor: measurement (dashed) and calculation (solid line) for test case 11.14.00-13. Another effect is responsible for the differences in the condensation rate at later times seen in Figs. 4. and 5.: pipe wall, which is assumed to be at constant initial temperature in the simulations, is in fact slowly warming up, reducing the efficiency of the condensation. A conjugate heat transfer model could be added in the two-fluid model to avoid that effect, however, all the pressure peaks appear before the times when these differences become relevant. Similar agreement as seen in Fig. 4 and Fig. 5 exists for other test cases collected in Table 1 and calculated with only stratified flow heat and mass transfer correlations. Water hammer modelling An open issue remains upgrade of the two-fluid model with a procedure that can recognize the head of the slug, where inter-phase heat and mass transfer is much more efficient than predicted by the Chato-Dobson correlation. Slug head identification model from Eq. (31) was found to predict the area of the slug head. Increase of the heat transfer coefficients in the slug head region is performed with a general model of Eq. (30). These two models with the current values of the coefficients are being developed by fitting of the calculations with the measurements and remain open for further improvements. Capabilities of the current form of both models gives predictions of the condensation-induced water hammer pressure peaks with accuracy shown in the Table 1, where last 4 columns show measured and calculated magnitude and time of the pressure peak. Good agreement of pressure peak and timing is seen for cases 03.01.01-13, 05.21.01-14 and 11.13.00-31. Fig. 6 shows measured and calculated pressure for the case 03.01.01-13, which can be considered as a successful simulation. Secondary shock waves are seen in computation and experiment. They are caused by a classical "water column separation" mechanism, where WAHA code is well tested and accurate. As shown in Fig. 7 that presents the same case, pressure peak causes only minor changes in the integral condensation rate. Comparison of Fig. 7 and Fig. 4. shows very similar calculated pressure histories, despite the absence of the pressure peaks in Fig. 4. Case 03.01.01-14 performed with slightly lower hot gas mass flow rate and similar initial pressure and volume fraction than cases 05.21.01-14 and 11.13.00-31 gives much 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 earlier time of water hammer than measured. Surprisingly, comparing to the 03.01.01-14 slightly higher pressure peak at earlier time was measured in the case 05.21.01-12, despite even lower hot gas mass flow rate. This leads us to conclusion, that tuning of the models cannot be performed on one single experimental case due to the rather stochastic nature of the whole phenomena. Thus, all the changes in the models are continuously tested for all 9 test cases of the Table 1. Figs. 8 an 9 show an example of a simulation of modest accuracy 05.21.01-12. '11 14 00-testl 1strat out' u 1 5 /' FEB/EXPERIMENT/11 14 00/pace-pcb4-t11 exp u 1 4 / Fig. 6: Measured (dashed) and calculated (solid) pressure (Pa) vs. time (s) at the closed end for test 03.01.01-13. 500000 1 15 2 25 3 35 4 45 5 Fig. 7: Measured and calculated pressure(Pa) vs. time (s) in the middle of the pipe (PACE3) for test 03.01.01-13. The case 03.01.01-16 was performed at higher initial temperature than other tests. Similar pressure peak is measured and calculated, however, calculated pressure peak occurs too late. The worse results are obtained for high initial vapor volume fractions. An example of poor simulation is given in Figs. 10. and 11. for the case 11.14.00-11. Despite low amount of liquid, 1D two-fluid model predicts formation of the slug in all 3 cases 11.14.00-11, 12, 13. Slug formation is followed by a strong water hammer, which is not seen in the measurements at all, except a pressure peak of medium magnitude in the case 11.14.00-12. As seen in Fig. 5 the problem might not stem from the inter-phase heat and mass transfer correlations but from the basic two-fluid equations 5e+06 4e+06 3e+06 2e+06 le+06 '03 01 01-test3 out' u 1 2 / /FEB/ XPERIMENT/03 01 01/pace-pcb4-tl3dp exp' u 1 5 ----- 1v Paper No and their capabilities to model stratified flows. Non-existing slug in the case of Fig. 5 simulation is predicted even with correlations for stratified flow. Pressure interface term that makes the two-fluid model to behave like a shallow water equations when stratification is assumed, is more accurate at vapor volume fractions around 0.5, where circular pipe behaves like a rectangular channel. At low (less than 0.2) or high (higher than 0.8) vapor volume fractions the pressure interface term might have a different form, which would influence the dynamics of the large interfacial waves (slugs). 25e+06 2e+06 1 5e+06 le+06 F 500000 1 15 2 25 3 35 4 45 Fig. 8: Measured (dashed) and calculated (solid) pressure (Pa) vs. time (s) at the closed end for test 05.21.01-12. '05 21 01-test12NOV out u 1 5 140000 /FEB/EXPERIMENT/05 21 01/pace-pcb4-tl2dp exp'u 1 2--- 120000 100000 80000 60000 40000 20000 0 1 15 2 25 3 35 4 45 Fig. 9: Measured and calculated pressure (Pa) vs. time (s) in the middle of the pipe (PACE3) for test 05.21.01-12. 5e+06 ----------------------- ---- 5e+ 6 11 14 00-test11 out u 1 2 / /FEB/EXPERIMENT/11 14 00/pace-pcb4-t11 exp u 1 5 ---- 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 400000 S11 14 00-testll out u 15 --- / I FEB/EXPERIMENT/11 14 00/pace-pcb4-t11 exp' u 1.--'- 350000 - 300000 - 250000 200000 150000 100000 - 50000 --- l ----------- 05 1 15 2 25 3 35 4 45 Fig. 11: Measured and calculated pressure (Pa) vs. time (s) in the middle of the pipe (PACE3) for test 11.14.00-11. All computations were performed with an input model consisting of -170 volumes with the horizontal test section discretized in 60 volumes. Grid refinement was performed for all cases in the Table 1 with test section discretized into 120 volumes. Pressure peaks and times of the peaks obtained on the refined grid were typically up to 5% different. Conclusions Condensation-induced water hammer has been studied on the experimental device described by Martin et. al. (2007) and simulated with 1D two-fluid model of the computer code WAHA (Tiselj et. al. 2004). For the purpose of the present study WAHA was upgraded with ammonia thermo-physical still being tested as well as correlations for heat, mass and momentum transfer near the head of the slug. Current models for condensation in the slug head are being developed as a best fit with various experimental runs. Results of the simulation show that 1D two-fluid model can capture the main phenomena of the condensation-induced water hammer, however, reliable prediction of the condensation-induced water hammer in the current configuration is still not possible. Behaviour at various initial temperatures, pressures and hot gas flow rates are well described for initial filling of the pipe of around 50%, while non-existent condensation-induced water hammers are predicted at low liquid fillings (10-20%). Acknowledgements This research was financially supported by the Ministry of Higher Education, Science and Technology, Republic of Slovenia, project no. J2-1134 and research project of the EU 7th FP NURISP 05 1 15 2 25 3 35 4 45 Fig. 10: Measured (dashed) and calculated (solid) pressure (Pa) vs. time (s) at the closed end for test 11.14.00-11. "05 21 01-testl2NOV out u'l 2 / /FEB/EXPERIMENT/05 21 01/pace-pcb4-tl2dp exp u 1 5 ---- S --.- ._- ,- Paper No 7th International Conference on Multiphase Flow ICMF 2010, Tampa, FL USA, May 30-June 4, 2010 References 1978. Bartosiewicz Y., Seynhaeve J.-M., Vall6e C., H6hne T., Vall6e C., Lucas D., Beyer M., Pietruske H., Schiitz P., Carl Lavi6ville J.-M., Modeling free surface flows relevant to a H., Experimental CFD grade data for stratified two-phase PTS scenario: comparison between experimental data and flows, Nuclear Engineering and Design, in press (2010) three RANS based CFD-codes. Comments on the (doi:10.1016/j.nucengdes.2009.11.011) CFD-experiment integration and best practice guideline, proceedings of XCFD4NRS, Grenoble, France, 2008. Dobson M.K, Chato J.C, Condensation in smooth horizontal tubes, Journal of Heat Transfer ASME 120, 193-213, 1998. Bestion D., The Physical closure laws in the CATHARE code, Nuclear Engineering and Design, 124, pp. 229-245, 1990. Bjorge R.W., Griffith P, Initiation of Waterhammer in horizontal and nearly horizontal pipes containing steam and subcooled water, ASME Journal of Heat Transfer 106, pp8350840, 1984. Carlson K.E., Riemke R.A., Rouhani S.Z., Shumway R.W., Weaver W.L., RELAP5/MOD3 Code Manual, Vol. 1-7, NUREG/CR-5535, EG&G Idaho, Idaho Falls, 1990. Issa R.I., Kempf M.H.W., Simulation of slug flow in horizontal and nearly horizontal pipes with the two-fluid model, International Journal of Multiphase Flow 29, pp 69-96, 2003. Lin PY., Hanratty T.J., Prediction of the initiation of slugs with linear stability theory, International Journal of Multiphase Flow 12(1), pp 79-98, 1986, Martin C. S., R. Brown R., J. Brown J., Condensation-Induced Hydraulic Shock Laboratory Study, ASHRAE 970-RP, June 2007 Martin C.S. Condensation-induced water hammer in a horizontal refrigerant pipe, Proceedings of BHR Pressure Surges,, 581-589, 2004. Rukes B., Dooley R.B., Guideline on the IAPWS Formulation 2001 for the Thermodynamic Properties of Ammonia-Water Mixtures,, (2001) Strubelj L., Ezsol G, Tiselj I., Direct contact condensation induced transition from stratified to slug flow. Nucl. Eng. Des.. vol. 240, no. 2, str. 266-274, doi: 10.1016/j.nucengdes.2008.12.004, 2010 Taitel Y., Dukler A.E., A model for predicting flow regime transitions in horizontal and near horizontal gas-liquid flows, AICHE Journal 22, pp. 47-55, 1976. Tiselj I., Horvat A. Cerne G, Gale J., Parzer I., Mavko B., Giot M., Seynhaeve J. M., Kucienska B., Lemonnier H., WAHA3 Code Manual, Jo2ef Stefan Institute Report, IJS-DP-8841, March 2004 Tiselj I., Petelin S., Modelling of Two-Phase Flow with Second-Order Accurate Scheme. Journal of Computational Physics, vol. 136, pp. 503-521, 1997 Wylie E.B., Streeter VL., Fluid Transients, | http://ufdc.ufl.edu/UF00102023/00506 | CC-MAIN-2014-52 | refinedweb | 6,978 | 51.89 |
"Do something when a value is changed" in Python Node?
Hi,
Is there a way to perform an action if a value is changed?
The logic would be something like this:
If new value != with the existing value: do something:
Here is the existing code (inside of a Python node in an Expresso)
import c4d #Welcome to the world of Python def main(): store_value = 0 # The value ranges from 0 or 1 if Input1 != store_value: print "Something changed" store_value = Input1 else: print "Nothing changed"
The problem is at next draw/redraw/refresh the store_value stays at zero even though the Input is already at 1. This means the
store_value = Input1is not working.
You can check the illustration file here:
Upon opening the file, you'll see in the console printing "Nothing Changed" repeatedly. Now if you change the user data. It prints "Something Changed" but then it continuously prints "Something is changed".
The result should be something like
Nothing Changed # Changes user data Something changed # Back to Nothing Changed Nothing Changed
Is there a way around this? Thank you for looking at the problem
Hi @bentraje the way to go is to use a global variable. This will define a variable in the global space of the current node that will be frame independent and will live as long as the node itself live.
import c4d global store_value store_value = 0 def main(): if not c4d.threading.GeIsMainThread(): return global store_value if Input1 != store_value: print "Something changed" store_value = Input1 else: print "Nothing changed"
Cheers,
Maxime.
Thanks for the response. I tried the code but I still get the same result.
Nothing changed first.
Something changed.
Then something changed all throughout.
You can see the revised file here:
Sorry, I edited the code, the main issue is that you defined each time the new value to 0.
Cheers,
Maxime.
No worries. Thanks again for the reply!
Just one last thing:
Is there a way to save the store_value when closing and then reopening the file?
The current set-up is
user_data value = 0.
When you change the value from 0 to 1. It works perfectly (i.e. prints something is changed)
However, when the set-up is the
user_data value = 1(the user changed it in the last session),
and change the value from 1 to 0, it prints "Nothing changed" where it should be "Something changed".
Not sure if this is possible since
store_value=0is hard coded. Or do you have any alternative to the set-up? I'm all ears! Thank you
Hi sorry I overlooked your answers.
If you want to have something more consistent you should store it into the scene. So the things that make more sense is to store it into the basecontainer of the current GvNode. Like so
import c4d def main(): if not c4d.threading.GeIsMainThread(): return bc = op.GetDataInstance() # Get an unique ID at store_value = bc[1000001] if Input1 != store_value: print "Something changed" bc[1000001] = Input1 else: print "Nothing changed"
Cheers,
Maxime. | https://plugincafe.maxon.net/topic/11649/do-something-when-a-value-is-changed-in-python-node | CC-MAIN-2021-17 | refinedweb | 499 | 74.79 |
.
Obtaining GPS fix using Java ME
There have been many posts on the Java Forum regarding the Location API (JSR-179) and the fact that sometimes no GPS fix can be obtained through those.
Many times the problem can be identified as a "time-out" exception, which means that the GPS chip couldn't return a GPS position within a determined time-window.
It has been apparent that some people actually try to obtain a GPS fix without knowing anything about GPS-technology, which makes it even harder to pinpoint where the problem might be...
So we are gonna make some assumptions and see where the developer himself could try to force a GPS fix out of this hard-headed hardware :D
The assumptions are :
- GPS-satellites are still happily circling the earth, and are all 100% functional, so no aliens actually shot those down
- the internal/external GPS-receiver is also a 100% functional, so the device didn't fall in water or something like that
So now you have written your code using the Location API's, and it runs pretty good in the emulator... But when installed on a device you simply can't seem to get a GPS fix... What can you do ?
Step 1
Most probably you have the Nokia Maps software installed on your device also. Fire that up and WALK OUTSIDE ! To get a GPS fix your device must be able to connect to at least 3 satellites, this DOES NOT happen if there is x inch/cm of concrete between the device and the outside air where the signals are actually traveling... So your device will need a good portion of clear sky to look for satellites.
If the Nokia Maps app will get a fix (note this may take even up to 5 minutes !!! This is called a cold-fix) you can close it down and fire up your own application. Hopefully this resolved your issue, otherwise let's try step 2.
Step 2
Well if step 1 didn't work and the aliens still haven't shot our GPS satellites down the problem might be in your code! At some point you will have set up a Criteria to be used to determine your LocationProvider. Try to "loosen" the criteria as much as possible, for example something like :
Criteria cr= new Criteria();
cr.setCostAllowed(true);
cr.setPreferredPowerConsumption(Criteria.NO_REQUIREMENT);
and maybe set the accuracy to very low, so setting a high value :
cr.setVerticalAccuracy(5000);
cr.setHorizontalAccuracy(5000);
Hopefully that helped ! Try this OUTSIDE once again :D
Step 3
Well, that didn't work ?. So last shot to get this problem out of the world! There are two methodologies to obtain a location with the Location API's :
Type 1 : Polling for a Location. You create a LocationProvider, feed it a Criteria and then you politely ask it to give you a Location :
lp= LocationProvider.getInstance(cr);
position = lp.getLocation(60);
Type 2 : Interrupt-driven. You still create a LocationProvider and feed it a Criteria. But then you make use of the LocationListener() Interface so that when a Location is available (or when you need a Location every x seconds) it will simply be passed to the LocationUpdated() method within your MIDlet!
First extend the class with the interface:
public class myClass implements LocationListener
Then attach the LocationListener to the LocationProvider :
lp.setLocationListener(this, interval, -1, -1);
And then obviously this method will be needed as part of the LocationListener interface:
public void locationUpdated(final LocationProvider locationProvider, final Location location)
That last one will be called whenever a Location is available...
Also a complete code example can be find within :
Java Developers Library 3.3 -> JavaDocs -> (JSR-179)Location API's
There have been reports of problems whilst using the "polling" mechanism, so ALWAYS try the LocationListener mechanism as well !!!
Again GO OUTSIDE and test the app!
Hopefully now you are able to get a GPS fix, if not most probably the aliens actually did shoot down the satellites, and the last thing you should be worying about is getting a GPS fix! | http://developer.nokia.com/community/wiki/index.php?title=Obtaining_GPS_fix_using_Java_ME&oldid=199793 | CC-MAIN-2015-14 | refinedweb | 683 | 59.53 |
Mostly ZIP extension files are called compressed file of file(s). We create zip from various program (UI) or via command utility.
In this article, you will learn the following things.
What is a Zip File?
Often, the files with zip extension are compressed files. We can create a zip file using various programs (UI) or via the command utility; such as -
Program UIs
Command Line Utilities
There are various ZIP utilities which compress our one or more files into a single ZIP file.
(Logo copied from for display and educational purpose)
As you can see in the above WinZip logo icon, a compressing machine is compressing the files and folders. Usually, the ratio of text, doc, and XLS files compression is way higher than the images and video files.
ZIP Utility
In old days, developers used third-party utilities or drivers to create a zip file programmatically, such as -
But then, Microsoft introduced a new namespace called System.IO.Compression in .NET 4.5 and above frameworks. Using this namespace, we can create a zip file very easily.
This namespace has the following utility and commands.
ZipFile a is static class which has the following methods,
In this article, we are going to create a zip file by using Windows.Forms application.
Let's start step by step.
STEP 1
Create a Windows.Forms application called “ZipWinFormApp”.
STEP 2
Double-click on Form1.CS file in Solution Explorer. You can switch ON the Solution Explorer by pressing "CTRL + ALT + L" or "ALT + V + P".
Now, again, double-click on the canvas of Form1.cs file. You can see Form1_Load method gets opened by-default. Let's start writing the code inside this method.
Now, right-click on References folder and select Assemblies >> Framework. Select the following two libraries.
And add the followings namespace to Form1.cs on the top.
Go through the following links of MSDN pages to learn more.
STEP 3
Now, switch again to Form1.cs file and drag and drop the following items on Form1.cs canvas.
FolderBrowserDialog This dialog box is used to browse and select the folder to further processing. In the following image, as you can see, this control is easily available inside Dialogs option.
You can easily get TextBox and Button control inside Common controls and All Windows.Forms tab.
Now, it's time to give naming to our following controls and titles.
Select TextBox and right click on TextBox, select Property option.
Now, let us start coding the buttons to implement the functionality.
On Browse Button (btnBrowse), write the following code.
On Create Zip button (btnZip), write this code.
OUTPUT
Start the project by pressing F5.
Click on "Select Folder" button.
After folder selection,
As I clicked on Create Zip button.
You can see in above images, I have selected the path as C:\Users\admin\Desktop\MyArticles. The Zip file will be created inside d:\Backup folder.
The Zip file will be created every time with date and time stamp in the network. Any user can take backup of the data file or folder very easily without any overwriting or any problem.
Thank you …
Happy coding…
View All | https://www.c-sharpcorner.com/article/create-zip-system-io-compression-from-winform-applicaton2/ | CC-MAIN-2020-45 | refinedweb | 528 | 68.57 |
Learn C++ Concepts with Visual Studio and the WSL
Andrew
Concepts promise to fundamentally change how we write templated C++ code. They’re in a Technical Specification (TS) right now, but, like Coroutines, Modules, and Ranges, it’s good to get a head start on learning these important features before they make it into the C++ Standard. You can already use Visual Studio 2017 for Coroutines, Modules, and Ranges through a fork of Range-v3. Now you can also learn Concepts in Visual Studio 2017 by targeting the Windows Subsystem for Linux (WSL). Read on to find out how!
About concepts
Concepts enable adding requirements to a set of template parameters, essentially creating a kind of interface. The C++ community has been waiting years for this feature to make it into the standard. If you’re interested in the history, Bjarne Stroustrup has written a bit of background about concepts in a recent paper about designing good concepts. If you’re just interested in knowing how to use the feature, see Constraints and concepts on cppreference.com. If you want all the details about concepts you can read the Concepts Technical Specification (TS).
Concepts are currently only available in GCC 6+. Concepts are not yet supported by the Microsoft C++ Compiler (MSVC) or Clang. We plan to implement the Concepts TS in MSVC but our focus is on finishing our existing standards conformance work and implementing features that have already been voted into the C++17 draft standard.
We can use concepts in Visual Studio 2017 by targeting the Linux shell running under WSL. There’s no IDE support for concepts–thus, no IntelliSense or other productivity features that require the compiler–but it’s nice to be able to learn Concepts in the same familiar environment you use day to day.
First we have to update the GCC compiler. The version included in WSL is currently 4.8.4–that’s too old to support concepts. There are two ways to accomplish that: installing a Personal Package Archive (PPA) or building GCC-6 from source.
But before you install GCC-6 you should configure your Visual Studio 2017 install to target WSL. See this recent VCBlog post for details: Targeting the Windows Subsystem for Linux from Visual Studio. You’ll need a working setup of VS targeting Linux for the following steps. Plus, it’s always good to conquer problems in smaller pieces so you have an easier time figuring out what happened if things go wrong.
Installing GCC-6
You have two options for installing GCC-6: installing from a PPA or building GCC from source.
Using a PPA to install GCC
A PPA allows developers to distribute programs directly to users of apt. Installing a PPA tells your copy of apt that there’s another place it can find software. To get the newest version of GCC, install the Toolchain Test PPA, update your apt to find the new install locations, then install g++-6.
[text]
sudo add-apt-repository ppa:ubuntu-toolchain-r/test
sudo apt update
sudo apt install g++-6
[/text]
The PPA installs GCC as a non-default compiler. Running
g++ --version shows version 4.8.4. You can invoke GCC by calling
g++-6 instead of
g++. If GCC 6 isn’t your default compiler you’ll need to change the remote compiler that VS calls in your Linux project (see below.)
[text]
g++ –version
g++-6 –version
[/text]
Building GCC from source
Another option is to build GCC 6.3 from source. There are a few steps, but it’s a straightforward process.
- First you need to get a copy of the GCC 6.3 sources. Before you can download this to your bash shell, you need to get a link to the source archive. Find a nearby mirror and copy the archive’s URL. I’ll use the
tar.gzin this example:
[text]
wget http://[path to archive]/gcc-6.3.0.tar.gz
[/text]
- The command to unpack the GCC sources is as follows (change
/mnt/c/tmpto the directory where your copy of gcc-6.3.0.tar.gz is located):
[text]
tar -xvf /mnt/c/tmp/gcc-6.3.0.tar.gz
[/text]
- Now that we’ve got the GCC sources, we need to install the GCC prerequisites. These are libraries required to build GCC. (See Installing GCC, Support libraries for more information.) There are three libraries, and we can install them with apt:
[text]
sudo apt install libgmp-dev
sudo apt install libmpfr-dev
sudo apt install libmpc-dev
[/text]
- Now let’s make a build directory and configure GCC’s build to provide C++ compilers:
[text]
cd gcc-6.3.0/
mkdir build
cd build
../configure –enable-languages=c,c++ –disable-multilib
[/text]
- Once that finishes, we can compile GCC. It can take a while to build GCC, so you should use the
-joption to speed things up.
[text]
make -j
[/text]
Now go have a nice cup of coffee (and maybe watch a movie) while the compiler compiles.
- If
makecompletes without errors, you’re ready to install GCC on your system. Note that this command installs GCC 6.3.0 as the default version of GCC.
[text]
sudo make install
[/text]
You can check that GCC is now defaulting to version 6.3 with this command:
[text]
$ gcc –version
gcc (GCC) 6.3.0
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
[/text]
Trying out Concepts in VS
Now that you’ve updated GCC you’re ready to try out concepts! Let’s restart the SSH service again (in case you exited all your bash instances while working through this walkthrough) and we’re ready to learn concepts!
[text]
sudo service ssh start
[/text]
Create a new Linux project in VS:
Add a C++ source file, and add some code that uses concepts. Here’s a simple concept that compiles and executes properly. This example is trivial, as the compile would fail for any argument
i that doesn’t define
operator==, but it demonstrates that concepts are working.
[cpp]
#include <iostream>
template <class T>
concept bool EqualityComparable() {
return requires(T a, T b) {
{a == b}->bool;
{a != b}->bool;
};
}
bool is_the_answer(const EqualityComparable& i) {
return (i == 42) ? true : false;
}
int main() {
if (is_the_answer(42)) {
std::cout << "42 is the answer to the ultimate question of life, the universe, and everything." << std::endl;
}
return 0;
}
[/cpp]
You’ll also need to enable concepts on the GCC command line. Go to the project properties, and in the C++ > Command Line box add the compiler option
-fconcepts.
If GCC 6 isn’t the default compiler in your environment you’ll want to tell VS where to find your compiler. You can do that in the project properties under C++ > General > C++ compiler by typing in the compiler name or even a full path:
Now compile the program and set a breakpoint at the end of
main. Open the Linux Console so you can see the output (Debug > Linux Console). Hit F5 and watch concepts working inside of VS!
Now we can use Concepts, Coroutines, Modules, and Ranges all from inside the same Visual Studio IDE!
Example: concept dispatch
The example above shows that concepts compile properly but it doesn’t really do anything. Here’s a more motivating example from Casey Carter that uses a type trait to show concept dispatch. This is a really great example to work through to illustrate the mechanics of constraints.
[cpp]
#include <iostream>
#include <type_traits>
template<class T>
concept bool Integral = std::is_integral<T>::value;
template<class T>
concept bool SignedIntegral = Integral<T> && T(-1) < T(0);
template<class T>
concept bool UnsignedIntegral = Integral<T> && T(0) < T(-1);
template<class T>
void f(T const& t) {
std::cout << "Not integral: " << t << ‘\n’;
}
void f(Integral) = delete;
void f(SignedIntegral i) {
std::cout << "SignedIntegral: " << i << ‘\n’;
}
void f(UnsignedIntegral i) {
std::cout << "UnsignedIntegral: " << i << ‘\n’;
}
int main() {
f(42);
f(1729u);
f("Hello, World!");
enum { bar };
f(bar);
f(‘a’);
f(L’a’);
f(U’a’);
f(true);
}
[/c! | https://devblogs.microsoft.com/cppblog/learn-c-concepts-with-visual-studio-and-the-wsl/ | CC-MAIN-2019-43 | refinedweb | 1,364 | 63.49 |
snd_ctl_read()
Read pending control events
Synopsis:
#include <sys/asoundlib.h> int snd_ctl_read( snd_ctl_t *handle, snd_ctl_callbacks_t *callbacks );
Arguments:
- handle
- The handle for the control connection to the card. This must be a handle created by snd_ctl_open() .
- callbacks
- A pointer to a snd_ctl_callbacks_t structure that defines the callbacks for the events.
Library:
libasound.so
Use the -l asound option to qcc to link against this library.
Description:
The snd_ctl_read() function reads pending control events from the control handle. As each event is read, the list of callbacks is checked for a handler for this event. If a match is found, the callback is invoked. This function is usually called on the return of the select() library call (see the QNX Library Reference).
If you register to receive notification of events (e.g. by using select()), it's very important that you clear the event queue by calling snd_ctl_read(), even if you don't want or need the information. The event queues are open-ended and may cause trouble if allowed to grow in an uncontrolled manner. The best practice is to read the events in the queues as you receive notification, so that they don't have a chance to accumulate. | https://developer.blackberry.com/playbook/native/reference/com.qnx.doc.neutrino.audio/topic/libs/snd_ctl_read.html | CC-MAIN-2020-34 | refinedweb | 199 | 73.47 |
I'm interested mostly in C++ and method/class name/signature automatic changes.
I do this a lot, so I'm axiously awaiting other replies too.
The only tricks I know are really basic. Here are my best friends in Emacs when refactoring code:
M-x query-replace
This allows you to do a global search and replace. You'll be doing this a ton when you move methods and commonly-accessed data to other classes or namespaces.
C-x 3
This gives you a display with two buffers side-by side. You can then proceed to load different files in them, and move your cursor from one to the other with
C-x o. This is pretty basic stuff, but I mention it because of how powerful it makes the next one...
C-x ( (type any amount of stuff and/or emacs commands here) C-x )
This is how you define a macro in emacs. Any time you find yourself needing to do the same thing over and over to a bunch of code (and it is too complex for query-replace), this is a lifesaver. If you mess up, you can hit
C-g to stop the macro definition, and then undo (
C-_) until you are back to where you started. The keys to invoke the macro are
C-x e. If you want to do it a bunch of times, you can hit
Esc and type in a number first. Eg:
Esc 100 C-x e will try to invoke your macro 100 times.
(Note: On Windows you can get "Meta" by hitting the Esc key, or holding down Alt). | https://codedump.io/share/odd12oBJYZB0/1/how-can-i-refactor-c-source-code-using-emacs | CC-MAIN-2018-26 | refinedweb | 274 | 79.6 |
Utility functions for working with strings. More...
#include <qgsstringutils.h>
Utility functions for working with strings.
Definition at line 27 of file qgsstringutils.h.
Returns the Hamming distance between two strings.
This equates to the number of characters at corresponding positions within the input strings where the characters are different. The input strings must be the same length.
Definition at line 164 of file qgsstringutils.cpp.
Returns the Levenshtein edit distance between two strings.
This equates to the minimum number of character edits (insertions, deletions or substitutions) required to change one string to another.
Definition at line 19 of file qgsstringutils.cpp.
Returns the longest common substring between two strings.
This substring is the longest string that is a substring of the two input strings. Eg, the longest common substring of "ABABC" and "BABCA" is "ABC".
Definition at line 101 of file qgsstringutils.cpp.
Returns the Soundex representation of a string.
Soundex is a phonetic matching algorithm, so strings with similar sounds should be represented by the same Soundex code.
Definition at line 203 of file qgsstringutils.cpp. | https://api.qgis.org/2.12/classQgsStringUtils.html | CC-MAIN-2020-34 | refinedweb | 178 | 69.68 |
More Thinking About Item Renderers
Well, the last post definitely got people thinking. Since then I've seen a few of you struggle with images, centering, etc. Again, if you're in a hurry, take a container and center an Image in it, but just be aware that that is kind of heavy.
This example shows how I would do it in order to optimize on performance. Most drop-in renderers like Image and CheckBox are comprised of child components that actually display the content, text and icons. By overriding the updateDisplayList methods, you can center the content without the cost of wrapping the renderer in a container.
This example also shows how to use labelFunction to map fields in your data to external or embedded images. The usual caveats and disclaimers apply.
-Alex
Great work man... exactly what I needed....
check this out I'm using it in the fullScreen mode of a photogallery:
Posted by: Maikel Sibbald | April 9, 2007 4:41 AM
Hi Alex,
I am pretty much completely lost in these examples, but I will start with a simple question. How is it that CenteredCheckBox is setting its selected state? How does it know to apply the value of its data property to its selected property?
Thanks,
Ben
-------------
Ben,
Sorry you got lost. Maybe what you're missing is that CheckBox, Image and some other out-of-the-box Flex components are drop-in item renderers. They implement IDropInListItemRenderer and know how to pick up extra information from the DataGrid such as which column they are renderering and therefore which dataField to pick out of the data.
If you just drop in CheckBox you'll see it work fine but left-aligned.
There's a lot of power in the standard components that can be leveraged once you figure out what they can do. And once you get a better understanding of that, it becomes more clear that lightweight subclassing of these components is better than the old Canvas-with-a-component pattern, which is much easier to learn, but may not be optimal.
Posted by: Ben | April 9, 2007 6:55 AM
Hi Alex, great work. I have a dude. If i click in the header for sort, the values of the chekboxes lost, it's by not have editor ??
----------
Yes, I did not add the code where clicking on the checkbox updates the dataprovider.
Posted by: Fabian | April 17, 2007 12:51 PM
Hi Alex,
may be you would be able to advise me. I’m looking for a solution to layout a row such what a line of text would start in the leftmost column and span multiple columns. Content of other columns should be pushed down as to allow space for the text line.
Thank you in advance,
Vlad
-------------
Haven't tried this yet, but you will probably need to know that the z order of renderers in a row is left to right where the right side is "above" the left. It turns out that once the list class determines the size and position of the renderer, you can change it later as long as you don't cause the list to re-render everything. So in your renderers' updateDisplayList, one should get really wide and the others should move down.
That's the theory. I think somebody got this to work. I'd try it myself but I'm pretty busy right now. Good luck
---------------
Yeah, this is how I'm trying to do it now, but it looks a bit too much as a hack. Well, as long as it works and there is no better way… :-)
Cheers,
Vlad
---------------
Yeah, we didn't support row/column span. There should be better support in the next major release.
Posted by: Vlad | May 4, 2007 8:06 PM
Hi Alex,
Thanks for your helpful CenteredWidgets example. I did have some trouble importing it into Flex, but that's because I am a Flex noobie.
Anyhow, my question is... I'm trying to make a very simple "Icon + text" combination. Let's say my icon is 16 pixels square. I'd want perhaps 8 pixels gap. And then the text to the right of the icon.
I want all this in one column!
What's the best way to do this in flex?
Should I extend your image to draw the text to the right of it? Oh wait, it's centered isn't it. I don't want it centered.
Thanks if you have any advice.
-----------------
I would take a UIComponent and add children Image and UITextField. You can look at the Flex framework source for ListItemRenderer for inspiration.
Posted by: Theodore H Smith | May 11, 2007 6:42 AM
Hi Alex,
I am trying to display some HTML data to Flex application. From Server it is coming as CDATA. It may contain tables, html text, images things.
Now I have 2 problems:
1. Which component is best to display such component. Is there any built in component for this?
2. I am displaying data in TextArea using its htmlText property. But it is not showing output as it is coming from server. Can u tell me why so?
Thanks in advance for looking in this problem.
----------------
Flash support for HTML is historically poor. Ask about it on FlexCoders and you'll see alternative approaches, one of which is called HTMLComponent. Oher support may get better over time, but no promises.
Posted by: Ashish Mishra | May 11, 2007 9:49 PM
Hi Alex,
I would like to create a list item renderer that displays a value as a horizontal bar, as in a bar graph. Do you have any suggestions on how to do this efficiently?
Thanks!
Rob
-------------------------------
I would start with UIComponent and draw a rectangle into its graphics layer. Hope that's enough info to get you started.
Posted by: Rob Turknett | May 21, 2007 1:14 PM
Alex,
I just read both of these articles about item renderers. I was really missing the mark. I will fix my grids and let you know how it went.
What the heck was I thinking. Thank you so much for the redirection. Your rock dude!
Thanks again,
Tony
Posted by: Tony | July 14, 2007 1:44 PM
Alex,
I'm trying to use the CenteredCheckBox in a datagrid, using actionscript instead of mxml. I've tried to get the backing arrayCollection to be updated when it changes, but it isn't working. It reflects the data being sent to the grid, but not the state of the checkboxes. Could you post a quick example of what needs to be added for it to fully function in a datagrid? Thanks, John
-----------
How to update depends a bit on the backing data. I implement change event handlers that update the data. You may need to call itemUpdated though
Posted by: John Lentz | July 25, 2007 8:58 PM
Alex, I wanted to personally thank you for saving me many painful hours. Thanks a million.
-Rameen
Posted by: rameen | September 20, 2007 2:02 PM
This works but you loose the ability to have a click event in the column which you have with an component.
Are there other methods of centering the image?
--------------
Not sure what you mean by that. You can always put some sort of alpha=0 shield over the entire column if you think you need to detect mouse outside the image bounds.
Posted by: Nigel | October 30, 2007 3:00 AM
Alex, these two posts on item renderers have helped me understand what is really going on in the DataGrid so much better than I ever did before. And my grid performance is better now too!
Thank you very very much for taking the time to help us all out. Most appreciated dude.
cheers, Adrian
Posted by: Adrian Parker | April 30, 2008 10:06 AM
Hi Alex,
Pretty useful demo here, but I'm having trouble extending it to meet my needs. The images I'm loading are of an unknown variety of heights and widths, and need to be resized to fit the cell if they're too big. I can get it working for the initial load, but the unpredictability of item renderers messes up the y values after a column re-order or two.
Keep up the good work
------------------------
Alex responds:
Pick a fixed size for the images and scale the actual images to fit. Then it should be more stable
Posted by: Jonathan | July 16, 2008 12:04 AM
alex,
i was trying to expand on some of the item renderer examples that you gave here, but i ran into some trouble. i am trying to create a renderer that has a clickable image and a text component. i decided to subclass TextInput and add a preceding image but it just doesn't render properly. when first displayed, the image is positioned at x=-8, y=-8. when the mouseover forces a redraw, the image is properly positioned. also, there appears to be a thin border at the bottom of the cell that i cannot get rid of. any help would be appreciated.
public class ParameterRenderer extends TextInput
{
private var image:Image;
public function ParameterRenderer()
{
super();
setStyle("borderStyle", "none");
setStyle("paddingBottom", 0);
}
override public function validateNow():void
{
// see BackgroundColorRenderer
}
override protected function updateDisplayList(w:Number, h:Number):void {
super.updateDisplayList(w, h);
// lifted from CenteredImage
if (image.content) {
var contentHolder:Loader = image.content.parent as Loader;
contentHolder.width = contentHolder.contentLoaderInfo.width;
contentHolder.height = contentHolder.contentLoaderInfo.height;
contentHolder.x = textField.x;
contentHolder.y = (h - contentHolder.contentLoaderInfo.height) / 2;
}
}
override protected function createChildren():void {
super.createChildren();
textField.selectable = false;
if (!image) {
image = new Image();
// attempt to get image to position properly
image.width = 16;
image.height = 16;
image.source = "../img/delete2.gif";
addChild(DisplayObject(image));
image.addEventListener(MouseEvent.CLICK, delete_onClick);
invalidateDisplayList();
image.move(2,0);
}
}
override protected function createBorder():void {
// thought this might get rid of bottom border
}
public function delete_onClick(event:MouseEvent):void {
// do something
}
-------------------
Alex responds:
ListItemRenderer has an icon and a TextField which could be editable. Might be easier to start there.
Posted by: del | July 22, 2008 7:07 PM
Hi Alex,
Thanks for these great demos. I was really struggling with itemRenderers until I found these articles.
I have a question about the centered checkbox example... My datasource is returning 0/1 for boolean data, rather than true/false, and I can't get the checkboxes to show selected. I tried adding a labelFunction that returns true if 1 and false if 0, but that doesn't seem to work either (even if I only return true from my labelFunction, they're all unchecked).
I feel like a total newb asking, but what am I missing?
Thanks
------------------------
Alex responds:
The checkbox just pulls the field. It won't listen to labelFunction. You could wrap data objects or override the data setter on checkbox.
Posted by: Chad | July 27, 2008 8:49 AM
Hi Alex,
A nice blog you've got going - bookmarked for later use, as I'm sure it will come up.
I have a really simple question... I'm trying to use custom renderers to format the text of each column's header individually - nothing fancy like checkboxes or comboboxes...just text. Might someone be able to tell me what I'm doing wrong here?
import fl.controls.dataGridClasses.HeaderRenderer;
import flash.text.TextFormat;
public class MyHeaderRenderer extends HeaderRenderer {
var myTextFormat:TextFormat = new TextFormat();
myTextFormat.bold = true;
myTextFormat.align = "center";
setStyle("headerTextFormat", myTextFormat);
//setStyle("textFormat", myTextFormat);
}
...and then:
myDataGrid.getColumnAt(0).headerRenderer = MyHeaderRenderer;
-------------------
Alex responds:
TextFormat is a low-level Flash thing that formats Text. The Flex style system doesn't use it until the very end and will overwrite any TextFormat you do apply.
Use CSS styles like fontWeight and textAlign insttead
Posted by: Nick Cherry | August 21, 2008 8:45 AM
I'm trying to reference a TextInput control inside an itemRenderer when a Button is clicked from within that same renderer. I'm able to change the text of the TextInput, but when I scroll down, I see that other rows (at random) have that same new value in their TextInput boxes. What am I doing wrong? Any workaround? Help!!!!
----------------------
Alex responds:
Classic symptoms of recycling. The contents of the TextInput need to be derived from the .data property
Posted by: Alex C | September 29, 2008 1:17 PM
Hi,
I have a problem using a custom ItemRenderer for a Horizontallist control. I require to use two comboboxes (wrapped in a canvas) to render Hlist control. That is, for each valuepair in HList will be rendered (and edited) by this custom component featuring two comboboxes. My problem is that I can't even figure out how to do it with a single combobox (wrapped in a canvas). I have successfully implemented the combobox itemrenderers in datagrid, but with HList, I don't know how to use getter/setter methods to pass data from HList to the rendered control.
Can you help me out? If I can get it work with a single combobox (wrapped in a canvas), I may manage to do the rest.
Thanks,
Mits
------------------------
Alex responds:
I'd ask on FlexCoders. It really depends on what your data looks like
Posted by: mitesh | November 25, 2008 12:13 PM
Hi Alex,
I want to use buttons with multiple lines inside of a tileList, have you any example of that?
Thanks in advance.
Rafael
----------------------
Alex responds:
Did you try using my multiline button example in a tile list?
Posted by: Rafael | February 6, 2009 1:36 PM
Hi Alex,
Very interesting article. Thank you for posting it. I have a much more complex need at this moment, which had me searching all through google and landed me (thankfully) here.
I would like to create a runtime itemRenderer. Basically, I have a DataGrid. This datagrid of course is fed in information in the form of an arrayCollection to display what has already been saved, as well as gives the option to add a new line item.
I would like to have a column completely driven by a drop-down selection in column one.
Example - column one has a combobox with three choices: gold, silver, other.
Column two would generate a combo box and populate it with choices of gold jewelry for choice1, or choices of silver jewelry for choice 2.
If the user selects other, a TextInput is rendered instead for manual entry.
I have tried so many things to get this to work, but am having so many issues. Mostly around getting data populated and saved, but also in some of the renderings as well.
Any suggestions?
Thanks,
Amanda
------------------------
Alex responds:
Should be possible. Remember to keep things data-driven. The second column's dataprovider should be based on the first column's data.
You may need a custom renderer that can either be a combobox or textinput.
I'd ask for help on FlexCoders. Some folks have solved parts of this problem before.
Posted by: Amanda | February 13, 2009 4:13 PM
Oh, and I forgot to mention that I am using Flex 2.
Thanks Alex!
---------------------------
Alex responds:
Then you'll probably have to use a custom renderer that switches its child from being a ComboBox or TextInput.
In Flex 3 some new APIs were added to data-drive which renderer is created.
Posted by: Amanda | February 13, 2009 4:16 PM
Alex,
I am going over your posts and was wondering if it is possible to combine a few of them into one sample. i.e. Let's say you have a datagrid whose dataprovider is an ArrayCollection provided to you by an outside method on the server. Then you want to do the following in one grid:
1. Ability to have EVERY header of the datagrid columns be a combo box. This is like your one example but by having each header with the same capability you get a real drill down capability.
2. The ability to render a complete row a color of red or yellow based on the word in one of the columns. i.e. You have a column say cable outage and if the row has the term scheduled outage you color that entire row red and it thus turns back to normal color when the term changes from scheduled to say none.
3. The ability to click one column's cell and have it pop-up a window with a checklist of three items. You select one of the three and it updates that cell.
4. The ability to take one entire column which contains time in Epoch value and display it as regular time.
Would the best way to do this be to create one component and extrapolate each concept as a specific render class. Also I am a simple guy trying to come up with a cool way to extend my internal tool at work. How long should it take to slap something like this together? I am attempting it on my own but we really really need this fast and I am not as strong a coder in flex as you are yet. Let me know. Thanks for all the tips and demo's you have made so far.
--------------------------
Alex responds:
I wish I could create examples for everything, but I don't have the time. It's hard to estimate how long it will take you. I would ask questions on FlexCoders. You'll get faster responses there.
Posted by: Raymond | February 22, 2009 8:33 PM
Alex, I appreciate your column. I am a new Flex developer and would like to know how to reset a combobox item renderer in a datagrid column. I understand that item renderers are reused and I am seeing that. I have a combobox itemrenderer for a cell in a data grid. After I have added a couple of rows and selected an item from the dropdown list, if I delete a row or two then add another row I see the selection from a previous row in the combobox. I also understand that I need to reinitialize the item renderer so that it appears blank on the new row but I don't know how. Your help will be greatly appreciated. Thanks very much.
----------------------
Alex responds:
Everything in a renderer should be data-driven (derived from the data property). The ComboBox will by default set its selection to the text of the item if it can find it in the ComboBox's dataProvider.
If you need further assistance, you'll get faster response posting to FlexCoders or the Adobe forums.
Posted by: Fred Allen | April 8, 2009 12:35 PM
Hi there!,
I have problem with my tilelist. I want to view the data in tilelist in random order. The data are form xml list. How can i view data in random order? . Please send reply to my email.Thanks!
-gina
---------------------
Alex responds:
Sorry, I cannot help you directly via email. Please post your question to one of the forums. Other folks will have a chance to help you as well.
Posted by: gina | April 12, 2009 10:22 PM
Hi Alex,
I got two questions regarding Itemrenderers.
1) I have used your centered CheckBox but if a user changes the state of checkbox it is not updating the collection.
2) Similarly I have used radiobutton as item renderer in one column and assigned them to a RadioButton Group so that the user can only select one row at a time. problem here is I want to preselect one radio button during initialization. can you hlp me how to do that .
I was struggling really hard with these two issues.Any help would be appreciated
thanks in advance
vin
---------------------------
Alex responds:
I think you might find the Checkbox and DataGrid posts helpful for both those problems. You can swap in the centered checkbox for the regular checkbox
Posted by: vin | June 15, 2009 11:18 AM | http://blogs.adobe.com/aharui/2007/04/more_thinking_about_item_rende.html | crawl-002 | refinedweb | 3,339 | 73.68 |
Python language / CPython interpreter ideas
- Security audit of python. Using as many automated processes as possible.
- Clean up the porting ifdefs, including os and posixmodule
- Python speed up. Reduce memory usage, speedup startup time. The two main speed regressions of the 2.0, 2.1,2.2,2.3,2.4 releases. (438,453,499,771,880) syscalls vs 106 for latest perl. 0m0.031s, 0m0.029s, 0m0.037s, 0m0.059s, 0m0.057s real time to start vs 0m0.007s for the latest perl.
Add a MemoryUsageProfiler to python. Currently it is almost impossible to figure out where memory is going in a large python program, especially if you have C extensions loaded. It'd be nice to know where the memory is going, if there are circular references, or if objects are being held too long. See the bcannon-sandboxing branch in svn for an attempt at a proof-of-concept. There have been several attempts with varying success: and
- math speedups or IO speedups (I think the string-in-base-10 to an int was recently sped up, but there may be other similar locations)
SpeedUpInterpreterStartup
../PythonGarbageCollected
../RegisterVirtualMachine
- Add regular code-coverage (both C and Python) to the build system (maybe even to Buildbot?)
- Better introspection support for C functions: ability to expose arguments through inspect. Might require retrofitting existing extensions.
See
- Provide more and better debugging of reference counting, garbage collection, and other memory issues for extension and embedding authors.
- Write tools that leverage the new compiler AST-- tools to analyze code, walk the AST, modify it, allow a modified AST to be compiled back to bytecode. Work on PEP 267.
Create a practical statistical profiler designed for inclusion in core Python. (You might want to take a look at Andy Wingo's statprof profiler as a starting point. -- SkipMontanaro) Also/alternatively, create a thread-aware profiler -- none of the current profilers are useful with multi threaded code.
The development of the new NumPy has led to good ideas for how to get a generic multidimensional array object into Python 2.6. Somebody willing to work with the NumPy developers to take the essential portions of NumPy and create a basearray (also called a dimarray) that could be included as a base-class multidimensional array object along with a general-purpose data-type object. This project has already been started but needs someone with time to help it along. See the Array Interface description page for an SVN check-out. This project has large impact potential for Python.
Improve Python threading performance, maybe remove GlobalInterpreterLock (GIL). (Note that the chance of getting a remove-the-GIL patch into core Python is near zero.) Reducing memory usage, and other resource usage will give a nice speedup.
- Improve cross-compiling support of Python interpreter.
- Deprecate .pyo files and come up with a way of specifying what optimizations have taken place within the bytecode. Would work well with also implementing a way to have user-defined optimizations take place at .pyc creation time.
Auto-generate code (as much as is reasonably possible) to go from Python's parse tree to the AST (essentially generate a large chunk of ast.c.
Bootstrap the pure Python implementation of import (found here, but a newer version lives here) so that it can be used as the actual import mechanism instead of the C implementation.
- Try to speed up access to the built-in namespace. Various proposals in the past have come up about how to deal with shadowing of built-ins (including a new keyword). | http://wiki.python.org/moin/CodingProjectIdeas/PythonCore | CC-MAIN-2013-20 | refinedweb | 592 | 56.86 |
Tech Off Thread34 posts
C++0x (vs2010) question, please tell me what i'm doing wrong
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Pagination
Hello fellow C++0x programmers.
I have this code:
The 'test_f' works as it should but test_c class, which does the same basically, does not.
Problem list:
1. How to make this compile. What am i missing / doing wrong.
2. Why do i have to type "test_c<int, void(int)>" instead of just "test_c<int>", the compiler should be able to figure that out, it did that for "test_f"
Thanks for your help.
It works for test_f due to "template argument deduction". This applies only to template functions, not to template classes.
Don't use void(int). That simply means a function that takes an int and returns nothing. normal_struct_func is not a function, it's an object that has a () operator aka function object, functor etc. You could use std::function (make sure you include <functional>):
> "template.
In this particular case it seems to me that the simplest solution is to get rid of the Function template argument:
@Mr Crash: For your specific problem, I like Dexter's way better; however, since stuff like this pops up occassionally, here is another way:This works in VC++2010 and MinGW's port of g++ 4.5.2. Here's the command line for MinGW's g++ 4.5.2: This code produces the following output:
Hope This Also Helps,
Joshua Burkholder
Very interesting and helpful answers, thank you.
I decided to see how many times i could shot myself in the foot.
Basically if i could make something that was lighter then the suggestions.
That is without std::shared_ptr and std::function.
And yet again i managed to get into a fight with the compiler
This is sandbox code so expect strangeness and inconsistencies:
Ok, so the problem i'm having:
In <T*> version of 'scoped(scoped &&right)' (that's the class i've used as test subject)
How to make 'right.m_onLeaveScope' accept the new empty function ?
The compiler complains:
"error C2275: 'default_empty<T>' : illegal use of this type as an expression"
due to 'm_onLeaveScope_empty(default_empty<T>)' on line
explicit scoped(T *p = nullptr, OnLeaveScopeFunc func = default_delete<T>) : m_ptr(p), m_onLeaveScope(func), m_onLeaveScope_empty(default_empty<T>) {}
I can't see why i doesn't want to work.
"OnLeaveScopeFunc func = default_delete<T>"
Worked fine so why doesn't that want to work ?
I've also tried:
"OnLeaveScopeFunc func_empty = default_empty<T>"
'm_onLeaveScope_empty(func_empty)'
explicit scoped(T *p = nullptr, OnLeaveScopeFunc func = default_delete<T>, OnLeaveScopeFunc func_empty = default_empty<T>) : m_ptr(p), m_onLeaveScope(func), m_onLeaveScope_empty(func_empty) {}
You're trying to assign a type name (default_delete<T>) to a variable (m_onLeaveScope_empty), you forgot.
> Anyway, it still won't work. Once you fix this you'll get another error: '`anonymous-namespace'::<lambda1>::(const `anonymous-namespace'::<lambda1> &)' : cannot convert parameter 1 from 'default_empty<T>' to 'const `anonymous-namespace'::<lambda1> &'
I knew i forgot to mention something, it was 3 am when i wrote that, sorry about that.
I did get that error too, which made me confused and got me thinking i've forgot some c++ rule again.
> Again, you're mixing up things that look like functions but they have different types.
Yes, can you explain what i'm missing, please ?
How would i make it work or is that not a possibility without std::function ?.
Yes, I've thought of that, it would work for the pointer version, but not for the non pointer version.
We can't really test for m_obj != 0 since 0 might be a totally valid value.
The possible solution would be to add a bool that gets set to true (is_empty = true) when the data is moved.
This, i'm guessing, would also be faster then calling an empty function.
But i'm not sure which way to go. I want it to be correct and as performance as possible so i'm still wondering if there is some kind of template magic to sole this.
But i'm leaning to the bool solution or perhaps i should use std::function...
Am i overthinking it ?
Yep, the non pointer version is an issue, didn't look at it as it didn't have compile errors
Performance wise I'd say that the bool variant is the fastest. std::function is cleaner but it has larger time & space overhead. But you know what they say, premature optimization is the root of all evil. Things like CreateFile or LoadLibrary will take far more time to complete than the few instructions that are need by make_scope/scoped.
If you really want it to be fast then the first thing you'll want to do is to get rid of make_scoped, it's not "free".
Interesting topic.
But the code examples above will generate a lot of overhead for the small tasks it seems to be for. For example using it as a scoped_array.
Best would be if you could make the optimizer inline , etc..
Make the compiler do the heavy work for us.
Like this little code example:
Generated code in win32 release mode:
Shouldn't you be able to achieve this with the power of c++0x but without this big overhead ?
I don't understand... that's exactly what the compiler did. The code in main is the code from normal_function, 3 calls to the stream insertion operator and nothing else.
@Dexter: The code in my post was just an example of compiler optimization. How a good template class should work.
Both your code and Burkholder's code have a big overhead.
Is there a way to minimize the overhead like in my example ?
OK,.
I posted this link on last Advanced STL show:
here an except of the code (how to register a function to call)
is_convertible and decay seens what you are looking for deal with functors, function and lambdas. There are other interesting stuff on the blog. (I think I see an example with std::bind for additional "magic"call somewhere, I'll try re-digg it)
Here's how STL would do it:. | https://channel9.msdn.com/Forums/TechOff/C0x-vs2010-question-please-tell-me-what-im-doing-wrong | CC-MAIN-2017-13 | refinedweb | 1,049 | 71.85 |
as the topic says if i include <fstream> and <allegro.h> i get a lot of errors.so i searched the forums for a solution but even with the -D__GTHREAD_HIDE_WIN32API -flag i get errors like these:
cbot.cpp:26: error: use of 'fixed' is ambiguous
/usr/include/allegro/fixed.h:28: error: first declared as 'typedef int32_t fixed' here
/usr/lib/gcc/i686-pc-linux-gnu/4.0.3/../../../../include/c++/4.0.3/bits/ios_base.h:951: error: also declared as 'std::ios_base& std::fixed(std::ios_base&)' here
...
what to do now?
Brutalo Deluxe 2 | BD2 Movie | BDNE 1.29 (C++ TCP Socket Wrapper) | Stats
Show us the line with the error.
-- Tomasu: Every time you read this: hugging!
Ryan Patterson - <>
cbot.cpp:26
fixed distance=itofix(1000);
seems to be some conflict with the fixed format.
Do you happen to have a using namespace in your headers?
--RTFM | Follow Me on Google+ | I know 10 people
Yes, do NOT do using namespace std if you are going to be using fixed. (Since std::fixed is a stream manipulator, you will end up with (std::)fixed and fixed in your namespace).
::fixed distance=itofix(1000);
_______________________________Indeterminatus. [Atomic Butcher]si tacuisses, philosophus mansisses
Do you happen to have a using namespace in your headers?
No!
::fixed distance=itofix(1000);
this works but is this really the only way?and what does this exactly - in all my source files where i use the std-code there is a "using namespace std" ?
It tells the compiler to use the version of fixed not in any namespace--the one on the global scope.
so there isn't an workaround for this?i can't imagine that i'm the only one who got this problem...
Nobody uses fixeds
And the workaround is not to use using namespace std;. This is the reason namespaces exist.
you mean to use the :: (scope-operator), heh?there is no such thing like a namespace allegro, right?
there is no such thing like a namespace allegro, right?
Right.
And as for the workaround: If you don't want to use ::, and you also don't want to write std:: everywhere, instead of using namespace std; you can put using std::vector; for example (of course, you'd have to do that for everything you're using from the std namespace).
As long as you don't write using std::fixed; then, fixed isn't ambiguous, hence you won't need to explicitly identify which one you want.
ok thanksor i'll change my fixed to float... | https://www.allegro.cc/forums/thread/586045/593070 | CC-MAIN-2018-34 | refinedweb | 428 | 76.01 |
Agenda
See also: IRC log
Zakin, aadd is Peter
<scribe> Scribe: Peter
Namespace:
discussion of NS and where it is used
we should not expect to change NS
we do have soapjms:bindingVersion message property that defines the SOAP-JMS version
are we ok with ?
<Derek> +Derek
general agreement
<PhilAdams> +1
RESOLUTION: namespace is
Once we have CVS access we will make the editorial changes identified.
These should be done by end of June.
Testing and Conformance
can someone scribe while I cal in again
<markphillips> yes I will
<eric> I've got to sign off - sorry.
need to develop tests in the form of client app that sends requests
need to identify all the assertions in the binding spec.
decide how to test each of the assertions
<scribe> ACTION: Peter and Phil will take a first pass of the spec to identify assertions [recorded in]
<trackbot-ng> Created ACTION-5 - And Phil will take a first pass of the spec to identify assertions [on Peter Easton - due 2008-05-27].
identify assertions on a section by section basis
consolidate later
we should ask Yves to give suggestions on how to construct a test plan and test assertions
anything else to discuss today?
This is scribe.perl Revision: 1.133 of Date: 2008/01/18 18:48:51 Check for newer version at Guessing input format: RRSAgent_Text_Format (score 1.00) No ScribeNick specified. Guessing ScribeNick: Roland Found Scribe: Peter WARNING: No "Topic:" lines found. Default Regrets: Yves Agenda: Got date from IRC log name: 20 May 2008 Guessing minutes URL: People with action items: p] | http://www.w3.org/2008/05/20-soap-jms-minutes | CC-MAIN-2016-30 | refinedweb | 265 | 68.81 |
Replacing Styled Components with a 1KB alternative Goober
Agney Menon
・3 min read
Styled Components and EmotionJS are two of the most popular CSS-in-JS libraries for the React land. But both of these do come with a cost, anywhere between 10KB to 20KB is how much any of these libraries would add to the your bundle.
What if we could replace the same with a 1KB library? That is the promise of GooberJS that uses the same
styled(element) paradigm styled-components and emotion popularised but at much lesser size.
Goober does this by utilising a custom pragma pattern which is already used in cases like the
css prop in emotion or
sx prop in ThemeUI.
TLDR; JSX Pragma is a way of customising how JSX is compiled to React elements (
React.createElement) and adding our own thing in there.
Installation
You can install GooberJS with npm or yarn:
npm install goober # or yarn add goober
Usage
First, we have to set the pragma to match:
import { createElement } from 'react'; import { setPragma } from 'goober'; setPragma(createElement);
Note that this has to be performed only once in the whole application and would probably go in
index.js file in your application.
How do I styled an HTML element?
// It's a named export import { styled } from 'goober'; // Notice the parathesis. const Title = styled('h1')` font-size: 2rem; color: maroon; `; function Header() { return ( <header> <Title>Goober</Title> </header> ); }
Goober also supports nesting and SASS like
&:hover kind pseudo selectors as it's predecessors. You can also add media templates inside styled components to make it work.
How do I customise it with props?
import { styled } from 'goober'; const Title = styled('h1')` font-size: 2rem; color: ${props => props.textColor}; `; function Header() { return ( <header> <Title textColor="red">Goober</Title> </header> ); }
How do I extend a component?
import { styled } from 'goober'; const Title = styled('h1')` font-size: 2rem; color: ${props => props.textColor}; `; const LargeTitle = styled(Title)` font-size: 4rem; `; function Header() { return ( <header> <Title textColor="red">Goober</Title> </header> ); }
Global Styles?
Goober exposes
glob function for this. It is not to be imported/used anywhere else, just using this function would add the global styles as necessary.
import { glob } from 'goober'; glob` body { margin: 0; } `;
I do feel that styled components API did it better here with the
createGlobalStyle function. But if you have been with the project for long, you will know this is how it started off.
Missing
styled.tag?
If you are feeling attached to
styled.tag format from Styled Components, Goober team has a babel plugin that can help so that you can keep writing
styled.tag but the plugin will convert the references for you.
npm i --save-dev babel-plugin-transform-goober # or yarn add --dev babel-plugin-transform-goober
What's pending now?
- Goober does not automatically vendor prefix styles as of now, but they are proactively working on it.
- Goober does not support theming at the moment. Here is the PR they are working on.
But this should not discourage you from using theming at all. You can always fallback to using CSS variables (or create a Theme Context and work with it if you miss JavaScript theming)
Here is a kitchen sink of everything mentioned in this article:
What Makes You a Great Programmer on The Team?
Majority of software developers are aspired to be not only a competent professional but also a great one.
Neat! I'm a huge fan of the
1kb alternative togenre of JS libs.
Thank you @boywithsilverwings ! :) I appreciate the article and taking the time to write it! This is awesome! :D I'm so excited that I'll jump on the theme PR and hopefully I can have it under
1kbcause that's all that's left. But, that's what drives me and goober🥜!
Awesome, really awesome 👏👏👏👏
I will definitely give it a try!
Thanks!
Cool stuff! Is it supports TypeScript?
Yup! And that's because of our great community effort. It's been really awesome to see it happen! | https://dev.to/boywithsilverwings/replacing-styled-components-with-a-1kb-alternative-goober-39d8 | CC-MAIN-2020-16 | refinedweb | 673 | 64.81 |
The following syntax is very intuitive. Run in Spyder, and it plots a nonlinear function.
import numpy as numpy
import matplotlib.pyplot as plot
x = numpy.arange(0, 1, 0.01)
def nonlinear(x, deriv=False): #sigmoid
if (deriv==True):
return x*(1-x)
return 1/(1-numpy.exp(-x))
plot.plot(x, nonlinear(x))
nonlinear
plot.plot
nonlinear
It works fine because the usual arithmetic operations (e.g.
/ and
- as you've used) are defined for numpy arrays; they're just performed element-wise. The same goes for
np.exp(). You can see exactly what
nonlinear(x) looks like for yourself (it's also a numpy array):
>>> import numpy as np >>> def nonlinear(x): return 1/(1 + np.exp(-x)) ... >>> nonlinear(np.arange(0, 1, 0.1)) array([ 0.5 , 0.52497919, 0.549834 , 0.57444252, 0.59868766, 0.62245933, 0.64565631, 0.66818777, 0.68997448, 0.7109495 ])
You're just finding the value of the sigmoid evaluated at each point in the specified range, and passing those as the y-values to
plot. | https://codedump.io/share/gU8IS2G3ftxL/1/how-does-matplotlib-accept-function-parameters-are-they-lambdas | CC-MAIN-2016-50 | refinedweb | 175 | 70.39 |
performance check if - What's the most efficient way to test two integer ranges for overlap?
Given two inclusive integer ranges [x1:x2] and [y1:y2], where x1 ≤ x2 and y1 ≤ y2, what is the most efficient way to test whether there is any overlap of the two ranges?
A simple implementation is as follows:
bool testOverlap(int x1, int x2, int y1, int y2) { return (x1 >= y1 && x1 <= y2) || (x2 >= y1 && x2 <= y2) || (y1 >= x1 && y1 <= x2) || (y2 >= x1 && y2 <= x2); }
But I expect there are more efficient ways to compute this.
What method would be the most efficient in terms of fewest operations.
Great answer from Simon, but for me it was easier to think about reverse case.
When do 2 ranges not overlap? They don't overlap when one of them starts after the other one ends:
dont_overlap = x2 < y1 || x1 > y2
Now it easy to express when they do overlap:
overlap = !dont_overlap = !(x2 < y1 || x1 > y2) = (x2 >= y1 && x1 <= y2)
I suppose the question was about the fastest, not the shortest code. The fastest version have to avoid branches, so we can write something like this:
for simple case:
static inline bool check_ov1(int x1, int x2, int y1, int y2){ // insetead of x1 < y2 && y1 < x2 return (bool)(((unsigned int)((y1-x2)&(x1-y2))) >> (sizeof(int)*8-1)); };
or, for this case:
static inline bool check_ov2(int x1, int x2, int y1, int y2){ // insetead of x1 <= y2 && y1 <= x2 return (bool)((((unsigned int)((x2-y1)|(y2-x1))) >> (sizeof(int)*8-1))^1); };
If you were dealing with, given two ranges
[x1:x2] and
[y1:y2], natural / anti-natural order ranges at the same time where:
- natural order:
x1 <= x2 && y1 <= y2or
- anti-natural order:
x1 >= x2 && y1 >= y2
then you may want to use this to check:
they are overlapped <=>
(y2 - x1) * (x2 - y1) >= 0
where only four operations are involved:
- two subtractions
- one multiplication
- one comparison
If someone is looking for a one-liner which calculates the actual overlap:
int overlap = ( x2 > y1 || y2 < x1 ) ? 0 : (y2 >= y1 && x2 <= y1 ? y1 : y2) - ( x2 <= x1 && y2 >= x1 ? x1 : x2) + 1; //max 11 operations
If you want a couple fewer operations, but a couple more variables:
bool b1 = x2 <= y1; bool b2 = y2 >= x1; int overlap = ( !b1 || !b2 ) ? 0 : (y2 >= y1 && b1 ? y1 : y2) - ( x2 <= x1 && b2 ? x1 : x2) + 1; // max 9 operations | http://code.i-harness.com/en/q/31e33a | CC-MAIN-2019-09 | refinedweb | 398 | 63.43 |
Introduction
The current Joomla! help system has worked remarkably well over the years and has remained essentially unchanged since Mambo days. However, there are some inherent difficulties with it that lead to consideration of an updated help system.
- The back-end help server must be either a (remote) Joomla! installation or the local Joomla! filesystem. Non-Joomla! back-ends are not easily supported.
- There is no flexibility in the interface to the remote help server. The URL used to access the remote system is fixed and would require a core hack to change it.
- Similarly there is no flexibility in the interface to the local help files.
- The table of contents page is generated from the directory of local help files that happen to be present, plus those added from third-party component help directories. A new help file added to a remote help server is effectively invisible.
- Local help files can only be updated during the normal update cycle for Joomla! itself, whereas experience has shown that the development of help information works to a different cycle to that of the code.
- Arbitrary back-end help servers may be supported. In particular, we will be able to move the official help screens from help.joomla.org (a Joomla! instance) to docs.joomla.org (a MediaWiki instance) where they will be easier to maintain. This is perhaps the most significant reason for wanting to change the current help system as it makes it easier for the Doc WG to bring the help screens into the modular, re-usable documentation methodology that we are moving towards for the bulk of the documentation.
- All Joomla! produced error and warning messages become potential entry-points into the documentation. This will allow the user to obtain context-sensitive help with specific error conditions and by using a wiki the Dev and Doc WG can evolve the support given in the light of experience with the software.
- Flexible support for multi-language back-end help servers. We will have a range of options for handling multi-lingual help that are not be tied to a specific technology.
- All these same capabilities will be available for extension developers to exploit if they wish to.
- No changes are required to key references in the current code base.
- Existing help servers can continue to be used if required.
Help sites are currently listed in administrator/help/helpsites-15.xml, which can be thought of as a registry of available help sites. Currently this contains just the one entry:
Code: Select all
<?xml version="1.0" encoding="iso-8859-1"?>
<joshelp>
<sites>
<site tag="en-GB" url="">English (GB)</site>
</sites>
</joshelp>
This arrangement lacks the flexibility that will be required for this proposal, but rather than specify particular changes to the XML file the following changes to JHelp are suggested instead as this forms the API to access and manage the help sites registry. By talking about the API to the registry in abstract terms it can be left to others to decide the most appropriate physical implementation for the registry itself. This might turn out not to be an XML file.
The intention is that the help sites registry will contain information about all help sites including those used by the installed extensions.
Properties
Each registry entry has the following properties:
- key is a unique identifier string which can be used to reference a specific registry entry. All keys beginning with an underscore are reserved for use by Joomla! itself.
- type is a string indicating the type of the registry entry. The following types have special meaning:-
joomla means that the help site contains full help information for Joomla! These sites are the ones that will be listed as help sites in Global Configuration and the User Manager. Help sites that provide support for extensions will use their own type string.
- method is a string containing the name of the method used to access the help site. The currently supported methods are:- file to access files on a mounted filesystem; http to access web pages via the HTTP protocol. Support for other methods may be added in the future as required.
- name is a string describing the help site and is for display purposes only.
- resource is a string most likely containing a path or URL that will be used to access pages on the help site. A resource string may contain substitution codes that will be replaced before it is used (see later).
- selected is a boolean which indicates the preferred or currently selected help site amongst entries with a given type. For example, the default Joomla! help site selected in Global Configuration will have the selected property set to true while others with type = joomla are set to false.
JHelp manages the repository of information about help sites and is the API for access to the registry. The JHelp class requires the following methods:-
- addSite ( $key, $type, $name, $resource, $method='http' )
Adds a site to the registry.
- removeSite ( $key )
Removes a site from the registry.
- createUrl ( $key, $id, $extver='' )
Returns the URL (or path) to access the resource using the given reference. This method already exists but will need to be extended to support substitution codes in the resource name and the addition of a $key to specify which help site to use. The optional $extver parameter is so that third-party extension developers can pass an extension version string for the {extver} substitution code.
- createSiteList ( $type=null, $selected=false )
Returns an array of help sites which match the type requested. If $type is empty or null then all help sites will be returned. In effect, the type forms a namespace for help sites and extension developers should carefully select a unique name, probably based on the name of their extension, to avoid help site name collisions. This method already exists but needs to be modified to allow selection by type. If $selected is true then only help sites with the selected property set to true will be returned. Otherwise, help sites with selected property in either state will be returned.
- selectSite ( $key )
Sets the select property of the entry specified by $key to true. The select property of all other entries with the same type string as the one specified by $key will be set to false.
Resource substitution codes
The following codes (at least) should be available for substitution into the resource string by the createUrl method.
- {id} is a unique identifier for the help resource. For example, in the old-style key reference "screen.installer.15", the "screen.installer" part would be regarded as the {id}. This is just the $id parameter passed to createUrl.
- {version} is a shortened version of the for Joomla! version number comprising the major and minor version numbers with no dot separator. For example, for Joomla! 1.6.x {version} would be "16". This is backwards compatible with the current version suffix string.
- {major} is the major version number. For example, for Joomla! version 1.6.2 {major} would be "1".
- {minor} is the minor version number. For example, for Joomla! version 1.6.2 {minor} would be "6".
- {maintenance} is the maintenance release number. For example, for Joomla! version 1.6.2 {maintenance} would be "2".
- {language} is the ISO-defined language code for the current language. For example, "en-GB" is used for British English.
- {langcode} is the short language code consisting of the first two characters of the ISO-defined language code for the current language. For example, if the ISO language code is "en-US" then {langcode} would be "en".
- {client} is the Joomla! client name ("site" for the front-end, "administrator" for the back-end, "installer" for the installer).
- {extver} is the version of the extension (where relevant). This is just the $extver parameter passed to createUrl.
Example registry entries
The following two entries would give backwards compatibility with the current help server options.
key = “local”
type = “joomla”
method = “file”
name = “Local help”
resource = "administrator/help/{language}/{id}.{version}.html"
key = “joomla”
type = “joomla”
method = "http"
name = “English (GB) – help.joomla.org"
resource = "{id}.{version}”
The following example illustrates how local help files could be located anywhere on a local area network using a mounted filesystem.
key = “lan”
type = “joomla”
method = “file”
name = “LAN file server”
resource = “/mnt/net41/joomla/help/{language}/{id}.{version}.xml”
This example illustrates how the MediaWiki at docs.joomla.org could be used as a help server back-end. This example uses language pseudo-namespaces to serve multi-lingual help.
key = “wiki”
type = “joomla”
method = “http”
name = “Joomla! official documentation site”
resource = “{langcode}:{id}_{version}”
Another approach to multi-lingual help is to have separate help server instances each in its own subdomain. [Can the full ISO language code be used as a subdomain name? Would we want to do that anyway?]. This is the preferred approach for us to produce a multi-lingual documentation site.
key = “multi-lingual wiki”
type = “joomla”
method = “http”
name = “Multi-lingual documentation site”
resource = “http://{langcode}.joomla.org/docs/{id}_{version}”
We would implement a hard redirect of to using mod_rewrite.
For an example of a set of multi-lingual MediaWiki pages using this method see
For more information on multi-language support in MediaWiki see,
Core parameter types
helpsites
The core parameter type “helpsites” should be modified as follows:-
- default attribute will be used as the id parameter in a call to createSiteList.
- helptype is a new attribute that will be passed as the type parameter in a call to createSiteList.
- selected is a new attribute that will be passed as the selected parameter in a call to createSiteList. This attribute is optional.
Code: Select all
<param name=”helpsites” type=”helpsites” helptype=”com_musthave” default=”” label=”Help sites” description=”Select a help site” selected=”false” />
While not strictly necessary, a new core parameter type, called “help”, is proposed. This will allow extension developers to add a button to any parameter screen for access to extension and context-specific help information. It has the following parameters:
- name is the field name.
- type is 'help' to indicate that this a help parameter.
- helpsite will be passed as the key parameter in a call to createUrl.
- helpid will be passed as the id parameter in a call to createUrl.
- label will be used as a label for the button.
- description will be used as alternative text for the button.
will present a button labelled “Help me” which when clicked will pass “Help_with_parameter_x” via the {id} substitution code to the help site registered with key “com_musthave”.
Code: Select all
<param name=”helpwithsomething” type=”help” helpsite=”com_musthave” helpid=”Help_with_parameter_x” label=”Help me” description=”Click me for help with something” />
Extension Developers
Extension developers can add information about their own help servers into the registry using the $type field as a kind of namespace. Access to help for an extension can then be supported in the same way as with Joomla! itself, but without involving the official Joomla! websites. Help sites can be added to the registry using the addSite method in the com_install function (and removed using the removeSite method in the com_uninstall function).
However, a straightforward extension to the installer XML would simplify this for developers. For example, the following XML fragment could easily be supported to add a help site during component installation.
Code: Select all
<helpsites>
<helpsite key=”com_musthave” type=”com_musthave”>
<name>Must have component help site</name>
<resource>{id}.{extver}</resource>
</helpsite>
</helpsites>
Warning and Error Messages
Just as a user clicking on a help toolbar button can be thought of as a cry for help, the presentation of a warning or error message could be the precursor to such a cry. By adding a link in the message presented, the user can be given the opportunity to request help with the specific condition. Additionally, community experience with a particular error condition can be fed into the resource that is linked to by the error message so that feedback to the user can be improved over time.
Adding the link is easy to achieve programmatically but requires that each error/warning condition have a unique identifier that can be used to construct the URL. JHelp::createUrl is called to create the link, passing this unique id into the {id} substitution code. The following format for the id string is suggested:
Code: Select all
<package>_<subpackage>_<uid>
Where:
- <package> is the name of the package where the error/warning occurred. This should match the @package name in the phpdoc tags for the code where the error/warning occurred. Extension developers must not use the Joomla! package names (which should therefore be regarded as "reserved").
- <subpackage> is the optional name of the subpackage where the error/warning occurred. This should match the @subpackage name in the phpdoc tags for the code where the error/warning occurred. Extension developers are free to use subpackage names which match those used in Joomla! itself.
- <uid> is a unique numeric identifier for the error/warning condition. This identifier must be unique within the package. In other words, the same identifier must not be used in different locations within the same package. The <package><uid> together should form a globally unique identifier. The code 99999 has the special meaning of “not yet allocated”. Prior to a release, the codebase can easily be swept for occurrences of this code so that proper codes can be assigned. Code numbers are allocated sequentially and are not re-used.
Code: Select all
JFramework_Utilities_1234
It is then trivially easy to create a wiki page at which explains the error, possible causes and what to do about it. This can be kept up-to-date as experience with the error condition grows.
By adding each wiki error page to a special “error” category, the wiki will automatically maintain an alphabetical contents page so that it becomes easy to assign the next sequential error code.
Tooltips
An interesting but probably impractical extension to this idea is to store tooltip text in the back-end help server and have it retrieved, perhaps via AJAX, as the user hovers over the relevant region. This would be useful because the tooltip text could then be transcluded into the help screen text. This would help to ensure that tooltip and help screen text is kept up-to-date with the minimum of effort. Raw wiki text can be retrieved programmatically using the MediaWiki API which returns it with a minimal XML wrapper. The tooltip text chunks might also be re-used elsewhere in the documentation.
The MediaWiki API is described here:
Admin help page
At present the user is presented with an alphabetical table of contents generated from all the local help files, together with local help files found in all the installed components. Whilst quite clever, this is not all that helpful as it is merely listing the help screens available from individual screens in the software. It would be nice to find a way to present task- or goal-orientated information instead.
The suggestion here is that the left-hand list merely comprises a list of registered help sites that are currently selected. Clicking on any of the links will bring up a page with a standard id, perhaps “Start_here”. This page must be present on all registered help sites for this to work. The content of this standard page can be anything but in the case of the Joomla! help sites should be lists of tasks or goals, perhaps grouped by user type (eg. editor, publisher, administrator, etc). Extension developers can choose to organise their help sites in other ways if they choose.
The top item on the help sites list should always be the help sites for Joomla! itself, followed by registered extension help sites. When the help page is first presented, the “Start_here” page for Joomla! will therefore be shown.
Impact on performance
Having the createUrl method retrieve the resource from the help sites registry could have a performance impact depending on how the registry is implemented. However, the resource can easily be cached to mitigate this.
The proposal regarding tooltips clearly adds network latency to the time taken to show tooltip text to the user. Whether this will be acceptable is uncertain. | http://forum.joomla.org/viewtopic.php?f=502&t=268156&start=0 | CC-MAIN-2016-30 | refinedweb | 2,712 | 56.15 |
Hi,
I have made a very simple program ...It goes like this
package ch03;
public class mytest {
public static void main(String[] args) {
System.out.println("is the class file getting generated");
}
}
when i compile this "javac mytest.java " it gets compiled properly. But when i try to run it..." java mytest " it says class not found. I have also tried running it as "java ch03.mytest ". Could u pls help me abt this.
package ch03;
Awaiting replies,
Thanks,
Saru
Hi,
The process follows something like this. Give a try.
1. Compiling the java file -> javac -d . <filename.java>
2. Running the program -> java <package>.<classname>
This must work. The reason is that if you simply try to compile as javac <filename.java> it will not generate any package structure and therefore no class file and so it cant find the class file at the time of running.
This is my understanding.
For furthur information type javac -d at the command prompt and u must be displayed a pageful of info regarding compiling.
Good Luck,
Narayana :-)
Also See the "java compilation problem...pls help" thread | http://forums.devx.com/showthread.php?140552-getting-selected-checkbox-help!&goto=nextoldest | CC-MAIN-2016-44 | refinedweb | 185 | 79.06 |
I downloaded a US State extract from CloudMade, imported into Nominatim, and found that house numbers are not recognized.
I don't understand why I am getting completely different results than nominatim.openstreetmap.org.
Would I get better results from a full planet OSM file? I kind of have cold feet with the experience so far from this small extract.
Thanks
asked
19 Apr '12, 00:11
Norm1
126●4●5●8
accept rate:
0%
edited
19 Apr '12, 11:12
SomeoneElse ♦
35.3k●70●362●843
My table location_property_tiger is empty, could that have anything to do with not finding house numbers? Where would that source data come from?
location_property_tiger
Maybe we need some testcases to see where the problem is.
And perhabs you can ask ... she seems to be involved in some way to Nominatim.
Thank you, I will reach out to lonvia.
On a side note, is anyone here running a copy of Nominatim? Is your table location_property_tiger empty?
I scoured through the source code of OSM and Nominatim and I don't see anything that is responsible for populating data for that table.
Here is a perfect example with missing house numbers:
In the US, the OSM instance of Nominatim uses TIGER address data to complement the still sparse OSM house number data. You can add TIGER data to your own Nominatim instance by following these steps:
./utils/imports.php --parse-tiger-2011 <tiger directory>
./utils/setup.php --import-tiger-data
Be warned that the import can take a very long time, especially if you are importing all of the US.
Note: answer updated for TIGER 2012 data.
answered
23 Apr '12, 19:36
lonvia
5.9k●2●53●84
accept rate:
38%
edited
17 Jul '13, 10:52
Cheers, lonvia. Your instructions were spot on!
Hello, I'm having this problem when I try to import tiger data by following the steps you mention. I've downloaded the edges from here
The command I use is ./utils/imports.php --parse-tiger-2011 EDGES/
I get the output of this sort:
File "/Nominatim/utils/tigerAddressImport.py", line 50, in <module>
import ogr
ImportError: No module named ogr
Failed parse (/root/tiger/ftp2.census.gov/geo/tiger/TIGER2011/EDGES/tl_2011_01001_edges.zip)
Any help you could give will be extremely appreciated!
You need the GDAL package for python. In Ubuntu install it with sudo apt-get install python-gdal.
sudo apt-get install python-gdal
I am running this command ./utils/imports.php --parse-tiger-2011 /osm/tiger_data/ but the process does not start and no output even.
Looks like the changes for the 2012 and 2013 editions haven't made it into the release yet. You need the import script from the latest git version. It is safe to simply clone the latest version temporarily and run the TIGER import from there.
@mezbaur I needed to put the edge zip file(s) in their own directory and pass that directory in as the argument. Hope that helps. Also you can get a specific county's EDGEs by going here Select "All Lines" from the drop down. Then choose the state/county.
Also note that this process took up a bunch of ram.
I imported it and it still seems to not be working
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This is the support site for OpenStreetMap.
Question tags:
nominatim ×670
house ×38
number ×11
cloudmade ×6
question asked: 19 Apr '12, 00:11
question was seen: 9,186 times
last updated: 14 May '14, 23:46
Tiger House Numbers
How to edit house numbers
How can I add house number to the map?
Units on the same street with the same "addr:housenumber", how do you tag?
Street Numbers for Australia
Nominatim House Numbers Problem
! | https://help.openstreetmap.org/questions/12150/missing-house-numbers-in-local-nominatim-instance?sort=newest | CC-MAIN-2022-21 | refinedweb | 646 | 66.13 |
Python's None: Null in Python (Overview)
None is a powerful tool in the Python toolbox. Like
True and
False,
None is an immutable keyword. As the
null in Python, you use it to mark missing values and results, and even default parameters where it’s a much better choice than mutable types.
Now you can:
- Test for
Nonewith
isand
is Not
- Choose when
Noneis a valid value in your code
- Use
Noneand its alternatives as default parameters
- Decipher
Noneand
NoneTypein your tracebacks
- Use
Noneand
Optionalin type hints
Congratulations, you made it to the end of the course! What’s your #1 takeaway or favorite thing you learned? How are you going to put your newfound skills to use? Leave a comment in the discussion section and let us know.
This was all very helpful. So thank you.
But it has confused me about something I had thought I understood.
I use if var: a lot to test if data exists. And I’m usually basing that on a returned function.
e.g.
def main(input): test = test_func(input) if test: do_something() else: do_something_else() def test_func(input): if input == something: return something
Is it wrong of me, then, to use this Truthy/Falsey if test: approach? My test_func is returning None if the condition is not met, and so I want my main func to do_something_else().
To ensure this, would I be better writing if test is not None: instead?
Using explicit comparison is more Pythonic because it clearly states your intent. That’s one of the core philosophies you’ll find in the Zen of Python.
More importantly, however, relying on implicit truthy/falsy values is risky because it may not work as expected, depending on what your functions return. For example, if zero (
0) should be considered a success, which often is in Unix programs, then your condition won’t work, because zero evaluates to false in a Boolean context.
As a rule of thumb, use explicit comparison whenever possible.
By the way, it’s also worth noting to avoid double negation in expressions like this:
if test is not None: success() else: failure()
You can swap the order to make it a little easier on the eyes:
if test is None: failure() else: success()
Become a Member to join the conversation.
Agil C on July 30, 2020
Thanks for the video..! | https://realpython.com/lessons/python-none-summary/ | CC-MAIN-2020-34 | refinedweb | 394 | 70.84 |
Considerabstraction ? What we need is to constrain the instrument in the method.
My initial implementation was to make the
AccruedInterestCalculatora separate class parameterized with the
Tradeoftype I for any specific method within
Tradebeyond what was specified as the constraint in defining the
Tradeclass.and
Bshould exactly match
A <:< B, which mandates that
Amust conform to B
- A
A <%< B, which means that A must be viewable as B
Predef.scala contains these definitions. Note that unlike <: or >:, the generalized type constraints are not operators. They are classes, instances of which are implicitly provided by the compiler itself to enforce conformance to the type constraints. Here's an example for our use case ..
class Trade[I <: Instrument](id: Int, account: String, instrument: I) {
//..
def accruedInterest(convention: String)(implicit ev: I =:= CouponBond): Int = {
//..
}
}
evis the type class which the compiler provides that ensures that we invoke
accruedInterestonly for
CouponBondtrades. You can nowclassinstruments, you can express the constraint succinctly using
<:<..
class Trade[I <: Instrument](id: Int, account: String, instrument: I) {
//..
def validateInstrumentNotMatured(implicit ev: I <:< FI): Boolean = {
//..
}
}method whole being within the trade class. Calculating
accruedInterestis a normal domain operation for a
CouponBondtrade - {
def calculate(principal: Int, tradeDate: java.util.Date): Int
}
case class DefaultImplementation(name: String) extends CalculationStrategy {
def calculate(principal: Int, tradeDate: java.util.Date) = {
//.. impl
}
}
But how do we use it within the core API that the
Tradeclass publishes ? Type Classes to the rescue (once agian!) ..
class Trade[I <: Instrument](id: Int, account: String, instrument: I) {
//..
def accruedInterest(convention: String)(implicit ev: I =:= CouponBond, strategy: CalculationStrategy): Int = {
//..
}
}
and we can now use the type classes using our own specific implementation ..
implicit val strategy = DefaultImplementation("default")
val cb = CouponBond("IBM", 10)
val trd = new Trade(1, "account-1", cb)
trd.accruedInterest("30U/360") // uses the default type class for the strategy
Now we have the best of both worlds. We implement the domain constraint on instrument using the generalized type constraints and use type classes to make the calculation strategy flexible.
14 comments:
Thanks for the post, that is very useful. Looking forward to reading the DSL in Action book too.
Interesting things these constraints, thanks for bringing this up - where could one learn the new 2.8 features (and some advanced pre 2.8) systematically?
I don't know anything about the domain - so the following might not be necessary. But its seems as if you now moved the strategy (for calculation) back into the class. And you cant overload the implicit (implicit ev: I =:= OtherBond): (I guess ?). So whenever you want another accruedInterest with this trade but with another Instrument, you have to create a method with a different name, instead of a new class as was before. Did you really gain a lot?
@joe accrued interest is only applicable for coupon bonds - that's one of the domain assumption in my case. You r correct .. if I had to do some polymorphic stuff, a separate abstraction would have been better. But here it's not the case - so it sets up nicely with the =:= type class that Scala 2.8 offers.
Fantastic! I wasn't aware of this feature. Like others I don't fully understand the domain though.
This kind of post is really, really valuable because it shows the relevance of Scala in a real-world setting (who said that Scala was an academic-only language :-)?).
My only comment would be along what Joe wrote: "its seems as if you now moved the strategy (for calculation) back into the class".
It is fairly likely that on a real-world project doing so will clutter your Trade class and bring on more and more dependencies on that class.
So I think that a short update showing how you can re-extract that logic to a "pimped" Trade class, with an implicit definition using the same kind of generalized type constraint and leaving the client code untouched would be useful (which bring us back to a TypeClass pattern doesn't it?).
Isn't it what you will eventually do on your real project?
Very nice post! I have just one small point to add. Generalized type constraints are in no way ``magical'', the compiler knows nothing about them. There are just these three classes in Predef: :<, <%<, =:= together with implicit definitions that give you the roper instances. If you want to rename them to something like conformsTo, visibleAs, equalTo, you can, and things will work the same way.
So anyone could have written these classes, it's not that they are burned into the language.
The new thing in 2.8 is that implicit resolution as a whole has been made more flexible, in that
type parameters may now be instantiated by an implicits search. And that improvement made these classes useful.
That's what I call a sweet spot in language design. You make an existing feature stronger and you get another one for free (the only other treatment of generalized type constraints I know of is Kennedy and Russo's work which appeared at OOPSLA 04. This was proposed, but to my knowledge never accepted, for C#).
BTW, prior to 2.8 the idea could more or less be expressed with
def accruedInterest(convention: String)(implicit ev: I => CouponBond): Int = ...
I say more or less because ev could be supplied by any implicit function that converts I to CouponBond. Normally you expect ev be the identity function, but of course somebody could have writen an implicit conversion from say DiscountBond to CouponBond which would screw things up royally.
To reiterate what Martin said, here's the definition of the =:= class
And here's the definition of the implicit that supplies instances of it.
No compiler magic that you can't use yourself.
Couple of comments:
1) The fact that the generalized type constraints are identifiers and not operators seem like a compiler technicality that users should not be exposed to. My naive reaction the first time I read about ":<:" was "why didn't they reuse ":<" since the meanings are so close to each other?
2) I don't know if it's your example or the concept, but it feels like your nicely generic class Trade has now been polluted with a specific implementation. This doesn't smell too good to me, but maybe I'm missing something?
Hi Cedric -
Thanks for visiting my blog. Addressing your second concern ..
Which specific implementation are u talking about ? Is it that of accruedInterest method ? AS I mentioned, if we can have only ONE implementation of the method, why can't we have it within the Trade class ? And if we have any variation, then we can refactor the variable part in the form of a strategy class. I have done exactly this in the update which I posted yesterday. Please have a look at the bottom of the post where I discuss this.
Would be willing to know your thoughts.
Debasish, I'm talking about CouponBound. Before you introduced the generalized type constraint, your Trade class was relying on the very generic Instrument class, and that was great.
After the type constraint, your interface is now coupled with a subclass (or an implementation) of Instrument.
This sounds like an implementation detail that should be handled with an instanceof internally instead of leaking into the interface and coupling your class with an implementation.
As for my first point: still no answer? Would you agree that :< would be acceptable instead of :=: or am I missing something?
Hi Cedric -
First let me address the issue with Coupon Bond. I agree that CouponBond is a specific implementation of Instrument.
At the same time the method accruedInterest is ONLY applicable for CouponBonds only. No other instrument type can have accrued interest. This is a domain constraint, which I need to express. In terms of the Trade abstraction, it turns out to be "A CouponBond trade needs to calculate the accrued interest". So in the problem domain itself there's a coupling between Trade and CouponBond.
What you have suggested is to keep the Trade abstraction *completely* generic without any coupling with implementation classes. That's what I did in the first implementation. The flip side however, is that the APIs are not always that intuitive. An accrued interest calculation is an innate component of a CouponBond trade valuation. Hence an API like
trade.accruedInterest(..) looks more natural than new AccruedInterestCalculator(..).accruedInterest(trade). It's just a
matter of taste I guess - I don't mind to couple an abstraction with some implementation if the problem domain model itself has such a coupling. And the generalized type constraints allow me to do that quite succinctly. However if I have variations within the implementation, then of course I need to refactor that in a Strategy, as I have shown in
the update to the post towards the end.
Now regarding your first concern, I agree that both <: and <:< has a similar underlying connotation of conformance. I think the designers chose a different symbol only to differentiate the fact that <: denotes an upper bound in a type
constraint, while <:< is actually a class in Predef. As Martin has indicated in his comment to my post, you could very well rename it to conformsTo instead of <:<. Also I am not sure if there would be any parser issue if they used the same
symbol for both cases.
Hi Martin / James -
Thanks for the very clear explanation. It's really great that these type constraints are plain Scala classes and NOT burned into the language core. Plus the improved implicit resolution in 2.8 has made them more potent in designing intuitive APIs (as I have demonstrated with a real world example).
Hi Kafecho -
Glad that you liked the post. Great to hear your comments on the book too. I hope you like it.
Debashish, Cedric,
The reason we could not use <: and <% is that these are reserved (i.e. keywords). As I have explained above, <:< and <%< are user-defined. So we could not have taken the same operators for them. It's like insisting hat you should use `if' for a conditional construct in a DSL - yes it would be nice if you could reuse `if' in that context, but unfortunately you can't. | https://debasishg.blogspot.com/2010/08/using-generalized-type-constraints-how.html | CC-MAIN-2018-05 | refinedweb | 1,706 | 65.12 |
0
I have tried and tried to figure out what it is I am have wrong. I have an assignment to create a program that calculates employee's bonus. I think I pretty much have it, but I keep getting an error that I cant figure out and what the error is trying to tell me. If someone could please help I would really appreciate it.
#include <iostream> #include <string> using namespace std; myfunc (int calc_bonus); int main ( ) { string name; int total_sales, bonus; cin >> name; cin >> total_sales; int calc_bonus(int sales){ int temp if (total_sales < 3001) temp = 0; if (total_sales > 3000 && < 5001) temp = 50; if (total_sales > 5000 && < 10000) temp = 100; if (total_sales > 9999) temp = 250; return temp } cout << “ name's bonus is ” << bonus << endl; }; // Exit program. return 0; }
Here is the error I got from the compiler
Line 21: error: stray '\342' in program
compilation terminated due to -Wfatal-errors.
Again, any assistance would be great! Thanks!
Edited by Nick Evan: Added code-tags. Always wrap your code in [code] ...code here... [/code] tags | https://www.daniweb.com/programming/software-development/threads/239554/error-i-cant-figure-out | CC-MAIN-2017-39 | refinedweb | 174 | 77.77 |
Declare::Constraints::Simple::Library::Base - Library Base Class
package My::Constraint::Library; use warnings; use strict; # this installs the base class and helper functions use Declare::Constraints::Simple-Library; # we can also automagically provide other libraries # to the importer use base 'Declare::Constraints::Simple::Library::Numericals'; # with this we define a constraint to check a value # against a serial number regular expression constraint 'SomeSerial', sub { return sub { return _true if $_[0] =~ /\d{3}-\d{3}-\d{4}/; return _false('Not in SomeSerial format'); }; }; 1;
This base class contains the common library functionalities. This includes helper functions and install mechanisms.
Installs the base classes and helper functions into the
$target namespace. The
%CONSTRAINT_GENERATORS package variable of that class will be used as storage for it's constraints.
Class method. Returns all constraints registered to the class.
Class method. Returns the constraint generator code reference registered under
$name. The call will raise a
croak if the generator could not be found.
Class method. This wraps the
$generator in a closure that provides stack and failure-collapsing decisions.
Class method. The actual registration method, used by
constraint.
Note that some of the helper functions are prefixed with
_. Although this means they are internal functions, it is ok to call them, as they have a fixed API. They are not distribution internal, but library internal, and only intended to be used from inside constraints.
constraint 'Foo', sub { ... };
This registers a new constraint in the calling library. Note that constraints have to return result objects. To do this, you can use the helper functions "_result($bool, $msg", _true() and _false($msg).
Returns a new result object. It's validity flag will depend on the
$bool argument. The
$msg argument is the error message to use on failure.
Returns a non-valid result object, with it's message set to
$msg.
Returns a valid result object.
Sets the current failure info to use in the stack info part.
This applies all constraints in the
\@constraints array reference to the passed
$value. You can optionally specify an
$info string to be used in the stack of the newly created non-valid results.
Puts
$value into an array reference and returns it, if it isn't already one.
This is the internal version of the general
Message constraint. It sets the current overriden message to
$msg and executes the
$closure with
@args as arguments.
Applies the
$constraint to
@args in a newly created scope named by
$scope_name.
Stores the given
$result unter the name
$name in
$scope.
Returns the result named
$name from
$scope.
Returns true only if such a result was registered already.
Declare::Constraints::Simple, Declare::Constraints::Simple::Library
Robert 'phaylon' Sedlacek
<phaylon@dunkelheit.at>
This module is free software, you can redistribute it and/or modify it under the same terms as perl itself. | http://search.cpan.org/~phaylon/Declare-Constraints-Simple-0.03/lib/Declare/Constraints/Simple/Library/Base.pm | CC-MAIN-2014-52 | refinedweb | 471 | 58.08 |
From: Peter Dimov (pdimov_at_[hidden])
Date: 2001-04-10 13:42:25
From: "Gary Powell" <Gary.Powell_at_[hidden]>
The new version breaks Intel 5.0:
C:\Projects\testbed\main.cpp(96) : internal error: assertion failed at:
"edgcpfe/expr.c", line 12892
auto_ptr<const Derived> pp(p);
When I tried to change this to
auto_ptr<const Derived> pp;
it complained that in
explicit auto_ptr(pointer rhs =0) throw()
: inherited(rhs)
pointer cannot be converted to void*. With the (void*) cast suitably
inserted main.cpp compiles.
The reason for the internal error turned out to be that the copy constructor
is wrapped with
#if !defined (BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP)
(AFAIK Intel does have Koenig lookup (it's EDG 2.41) so this may be another
problem with config.hpp.)
When I comment the #if/#endif lines it compiles but crashes when run. :-)
I wonder what copy constructor does MSVC use. :-)
-- Peter Dimov Multi Media Ltd.
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk | https://lists.boost.org/Archives/boost/2001/04/10925.php | CC-MAIN-2020-45 | refinedweb | 172 | 61.93 |
This, which is an open source web application server, serves up an HTML page with an embedded javascript code. The javascript would run in the user's browser and has instructions to retrieve the positional information from the mySQL database every second. It then integrates this information into Google Maps through Google Maps API which displays the position on a map. Since the positional information is retrieved every second and the maps updated at the same frequency, a real time GPS tracking effect is achieved. Mhz.'s APN (Access Point Name). If your cellular provider is not AT&T, replace the string "isp.cingular" with the appropriate APN for your cellular provider. In the line: cell.println("AT+SDATACONF=1,\"TCP\",\"your_ip_address\",32000"); Change this to the IP Address for your TCP Server.
//Include the NewSoftSerial library to send serial commands to the cellular module.
#include <NewSoftSerial.h>
#include <TinyGPS.h>
#include <PString.h>
#define POWERPIN 4
#define GPSRATE 4800
#define BUFFSIZ 90
char at_buffer[BUFFSIZ];
char buffidx;
int firstTimeInLoop = 1;
int GPRS_registered;
int GPRS_AT_ready;
//Will hold the incoming character from the Serial Port.
char incoming_char=0;
char buffer[60];
PString myString(buffer,sizeof(buffer));
//Create a 'fake' serial port. Pin 2 is the Rx pin, pin 3 is the Tx pin.
NewSoftSerial cell(2,3);
TinyGPS gps;
int redLedPin = 11;
int blueLedPin = 12;
// Function to Blink a LED
// Parameters: lPin - Pin of the LED
// nBlink - Number of Times to Blink
// msec - Time in milliseconds between each blink
void blinkLed(int lPin, int nBlink, int msec) {
if (nBlink) {
for (int i = 0; i < nBlink; i++) {
digitalWrite(lPin, HIGH);
delay(msec);
digitalWrite(lPin, LOW);
delay(msec);
}
}
}
// Function to Switch on a LED
// Parameters: lPin - Pin of the LED
void onLed (int lPin) {
digitalWrite(lPin, HIGH);
}
// Function to Switch off a LED
// Parameters: lPin - Pin of the LED
void offLed (int lPin) {
digitalWrite(lPin, LOW);
}
// Do system wide initialization here in this function
void setup()
{
// LED Pin are outputs. Switch the mode
pinMode(redLedPin, OUTPUT);
pinMode(blueLedPin, OUTPUT);
/* Blink the Power LED */
blinkLed(redLedPin,3,500);
//Initialize serial ports for communication.
Serial.begin(4800);
cell.begin(9600);
//Let's get started!
Serial.println("Starting SM5100B Communication...");
delay(5000);
/* Currently GPRS is not registered and AT is not ready */
GPRS_registered = 0;
GPRS_AT_ready = 0;
}
/* Reads AT String from the SM5100B GSM/GPRS Module */
void readATString(void) {
char c;
buffidx= 0; // start at begninning
while (1) {
if(cell.available() > 0) {
c=cell.read();
if (c == -1) {
at_buffer[buffidx] = '\0';
return;
}
if (c == '\n') {
continue;
}
if ((buffidx == BUFFSIZ - 1) || (c == '\r')){
at_buffer[buffidx] = '\0';
return;
}
at_buffer[buffidx++]= c;
}
}
}
/* Processes the AT String to determine if GPRS is registered and AT is ready */
void ProcessATString() {
if( strstr(at_buffer, "+SIND: 8") != 0 ) {
GPRS_registered = 0;
Serial.println("GPRS Network Not Available");
}
if( strstr(at_buffer, "+SIND: 11") != 0 ) {
GPRS_registered=1;
Serial.println("GPRS Registered");
blinkLed(redLedPin,5,100);
}
if( strstr(at_buffer, "+SIND: 4") != 0 ) {
GPRS_AT_ready=1;
Serial.println("GPRS AT Ready");
}
}
void loop() {
/* If called for the first time, loop until GPRS and AT is ready */
if(firstTimeInLoop) {
firstTimeInLoop = 0;
while (GPRS_registered == 0 || GPRS_AT_ready == 0) {
readATString();
ProcessATString();
}
if(POWERPIN) {
pinMode(POWERPIN, OUTPUT);
}
pinMode(13, OUTPUT);
Serial.println("GPS Parser Initialized");
digitalWrite(POWERPIN, LOW);
delay(1000);
Serial.println("Setting up PDP Context");
cell.println("AT+CGDCONT=1,\"IP\",\"isp.cingular\"");
delay(1000);
Serial.println("Activating PDP Context");
cell.println("AT+CGACT=1,1");
delay(1000);
Serial.println("Configuring TCP connection to TCP Server");
cell.println("AT+SDATACONF=1,\"TCP\",\"\",");
delay(1000);
Serial.println("Starting TCP Connection\n");
cell.println("AT+SDATASTART=1,1");
onLed(redLedPin);
} else {
while(Serial.available()) {
int c = Serial.read();
if (gps.encode(c)) {
onLed(blueLedPin);
float flat, flon;
unsigned long fix_age;
gps.f_get_position(&flat,&flon,&fix_age);
if(fix_age == TinyGPS::GPS_INVALID_AGE)
Serial.println("No fix detected");
else if (fix_age > 5000)
Serial.println("WARNING: Possible Stale Data!");
else {
myString.print("AT+SSTRSEND=1,\"");
myString.print("Lat: ");
myString.print(flat,DEC);
myString.print(" Long: ");
myString.print(flon,DEC);
myString.print("\"");
Serial.println(myString);
cell.println(myString);
myString.begin();
offLed(blueLedPin);
}
}
}
}
}.
#!/usr/bin/env python
import socket
import MySQLdb
TCP_IP = ‘your_ip_address"’
TCP_PORT = 32000
BUFFER_SIZE = 40
# ClearDB. Deletes the entire tracking table
def ClearDB(curs,d ):
curs.execute ("""
INSERT INTO gmaptracker (lat, lon)
VALUES (0.0,0.0)""")
d.commit()
# Connect to the mySQL Database
def tServer():
try:
db = MySQLdb.connect (host = "your_host",
user = "your_user",
passwd = "your_password",
db = "gmap" )
except MySQLdb.Error, e:
print "Error %d: %s" %(e.args[0], e.args[1])
sys.exit(1);
cursor = db.cursor()
# Start with a fresh tracking table
ClearDB(cursor,db)
# Set up listening Socket
try:
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
s.bind((TCP_IP, TCP_PORT))
print "Listening...."
s.listen(1)
conn, addr = s.accept()
print 'Accepted connection from address:', addr
except socket.error:
if s:
s.close()
print "Could not open socket: "
cursor.close()
conn.close()
db.close()
sys.exit(1)
try:
while 1:
data = conn.recv(BUFFER_SIZE)
if not data:break
str1,str2 = data.split("Long: ")
str1 = str1.split("Lat: ")[1]
latitude = float(str1)
longitude = float(str2)
cursor.execute ("""
INSERT INTO gmaptracker (lat, lon)
VALUES (%s,%s)""", (latitude,longitude))
db.commit()
except KeyboardInterrupt:
ClearDB(cursor,db);
cursor.close()
conn.close()
db.close()
if __name__ == '__main__':
tServer(), jayesh@’localhost’.
msql>; GRANT ALL PRIVILEGES ON *.* TO user@'host' IDENTIFIED BY 'password';.
Step 6:
PLONE
The next piece of software we need to install is Plone. Plone is a CMS (Content Management System) built on top of Zope, which is a popular web application server. We’ll be using only the Zope functionality of Plone and not it’s CMS features. In fact, using Plone for this application is an overkill since you can just download Zope and use that. I already had Plone installed on my computer and I’ll show you how to use Plone, but if you want to try Zope, you’re welcome to do that. The steps are very similar.
- Download Plone 3.3.5 from into /usr/local/src. ( I used Plone 3.3.5, Plone4 has a radically new interface and the steps below might not work. You’ll have to dig around, if you are using Plone4.)
- Install Plone
cd /usr/local/src sudo tar -xvf Plone-3.3.5-UnifiedInstaller.tgz cd Plone-3.3.5-UnifiedInstaller/ sudo ./install.sh standalone
- Note down the Username and Password displayed at the end of the installation process. You'll need it to access the Plone GUI. Plone will be installed in /usr/local/Plone
Go to the Zope Directory in Plone, in this case it's /usr/local/Plone/Zope-2.10.11-final-py2.4.
Download ZmySQLDA from into that directory and extract the tar file with the command:
sudo tar -xvxf ZMySQLDA-2.0.8.tar.gz
If everything goes ok, a ZMySQLDA directory will be created under /usr/local/Plone/Zope-2.10.11-final-py2.4/lib/python/Products.
ZMySQLDA is a SQL Database Adaptor that Zope will be using to talk to the database. ZMySQLDA using another piece of software called MySQLdb to perform it’s tasks. Let’s download and install MySQLdb now.
cd /usr/local/Plone/Zope-2.10.11-final-py2.4/lib/python/Products
Download MySQLdb from into that directory
Extract the tarball and install MySQLdb with the following commands:
sudo tar -xvf MySQL-python-1.2.0.tar.gz
cd MySQL-python-1.2.0
sudo /usr/local/Plone/Python-2.4/bin/python setup.py build sudo /usr/local/Plone/Python-2.4/bin/python setup.py install
One very important thing to note when building and installing MySQLdb is to use the same python binary that was shipped with Plone. If you don’t use the same exact python binary that was shipped with Plone, Plone won’t be able to find it. In this case the python binary that was shipped with Plone resides in /usr/local/Plone/Python-2.4/bin.
Start Plone
cd /usr/local/Plone/zinstance/bin sudo ./plonectl start
Wait for a few moments for Plone to start up and then open a browser and point it to:. This is assuming everything is on the same computer. If you are accessing from a different computer, change localhost to the IP Address of the computer running Plone.
You should see a dialog box for entering the username and password. Enter the username and password you noted down after the Plone installation process. You should see the root folder view as shown below:
1. Create a SQL Database Connection
Select the 'Z SQL Database Connecton' from the drop down list on the right. In the database connection string text box, enter gmap@host:port. Replace host and port with your hostname and port respecively. If the SQL database is running on the same machine as Plone, enter
gmap <username> <password>
Click the Browse tab of the Z MySQL Database Connection. You should be able to see your table (gmaptracker). Click the + sign and you should be able to see the elements of the table.
2. Add a Z SQL Method to retrieve the last row from the SQL table.
Select the 'Z SQL Method' from the drop down list on the right. Enter "GmaplocsPkSelectLastAdded" for id and "SQL Method to select Data" for tile.
Enter the code:
select * from gmaptracker order by id desc limit 1
Click Add.
From the root folder view, Click the GmaplocsPkSelectLastAdded method from the root folder view and click the Advanced Tab. Change the value of "Maximum rows to retrieve" to 0 (zero). Save the changes.
On why this should be done, read this.
3. Add a DTML Method
Go to the root folder view. Select the 'DTML Method' from the drop down list on the right. Enter "data.xml" for id and an descriptive title (can by anything you want). Click Add and Edit.
Enter the code
<?xml version="1.0" encoding="UTF-8"?>
<markers>
<dtml-in GmaplocsPkSelectLastAdded>
<marker lat="<dtml-var lat>" lng="<dtml-var lon>"/>
</dtml-in>
</markers>
Save the changes.
4. Add a DTML Document
Go to the root folder view. Select the 'DTML Document' from the drop down list on the right'. Enter "gpstrack.html" for id and a descriptive name. Click Add and Edit.
Enter the code:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"">
<html xmlns="">
<head>
<title>Real Time GPRS based GPS Tracker</title>
<script src="?
file=api&v=1" type="text/javascript"></script>
<!-- Make the document body take up the full screen -->
<style type="text/css">
v\:* {behavior:url(#default#VML);}
html, body {width: 100%; height: 100%}
body {margin-top: 0px; margin-right: 0px; margin-left: 0px; margin-bottom: 0px}
</style>
<script type="text/javascript">
//<![CDATA[
function load(){
var map = new GMap(document.getElementById("map"));
var point = new GPoint(0,0);
map.addControl(new GLargeMapControl());
map.addControl(new GMapTypeControl());
map.centerAndZoom(point, 1);
window.setTimeout(function(){reloadMap(map)},1000);
}
function reloadMap(map) {
var request = GXmlHttp.create();
request.open("GET", "data marker = new GMarker(point);
map.clearOverlays();
map.addOverlay(marker);
map.centerAtLatLng(point);
}
}
}
request.send(null);
window.setTimeout(function(){reloadMap(map)},1000);
}
// Monitor the window resize event and let the map know when it occurs
if (window.attachEvent) {
window.attachEvent("onresize", function() {this.map.onResize()} );
} else {
window.addEventListener("resize", function() {this.map.onResize()} , false);
}
//]]>
</script>
</head>
<body onload="load()">
<div id="map" style="width: 100%; height:100%;"></div>
</body>
</html>
Save the changes.
Step 7:
Open a browser to. You should see a plain blue Google Map Screen.
That's because the initialization co-ordinates are 0.0000000000 Lat and 0.0000000000 Long. That's in the Atlantic Ocean off the coast of Africa. Zoom back the map using the slider, if you don’t' believe me.
Once you power on the device, you should see the marker move to the correct GPS co-ordinates and it should update every second. Move around the GPS tracker around the house and see if it tracks properly. | http://www.instructables.com/id/Real-Time-GPS-Tracker-with-Integrated-Google-Maps/ | CC-MAIN-2017-17 | refinedweb | 1,995 | 52.26 |
Eclipse Community Forums - RDF feed Eclipse Community Forums Setting contextType for templates <![CDATA[I've run into some problems that I'm not sure how to solve. I'll describe what I want to achieve and then what I have done and tried so far. Hopefully someone can point out where I've gone wrong. What I want to achieve: The user edits an XML file in the WTP XML editor (or any other editor). If my plugin is active, the user should be able to get templates suggested that are relevant for the type of XMLs we use. These templates are linked to three different namespaces and only the templates that are appropriate depending on the current edit position should be shown. My work so far: I created three new context types: "org.eclipse.ui.editors.templates" - "contextType". Each context type will correspond to the three namespaces that will be relevant for us. I've added all templates to the extension point "org.eclipse.ui.editors.templates" - "template" and each template is set to one of my contextType. Now when the user want to get a template I have to determine which contexttype is relevant. This means finding out the namespace where the user is editing. So I have created a "org.eclipse.wst.sse.ui.completionProposal" - "proposalComputer". The class org.eclipse.wst.xml.ui.internal.contentassist.AbstractXMLCom pletionProposalComputer looked real nice to reuse, using the right interface and being abstract and all, BUT it is internal and I get "discouraged access" warning. Alot of other classes that would be real useful, like org.eclipse.wst.sse.ui.internal.contentassist.ContentAssistU tils have the same access problem. With copying several org.eclipse.wst.xml.ui.internal.* classes to my project and hardcoding one of the contexttype, I've been able to get the editor to show the templates, so it is working. But the discouraged access warning tells me that I'm probably on the wrong path... Bug atleast tells me I'm not the only one who've run into this issue. I guess I could create a specific editor that handles our XMLs, but since all we really want are the templates it seems like overkill. ]]> Fredrik Lindqvist 2011-01-18T17:53:26-00:00 Re: Setting contextType for templates <![CDATA[How did it turned out? Im currently working on my exam project and one part consists of doing generating some dynamic content assist proposals. Im trying to find a plugin.xml that extends the 'org.eclipse.wst.sse.ui.completionProposal' and explains exactly what i need but haven't been able to do so. Is there a chance you would like to post yours here and explain a bit about your completionProposal extension? MVH /Tobbe ]]> Torbjörn Lindberg 2012-03-19T13:56:02-00:00 | http://www.eclipse.org/forums/feed.php?mode=m&th=203181&basic=1 | CC-MAIN-2015-11 | refinedweb | 468 | 58.18 |
Stephan Herhut <S.A.Herhut at herts.ac.uk> writes: > module B(bar) where > instance Foo Integer where > module C(tango) > instance Foo Integer where > import B(bar) > import C(tango) > But now, ghc complains about two instances of Foo Integer, although > there should be none in the namespace main. I suspect the problem is that instances are always exported and imported, so that GHC sees both in Main, and complains. Perhaps this could be relaxed to allow your situation (where the class isn't used directly in Main anyway)? -kzm -- If I haven't seen further, it is by standing in the footprints of giants | http://www.haskell.org/pipermail/haskell/2004-July/014317.html | CC-MAIN-2013-48 | refinedweb | 106 | 63.7 |
Before you can compile and execute a Java application, you must setup a Java programming environment. There are various Java compilers, but the standard is the one distributed on the Sun Web site. You can download the Java 2 SDK, Standard Edition from.
On this page you will see three types of downloads for the latest released version and latest prereleased/release candidate (if available) version of Java. These three downloads are
Software Developers Kit (SDK)
Java Runtime Engine (JRE)
Documentation
The SDK is used to compile and execute Java programs; you will need to download this.
The JRE is used to execute Java programs, but does not contain anything for compiling them. People that use your Java applications will have to download and install JRE; the SDK includes the JRE so you don't need to download it.
The documentation is specifically for users of the SDK. It lists and explains all the public classes in Java. I would highly recommend that you download and install this (it is viewable directly from the Internet). If you are short on disk space, then you can browse through the documentation as you need it.
As of this writing, the latest version of the Java 2, Standard Edition is version 1.4.
There are links to installation instructions presented to you when you download the SDK, but the following sections summarize the installation steps.
The Java SDK for Microsoft Windows is an InstallShield® file that guides you through the installation using wizard-like screens.
Download the SDK.
Launch the downloaded file.
Follow the prompts.
There are two versions of installation for Linux: a self-extracting binary file, and a binary file containing RPM packages.
Copy the file to the directory where you want to install Java.
Grant the file execute privileges:
chmod a+x filename.bin
Execute the file:
./filename.bin
Follow the onscreen instructions.
RPM files, which are primarily used on Red Hat Linux, contain detailed installation instructions. RPM files are very easy to install and require little user interaction.
chmod a+x filename.rpm.bin
./filename.rpm.bin
The result of this execution is the creation of a .rpm file. Execute the .rpm file as follows:
rpm -iv filename.rpm | https://flylib.com/books/en/1.89.1.17/1/ | CC-MAIN-2020-10 | refinedweb | 370 | 58.08 |
Hi All, O.K. I'm new to swift and apple. I've worked in C and Tcl/Tk. What I'm trying to do is run an executable on MacOS from swift. Specifically aescrypt. I've played with Process and task.esecutableURL but they all seem to fail. Any hints. Thanks
I'm guessing you tried to use the path to your executable for
executableURL, while it should be the path to the shell.
Something like this works for me:
import Foundation let process = Process() let pipe = Pipe() process.standardOutput = pipe // you can also set stderr and stdin process.executableURL = URL(fileURLWithPath: "/bin/bash") // or any other shell you like process.arguments = ["-c", "the command you use to run your executable normally"] try! process.run() // process.waitUntilExit() // you might need this let data = pipe.fileHandleForReading.readDataToEndOfFile() guard let standardOutput = String(data: data, encoding: .utf8) else { FileHandle.standardError.write(Data("Error in reading standard output data".utf8)) fatalError() // or exit(EXIT_FAILURE) and equivalent // or, you might want to handle it in some other way instead of a crash }
In addition, you can wrap the whole thing in a function like this:
/// Executes a shell command with `/bin/bash`. /// - Parameter command: The command to execute. /// - Returns: The standard output from executing `command`. @discardableResult func bash(_ command: String) -> String { ... }
and then call it like this:
bash("the command you use to run your executable normally") // or let standardOutput = bash("the command you use to run your executable normally")
Thank you. I now have it working for what I wanted, and your explanation was the key !
// Thanks again wow bagger, you example/suggestion brought me to this code below.
// This is what worked for me to run command aescrypt. put together from several sources
// below now works**
import Foundation
func executeCommand(command: String, args: [String]) -> String {
let task = Process()
task.launchPath = command
task.arguments = args
let pipe = Pipe()
task.standardOutput = pipe
task.launch()
let data = pipe.fileHandleForReading.readDataToEndOfFile()
let output: String = String(decoding: data, as: UTF8.self)
return output
}
let commandOutput = executeCommand(command:"/bin/bash",args: ["-c", "exec /usr/local/bin/aescrypt -k /Users/usr/.secret.key -e /Users/usr/test.swift"])** | https://forums.swift.org/t/running-launching-an-existing-executable-program-from-swift-on-macos/47653 | CC-MAIN-2021-31 | refinedweb | 360 | 52.87 |
Overview
-!
Introduction
“Hey Google. What’s the weather like today?”
This will sound familiar to anyone who has owned a smartphone in the last decade. I can’t remember the last time I took the time to type out the entire query on Google Search. I simply ask the question – and Google lays out the entire weather pattern for me.
It saves me a ton of time and I can quickly glance at my screen and get back to work. A win-win for everyone! But how does Google understand what I’m saying? And how does Google’s system convert my query into text on my phone’s screen?
This is where the beauty of speech-to-text models comes in. Google uses a mix of deep learning and Natural Language Processing (NLP) techniques to parse through our query, retrieve the answer and present it in the form of both audio and text.
The same speech-to-text concept is used in all the other popular speech recognition technologies out there, such as Amazon’s Alexa, Apple’s Siri, and so on. The semantics might vary from company to company, but the overall idea remains the same.
I have personally researched quite a bit on this topic as I wanted to understand how I could build my own speech-to-text model using my Python and deep learning skills. It’s a fascinating concept and one I wanted to share with all of you.
So in this article, I will walk you through the basics of speech recognition systems (AKA an introduction to signal processing). We will then use this as the core when we implement our own speech-to-text model from scratch in Python.
Looking for a place to start your deep learning and/or NLP journey? We’ve got the perfect resources for you:
Table of Contents
- A Brief History of Speech Recognition through the Decades
- Introduction to Signal Processing
- Different Feature Extraction Techniques from an Audio Signal
- Understanding the Problem Statement for our Speech-to-Text Project
- Implementing the Speech-to-Text Model in Python
A Brief History of Speech Recognition through the Decades
You must be quite familiar with speech recognition systems. They are ubiquitous these days – from Apple’s Siri to Google Assistant. These are all new advents though brought about by rapid advancements in technology.
Did you know that the exploration of speech recognition goes way back to the 1950s? That’s right – these systems have been around for over 50 years! We have prepared a neat illustrated timeline for you to quickly understand how Speech Recognition systems have evolved over the decades:
- The first speech recognition system, Audrey, was developed back in 1952 by three Bell Labs researchers. Audrey was designed to recognize only digits
- Just after 10 years, IBM introduced its first speech recognition system IBM Shoebox, which was capable of recognizing 16 words including digits. It could identify commands like “Five plus three plus eight plus six plus four minus nine, total,” and would print out the correct answer, i.e., 17
- The Defense Advanced Research Projects Agency (DARPA) contributed a lot to speech recognition technology during the 1970s. DARPA funded for around 5 years from 1971-76 to a program called Speech Understanding Research and finally, Harpy was developed which was able to recognize 1011 words. It was quite a big achievement at that time.
-.
Wouldn’t it be great if we can also work on such great use cases using our machine learning skills? That’s exactly what we will be doing in this tutorial!
Introduction to Signal Processing
Before we dive into the practical aspect of speech-to-text systems, I strongly recommend reading up on the basics of signal processing first. This will enable you to understand how the Python code works and make you a better NLP and deep learning professional!
So, let us first understand some common terms and parameters of a signal.
What is an Audio Signal?
This is pretty intuitive – any object that vibrates produces sound waves. Have you ever thought of how we are able to hear someone’s voice? It is due to the audio waves. Let’s quickly understand the process behind it.
When an object vibrates, the air molecules oscillate to and fro from their rest position and transmits its energy to neighboring molecules. This results in the transmission of energy from one molecule to another which in turn produces a sound wave.
Parameters of an audio signal
- Amplitude: Amplitude refers to the maximum displacement of the air molecules from the rest position
- Crest and Trough: The crest is the highest point in the wave whereas trough is the lowest point
- Wavelength: The distance between 2 successive crests or troughs is known as a wavelength
- Cycle: Every audio signal traverses in the form of cycles. One complete upward movement and downward movement of the signal form a cycle
- Frequency: Frequency refers to how fast a signal is changing over a period of time
The below GIF wonderfully depicts the difference between a high and low-frequency signal:
In the next section, I will discuss different types of signals that we encounter in our daily life.
Different types of signals
We come across broadly two different types of signals in our day-to-day life – Digital and Analog.
Digital signal
A digital signal is a discrete representation of a signal over a period of time. Here, the finite number of samples exists between any two-time intervals.
For example, the batting average of top and middle-order batsmen year-wise forms a digital signal since it results in a finite number of samples.
Analog signal
An analog signal is a continuous representation of a signal over a period of time. In an analog signal, an infinite number of samples exist between any two-time intervals.
For example, an audio signal is an analog one since it is a continuous representation of the signal.
Wondering how we are going to store the audio signal since it has an infinite number of samples? Sit back and relax! We will touch on that concept in the next section.
What is sampling the signal and why is it required?
An audio signal is a continuous representation of amplitude as it varies with time. Here, time can even be in picoseconds. That is why an audio signal is an analog signal.
Analog signals are memory hogging since they have an infinite number of samples and processing them is highly computationally demanding. Therefore, we need a technique to convert analog signals to digital signals so that we can work with them easily.
Sampling the signal is a process of converting an analog signal to a digital signal by selecting a certain number of samples per second from the analog signal. Can you see what we are doing here? We are converting an audio signal to a discrete signal through sampling so that it can be stored and processed efficiently in memory.
I really like the below illustration. It depicts how the analog audio signal is discretized and stored in the memory:
The key thing to take away from the above figure is that we are able to reconstruct an almost similar audio wave even after sampling the analog signal since I have chosen a high sampling rate. The sampling rate or sampling frequency is defined as the number of samples selected per second.
Different Feature Extraction Techniques for an Audio Signal
The first step in speech recognition is to extract the features from an audio signal which we will input to our model later. So now, l will walk you through the different ways of extracting features from the audio signal.
Time-domain
Here, the audio signal is represented by the amplitude as a function of time. In simple words, it is a plot between amplitude and time. The features are the amplitudes which are recorded at different time intervals.
The limitation of the time-domain analysis is that it completely ignores the information about the rate of the signal which is addressed by the frequency domain analysis. So let’s discuss that in the next section.
Frequency domain
In the frequency domain, the audio signal is represented by amplitude as a function of frequency. Simply put – it is a plot between frequency and amplitude. The features are the amplitudes recorded at different frequencies.
The limitation of this frequency domain analysis is that it completely ignores the order or sequence of the signal which is addressed by time-domain analysis.
Remember:
Time-domain analysis completely ignores the frequency component whereas frequency domain analysis pays no attention to the time component.
We can get the time-dependent frequencies with the help of a spectrogram.
Spectrogram
Ever heard of a spectrogram? It’s a 2D plot between time and frequency where each point in the plot represents the amplitude of a particular frequency at a particular time in terms of intensity of color. In simple terms, the spectrogram is a spectrum (broad range of colors) of frequencies as it varies with time.
The right features to extract from audio depends on the use case we are working with. It’s finally time to get our hands dirty and fire up our Jupyter Notebook!
Understanding the Problem Statement for our Speech-to-Text Project
Let’s understand the problem statement of our project before we move into the implementation part.
We might be on the verge of having too many screens around us. It seems like every day, new versions of common objects are “re-invented” with built-in wifi and bright touchscreens. A promising antidote to our screen addiction is voice interfaces.
TensorFlow recently released the Speech Commands Datasets. It includes 65,000 one-second long utterances of 30 short words, by thousands of different people. We’ll build a speech recognition system that understands simple spoken commands.
You can download the dataset from here.
Implementing the Speech-to-Text Model in Python
The wait is over! It’s time to build our own Speech-to-Text model from scratch.
Import the libraries
First, import all the necessary libraries into our notebook. LibROSA and SciPy are the Python libraries used for processing audio signals.
Data Exploration and Visualization
Data Exploration and Visualization helps us to understand the data as well as pre-processing steps in a better way.
Visualization of Audio signal in time series domain
Now, we’ll visualize the audio signal in the time series domain:
Sampling rate
Let us now look at the sampling rate of the audio signals:
ipd.Audio(samples, rate=sample_rate) print(sample_rate)
Resampling
From the above, we can understand that the sampling rate of the signal is 16,000 Hz. Let us re-sample it to 8000 Hz since most of the speech-related frequencies are present at 8000 Hz:
samples = librosa.resample(samples, sample_rate, 8000) ipd.Audio(samples, rate=8000)
Now, let’s understand the number of recordings for each voice command:
Duration of recordings
What’s next? A look at the distribution of the duration of recordings:
Preprocessing the audio waves
In the data exploration part earlier, we have seen that the duration of a few recordings is less than 1 second and the sampling rate is too high. So, let us read the audio waves and use the below-preprocessing steps to deal with this.
Here are the two steps we’ll follow:
- Resampling
- Removing shorter commands of less than 1 second
Let us define these preprocessing steps in the below code snippet:
Convert the output labels to integer encoded:
Now, convert the integer encoded labels to a one-hot vector since it is a multi-classification problem:
from keras.utils import np_utils y=np_utils.to_categorical(y, num_classes=len(labels))
Reshape the 2D array to 3D since the input to the conv1d must be a 3D array:
all_wave = np.array(all_wave).reshape(-1,8000,1)
Split into train and validation set
Next, we will train the model on 80% of the data and validate on the remaining 20%:
from sklearn.model_selection import train_test_split x_tr, x_val, y_tr, y_val = train_test_split(np.array(all_wave),np.array(y),stratify=y,test_size = 0.2,random_state=777,shuffle=True)
Model Architecture for this problem
We will build the speech-to-text model using conv1d. Conv1d is a convolutional neural network which performs the convolution along only one dimension.
Here is the model architecture:
Model building
Let us implement the model using Keras functional API.
Define the loss function to be categorical cross-entropy since it is a multi-classification problem:
model.compile(loss='categorical_crossentropy',optimizer='adam',metrics=['accuracy'])
Early stopping and model checkpoints are the callbacks to stop training the neural network at the right time and to save the best model after every epoch:
es = EarlyStopping(monitor='val_loss', mode='min', verbose=1, patience=10, min_delta=0.0001) mc = ModelCheckpoint('best_model.hdf5', monitor='val_acc', verbose=1, save_best_only=True, mode='max')
Let us train the model on a batch size of 32 and evaluate the performance on the holdout set:
history=model.fit(x_tr, y_tr ,epochs=100, callbacks=[es,mc], batch_size=32, validation_data=(x_val,y_val))
Diagnostic plot
I’m going to lean on visualization again to understand the performance of the model over a period of time:
from keras.models import load_model model=load_model('best_model.hdf5')
Define the function that predicts text for the given audio:
Prediction time! Make predictions on the validation data:
The best part is yet to come! Here is a script that prompts a user to record voice commands. Record your own voice commands and test it on the model:
Let us now read the saved voice command and convert it to text:
Here is an awesome video that I tested on one of my colleague’s voice commands:
Congratulations! You have just built your very own speech-to-text model!
Code
End Notes
Got to love the power of deep learning and NLP. This is a microcosm of the things we can do with deep learning. I encourage you to try it out and share the results with our community. 🙂
In this article, we covered all the concepts and implemented our own speech recognition system from scratch in Python.
I hope you have learned something new today. I will see you in the next article. If you have any queries/feedback, please free to share in the below comments section!You can also read this article on our Mobile APP
3 Comments
That was quite nice, but you should have warned the speech recognition beginner that speech recognition and understanding goes a long way beyond small vocabulary isolated word recognition. Perhaps your next instalments could look at medium vocabulary continuous speech recognition, then robust open vocabulary continuous speech recognition, then start combining that with get into NLP. However, I expect python could run into problems doing that kind of thing in real-time. Perhaps that’s one reason why you decided to downsample from 16 to 8 kHz, when 16 kHz is known to be more accurate for speech recognition.
Hi Andrew,
Thanks. I completely agree with you. The next task would be to build a continuous speech recognition for medium vocabulary. However, the article was designed by keeping beginners in mind.
This is a wonderful learning opportunity for anyone starting to learn NLP and ML. Unfortunately, the kernel keeps crashing. Gotta fix my environment. Thanks Aravind for the good start. | https://www.analyticsvidhya.com/blog/2019/07/learn-build-first-speech-to-text-model-python/ | CC-MAIN-2020-29 | refinedweb | 2,573 | 54.02 |
Customize Your jQuery Mobile Interface with Specialized Plugins
JavaScript libraries like jQuery Mobile can help you develop mobile apps rapidly, but your results often have a generic feel that leaves your apps resembling many other jQuery Mobile apps. If you want your mobile development work to stand apart, you may have to deviate from the standard jQuery Mobile library and employ plugins or other forms of customization.
In this article, I’ll demonstrate one of these specialized plugins—Audero Text Changer, a jQuery Mobile plugin that I designed to solve a common problem that developers encounter while working with the jQuery Mobile framework. As you might know, the links in jQuery Mobile are rendered as buttons, but they aren’t actually buttons from a technical standpoint. For this reason, the button widget doesn’t apply to them. Suppose you want to change several elements’ text in one of your mobile layouts, including some of these links. Since the links aren’t buttons, you can’t change the text directly inside them and use the method
button('refresh') to redraw the button, because you’ll get an error. So, to regain control of your mobile link labeling, you can rely on Audero Text Changer.
As you’ll see in a few moments, Audero Text Changer is very simple and lightweight. In fact, the minimized version is less than 1kb, but it allows you to easily change the text of all the elements of your mobile page layouts without breaking the enhancements of the mobile framework. It also has very high backward compatibility, since it’ll work on jQuery Mobile version starting as far back as 1.0.1.
Let’s now dive into the code.
The Basics
Since I like to code “the right way” and illustrate best practices, the plugin will use the jQuery plugin suggested guidelines. Explaining how to build a jQuery plugin, or from another point of view, rearranging the content of the linked page, is outside the scope of this article, so I’ll give you just a brief overview. I’ll use an IIFE so the plugin won’t collide with other libraries that use the dollar sign as an abbreviation. As suggested by the guidelines, I’ll also use namespacing so that the plugin will have lower chances of being overwritten by other libraries loaded by the same page. As you can guess from the plugin name, the chosen namespace is
auderoTextChanger. At line 2 of the next snippet, I added the namespace as a property of the
$.fn object. To make sure that I don’t overload the
$.fn object, instead of adding every method to it, I’ll write them inside an object literal. In this way, you can call the plugin’s methods by passing the method’s name as a string.
Please note that the plugin needs just one method, to serve its purpose of changing the text of layout elements. Its only parameter is a string that represents the text to write. As you can see, line 5 of the listed code is slightly different compared to the guidelines, because I added the test
typeof method === 'string'. In this way, you can simply call the plugin by passing a raw string instead of wrapping the latter in an object literal.
(function($){ $.fn.auderoTextChanger = function(method) { if (methods[method]) return methods[method].apply(this, Array.prototype.slice.call(arguments, 1)); else if (typeof method === 'object' || typeof method === 'string' || !method) return methods.init.apply(this, arguments); else $.error('Method ' + method + ' does not exist on jQuery.auderoTextChanger'); }; })(jQuery);
Getting Started
As I pointed out in the introduction, you don’t have to worry about the elements’ type given to the plugin, because it will manage them for you. When jQuery Mobile applies its code enhancements, it adds several elements to the DOM and, based on the type of the element, adds different elements (like
<span> and
<div>) in different elements’ positions (sometimes as parent element, other times as a child). This fact leads the text of many elements to be moved from their original position or to be copied into other elements. For example, if the enhanced tag is a
<button>, jQuery Mobile wraps it in a
<div>. Moreover, it adds a child element
<span> that has yet another
<span>,which actually contains the desired text. I know it can be a little complex, but this is the way the framework works. Thus, based on the type of the element, our plugin has to search for the right element to replace the text. Take a look at the code below.
var methods = { init: function(text) { return this.each(function() { if ($(this).is('a')) $(this).find('.ui-btn-text').attr('title', text).text(text); else if ($(this).is('button, input[type="submit"], input[type="reset"]')) $(this).closest('.ui-btn').find('.ui-btn-text').text(text); else $(this).text(text); }); } };
Let’s explain the above function. If the element is a link, the plugin changes its title attribute and the text of its inner element having
class="ui-btn-text". That is the element where jQuery Mobile has put the link’s display text. If the element is a true button or an input having type submit or reset, the text isn’t a child of these elements, but a child within a child element.
How to Use the Plugin
Using this plugin is very simple. Just call the
auderoTextChanger() method on the element(s) that you want to modify by changing their display text. You don’t need to worry about the type of the elements, the plugin will manage that part of the process for you. Suppose that you have the following code:
<div id="box"> <a href="#" id="info-button" data-Info</a> <button id="demo-button">Button</button> <input id="reset-button" type="reset" value="Reset" /> <input id="submit-button" type="submit" value="Submit" /> </div>
A basic call to the plugin is:
<script> $(document).on( 'pageinit', function () { $('#info-button').auderoTextChanger('About...'); $('#demo-button').auderoTextChanger('A Private Text'); $('#box input').auderoTextChanger('A New Text!'); } ); </script>
Conclusion
As you’ve seen in this article, the problem of keeping control over your interface content without breaking the jQuery Mobile framework can be easily solved with few useful lines of jQuery Mobile plugin code. Feel free to use Audero Text Changer in your projects as you like since I released it dual licensed under the MIT and GPL-3.0 licenses. You can download the plugin through my repository to study the whole code or download the minified version.
No Reader comments | http://www.sitepoint.com/how-to-change-texts-in-your-jquery-mobile-apps-without-breaking-widgets/ | CC-MAIN-2015-11 | refinedweb | 1,097 | 62.58 |
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wikiHow to Work out the Payback Period
The "payback period" is an accounting metric used for investment decision making. The metric is very simple, and is designed to estimate how quickly a company will recover a cash investment. When used alone, the payback period can be misleading and oversimplified. However, when analyzed alongside other decision-making metrics, the payback period can be clarifying and helpful. Learning how to work out the payback period for a particular investment or project is a matter of estimating a few cash flows and performing a simple calculation.
Steps
- 1Familiarize yourself with the basic computation of the payback period. The payback period specifies how quickly (in years) the cash invested in a particular project will be recovered. For example, consider a project that requires a $100,000 cash outflow immediately, but is expected to bring in an additional $10,000 in cash each year for 20 years. The payback period is 10 years, because after 10 years the original cash outflow has been recovered ($10,000 * 10 = $100,000).
- Note that the payback period calculation does not take the time value of money into account. Future cash flows are not discounted to their present values, but are instead used at face value.
- Note also that the payback period only considers cash flows, and does not take into account the effect of depreciation or other non-cash expenses. This, along with the time value exclusion, is a shortcoming of the payback calculation.
- 2Assess the immediate cash outflow associated with the project in question. This is the amount that must be paid out in cash at the start of a project.
- For example, consider a company's decision to buy a new copy machine to replace an old one. The machine costs $10,000, and is expected to save $1000 in toner and electricity each year for 8 years, and then save $800 each year for the next 10 years. The immediate cash outflow associated with this project is $10,000.
- 3Assess the future cash flows expected from a project. These cash flows should be estimated before undertaking any project. Before calculating the payback period, it helps to write these cash flows down on paper in timeline form. In the example above, there are 8 cash flows of $1000, followed by 10 cash flows of $800.
- 4Sum together the future cash flows until you recover the initial cash investment. Begin adding the cash flows together in chronological order. When the sum is equal to the initial outflow, you have found the payback period.
- In the example above, after 1 year the company has recovered $1000. After 5 years, the company has recovered $5000. After 8 years, $8000 has been recovered. After 10 years, $9600 has been recovered. After 11 years, $10,400 has been recovered; this amount exceeds the initial investment, so the payback period must be between 10 and 11 years.
- The cash flow in year 11 was $800. After $400 of this cash was received, the initial investment of $10,000 had been recovered. This is exactly half of that year's cash flow, so the payback period for this investment is 10.5 years.
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Tips
- The sample calculations above will also work when expressed in other currencies.
- The payback period should always be used in conjunction with other decision-making metrics, such as return on investment (ROI) and internal rate of return (IRR).
Things You'll Need
- Pencil
- Paper
Article Info
Categories: Credit and Debt
Thanks to all authors for creating a page that has been read 14,395 times.
Did this article help you? | http://www.wikihow.com/Work-out-the-Payback-Period | CC-MAIN-2017-04 | refinedweb | 631 | 63.49 |
This example shows you how you can persist objects across requests in the session object.
As was discussed previously , instances
of Session last as long as
the notional session itself does. Each time Request.getSession is called, if the session
for the request is still active, then the same
Session instance is
returned as was returned previously. Because of this,
Session
instances can be used to keep other objects around for as long as the session
exists.
It’s easier to demonstrate how this works than explain it, so here’s an example:
>>> from zope.interface import Interface, Attribute, implements >>> from twisted.python.components import registerAdapter >>> from twisted.web.server import Session >>> class ICounter(Interface): ... value = Attribute("An int value which counts up once per page view.") ... >>> class Counter(object): ... implements(ICounter) ... def __init__(self, session): ... self.value = 0 ... >>> registerAdapter(Counter, Session, ICounter) >>> ses = Session(None, None) >>> data = ICounter(ses) >>> print data <__main__.Counter object at 0x8d535ec> >>> print data is ICounter(ses) True >>>
What? , I hear you say.
What’s shown in this example is the interface and adaption-based
API which
Session exposes for persisting state. There are
several critical pieces interacting here:
ICounteris an interface which serves several purposes. Like all interfaces, it documents the API of some class of objects (in this case, just the
valueattribute). It also serves as a key into what is basically a dictionary within the session object: the interface is used to store or retrieve a value on the session (the
Counterinstance, in this case).
Counteris the class which actually holds the session data in this example. It implements
ICounter(again, mostly for documentation purposes). It also has a
valueattribute, as the interface declared.
ICounter(ses). This is read as : adapt
sesto
ICounter. Because of the
registerAdaptercall, it is roughly equivalent to
Counter(ses). However (because of certain things
Sessiondoes), it also saves the
Counterinstance created so that it will be returned the next time this adaption is done. This is why the last statement produces
True.
If you’re still not clear on some of the details there, don’t worry about it
and just remember this:
ICounter(ses) gives you an object you can
persist state on. It can be as much or as little state as you want, and you can
use as few or as many different
Interface classes as you want on a
single
Session instance.
With those conceptual dependencies out of the way, it’s a very short step to actually getting persistent state into a Twisted Web application. Here’s an example which implements a simple counter, re-using the definitions from the example above:
from twisted.web.resource import Resource class CounterResource(Resource): def render_GET(self, request): session = request.getSession() counter = ICounter(session) counter.value += 1 return "Visit #%d for you!" % (counter.value,)
Pretty simple from this side, eh? All this does is
use
Request.getSession and the adaption from above, plus some
integer math to give you a session-based visit counter.
Here’s the complete source for an rpy script based on this example:
cache() from zope.interface import Interface, Attribute, implements from twisted.python.components import registerAdapter from twisted.web.server import Session from twisted.web.resource import Resource class ICounter(Interface): value = Attribute("An int value which counts up once per page view.") class Counter(object): implements(ICounter) def __init__(self, session): self.value = 0 registerAdapter(Counter, Session, ICounter) class CounterResource(Resource): def render_GET(self, request): session = request.getSession() counter = ICounter(session) counter.value += 1 return "Visit #%d for you!" % (counter.value,) resource = CounterResource()
One more thing to note is the
cache() call at the top
of this example. As with the previous example where this came up, this rpy script is stateful. This
time, it’s the
ICounter definition and
the
registerAdapter call that need to be executed only
once. If we didn’t use
cache , every request would define
a new, different interface named
ICounter . Each of these
would be a different key in the session, so the counter would never
get past one. | http://twistedmatrix.com/documents/current/web/howto/web-in-60/session-store.html | CC-MAIN-2016-22 | refinedweb | 676 | 50.33 |
If you are interested in creating your own chat robot, then here is a tutorial on how to do it yourself by using Java and AIML.
A chat robot or chatterbot is a human chat simulator. It is a program for auditory or textual conversation between a computer and a human being. Such robots are used for fun, education and 24×7 customer services. When students and customers have many questions to ask, the robot gives the answers on behalf of teachers or customer service executives.
In this article, I have used AIML, A.L.I.C.E, Java and NetBeans. A brief introduction to these technologies follows.
AIML (Artificial Intelligent Markup Language) is an XML based mark-up language to help create a chat robot from scratch. It was first developed by Dr Richard Wallace when he created a chat robot named A.L.I.C.E (Artificial Linguistic Internet Computer Entity).
The important tags for AIML are listed below.
- <aiml>: The parent tag to start and end the AIML document.
- <category>: Every new question or pattern with its relevant answer goes in this tag.
- <pattern>: Matches the pattern with the user’s question.
- <template>: The robot gives the answer from the template if the pattern can be matched.
<?xml version = “1.0” encoding = “UTF-8” ?> <aiml version = “1.0.1” encoding = “UTF-8”?> <category> <pattern> What is your name? </pattern> <template> I am Alice, nice to meet you. </template> </category> </aiml>
Here is an explanation of the code given above. File first.aiml contains the XML based tag for the robot’s knowledge. Here, the <category> tag is used to describe the user pattern or the user’s question. <template> is the response given by the robot to the user if the user’s pattern is matched.
A.L.I.C.E is the robot created in 1995 by Dr Richard Wallace, in Java, by using AIML. We can also say that A.L.I.C.E is an AIML parser. Nowadays, many parsers are available in various languages like PHP, Python, etc.
Steps to creating a chat robot
1. Download the source code from
2. Go to the Java section.
3. Download the source code under the link Chatterbean.
4. Under the section ‘Download, Building and Usage Information’, go to ‘Download Chatterbean 00.008 Source Distribution’. We will download the source code rather than the binary distribution.
5. Extract Chatterbean to the folder (Figure 2).
This extracted folder contains the ‘Bot’ directory, which will have the collection of AIML. We can create our own AIML to increase the knowledge of our robot. But first let’s proceed to the set-up. The folder ‘Source’ contains Java code for the robot A.L.I.C.E and the AIML parser. We will use this, as it is, in our program.
Preparing NetBeans for coding
The following steps prepare NetBeans for coding.
1. Create a project named ‘myChatBot’.
2. Copy the existing source code of A.L.I.C.E into our Project folder. Copy botoflife from the downloaded source code to NetbeansProject/mychatbot/src as shown in Figure 4.
The source code will appear in the Projects tab under Source Packages at the NetBeans IDE shown in Figure 5.
3. Now copy the Bot folder from the downloaded source code to NetbeansProject/myChatBot as shown in Figure 6.
4. Add additional supportive libraries which come with the A.L.I.C.E source code. These are bsh.jar and junit.jar.
The set-up is now ready. Open MyChatBot.java which contains main() and import the libraries, using the following code:
import bitoflife.chatterbean.AliceBotMother; import bitoflife.chatterbean.AliceBot; public static void main(String[] str) { try{ AliceBotMother mother = new AliceBotMother(); AliceBot mybot = mother.newInstance(); String ask = “Who are you?”; //Here You can ask Dynamic question. String str = mybot.respond(ask); System.out.println(str); } catch(Exception ex) { System.err.println(ex.toString()); }
Execute the code. It will generate the answer shown in Figure 8.
In the above code, in the first two lines, the AliceBotMother and AliceBot class create the instance of Bot. Now, ask a meaningful question; in our case, it’s String ask. Now pass this string to object AliceBot with the respond function, which returns the string answer predefined in the relevant AIML. We can ask various questions by replacing the string in ask variable.
Your own, personal robot is now ready! As it’s a Java based application, you can use it on various platforms.
Connect With Us | http://opensourceforu.com/2017/01/create-your-own-java-based-chat-robot/ | CC-MAIN-2017-04 | refinedweb | 754 | 61.83 |
Thank you both for the answers
> def union( > name: str, types: Tuple[Types, ...], * > ) -> Union[Types]: > # implementation is not important > return None # type: ignore > ```
I think the (non) implementation as shown is confusing. You surely don't actually return None? What do you do with the name, just ignore it?
The implementation returns an instance of a custom defined union class, which holds the information about the types and the name.
I think a better implementation would be to return Annotated[Union[*Types], Something(name="passed name")], but that would have the same issue I'm having now, since I'm passing through a function call.
I think I can ask my users to use Annotated directly 😊
My goal with a custom union function was ease of use, I wanted something that didn't require to learn new concepted (Annotated) and it was easier to type:
```python UserOrError = strawberry.union((User, Error), "UserOrError")] # vs UserOrError = Annotated[User|Error, strawberry.union("UserOrError")] ```
but maybe Annotated doesn't look too bad, especially with the new union syntax 😊
Thanks Steven and Eric!
On Sat, 11 Jun 2022 at 00:48, Steven D'Aprano steve@pearwood.info wrote:
Hi Patrick,
On Fri, Jun 10, 2022 at 12:42:16PM -0000, Patrick Arminio wrote:
def union( name: str, types: Tuple[Types, ...], * ) -> Union[Types]: # implementation is not important return None # type: ignore
I think the (non) implementation as shown is confusing. You surely don't actually return None? What do you do with the name, just ignore it?
If you ignore the name, then it is hard for me to see why you need this union function at all.
UserOrError = User|Error # Or if you need to annotate it with additional information: UserOrError = Annotated[User|Error, "UserOrError"]
As Eric explains in another post, it is unlikely that static (compile-time) type checkers will support the evaluation and tracking of arbitrary types generated at runtime.
Unfortunately subscripting syntax does not allow keyword arguments, so you cannot associate your annotation with a parameter name:
# This is a syntax error. Annotated[User|Error, name="UserOrError"]
See rejected PEP 637.
-- Steve _______________________________________________ Typing-sig mailing list -- typing-sig@python.org To unsubscribe send an email to typing-sig-leave@python.org Member address: patrick.arminio@gmail.com | https://mail.python.org/archives/list/typing-sig@python.org/message/L2W44M5FOJU62S4PJV65F2SPYJ24LP3P/ | CC-MAIN-2022-40 | refinedweb | 376 | 55.44 |
NAME
vm_page_io_start, vm_page_io_finish — ready or unready a page for I/O
SYNOPSIS
#include <sys/param.h> #include <vm/vm.h> #include <vm/vm_page.h> void vm_page_io_start(vm_page_t m); void vm_page_io_finish(vm_page_t m);
DESCRIPTION
The vm_page_io_start() function prepares the page for I/O by incrementing its busy flag by one. The vm_page_io_finish() function lowers the busy count on the page by one, if the resulting busy count is zero, a wakeup(9) will be issued if the page has been marked VPO_WANTED. A page is typically marked VPO_WANTED by a thread to register its interest in the page to either complete I/O or becoming available for general use.
AUTHORS
This manual page was written by Chad David ⟨davidc@acns.ab.ca⟩ and Alfred Perlstein ⟨alfred@FreeBSD.org⟩. | http://manpages.ubuntu.com/manpages/precise/man9/vm_page_io.9freebsd.html | CC-MAIN-2016-18 | refinedweb | 127 | 57.47 |
The first thing that we're going to look into is the NumericTextBox. We do have a DropdownList first, but we already added the data for that list already.
Our NumericTextBox is not looking exactly how we want it to. Out of the box, there is no restriction on what numbers can be used, including negative numbers and decimals. We can't eat a negative amount of fruit and vegetables. As many times as I want to only halfway do my tasks, we don't want the value to be a decimal. This value will become a set of radio buttons for each habit that we create, so this value needs to be a whole number.
The first thing we need to do is formatting. To set the format to not allow decimals, we set a prop input ( format ) to 0. There are other formats to choose from. For instance, you can add C to format the input as currency. 0 is all we need.
format
0
<NumericTextBox format="0"/>
In the documentation for the NumericTextBox, there are all the different format types that you can explore. There's also an API that you can go through and check all the ways you can customize this input.
Next, we need to set min to zero so that our users cannot input any negative numbers, and just for the heck of it, we'll also set max to 22.
min
max
<NumericTextBox
format='0'
min={0}
max={22}
/>
Now that we have the NumericTextBox set up, let's run the app. With the built-in keyboard navigation, we can raise or lower the amount with the arrow keys so long as the number is between 1 and 22.
Next, we want to be able to click the add button and create a new habit. In order to make this work, we will need to add event listeners to our inputs and button to call handlers that will update our application, in turn creating a list of healthy habits.
Before we do that, let's add some information to our state: habitName, habitId, habitIteration and an array of habits. Our state object needs to be updated as follows:
habitName
habitId
habitIteration
habits
this.state = {
data: nutrition,
habitId: 0,
habitName: '',
habitIteration: 0,
habits: [],
habitsOptions: [
'Drink 1 cup of water',
'1 Hour of Coding',
'10 pushups',
'Eat Your Fruits and veggies',
'1 hour of Reading',
'10 minutes of Meditation',
]
}
So we added a habitName with an empty string (intentionally left blank), and a habitId set to 0. We're using this to set a key that we need for every list item. Then we added a habitIteration with an initial state of zero. Finally, we add a habits field initializing as an empty array.
habitName
habitId
0
Remember, we are just prototyping. Understand that keeping all of our state inside the App.js file and updating state manually is definitely not something you want to do in a scalable production app, but my intention is to teach you the Kendo controls, not build a solid production web application. Just remember that in a real-world web app, you would want to incorporate a state management strategy and/or make our application modular by breaking the UI and logic up into many services, containers and presentational components.
App.js
Next, onto our handler functions. We will make a handleNameChange function, which takes the event from DropDownList as an argument. When this function is triggered we setState() to change our habit name. We'll set it to event.target.value . We're going to be doing the same with handleIterationChange(). Copy the code for the handlers below into your App.js file just underneath the constructor.
handleNameChange
setState()
event.target.value
handleIterationChange()
handleNameChange = (event) => {
this.setState({ habitName: event.target.value })
}
handleIterationChange = (event) => {
this.setState({ habitIteration: event.target.value })
}
Now that we have the handler functions for our event listeners, we can add the change listener to the dropdown list, and numeric text box as well the onClick event that will capture our form submission to add a habit. I also want to add a primary class to the button to make it pop on the page a little more (setting primary={true}). With these changes, anytime there's a change in the inputs, it should be immediately reflected in the state, which in turn will update our component. Let's update the inputs and button with these changes:
primary={true}
<DropDownList
data={this.state.habitsOptions}
value={this.state.habitName}
onChange={this.handleNameChange} />
<NumericTextBox
format='0'
min={0}
max={22}
value={this.state.habitIteration}
onChange={this.handleIterationChange} />
<Button primary={true}>
Add Habit
</Button>
We will also need a list of habits to add to as well as a handler for the button onClick event. Let's add an event listener to our button right after we implement a handleAddHabit() handler function.
onClick
handleAddHabit()
handleAddHabit = (event) => {
this.setState({
habits: this.state.habits.concat([{
key: this.state.habitId,
name: this.state.habitName,
iterations: this.state.habitIteration
}]),
habitId: this.habitId++
});
}
Since we have habits as an array, the first time we add a habit, it will simply add that habit to the array, but for each subsequent operation, we will want to concatenate the new habit being added with the previous habits already existing in the array. We are also adding an iterator as habitId so that each habit will have a unique key.
habits
We have an empty div tag at the top of our page with a heading that says "Healthy Things"—this is where we will put our list of healthy habits. Copy the code below and replace the empty contents of that div.
div
div
<ul key='all-habits'>
{this.state.habits.map((habit) => [
<li key={habit.key}>
<h3>{habit.name}</h3>
<div className='iterations-area'>
{[...Array(habit.iterations)].map((iteration, index) => {
return <input key={index}
})}
</div>
</li>
])}
</ul>
Now we should see our list populated with the information that the user put into our inputs and a radio button for however many times they want to do that habit. This way, they can check them off as they go. Below is a preview of what you should be seeing at this point:
The next thing we're going to do is work on making our grid not only look a little bit better, but also add some functionality by giving it the ability to filter. Since we have this never ending grid, we're going to set the height by adding the code below to the Grid tag. We save that, and now we no longer have the crazy long grid.
Grid
<Grid data={this.state.data} style={{ maxHeight: '500px' }}>
Now we'll be adding the filtering for our grid. If you recall, in the section where we installed the Grid and related dependencies, one of the packages we installed was a data query module. We installed this module for the specific purpose of filtering our data in our grid. You see, I was thinking ahead for ya! Like I said, it's already available to us through the kendo-data-query package, let's import it!
import { filterBy } from '@progress/kendo-data-query';
With that in place, we can create a constant right above our state initialization in the constructor. This will serve as an initial filter (default state of the filter), upon our application loading for the first time:
const initialFilter = {
logic: 'and',
filters: [{
field: 'Description',
operator: 'contains',
value: 'Apple'
}]
};
Everything we have setup in this initialFilter is something the user will have control over when they are interacting with our grid. The API, and more importantly examples for this, can be found on the Data Query Overview. But in short, we are specifying our logic to be and as opposed to or. field, (the data item field to which the filter operator is applied) will be Description (our first column in the grid), and our operator for comparison will be contains where the description value is "Apple".
initialFilter
and
or
field
While we are dabbling in the constructor, we also need to change the state.data assignment to come from a function that takes initialFilter as an argument returning a data set where initialFilter has already been applied to it. After making that change, our state object will look like this:
state.data
initialFilter
this.state = {
data: this.getNutrition(initialFilter),
filter: initialFilter,
habitId: 0,
habitName: '',
habitIteration: 0,
habits: [],
habitsOptions: [
'Drink 1 cup of water',
'1 Hour of Coding',
'10 pushups',
'Eat Your Fruits and veggies',
'1 hour of Reading',
'10 minutes of Meditation',
]
}
Considering we have introduced a new function that we have not yet created, let's do that now.
getNutrition = (filter) => filterBy(nutrition, filter);
That is enough to get the initial state of the grid working, but we also want the grid itself to be filterable through user interactions. To get this working, let's skip down to the actual <Grid> component in our JSX and set a few more things up. Update the <Grid> start tag to the following:
<Grid>
<Grid data={this.state.data} style={{maxheight: '500px'}}
filterable={true} filter={this.state.filter}
onFilterChange={this.handleFilterChange}>
Here we have set filterable to true enabling filtering for the component, filter which will point to state.filter , and we will also need a handler for the change event filterChange . Let's go ahead and set that up because after adding the code above, we now have an error.
filterable
true
filter
state.filter
filterChange
handleFilterChange = (event) => {
this.setState({
data: this.getNutrition(event.filter),
filter: event.filter
});
}
So if we take a look at our application, we now have a grid that has filter functionality. For instance, if we change Apple in our editable filter to Orange, we will see that change take effect immediately in our grid filtering on food descriptions that contain the word Orange.
Apple
Orange! | https://www.telerik.com/blogs/kendoreact-customizing-components | CC-MAIN-2019-04 | refinedweb | 1,648 | 63.8 |
C++ function templates are used to write generic functions. A generic function defines a family of functions which are defined using the same code but which can be parameterized by different types, and by some sorts of constant parameters.
The classic example is a max function which returns the greater of its two parameters :-
template<class T>
T max(T a, T b) {
return (a<b?a:b);
}
This function can be used for any pair of parameters of the same type provided that the < operator is defined for them.
Log in or register to write something here or to contact authors.
Need help? accounthelp@everything2.com | https://everything2.com/title/function+template | CC-MAIN-2017-47 | refinedweb | 107 | 59.64 |
#include <wx/scopedptr.h>
A scoped pointer template class.
It is the template version of the old-style scoped pointer macros.
Notice that objects of this class intentionally cannot be copied.
Constructor takes ownership of the pointer.
Destructor deletes the pointer.
Returns pointer to object or NULL.
Conversion to a boolean expression (in a variant which is not convertible to anything but a boolean expression).
If this class contains a valid pointer it will return true, if it contains a NULL pointer it will return false.
Returns a reference to the object.
If the internal pointer is NULL this method will cause an assert in debug mode.
Smart pointer member access.
Returns pointer to object.
If the internal pointer is NULL this method will cause an assert in debug mode.
Releases the current pointer and returns it.
Reset pointer to the value of ptr.
The previous pointer will be deleted.
Swaps pointers. | http://docs.wxwidgets.org/3.0/classwx_scoped_ptr_3_01_t_01_4.html | CC-MAIN-2018-34 | refinedweb | 152 | 70.5 |
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Release History
By product
Test Studio Run-Time 2012.21420
February 20, 2013
[Common/Framework]
Settings:
- Changed: SilverlightConnectTimeout is increased from 30 to 60 seconds. [Story #39373]
- Changed: ClientReadyTimeout is increased from 30 to 60 seconds. [Story #39373]
- Changed: ElementWaitTimeout is increased from 10 to 30 seconds. [Story #39373]
Firefox:
- Fixed FormatException in GetRectangle(). [Bug #172570]
Silverlight & WPF:
- Changed: VisualFind default wait on elements timeout is up to 30 seconds. [Story #39373]
WPF:
- Fixed possible InvalidOperationException on launching WPF application. [Bug #174140]
MbUnit:
- Fixed ThreadAbortException being thrown at the end of the test even if the test has been reported to pass. [Bug #174869, PITS #13863]
Keyboard:
- Fixed Shift key not being released case.
[Execution]
Execution:
- Fixed playback freezes on long test run in IE9. [Bug #168031, PITS #13036]
- Fixed taken memory keeps stacking up when test fails. [Bug #152668, PITS #10946]
- Fixed the memory used by the Telerik.TestStudio.exe process is not been released after a log run completes. [Bug #163683, PITS #12522]
- Fixed Caret (^) symbol only inserts host portion of Project BaseUrl into FrameInfo BaseUrl field. [Bug #173092, PITS #13649]
- Fixed FileUpload dialog handler throwing FormatException in Silverlight OOB. [Bug #172594, PITS #13601]
- Fixed Inherit parent data leads to wrong iteration index in a test as step execution scenario. [Bug #173799, PITS #13725]
- Fixed test list execution failing to load test doesn't point the user to the problematic test. [Bug #175091, PITS #13894]
- Fixed a WPF execution problem for specific apps changing the visual tree on click causing the next action to fail with FindElementException. [Bug 177700, PITS #14073]
- Fixed InvalidOperationException when selecting from HTML Select element by index. [Bug #40300, Portal Problem #40298]
- Fixed Dialog handle steps may timeout in Firefox if you use the default timeout of 5000ms. [Bug #164316]
- Fixed Runner throwing unhandled exception in case of corrupted data source. [Bug #175032]
- Fixed Runner hanging in case of test list with execution browser set as AspNetHost. [Bug #173042]
[Common (Standalone + VS)]
Activation:
- Fixed manual deactivation link used to point to an obsolete address. [Bug #39670]
Recording:
- Fixed recorder crashing with RunToHere against a customer Silverlight application. [Bug #172021, PITS #13563]
- Fixed customer WPF application crashing on recording. [Bug #173897, PITS #13744]
- Fixed Recording using IE 10 leaves the FileUploadPath field empty on Handle FileUpload dialog step. [Bug #171573, PITS #13526]
- Fixed Recorder fails to attach after using 'Run to Here' option in test recorded against specific Microsoft CRM application. [Bug #176251, PITS #14008]
- Fixed recording type text in wrong text box for Silverlight windowless app. [Bug #40324, #40192, Portal Problem #40326, #40283]
- Fixed Silverlight/WPF RadRichTextBox highlighting issues. [Bug #175398, PITS #13934]
- Fixed Problem recording tooltip verification in WPF. [Bug #176162, PITS #14003]
- Fixed possible adding multiple dialog handler steps during recording in IE 10. [Bug #171579]
- Fixed multiple select is not recorded in a HTML ListBox control, normal select is not always recorded. [Bug #174932]
- Fixed WPF highlighting doesn't work for a specific app. [Bug #40088]
Execution:
- NEW: Exposed new DialogTitle property for WPF Open and SafeFile dialog handling. [Bug #162927, #153257, PITS #12391, #10879]
- NEW: Exposed new WaitForNoMotionCheckInterval property for WPF and Silverlight actions and verifications. [Bug #173100]
- Fixed coded step faulure details are missing in the Step Debug Failure UI after quick execution. [Bug #174652, PITS #13830]
- Fixed recapture storyboard execution throwing ArgumentNullException, introduced with internal build 2012.2.1317. [Bug #40701]
Project Settings:
- Changed: Default SilverlightConnectTimeout is up from 10 to 30 seconds. [Story #39373]
- Changed: Default QuickExecution ClientReadyTimeout is up from 10 to 30 seconds. [Story #39373]
- Changed: Default QuickExecution ElementWaitTimeout is up from 10 to 30 seconds. [Story #39373]
- Changed: Check for update notification for internal builds is off by default. [Bug #39505]
Test Step Properties:
- Changed: Default WaitOnElementsTimeout for all step is up from 10 to 30 seconds. [Story #39373]
- Changed: Default Timeout for verifications acting as waits is increased from 10 to 30 seconds. [Story #39373]
Data Binding:
- Fixed unable to see the data on binding a test in case of a space in the Excel worksheet name or styles. [Bug #173916, PITS #13746]
- Fixed unhandled exception changing the verification's datasource of an IF step. [Bug #173444, PITS #13695]
Test Explorer:
- Fixed a possible unhandled exception in case of drag and drop "if" step beyond the step area. [Bug #173457]
- Fixed delete of an if/else step from test explorer keeps bad data leading to unhandled exception on next step recording. [Bug #131600]
- Fixed unhandled exception on undo with logical steps scenario. [Bug #40673]
Find Expression Builder:
- Fixed change element option always prompts to save changes. [Bug #172170]
[Standalone]
Load Testing:
- Fixed Cookies are recorded along with other HTTP headers of a load test. [Bug #167482, PITS #12951]
- Fixed Data driven load test will double URL encode non data driven web form during POST. [Bug #175403, PITS #13935]
- Fixed Databound variables in load tests are not updated properly. [Bug #167473, PITS #12950]
- Fixed Capture Fails in Load with Certificate Error. [Bug #39757]
- Fixed Capturing traffic from existing test fails with IE10 on Windows 8. [Bug #39775]
- Fixed Redirects are being auto followed by Load Agents resulting in duplicate traffic. [Bug #175619]
- Fixed Cookies lower cased cookies. [Bug #175620]
- Fixed 100 Continues being sent by Load Agent. [Bug #175621]
- Fixed unhandled NullReference exception when selecting a browser for capturing traffic from existing Web test. [Bug #39486]
- Fixed Data binding load test with invalid range may cause unhandled exception. [Bug #39774]
- Fixed HTTP request cookie header parsing. [Bug #39668]
Performance Testing:
- Fixed Exporting Performance Results to Word or Excel not working properly. [Bug #131553, PITS #8003]
Project View:
- Fixed Folders containing slashes in their name are not generated correctly. [Bug #173957, PITS #13753]
- Fixed exclude from project may cause out of memory. [Bug #175250]
- Fixed lost focus on deleting nodes. [Bug #174619]
- Fixed displaying IsTestFragment causes confusion. [Problem #19554]
- Fixed NullReference exception when excluding a test from project with compilation error, introduced with internal build 2012.2.1317. [Bug #40896]
Coded Tests:
- Fixed removing test steps and code switching between different type of coded tests. [Bug #40285, #40459, Public #40206]
- Fixed a coded step description silently fails to be parsed giving no feedback to the user. [Bug #173912]
- Fixed unable to display compilation errors in case of running a test from a VB project. [Bug #41073]
Test Lists:
- NEW: Dynamic list rules include "NotContains" comparison. [Bug #155709, PITS #11196]
- Fixed Run list persisting results may throw SerializationException. [Bug #173959, PITS #13777]
- Fixed UI problems displaying tests in grid of Dynamic Test lists. [Bug #39867]
- Fixed erroneously adding tests to the test lists for selected test on scrolling. [Bug #39785]
Results View:
- Fixed Scheduling results from datadriven tests iterations are not sorted properly. [Bug #172829]
TeamPulse Integration:
- Fixed missing Add & Remove test case buttons in the dialog for setting acceptance criteria. [Bug #174062]
[Visual Studio Plugin]
- VS 2012:
- Fixed FileNotFoundException executing test not in project root in VS 2012. [Bug #173817, PITS #13731]
- Fixed Test Explorer does not discover Test Studio tests. [Bug #40558, Portal #40414]
- Fixed Unexpected "known types" error thrown in Visual Studio 2012 during execution. [Bug #40861, Portal #40901]
- Fixed New coded steps don't compile in Visual Studio 2012. [Bug #40531, Portal #40415]
- Fixed Value cannot be null error when running new empty test from Test Explorer. [Bug #41138]
- Fixed Test Explorer RunAll option does not trigger TS tests to run. [Bug #41141]
- Fixed "Customize step in code" in VS 2012 throws null reference exception due to missing Pages.cs file. [Bug #40375]
- Fixed copy/pasted test isn't discovered in Test Explorer.
- Fixed After closing the solution, tests are not cleared from text explorer. [Bug #40565]
- Fixed test discovery doesn't work for closed or not docked test explorer. [Bug #41232]
- Fixed possible unhandled exception in VS on selecting local data test explorer view. [Bug #174082]
- Fixed WPF coded step does not add reference to external assembly built against .Net 4.5 in the settings file. [Bug #40058]
- Fixed Kendo wrapper reference missing in project template leading to compile error. [Bug #40710]
- Fixed Page & element changes are not persisted unless test in open in Visual Studio. [Bug #158523, PITS #11649]
- Fixed Having both WPF and Web tests with code in one project fails to generate Pages.cs file correctly. [Bug #40377]
- Fixed Occasionally the elements explorer is not loaded in Visual Studio. [Bug #40844]
- Fixed unhandled exception for Step Builder in VS when step builder is open, close project and select element from it. [Bug #40795]
[RadControls for AJAX]
- NEW: RadGauge control wrappers and translators.
- Added RadTreeViewItem.Expandable property. [Bug #170554, PITS #13370]
- Added support for fields drag-drop inside the configuration panel.
- Added a BlurAfterTyping property for RadInput typing action.
- Added internal scroll to visible action in handling RadAsyncUpload. [Bug #165038]
- Added RadComboBox.DropDownWidth property and built-in verification.
- Added AutoCompleteBox.EmptyMessage built-in verification.
- Fixed Default RadTreeView control to bring up ContextMenu displays error message on playback. [Bug #176101, PITS #13999]
- Fixed RadTreeViewItem.Expand action generates no code. [Bug #173204]
- Fixed RadGrid records select command when column resizing is enabled.
- Fixed PivotGrod.DragDrop action auto scroll to be visible.
[RadControls for Silverlight/WPF]
- Added RadPropertyGrid control wrappers.
- Added RadMap control wrappers.
- Added RadChartView control wrappers for Range, RangeBar, ScatterSpline and ScatterSplineAreas.
- RadRibbonView:
- Fixed control wrapper names.
- Added RadRibbonGallery control wrapper with IsCompressed and CompressedThreashold build-in verifications.
- Added RadRibbonGroup.Variant property and built-in verification.
- Exposed .CurrentSize property and built-in verification for all ribbon buttons.
- RadMaskedInput:
- Added RadMaskedInput.Value property and built-in verification.
- Fixed default clicks recorded incorrectly leading to useless set text steps during playback.
- RadDiagram: Added control wrappers and translators for DiagramRuler DiagramNavigationPane, SettingsPane.
- Added RadWatermarkTextBox.IsWatermarkVisible property and built-in verification.
- Fixed RadListBox.Items and RadListBoxItem.IsSelected & .IsHighlighted problems.
- Changed: Moved the deprecated RadRibbonBar into new namespaces - Telerik.WebAii.Controls.Xaml.RibbonBar & Telerik.WebAii.Controls.Xaml.Wpf.RibbonBar.
[KendoUI]
- Fixed unable to get the count of KengoGrid items (compatibility with the latest Kendo UI Grid). [Bug #173839, PITS #13732]
- Fixed KendoUI item count verification builder doesn't display the item count. [Bug #174328] | https://www.telerik.com/support/whats-new/release-history/release-notes/teststudioruntime/test-studio-run-time-2012-21420 | CC-MAIN-2021-04 | refinedweb | 1,696 | 57.77 |
A fluent, builder-based library for generating valid Dart code.
Usage
code_builder has a narrow and user-friendly API.
See the
example and
test folders for additional examples.
For example creating a class with a method:
import 'package:code_builder/code_builder.dart'; import 'package:dart_style/dart_style.dart'; void main() { final animal = Class((b) => b ..name = 'Animal' ..extend = refer('Organism') ..methods.add(Method.returnsVoid((b) => b ..name = 'eat' ..body = const Code("print('Yum!');")))); final emitter = DartEmitter(); print(DartFormatter().format('${animal.accept(emitter)}')); }
Outputs:
class Animal extends Organism { void eat() => print('Yum!'); }
Have a complicated set of dependencies for your generated code?
code_builder
supports automatic scoping of your ASTs to automatically use prefixes to avoid
symbol conflicts:
import 'package:code_builder/code_builder.dart'; import 'package:dart_style/dart_style.dart'; void main() { final library = Library((b) => b.body.addAll([ Method((b) => b ..body = const Code('') ..name = 'doThing' ..returns = refer('Thing', 'package:a/a.dart')), Method((b) => b ..body = const Code('') ..name = 'doOther' ..returns = refer('Other', 'package:b/b.dart')), ])); final emitter = DartEmitter.scoped(); print(DartFormatter().format('${library.accept(emitter)}')); }
Outputs:
import 'package:a/a.dart' as _i1; import 'package:b/b.dart' as _i2; _i1.Thing doThing() {} _i2.Other doOther() {}
Contributing
- Read and help us document common patterns over at the wiki.
- Is there a bug in the code? File an issue.
If a feature is missing (the Dart language is always evolving) or you'd like an easier or better way to do something, consider opening a pull request. You can always file an issue, but generally speaking, feature requests will be on a best-effort basis.
NOTE: Due to the evolving Dart SDK the local
dartfmtmust be used to format this repository. You can run it simply from the command-line:
$ pub run dart_style:format -w .
Updating generated (
.g.dart) files
NOTE: There is currently a limitation in
build_runnerthat requires a workaround for developing this package since it is a dependency of the build system.
Make a snapshot of the generated
build_runner build script and
run from the snapshot instead of from source to avoid problems with deleted
files. These steps must be run without deleting the source files.
$ dart run build_runner generate-build-script $ dart compile kernel .dart_tool/build/entrypoint/build.dart $ dart .dart_tool/build/entrypoint/build.dill build --delete-conflicting-outputs | https://pub.dev/documentation/code_builder/latest/ | CC-MAIN-2022-40 | refinedweb | 379 | 54.39 |
Events
In addition to the built-in timing mechanisms for internal control, ChucK has an event class to allow exact synchronization across an arbitrary number of shreds.
What they areChucK events are a native class within the ChucK language. We can create an event objects, and then chuck (=>) that event to now. The event places the current shred on the event's waiting list, suspends the current shred (letting time advance from that shred's point of view). When the the event is triggered, one or more of the shreds on its waiting list is shreduled to run immediately. This trigger may originate from another ChucK shred, or from activities taking place outside the Virtual Machine ( MIDI, OSC, or IPC ).
// declare event Event e; // function for shred fun void eventshred( Event event, string msg ) { // infinite loop while ( true ) { // wait on event event => now; // print <<
>>; } } // create shreds spork eventshred ( e, "fee" ); spork eventshred ( e, "fi" ); spork eventshred ( e, "fo" ); spork eventshred ( e, "fum" ); // infinite time loop while ( true ) { // either signal or broadcast if( maybe ) { <<<"signaling...">>>; e.signal(); } else { <<<"broadcasting...">>>; e.broadcast(); } // advance time 0.5::second => now; }
UseChucking an event to now suspends the current shred, letting time advance:
// declare Event Event e; // ... // wait on the event e => now; // after the event is trigger <<< "I just woke up" >>>;
As shown above, events can be triggered in two ways, depending on the desired behavior.
// signal one shred waiting on the event e e.signal();
Signal() releases the first shred in that event's queue, and shredule it to run at the current time, respecting the order in which shreds were added to the queue.
// wake up all shreds waiting on the event e e.broadcast();
broadcast() releases all shreds queued by that event, in the order they were added, and at the same instant in time
The released shreds are shreduled to run immediately. But of course they will respect other shreds also shreduled to run at the same time. Furthermore, the shred that called signal() or broadcast() will continue to run until it advances time itself, or yield the virtual machine without advancing time. (see me.yield() under concurrency)
MIDI eventsChucK contains built-in MIDI classes to allow for interaction with MIDI based software or devices.
MidiIn min; MidiMsg msg; // open midi receiver, exit on fail if ( !min.open(0) ) me.exit(); while( true ) { // wait on midi event min => now; // receive midimsg(s) while( min.recv( msg ) ) { // print content <<< msg.data1, msg.data2, msg.data3 >>>; } }
MidiIn is a subclass of Event, as as such can be ChucKed to now. MidiIn then takes a MidiMsg object to its .recv() method to access the MIDI data. As a default, MidiIn events trigger the broadcast() event behavior.
OSC eventsIn addition to MIDI, ChucK has OSC communication classes as well:
// create our OSC receiver OscRecv orec; // port 6449 6449 => orec.port; // start listening (launch thread) orec.listen(); function void rate_control_shred() { // create an address in the receiver // and store it in a new variable. orec.event("/sndbuf/buf/rate,f") @=> OscEvent oscdata; while ( true ) { oscdata => now; //wait for events to arrive. // grab the next message from the queue. while( oscdata.nextMsg() != 0 ) { // getFloat fetches the expected float // as indicated in the type string ",f" buf.rate( oscdata.getFloat() ); 0 => buf.pos; } } }
The OscRecv class listens for incoming OSC packets on the specified port. Each instance of OscRecv can create OscEvent objects using its event() method to listen for packets at any valid OSC address pattern.
An OscEvent event can then be ChucKed to now to wait for messages to arrive, after which the nextMsg() and getFloatStringInt() methods can be used to fetch message data.
Creating custom events
Events, like any other class, can be subclassed to add functionality and transmit data:
// extended event class TheEvent extends Event { int value; } // the event TheEvent e; // handler fun int hi( TheEvent event ) { while( true ) { // wait on event event => now; // get the data <<
>>; } } // spork spork hi( e ); spork hi( e ); spork hi( e ); spork hi( e ); // infinite time loop while( true ) { // advance time 1::second => now; // set data Math.rand2( 0, 5 ) => e.value; // signal one waiting shred e.signal(); }
VM Wide EventsOften it can be useful to trigger events across the VM outside of the child/parent shred relationship.
This can be done by declaring a reference to static data within a public class. You may only declare one public class in a file so the following must be added as two files. For more on classes see Objects reference.
This example creates a VM wide event that also has communicates an int value.
File 1: Extend Event to carry int value
//First Extend Event to carry int public class E extends Event{ int value; }
File 2:Declare static version of extend class and instantiate once.
//Create Static Event public class vmwEvent{ static E @ gbEvent; } new E @=> vmwEvent.gbEvent;
This creates the global VM wide event which can then be used as required.
Write int value and broadcast event
//send values while (true){ Std.rand2(100,300) => vmwEvent.gbEvent.value; vmwEvent.gbEvent.broadcast(); 500::ms => now; <<<"sent">>>; }
Receive and read int value for VM wide event.
//receive values while (true){ vmwEvent.gbEvent => now; <<< vmwEvent.gbEvent.value >>>; <<<"got">>>; } | http://archive.flossmanuals.net/chuck/ch023_events.html | CC-MAIN-2020-40 | refinedweb | 868 | 71.75 |
Workshop: Remote Control Panel
We’re going to build an app to run unit tests from the web, using nothing but Python, with Anvil.
To follow along, you need to be able to access the Anvil Editor. Create a free account using the following link:
Step 1: The Run Button
Open the Anvil Editor to get started.
In the top-left there is a ‘Create New App’ button. Click it and select the Material Design theme.
You are now in the Anvil Editor.
First, name the app. Click on the name at the top of the screen and type in a name like ‘Test Manager’., add a Label, a TextBox and a Button..
Align it to the left to make it sit against the TextBox.
Your app should now look something like this:
The next step is to make it do something.
At the bottom of the Properties tool for the Button is a list of events that we can bind methods to. Click the arrow next to the
click event:
You should see some code that looks like this:
def run_tests_button_click(self, **event_args): """This method is called when the button is clicked""" pass
Remove the
pass and add a call to the built-in
alert function:
def run_tests_button_click(self, **event_args): """This method is called when the button is clicked""" alert("Test runs requested: {}".format(self.run_number_box.text, title="Test run")
When you click the Button, you’ll get a dialog box displaying the number of test runs requested.
Step 2: Displaying Test Runs
Let’s make the Button do something a bit more interesting.
Add a Repeating Panel to your app. This is a component that displays the same piece of UI for each element in a list (or other iterable).
Double-click on the Repeating Panel in the Designer. You’ll see most of the page grayed out, and you can drop things into the Repeating Panel’s template. Drop a Card into it, and into that Card, put a Label whose text is set to ‘Date/Time’. Drop another Label next to it and leave it blank for now - it will hold the date and time that the test was run.
Arrange some more Labels until you have a UI that can display the number of tests run, passed, failed and with errors.
To populate the page with a bunch of empty test result cards, just set the Repeating Panel’s
items attribute to an
arbitrary list:
class Form1(Form1Template): def __init__(self, **properties): # ... self.repeating_panel_1.items = [1, 2, 3, 4]
Run your app to see some empty results cards:
Step 3: Displaying Data
Let’s make the Repeating Panel display some data.
Change the
[1, 2, 3, 4] from Step 2 to be an empty list, so the Repeating Panel is empty when the app starts:
self.repeating_panel_1.items = []
And append some fake data to this list when the Button is clicked:
from datetime import datetime from random import randint # ... def run_tests_button_click(self, **event_args): """This method is called when the button is clicked""" for i in range(self.run_number_box.text): tests_run = 6 passed = randint(0, tests_run) failed = tests_run - passed errors = 0 self.repeating_panel_1.items = [{ 'date_time': datetime.now(), 'tests_run': tests_run, 'passed': passed, 'failed': failed, 'errors': errors, }] + self.repeating_panel_1.items
Run your app and hit the ‘Run Tests’ button. You’ll see a number of test result cards corresponding to the number of test runs the user selected.
Let’s get the data into the result card. For each empty Label, click on it in the Design view and add a Data Binding in the Properties window:
Data Bindings tie the value of a property to the value of a Python expression. In this case we’re tying the
text of the
Label to the test run data. Since these Labels are within the Repeating Panel, each element of
self.repeating_panel_1.items is available
to the Label as
self.item. So the Data Bindings are:
and similar for the
'passed',
'failed' and
'errors' Labels.
The
'date_time' label needs to format the
datetime object into a string using the
strftime method:
Clicking on the ‘Run Tests’ button will now generate randomly populated result cards.
Step 4: Get Something To Test
An app like this could manage and report on the stages of a complex build and deployment pipeline. But to keep it simple for this workshop, we’ll clone a very simple Git repo and run the unit tests.
The repo in question is a Roman Numeral Calculator coding challenge (our thanks to Tony “Tibs” Ibbs). To clone it, open a terminal window on your computer, change directory to somewhere you’re happy to put it, and enter:
git clone git@github.com:tibs/roman_adding.git
If you don’t have Git, you can download it as a zip file at
(click on the green ‘Clone or download’ link).
To run the unit tests, simply run the
test_roman_adding.py file.
Make the tests fail randomly
To make this more interesting, let’s add a random calculation error into the code.
In
roman_adding.py, import the
random module and change the calculation from
sum = number1 + number2
to
sum = number1 + number2 + random.choice(['', 'I'])
in 1 out of every 2 runs, this will randomly add 1 (that is,
I) to the result of the calculation. So 1 in 2 of the
unit tests should now fail.
Step 5: Connect your app to your computer
We’re going to use the Uplink to allow Anvil to trigger test runs on your machine from the web app.
First, configure your app to use the Uplink by clicking on
Uplink... in the Gear Menu
and clicking the ‘enable’ button in the modal that comes up:
A random code will be displayed that allows your local script to identify your Anvil app.
On your computer, install the Anvil server module using
pip:
pip install anvil-uplink
(As always, I suggest you do this in a Python Virtual Environment.)
Now create a file in the Roman Adding repo called something like
connect_to_anvil.py. Add these lines at the top
import anvil.server anvil.server.connect("<The Uplink key for your app>")
Where
<The Uplink key for your app> is the key you got from the
Uplink... modal.
Within this script, define a function to call from your app:
@anvil.server.callable def run_tests(times_to_run): print('Running tests...') results = [] for i in range(times_to_run): print("Run number {}".format(i)) return results anvil.server.wait_forever()
The
@anvil.server.callable makes it possible to call this function from the browser code. In the Anvil Editor, add an
anvil.server.call to the top of your click handler:
import anvil.server # ... def run_tests_button_click(self, **event_args): """This method is called when the button is clicked""" results = anvil.server.call('run_tests', self.run_number_box.text)
Run
connect_to_anvil.py. You should see something like
Connecting to wss://anvil.works/uplink Anvil websocket open Authenticated OK
Now when you click on the Run Tests button, your script will print this to your terminal:
Running tests... Run number 0 Run number 1
Step 6: Running the tests from your app
Now to make your Uplink script actually run the unit tests.
Add a call to the
unittest module inside the loop in the
run_tests function and append the results to the
results list:
import unittest from datetime import datetime # .. and inside the run_tests function ... for i in range(times_to_run): # run the tests result = unittest.main(module='test_roman_adding', exit=False).result # unpack the results a bit failed = len(result.failures) errors = len(result.errors) passed = result.testsRun - failed - errors # Create an entry in the results list results.append({ 'date_time': datetime.now(), 'tests_run': result.testsRun, 'passed': passed, 'failed': failed, 'errors': errors, })
Now in your app, you replace the code that concocts fake data with the call to your actual test runner:
def run_tests_button_click(self, **event_args): """This method is called when the button is clicked""" results = anvil.server.call('run_tests', self.run_number_box.text) self.repeating_panel_1.items = results + self.repeating_panel_1.items
You’ve now got a web app that runs tests on a remote machine and displays the results!
Step 7: Store the results persistently
Currently, when the app is reloaded in the browser, the existing test results are cleared from memory. It would be nice if your test results could persist.
In the Editor, click on the plus next to ‘Services’ and add the Data Tables Service. Add a table named
test_results.
Add a ‘Date and Time’ column called
date_time and ‘Number’ columns called
tests_run,
passed,
failed and
errors.
We’ll access this table from a Server Module. A Server Module is Python code that runs in a Python runtime on a server managed by us. Click on the plus next to ‘Server Modules’ in the Editor. You’ll see a code editor with a yellow background, denoting the Anvil server environment.
Functions in here can be decorated as
@anvil.server.callable just like functions in your Uplink script. Write a simple
function to get the data from the Data Table.
@anvil.server.callable def get_test_results(): return app_tables.test_results.search(tables.order_by('date_time', ascending=False))
To put the data into the Data Table, we’ll use another tiny function:
@anvil.server.callable def store_test_results(results): for result in results: app_tables.test_results.add_row( date_time=result['date_time'], tests_run=result['tests_run'], passed=result['passed'], failed=result['failed'], errors=result['errors'], )
(If you’re quite familiar with Python you might spot that you could just do
app_tables.test_results.add_row(**result))
So we have functions for storing test results and retrieving them. Since they are
anvil.server.callable, they can be
called from anywhere, so both the browser and
connect_to_anvil.py can use them to persist data.
When the
connect_to_anvil.py script has finished running tests, it needs to run the
store_test_result function. Add that call in now:
@anvil.server.callable def run_tests(times_to_run): # ... run the tests, then ... anvil.server.call('store_test_results', results) return results
And when the app starts up, it should retrieve the historical test results from the Data Table:
class Form1(Form1Template): def __init__(self, **properties): # ... self.repeating_panel_1.items = list(anvil.server.call('get_test_results'))
Now your test results are stored between sessions. Try launching a few test runs with your app and refreshing the page. The previous runs are still there, and when you trigger new runs they get added to the list.
And we’re done
And that’s it! You’ve just built the foundation of a Continuous Integration platform in Anvil.
It connects to a remote machine, runs a script that you might typically find in a build-test-deploy pipeline, and stores data about the runs so users can see what’s going on.
Connecting your app to an arbitrary Python process opens up an infinity of possibilities.
You could construct a more elastic build system by spinning up cloud servers (using, say, the AWS Boto3 module from Anvil’s Server Modules) and connecting to them with the Uplink to run build scripts.
You could connect to an Internet of Things gateway and use your app to manage your devices.
You can even run an interactive terminal session in the browser.
If you can do it in Python, you can connect it to your Anvil app.
Clone the finished app
Every app in Anvil has a URL that allows it to be imported by another Anvil user.
Click the following link to clone the finished app from this workshop.
If you want to run the cloned version, you need to enable the Uplink as detailed in Step 5.
Your app is live on the internet already (find out more).
Extensions
If you’ve got this far, you might enjoy figuring out how to grow your app further. Some things you might like to try include:
- Storing the ID of the commit being tested.
- Running the tests every time a commit is made, and pushing the results to your app.
- Adding a more detailed breakdown of test results.
- Adding linting results.
- Adding test coverage results.
- Adding a ‘deploy’ button to the app and watching the progress of a deployment.
- Controlling other hardware to visually display test status, for example using an Easter Island Tiki head that snorts dry ice.
Alternatively, take a look at the TODO list workshop and the Data Dashboard workshop. | https://anvil.works/learn/workshops/test-manager | CC-MAIN-2019-35 | refinedweb | 2,045 | 65.42 |
Just tell him that "functions are like all other variables and can therefore be passed by other functions or returned by other functions. " If your friend understands variables and functions and he can't make the "leap" (and assuming you're right, of course) then your friend doesn't understand variables and functions. Happy Friday. Sean On 9/21/07, Cristian <super.sgt.pepper at gmail.com> wrote: > On Sep 21, 3:44 pm, Ron Adam <r... at ronadam.com> wrote: > > > I think key may be to discuss names and name binding with your friend. How > > a name is not the object it self, like a variable is in other languages. > > For example show him how an object can have more than one name. And discus > > how names can be bound to nearly anything, including classes and functions. > > I could discuss name binding but it would be great if Python said this > itself. After all, you can even bind a module with the foo = bar > syntax by using __import__ function. If function definitions followed > the same pattern, I think a beginner would subconsciously (maybe even > consciously) realize that function names are just like everything > else. Actually, this would be helpful for many people. If you come > from a language like Java you're used to thinking of attributes and > methods as living in different namespaces. I think a new syntax will > encourage seasoned programmers think in a more Pythonic way. > > Python has done a very good job in easing people into programming. My > friend doesn't come to me very often because the syntax is clear and > simple and the builtin datatypes allow you to do so much. My goal is > that I would never have to explain to him about name binding; that > he'd pick it up by learning the language on his own. He's learned > lists, dictionaries and even some OOP without me. I don't think name > binding would be a stretch. > > > You could also discus factory functions with him. Once he gets that a > > function can return another function, then it won't be so much of a leap > > for a function to take a function as an argument. > > I think this isn't the most intuitive way of approaching first order > functions. It's true that if a function can return another function > then a function must be first order (i.e., it's just like any other > variable), but that seems almost backwards to me. I think it would > make more sense to have beginners _know_ that functions are like all > other variables and can therefore be passed by other functions or > returned by other functions. That I think would be better accomplished > if they define functions the same way you would define other variables > that you know can be passed and returned. > > > -- > > -- Sean Tierney | https://mail.python.org/pipermail/python-list/2007-September/442737.html | CC-MAIN-2014-10 | refinedweb | 473 | 71.34 |
In Ignition 7.9.x the log files are now exported as an .idb file.
Since I have some systems and clients that do not give me access to the file system so I can get the wrapper log.
What application am I supposed to use to read the contents of the .idb file?
In Ignition 7.9.x the log files are now exported as an .idb file.
It’s just a sqlite DB, so you can use any utility you want that can understand it. Not that looking at a DB full of log entries is very useful…
So lets say I grab which sounds like it would work if it’s a sqlite DB.
But it doesn’t recognize .idb as a file type it can use.
Furthermore, the file is for some outdated software.
The software from here: does not work to open it.
Do you have a suggestion for a utility that can understand it?
the extension is not important, in the file open dialog chose . if possible or change the extension of your db file with an extension sqlitebrowser support.
You can use as well
I wouldn’t have guessed it, but it works if you just load it anyway. Thanks.
I’m using the tool from
I wrote a quick Python function to dump the IDB to a typical-looking log file:
import sqlite3 from datetime import datetime def dump(idb_file, logger_name, output_file): """ Dump an Ignition SQLite log database to file in typical log file format. :param idb_file: .idb file to dump :param logger_name: logger name (package) to filter on :param output_file: path for output text file """ try: connection = sqlite3.connect(idb_file) cursor = connection.cursor() pattern = logger_name + '.%' rows = cursor.execute('SELECT level_string, timestmp, thread_name, logger_name, formatted_message ' 'FROM logging_event WHERE logger_name LIKE "%s" ORDER BY timestmp' % pattern) count = 0 with open(output_file, 'w') as f: for row in rows: count = count + 1 (level_string, timestmp, thread_name, logger_name, formatted_message) = row time_string = datetime.fromtimestamp(timestmp / 1000.0) f.write( '%-5s %s [%s] %s %s\n' % (level_string, time_string, thread_name, logger_name, formatted_message)) print 'From "%s", wrote %d lines to "%s"' % (idb_file, count, output_file) finally: connection.close() | https://forum.inductiveautomation.com/t/viewing-downloaded-logs/14060 | CC-MAIN-2021-39 | refinedweb | 357 | 64.51 |
Safari Books Online is a digital library providing on-demand subscription access to thousands of learning resources.
Calling close() on a socket closes both halves of the bidirectional communication channel. Sometimes, it is useful to close one half of the connection, so that data can be transmitted in just one direction through the socket. The shutdown() system call provides this functionality.
#include <sys/socket.h> int
shutdown(int sockfd, int how);
Returns 0 on success, or -1 on error
The shutdown() system call closes one or both channels of the socket sockfd, depending on the value of how, which is specified as one of the following:
SHUT_RD
Close the reading half of the connection. Subsequent reads will return
end-of-file (0). Data can still be written to the socket. After a
SHUT_RD on a UNIX domain stream
socket, the peer application receives a
SIGPIPE signal and the
EPIPE error if it makes further attempts to write to the
peer socket. As discussed in Calling shutdown() on a TCP Socket,
SHUT_RD can’t be used meaningfully for TCP
sockets. | http://my.safaribooksonline.com/book/programming/linux/9781593272203/sockets-advanced-topics/the_shutdown_open_parenthesis_close_pare | CC-MAIN-2014-15 | refinedweb | 179 | 52.09 |
Windows File Tagger Shell Extensions (C++)
Budjetti $1-500 USD
------------------------------------
BRIEF
------------------------------------
This project requires solid experience in developing shell extensions -- particularly context menu and namespace extensions.
Develop a set of Windows shell extensions that will allow the user to 1) assign (and remove) one or more arbitrary tags to any file, and 2) browse a virtual folder whose subdirectories are the tags in use and whose contents are files who share the tags in this virtual subdirectory. This is a small utility with some tricky plumbing.
------------------------------------
DETAIL
------------------------------------
== General Requirements ==
- Must run under Windows XP/Vista/7. 64-bit support is not required.
- Must be written in unmanaged C++. VB6 or managed solutions (i.e. C#) are prohibited (If you're submitting a bid, you should already know this restriction.)
- Must be efficient. Rough goal for a dual-core 2GHz machine w/ 1GB RAM is no more than 3s to filter down 5,000 files in the worst case. This is flexible, and meant to give a starting point, but it should be relatively quick.
- File tagging (or untagging) should not modify the file itself in any way.
- Security of tags or tag/file associations is not an issue.
- Must not access/require internet access.
== Requirement 1 - Tag Manipulation - 10% ==
Tagging and removing of tags on arbitrary files, should be the easier of the two tasks and should be implemented as a context menu. The context submenu should include a list of all tags available with those already selected checked or otherwise marked, and allow a user to mark one or more selected files with a given tag.
A tag list will be stored in a plaintext, user-modifiable file. This could be a CSV, INI, whatever. Tag & files associations can be stored in any way that proves efficient. This part does not have to be human readable so a binary format will likely be optimal.
(Optional requirement 1b, a property page accessible via the Properties context menu item displaying checkboxes for the available tags indicating which tags the file is associated with and allowing the user to toggle them. Only if you're feeling ambitious...)
== Requirement 2 - Tag Browsing - 90% ==
Develop a shell namespace extension to create a virtual directory on the local machine. This directory will 'point' to a real directory on the machine but display the contents of that folder and (its subfolders) in a tag-based way. This virtual directory will contain subfolders. The subfolders are tags that have 1 or more files associated with them (empty tags will not be shown). Opening a subfolder will the display subfolders and items -- the subfolders will be tags which, in combination with the current tag, yield 1 or more files; and files which match the currently selected tags. In essence, the relative path from the namespace root becomes a list of tags to filter for. At no point should a tag be listed as a subfolder if navigating to it would yield 0 results.
For example, assuming the namespace is rooted at C:\User\Tags, then a 'path' of "C:\User\Tags\Wallpapers\Car" should display files tagged with at least 'Wallpapers' and 'Car'. If there were files tagged with 'Wallpaper', 'Car', and 'Beach', then "Beach" would be a subfolder (files with the Beach tag would be shown at this point, however, clicking on the Beach folder would filter out those without that tag.)
Folders under this namespace should behave and respond as standard Windows Explorer folders. Toolbar features such as various ShellViews should work as well as context menus -- and of course, Tagging. This will probably entail using DefView. If I knew for sure, I'd be writing this myself.
------------------------------------
Deliverables:
------------------------------------
- Compiled DLLs
- List of any necessary registry settings needed to 'install'. (.reg file will work)
- Source, including but not limited to: classes, header files, any other resource files or data necessary for compilation and/or use.
Code should be reasonably well documented, at least at the procedure level. | https://www.fi.freelancer.com/projects/c-c-windows/windows-file-tagger-shell-extensions/ | CC-MAIN-2018-13 | refinedweb | 661 | 62.88 |
The problem “Count number of triplets with product equal to given number” states that we are given an integer array and a number m. The problem statement asks to find out the total number of triplets of with product equals to m.
Example
arr[] = {1,5,2,6,10,3} m=30
3
Explanation
Triplets which formed product equal to m are (1,5,6), (5,2,3) and (1,3,10)
arr[] = {2,4,5,1,10} m=20
2
Explanation
Triplets which formed product equal to m are (2,1,10), (4,5,1)
Algorithm
- Declare a map.
- Store the index of each element into the map by traversing the array.
- Set output to 0.
- Traversing the array again using a nested loop:
- Check if((arr[i] * arr[j] <= m) && ( arr[i] * arr[j] ! = 0) &&( m % (arr[i] * arr[j]) == 0)).
- If this is found to be true, then find out m / (arr[i] * arr[j]) and search it in the map.
- Also check for, the third element we found is not equal to the current two elements (arr [i] and arr [j]).
- If the condition satisfies, then increase the count of output by 1.
- Return output.
Explanation
Our task is to find out the triplets whose product should be equal to the given number m. We are not going to use a naive approach to solve this question, it costs us more time. Rather than visiting picking each element of the triplet, we will use Hashing.
We will traverse the given array and store the index of each array element into the map along with the given array element. This is being done because later, we are going to check if the element we found should not be repeated. If the element has the same index. This means that we do not count the same array element twice for the triplet.
After the traversal of the array, we have the values in the hashmap. Set the value of output to 0. Now, we are going to use a nested loop. In which we take an element in the outer loop and in the inner loop next pick another element. Then we are going to find out the third element. All of the condition that lies in ‘if statement’ is used to find out the third element. After doing arr[i] * arr[j] all we have to find is the third element. So on a simple note, if a*b*c=m ⇒ then c = m / a * b.
Then check for the third element, if it presents in the map, means we have found it. We just have to check if the element we found should not be equal to the current two elements of the triplet. Also, current index should not have been repeated before. If all of the conditions are satisfied then we just increase the count of output by 1. This means we have one or more triplets. Then at last simply return the output.
C++ code to count number of triplets with product equal to given number
#include<iostream> #include<unordered_map> using namespace std; int getProductTriplets(int arr[], int n, int m) { unordered_map<int, int> numindex; for (int i = 0; i < n; i++) numindex[arr[i]] = i; int output = 0; for (int i = 0; i < n - 1; i++) { for (int j = i + 1; j < n; j++) { if ((arr[i] * arr[j] <= m) && (arr[i] * arr[j] != 0) && (m % (arr[i] * arr[j]) == 0)) { int third = m / (arr[i] * arr[j]); auto it = numindex.find(third); if (third != arr[i] && third != arr[j]&& it != numindex.end() && it->second > i&& it->second > j) output++; } } } return output; } int main() { int arr[] = {1,5,2,6,10,3}; int n = sizeof(arr) / sizeof(arr[0]); int m = 30; cout <<"Total product triplets are: "<<getProductTriplets(arr, n, m); return 0; }
Total product triplets are: 3
Java code to count number of triplets with product equal to given number
import java.util.HashMap; class TripletProductPair { public static int getProductTriplets(int arr[], int n, int m) { HashMap<Integer, Integer> numindex = new HashMap<Integer, Integer>(n); for (int i = 0; i < n; i++) numindex.put(arr[i], i); int output = 0; for (int i = 0; i < n - 1; i++) { for (int j = i + 1; j < n; j++) { if ((arr[i] * arr[j] <= m) && (arr[i] * arr[j] != 0) && (m % (arr[i] * arr[j]) == 0)) { int third = m / (arr[i] * arr[j]); numindex.containsKey(third); if (third != arr[i] && third != arr[j]&& numindex.containsKey(third) && numindex.get(third) > i && numindex.get(third) > j) { output++; } } } } return output; } public static void main(String[] args) { int arr[] = {1,5,2,6,10,3}; int m = 30; System.out.println("Total product triplets are: "+getProductTriplets(arr, arr.length, m)); } }
Total product triplets are: 3
Complexity Analysis
Time Complexity
O(n2) where “n” is the number of elements in the array. Since we have used two nested loops and used Hashmap to search for the third element. So, this searching operation is being done by HashMap in O(1) which was previously being done in O(N) time in a naive approach. Thus this speed up is because of the HashMap.
Space Complexity
O(n) where “n” is the number of elements in the array. Because we will store all elements in the map. The space complexity is linear. | https://www.tutorialcup.com/interview/hashing/count-number-of-triplets-with-product-equal-to-given-number.htm | CC-MAIN-2021-49 | refinedweb | 890 | 72.16 |
This page is a snapshot from the LWG issues list, see the Library Active Issues List for more information and the meaning of C++14 status.
Section: 32.4.4.3 [thread.lock.unique] Status: C++14 Submitter: Anthony Williams Opened: 2011-11-27 Last modified: 2017-07-06
Priority: Not Prioritized
View all issues with C++14 status.
Discussion:
I just noticed that the unique_lock move-assignment operator is declared noexcept. This function may call unlock() on the wrapped mutex, which may throw.Suggested change: remove the noexcept specification from unique_lock::operator=(unique_lock&&) in 32.4.4.3 [thread.lock.unique] and 32.4.4.3.1 [thread.lock.unique.cons]. Daniel: I think the situation is actually a bit more complex as it initially looks. First, the effects of the move-assignment operator are (emphasize mine):
Effects: If owns calls pm->unlock().
Now according to the BasicLockable requirements:
m.unlock()3 Requires: The current execution agent shall hold a lock on m. 4 Effects: Releases a lock on m held by the current execution agent. Throws: Nothing.
This shows that unlock itself is a function with narrow contract and for this reasons no unlock function of a mutex or lock itself does have a noexcept specifier according to our mental model.Now the move-assignment operator attempts to satisfy these requirement of the function and calls it only when it assumes that the conditions are ok, so from the view-point of the caller of the move-assignment operator it looks as if the move-assignment operator would in total a function with a wide contract. The problem with this analysis so far is, that it depends on the assumed correctness of the state "owns". Looking at the construction or state-changing functions, there do exist several ones that depend on caller-code satisfying the requirements and there is one guy, who looks most suspicious:
unique_lock(mutex_type& m, adopt_lock_t);11 Requires: The calling thread own the mutex.
[…]
13 Postconditions: pm == &m and owns == true.
because this function does not even call lock() (which may, but is not required to throw an exception if the calling thread does already own the mutex). So we have in fact still a move-assignment operator that might throw an exception, if the mutex was either constructed or used (call of lock) incorrectly.The correct fix seems to me to also add a "Throws: Nothing" element to the move-assignment operator, because using it correctly shall not throw an exception.
[Issaquah 2014-02-11: Move to Immediate after SG1 review]
Proposed resolution:
This wording is relative to the FDIS.
Change 32.4.4.3 [thread.lock.unique], class template unique_lock synopsis as indicated:
namespace std { template <class Mutex> class unique_lock { public: typedef Mutex mutex_type; […] unique_lock(unique_lock&& u) noexcept; unique_lock& operator=(unique_lock&& u)
noexcept; […] }; }
Change 32.4.4.3.1 [thread.lock.unique.cons] around p22 as indicated:
unique_lock& operator=(unique_lock&& u)
noexcept;
-22- Effects: If owns calls pm->unlock().-23- Postconditions: pm == u_p.pm and owns == u_p.owns (where u_p is the state of u just prior to this construction), u.pm == 0 and u.owns == false. -24- [Note: With a recursive mutex it is possible for both *this and u to own the same mutex before the assignment. In this case, *this will own the mutex after the assignment and u will not. — end note] | https://cplusplus.github.io/LWG/issue2104 | CC-MAIN-2019-22 | refinedweb | 563 | 53.51 |
Talk:Order of Uncyclopedia
From Uncyclopedia, the content-free encyclopedia.
Damn man. This is fantastic. I bow once again to your magnificance. --Famine 22:06, 2 Aug 2005 (UTC)
Dang skippy. I also figured out how to put stuff after my username in sigs by copying Elvis. The bloke really is quite invaluable. --Sir Rcmurphy CUN 22:20, 2 Aug 2005 (UTC)
Are ROUNs anything like ROUSs?--Flammable 20:41, 3 Aug 2005 (UTC)
Since I created the Writer of the Month award, technically shouldn't I be a Duke or something? --Savethemooses 23:50, 4 Aug 2005 (UTC)
[edit] Uncyclopedia Namespace
I think this is important enough to be moved to the Uncyclopedia namespace. I already moved my Order of Uncyclopedia/Simple charts to Uncyclopedia:Awards, Decorations and Honours. just an idea--Insertwackynamehere CUN 01:50, 25 Aug 2005 (UTC)
[edit] I have a question
what exactly is the hmrfra awarded for? and also do regular Commanders (CUN) use the "Sir" prefix also or do they just use "CUN" postfix?--Insertwackynamehere CUN 02:10, 4 Aug 2005 (UTC) EDIT: also, Sir Elvis, the fact the Sir comes before the user seems to break uncyclopedias recognition that its a user page, just so you know :P
- Just fixed it now, lost all the history but not to major --Sir Elvis KUN | Petition 10:10, 4 Aug 2005 (UTC)
- cool :) maybe it would be better to format everything User:prefix name postfix, instead? also just through this together Order_of_Uncyclopedia/Simple_charts#User_Page_Name do you think that works?--Insertwackynamehere CUN 13:47, 4 Aug 2005 (UTC)
- Dang nibits. I just read the article and found that only the two highest ranks are knights. I'm not a knight so I can't have "Sir." I'm so depressed right now. --Rcmurphy CUN 02:29, 4 Aug 2005 (UTC)
- Darnit :( Maybe Sir Elvis could change that to the three highest ranks... (hint hint) also instead of using <font size=smaller> you should use <small> Basing everything on Elvis, the sig format should be as follows: [[User:<name>|<prefix> <name>]] <small>[[Order_of_Uncyclopedia#<anchor two specific order>|<postfix>]]</small> mine looks as follows: --Insertwackynamehere CUN 02:38, 4 Aug 2005 (UTC)
- Elvis and I had a row about fonts in Template_talk:Wilde. How they render is a direct function of what browser you view them in, and what settings you have. See our beautiful screen shots there if you're bored. --Famine 04:43, 5 Aug 2005 (UTC)
Answers:
- Re: HMRFRA is awarded to members of military units that have performed conscious acts of mediocrity or Civil Servants in liue of a Carriage Clock. (it was just an amusing award to replace the British Empire Medal from the OBE that I sporked from).
- Mega Deletion Award now also gives promotion to KUN.
- Nothing to stop you awarding yourself a Knight Bachelorhood and calling yourself Sir :-)
- I am now slightly scared of the beast I created.
--Sir Elvis KUN | Petition 10:31, 4 Aug 2005 (UTC)
[edit] Primary writer?
How do we determine Primary writer, is it the OA, or the greatest contributor?--Flammable OUN 16:56, 4 Aug 2005 (UTC)
- Bit of both really, the wiki system (obviously) dosn't lend itself to picking one person over another, if in doubt I've added more than one, if you think you have been missed off by all means give yourself a promotion! --Sir Elvis KUN | Petition 17:00, 4 Aug 2005 (UTC)
[edit] charts
Order of Uncyclopedia/Simple charts made this page for quicker lookness ;) --Insertwackynamehere CUN 03:32, 4 Aug 2005 (UTC)
- moved to Uncyclopedia:Awards, Decorations and Honours--Insertwackynamehere CUN 01:48, 25 Aug 2005 (UTC)
[edit] Limited to 12?
The top rank is limited to 12 people, but what happens when more then 12 writer of the months awards are given out? Rangeley 23:06, 17 Oct 2005 (UTC)
- heh elvis will have to confirm this but I'm pretty sure those "limits" are just sarcastic and part of the original (pre-sporked) article from Wikipedia --Maj Sir Insertwackynamehere
CUN VFH VFP Bur. CMInsertwackynamehere | Talk 00:07, 18 Oct 2005 (UTC)
[edit] The Order
Hi! I'm a n00b Uncyclopedian, a Wikipedian :), and a minor conspirator and a major anti-conspirator in the Grand Conspiracy Theory. How do you get into the order and move up in rank? If nobody answers my questions I can and will send legions of spork-wielding squirrels wearing pickelhaubes to eat you. Muahahahaaa! Filmcom 15:15, 2 March 2006 (UTC)
- You're a Member of the Order just by registering on Uncyc. You can put {{MOOU}} or {{MUN}} on your userpage now. To gain rank you need to win awards for great writing, helpful maintenance or some other cool thing. The criteria for each rank are on the main Order page. --—rc (t) 15:25, 2 March 2006 (UTC)
[edit] International Flavour
I've uploaded and added a few flag icons in front of people's names. I thought it might be fun to see the diversity of contributors in the Order. More matching flags are available free from: (whole pack) (browse for individual ones)
~ T. (talk) 17:07, 2 March 2006 (UTC)
- Have a look at mine....and replace the flag part with the US one..... -- Sir Mhaille
(talk to me)
[edit] PotM
Shouldn't PotM count for something? Like, even GUN? -- §. | WotM | PLS | T | C | A 21:44, 28 December 2006 (UTC)
[edit] This page does not exist
Haha. Okay. I see your point. It should be protected so no one else does this too.SteveSims 23:00, 26 May 2007 (UTC)
[edit] Limits?
I just noticed that it says in the intro that the GUN and KUN ranks are limited to 20 members each. If that's the case, then why does each rank clearly have more than 20 members? Also, I find it cool to see that once upon a time, even the current admins didn't have fancy signatures. P.M., WotM, & GUN, Sir Led Balloon
(Tick Tock) (Contribs) 23:20, 26 June 2007 (UTC)
- Back when Elvis wrote the guidelines I don't think anyone thought Uncyc would get this popular or that the awards system would still exist in any recognizable form two years later. In conclusion: as with so many other things at Uncyclpedia, ignore the rules. —rc (t) 01:08, 27 June 2007 (UTC)
[edit] Umm...
Is Grand Master kind of like Grand Dragon? Or more like the Pope? (Which would make Oscar Wilde Jesus, I suppose.) --CUN RA Talk to me _ 22:18, 28 October 2007 (UTC)
- We have no Grand Master, we have a Knight/Dame Grand Cross. It is very much like the Grand Dragon/Wizard, though. WHITE POWER!For the record, I'm not a racist, I'm just joking around. - P.M., WotM, & GUN, Sir Led Balloon
(Tick Tock) (Contribs) 22:39, Oct 28
- Your wrong Led. Chronarion is Grand Master, the rest of us, the highest rank is GUN--Sir Manforman
22:52, 28 October 2007 (UTC)
[edit] noob wishing to join
I have little idea as to how the order works. can anyone tell me how to join?
~ NEZLR
21:16, 18 May 2008 (UTC)
- Win something. To become a CUN, you can get an article featured, get an image featured, win NotM, or win RotM. I think there may be some other awards that can get you in as a CUN, but I can't remember. ~Minitrue Sir SysRq! Talk! Sex! =/ GUN • WotM • RotM • AotM • VFH • SK • PEEING • HP • BFF @ 23:04 May 18
So, if my currently nominated image (the iceberg one) were to win the vote, i can add CUN to my signature and become a member? sweet.
[edit] Banninated?
Sorry to post in here, but I have a problem. The front page is all messed up, and it has a note saying:
."
I must state that I have not thrown a hissy fit or sockpuppeted (I don't see even how I could do that as an anonymous user [explain!]76.185.146.49 14:38, 15 October 2008 (UTC)
- AH...nevermind. Everything's back to normal and apparently that note was the featured article (O.o) :)76.185.146.49 14:51, 15 October 2008 (UTC) | http://uncyclopedia.wikia.com/wiki/Talk:Order_of_Uncyclopedia | crawl-002 | refinedweb | 1,381 | 71.44 |
Re: My view on this "Is blah an assembler"
From: C (blackmarlin_at_asean-mail.com)
Date: 08/16/04
- ]
Date: 16 Aug 2004 11:34:52 -0700
"Beth" <BethStone21@hotmail.NOSPICEDHAM.com> wrote in message news:<WOQTc.1198$Xu.828@newsfe4-gui.ntli.net>...
[snip]
> You're actually criticising "type casting"...legitimately because it _is_
> an often horrid thing to have to include in a syntax...HLA merely, like
> every other assembly language, picks up the nastiness of this...it's not at
> all unique to HLA...other assemblers start to look horrid when you start to
> get into "mov [ stringstr ptr ebx ].memberA, byte ptr 34" style of syntax
> too...
Hmm, in Luxasm that would be (assuming ebx is typed as 'stringstr') ...
mov ebx->memberA:1, 34
Shorter, tidier, but still ugly.
[snip]
> I'm not sure that C (the person, not the language) picked up my suggestion
> of this for LuxAsm syntax or not...but I was thinking that we see lots of
> assemblers use things like the following: "stos operand" versus "stosb",
> "stosw", "stosd"...or "push dword" versus "pushd"...or, of course, somewhat
> univeral is "jmp" (tool to decide size with "jump optimisation"), "jmp
> near", "jmp far" (explicit sizes, used regardless of "jump optimisation"),
> etc...
Well, I did not pick up on your suggestion, but I have had similar
ideas myself -- have a look in the /document/ directory on the Luxasm
CVS -- there are some files noting ideas for a logically consistant
syntax, which could be used as an alternate to the default Intel
style syntax, possibally by changing namespaces. So you would have
something like...
add ax, bx -> add.w a, b
mov ax, bx -> mov.w a, b
mov cs, dx -> mov.sw c, d
movzx eax, bl -> mov.db a, b
movsb -> mov.ab
paddb mm0, mm1 -> add.xb r0, r1
paddb xmm0, xmm1 -> add.vb r0, r1
[snip]
> I think C worked out a ":2" / ":4" convention or something...nice - perfect
> for the "constant" issue - but it's a bit "non-standard" and
> "non-Intel-syntax"...putting "b", "w" and "d" as a suffix on the mnemonic
> is a scheme already being used for other instructions in the "Intel" style
> already...extending that to, basically, the rest of the instruction set
> (except for those instructions where such a thing doesn't make
> sense...wouldn't need it for "movq", for example ;)...
The idea for the ':2' / ':4' convention is an alternate to the
Intel syntax 'word ptr' / 'dword ptr' which is generally agreed
as both ugly, wasteful to type and adding little to the read-
ability of the code. However, as you said, this syntax is
unsuitable for mneumonics (mainly because it would cause a
parsing conflict with the label definition syntax, though, as
Luxasm is not a context free grammer, this problem my be solvable).
But using a straight 'b', 'w' or 'd' is also not possable as
Intel have already stimied this by having different instructions
with those names -- though using '.b', '.w' or '.d' can work.
A better solution, I believe, is to redesign the instruction set
from scratch (much like Herbert has done), but keep that set as
a seperate mode, so a more familiar Intel set is available by default.
[snip]
> Oh, note, C, Frank, that one thing to consider about LuxAsm and "data
> typing" is that if we do have it (which C appears to want a loose scheme of
> and I'd be completely behind that idea :)...
For anyone who does not know, the syntax I am using is a system of
'type recording' which does little more than noting the label of
the type -- infact that label may be anything, as the assembler
makes virtually no use of that label. The 'type recording' comes
into play with the macro library, allowing powerful macros to be
built which make use of the extra information which may be
recorded with each label. For instance you could write a 'mov'
macro which checks the recorded type of a register matches the
recorded type of a variable. (Luxasm also provides a '->'
operator which does a text substitution based on the recorded
type, the user may of course elect not to use this operation.)
There is one other use for 'type recording', that is you can do...
#equate dword, 4 ; set dword as number 4
#label my_label : dword ; define label as current pos
#d 0xdeadbeef ; define initial value of label
mov [ my_label ], 42 ; move a new value to label
Which would use the equate to determine the size of 'my_label'
as no other type has been provided, but this would only work
when the type label has been equated to some value.
C
2004-08-16
- ] | http://coding.derkeiler.com/Archive/Assembler/alt.lang.asm/2004-08/0860.html | crawl-002 | refinedweb | 785 | 70.13 |
#include <crypto/chacha20.h>
#include <crypto/common.h>
#include <uint256.h>
#include <chrono>
#include <cstdint>
#include <limits>
Go to the source code of this file.
Get 32 bytes of system entropy.
Do not use this in application code: use GetStrongRandBytes instead.
Definition at line 276 of file random.cpp.
Generate a uniform random integer in the range [0..range).
Precondition: range > 0
Definition at line 591 of file random.cpp.
Overall design of the RNG and entropy sources.
We maintain a single global 256-bit RNG state for all high-quality randomness. The following (classes of) functions interact with that state by mixing in new entropy, and optionally extracting random output from it:
On first use of the RNG (regardless of what function is called first), all entropy sources used in the 'slow' seeder are included, but also:
When mixing in new entropy, H = SHA512(entropy || old_rng_state) is computed, and (up to) the first 32 bytes of H are produced as output, while the last 32 bytes become the new RNG state. Generate random data via the internal PRNG.
These functions are designed to be fast (sub microsecond), but do not necessarily meaningfully add entropy to the PRNG state.
Thread-safe.
Definition at line 584 of file random.cpp.
Definition at line 601 of file random.cpp.
Definition at line 596 of file random.cpp.
Gather entropy from various sources, feed it into the internal PRNG, and generate random data using it.
This function will cause failure whenever the OS RNG fails.
Thread-safe.
Definition at line 585 of file random.cpp.
Gathers entropy from the low bits of the time at which events occur.
Should be called with a uint32_t describing the event at the time an event occurs.
Thread-safe.
Definition at line 587 of file random.cpp.
Gather entropy from various expensive sources, and feed them to the PRNG state.
Thread-safe.
Definition at line 586 of file random.cpp.
Check that OS randomness is available and returning the requested number of bytes.
Definition at line 641 of file random.cpp.
Initialize global RNG state and log any CPU features that are used.
Calling this function is optional. RNG state will be initialized when first needed if it is not called.
Definition at line 710 of file random.cpp.
More efficient than using std::shuffle on a FastRandomContext.
This is more efficient as std::shuffle will consume entropy in groups of 64 bits at the time and throw away most.
This also works around a bug in libstdc++ std::shuffle that may cause type::operator=(type&&) to be invoked on itself, which the library's debug mode detects and panics on. This is a known issue, see
Definition at line 231 of file random.h. | https://doxygen.bitcoincore.org/random_8h.html | CC-MAIN-2021-43 | refinedweb | 458 | 67.15 |
The Future of Style - W3C 2016-07-22T00:00:05+00:00 Planet/2.0 + Video of the Week–Jen Simmons: Real Art Direction on the Web 2016-07-21T23:57:04+00:00 <p>At Respond this year, Jen Simmons gave a very well received session on the current state of CSS layout. A great deal is now possible that never has been before with flexbox, and even more is in the pipeline with Grid layouts. </p> <p>We finally have the tools necessary to create amazing page designs on the web. Now we can art direct our layouts, leveraging the power and tradition of graphic design. In this eye-opening talk, Jen explores concrete examples of an incredible range of new possibilities.</p> <p.</p> <p></p> <h4>Get more like this delivered weekly</h4> of the Week–Jen Simmons: Real Art Direction on the Web</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 Minutes Telecon 2016-07-20 2016-07-21T00:22:12+00:00 <ul> <li><b>Resolved: </b>Add AbobeRGB and ProPhotoRGB as predefined spaces. Allow either the table of numbers or an ICC v.4 profile with relative colorimetric intent</li> <li><b>Resolved: </b>Add a single CMYK profile, with relative colorimetric intent, mainly to use as a fallback</li> <li>TabAtkins explained the work being done on web components which will solve for many of the problems authors are facing around namespaces. The group agreed that this approach did seem like it would help and more experimentation in this direction would lead to more progress. The group also actioned TabAtkins to create a wiki to gather the history of work and experimentation and allow authors to comment and contribute to further progress.</li> <li><b>Resolved: </b>Outside bullets are outside the box (See <a href="">testcase</a>).</li> <li><b>Resolved: </b>Accept the <a href="">proposed change</a> for <a href="">Grid</a> (implied min takes on the constraint defined on the track).</li> <li>Everyone has a week to review the <a href="">proposal</a> for block-axis baseline. Next week the group will resolve on block-axis and then vote to publish <a href="">Grid</a>.</li> <li><b>Resolved: </b>Start a <a href="">level 4 draft</a> of Values & Units, move <code>calc</code> serialization to it, and then publish the remainder of <a href="">Values & Units 3</a> as CR.</li> </ul> <p><a href="">Full Minutes</a></p> <img src="" width="0" height="0" alt="" /> Dael Jackson CSS WG Blog Cascading Style Sheets Working Group Blog 2016-07-21T00:30:03+00:00 Video Ristretto: Rhiana Heath–Pop-up Accessibility 2016-07-20T03:09:08+00:00 <p>Modals and pop-ups can be a really useful tool for displaying additional information or getting users to enter information in a way that doesn’t clutter up your screen. However as yet (one coming soon) there is no official HTML element that lets us display modals in a consistent way. As a result screen readers, such as JAWS and NVDA, have a hard time reading them resulting in a lot of pop-ups not being accessible to people with disabilities.<br /> In this week’s video ristretto, Rhiana Heath looks at how to make modals accessible for people who use screen readers. This uses a combination of ARIA attributes and hidden text to speak with the screen reader. As well as helping of JavaScript to help with some custom keyboard control. All while keeping a pleasing look and feel for all users using JavaScript and CSS.</p> <p></p> <h4>Want more?</h4> <p Ristretto: Rhiana Heath–Pop-up Accessibility</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 Monday Profile: Rachel Andrew 2016-07-18T02:19:57+00:00 <p><img src="" alt="Rachel Andrew" />Monday Profile today again shares an interview we conducted with a <a href="">Code conference</a> speaker.</p> <p>You’ll find all these interviews (and a lot more!) in the second issue of our <a href="">Scroll Magazine</a>.</p> <p>This week, it’s with Rachel Andrew, whose <a href="">talk and workshop on CSS Grid Layouts</a> should be a conference highlight.</p> <h2>Rachel Andrew: In Person</h2> <p><strong>Q</strong> What made you decide you could do this for a living?</p> <p><strong>A</strong> Despite being the daughter of a programmer, I had no intention of working with computers. I trained in dance and music theatre and I was convinced that my future lay in the theatre somewhere. Life had different ideas and I began building websites when pregnant with my daughter in late 1996. By the time she was three years old I was proficient enough to be offered a job in a dot com company. I’m curious about how things work and not afraid to play, experiment and get things wrong. That, coupled with an ability for unpicking complex problems, has made up for my lack of formal training in computer science – though I sometimes find myself searching for the definition of something that everyone else seems to know already!</p> <p>The web is a great place to work for the polymath. Most of us aren’t sitting in cubicles working on small parts of systems – we get to build large chunks, sometimes even entire experiences. I love that there is always something new to learn and it might be in a completely different area to the last thing I studied.</p> <p><strong>Q</strong> Have you ever coded live on stage, or in front of an audience? How did it go?</p> <p><strong>A</strong> I’m not a fan of live coding in presentations, unless the presenter is truly exceptional at it. There are a few people who really have this skill, however much live coding results in fumbling through examples – often with the audience yelling out corrections to the presenter’s typos! In presentations of an hour or less I prefer to have my code on slides, that I can then talk about. I often link to fully worked examples for the audience to take a look at later. This approach lets me craft a talk of the right length that hits the things I want to share with the audience.</p> <p>In my day-long workshops I do live code, however I begin with a set of starting point files on CodePen, and we work together to build out the examples. I try to keep the typing to the minimum required to show the techniques – partly to focus on what we are learning but partly for self-preservation. Three years ago I shattered my elbow and have about 30% use of my dominant hand. Typing all day is pretty difficult for me, so I try and keep the examples streamlined.</p> <p><strong>Q</strong> How do you further develop and extend your skills? Books, courses? Noodling by yourself?</p> <p><strong>A</strong> I attend a lot of conferences, I enjoy seeing talks that are on areas I don’t do so much myself. I’m a developer, so it is interesting to sit in on a design talk; I’m not someone who uses JavaScript frameworks such as React, so it is interesting to sit in on a React or Angular talk. I find different approaches make me think about the things I do in a different way.</p> <p>In terms of CSS, I mostly learn by reading the specifications and building examples. Even where no browser implementation exists, I’ll usually build examples just to clarify how it is supposed to work in my own mind. That is where a lot of my work on CSS Grid started – I was building examples of something that didn’t yet exist in any browser and then as implementations appeared I could see if what I thought was the case, actually worked!</p> <p><strong>Q</strong> Is it better to learn HTML then CSS then JavaScript, or JavaScript then HTML then CSS, or all three at once, or something else?</p> <p><strong>A</strong> HTML and CSS, then JavaScript. You need to understand the DOM and the presentation layer that is CSS before you start using JavaScript to manipulate it. In addition, there is so much now that is part of CSS that traditionally we would have had to use JavaScript for – it is worth making sure that you aren’t using JavaScript for something we have a perfectly useful CSS property for.</p> <p><strong>Q</strong> What’s the best way to get more women coding?</p> <p><strong>A</strong> I’m not sure I have a good answer to that, however I mentioned that my father is a programmer. He was a programmer all through my childhood and worked at Newcastle University in the UK. We would sometimes go visit him at the computing lab, and there I took away the impression that programmers were mostly women. It was women I spoke to, sat amongst the giant whirring computers. It never occurred to me that this wasn’t a job for someone like me.</p> <p>I think having role models who represent the different reasons why people get into this field has to be a positive thing. Some people are genuinely interested in code, in and of itself. Others are perhaps more interested in running a business, creating products – and writing code is just the route to being able to do that. For young people to see that is I think important, and as important for young men as well as young women.</p> <p><strong>Q</strong> Frameworks. What’s your take? Are they good, bad or does it depend on how you use them?</p> <p><strong>A</strong> It absolutely depends on how you use them, that is the same for any tool. I would encourage anyone who wants to work as a professional in this business to learn HTML and CSS, understand the basics of Accessibility, and also learn a solid amount of vanilla JavaScript. The reason being that these languages and principles are pretty timeless. They will outlast your understanding of the framework of the moment, and they will enable you to make good decisions about frameworks rather than being swayed by what everyone on Twitter is saying.</p> <p>From that point, you need to look at the business requirements for the thing you are building. How much time have you available? What are the upsides of using a framework, what are the downsides? Does one outweigh the other? You can usually fairly easily make those decisions, and then be in a good position to address any potential downsides with your choice.</p> <p>My real concern with frameworks is that a complete reliance on tools and frameworks is creating abstractions to the extent that people are unable to engage with the underlying languages. This means they struggle to debug issues, as they don’t understand how to create a reduced test case without the involvement of the tool. It also means that they don’t butt up against places where our core specifications are lacking. I’d love for more people to be looking at the CSS specs for example and asking “why can’t we do x?” If folk are always working with an abstraction they are less likely to do that, instead just working with what their favourite tool gives them.</p> <p><strong>Q</strong> Tabs or spaces?</p> <p><strong>A</strong> I really don’t care. Be consistent with the rest of your team. There are better things to worry about.</p> <p><strong>Q</strong> What’s on your horizon?</p> <p><strong>A</strong> A lot of travel! I’m speaking at several conferences about Grid Layout and related CSS specifications. We’ve also got a bunch of exciting things planned for my CMS product Perch and Perch Runway. Lots to do – but I like it that way!<: Rachel Andrew</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 Minutes Telecon 2016-07-13 2016-07-14T01:02:48+00:00 <ul> <li>Anyone who has not done so should book for TPAC soon as hotels are filling up.</li> <li>The dates for the January 2017 F2F are tentatively set as the 11th, 12th, and 13th. Anyone with problems for these dates should raise their concern in the next two weeks on a call or on the mailing list.</li> <li>The spring meeting will be in Japan. On the call late April was suggested, but afterwards in IRC it was brought up that Golden Week (April 29-May 6) needs to be avoided and that there are US school holidays in that time period that may also need to be avoided. </li> <li>There was a strong desire to ensure that CSS-AAM is done as a joint effort between the APAWG and CSSWG. Rossen indicated the coordination on this was a part of the new CSSWG charter.</li> <li><b>Resolved: </b>Accept changes <a href="">proposed here</a> to have <code>fit-content</code> apply on every step of the algorithm instead of at the end.</li> <li><b>Resolved: </b>Change MQ4 to p3 from dci-p3</li> <li><b>Resolved: </b>All alpha for color functions can be <code>number</code> and <code>percentage</code></li> <li><b>Resolved: </b>Opacity also takes <code>number</code> or <code>percentage</code></li> <li><b>Resolved: </b><code>rgb</code> should be extended to allow an optional alpha. Likewise <code>hsl</code>. Pending compat analysis by TabAtkins.</li> <li>There was not a decision reached on if commas should be, should not be, or should optionally be present in <code>color</code> nor in other color functions like <code>rgb</code> and <code>hsl</code>. There were four options on the table for the group to discuss on github and revisit for voting next week. They are: <ol> <li>always require commas</li> <li>commas are optional everywhere in color functions</li> <li>commas are optional in old functions such as rbg() and drop the ones from new ones</li> <li>commas are required in old functions such as rbg() and drop the ones from new ones</li> </ol> </li> </ul> <p><a href="">Full Minutes</a></p> <img src="" width="0" height="0" alt="" /> Dael Jackson CSS WG Blog Cascading Style Sheets Working Group Blog 2016-07-21T00:30:03+00:00 W3C Web.br is the main Web conference in Brazil, organized b… 2016-07-12T18:30:04+00:00 <div><span lang="en-us" class="updated" title="2016-10-13"><span>13</span> Oct 2016</span> <a href="">W3C Web.br</a> is the main Web conference in Brazil, organized by <a href="">W3C Brazil</a>, <a href="">CGI.br</a>, <a href="">NIC.br</a> and <a href="">CEWEB.br</a>. This year's special focus is on the Web of Things and Finance. Keynote speakers include Dave Raggett and Bert Bos. (Conference in Portuguese.)</div> W3C Cascading Style Sheets 2016-07-12T18:30:04+00:00 CSS Dev Conf is a conference about CSS in San Antonio TX (US… 2016-07-12T18:30:04+00:00 <div><span lang="en-us" class="updated" title="2016-10-17"><span>17</span> Oct 2016</span> <a href="">CSS Dev Conf</a> is a conference about CSS in San Antonio TX (USA), on 17–19 October. A feature of this conference is that part of the conference program is determined by <a href="">vote.</a></div> W3C Cascading Style Sheets 2016-07-12T18:30:04+00:00 Ilya Streltsyn (Russian: Илья Стрельцын) collects surprising… 2016-07-12T00:00:00+00:00 <div><span lang="en-us" class="updated" title="2016-07-12"><span>12</span> Jul 2016</span> Ilya Streltsyn (Russian: Илья Стрельцын) collects <a href="">surprising, but beautiful things people do with CSS.</a> (He has similar examples for SVG and JavaScript.) The page is in Russian, but just follow the links from the pretty pictures, or use <a href="">Google's translation</a>.</div> W3C Cascading Style Sheets 2016-07-12T18:30:04+00:00 Monday Profile: Tim Kadlec 2016-07-11T01:51:33+00:00 <p><img src="" alt="Tim Kadlec" />It’s only a few weeks until this year’s <a href="">Code</a> conference, so Monday Profile is going to start sharing some of the interviews with our presenters you’ll see in our <a href="">Scroll: Code</a> magazine.</p> <p>We’re going to start with Tim Kadlec, web technology advocate at Akamai, and someone who knows more about the intersection of performance & responsive design than probably anyone around. </p> <p>Tim’s <a href="">Code session</a> will focus on giving users the feeling that their web experiences are fast and friction-free. Let’s find out a bit about him.</p> <h2>Tim Kadlec: In Person</h2> <p><strong>Q </strong>What made you decide you could do this for a living?</p> <p><strong>A</strong> In junior high, I saw a magazine at a local store that promised to teach you HTML for maybe $6, so I bought it and read it cover to cover. I honestly wasn’t that interested in web development. I liked to write, particularly about the history of basketball at that time, and wanted to be able to publish articles online. So I used the information in that magazine to build a very basic site full of all sorts of obnoxious animated GIFs, where I could write articles about basketball. Occasionally, I helped someone in town put together something simple as well.</p> <p>In college, I found an ad for an agency that was looking for an entry level web developer. At that point, it had never occurred to me that I could do this as a full-time job, but I called up and scheduled an interview. I basically faked my way through the whole thing. When they offered me the job, I ran to the book store and bought a few books: <em>Designing with Web Standards</em>, Meyer on CSS, <em>DOM Scripting</em> and one or two more.</p> <p>That weekend, all I did was read and code. By the time Monday came around I was at least OK enough to do the work (luckily, the agency wasn’t doing anything very advanced). Before long, I was hooked.</p> <p><strong>Q </strong>Have you ever coded live on stage, or in front of an audience? How did it go?</p> <p><strong>A</strong> No, never. I’ve seen a lot of people live code, but I can count on one hand the number of people I’ve seen do it well. I would definitely not be one of them. I’m guessing watching me make typo after typo for 45 minutes wouldn’t be particularly interesting to folks.</p> <p><strong>Q </strong>How do you further develop and extend your skills? Books, courses? Noodling by yourself?</p> <p><strong>A</strong> Videos, blog posts and books are certainly a part of it. I stubbornly hold onto my RSS feed and download a ton of talks to my computer to watch whenever I have a spare moment. The reading and video watching doesn’t do much if you don’t practise, so firing open a browser and seeing what you can build and what you can break is important.</p> <p>But if I had to say one thing more than any other that helps me, it’s that I am constantly bothering people smarter than myself with questions. Anytime I have an idea to bounce off someone, or run into something that doesn’t make sense, I fire off an email or send a message. We have a lot of smart people in our industry who are willing to share their knowledge — it’d be silly not to take advantage of it.</p> <p><strong>Q </strong>Is it better to learn HTML then CSS then JavaScript, or JavaScript then HTML then CSS, or all three at once, or something else?</p> <p><strong>A</strong> I learned it that way: HTML, CSS then JavaScript. That’s how I teach it to others as well. Markup is your base and everything else is layered on top of that, so to me it makes sense to teach the base first. As long as you start with the vanilla versions of each though, I think you’re probably OK. Jumping into a framework right away obscures a lot of core knowledge and at the end of the day it’s the core knowledge that will help you best adapt to new technologies.</p> <p><strong>Q </strong>What’s the best way to get more women coding?</p> <p><strong>A</strong> I’m not really qualified to provide the best advice here. If you really want to know how to make our industry a more welcome space for women, ask them. Listen to what they have to say and ask for clarification on things you don’t understand. There’s a lot we can do to make our community a friendly, safer space and I think it starts with being willing to listen.</p> <p><strong>Q </strong>Frameworks. What’s your take? Are they good, bad or does it depend on how you use them?</p> <p><strong>A</strong> It all depends. That’s the boring answer, but it’s true. I think it’s incredibly important to know the core language first—CSS before Sass, JavaScript before jQuery—but there’s nothing inherently bad about frameworks themselves. Abstractions can be useful, if applied with care.</p> <p>The problem I see with them in our industry is the number of people who blindly reach for them, applying framework after framework without realizing what they’re giving up in the process. You don’t always need a framework, and if you understand the core, you’ll be able to tell the difference between when you don’t and when you do.</p> <p><strong>Q </strong>Tabs or spaces?</p> <p><strong>A</strong> Tabs, but not enough to have any sort of serious debate about them. More like the kind of debate you have with friends late one night when everyone involved has had a few drinks.</p> <p><strong>Q </strong>What’s on your horizon?</p> <p><strong>A</strong> The sun.</p> <p>For the web, there’s plenty of stuff that has me excited: service workers (which I still don’t think we’ve even scratched the surface of) and the physical web stuff come to mind right away. I’m interested to see how we handle the challenges of truly going global as we adjust our sites and applications for different markets, as well as the challenge of reducing our impact on the CPU.</p> <p>Someone smarter than me pointed out that we’re increasingly becoming CPU bound in terms of performance, not network bound. It’s true, and it’s not necessarily something that has been true for very long. It’ll be interesting to see how we adjust for that new reality that we’ve created with loads of images and scripts.<: Tim Kadlec</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 Video: in conversation with Jen Simmons 2016-07-07T05:03:06+00:00 <p><img src="" alt="Jen Simmons" /><br /> <a href="">Jen Simmons</a> hosts the very popular <a href="">The Web Ahead podcast</a>, is on the W3C CSS Working Group, works as a design advocate at Mozilla, and has 20 years working on sites for the likes of CERN, the W3C and Google.</p> <p>Her current focus is layout for the Web, in particular new layout capabilities in CSS, like Flexbox and Grid, about which she speaks and writes extensively, and about which she spoke at our recent <a href="">Respond conference</a>. While Jen was in Sydney we sat down and spoke about these new layout capabilities of the Web, how being always connected changes the way our social networks have changed, and much more. It was a long, but very enjoyable chat, and I hope you enjoy it.</p> <p>As always, <a href="">the transcript is below</a>, and you can find more video conversations in this recent series, including with </p> <ul> <li><a href="">Ethan Marcotte</a></li> <li><a href="">Karen McGrane</a></li> <li><a href="">Sara Soueidan</a></li> <li><a href="">Russ Weakley</a></li> </ul> >Jen</dt> <dd>This is the first time I’ve been to Australia. </dd> <dt>John</dt> <dd>Oh that’s right, your first time you’ve been to the hemisphere. </dd> <dt>Jen</dt> <dd>Yeah. </dd> <dt>John</dt> <dd>See, Americans have a real thing about hemispheres. They invented a whole hemisphere called The Western Hemisphere. Like, it’s a big deal in America to have this Western Hemisphere, right? Whereas, it strikes me, there are two in the world. There’s the one on the top and there’s the one on the bottom. </dd> <dt>Jen</dt> <dd>Yeah, well that’s what I mean. I left the Western Hemisphere, I’ve been to the Eastern Hemisphere, but I’ve never left– </dd> <dt>John</dt> <dd>What are these things? Who ever talks on the Eastern Hemisphere? </dd> <dt>Jen</dt> <dd>Well, my grandfather had a big like a very fancy certificate on the wall that he had gotten the day that he had crossed the equator for the first time. </dd> <dt>John</dt> <dd>Was he in the Merchant Navy or something? </dd> <dt>Jen</dt> <dd>He was in, yeah, he was in the US Navy. </dd> <dt>John</dt> <dd>If he is still with us you can ask him, but he’s not still with us, there used to be terrible hazing rituals in the British Navy when people crossed, even Charles Darwin, I don’t know if he diarized it in the diaries of Journey of the Beagle, but there are these, I think there were particular offerings made to some punitive god of the, you know, anyway. </dd> <dt>Jen</dt> <dd>I have no idea, I just know that that certificate was a point of real pride. </dd> <dt>John</dt> <dd>Right. </dd> <dt>Jen</dt> <dd>And it struck me as a little kid like, “Crossing the equator is such a big deal.” So I just crossed the equator for the first time. Last night. </dd> <dt>John</dt> <dd>That’s the first time you crossed the equator? </dd> <dt>Jen</dt> <dd>Yeah. </dd> <dt>John</dt> <dd>Many years ago I lived in the UK and I had this friend who was much older I’d met there, you know, much older, he was probably my age now but this was a long time ago, and we talked about how if you thought back to the time of Chaucer, or the periods even before the train, you know 140, 150 years before that, you know I had this thought of people leaving home walking up, we were staying in this little village doing something I can’t remember quite what, and walking up the hill and looking back, perhaps for the last time in years, on their hometown as they went off to Rome for a pilgrimage or, or maybe they’re walking tradesmen who, you know, when was the next time? So even when I traveled then, this is in 1990 when I first sort of traveled for some years, people didn’t use the Web, it didn’t exist, and people barely used the internet, we called it “internet” by the way, we didn’t have the, “the” came later. But you left and you were sort of removed from your past life. You were gone. And I guess like your grandfather going in the Navy and he might have got a letter from his parents and sent a letter once every few months. Whereas now we’re always connected. And you know, you got off your plane awaiting, you know, emails and Twitter feeds and whatever. </dd> <dt>Jen</dt> <dd>Yeah, I’m texting with my neighbor to see how my dog is. </dd> <dt>John</dt> <dd>And now on the plane, you probably had wifi, and you weren’t even connnected, you weren’t even disconnected while you’re on the plane now. </dd> <dt>Jen</dt> <dd>Yeah, I didn’t turn it on. </dd> <dt>John</dt> <dd>We’re connected everywhere. </dd> <dt>Jen</dt> <dd>Yeah. </dd> <dt>John</dt> <dd>In a very short period of time we’ve gone from this idea that, for almost all of human history we would be disconnected from our networks for long periods of time. And we would therefore forge new ones. And now we’re never disconnected. I wonder what the long-term implications of that might be? </dd> <dt>Jen</dt> <dd>I dunno, it’s a radical change in the way that what it means to be a human being, and what it means to have relationships with other people. I don’t think we’ve really let that sink in. I think it’s changed very drastically in the last, even in the last 10 years. The difference between having Twitter and not having Twitter. Using RSS or going to peoples’ blogs manually verus just opening up Twitter every morning or every afternoon. </dd> <dt>John</dt> <dd>It’s almost like a push medium now. </dd> <dt>Jen</dt> <dd>Just this constant stream, constant stream, of just thousands of pieces of information. I don’t think we’ve caught up to that at all, I think it’s impacted our lives in very drastic ways and we don’t know what that is yet. </dd> <dt>John</dt> <dd>Yeah. I mean, we often worry about or are concerned with implications for business models and you know, traditional media that has been pivotal to our lives from 150 years, kinda doesn’t even know how to make money anymore in the life for this, but you know, in the context of having this sorta always-on always-connected world. But I think you’re right in observing that it actually changes about being human, which is far more important than business models and media companies, right? </dd> <dt>Jen</dt> <dd>Yeah, yeah. </dd> <dt>John</dt> <dd>You know the whole Dunbar number, if we really only really have the capacity as a human to really remember 250 or so strong connections with people. In the past, those connections would come and go over a lifetime. You would go to college, and you would then go to another place to work, and some of those things would fall away. Whereas now we sorta take all of them with us. We take all of our relationships with us where ever we go. Because they’re mostly not physical relationships, the connections aren’t, you don’t need to be in the same room or the same city as someone anymore to keep up that very strong connection. I think there are a lot of positive things about that, but I do wonder what else it means. </dd> <dt>Jen</dt> <dd>Yeah, and there’s people who’ve written a lot about his extensively, or studied it, but I feel like those of us who make websites and teach each other, and have strong ideas about how to make websites, we’re not talking about these things very much at all. And even trying to have a conversation right now about it, I feel like well, everything I might have to say about that is so infant, it’s so unpolished. </dd> <dt>John</dt> <dd>Speculative really. </dd> <dt>Jen</dt> <dd>It’s just so, kinda amateurish, when there are psychologists and sociologists who’ve studied this more extensively. Like, Sherry Turkle has some great work out, like I keep wanting to have more time in my life to slow down and to read a lot of those books, and to just– </dd> <dt>John</dt> <dd>But then there’s another Twitter feed to read. </dd> <dt>Jen</dt> <dd>Be more deliberate in my own choices about not necessarily opening up Twitter at the very beginning of the day. Waiting until lunch or something, or you know, being more deliberate about what I wanna focus on and spending time on that, and less consuming information, just pouring information in ’til I get completely overwhelmed and just get up the next day and pour more information in (laughs), and get overwhelmed and pour more information in. I mean in some ways it’s been really helpful to do that. I’ve been able to do a lot of the work that I do by doing that. But then on the hand, there’s a weird way in which I think it’s, I think we’re full. I think a lot of us are really full now, and we are ready for something else, and living our lives in a different way. </dd> <dt>John</dt> <dd>So we had the slow food sort of idea in particularly the 90s, and some other sort of slow approaches. I’m probably alluding to other people’s ideas here, like slow conversations, or slow reading, almost deliberative approaches to slowing down, as you say. </dd> <dt>Jen</dt> <dd>It’s hard because I wanna know what my friends are up to. And Twitter or other things like it give me a way to quickly keep touch with, keep track of, keep in touch with dozens of people on several different continents very very quickly. And those are real connections. But mixed in with that is also a lot of noise, and it’s that noise that can kinda get, and I don’t have time to separate all of that out. </dd> <dt>John</dt> <dd>It’s almost like you need the noise to get the signal. </dd> <dt>Jen</dt> <dd>Yeah. </dd> <dt>John</dt> <dd>And the signal is important but we actually we lose a lot by having to wade through all that noise. </dd> <dt>Jen</dt> <dd>I do see people doing things though, like opening a bunch of private Slack channels and just being in little conversations with a dozen people, five people, two dozen people, and having a lot more signal in those spaces and then spending less and less time in the spaces that are more noise and more public. Which is bad in a way, because it feels like that was one of the great things about the web, is this kind of open conversation that anybody could get involved with, and yet a lot of it’s now being private, you have to be invited to the little group, you have to know somebody, you have to be friends with them already to kinda get in the door. </dd> <dt>John</dt> <dd>Yeah, and then one of the great problems of the web is you open yourself up to ideas that, you know, you’re not simply in an echo chamber, however, as we’ve seen particularly with, particularly with a lot of women, in recent years, well, going back a long way, but certainly gaining more understanding of just how prevalent this is, you know, being exposed to horrendous attacks and vitriol. So you know, the response being, you know, we need to create walls around ourselves. But the unfortunate thing is that they will also limit positive as well as negative kind of random connections and so on. It’s almost like we flipflop between the desire for openness and then we realize the negative of that and we kind of withdraw back within our castles and then kind of sneak out again. It’s probably something we’ve seen oscillate for the last 20 years online. Interestingly enough it leads me to, I didn’t realize until very recently, you’re in Missoula now, so how long have you been there? </dd> <dt>Jen</dt> <dd>I started in August last year. </dd> <dt>John</dt> <dd>Okay, so you were there for about six months before I realized that, so (laughs). </dd> <dt>Jen</dt> <dd>Yeah. </dd> <dt>John</dt> <dd>I don’t know whether I wasn’t paying enough attention, or– </dd> <dt>Jen</dt> <dd>Or I didn’t promote it well enough (laughs). </dd> <dt>John</dt> <dd>Right.</dd> <dt>Jen</dt> <dd>Probably both. </dd> <dt>John</dt> <dd>And so your job though, in your job description, you say you’re a design advocate. </dd> <dt>Jen</dt> <dd>Designer. </dd> <dt>John</dt> <dd>So we see this term of a developer advocate used quite a bit, I think Google uses that term to some extent, and probably others as well. So you’re a design advocate. And you spend your time researching the coming revolution in graphic design, sounds like a pretty awesome job. But I wanted to start by asking well what is the coming revolution in graphic design on the web? </dd> <dt>Jen</dt> <dd>So the way I see it these days most websites are designed with a lot of variation and a lot of attention and effort put into typography, and maybe a little bit of color palette, there seems to be a lot of the style right now, the trend right now, is to not have a lot of other things going on as far as drop shadows or backgrounds, this whole flat design movement. Which may or may not stick around. But then there’s almost no attention and no conversation about page layout. It feels like everyone takes that very carefully crafted typography, that incredibly simple modern idea of visual design, and they pour it into layouts that we’ve been using for 10 or 15 years. You’ve got a header across the top of the page, you got a sidebar, you got a footer, and you got a main content column. Or maybe you’ve got like, a big chirographic or a carousel, and then you’ve got like a paragraph that’s centered, and then you have three paragraphs next to each other with icons, and then (laughs). </dd> <dt>John</dt> <dd>So basically the Bootstrap– </dd> <dt>Jen</dt> <dd>Yeah! </dd> <dt>John</dt> <dd>Style of– </dd> <dt>Jen</dt> <dd>Basically it’s like the four layouts that Bootstrap comes with. You know, a handful. There’s many a half a dozen of different layouts that we see over, and over, and over again. And recently there’s been a couple tweets actually, that have gone around. Jokes where people have said, you know, kinda made reference to how bored we are, made reference to how everybody’s doing the same thing. And those tweets, those blog posts, just blow up. Which tells me that a lot of people feel this pain right now. A lot of people are just completely bored. Part of the reason that we have those layouts is because we were doing everything with floats, CSS floats. And floats have a lotta, you know, float were never designed, that part of CSS was never designed to really do a layout. </dd> <dt>John</dt> <dd>It was discovered that could be used in that way, but it certainly wasn’t just– </dd> <dt>Jen</dt> <dd>That’s not what it was for. </dd> <dt>John</dt> <dd>What it was actually designed for was sort of cutout effects and– </dd> <dt>Jen</dt> <dd>Yeah, like having a photo and then getting text to wrap around the photo. </dd> <dt>John</dt> <dd>Which no one seems to do! </dd> <dt>Jen</dt> <dd>Right, because we’re putting everything in the column and the photo’s just all the way across. </dd> <dt>John</dt> <dd>Right. </dd> <dt>Jen</dt> <dd>But there’s some certain things about floats that have limited us. Like, for example, you can’t have a bunch of photos of different sizes and shapes all laid out on the page. You end up with all these empty blocks and empty spaces that look broken, because of the float drop problem, where floats, you get four across and the next one doesn’t go here, it goes like– </dd> <dt>John</dt> <dd>Below the line. </dd> <dt>Jen</dt> <dd>Gets caught on whichever one is the tallest one. So what did we do to solve that problem? We just made every photo a square, or we make every photo the exact same aspect ratio. Maybe it’s a rectangle, but they’re all the same height as each other, they’re all the same width as each other. Everything’s always like– </dd> <dt>John</dt> <dd>The grids a very, very simplistic grid. </dd> <dt>Jen</dt> <dd>Oh my god. </dd> <dt>John</dt> <dd>I guess that these are responses to the constraint of the technology. </dd> <dt>Jen</dt> <dd>Yes! </dd> <dt>John</dt> <dd>All design is within– </dd> <dt>Jen</dt> <dd>Part of it’s trends. And part of it’s, you know, we don’t have enough time to invent everything from scratch every time. We learn from each other, we get inspired from each other. So some of that’s normal. But a lot of it is the limitations of the CSS that we’ve had. It’s the limitations of the technology itself. And those limitations are changing right now. </dd> <dt>John</dt> <dd>So, we’ve certainly had experiments with shapes and regions. Is that something that you’ve got in mind? </dd> <dt>Jen</dt> <dd>Well yeah, I mean we have flexbox which is– </dd> <dt>John</dt> <dd>But even stepping back before we get to those very complex kinda layout systems, this print design of being able to flow text around arbitrary shapes. </dd> <dt>Jen</dt> <dd>Right. Instead of around a rectangle, you can float around a circle or a polygon. </dd> <dt>John</dt> <dd>I mean, is that the sort of thing you have in mind? </dd> <dt>Jen</dt> <dd>Yeah. I mean, there’s a lot of different pieces. Some of them are big pieces like flexbox regions and the alignment specification. Some of them are small pieces like shapes, which lets you flow text around a shape that’s not a square, you can flow it around a circle. Clip-path, which lets you cut something into something that’s not a rectangle. ‘Cause by default, every time you put anything on a page, it’s a rectangle. </dd> <dt>John</dt> <dd>Right. Well that’s the box model right there. </dd> <dt>Jen</dt> <dd>It’s the box model! Everything’s a rectangle. But before we used floats, before we used CSS, when we were using table-based layouts, we were using tables for layouts and everything was HTML, we did all kinds of stuff with circles. Remember all the circles? There were circles everywhere. And then we went to CSS– </dd> <dt>John</dt> <dd>Well also we tend to– </dd> <dt>Jen</dt> <dd>There were like, no more circles. </dd> <dt>John</dt> <dd>You know, I remember one circle was all we did, which was, you know, with the image map around, you know, it was all rendered out of terribly inaccessible– </dd> <dt>Jen</dt> <dd>Terrible JavaScript, terrible J– </dd> <dt>John</dt> <dd>Looked kinda nice, right? </dd> <dt>Jen</dt> <dd>Yeah, didn’t work in both Internet Explorer and Netscape. </dd> <dt>John</dt> <dd>When I think about the number of people whose lives were made hell ’cause they couldn’t read it, ’cause they’ve got a screen reader. </dd> <dt>Jen</dt> <dd>Yeah yeah yeah. So there were all kinds of problems with that, and (laughing) CSS is definitely better. But CSS, because it’s been limited to these boxes, so, clip-path is another one where you can have an object, maybe’s a photo, maybe it’s a pull quote, maybe it’s a box of color, and you can cut it into a trapezoid or into some kind of polygon, or into some sort of non-rectangular shape, so you can cut something into a non-rectangular shape, you can flow things around it in a non-rectangular shape. There’s a specification called initial-letter, which is gonna finally let us do– </dd> <dt>John</dt> <dd>So how’s that different from first-letter? </dd> <dt>Jen</dt> <dd>Drop caps. So first-letter the pseudo element lets you isolate the first letter without having to wrap it in a span, which is great. But once you’ve isolated that first letter, what are you gonna do with it? So, you say– </dd> <dt>John</dt> <dd>I guess the drop cap is the idea of what we’ve traditionally done with the first letter of a paragraph. </dd> <dt>Jen</dt> <dd>Right, if you wanna do a drop cap how are you, what technology are you gonna use? So then you have to apply a different size font, and maybe a different color, and maybe you make it bold, but in one browser it’s lined up perfectly, you want it to be the height of three lines of text, three paragraphs lines, so you make it all perfect in, I dunno, the browser of your choice, and then you open it in another browser and it doesn’t line up properly because the browsers don’t– </dd> <dt>John</dt> <dd>The font’s different. </dd> <dt>Jen</dt> <dd>The fonts are different. Or if the font doesn’t load or the user changes their font size or, it’s very very fragile. </dd> <dt>John</dt> <dd>That is a problem we had with absolute positioning way back in the day, and it didn’t end up being the solution we dreamt it would be because it looked perfect for the Mac, but you know, at 72 dpi, but then you go over here and the first time you ever open it, ’cause you know, owning a Mac and not a Windows machine was, was really expensive back then. I mean, the first time with this beautiful layout with absolute positioning on my Mac, and I opened it in the college Windows and was like, “Oh man.”</dd> <dt>Jen</dt> <dd>And it was all broken. </dd> <dt>John</dt> <dd>My life ended right there. </dd> <dt>Jen</dt> <dd>No, we need things that are robust and will work across a whole bunch of different places, under conditions that we can’t control and we half the time don’t even know about. So first-letter isolates that first letter but we still don’t have the technology that you need to make it big, and make it big in a robust way that’s gonna work all the time. And that’s what initial-letter does. You’re still gonna use first-letter and then you’re gonna use initial-letter. So you’ll say, “Oh, first-letter, change the font, “make it,” no not make it big, “Change the font, change the color, “maybe add a little margin to it.” But then initial-letter is a command to say “Make that letter be the height “of four lines of text, six lines of text, “two lines of text.” Or, and make it, by default it will just line up the top of the paragraph that it’s part of, but you can make it a raised letter, you can actually say, “Oh I want it to be higher.” So, “I want it to be the height of six lines, “but I want it to be only overlapping two lines, “and stick up three lines, or four lines.” It’s simple technology, but it’s gonna let us finally do drop caps and actually have it work. </dd> <dt>John</dt> <dd>Drop caps and initial-letter is I guess focusing on a very specific part of the page, but a lot of layout is really about the kind of things that we don’t see in necessarily in our phones and our smaller devices that make a lot of sense in a big device. You know, on phones we tend to have a very simple linearized kinda layout, because elements get very small very quickly. </dd> <dt>Jen</dt> <dd>Yes. Although, there still might be something that you wanna go ahead and do some layout with, something small, a diagram or some data, or you know, maybe you won’t do something fancy with a bunch of text or a bunch of photos, but maybe there’s something small that you wanna actually do some real layout with. And I also feel like maybe there are things that we would do on a very narrow screen that we haven’t been able to, so we haven’t thought of them yet. But maybe once we’re able to we’ll realize “Ah, actually there’s all these amazing ways.” Maybe we wanna use sideways scrolling, we’ve never used it before because it’s been a totally horrible experience, but maybe there’s a new way to manipulate a page and to use a page where sideways scrolling might matter. Like, I don’t know. I feel things are changing so radically we should be willing to ask ourselves those questions. Especially if you, you know, when you’re on a deadline for a specific project with a specific client, you really, you can’t go nuts. Maybe you add one little interesting new thing, or two little interesting new things, which can have a profound effect. Some of the most profound things I’ve seen or done myself have actually been technologically not that hard at all. Little tiny change. But I do think we need to make space in our lives or careers, it’s something that I’m definitely doing, to do bigger experiments and to try out some crazy stuff and see what happens. More like what we were doing before CSS came along or when CSS first came along, you know, the first decade of the web we were experimenting and trying all kinds of crazy new cool things. </dd> <dt>John</dt> <dd>The very famous Creating Killer Web Sites. </dd> <dt>Jen</dt> <dd>Yeah. </dd> <dt>John</dt> <dd>Do you remember that? </dd> <dt>Jen</dt> <dd>Yeah, I have it on my shelf. </dd> <dt>John</dt> <dd>There are definitely people watching right now who weren’t born when that book came out. I think 1996 it was the number one bestseller on Amazon, of any book, not on web design, any book. So they sold a lot of books. But if you actually go back to it and look at it, they were full of these horrendous, not all of the techniques were horrendous. You know, to get leading between lines before we had line-height, it would literally break lines into individual table rows and then add the spacing in that way. </dd> <dt>Jen</dt> <dd>Yeah. </dd> <dt>John</dt> <dd>But beyond that, you actually look at these killer designs that we just all went ape over, they’re all fluffin’ horrible (laughs). They’re really not particularly attractive designs, I guess it showed how, what came before, how impoverished from a design perspective web design was before we started working out– </dd> <dt>Jen</dt> <dd>Well you have to remember too though, that computer screen at that time were very low-fi. Like, they didn’t have nearly as many colors as we do now. Just a handful of colors. </dd> <dt>John</dt> <dd>640 by 480 was a pretty common frame. </dd> <dt>Jen</dt> <dd>Yeah, and the pixels were giant! So you’re looking at this screen of giant pixels with you know, a very limited color palette, and that’s what we were used to. </dd> <dt>John</dt> <dd>We had the web safe color palette. </dd> <dt>Jen</dt> <dd>Right, the 216 colors. And graphic design, we didn’t even call it graphic design for a while, we called it desktop publishing. And desktop publishing, the fonts that we had were like chunky and all bitmapped. </dd> <dt>John</dt> <dd>However, when it all got printed out– </dd> <dt>Jen</dt> <dd>No, it came out like that. </dd> <dt>John</dt> <dd>It looked beautiful right? </dd> <dt>Jen</dt> <dd>I mean, you know laser printed. Sometimes people were doing work that was beautiful, but there was also a lot of work that wasn’t beautiful on the print side. </dd> <dt>John</dt> <dd>Yes, I think we forget that.</dd> <dt>Jen</dt> <dd>In the 90s. </dd> <dt>John</dt> <dd>I think we look at some of the supposedly revolutionary print design of the late 80s and early 90s. It struck me as more “Oh, because we can do it, “we will do it.” </dd> <dt>Jen</dt> <dd>Yeah. </dd> <dt>John</dt> <dd>But again, that’s often experimentation as well. Like I mean, Neville Brody and the work in things like The Face magazine, it spawned you know, a million emulators. We look at it today, incredibly busy, there’d be multiple, multiple typefaces let alone weights on a single page, partly because we could for the first time. </dd> <dt>Jen</dt> <dd>Right. </dd> <dt>John</dt> <dd>It was physically possible to do that, </dd> <dt>Jen</dt> <dd>It was amazing. </dd> <dt>John</dt> <dd>And economically possible to do that. </dd> <dt>Jen</dt> <dd>Yeah, you didn’t have to buy the actual letters. </dd> <dt>John</dt> <dd>Right. Yeah, the letter set. And a lot of it was letter setted as well, and then suddenly we could do it on the Mac. I mean, this is one of these things that I know you share my great passion for, the kinda history of the web and the prehistory of the web, But I look back to this period of the late 80s and this explosion of desktop publishing creating, suddenly instead of there being a handful of magazines that were incredibly expensive to produce, there were dozens and dozens that were fragmented around popular culture, and specific sub– Not just talking about zines, which were, again, another level of kind of popularity, but actually things that end up in news agents. There was an explosion of them, because economically it became possible, and that was all driven, to be quite honest, with Mac. The Mac can illustrate well– </dd> <dt>Jen</dt> <dd>PostScript. </dd> <dt>John</dt> <dd>PageMaker and PostScript. But I think back to this cohort of kind of digital creators, were the first digital creators, writers, and editors, and illustrators, and page layers, page layout experts, who, when the web came along were ready to fill it with stuff. </dd> <dt>Jen</dt> <dd>Yeah, and those are the people who were on the web for a long time. </dd> <dt>John</dt> <dd>Because they were the people who were already using the digital tools to create. So instead of it being directed onto paper, it was directed onto the screen. And so I think there’s a reason why print has very much dominated our way of thinking about web design. </dd> <dt>Jen</dt> <dd>I’m hoping that we can get that spirit of experimentation back on the web, and try out some new things with the new layout technology. I hope that we don’t just say, “Well let’s do Bootstrap using “CSS Grid Layout Module,” (laughs). </dd> <dt>John</dt> <dd>Maybe we could go the Talmud, right which is, you know the Talmud? I’m probably mispronouncing it. </dd> <dt>Jen</dt> <dd>No I know what you mean, what’s your? </dd> <dt>John</dt> <dd>Well if you look at the page layout of a page in the Talmud, it’s incredibly complex, and a lot of people refer to it as the very earliest hypertext, because you’re embedding exegesis about a passage into another passage. Certainly by modern contemporary standards you wouldn’t necessarily call that beautiful design, but it’s very complex and rich information architecture I guess. </dd> <dt>Jen</dt> <dd>Well and there definitely was a spirit, even before the web, of you know, hypermedia, hypertext. </dd> <dt>John</dt> <dd>Oh absolutely, it’s where I came from. </dd> <dt>Jen</dt> <dd>“This is new, what is this, we could do anything, “what is this medium, let’s invent.” And a lotta academics, a lotta artists, “Let’s invent something new.” Or yeah, even a laser printer and PageMaker and a Mac, and you could make a magazine. And there was this spirit of do-it-yourself and anybody can now have a voice, and “Let’s invent something outta nothing.” </dd> <dt>John</dt> <dd>And yet now we look to– </dd> <dt>Jen</dt> <dd>Now it’s like “Oh I gotta business. “I gotta business, I need to grow “the way our VC funders want us to, “we’re gonna use Bootstrap, “we gotta test this stuff, we gotta–” Like, it’s just so, it feels like everything culturally has become so narrow and so specific. But I hope we can recapture some of that– </dd> <dt>John</dt> <dd>But maybe there are other places like 3D printing and other fields– </dd> <dt>Jen</dt> <dd>VR right now is the place where everybody’s going a little nuts and trying to, like, “What’s virtual reality? “What are we gonna do?” </dd> <dt>John</dt> <dd>So I look back to the early days of the web and I was sort of fortunate enough to have seen probably three such revolutions in my relatively long life now. In the kinda mid-to-late 70s I was quite young, but early teenage years, the rise of the pre-PC, with the first personal computers, they were expensive, the people I knew who had them tended to be doctors and lawyers and accountants who had money, but they were passionate about them. And they didn’t care that this was the future in terms of making a heap of money, They were genuine enthusiasts, and they would get together and compare their specs and so on. What drove their interest was certainly not a commercial one. We’ve talked a little bit about desktop publishing, I think it was a genuine revolution that we’ve sort of overlooked to some extent. And as I said, it was an absolutely vital precursor to the web. Because if we hadn’t had that, I don’t think we woulda had those skills and that knowledge base, and those people who could then see the web for what it was and jump into and start using it as a distribution network and a medium in of its own. And I guess, you know, those three together are revolutions that came relatively close together, 15 year period. And you know, 20 years later, as you say, we’ve had some periods of experimentation with the web but increasingly, as you say, it tends to be, you know it’s a commercial medium now. And we’re not seeing it necessarily used in that experimental way. But as I said, maybe there are other fields now like 3D printing, and you mentioned VR, where– But even then now there’s a feel with this idea well VR, with Oculus and Facebook buying it for billions, and you know, Sony, the commercial impetus certainly seems to be there. </dd> <dt>Jen</dt> <dd>It seems a bit like “VR might be the next iPhone, “we better get involved.” </dd> <dt>John</dt> <dd>“We better throw money at it,” right. </dd> <dt>Jen</dt> <dd>Yeah, “We better get there, ’cause last time “we didn’t get into mobile early enough. “We didn’t make the kind of money we could have made. “This time, if this is the new mobile, “then let’s get there sooner.” </dd> <dt>John</dt> <dd>And probably 3D printing to an extent as well. We’re seeing a lot of sorts of, I mean there’s obviously lots of money flowing in– </dd> <dt>Jen</dt> <dd>I feel like it’s already, it’s a bit, yeah. I do think though, that layout is, we have a chance with this new CSS to do amazing things with the layout. And I do think there are commercial advantages to doing that. I do think that you could have a much better design, a much fresher, get your audience to show up and go “Wait, wow, where am I? “I clicked a random link and now I wanna, “I’m interested to look more, “I’m gonna read this first article “but I’m actually gonna stick around “and look around the website more.” </dd> <dt>John</dt> <dd>We’re seeing a little bit, I mean even Bloomberg and some other major publications have certainly tried to experiment more with like kind of novel visual design. </dd> <dt>Jen</dt> <dd>New York Times has done a tremendous amount of work, and so has The Atlantic. There are a handful of publications I feel like I look at their work and I just see a healthy group of people who’ve been allowed, encouraged, and supported to experiment with their medium and figure out “How are we gonna do “news for real in the 21st Century? “What does it mean to have the ability “to embed data and live graphics “and video with gorgeous photos, “more gorgeous than any photos “we’ve ever had before, “and text with professional reporters, “professional writers, professional essayists, “and deliver that to an audience? “Let’s not just take the newspaper articles “and stick ’em on the internet, “let’s redefine what a newspaper is “based on what a computer can do.” The New York Times has been doing amazing work with that. And layout is a big part of it. </dd> <dt>John</dt> <dd>Yes. </dd> <dt>Jen</dt> <dd>A big part of what they’ve been doing. </dd> <dt>John</dt> <dd>So let’s talk a little about those technologies. Particularly I guess think about flexbox and grid layout. Now my concern with flexbox, ’cause it’s something I’ve been experimenting with in its 87 different iterations since it started, is I always have a concern about certain technologies that don’t get adopted simply because the learning curve is so significant. And my response to flexbox time and again is wow, if I’m really struggling with this, as someone who knows CSS pretty well and all these technologies pretty well, I’m not saying I’m a rocket scientist, but, you know, if I go away for three weeks and come back I find I’m starting all over again from scratch. And I know it’s probably the solution to some of the interesting things I’m trying to do. What can we do around this? Is, ultimately, flexbox like assembly? It’s a language underneath and we will use tooling on top of that? </dd> <dt>Jen</dt> <dd>No. </dd> <dt>John</dt> <dd>Or do you think it will work straight in flexbox? </dd> <dt>Jen</dt> <dd>I think that flexbox is a bit, right, so you alluded to flexbox… So here’s the thing. Some of the CSS properties are fairly simple, like initial-letter, it’s one line of code, shapes of one line of code. Lot of thinking went into that specification, lot of thinking went into what that would be. But when it actually went into a browser and then when it actually goes into a front-end developer’s brain, it’s not that complicated. There wasn’t a lot of discussion, there wasn’t a lot of debate. Flexbox needed some time for the CSS Working Group and for people who know what this medium is, the people who are inventing this medium, to try out a bunch of ideas and then change their minds and try out different idea and change their minds and try out different ideas (laughs). And when they did that with flexbox we were using prefixes. So all of that code went into browsers prefixed– </dd> <dt>John</dt> <dd>In the knowledge that it would be broken. </dd> <dt>Jen</dt> <dd>And we started using it. Like, authors, those of us who make websites started using it. It was like “This is awesome! “I’m gonna start using it right now.” I mean, that’s how I, I advocated for years, you should use prefixes. And things like using a prefix on border-radius was no big deal because border-radius didn’t change, because border-radius is just syntax for making a rounded corner, not that complicated. But with flexbox, the people who invent what the web’s going to be needed a chance to have running code in a browser, build some websites with it, and then change their minds about how that specification should work, change their minds about what that syntax should be. And that was incredibly messy, because like you said, we had to keep relearning it. If you made a website six years ago, or maybe I should say four years ago, then the code changed and you had to redo your website. Total mess. In some ways in response to that mess, they’re not inventing grid using prefixes. Grid is getting invented using flags. So, basically it’s, grid is even way more complicated than flexbox. Grid is gonna make flexbox look like a piece of cake to learn (laughs). But it’s happening all behind flags– </dd> <dt>John</dt> <dd>We’re not trying to scare anyone out there (laughs). </dd> <dt>Jen</dt> <dd>It’s just the reality! There is a certain level of messiness that came with flexbox, and learning flexbox, and feeling like “Oh I started using flexbox “too early and then I got burned.” That, I don’t think anybody should worry about anymore. </dd> <dt>John</dt> <dd>That’s more alluding to– </dd> <dt>Jen</dt> <dd>I know, I wanna get to your question, too. But I just wanna say that as a preface, ’cause I feel like I’ve seen, out there, a lot of people be like “Wow, flexbox was too hard! “And then it changed. “And now is it still changing? “I don’t know!” And then grid, “I don’t wanna get “burned like that with grid.” </dd> <dt>John</dt> <dd>Sounds a bit like me! </dd> <dt>Jen</dt> <dd>“I don’t wanna bother to learn it “until it’s already finished.” And it’s not gonna get rolled out in the same way. Grid has gone through a bunch of iterations, people have been building websites in grid behind flags. Which flag basically means is, with the prefix, if I wanted to make a website using this experimental technology, all I had to do–</dd> <dt>John</dt> <dd>You as an author are allowed to say “I want the browser to use this.” </dd> <dt>Jen</dt> <dd>Me as an author, I could say “I need this prefix,” and then every single person who ever went to the website would get that prefix experience. </dd> <dt>John</dt> <dd>Provided their browser supported that prefix. </dd> <dt>Jen</dt> <dd>With the flags, it’s on the user. So I could write the grid code, but you have to flip a button in your browser. And so I can’t then expect that every single one of my users is gonna flip a flag in a browser. </dd> <dt>John</dt> <dd>So it’s quite clearly experimental. And the reason why it’s supported is for us to learn it. </dd> <dt>Jen To learn it. And one of the disadvantages is that not enough people are messing around with it. The people who are inventing grid need more folks like you and I to try it out and to give them feedback, and to make experiments and say, “Yeah this isn’t quite done yet. “How about if we do this, how about if we do that?” Because we need more people actually trying it out to have input. But once it’s ready, once it’s done, once it comes out from behind the flag, it’s not gonna change anymore. And people can start learning it, they don’t need to wait, they’re not gonna get burned like with flexbox. So that said, it is hard to learn how to use flexbox. It is hard, it’s gonna be even harder to learn how to use grid. I think that we, lots of times, especially those of us who write this code for a living, as a front-end developer for a living, we’re used to getting a project, getting tickets, getting marching orders and saying “Okay, you’ve got two weeks, “you gotta build this, this part of the website “is your responsibility, it needs to get done “before the end of the next sprint.” And there’s not enough time in that cycle to learn something completely new. We have to set aside some time to learn these things. We have to take time to actually go off, maybe if they won’t let you do it at work then you gotta do it on the weekend on your own. But maybe everybody at work is gonna decide “You know what, we’re gonna take this project, “we coulda done it in two weeks using old technology, “but we need to learn the new technology “so we’re gonna do it with new technology “and we’re gonna give it a month, “because we’re gonna be slow “because it’s gonna be the first time we’re using it.” It’s not gonna be slow because it’s always slow, it’s just gonna be slow because it’s new. Learning responsive web design was that kind of an investment. Learning how to use CSS in the first place was that kind of investment. </dt> <dd>John</dd> <dt>I feel like certainly what you’re talking about as a model of practice, is certainly not alien to anyone who’s been doing this for a long time. </dt> <dd>Jen</dd> <dt>Yeah. </dt> <dd>John</dd> <dt>Because we’ve been through these periods of significant change in the core technologies. Whereas I think there’s, you know, despite having the rise of React and other front-end frameworks– </dt> <dd>Jen</dd> <dt>Right! (laughs)</dt> <dd>John</dd> <dt>That people learn, you know, we haven’t necessarily seen this massive upheaval like we might have done. </dt> <dd>Jen</dd> <dt>Well that’s the thing, people are putting a tremendous amount of effort into learning React or learning Angular, or changing from one to the other, or setting up Grunt, or setting up– </dt> <dd>John</dd> <dt>Or going from version one to version two. </dt> <dd>Jen</dd> <dt>Yeah! And it’s interesting that I do see a bit of resistance to learning CSS when I don’t see that kind of resistance to learning third-party tools. It like, “The third-party tools are cool! “And they’re gonna make us more efficient! “But learning CSS? “Ugh, why would you ever wanna “invest in that time?” It’s like, because CSS is gonna be around for the rest of your career! If you learn flexbox, you will use it for the rest of your career. If you learn learn React, eh, you’ll use it until the next thing comes along. </dt> <dd>John</dd> <dt>Until the next thing comes along, right. So let’s step back a bit. Because we’re talking about a whole bunch of technologies, and I think there might be, to some extent, amongst quite a lot of people, a little bit of uncertainty about what these technologies are. So I guess at heart there are two core layout technologies that are coming down the turnpike. We’ve got flexbox, and we’ve got grid. </dt> <dd>Jen</dd> <dt>Yes. </dt> <dd>John</dd> <dt>And these, naively, appear to be two technologies that more or less do the same thing, they’re both very complex, you know, compared to “Well I already know how to float this left “and float this right,” and obviously I appreciate that I might get a bit more than that, but how do these fit together? Are they designed for different things? </dt> <dd>Jen</dd> <dt>Yes. </dt> <dd>John</dd> <dt>Are they designed to work together? Is one gonna obsolete the other? What’s going on? </dt> <dd>Jen</dd> <dt>Right. I think that there’s… It’s easy to maybe thing that flexbox and grid were made by two different groups of people. </dt> <dd>John</dd> <dt>Right. </dt> <dd>Jen</dd> <dt>The way that React and Angular are. </dt> <dd>John</dd> <dt>Right. </dt> <dd>Jen</dd> <dt>You either use React or you use Angular, you don’t use both. But that’s not the case. Flexbox and grid were made by, both, very small groups of people that are either identical or overlapping. You know, it’s the same group of people who made them both. </dt> <dd>John</dd> <dt>So why have they made two things? What are each of them for? </dt> <dd>Jen</dd> <dt>And they didn’t just make two. There’s actually, I don’t know how many specs there are. I feel like every time I turn around, there’s another one that I didn’t, like I, “Oh gosh, I need to go learn.” ‘Cause there’s flexbox and grid– </dt> <dd>John</dd> <dt>And you were in the Working Group right? </dt> <dd>Jen</dd> <dt>I just joined the Working Group, (laughing) but I don’t need– Right, so there’s flexbox and grid and then there’s alignment, which I can explain in a minute, and then, what was it yesterday I learned? This morning! I got off the plane and I was reading my email and I’m like “Sizing, intrinsic and extrinsic “sizing specification.” Like, what is that? </dt> <dd>John</dd> <dt>Yeah, that’s been prefixed in browsers a while, I use that a bit. I like that. </dt> <dd>Jen</dd> <dt>There’s just, there’s a lot of, I think there’s a lotta pieces to this puzzle. The flexbox piece and the grid piece are giant pieces. </dt> <dd>John</dd> <dt>Right, they’re the biggest pieces. </dt> <dd>Jen</dd> <dt>And a lot of the others are sort of helper pieces and side pieces. </dt> <dd>John</dd> <dt>Look at the round stuff as well. </dt> <dd>Jen</dd> <dt>Round I find very exciting. Viewport, you know, I find very exciting. But in general, flexbox came first. I think its use cases are simpler. I think it is a very powerful tool, it’s more powerful than using floats and less hackey. </dt> <dd>John</dd> <dt>But is it largely with the sort of problems we have been solving, obviously a super set of that, but the kind of page level layout? Where does it sit in terms of the problem it’s trying to solve? </dt> <dd>Jen</dd> <dt>What we’ve been doing is using floats, or especially we’ve been using 12 column, where all the columns are the same width as each other, float-based, usually Sass-based, layout frameworks. Like 960 grid, and all the responsive versions of that, and Bootstrap, and all the, right. So there are all these different, I mean, every time I turn around there’s another flexbox grid framework, which is basically trying to take flexbox and make it do what 960 grid used to do, although in a responsive way. I think it’s a terrible idea. I think it’s a absolutely ridiculous idea. Because flexbox does something that’s incredibly different than 960.gs. And grid is gonna do something incredibly different than flexbox, and incredibly different than 960.gs. And I think if you really, really want to have a 12 column, float, like the kind of layout that you’d get from floats, which is like, everything on the page kinda sticks to the top and then, like changing the icons on your iOS device. You can’t put icons at the top and icons at the bottom and nothing in the middle. All the icons are always, like all your elements in your page are always up against the top of the page. It’s another thing that, that’s what you get out of something like 960.gs. You’ve no control over rows, where with grid you do. So I think there’s a mistake and one of the things we have to do, one of the things that’s hard, is we have to really change our mental models. So flexbox is good at taking something in one dimension, taking content in one dimension, and laying it out. If you had an infinitely wide browser you have a row of content that was just all in one row, your browser of course is not infinitely wide, so it’s however wide it is, and the content wraps. So you have a row and then it wraps, and you have another row and it wraps, and you have another row. But the way the browser’s thinking about it is as if it’s one long piece and it does all these calculations, flexbox is really good at like, figuring out how big things should be and what to do with the extra space. If you wanna distribute extra space in a way that’s simple, you wanna write simple code, flexbox is your tool. But when you have multiple rows, each row gets calculated completely independently of the other rows. So let’s say you’re making a word processor and you’ve got a whole bunch of buttons in a toolbar, that’s perfect for flexbox. Maybe on a big screen they’re all in one row, but on a smaller screen they start to wrap and you got three rows or something. But those buttons are all gonna fill up the space that’s available based on the rules that you give it without really knowing anything about the other rows. What we’ve been trying to do a lot, what I have used flexbox for many times, is like a bunch of photos or a bunch of, you know, you end up with like a card that’s like a photo with a headline and a teaser paragraph, and the height– </dt> <dd>John</dd> <dt>Which we normally would make identically high because– </dt> <dd>Jen</dd> <dt>Exactly. </dt> <dd>John</dd> <dt>When we flow them. But of course, as soon as you get a bit of overflow of, maybe the name of a speaker, if we look at one of our designs recently (laughs). </dt> <dd>Jen</dd> <dt>Yup. </dt> <dd>John</dd> <dt>Yeah, they have one of these double-barrel names and it’s too long and it wraps to the next line and it pushes the whole box too big and the whole line just drops out– </dt> <dd>Jen</dd> <dt>So that’s a perfect example of the limitation of the float-based systems, is that all that content, each one of those cards or whatever they are, each one of those units of stuff has to be exactly the same height. So then you end up doing dumb things like truncating your text so that every teaser paragraph is always 42 characters, because if it’s 44 characters, it’s gonna break the entire page layout. </dt> <dd>John</dd> <dt>Yes, alright. So this is exactly what flexbox is best or good for. </dt> <dd>Jen</dd> <dt>Flexbox is much better than floats because flexbox lets you, so you have a row of items. Let’s say you’ve got three of them and one of them is short, ’cause the text is short, and one of them is long, because the text is long, the one that’s the longest of the row will determine the height of the row and everything else in the row will become that height. </dt> <dd>John</dd> <dt>Ah, right right. </dt> <dd>Jen</dd> <dt>Which is awesome. But the next row gets calculated all on its own. So the next row becomes the height of the tallest thing. But what if you wanted to find the tallest one on the whole page and make them all be the same height? No, flexbox is not gonna let you do that. And the other thing about flexbox, is let’s say you have, it’s two across sometimes and when the screen’s wider it’s three across, and when the screen’s wider it’s four across. Let’s say it’s three across but you’ve got 13 objects not 12. So you’ve got three, three, three– </dt> <dd>John</dd> <dt>You are describing exactly how I layout all of the speakers for our conferences. And we want different sizes for various reasons. </dt> <dd>Jen</dd> <dt>And that bottom row, because it’s, if you have 12 then your bottom row is even. </dt> <dd>John</dd> <dt>It’s like, what do we do? We leave someone out? Do we make someone more important? Do we, what do we do here? </dt> <dd>Jen</dd> <dt>Right, because flexbox will take that bottom row and it will calculate it so that that last one, if it’s by itself, will take up the whole space. So you have three, three, three, and one. Or three, three, three, and two. And it will take that one or two and it will make it the full width. </dt> <dd>John</dd> <dt>Right, which you can’t do, for example, with an nth child selector, because may or may not want to apply that rule, depending on how much space is left. </dt> <dd>Jen</dd> <dt>If you start putting widths on everything you can control the widths. But then you have to write all these media queries to change the widths at all these different breakpoints. And the whole idea with flexbox is that you shouldn’t have to do all that work, it should just calculate it for you. So the thing that everybody’s wanted that I walked around asking all these questions trying to find the answer to, is how do you get flexbox to just know the width of the things above and just do the same thing? And the answer is you will never do that. Flexbox will never do that. What you want in that situation is grid. Because flexbox is only thinking about one dimension, and it’s only calculating each row. Or you can go the other direction, you could do columns. But then it’s only going to calculate each column with no information about the other columns. </dt> <dd>John</dd> <dt>Whereas grid, by its nature– </dt> <dd>Jen</dd> <dt>Is two-dimensional. </dt> <dd>John</dd> <dt>Right. </dt> <dd>Jen</dd> <dt>Grid, you can easily say, “Hey I got all this dynamic stuff, “I want you to automatically calculate “all these things for me. “I need you to calculate them based on “the other items that are on the page. “in both dimensions.”</dt> <dd>John</dd> <dt>Now a lot its origins is with the way Windows 8 introduced tiling, so there’s a kind of a background there. I think a lot of people involved with the tiling layout of Windows 8 home screen, they’re involved with the development of grid as well. </dt> <dd>Jen</dd> <dt>Yeah. </dt> <dd>John</dd> <dt>Isn’t that right? </dt> <dd>Jen</dd> <dt>Yeah, Microsoft came up with grid and it’s in IE and Edge actually right now, behind a prefix. I mean, I was telling you before there was no prefixes for grid and there was no early implementation that’s changed? Well okay, except for the fact (laughing)– </dt> <dd>John</dd> <dt>Except for grid (laughs). </dt> <dd>Jen</dd> <dt>Except for the very first implementation. The very first implementation is live. </dt> <dd>John</dd> <dt>It’s behind flags now. </dt> <dd>Jen</dd> <dt>It’s not behind flags. But it is behind prefixes. And if you just don’t write those prefixes then you can ignore it. And maybe at some point we’ll start using that, we’ll write something and it will… some sort of tool like an auto prefixer tool will spit out the new syntax and translate that new syntax into the old syntax. But I don’t know. I also think there’s a good chance we might just ignore the old implementation and just pretend like it’s not there. And just look for the new implementation. </dt> <dd>John</dd> <dt>Well now I guess with IE moving in that evergreen direction as well, we know that, you know, and even with Safari, the WebKit preview version’s gonna be updated every two weeks. It feels like we’re finally reaching the promise that browsers are gonna ever auto-update. And for the most part, we’ll be able to stop worrying about legacy. </dt> <dd>Jen</dd> <dt>I think the bugger’s gonna be IE11. If people have to support IE11 long into the future, nothing new, the way that I understand it, not officially but just in talking to people from Microsoft, it sounds like nothing new will ever go into IE11. </dt> <dd>John</dd> <dt>Did 11 ever get, did it even have this old version of grid in it or not? </dt> <dd>Jen</dd> <dt>It does have the old version of grid in it. Because it was like in 8 or 9 or something, it’s been around for a while. </dt> <dd>John</dd> <dt>So where are we at? Just before we wrap up, there are a lot of exciting features, where are we at in terms of the reality using it? Okay, we can play with it and that’s really important. But people gotta put food on the table as well. </dt> <dd>Jen</dd> <dt>People should use flexbox now. </dt> <dd>John</dd> <dt>Alright, so we can use it. </dt> <dd>Jen</dd> <dt>It’s better supported than border-radius. </dt> <dd>John</dd> <dt>Better supported than border-radius. So what are the big gotchas in terms of flexbox? </dt> <dd>Jen</dd> <dt>I mean, I think it doesn’t work in Opera Mini, which is a browser that people do not test it in and they should, people are obsessed about IE6 or IE8, or IE7– </dt> <dd>John</dd> <dt>But Opera Mini has many more users than those. </dt> <dd>Jen</dd> <dt>Opera Mini has way more users than IE8 ever will have. </dt> <dd>John</dd> <dt>And they’re live and everything, those users (laughs). </dt> <dd>Jen</dd> <dt>Yes, they’re using their phones right now. </dt> <dd>John</dd> <dt>As we speak, millions! </dt> <dd>Jen</dd> <dt>And then you know, a lotta CSS doesn’t work in Opera Mini. So it’s a whole other thing, people, if they don’t understand how that browser works, they should go learn about that browser and they should install it on their phone. </dt> <dd>John</dd> <dt>They should just turn off CSS every now and then and realize that that’s a lotta the world actually would prefer to see your webpage. </dt> <dd>Jen</dd> <dt>Yeah. But otherwise, I feel like flexbox, you know, if you understand how to write CSS in a progressively enhanced way so that when it doesn’t work in browsers it’s fine, because it works and doesn’t work at the same time. And you can just write it so that it’s gonna work out. Maybe you have a float-based fallback, or maybe you just have a narrower, you know, we just started doing that with media queries where we’d sorta have a simplified layout and then layer in media query-based responsive design. </dt> <dd>John</dd> <dt>What about using, say, supports? Or are we not quite there? </dt> <dd>Jen</dd> <dt>@supports is a great way to do it. So feature queries, the problem with using feature queries with flexbox is that there are browsers that support flexbox that do not support feature queries. Like Safari 8. So there’s a way in which, if you write flexbox code and then you wrap everything into a feature query there are browsers out there that should get the flexbox code that won’t, because they see the feature query, the conditional, that says “Hey,” you know, “Does this work? “Do you understand flexbox or not?” And if it says “No I don’t understand,” it won’t say “I don’t understand flexbox,” it’ll say “I don’t understand the question,” and then it will skip all that code. So I don’t know that I would use feature queries with flexbox. I mean, I started using flexbox in production on major, major, major websites, like four years ago. </dt> <dd>John</dd> <dt>Right. So like SVG, which is still, you know, it’s been well supported for a long period of time, but still have this sense it’s experimental. </dt> <dd>Jen</dd> <dt>Yeah, it’s not. Flexbox is ready to go. If you understand– </dt> <dd>John</dd> <dt>You heard that first, people. Go out there, use flexbox now. </dt> <dd>Jen</dd> <dt>Yes, yes yes yes. Grid, however, is in 0% of browsers. If you consider the Microsoft– </dt> <dd>John</dd> <dt>So you could use it in progressively enhanced way (laughs). </dt> <dd>Jen</dd> <dt>(laughing) Yeah! </dt> <dd>John</dd> <dt>Fallback to not grid. </dt> <dd>Jen</dd> <dt>If we say that that prefix old original draft in Edge in IE doesn’t exist, like if you don’t consider that part of the new implementation then it’s in 0% of browsers. So yeah, we’re not using it right now. </dt> <dd>John</dd> <dt>Except it’s behind flags in– </dt> <dd>Jen</dd> <dt>It’s behind flags in Chrome, including the current version of Chrome and Chrome Canary as well, so that’s a great place to go test it out if you want. Rachel Andrew, who’s been writing a tremendous amount about grid and teaching about it now for a couple years– </dt> <dd>John</dd> <dt>She’s gonna come do a workshop for us in July, so if you’re in Australia, she’ll be coming out here to do that in a couple of months. </dt> <dd>Jen</dd> <dt>She is a good person, if people wanna learn more, if they actually wanna learn the technology, find a video of her talking, go see her talk. She’s got a video series coming out that teaches you, not just grid and flexbox, but also all the old stuff, display:table, and floats, and– </dt> <dd>John</dd> <dt>I was always a bit surprised at the table-based displayed in–</dt> <dd>Jen</dd> <dt>Inline-block. </dt> <dd>John</dd> <dt>Kind of like, that solved a lot of our problems for us. </dt> <dd>Jen</dd> <dt>Inline-block too. We sorta skipped over inline-block. </dt> <dd>John</dd> <dt>I love inline-block. </dt> <dd>Jen</dd> <dt>We just got so fixated on like– </dt> <dd>John</dd> <dt>On floating everything, right? </dt> <dd>Jen</dd> <dt>Putting into the hands of a third party. So grid is almost, it’s also in Safari, I mean in Firefox, it’s in Firefox in the current version, in the developer’s edition behind a flag, it’s in Firefox Nightly without the flag. The easiest way to play around with grid, the easiest way to see examples in grid running, is just download Firefox Nightly and look at everything in Firefox Nightly. Then you don’t even have to go figure out where the flag is. And it’s in Safari Technical Preview? </dt> <dd>John</dd> <dt>Yup. </dt> <dd>Jen</dd> <dt>Behind prefixes. </dt> <dd>John</dd> <dt>Just launched last week I think, right? </dt> <dd>Jen</dd> <dt>Yeah. </dt> <dd>John</dd> <dt>So they have it prefixed rather than flags? </dt> <dd>Jen</dd> <dt>It’s prefixed. Safari still doesn’t have a flag. Maybe they will have flags eventually but so far– </dt> <dd>John</dd> <dt>I’ll hassle my good friends at Safari. </dt> <dd>Jen</dd> <dt>Everything’s still WebKit. Just, everybody out there, don’t only write WebKit prefixes. </dt> <dd>John</dd> <dt>Yeah. </dt> <dd>Jen</dd> <dt>If you ever write a WebKit prefix, also write the unprefixed– </dt> <dd>John</dd> <dt>Follow it up by the real one, right? </dt> <dd>Jen</dd> <dt>The real one, the un-prefixed one. Grid feels like it’s almost done. </dt> <dd>John</dd> <dt>So you sort of think like, it’d be almost like an overnight sensation? </dt> <dd>Jen</dd> <dt>Yes. </dt> <dd>John</dd> <dt>Because of the way it’s being worked on. </dt> <dd>Jen</dd> <dt>Yes. </dt> <dd>John</dd> <dt>It hasn’t sort of had these long, it started almost like, came full of stature when it started, because it’d already kinda worked in– </dt> <dd>Jen</dd> <dt>It needs like two years of baking, but we’re at like, one year and 10 months. It’s already mostly baked.</dt> <dd>John</dd> <dt>It’s like an elephant, the gestational period is quite long– </dt> <dd>Jen</dd> <dt>Nobody knew that it was baking. And because it’s in Edge already really all they need to do is update their implementation. A lot of the heavy lifting around the browser calculating how to do layout is already all there, they just need to revise it based on the new– </dt> <dd>John</dd> <dt>Syntax. </dt> <dd>Jen</dd> <dt>The new syntax. So all the browser makers are either working on it currently or they’re, or other folks are working on it for those browser makers. </dt> <dd>John</dd> <dt>It’s one of those technologies that actually has complete buy-in from all the major engines. For new– </dt> <dd>Jen</dd> <dt>Everybody’s super excited about it. </dt> <dd>John</dd> <dt>For significant new features in CSS, there’s usually one holdout. I’m not naming any names. Apple (laughs). But in this one we’re seeing buy-in right across. </dt> <dd>Jen</dd> <dt>Usually you’ll see one or two browsers really want it and put it in, and the other browsers are like “Welllll, we don’t, we don’t, “priorities, engineering, resource constraints.” </dt> <dd>John</dd> <dt>Wheras this one’s really got buy-in. </dt> <dd>Jen</dd> <dt>This is like everybody wants it right now. </dt> <dd>John</dd> <dt>That tends to be a good indication of what will really happen. I think if you get buy-in right across the engines you’re pretty safe in knowing that that thing is gonna happen. </dt> <dd>Jen</dd> <dt>The thing is though, that there’s this thing called subgrid. </dt> <dd>John</dd> <dt>Yes. Which isn’t gonna happen, I believe. </dt> <dd>Jen</dd> <dt>No, I think it is gonna happen. </dt> <dd>John</dd> <dt>Oh it is? </dt> <dd>Jen</dd> <dt>And I think it’s gonna delay grid. </dt> <dd>John</dd> <dt>Because it adds a lotta complexity from an implementation– </dt> <dd>Jen</dd> <dt>It might add a lotta complexity. </dt> <dd>John</dd> <dt>Right, okay (laughs). </dt> <dd>Jen</dd> <dt>Some implementers believe– </dt> <dd>John</dd> <dt>Certain people are saying to me that– </dt> <dd>Jen</dd> <dt>Yes, certain people believe it’s so complicated that it’s impossible and we shouldn’t even bother. But, uh. </dt> <dd>John</dd> <dt>Hey, computers can beat humans at Go now, we can do anything right? </dt> <dd>Jen</dd> <dt>Well, so here’s the deal. This is true with flexbox as well. Flexbox and grid both work, unlike the third-party frameworks, a third-party framework, you define a grid, basically any object, any part of the DOM any div, any paragraph, any aside, anything that you’ve got in the DOM you can apply a class to, or use some Sass to target, and you can lay it out on the page. With grid and flexbox, there’s this limitation that people are gonna really hate, which is you can only apply that technology to the direct children of the flex container or the grid container. So say you have an article and you said “Okay, this article is gonna be a flex container, “or this article is gonna be a grid container,” then each of the main items underneath like, the direct children of that article you can totally lay out on a grid. But none of the grandchildren can be laid out on the grid. </dt> <dd>John</dd> <dt>Right, and so subgrid would allow, would be for descended elements to be laid out on the same grid. </dt> <dd>Jen</dd> <dt>Because without subgrid, what we have to do is define a second grid, a third grid, a fourth grid. And a lot of people, especially people who are coming from the editorial design background from real graphic design, are gonna wanna not technologically implement a grid, but they’re gonna wanna design a grid. Like “Ohhh, let’s use a golden ratio for this one, “and we’ll arrange our columns in this order, “and here’s my grid for my page, “here’s my drawing, my sketch that I did, “here’s all the math. “Now we need to implement it in code.” Well you’re gonna define it multiple times, you have like a wrapper div and you define it there, and then in the article you have to redefine it, but that’s actually a percent of the outside. Like, the math is gonna get insane very quickly. </dt> <dd>John</dd> <dt>If you’re a CSS developer. </dt> <dd>Jen</dd> <dt>Yeah. It’s just gonna get messy. </dt> <dd>John</dd> <dt>So we wanna shift all that responsibility onto the browser people, it looks like? </dt> <dd>Jen</dd> <dt>We want the browser to do that work, we don’t want the humans to have to do that work. And I feel like, and a lot of people, Eric Meyer and Rachel Andrew as well, feel like a lot of really bad hacks will start to creep up. People will start stripping markout out, because they’ll say “Oh, it only works on the direct children? “And this should be a grandchild “or this should be a great grandchild–” </dt> <dd>John</dd> <dt>“But we’ll just make it a child.” </dt> <dd>Jen</dd> <dt>Yeah. “Forget it.” </dt> <dd>John</dd> <dt>Or bring it up a level. </dt> <dd>Jen</dd> <dt>“We’ll just remove all of the ARIA roles, “we’ll just remove all of the accessibility markup, “we’ll just remove all of the…” That’s terrible. </dt> <dd>John</dd> <dt>So if there’s one thing that will hold up adoption or widespread roll-out in browsers… </dt> <dd>Jen</dd> <dt>Yes. </dt> <dd>John</dd> <dt>Will be this issue of subgrids. </dt> <dd>Jen</dd> <dt>And you know, there’s a bunch of us who’ve had a debate, there are some people who think that subgrid, ’cause as subgrid has been discussed so far, it’s incredibly complicated, so “It’s getting super complicated mathematically, “maybe it’s impossible.” There are other people who think “We don’t need subgrid to be able to do “every single solitary use case, “edge case, possibility ever. “Let’s limit what’s possible with subgrid. “Let’s just think of the main use cases, “the main reason we need subgrid, “and let’s just implement a tool “that just does that and doesn’t do everything crazy ever. “Just does the two things or the three things “that we need, really really really badly.” Well, that spec hasn’t been written yet. So several people who are writing the spec have clear ideas about what they think it should be, but that’s what we need to have happen next. Those people need to actually write it down on paper, and the group needs to discuss whether or not its possible. And my hope is that a lot of the implementers who are skeptical that it’s possible or fear that it’s gonna be too hard, will look at the new ideas that haven’t been written down yet and go “Oh yeah, you know, maybe you’re right, “that wouldn’t be so hard, that we could do.” I don’t know, I don’t understand exactly how a browser implements, I don’t know how to write a browser or build a browser, (laughing) I know how to build a website. So we’ll see, we don’t know what happens, but I hope we can come up with a simplified version of subgrid that’s not so hard to implement. And I am one of the people who believes that you know, maybe we could get grid shipped this fall, but grid with a simplified subgrid, we’re gonna have to wait until next spring and we’ll have to wait until next summer, sometime in 2017. I think we should wait. I think we should wait, even though I want grid yesterday, I think we should wait six months more to get grid with subgrid from day one. </dt> <dd>John</dd> <dt>Alright. So just to wrap all this up… </dt> <dd>Jen</dd> <dt>Yes. </dt> <dd>John</dd> <dt>What we learnt is just go and use flexbox today. </dt> <dd>Jen</dd> <dt>Yes. </dt> <dd>John</dd> <dt>It’s usable, it’s shipping, it’s working, everyone’s bought into it. It brings us stuff that, especially if you’re doing lots of page layouts with floats, you can do much better, much cleaner layouts. </dt> <dd>Jen</dd> <dt>And maybe you won’t do your whole page with flexbox. Maybe you’ll use flexbox in certain pieces, and maybe you’ll still use your bigger, Bootstrap or whatever, for your main page layout. </dt> <dd>John</dd> <dt>For grid, it’s coming, there’s a lot of buy-in, there just seem to be some final implementation details that might be holding it up for some months. </dt> <dd>Jen</dd> <dt>But people could start learning it now. </dt> <dd>John</dd> <dt>Right. </dt> <dd>Jen</dd> <dt>I mean, I do think it’s gonna take time to learn, as I’ve started learning it and I still don’t understand a lot of it, as I’ve started learning it, it kind’ve blows my mind. And I’m enjoying learning it over several months, not trying to learn it all at once. So I think people should start trying to learn grid now. Because the main parts of grid are not gonna change. We know what it is, people can make stuff with it now. </dt> <dd>John</dd> <dt>Alright. </dt> <dd>Jen</dd> <dt>The other tip that I have for people is, because I think a lot of professional front-end developers these days don’t actually know how to do a layout with floats. </dt> <dd>John</dd> <dt>What are they doing!? </dt> <dd>Jen</dd> <dt>They’re using third-party tools. They’re using Bootstrap. And so I feel like that’s the other piece of homework, is go learn floats, go learn display:table– </dt> <dd>John</dd> <dt>Go look at the one true layout. </dt> <dd>Jen</dd> <dt>Go learn inline-block. </dt> <dd>John</dd> <dt>Inline-block, yeah! </dt> <dd>Jen</dd> <dt>Because those are gonna still be in our toolkit. We’re still gonna use floats, we’re gonna use floats with flexbox, with inline-block, with display:table, with grid– </dt> <dd>John</dd> <dt>I actually mostly don’t use float anymore, ’cause I find inline-block solves that problem a lot of the time. </dt> <dd>Jen</dd> <dt>I don’t think we’ll float a whole object, but we’re gonna wanna float a image and wrap text around it. </dt> <dd>John</dd> <dt>Actually use it for what it’s designed for. </dt> <dd>Jen</dd> <dt>Use it for what it’s supposed to be used for. So I don’t mean learn how to do a whole crazy thing with floats, I just mean learn what a float is. Because I think especially once we wanna use grid, we’re gonna need a fallback layout. You don’t wanna use Bootstrap for your fallback layout, you’re not gonna use grid and Bootstrap together. You’re gonna use grid and then you’re gonna write vanilla CSS for other parts of your layout, and you’re gonna need those skills. </dt> <dd>John</dd> <dt>Alright, well thank you so much Jen. There’s a bit of theme that’s come through a lot of these conversations with lots of different people over the last couple of days, the core, the basics, the foundations, they’re not going away. You know, don’t ignore those newer technologies, don’t ignore those enabling technologies that sit on top, but certainly don’t ignore the fundamental foundational technologies. As you say, they’ll be here long after we’re gone, for better or worse, but’s the reality. So it’s interesting that… (sighs) Sorry. So a message that’s come through from what you’ve said, even though we’re talking about a very new emerging technologies, it’s also come through with my conversation with Sara Soueidan and Russ Weakley and others over the last couple of days is that, you know, all these new emerging technologies are very exciting, all these layers of technology we’re working with, these third-party tools referred to are fantastic, but don’t forget the foundational elements. Everything is built on those. And it will always serve you well to know those technologies. And then built on top of them, you’ll be building a much more stable site, application, whatever your work. </dt> <dd>Jen</dd> <dt>Yeah, yeah. </dt> <dd>John</dd> <dt>Thank you so much for that. </dt> <dd>Jen</dd> <dt>Sure, thanks for having me. </dt> <dd>John</dd> <dt>You’re most welcome, and we look forward to seeing all these things in our browsers very soon. </dt> </dl> <p>The post <a rel="nofollow" href="">Video: in conversation with Jen Simmons</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 The CSS WG updated the Working Draft of Media Queries Level … 2016-07-07T00:00:00+00:00 <div><span lang="en-us" class="updated" title="2016-07-07"><span> 7</span> Jul 2016</span> The <abbr title="Cascading Style Sheets Working Group">CSS WG</abbr> updated the Working Draft of <a href=""><cite lang="en" class="notranslate">Media Queries Level 4</cite></a></div> W3C Cascading Style Sheets 2016-07-12T18:30:04+00:00 Idea of the Week: Fiona Chan 2016-07-05T01:52:59+00:00 <p><img src="" alt="Fiona Chan" />For <strong><em>Scroll: Respond</em></strong>, we asked several presenters if they’d like to write an article based on or somehow related to their conference presentation.</p> <p>We’re going to do the same with <strong><em>Scroll: Code</em></strong>, to be distributed at our Code conference (<a href="">you’re going, right?</a>), and for the next few weeks, we’re going to post a few of those articles here as Idea of the Week.</p> <p>First cab off the rank is Fiona Chan, former front end dev and lately Technical Recruiter at Lookahead Search, and one of the organisers of the SydCSS meetup group. </p> <p>Fiona’s article is on “linting” … but we’ll let her explain.</p> <h2>A Brief History of Lint</h2> <h3>Do You Lint?</h3> <p>In my presentation for Code 2016, <a href="">CSS: Code Smell Sanitation</a>, I talk about how to keep your CSS clean and free of errors. Most of the techniques I talk about are applied when everything <em>looks</em> right and has passed linting.</p> <p>Now, I’m looking forward to telling you more about that, but it occurred to me that I’ve assumed everyone knows about linting.</p> <p>Maybe that’s not the case. And it’s important that people who haven’t heard of it before, and therefore haven’t used it, feel comfortable about learning about it.</p> <p>So I’m going to write a bit here about linting, and specifically <a href="">CSSLint</a>.</p> <h3>Lint</h3> <p>Broadly, a lint tool performs static analysis of source code and flags patterns that might be errors or otherwise cause problems for the developer. Static analysis is when code is checked without actually being activated, as opposed to dynamic analysis when the software is running.</p> <p>But linting has a history.</p> <p>Back in the late 1970s, Stephen C. Johnson first developed <a href="">Lint</a> as a Unix tool that examined C language source code and pointed out code that might contain errors or be structurally unsound.</p> <p>It appeared in public in 1979 in Unix v.7, as part of the Portable C Compiler.</p> <p>The name comes from the textile fibres that accumulate on clothing and other material. If you do laundry, you’ll know lint. There’s also belly button lint – let’s not go there.</p> <p>To clean lint off a jumper or skirt, you might use a lint brush, a tool designed for that purpose. Jonhson’s Lint utility was like a lint brush for C, picking up code that looked messy or badly structured.</p> <p>From then on, most computer language compilers had a lint checker of some kind built in.</p> <p>Nowadays, lint checkers are tools that look for structural or syntactical discrepancies code in any language. For JavaScript there’s <a href="">JSLint</a>, for Python there’s <a href="">Pylint</a> and for CSS there’s <a href="">CSSLint</a>.</p> <h3>CSSLint</h3> <p><a href="">CSSLint</a> is an open source CSS code quality tool originally written by <a href="">Nicholas C. Zakas</a> and <a href="">Nicole Sullivan</a>, released in 2011.</p> <p><img class="alignnone size-full wp-image-6401" src="" alt="CSSLint screenshot" width="500" height="486" /></p> <p>As the authors say:</p> <blockquote><p.</p></blockquote> <p>The idea is that you choose which rules to apply and which problems to look for.</p> <p><img class="alignnone size-full wp-image-6402" src="" alt="CSSLint options screenshot" width="500" height="441" /></p> <p>This shows you both the comprehensiveness and the flexibility of CSSLint. You can see exactly what rules are being checked, and you can choose to implement them or not.</p> <p>Apart from anything else, it’s incredibly useful to have a checklist of what can and does go wrong in CSS.</p> <p>It is, of course, really confronting to be told everything that’s wrong with the CSS you wrote. It looked OK last time you went over it, right?</p> <p>But this is the kind of step you need to take and the kind of check you need to make – to avoid errors, to enhance site manageability and to improve page performance.</p> <p>It also doesn’t take long before many of these things stick in your head and you already address them as you work.</p> <h3>Controversy</h3> <p>CSSLint is not without its critics. Their criticisms are mostly focused on CSSLint “enforcing” rules that they feel inhibit creativity, or limit ingenuity, or are vague and arbitrary, or encourage bad practice.</p> <p>In my view, these criticisms are – by and large – not well-founded.</p> <p>The point of CSSLint is not to <em>enforce</em> any kind of policy or practice, nor is to clean your code for you. It’s designed to point out possible issues you might want to address, according to a set of rules you customise for yourself and your site.</p> <p>Even if you turn off all the rules, CSSLint is a great basic syntax checker, without having to look at validation issues. Sometimes, you just want – or need – to know that your CSS works.</p> <p>So, now when you come to my presentation (that’s <a href="">CSS: Code Smell Sanitation</a>, 3.10pm on Day 1) you’ll know what I’m talking about when I talk about what still needs to be checked <em>after</em> linting – the things even CSSLint might not catch – to keep your code smelling good.</p> <p>The post <a rel="nofollow" href="">Idea of the Week: Fiona Chan</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 The CSS WG published the first draft of CSS Color Module Lev… 2016-07-05T00:00:00+00:00 <div><span lang="en-us" class="updated" title="2016-07-05"><span> 5</span> Jul 2016</span> The <abbr title="Cascading Style Sheets Working Group">CSS WG</abbr> published the first draft of <a href=""><cite lang="en" class="notranslate">CSS Color Module Level 4</cite></a></div> W3C Cascading Style Sheets 2016-07-12T18:30:04+00:00 Video: In Conversation with Russ Weakley 2016-06-30T01:41:40+00:00 <p><img src="" alt="Russ Weakley: Dao of the Web Episode 4" width="500" height="280" class="aligncenter size-full wp-image-6391" /></p> <p>I really enjoyed these conversations we did with speakers at Respond a few weeks back, and I’m equally enjoying returning to them, editing them a little, and listening to what these wise, intelligent and generous contributors to our field have to say.</p> <p>If you’ve missed them to date, take a bit of time to listen to conversations with</p> <ul> <li><a href="">Ethan Marcotte</a></li> <li><a href="">Karen McGrane</a></li> <li><a href="">Sara Soueidan</a></li> </ul> <p>But this week we have the very first one I recorded, which I feel is entirely fitting. It’s with <a href="">Russ Weakley</a>, a huge contributor to the Web design profession not just here in Australia, but globally. It’s particularly fitting since Russ, Maxine Sherrin, Peter Firminger and I together started an event called Web Essentials back in 2004, that became Web Directions.</p> <p>We talked about accessibility, about how the role of what we now call front end developers (or do we?) has changed in the time, and what the future holds for us as Web professionals. There’s the obligatory discussion about voice interfaces, jetpacks and the future of interaction, and much more. I hope you enjoy this really great conversation with Russ Weakley.</p> <p>If you’d like to know more about Russ, <a href="">we featured him in our Monday Profile this week</a>, or why not grab a copy of the <a href="">digital edition of Scroll Magazine</a>, where the profile also appears?</p> <p>And last>John</dt> <dd>So I’m here with Russ Weakley in the very, very first- possibly last (laughs) – conversation over coffee or other beverage as it happens to be with folks who I find interesting in making great contributions and in many cases, have made great contributions over a long period of time to the web. So, Russ … Russ and I go way back and there’d be long stories around that that we can probably have over a glass of wine or a whisky.</dd> <dt>Russ</dt> <dd>1952, I think it was.</dd> <dt>John</dt> <dd>1952, that’s right. (laughing) See, young people probably think we’re not joking at that point. One of the things I’ve admired about Russ over that period of time is his focus on accessibility as a core part of the web. That’s something that since I very first met you in the early 2000s has been an important focus for you. Did something lead you to accessibility or how did that come about?</dd> <dt>Russ</dt> <dd>Yeah. Failure, dismal failure. So I think we also jumped on the web standards bandwagon in 2002, somewhere around that, and you sort of you were doing it right. When I remember going seeing my first blind user and watching them pull apart my website and the code and tell me how appalling it was and humility made me realize how badly it was written, so I suddenly decided that I had to learn it better and hooked up with people like Roger Hudson, who’s one of Sydney’s sort of penultimate accessibility gurus, but here it was just basically through realizing I knew nothing about it, and watching real users using codes. Things like that really helped.</dd> <dt>John</dt> <dd>Through the empathy for your user, and suddenly realizing I’m…</dd> <dt>Russ</dt> <dd>Well, I don’t think originally it was empathy, it was humiliation, eventually it became empathy. (laughing)</dd> <dt>John</dt> <dd>You just had to get out of the humiliation part.</dd> <dt>Russ</dt> <dd>But yeah, just watching simple things like, in those days we were obsessed with lists and realizing that this blind user was just saying, “Why are there so many lists on the page?” You know it’s simple things that you realize when you’re watching a real user that you, you know, you really need to change the way you work.</dd> <dt>John</dt> <dd>So, I guess when you or I were doing a lot of web work in the early part of the 2000’s, it was very much a point of focus, I think, we took pride in testing against the very standards for accessibility. People shared ideas about how to improve the quality of that. I generally don’t feel that that’s something that’s so important anymore to people, but what’s your thoughts about that?</dd> <dt>Russ</dt> <dd>I think it depends on who you speak to and the teams you’re in. So I think, we’re probably going to do this a lot, but it’s concept of a stack overflow developer. Do you know where you’ve heard that term, a stack overflow developer?</dd> <dt>John</dt> <dd>Absolutely, yeah I think there’s a whole book on it.</dd> <dt>Russ</dt> <dd>Oh, is there? So that there’s… Where I worked at the bank recently, there was a lot of young developers coming in, and they were handpicked to be craftsmen in the latest trends, so highly proficient in react, and could always, sort of, very modern job of script frameworks, and because these young guys, young people, just constantly on the move with these these young frameworks that are constantly changing, I think they’ve lost, there’s a big gap in basic knowledge. And it’s not just accessibility, it’s fundamental HTML, fundamental CSS practices. I would sit beside a young developer, by young, I mean, new in the field rather than ageist order, but just watching them literally have no idea about how to do basic mach up. So, their world was copying, pasting from stack overflow and constantly, agiley moving through code, but really not understanding that you couldn’t put an h1 round or div or, you know basic, things like that. So yeah, there’s somewhere along the way, just with the rapid progress of the way, we’ve lost, a lot of people just don’t understand, and also don’t appreciate, basic things like understanding what HTML is. Would you agree with that?</dd> <dt>John</dt> <dd>Look, I do, I do have a lot of empathy. I mean, when people like us started you could become a, well, you could be a world expert in CSS in about three weeks, because it was only about four weeks old. (laughing) There was a period when I probably knew more about CSS than almost anyone in the world because I had about a weeks head start. So, whereas of course, now, as you say, there’s a considerable need to learn an enormous body of knowledge, particularly around specific frameworks. And that’s partly, I guess, because people are, you know, (mumbles) is asking for expertise in specific frameworks and technologies.</dd> <dt>Russ</dt> <dd>Full stack, everything’s full stack.</dd> <dt>John</dt> <dd>Full stack, of course. But, of course, that doesn’t include, as you say, the core foundational technologies, so.</dd> <dt>Russ</dt> <dd>So the bottom of the stack is missing, that’s the problem.</dd> <dt>John</dt> <dd>Right.</dd> <dt>Russ</dt> <dd>Which is basically, HTML, no one cares about that so, the bottom of the stack I should say, you should actually also understand how a div works, unfortunately that’s not put in there.</dd> <dt>John</dt> <dd>And I guess on one level, people produce potentially fragile and not particularly stable code, and that’s bad enough, but on another level, we’re producing things that are inaccessible. And it seems to me, you know, once upon a time what we asked the web to do was pretty straight forward, right. It was to convey some basic information, it was very informational, it was marketing, communications teams with the old web, as to the extent we interacted at all was maybe to fill in a form and send it off. You know I remember, you’ll remember very well, the Sydney Olympics, when the tickets were available online, and that was a pretty complex, sort of web, what we now call application, and of course, it was inaccessible and it led to.</dd> <dt>Russ</dt> <dd>Well that was actually just tables but yeah, I know what you mean, it’s fundamentally, that one failed, but yeah, that was way before the days of rich web application.</dd> <dt>John</dt> <dd>But, whereas now, we’re asking the web to do so much more. we’re asking it to provide so much more interaction, and yet, we seem to be less and less concerned, in some ways, that it’s fundamentally accessible.</dd> <dt>Russ</dt> <dd>Inaccessible, yeah.</dd> <dt>John</dt> <dd>Yeah well, less concerned that it is (talking over each other) that it is inaccessible or that it be accessible. What are we going to do about it? What do you think, what are your thoughts about that?</dd> <dt>Russ</dt> <dd>That’s a hard one, I think, yeah you’ve got to look, I suppose, at the industry and I think there’s problems in around the way we define roles, and there’s problems in the way we understand the roles, and also just this feed, I just think that, I mean, you said off the cuff before this idea that we’ll always be in a job because there is that gap. You know, worked in banks to help people in that area because they didn’t have the skills, so on one side, you can say that it’s good that gap there, but i don’t know how to figure that, because the speed is ever going to increase. Like three weeks from now, there will be a totally new Java Script framework, and, you know the gap will get wider they’ll have to panic quicker, and they’re being asked to produce more quickly. I don’t know where we stop and try and fix the problem.</dd> <dt>John</dt> <dd>I guess one of the hopes I had is as we standardized on particular frameworks or a small number of frameworks get applied to solve specific problems, why aren’t we baking better accessibility into those. Lots of people are using Bootstrap, lots of people are using React, why is it? The more we bake accessibility into those frameworks and those libraries, surely the easier it makes accessibility, and it doesn’t seem to be what is happening.</dd> <dt>Russ</dt> <dd>Yeah, it’s a very good point, and, again, it depends on who you speak to. There are people who work with the accessibility Bootstrap would argue that Bootstrap is fundamentally accessible. Now on some level they’re right, but when you look at the way it’s applied, I mean the quickest example would be that you can apply a button class to a link or button, so that means that you could use either, so people will just slap one down and not really care, but fundamentally there’s a huge difference between a button element and a link element, they have a different purpose. The biggest one though is there’s a drop down menu and it’s a button with a drop down attached to it, and that is fundamentally inaccessible in terms of the way it’s being used. So, select menus are really hard to style so people put this button element there that looks like a really sexy, easy to style select menu, but now you’ve lost all of the accessibility, the default accessibility attached to a select menu. A lot of it comes down to the way they’re being used, rather than the core things being accessible.</dd> <dt>John</dt> <dd>However that is a core.</dd> <dt>Russ</dt> <dd>Yes, it’s a core problem still.</dd> <dt>John</dt> <dd>It’s a core piece of interaction. So, it’s something people use over and over again. So, anyway, this, I guess is our call out to people building those frameworks and libraries to really think, as much as possible, around accessibility.</dd> <dt>Russ</dt> <dd>I guess it depends where it stops though too because another example I’ve seen a lot is you make a, Bootstrap has a model, where you pop open a model, rightly or wrongly, people using models, and there is, as you said, baked in accessibility there. But people copy and paste that code, and so, for example, there’s like an array label, which is saying, this is attached to this, but if you just copy that and paste it, and don’t quite get it right, which I’ve seen people do all over the place.</dd> <dt>John</dt> <dd>You’re attaching something else. (talking over each other)</dd> <dt>Russ</dt> <dd>Which doesn’t exist, so it’s looking for a description for the model which doesn’t exist. So the people are trying, I think, to put it together, but there’s still a basic lack of understanding about simple array and what that label is doing and why it’s important. So I don’t know where it sits with the, if it’s purely with the framework developers, or education around them, or just people should know more about array, if you’re doing rich app sequence.</dd> <dt>John</dt> <dd>It does surprise me that ARIA, which I’ve been a strong advocate for, for a long time, is not as well understood, nor is widely understood, given it’s not particularly complicated, it’s technically not a complicated idea. You essentially label things with the role that they play.</dd> <dt>Russ</dt> <dd>Theoretically, yeah, but is fraught with all the perils of, you know, anything that’s began, it was introduced after WCAG 2, it wasn’t originating WCAG 2, it was introduced later so sufficiency techniques are sort of gradually coming in, which weren’t up there originally, so people that began with WCAG 2 are sort of having to relearn. And it wasn’t supported early, and it’s also got bugs. Like at the bank I sat day in day out using different screen readers in different browsers and watching all the different flaws of a simple array label, how well it was adapting. So, theoretically yes, it’s basic, but lacking. I think it’s like the early days of CSS, remember when we’d build something and you’d have to build it six ways for six browsers, (talking over each other) I think that array is still, there are parts of it that are very rock solid, but there are still parts of it that are a bit hairy around the edges, so yeah.</dd> <dt>John</dt> <dd>So it’s not magic. It’s not going to solve away our problems.</dd> <dt>Russ</dt> <dd>No, I mean there are things that are beautiful and do solve things really well, but there are things that are a little less beautiful and magical.</dd> <dt>John</dt> <dd>So I’m going to jump to something completely different. I’ve got a real thing, you know me, I have lots of things, so one of my things is voice interfaces, and if you go back to movies of the past about the future, often the way we interact with computers is using voice. Bill Gates has been obsessed with it for years. It is the future of how we’re going to interact with things, and indeed, only recently, the CEO of Microsoft talked again about the future is voice. Now obviously, on one level, you’ve worked with a lot of people and seen a lot of voice interfaces, screen readers reading to users, but not necessarily people speaking to computers. I’m just wondering, you know, what are your thoughts around voice? Is it a technology, do you think we’ll eventually replace tap and touch and typing and mousing or do you think, is it about specialized uses or is it just one of those technologies, what I call jet pack futurism, which is a vision of the future we always have, but never seems to arrive and we then sit back and think, well why don’t we have jet packs? What are your thoughts about voice?</dd> <dt>Russ</dt> <dd>Probably a lot of different things actually, I think that for some audiences it would be better. People with all the different motor skill issues, you know, they can’t move their hands or that sort of thing. Voice activation is already in place for a lot of them, but very crude.</dd> <dt>John</dt> <dd>And do you find, for example, Siri and Cortana and those other sort of technologies, are people with those sorts of disabilities, are they using those technologies. Are we seeing that happen? Is it being valuable for them?</dd> <dt>Russ</dt> <dd>Very interesting question. I’ve watched a lot of people, the the blind community, which you know, being a bit extreme here, very sort of anti Apple when it first came out, but as soon as voice over came in the uptake of IOS devices just blossomed. So, the voice over itself, got really good support, but as to theory, I haven’t actually tested that at all so I’m not sure how well supported that is.</dd> <dt>John</dt> <dd>I read recently, something a while ago i bet, again, only because it conformed to my preordained expectations and beliefs, after several years of Siri, only 15% of Apple, you know of IOS users, had even used it, let alone used it routinely. It seems to be one of those things that people don’t quite, and I’m wondering whether, is it, do people feel a bit weird talking to at inanimate object, except when watching sport, obviously, when we shout at it.</dd> <dt>Russ</dt> <dd>(laughing) Yeah, we shout at a screen.</dd> <dt>John</dt> <dd>You know I always had that vision of rooms full of like, the open plan office with all these people just talking at screens, like this babble coming out of it, (taking over each other)</dd> <dt>Russ</dt> <dd>There’s other problems as well like it’ll benefit some users, but will be problematic for others, like people who can’t talk, obviously, people who have speech impediments. You know there’s going to be all sorts of interesting… You know once you make something accessible to one group it’s going to negatively affect another group, so there will be all those, sort of, issues to run back as well.</dd> <dt>John</dt> <dd>I wonder with it too we will optimize voice recognition for certain languages because like wise,</dd> <dt>Russ</dt> <dd>American.</dd> <dt>John</dt> <dd>Yeah that’s right, we’ll be all speaking American. Every time I go to America and order a coffee, they think my name is Shawn, because John and Shawn, and so I just, if I want, to the extent that I care, if I want them to actually write my name down correctly on the Starbucks coffee,</dd> <dt>Russ</dt> <dd>You say Ja-hn.</dd> <dt>John</dt> <dd>Is I say Ja-hn, of course, so I do wonder whether we will all end up speaking with accents that will reflect the fact of what Siri or Cortana or other technologies will actually recognize.</dd> <dt>Russ</dt> <dd>I think your point about the jet pack, I just see us all sitting there going, “Open, open, open!” (laughing)</dd> <dt>John</dt> <dd>Well there’s a scene in Bladerunner, I think this is a great example.</dd> <dt>Russ</dt> <dd>Was it involving ants?</dd> <dt>John</dt> <dd>(laughing) I don’t think it’s that one. There’s a scene where he’s zooming in on a photo on a television screen, and if you watch the process, people should go and watch this, this is really, this is one of my arguments against, certainly ubiquitous use of a technology that like pinch zoom would be loop, He literally takes about a minute, because there’s no zoom, back, nope, like he’s just, He’s not even getting it wrong, it’s just the zoom in cut, and then he says crop and cut and then he prints it out.</dd> <dt>Russ</dt> <dd>I remember that scene where I found interesting is, this magical, extra pixels appeared each line after.</dd> <dt>John</dt> <dd>That’s right, like what are they using to code this thing? But it does strike me as a great example of that, sort of technology, that sort of, it demos well, it sounds really sexy but once you start actually seeing it in practice. Anyway, so I thought I’d, I’m going to ask this question of multiple people, maybe it’ll become my little stock, standard question to ask.</dd> <dt>Russ</dt> <dd>Be interesting to hear the comments.</dd> <dt>John</dt> <dd>Yeah, see what the even thoughts around it. But yeah, I have been saying for several years, I’m not convinced that we will see wide spread adoption of voice technologies. (talking over each other)</dd> <dt>Russ</dt> <dd>Are you talking in two years, five years or?</dd> <dt>John</dt> <dd>Right, right, well it’s a bit like artificial intelligence, so it’s about five years off. I certainly see in the car, for example, or even perfect example, obviously very dangerous to use, devices when looking at them and even touching them when, in theory, it’s less dangerous to talk to those devices and yet, we haven’t really seen wide spread adoption. I think there’s more investment in cars that drive themselves than controls we can just activate with our voice.</dd> <dt>Russ</dt> <dd>That makes more sense, it’s skipping the middle man, the middle man is that we are idiots as drivers.</dd> <dt>John</dt> <dd>Turn left, turn right, no, stop!</dd> <dt>Russ</dt> <dd>Fundamentally as humans we are bad drivers so, what good was that,</dd> <dt>John</dt> <dd>Oh I couldn’t agree more. but it strikes me as that is managing a more difficult problem than simply saying, “Can you turn the sound up please.”</dd> <dt>Russ</dt> <dd>But you see their logic’s like, basically, humans are wrong. Let’s go to the problem which is let’s drive the car for them.</dd> <dt>John</dt> <dd>And then we can just use our hands while we’re not watching the road.</dd> <dt>Russ</dt> <dd>See then you don’t have a problem anymore.</dd> <dt>John</dt> <dd>That’s right.</dd> <dt>Russ</dt> <dd>We can tweet while the car drives.</dd> <dt>John</dt> <dd>Yes, then we’ll all get motion sickness, and who knows, so. So you talked about that question of like, time out in the future. I always like to, sort of sometimes stop, and so, you know you and I first started talking about these things kind of over ten years ago. Does the world, or the web, feel an awful lot different to you from that time? If you were to go back to yourself back in 2002, rather than inside invest heavily in certain shares like Google, what were the things that you would alert yourself to, in terms of how the world was going to change?</dd> <dt>Russ</dt> <dd>I don’t know, its too hard a question to answer. I think fundamentally it’s so different, it’s impossible to. (background talking)</dd> <dt>John</dt> <dd>The job we did, they’re fundamentally different now, right?</dd> <dt>Russ</dt> <dd>I did a talk awhile ago and it showed this simple little diagram of what I used to do and then what it became, what it became, and that idea was that when I started there was a webmaster. I worked with a few of them, and they’re all bastards, they were horrendous human beings.</dd> <dt>John</dt> <dd>Well they identified as masters, you start there and (talking over each other)</dd> <dt>Russ</dt> <dd>They were these horrendous human beings.</dd> <dt>John</dt> <dd>Well you had to do everything, like you had to know how to do the web server.</dd> <dt>Russ</dt> <dd>Everything.</dd> <dt>John</dt> <dd>You had to know how to optimize GIFs.</dd> <dt>Russ</dt> <dd>And because they knew everything, they were arrogant.</dd> <dt>John</dt> <dd>The book was only about 150 pages. That was it, you could be the webmaster.</dd> <dt>Russ</dt> <dd>And know everything about the web. Everything about the web.</dd> <dt>John</dt> <dd>Literally from end to end.</dd> <dt>Russ</dt> <dd>So I came along in the very early days when there was no web designers and I was attached to these webmasters, who hated me, because I made their web pretty. You see what I’m saying, there were like two or three roles, and in CSS, I mean you were in it earlier than I was but it sort of gradually, bubbled up around 2000, 2001, and that became sort of like a different industry again, but then it sat for a long while, 2007 to 2008, was a long period of quiet.</dd> <dt>John</dt> <dd>So what changed that? Do you think the IPhone, IPad?</dd> <dt>Russ</dt> <dd>No, I reckon it was the abstraction of CSS, when we started to go to things you’d hate, like blueprint. You know we’d started to use frameworks that suddenly changed everything about what we did.</dd> <dt>John</dt> <dd>So how did that change? Did it make us more productive, in a sense, could we go do more and more quickly.</dd> <dt>Russ</dt> <dd>Yeah, that simple idea that instead of, literally every time you’d start a job, you’d build from the ground up. You could take this package, rightly or wrongly, unsematical, whatever, and just quickly build anything from simple websites to massively rich applications. All the interfaces were tested for you so, you know you didn’t need to browser test to the same degree.</dd> <dt>John</dt> <dd>And I guess browsers go sufficiently better that we’d never. We did spend a lot of our energy trying to make different things work across different browsers.</dd> <dt>Russ</dt> <dd>Oh yeah, actually, that’s a very good point, it was a number of factors, it’s never one thing. but I think abstraction of CSS, the frameworks, and also the sudden blossoming, everyone let go of Internet Explorer, those are the things all combined.</dd> <dt>John</dt> <dd>That sense that every website had to look the same in every browser. The reason why I brought up, particularly the iPhone, and then the iPad as well, is if you look at when responsive web design really, well got a title and took off, 2010. What’s interesting, in the previous three to four years, you had the iPhone and then the iPad. Remember the olden days, all the boss wants to talk like this and that’s (mumbles) You were always trying to install the browser you wanted the boss to use so that they didn’t look at it in the browser you didn’t want him to look at. It was always, “Oh, the boss wants “it to look the same in this.” so suddenly you put all of this effort into that because we had this idea that web has to look the same on every browser. Suddenly, I think the boss has the iPhone, that whole idea fell away, almost overnight to an extent, because it didn’t even make sense. I mean, it made sense sort of, that every browser and every, you know, roughly speaking there was 800 x 600, but the differences between, we always talked about the differences between mobile web and so on, but when it really arrived in 2007, 2008, 2009 as people started adopting smart phones. I think it went from being this abstract idea that the web could be anywhere, all these different devices and all. The stuff we talked about, even in the 90’s, actually became real, so.</dd> <dt>Russ</dt> <dd>Yeah, I suppose all this played a big part in it. It’s weird though because I still, when I was at the bank a year and a half ago, they were still trying to do pixel perfect things across browsers.</dd> <dt>John</dt> <dd>Really, and then what would happen? Was there a person who’s job it was, it’s like that pixels out of?</dd> <dt>Russ</dt> <dd>No, it was even better than that, they had written a script, this is just a staggering, there’s a script written with a bit of testing software, which is gone from my old brain, which would literally measure text screen shots against all these different browsers, and measure pixel accuracy and then could flag that this one was 15 pixels, this element was 15 pixels off.</dd> <dt>John</dt> <dd>I mean there’s value in regression testing. (talking over each other) (laughing)</dd> <dt>Russ</dt> <dd>But that was insanity.</dd> <dt>John</dt> <dd>So that, yes, so that has finally died</dd> <dt>Russ</dt> <dd>Not necessarily.</dd> <dt>John</dt> <dd>Well, yes, well hopefully.</dd> <dt>Russ</dt> <dd>That was only two years ago, that’s still there. But, yeah, I agree, fundamentally there’s been a let go, but there’s still pockets of people that are still desperately trying to hang on to the old.</dd> <dt>John</dt> <dd>You know, the one thing that is common in all of this, everything we’ve talked about, is still this piece of technology called the browser. Somehow this thing is still there. Are we always going to have browsers or is that thing?</dd> <dt>Russ</dt> <dd>My god, that’s (mumbles). I can’t answer that, you’d probably, you have more</dd> <dt>John</dt> <dd>I have thoughts about it.</dd> <dt>Russ</dt> <dd>Well what are your thoughts?</dd> <dt>John</dt> <dd>Well, I sort of think we’ll fall away. I mean, it comes down to this interesting phenomenon that we’ve also in the last, four or five years in particular, seen the rise of apps and particularly, I mean when I say apps I mean Facebook. (laughing) No really, I mean they do, and then what we’ve seen is, people kept saying these statistics are out, mobile used it. 85% of all mobile users are using apps, right? Well, if you really look at it, probably about 78% are using Facebook, but are very high percentage of that Facebook use, certainly many tens of percentages, I think, maybe as close to 30%, 40%, is actually the embedded web browser in Facebook. So people are looking at web content, into web content, but it’s in Facebook.</dd> <dt>Russ</dt> <dd>So what your essentially saying, you’re saying the browser will be there but be less obvious?</dd> <dt>John</dt> <dd>Well I think two things potentially, I have this feeling that, we’re seeing this fragmentation of platforms, like hardware and software platforms. So once upon a time there were Mac and Windows, well there’s really Windows and Mac right? Now we’ve got desktop and laptop and tablet, and within them you’ve go fragmentation. But then suddenly we’ve got wearable devices and suddenly we’ve got embedded devices in our home.</dd> <dt>Russ</dt> <dd>You forgot the fridge.</dd> <dt>John</dt> <dd>And we’ve got fridges. You’ve got all these things that, maybe they should or maybe they shouldn’t, that increasingly are internet enabled. Some of these don’t have, I mean, the classic internet fridge has got a screen and it’s a silly idea, but it’s not a silly idea to have an internet enabled fridge that might be testing air quality and temperature and reporting back to base. In the industrial world that’s been happening for 25 years right? So it seems to me, there’s two possibilities around these, and one is that we see this hyper fragmentation and if you want to deliver applications into that fragmented landscape, you just write the same application or variances of it all these different times and all these different languages. I think at some point that just breaks down. I think we’ve even seen that with wireless and android. My feeling is the web will be this layer that sits on top of that fragmentation.</dd> <dt>Russ</dt> <dd>Yeah, and in their delivery mechanism.</dd> <dt>John</dt> <dd>Yeah, and not just simply as the internet has become, people forget that there were lots of proprietary as well as well as open networks, and the internet basically became a network of networks, that sort of, almost layered over.</dd> <dt>Russ</dt> <dd>In fact, it was the information super highway.</dd> <dt>John</dt> <dd>Oh, indeed (laughing) the information super highway, which we’re still waiting for, I think. So my feeling, to answer the question that I asked you, when you kindly asked me that, I feel the browser, to some extent will fall away. the technologies of HTML, CSS, JavaScript, (mumbles) that stack of technologies will be embedded in lots of places. And maybe there are places that won’t have screens but they will still use those technologies. I mean, we’re seeing devices that basically use JavaScript in hardware as the programming.</dd> <dt>Russ</dt> <dd>I see where you’re going. You’re saying that we’ll all be in Minority Report and we’ll be throwing, with gloves, we’ll be throwing them up on.</dd> <dt>John</dt> <dd>Well that’s all a question of user experiences that I don’t necessarily, I think Minority Report is another great example of jet pack futurism. (laughing) But I am interested in what technologies, and I have been an advocate for many years that people should just learn JavaScript, because it is this enabling technology.</dd> <dt>Russ</dt> <dd>We lean up to a side note to that, one thing that I found fascinating is how that impacts people. Like I was doing testing with a guy on a big drug company site after the Facebook really has taken off, and this idea of navigation, you know like in the old days, top navigation was very common, and we tested a range of people and we found that none of them were using the top nav, and there was this weird thing, that when we asked them what it was, they had no idea. Then it hit us, their web is Facebook. There’s no concept of home, like it was this one page sort of thing with the interacting.</dd> <dt>John</dt> <dd>How old do these people tend to be?</dd> <dt>Russ</dt> <dd>These were elderly people, these were people who were testing theory and standards.</dd> <dt>John</dt> <dd>Right, were they potential people who came relatively late to the web, and they came in through (talking over each other)</dd> <dt>Russ</dt> <dd>Not sure about how far to unpack this, you can test, it was really just that, we noticed that for the first time in years, I did a lot of testing, the first time in years, this idea of a top nav had suddenly become a foreign concept, that they were much more interested in the home button and what would happen on the page, as if the page was more interactive. It was really a fascinating thing that something that was so commonly understood has possibly fallen away.</dd> <dt>John</dt> <dd>Well, because I guess it harks back to the menu bar that’s always been at the top of Windows or at the top of the screen in the Mac, whereas a mobile device, see, maybe that reflects the mobile device and the great debate about the Hamburger medium, which we won’t have today.</dd> <dt>Russ</dt> <dd>(laughing) Yes, thank God.</dd> <dt>John</dt> <dd>Which is just sort of, essentially a drawer to stuff all the features we otherwise wouldn’t. So are we moving towards a simpler model I guess, to an extent, potentially of interaction.</dd> <dt>Russ</dt> <dd>Of interaction, no, no. You were saying that everything’s breaking down, everything becomes harder.</dd> <dt>John</dt> <dd>To every bit becomes harder.</dd> <dt>Russ</dt> <dd>Yeah, and I think your point is really valid, I think there’s a period where we naively thought responsive web design, I think it’s a great thing, but it sort of began a slightly flawed mentality that one thing can do everything. And then we started to realize from a UX perspective that was incredibly flawed. If you’re on an iPhone, you need to operade in the most native way you can, regardless of how it’s built just from a UX perspective, you want it to be iPhone-esque if your on, you know like…</dd> <dt>John</dt> <dd>Yes, to reflect the platform that it is on.</dd> <dt>Russ</dt> <dd>Yeah, so that idea of one build goes everywhere just will fail more and more as we go into this world that you’re talking about.</dd> <dt>John</dt> <dd>So do you think, I mean, we’ve definitely been seeing a movement away from m-dot, style sites, towards a responsive.</dd> <dt>Russ</dt> <dd>You’d have to explain to your audience what that means.</dd> <dt>John</dt> <dd>Well I’m hoping our audience, maybe they’ll all know, like if you’re viewing this in 2075 in the far distant future.</dd> <dt>Russ</dt> <dd>I reckon there’d be a lot of people who wouldn’t know what you mean by MDOT is.</dd> <dt>John</dt> <dd>Is that because people aren’t doing that, or?</dd> <dt>Russ</dt> <dd>No, it’s gone, it’s dead.</dd> <dt>John</dt> <dd>Oh no, there’s still, a lot of sites still do it. (talking over each other) But have I made a mistake? All right, so MDOT being, of course the idea, that you sense on the service side what sort of device is come to ask for resources and you serve up completely different resources and therefore different experiences on different devices.</dd> <dt>Russ</dt> <dd>Having said that, I love, and I can’t pronounce his name, Luke Lebowski? Help me out here.</dd> <dt>John</dt> <dd>Wroblewski.</dd> <dt>Russ</dt> <dd>Thank you, I remember years ago big on responsive, and then he talked about RESS, and that changed my world, responsive and server side, because then you get the best of both worlds.</dd> <dt>John</dt> <dd>There’s really two different challenges here, there’s experience challenge, the right experience, and then there’s the engineering challenge of delivering the resources, and so, I sometimes think we sort of bundle them all together rather than unpacking those.</dd> <dt>Russ</dt> <dd>Which is why I think RESS is the ultimate solution, fundamentally it’s a responsive website at its core but you can use server side sniffing to say, “Actually, I’m going to leave a list, “I’m not going to throw all that JavaScript there.” (audio cuts off)</dd> <dt>John</dt> <dd>So Russ, you’ve been doing this a while, I’ve been doing this a while, you’ve alluded to a lot of people who’ve been in this industry a lot less time then us, and often, know a lot more, certainly in various areas, can we keep going, have we still got something to offer? Should we maybe retire, if we could afford to? What’s your feeling about, oh you know, does this really excite you, do you find you’re interested in different aspect? Where’s the next few years going to take you?</dd> <dt>Russ</dt> <dd>Yeah, well I think it’s a question, that it hits people that have been in the web for longer, more than you agree, because they’re coming out to already fitting descriptions that the web uses now, so I know I’m not a front end developer. I don’t know full stack, front to back so I can’t call myself a front end developer. I do a lot of UX and accessibility and I do parts of front end, but I can’t label myself exactly in those terms.</dd> <dt>John</dt> <dd>So, you struggle to fit into these holes in the industry.</dd> <dt>Russ</dt> <dd>I work in places where I fit, but just in pure industry standard, I don’t fit into label, and I speak to a lot of people who have grown up in our era, you know, a lot of people used to come to (mumbles) because at some point I went in a panic and thought what the hell is the future, and I rang around a whole bunch of different people, and from that same year have all found similar problems, that they, you know, they’re very confident in their skills but they’re not sure exactly where they’re fit in to these newer models. Also, to some degree, it’s like panic of at the speed it’s going will I be relevant? I haven’t had to worry as much about it because I can always switch, I do a lot of UX and private accessibility, so it’s weird that even though front end, that was my biggest passion, (mumbles) CSS,</dd> <dt>John</dt> <dd>You taught a great many people to do it well.</dd> <dt>Russ</dt> <dd>And I consider myself a front end developer, even though it staggers me how little people know about HTML and CSS, learning is now something else. It’s almost like need this other mini description, separate to what they now (mumbles) It’s a fascinating time, the world’s changed, there are times when, you know I worry about it, but generally there’s always work out there. I think I’ve been one of those who don’t quite fit into the exact roles of how all jobs are defined.</dd> <dt>John</dt> <dd>But the interesting thing is I think those who came into the web at the time we did, probably did for that very reason. We were odd creatures who sort of followed an interest when there weren’t really job descriptions and you sort of had to be master of all trades or jack of all trades at least.</dd> <dt>Russ</dt> <dd>Later, I think, you know things settled down into industries, and even that’s changing all the time. I think front end to me, is the biggest change, it’s shifted radically from where it was. UX hasn’t, you know it’s become more fun and more professional it really hasn’t fundamentally changed, but front end, in particular, and I don’t know, back end may have as well, but front end to me has radically shifted in it’s description and it’s goal.</dd> <dt>John</dt> <dd>Well here is to you fitting in for the next ten years. (laughing) I share your pain, yeah, you’ll be here for the next ten, (background talking) no, not five minutes, that you Russ for kicking off this series, which I hope will run for the next ten years but probably won’t.</dd> <dt>Russ</dt> <dd>And thanks for the flat Diet Coke. (laughing)</dd> <dt>John</dt> <dd>You are most welcome. All right, we’ll see what… </dd> </dl> <p>The post <a rel="nofollow" href="">Video: In Conversation with Russ Weakley</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 Minutes Telecon 2016-06-29 2016-06-30T00:22:41+00:00 <ul> <li><b>Resolved: </b>Accept option C: keep the tracks in the track listing, but force them to be zero-sized and suppress any gutters between adjacent collapsed tracks.</li> <li>No one has had time to fully think through the best way to address the removing restrictions on baseline-aligning things that have block-axis baselines problem, but fantasai, TabAtkins, Rossen, rachelandrew, and Mats are interested in investigating. The first step is for fantasai to add more diagrams to the spec and everyone else to review the baseline-aligning sections of the spec.</li> <li><b>Resolved: </b>Link to the compat spec to reference prefixed properties in the Snapshot and specs with relevant entires and monitor for problems in the future.</li> <li>There were five possible solutions to the potential combinatorial explosion with first and last baseline: <ol> <li>Explode alignment-baseline.</li> <li>Use last and baseline as separated keywords in align/justify-self/content as well as alignment-baseline.</li> <li>Use last-baseline in align/justify-self/content and last baseline in alignment-baseline.</li> <li>Introduce a new property to choose first vs last for vertical-align, and have last-baseline decompose to last in that property plus baseline for alignment-baseline.</li> <li>Introduce first-baseline and last-baseline to alignment-baseline(to match Align), but also allow first and last space-separated prefixes for all values of alignment-baseline(to avoid explosion). (This means that both first-baseline and first baseline would be valid)</li> </ol> <ul> <li>The group rejected options 1 & 3 and fantasai will add some examples to clarify the difference between the remaining options.</li> </ul> </li> </ul> <p><a href="">Full Minutes</a></p> <img src="" width="0" height="0" alt="" /> Dael Jackson CSS WG Blog Cascading Style Sheets Working Group Blog 2016-07-21T00:30:03+00:00 Minutes San Francisco F2F 2016-05-11 Part II: Scroll Snapping, Color, Grid, Flexbox, Inline 2016-06-29T00:05:44+00:00 <h3>Scroll Snapping</h3> <p> Archival Copy of the Change Proposal being discussed <a href="">available here</a></p> <ul> <li><b>Resolved: </b>No ability to specify the strictness of snapping separately per axis.</li> <li><b>Resolved: </b>Allow the keyword to be dropped, default to proximity.</li> <li><b>Resolved: </b>Ordering of keywords is strict in scroll-snap-type (to allow for extensions)</li> <li><b>Resolved: </b>Values are x | y | block | inline | both | point , where point would be dropped after next publication.</li> <li><b>Resolved: </b>Require (for now) an explicit axis and will gather more info as we can (to decide between physical and logical direction as the default).</li> <li><b>Resolved: </b>Make snap-align behave like a subset of background position (from <a href="">fantasai’s proposal</a>).</li> <li><b>Resolved: </b>Add section 6.2.2 (Snapping Boxes that Overflow the Scrollport) and add issues.</li> <li><b>Resolved: </b>Add section 6.2.1 (Scoping Valid Snap Positions to Visible Boxes) as an open issue</li> <li><b>Resolved: </b>Add section 6.2.3 (Unreachable Snap Areas)</li> <li><b>Resolved: </b>Merge section 6.3 (scroll-snap-stop) with an issue about whether it applies to 2D and an issue to bikeshed “normal”</li> <li><b>Resolved: </b>Merge section 7.3 (Choosing Snap Positions) with A parenthetical of “corridor” point moved to start the paragraph and JS element-targetting scrolls added into the :target paragraph</li> <li><b>Resolved: </b>Add section 7.1 after removing “explicit” “inertial” and “directional” definitions, moving the first sentence and adding a more precise definition of when an active scrolling operation is done so we know when to start snapping.</li> <li><b>Resolved: </b>Merge 7.0 (introductory text) too</li> <li><b>Resolved: </b>Add fantasai and TabAtkins as editors to scroll snapping</li> <li><b>Resolved: </b>Shortname css-snappoints -> css-scroll-snap</li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <h3>CSS Color</h3> <ul> <li>There were several actions recorded to make improvements to the spec. They were to: <ul> <li>add note explaining a reasonable range for C in <code>lch</code> to the spec</li> <li>remove commas between in the <code>color</code> examples</li> <li>fix Rec.2020 and Rec2020 to be rec2020, and DCI-P3 P3 to either (consistently) dci-p3 or p3</li> <li><code>color</code> fallback should be like font list fallback.</li> <li>add a working-color-space at-rule, which affects the entire document</li> </ul> </li> <li>The breakout session proposed resolving to publish WD for Color and MQ4.</li> <li><b>Resolved: </b>Do black point compensation when converting from profile to another.</li> <li><b>Resolved: </b>If you accurately describe the output device’s color profile in an @color-profile rule then a sane implementation will not alter your colors so this is sufficient as a replacement for device-cmyk in general and provides a good RGB fallback automatically.</li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <h3>Grid</h3> <ul> <li><b>Resolved: </b>Add allowing track list in <code>repeat</code> and auto-rows</li> <li><b>Resolved: </b>Drop named lines specified on the subgrid</li> <li><b>Resolved: </b>Publish a new WD.</li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <h3>Flexbox</h3> <ul> <li><b>Resolved: </b>Publish a new CR flexbox.</li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <h3>Inline</h3> <ul> <li><b>Resolved: </b>Publish inline</li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <img src="" width="0" height="0" alt="" /> Dael Jackson CSS WG Blog Cascading Style Sheets Working Group Blog 2016-07-21T00:30:03+00:00 Minutes San Francisco F2F 2016-05-11 Part I: Step Sizing, CSSOM View, CSS Text 3 & 4, Logical properties and margins in vertical text 2016-06-29T00:03:20+00:00 <h3>Step Sizing</h3> <ul> <li>The group reviewed Koji’s proposed spec for snap-sizing and still had a few too many concerns for FPWD. The concerns included:</li> <ul> <li>The potential for fonts rendering differently depending on OS.</li> <li>Interaction with line-grid being confusing for authors.</li> <li>That the proposal breaks the CSS design rule of being robust.</li> <li>The spec didn’t have enough use cases for the group to determine if this proposal would solve the problem-space.</li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <h3>CSSOM View</h3> <ul> <li>Brief discussion of changes for handling of empty rects in <code>getBoundingClientRects()</code> <a href="">Issue here.</a></li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <h3>CSS Text 3 & 4</h3> <ul> <li><b>Resolved: </b>Not breaking on nbsp; for the break-all value.</li> <li><b>Resolved: </b>break-all should do the same as normal for preserved spaces.</li> <li><b>Resolved: </b>break-spaces goes into overflow-wrap instead of word-break.</li> <li><b>Resolved: </b>Keep current hanging-punctuation values in Level 3.</li> <li><b>Resolved: </b>Add note that more non-CJK-relevant keywords will be added to Level 4.</li> </ul> <p> <a href="">Full Minutes</a> || Specs Referenced: <a href="">CSS Text 3</a>, <a href="">CSS Text 4</a></p> <h3>Logical properties and margins in vertical text</h3> <ul> <li><b>Resolved: </b>margin/border/padding logical properties use the element’s own writing-mode, not their parent’s writing-mode.</li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <img src="" width="0" height="0" alt="" /></ul> Dael Jackson CSS WG Blog Cascading Style Sheets Working Group Blog 2016-07-21T00:30:03+00:00 Unicode Converter v8 2016-06-28T16:50:27+00:00 <p class="floatright"><a href=""><img src="" alt="Picture of the page in action." /></a><br /><span><a href="">>> Use the converter</a></span></p> <p>An updated version of the Unicode Character Converter web app is now available. This app allows you to convert characters between various different formats and notations. </p> <p>Significant changes include the following:</p> <ul> <li>It’s now possible to generate EcmaScript6 style escapes for supplementary characters in the JavaScript output field, eg. \u{10398} rather than \uD800\uDF98.</li> <li>In many cases, clicking on a checkbox option now applies the change straight away if there is content in the associated output field. (There are 4 output fields where this doesn’t happen because we aren’t dealing with escapes and there are problems with spaces and delimiters.)</li> <li>By default, the JavaScript output no longer escapes the ASCII characters that can be represented by \n, \r, \t, \’ and \”. A new checkbox is provided to force those transformations if needed. This should make the JS transform much more useful for general conversions.</li> <li>The code to transform to HTML/XML can now replace RLI, LRI, FSI and PDI if the <samp>Convert bidi controls to HTML markup</samp> option is set.</li> <li>The code to transform to HTML/XML can convert many more invisible or ambiguous characters to escapes if the <samp>Escape invisible characters</samp> option is set.</li> <li>UTF-16 code points are all at least 4 digits long.</li> <li>Fixed a bug related to U+00A0 when converting to HTML/XML.</li> <li>The order of the output fields was changed, and various small improvements were made to the user interface.</li> <li>Revamped and updated the notes</li> </ul> <p>Many thanks to the people who wrote in with suggestions.</p> ishida blog » css r12a >> blog 2016-07-05T18:00:05+00:00 Idea of the Week: Jessica Edwards 2016-06-27T23:45:38+00:00 <p><img src="" alt="Jessica Edwards" />Jessica delivered a very well-received presentation at Respond 16 on advanced CSS image techniques, rather precociously titled “Farewell, Photoshop”. A section of this talk focused on using Blend Modes in CSS, and Jess wrote us an article on that for Scroll Magazine.</p> <p>Since CSS blend modes were also mentioned in a couple of other presenters’ talks, we figured it was worth giving the topic a bit of extra love by making it our Idea of the Week.</p> <p>You can also read Jessica’s article in the first edition of our rebooted <a href="">Scroll Magazine</a>.</p> <h3>Blend Modes in CSS</h3> <h4>What is blending?</h4> <p>Generally, when two or more pixels overlap, our screen just shows us the pixel that’s on top. If our topmost pixel has a luminosity value of 1 (white), and a pixel below it has a luminosity of 0 (black), we generally only care about the information we can get from the topmost pixel. </p> <p>Rather than let perfectly good pixels go to waste, we can opt to blend our topmost pixel with those below it. The information from the black pixel suddenly becomes useful. If you want the darkest pixel to show, you can compare the pixel’s luminosity values and return the lowest value. </p> <p>Alternatively, you could multiply these values together, and get an entirely different pixel. Scale this to dozens, hundreds, or thousands of pixels, and the result is an entirely different image!</p> <h4>blend-mode</h4> <p>Rather than getting our hands dirty and performing these calculations ourselves, CSS has been kind enough to give us 16 keywords, each representing a <code>‹blend-mode›</code>. Each <code>‹blend-mode›</code> is defined in the W3C Compositing and Blending Specification, but if you’ve ever used Adobe Photoshop, they will be very familiar.</p> <p>While each blend mode carries out unique operations, they can be broadly categorised by their resulting effect:</p> <p><img src="" alt="Normal Group" width="500" height="162" class="alignnone size-full wp-image-6383" /></p> <p><img src="" alt="Darken Group" width="500" height="159" class="alignnone size-full wp-image-6380" /></p> <p><img src="" alt="Lighten Group" width="500" height="159" class="alignnone size-full wp-image-6382" /></p> <p><img src="" alt="Contrast Group" width="500" height="160" class="alignnone size-full wp-image-6379" /></p> <p><img src="" alt="Inversion Group" width="500" height="160" class="alignnone size-full wp-image-6381" /></p> <p><img src="" alt="Component Group" width="500" height="158" class="alignnone size-full wp-image-6378" /></p> <p>Each blend mode works in the same way as Photoshop, too. This isn’t an accident: Adobe played a very active role in shaping the Compositing and Blending Specification, and subsequently bringing blend modes to the web. Remember to thank Adobe when you cancel your Adobe Creative Cloud subscription!</p> <h3>background-blend-mode</h3> <p>The <code>background-blend-mode</code> property can be used on all HTML elements. This property allows us to blend the layers of an element’s background. To get started, you will need an element with at least one <code>‹image›</code> provided via the <code>background</code> or <code>background-image</code> properties. With just one <code>background-image</code>, you will only notice an effect if you have provided a <code>‹color›</code> to the <code>background-color</code> property (because otherwise it has nothing to blend with).</p> <pre><code>background: url(‘image.jpg’), orange; background-blend-mode: exclusion;</code></pre> <p><img src="" alt="Exclusion" width="500" height="93" class="alignnone size-full wp-image-6372" /></p> <p>Rather than blend with a block of color, we can blend images as well, by specifying multiple images in our background.</p> <pre><code>background: url(‘top-image.jpg’), url(‘bottom-image.jpg'); background-blend-mode: lighten;</code></pre> <p><img src="" alt="Lighten" width="500" height="96" class="alignnone size-full wp-image-6373" /></p> <p>Just like you can provide a series of comma separated <code>‹image›</code> values to <code>background-image</code>,you can specify different <code>‹blend-mode›</code> values to <code>background-blend-mode</code>. This applies <code>lighten</code> to the first image, and <code>darken</code> to the second image. Whilst we have three layers, the bottom most layer does not have anything to blend with, so there is no need to provide a third <code>‹blend-mode›</code>.</p> <pre><code>background: url(‘top-image.jpg’), url(‘bottom-image.jpg’), orange; background-blend-mode: lighten, darken;</code></pre> <p><img src="" alt="Colour" width="500" height="96" class="alignnone size-full wp-image-6374" /></p> <h4>mix-blend-mode</h4> <p>You can use this property on any element, which means they can be used with SVG elements in addition to HTML elements. Whilst <code>background-blend-mode</code> restricts blending to within the element, <code>mix-blend-mode</code> blends different elements together.</p> <pre><code>img { mix-blend-mode: multiply; }</code></pre> <p><img src="" alt="Multiply" width="500" height="108" class="alignnone size-full wp-image-6375" /></p> <h4>What can you achieve with blend modes?</h4> <p><strong>Replicating Prototype Functionality</strong></p> <p>Perhaps the most obvious use case for blending is directly replicating a prototype given to you that uses blends. If you or a team member are comfortable with Photoshop, there is a large chance you will come across a prototype with blending between layers. Every 9/10 prototypes I come across are Photoshop files- people will use If you export an asset with a blend mode, it will not look the same in the browser. </p> <p>If the visual result is not drastically different, you can tell yourself on that no-one will notice – but sooner or later, you won’t be so lucky. I had a fairly good run, up until a certain airline logo.</p> <p>In the provided prototype, the logo casts a shadow behind it. Once exported, the result is considerably different:</p> <p><img src="" alt="Logos" width="500" height="105" class="alignnone size-full wp-image-6376" /></p> <p>Previously, if you had come across this issue, you had a few options:</p> <p>1. You, or whoever built the prototype, can go back and change the original design. Compromising on a design (especially when you don’t have to!) is frustrating in and of itself;slowing down the build time and waiting on a resolution is more so. In this situation, the prototype was provided by another company entirely.</p> <p>2. Rather than compromising the initial design, you can export both the initial asset, as well as any affected layers. The design remains intact, but potentially at the expense of the end user:more layers = larger size, more colours = higher file size. Using images of entire scenes also means that even trivial changes such as layout require a trip to an image-editing program.</p> <p>But, now we have blend modes! If your prototype uses one of 16 blend modes, you’re in luck- you don’t have to make this choice anymore. We can simply export our asset and apply the appropriate <code>‹blend-mode›</code>, rather than interrupt the development process.</p> <p><strong>Better Backgrounds</strong></p> <p>When I first started working in front-end development, backgrounds were a major pain point for me.A background takes up a huge part of your page, and whilst those beautiful, high resolution backgrounds with ~343898 colours can help set the tone of the page, I would just see hundreds of kilobytes. </p> <p>You could lower the file size by repeating the background image, but getting one to tile perfectly can be difficult to achieve. If the user instantly recognises a poorly executed pattern, their focus has been taken away from your content. It felt like a lose-lose situation.</p> <p>Nowadays, I’m much more excited by backgrounds! A very popular technique for textured backgrounds is through overlaying noise. Tiled noise by itself can be boring and as mentioned,when it is obviously repeated, it can be distracting. If we blend a small, tiled data-uri with a gradient, even when our image repeats, no tile is identical. We can have a rich, interesting, background, with even making a network request!</p> <p><img src="" alt="Texture" width="500" height="65" class="alignnone size-full wp-image-6377" /></p> <h4>What problems will you encounter?</h4> <p><strong>Stacking Context</strong></p> <p>When working with <code>mix-blend-mode</code>, the effects you will obtain depend on the order of the elements on your page. The order of elements, at least to me, is not always intuitive. There are a number of properties that can affect the order of your elements, some more obvious than others: <code>mix-blend-mode</code>, <code>position</code>, <code>transform</code>, <code>opacity</code>, <code>-webkit-overflow-scrolling</code>, <code>will-change</code> …</p> <p>When dealing with your own code, you can learn and make adjustments to the order to best suit your needs. But maybe you’re using the Latest and Greatest Framework TM, which has its own ideas about what order your elements should be? Or thinks that a <code>z-index</code> of 10,000 is appropriate? It may come down to choosing between the library or using <code>mix-blend-mode</code>, unfortunately.</p> <p>Furthermore, you may run into issues if you don’t have complete control over the environment your code will run in. I work in mobile web advertising, and I very rarely know where my work will be displayed, let alone have the ability to test it. Subsequently, for many of my projects it has been better to err on the side of safety, where I prefer to use <code>background-blend-mode</code> as its results are predictable.</p> <p><strong>Browser Support</strong></p> <p><code>background-blend-mode</code> and <code>mix-blend-mode</code> is supported by all major browsers, with the exception of Internet Explorer and Edge (with both properties under consideration for development in Edge). With OSX Safari and iOS Safari, the Component group blends (i.e. <code>hue</code>, <code>saturation</code>, <code>color</code>, and <code>luminosity</code>) are not yet supported. This is useful to know in advance, lest you toggle blend mode values whilst squinting and telling yourself that you <em>totally</em> see a subtle difference – no, no you can’t. These ones are unfortunately super fun, but so are the rest! In the meantime, you’ll get a lot of mileage out of <code>darken</code>, <code>lighten</code>, <code>screen</code> and <code>multiply</code>.</p> <p>The post <a rel="nofollow" href="">Idea of the Week: Jessica Edwards</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 Monday Profile: Russ Weakley 2016-06-27T00:23:08+00:00 <p><img src="" alt="russ weakley" />This week’s Monday profile is Russ Weakley: front end developer, web designer and trainer, with particular expertise in CSS, UX and accessibility.</p> <p>Russ spoke at our <a href="">Respond Front End Design conference</a>, and this profile first appeared in <a href="">Scroll magazine</a>.</p> <p>You can <a href="">follow Russ on Twitter</a>, and find him at <a href=""></a>.</p> <p><strong>Q</strong> Describe your family.</p> <p><strong>A</strong> I live with my long term partner, our two children and two dogs. Both my partner and I were born and raised in Sydney. </p> <p>Our oldest son is obsessed with video games of all varieties, to the point where we have to set time limits. He is also a passionate musician – playing the trombone. Our younger son is interested in a range of activities including competition swimming and dance. </p> <p><strong>Q</strong> What book has changed your life in some way?</p> <p><strong>A</strong> At different times of my life, different books have inspired me, or caused me to change how I thought about a specific topic. When I was around 20 years old a book called <em>Zen in the Martial Arts</em> by Joe Hyams was a big influence. As a print designer, many typography books helped me change the way I saw type in design. I cannot remember a lot of the earlier books, but one that comes to mind is <em>The Elements of Typographic Style</em> by Robert Bringhurst.</p> <p>When I moved into web design, a lot of books were influential but one stood out as it approached HTML and CSS in a very different way: <em>Pro CSS and HTML Design Patterns</em> by Michael Bowers. These days, I often get more inspiration from other media rather than books. I listen to a lot of podcasts and I watch a fair amount of YouTube movies on all sorts of topics from comedy to secularism and rationalism.</p> <p><strong>Q</strong> What formal qualifications do you have How did you end up doing web work?</p> <p><strong>A</strong> When I left school, I decided that I wanted to go to Art college as I was very interested in drawing and cartooning. Sadly, I did very little painting at the Art School so they decided to fob me off to a new “Design School” which was just about to start at the College. It was there that I learned about design. I learned from a grumpy typographer who constantly berated us about kerning and letter spacing. I still have nightmares about incorrectly spaced letters to this day.</p> <p>As part of the program, students had to do work experience. I refused to find my own, so the College found me a place with the Australian Museum design team. I worked there for two weeks and thought “Well, luckily I’ll never have to come back here”. Soon afterwards, I was employed by the Museum and worked there for 29 years.</p> <p><strong>Q</strong> Describe what you do. What’s your job? Is presenting at web conferences part of that job?</p> <p><strong>A</strong> My work falls into four different areas:</p> <p>1. I am a UX/UI professional. I work mainly on web applications – sketching, wireframing, prototyping, user testing etc.</p> <p>2. I am a front end developer – specialising in HTML/CSS/SCSS pattern libraries.</p> <p>3. I also work in Accessibility – often working with other developers to advise them on how to make applications more accessible.</p> <p>4. I do a fair amount of on-site training – where I work with team members to build up their skills in aspects of HTML, CSS, SCSS, Responsive Web Design and Accessibility.</p> <p><strong>Q</strong> Do you give much thought to the title you apply to yourself? Does it matter?</p> <p><strong>A</strong> It’s very hard to work out a title across these four disciplines. The closest I have seen is “UI Developer” – which theoretically covers aspects of UX/UI, design and front end. The problem is that individual teams use different titles, and they use them in different ways. There is no canonical reference point for titles. </p> <p><strong>Q</strong> Describe the first time you gave a presentation on a web topic.</p> <p><strong>A</strong> I began presenting around 2003. I think my first presentation was to a Web Standards Group meeting in Sydney on some aspect of CSS. I felt very little nerves as I had presented a lot before becoming a web designer/developer. I really enjoyed the idea that I could help people understand an topic.</p> <p><strong>Q</strong> In <em>The Graduate</em>, Mr McGuire has just one word to say to aimless college graduate Benjamin Braddock: “Plastics”. What one word would you give to today’s prospective web professional?</p> <p><strong>A</strong> Basics.</p> <p>I see many front end developers who have fast-tracked their knowledge. They can use Bootstrap and multiple different JavaScript frameworks but many lack even basic knowledge of HTML and CSS – or concepts like Progressive Enhancement.</p> <p>BONUS!</p> <p>When Russ first responded to our interview questions, he couldn’t resist having a bit of fun with the questions. Here are his original answers to the first three questions.</p> <p><strong>Q</strong> Describe your family.</p> <p><strong>A</strong> My family comes from a long line of criminals – thieves, robbers, pickpockets and the like. My father and mother actually met in jail – staring at each other across the exercise yard. They had three boys, all by accident. Our young lives were spent in and out of juvenile detention centres. It is amazing that any of us have managed to stay out of prison.</p> <p>I now have two boys of my own … well, I part-own them along with my partner. And the bank. I try to bring them up in the same way that I was brought up. Needless to say, they could shoot before they could walk and perform card tricks by the time they could speak. We have high hopes for their future.</p> <p><strong>Q</strong> What book has changed your life in some way?</p> <p><strong>A</strong> Probably the most important book I ever read was <em>Put ‘Em Down, Take ‘Em Out! Knife Fighting Techniques from Folsom Prison</em>“. It taught me many of the lessons that I still use in business meetings to this day.</p> <p><strong>Q</strong> What formal qualifications do you have How did you end up doing web work?</p> <p><strong>A</strong> Unlike my brothers, I pretty much failed high school. As we surveyed the wreckage that was my HSC score, it became apparent that there was very little I could do except go to art school. It was either that or Humanities. <: Russ Weakley</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 RealObjects released PDFreactor version 8.1, an XML-to-PDF f… 2016-06-27T00:00:00+00:00 <div><span lang="en-us" class="updated" title="2016-06-27"><span>27</span> Jun 2016</span> <a href="">RealObjects</a> released <a href="">PDFreactor</a> version 8.1, an XML-to-PDF formatter that runs either as a Web service or as a command line tool. It has support for, among other things, CSS Transforms, CSS Regions, Web Fonts, and running elements. Other features include support for HTML5 (including the <canvas> element), MathML, SVG, XSLT, JavaScript, and accessible PDF. This version adds PDF/UA, PDF/X-4p, embedded XMP and support for node.js. (Java. Free personal version)</div> W3C Cascading Style Sheets 2016-07-12T18:30:04+00:00 Minutes San Francisco F2F 2016-05-10 Part II: Page Media Query, Generated Content Spec, Report on vertical writing award website, Testing 2016-06-25T15:15:51+00:00 <h3>Page Media Query</h3> <ul> <li><b>Resolved: </b>Apply the same logic as <code>@viewport</code> has for <code>@page</code> size for viewport size.</li> </ul> <p> <a href="">Full Minutes</a> || Specs Referenced: <a href="">CSS Page</a>, <a href="">Media Queries</a></p> <h3>Generated Content Spec</h3> <ul> <li><b>Resolved: </b>Content property applies to all elements, but only lone <code>url</code> values apply to real elements–other values will be ignored.</li> <li><b>Resolved: </b>Add trailing-slash alt-text to content property.</li> <li><b>Resolved: </b>Replace <code>url</code> with <code>image</code>|<code>url</code></li> <li>This spec still isn’t friendly for accessibility, but would be a good guinea pig for doing accessibility mapping. dauwhe and Rossen will work with the editing task force and dauwhe will add a note to the spec.</li> <li><b>Resolved: </b>Drop <code>datetime</code></li> <li><b>Resolved: </b>Drop <code>document-url</code></li> <li><b>Resolved: </b>Publish new WD of Generated Content (possibly FPWD depending on patent policy needs).</li> </ul> <p> <a href="">Full Minutes</a> || <a href="">Spec Referenced</a></p> <h3>Report on vertical writing award website</h3> <ul> <li>skk presented his report on the vertical writing award website. The slides are <a href="">available here</a>.</li> </ul> <p> <a href="">Full Minutes</a> </p> <h3>Testing</h3> <ul> <li><b>Resolved: </b>All tests are added to csswg-test via GitHub PR, if implementation already reviewed push directly.</li> <li>gregwhitworth will write some basic contributer documentation.</li> <li><b>Resolved: </b>All new issues for test should be on GitHub</li> <li>gsnedders will develop a syntax for shepherd to be able to get the issues and an automatic tagging procedure and plinss will develop a way to get the GitHub test data into Shepard.</li> <li><b>Resolved: </b>Move issue-filing to GitHub in the following steps: <ol> <li>Set up mailing to receive GitHub issue notifications for archiving</li> <li>Switch to using GitHub for issue tracking</li> <li>Notify www-style</li> <li>Copy over issues filed against www-style to GitHub and reply with link. (for new issues filed after transition)</li> <li>Update specs to say that issue are filed against GitHub</li> </ol> <ul> <li>Any issues filed to the mailing list after this resolution is implemented will receive an answer from a spec author informing the individual of the new process and porting the issue over to GitHub.</li> </ul> </li> <li><b>Resolved: </b>Remove test-building aspect of build system, just build manifests.</li> </ul> <p> <a href="">Full Minutes</a> </p> <h3>Sizing</h3> <ul> <li><b>Resolved: </b>Create a new fit-content function in <a href="">Sizing Level 3</a> and <a href="">Grid</a></li> </ul> <p> <a href="">Full Minutes</a> || Specs Referenced: <a href="">Sizing Level 3</a>, <a href="">Grid</a></p> <img src="" width="0" height="0" alt="" /> Dael Jackson CSS WG Blog Cascading Style Sheets Working Group Blog 2016-07-21T00:30:03+00:00 CSS Generated Content Initial Rewrite 2016-06-24T15:08:19+00:00 <p>The CSS Working Group has published a Working Draft <a href="">CSS Generated and Replaced Content Level 3</a>. This module specifies the generated content features (<code>content</code> property and related functionality) in CSS.</p> <p>This is the first draft of a complete rewrite of this module, and is very rough. Large chunks (i.e. most) of the 2003 draft have been deleted, and major new functionality over CSS2.1 consists mainly of imports from the <a href="">GCPM</a> module. New features include:</p> <ul> <li><a href="">leaders</a> <li><a href="">cross-referenced counters</a> <li><a href="">named strings</a> <li><a href="">bookmark control</a> </li></li></li></li></ul> <p>plus a handy <a href="">new syntax</a> for alternate text: <code>content: url(sparkle.png) / "New!";</code></p> <p in the <a href="">Changes section</a>.</p> <p>Please send feedback by either <a href="">filing an issue in GitHub</a> (preferable) or sending mail to the (<a href="">archived</a>) public mailing list <a href="mailto:www-style@w3.org?Subject=%5Bcss-content%5D%20PUT%20SUBJECT%20HERE">www-style@w3.org</a> with the spec code (<code>[css-content]< CSS Scroll Snap Module Level 1 Merges Change Proposal 2016-06-24T01:59:58+00:00 <p>The CSS Working Group has published an updated Working Draft of <a href="">CSS Scroll Snap Module Level 1</a>. This module contains features to control panning and scrolling behavior with “snap positions”, to which the UA is biased to land after a scroll operation.</p> <p>This publication represents the completed merge of Tab and Fantasai’s <a href="">Change Proposal</a> that incorporates www-style <a href="">feedback</a> into Microsoft’s <a href="">CSS Snap Points Module</a> proposal championed by Matt Rakow. At this point all three editors will be working together to resolve the remaining open issues and address any further feedback on the module.</p> <p>Please send feedback by either <a href="">filing an issue in GitHub</a> (preferable) or sending mail to the (<a href="">archived</a>) public mailing list <a href="mailto:www-style@w3.org?Subject=%5Bcss-scroll-snap%5D%20PUT%20SUBJECT%20HERE">www-style@w3.org</a> with the spec code (<code>[css-scroll-snap]< Minutes Telecon 2016-06-22 2016-06-23T00:40:16+00:00 <ul> <li>astearns will input the dates he proposed on the private mailing list (<a href="">available here</a>)</li> <li><b>Resolved: </b>Publish <a href="">CSS Scroll Snap</a></li> <li><b>Resolved: </b>Line break opportunities should be controlled by the parent.</li> <li>The ‘auto’ value of <code>offset-position</code> will be written to mean do nothing to the position of the element.</li> <li>‘contain’ will be moved into <code>offset-path</code> as it’s only relevant when there’s an angle.</li> <li><b>Resolved: </b>Change the initial value of offset-rotation to 0deg.</li> <li>jihye will move the offset-* properties into the <a href="">Motion Path</a>.</li> <li><b>Resolved: </b>Rename update-frequency to update (Media Queries issue #1).</li> <li><b>Resolved: </b>Rename normal to fast (Media Queries issue #1).</li> <li><b>Resolved: </b>Move inverted colors to level 5 (Media Queries issue #8)</li> <li><b>Resolved: </b>Move custom MQ to level 5 (Media Queries issue #9).</li> <li><b>Resolved: </b>Publish a new WD of <a href="">Media Queries 4</a>.</li> <li>A decision on what happens with grid line names when dropping tracks (<a href="">issue here</a>) was deferred until next week to give people time to review.</li> <li><b>Resolved: </b><code>vertical-align: baseline</code> means first baseline except for inline-blocks (due to CSS2.1 legacy)</li> </ul> <p><a href="">Full Minutes</a></p> <img src="" width="0" height="0" alt="" /> Dael Jackson CSS WG Blog Cascading Style Sheets Working Group Blog 2016-07-21T00:30:03+00:00 Video: In Conversation with Sara Soueidan 2016-06-23T00:35:47+00:00 <p>As with <a href="">Karen McGrane</a>, <a href="">Ethan Marcotte</a>, and a number of other speakers at our recent Respond Conference whom we’ll feature in coming weeks, I had the privilege of sitting down and chatting with Sara Soueidan while she was here. We talked about how she became a speaker (great advice for anyone looking to start sharing their experience and expertise on stage), SVG (of course), and much more.</p> <p>We also recently published <a href="">our interview with Sara</a>, which first appeared in our Scroll Magazine, if you’d like to know more about her.</p> <p>Further reading and ideas</h3> <ul> <li><a href="">Rachel Andrew, “The High Price of Free” </a>. Rachel muses on the challenges experts in our field face in being asked to share their expertise for free, and the tension between the sharing nature of our Industry, the benefits of sharing, and their costs.</li> <li>Daniel Mall says we shouldn’t think “I don’t have time” but rather “<a href="">that’s not a priority</a>” </li> <li><a href="">Chris Coyier’s SVG article</a> Sara mentioned as being very influential.</li> <li><a href="">The CSS holy grail layout</a></li> <li>For the younger folks at home, just what was the “holy grail” of CSS layout?</li> <li>Want to read <a href="">Sara’s articles on SVG</a>? They’re all listed here.</li> <li>One of the most influential pieces of writing about the Web for me is <a href="">Tim Berner’s-Lee “WWW and the Web of life”</a>. To me it is mandatory reading for anyone who designs and builds things for the Web.</li> </ul> <h3 id="transcript">Transcript</h3> <dl> <dt> <h4>John</h4> </dt> <dd>So, Rachel Andrew, who writes a column in A List Apart recently, talked about the challenge of, basically, free. And how a lot of the time, people who have a profile in our industry, and often people who don’t, are kinda asked and even expected to do lots of things for free. Speaking at conferences, sharing their thoughts online. I think that it also connects with the open-source ethos and philosophy where a lot of people are devoting an enormous amount of time and rarely being particularly well recompensed. But, by the same token, I think it’s something very special and important about our industry is that we’ve collectively developed our expertise and our skills and shared that. Most people, I know, including myself, have learned a great deal from other experts who have learned something and shared it. So what are your thoughts around that dilemma? You know there are obviously benefits of giving your time, raising your profile with the opportunity, then, to perhaps publish a book or gain a client. </dd> <dt> <h4>Sara</h4> </dt> <dd>Exactly. </dd> <dt> <h4>John</h4> </dt> <dd>What are your feelings around that whole issue? </dd> <dt> <h4>Sara</h4> </dt> <dd>I don’t have anything particularly against it, if you get to do it on your own account. For example, if I have some time and I feel like writing, I write. If, like, you know, recently I read this article by Daniel Mall, where he talks about the difference between being busy and between setting priorities. So, instead of saying, “Okay, I’m too busy to do this,” you shift your mindset and you think, “This is not a priority.” So, when you don’t have a lot of work to do, which is what I used to be like the first year when I started out. I spent a lot of my time learning and I loved writing and I loved teaching so I spent a big part of my time writing as well. So, whenever I learned something, I shared it, I wrote an article. People liked the way I write my stuff and sort of related with it, so I kept doing it for awhile. And there’s this beautiful sense of satisfaction when someone comes, for example, sends you a Tweet or email and says, “Thank you, your article gave me this ah-ha moment and I finally understood the concept that I couldn’t understand before.” This is very satisfactory and sometimes this is enough for me to do what I do. But, in the last, like, few months actually, it only started maybe in September last year, I started setting priorities like Daniel said and ever since then, I’ve been writing less. I’ve also been speaking for free less. I used to speak, I spent my entire first year, probably, speaking for free. But then, I also used to make the mistake of making a new talk for every single conference. </dd> <dt> <h4>John</h4> </dt> <dd>Yes, that’s a good habit to break. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah, I definitely broke that. So, there are definitely disadvantages to that. But if you have the time, and it helps you build your profile, it helps you get connected to people, then definitely I don’t have anything against that. But, people on the other side, people who are receiving your stuff, they shouldn’t set expectations that you might not be able to meet. Like, I see a lot of, for example, I’m one of the people, I’m pretty sure there’s gonna be some criticisms to me saying that, I don’t wear open-source as a badge. Like, hey I’m a proud open-sourcer. I do have some things on GitHub. My activity is, I’m not really that active on GitHub, but I’ve seen a lot of people who are and who get a lot of nasty comments from people who are like, “You have to fix this.” I used to get those via email. Before I started writing tutorials on how to or how to explain things, I used to write tutorials on how to create certain demos and then after a few months when browser support changed and some demos broke, I used to get a lot of emails from people asking me to fix it for them. And some developers even used to send me emails asking me to fix their projects for them and without even offering anything. I was like, okay, there’s a limit to the amount of things, or the kinds of things that you can do for free. And people just need to understand that. Behind the web, there are people, and people tend to forget that there are people on the other side of the screen. </dd> <dt> <h4>John</h4> </dt> <dd>It’s really interesting, so I started on the web, actually pre-web days even, and one of our primary mechanisms of connecting with people were news groups. That’s how I met, for example, Eric Meyer many, many years ago. And what was really, what was always very interesting to observe in news groups is that people would behave towards someone, and if people aren’t familiar with news groups, I guess the closest analog these days is Slack, a bit like Twitter, in a sense as well. But typically, the difference between a news group is that they were relatively small communities on the whole. There also anybody could largely join in. And what you would find is that people just weren’t capable of imagining they were in a room having a conversation with someone and, therefore, they would, I remember one person when I made a suggestion on something he says, “Literally made me sick.” Like your suggestion, I was like yeah, seriously? You know, if you’re in my house and we’re having a beer or a cup of tea or whatever, would you say that? </dd> <dt> <h4>Sara</h4> </dt> <dd>You wouldn’t say that. </dd> <dt> <h4>John</h4> </dt> <dd>And I think that’s a really good analogy that we’ve sort of somewhat lost. It’s almost like we have to keep learning over and over again the same analogies. I guess my feeling, to some extent, around the whole free thing is, you have, sort of, two consumers or, you’ve obviously got the producer of the presentation, the writing, often the software, the code. You have the audience who will use it as part of their project or learn something from it and grow from it. But then you have either the people who employ those people or you have the companies who gain tremendous advantage from that code base or they may be publishers, they might be a conference company. And I think the balance is tricky. And I think it, probably, I mean one of things, one of our guiding principles with when we ask people to speak, that we want people to leave better for it and often financially is a part of that, right And I do, somewhat, sometimes feel that, particularly amongst those commercial entities that are benefiting really significantly from that work, there is this kind of expectation that, well, it’s all open-source or it’s all free and it’s all part of the giving community and what have you. I think that’s probably, we’re gonna burn out, I think, a lot of people this way. And I really, if I had a call to any activity around this, would be, to the people who really have the resources, to contribute those resources back to ensuring that this is, what I use the term, sustainable. I don’t think right now sometimes that it’s a sustainable ecosystem because we really do, really take for granted a lot of the excess, you know, surplus intellectual property people put into it. </dd> <dt> <h4>Sara</h4> </dt> <dd>I’ve only recently setting limitations and saying no more to conference invitations because, like half or more than half of the invitations that I got for this year, I got more than 30 invitations. </dd> <dt> <h4>John</h4> </dt> <dd>Right, wow. </dd> <dt> <h4>Sara</h4> </dt> <dd>And I said no to most of them because, it’s not mainly because of the money, but it was a big part of it. Like a lot of conferences would ask me to travel for, there was this conference that asked me to travel all the way to San Francisco, to the other side of the world. They would only pay for two nights to stay there. That’s not enough to even get over my jet lag. </dd> <dt> <h4>John</h4> </dt> <dd>Right, yeah. </dd> <dt> <h4>Sara</h4> </dt> <dd>And to give a 15-minute keynote for free. </dd> <dt> <h4>John</h4> </dt> <dd>Yeah, and I’m not gonna necessarily ask who the names are but I’ve found that actually some well-established, successful, large companies have that expectation. </dd> <dt> <h4>Sara</h4> </dt> <dd>Exactly. </dd> <dt> <h4>John</h4> </dt> <dd>And, you know, to me, I think that’s unsustainable, really.</dd> <dt> <h4>John</h4> </dt> <dd>Not these people. </dd> <dt> <h4>John</h4> </dt> <dd>There are people who definitely wanna do the right thing. And it makes it very hard to, essentially, in one sense, compete when other people aren’t necessarily wearing the costs that you are and going to the efforts that you are. Anyway, as I said, I don’t wanna make it about us, thanks for those sorts and I guess the broader point is, and I think as an industry, we really do have to value probably more, the contributions that a relatively small number of people are making. Often, not necessarily the most well-known. I think, in open-source, the very high-profile founders of a project will get recognition, rightly so, and maybe well employed or maybe start a company around what they’re doing. But there are plenty of other people who will make contributions that don’t necessarily do nearly as well out of that, right? </dd> <dt> <h4>Sara</h4> </dt> <dd>Don’t get recognition. </dd> <dt> <h4>John</h4> </dt> <dd>And I’m not sheeting that responsibility home to the people who started that project, by any means. But I think definitely, if your company does well out of other people’s work, you should be compensating them for that is my broad philosophy in life. </dd> <dt> <h4>Sara</h4> </dt> <dd>Definitely. </dd> <dt> <h4>John</h4> </dt> <dd>Anyway. So, you’re, I guess, most well-known, in many respects, for scalable vector graphics for SVG. So, how did you come to have a particular passion for, interest in, expertise around SVG? </dd> <dt> <h4>Sara</h4> </dt> <dd>It’s actually weird because I spent an entire year focusing on CSS only and nobody even sometimes remembers that. Even though I– </dd> <dt> <h4>John</h4> </dt> <dd>I guess there were lots of people who did that. You know, that was a field that was pretty saturated even ten years ago in a way. </dd> <dt> <h4>Sara</h4> </dt> <dd>I got into SVG– </dd> <dt> <h4>John</h4> </dt> <dd>Lea Verou pretty much cornered that market I think. </dd> <dt> <h4>Sara</h4> </dt> <dd>The way I got into SVG was totally unplanned. I gave my first talk a couple of years ago at CSSconf in Miami, so, I was supposed to give a talk about textured text and certain effects and I lost my inspiration for the talk a few weeks before the talk and so I wanted something new. I always like to challenge myself and I always like to put myself under pressure before I give a talk, otherwise, I’m not gonna come up with something creative. So, I had been reading about SVG for a couple of months before that here and there. There were only like a few articles, including one from Chris Coyier. So, everyone’s talking about this new image format and I don’t really </dd> <dt> <h4>John</h4> </dt> <dd>When you say new, were you talking about 12 years ago? </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah, yeah (laughs) </dd> <dt> <h4>John</h4> </dt> <dd>When did you, when was it you, what year are we talking about here? </dd> <dt> <h4>Sara</h4> </dt> <dd>That was two years ago. </dd> <dt> <h4>John</h4> </dt> <dd>All right. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah. </dd> <dt> <h4>John</h4> </dt> <dd>It’s very interesting to me that SVG has been supported since IE9 I think. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah. </dd> <dt> <h4>John</h4> </dt> <dd>So kinda many years before. We’ll get on to, perhaps, why it’s taken so long. But anyway, this reasonably, moderately new technology in 2014 </dd> <dt> <h4>Sara</h4> </dt> <dd>So, the new technology called SVG, I didn’t know anything about it. I don’t like not knowing anything about something. </dd> <dt> <h4>John</h4> </dt> <dd>So, you’d heard of it, it was like (mumbles) </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah, just articles here and there. </dd> <dt> <h4>John</h4> </dt> <dd>Right, right. </dd> <dt> <h4>Sara</h4> </dt> <dd>It has something to do with resolution independence and responsive design is really the big thing today so, I was like, okay. I started reading an article, reading a little more about it and then, this is how it starts with me all the time. Like, I start reading about something, I start taking notes for myself, and then these notes pile up, and then they turn into an article. But with that instance, they turned into a talk. So, I talked to Nicole Sullivan at that time and I said that I’m not really feeling inspired by the textured text talk and I’m thinking about changing it to styling and animating SVGs with CSS. And I didn’t even know that was going to be popular. Like, it was just a new topic, and I didn’t see a lot of people talk about it, so I thought I’d do it. I did and the feedback was amazing. Right now when I think about the slides I feel incredibly proud about them, because there weren’t really that amount of information about SVG gathered in one place like that. Okay, so because of the excitement that I got, and Kristina Schneider, she asked me to give the same talk at CSSconf EU and I wanted it to be updated for that conference, so I started digging more. And that’s when, whenever, if I don’t understand something from the inside out, I can’t really work with it. So I started looking into the viewbox attribute and that was like a black box. It didn’t get, it started changing the values and the image changed in ways that I didn’t even anticipate or expect. I had no idea how it worked and that drove me crazy. So, I spent two weeks, researching, reading. I didn’t find any good articles to make me understand it well. </dd> <dt> <h4>John</h4> </dt> <dd>So you had to go back to the spec. </dd> <dt> <h4>Sara</h4> </dt> <dd>The spec had, like, nothing about the viewbox. So, the only way I knew that I could understand it is to visualize it and that’s exactly what I did. I started, I created an instructive demo. I then, after awhile, I refined it and made it public, but at first I started with, for me. So, I started changing the values of the viewbox and seeing how it changed until one day it clicked and I was able to make the comparison between how the viewbox works, the positioning and the scaling, in how the positioning and scaling of background images works in CSS. They are very similar in that aspect. And that’s when I got the ah-ha moment and ever since then, I always say the same thing, if you understand the viewbox, your SVG codes are taken to a totally new level. And I started falling in love with it, especially the viewbox. Everyone knows how much I love the viewbox. A lot, like in every, I would have mentioned it tomorrow, but there’s nothing really to talk, it’s not really related to the content of my talk tomorrow. Yeah, so I got hooked and I started learning more. And the idea of having an image and being able to control the content of that image. When I used to be a kid, I used to draw a lot. And I used to draw cartoons a lot. And I used to dream about traveling to Japan some day, maybe, and working as an anime, you know, animator, basically. So, you have these images and you get to animate them. And, I didn’t get to do that, so I found SVG where I have an image, and I literally get to animate it using code and that was enough to get me hooked. The more I learned about it, the more I loved it. And I’m still learning. There’s so much more that I’m lagging behind. </dd> <dt> <h4>John</h4> </dt> <dd>So, I think there’s two things I wanna say about that. The first thing is, if you’re interested in becoming a presenter and doing presentations at conferences, I think that path is a really good example of how to do it. We ask lots of people to speak. We’re constantly looking for new speakers. We do speaker workshops and really, one of our missions is to help people become speakers. And time and again people will say, “I don’t know if I’ve got something to say. “I’m not sure what I’ve got to say is really interesting.” But I think a lot of people also think, “Oh, I have to be the world expert in something “in order to come to speak about it.” </dd> <dt> <h4>Sara</h4> </dt> <dd>No. </dd> <dt> <h4>John</h4> </dt> <dd>The fact of the matter is, there are so many undiscovered aspects, even in something like SVG which has been incredibly widely supported since IE9. IE9 was the last holdout. That’s 2009, I think, that we’ve had and I’ve been promoting SVG since long before that and continuing to bang my head against the table as to why people are not adopting, but I guess the point is, here’s a technology that’s been around a long time, incredibly powerful, incredibly exciting and capable, and yet, you’ve found aspects of it that will be valuable to people. No one else could teach you that. You had to work that and then you shared that with other people. I think that’s a really great example of the sort of thing people who are interested in presenting should look at but not think of themselves as having spent 10 years becoming a master. </dd> <dt> <h4>Sara</h4> </dt> <dd>They don’t have to know everything. </dd> <dt> <h4>John</h4> </dt> <dd>You can learn by teaching it to people. </dd> <dt> <h4>Sara</h4> </dt> <dd>By teaching it. Exactly, like when you’re learning, you start getting these moments and you start seeing things from a very different perspective that even experts don’t see them that way. So, you’re able to simplify things because the way you would get them is by simplifying them and, for example, if I or if some experts. I had this teacher back in college. He was a genius. He was incredibly smart. He got the highest not grades, average in college. Yeah, he was incredibly smart but he was the worst teacher. He was the worst at explaining things. So, what I’m trying to say is you don’t have to be really, really an expert in something and know it inside out to talk about it. When I started with SVG, like I said, I learned it two weeks before my talk. And the amount of information that I gave during the talk was all I knew about SVG back then. So, definitely don’t wait to become an expert. And I don’t really think the word expert, people sometimes call me an SVG expert and I’m like, no, I’m not an expert. It’s very hard to define yourself or to define other people as an expert so, if you’re gonna wait for yourself to become one, especially if you have the impostor syndrome, you’re never gonna speak. Because you’re never gonna think of yourself as an expert. </dd> <dt> <h4>John</h4> </dt> <dd>Yeah, absolutely. I studied mathematics and I found that I had dozens of professors over a three-year period and I’m terribly sorry to say that one of them was a good teacher. The rest were, literally, terrible teachers. Because they knew how to do mathematics and so they usually stand there and do it on the blackboard and walk away. </dd> <dt> <h4>Sara</h4> </dt> <dd>Exactly. </dd> <dt> <h4>John</h4> </dt> <dd>Whereas I’ve always, I probably had a similar journey compared with you nearly 20 years ago with CSS, where I had that ah-ha moment and I thought this is brilliant technology. It was only a matter of months old. And when you were telling the story, I felt like, that’s so similar in many respects to the story I had. Although I didn’t necessarily, there weren’t conferences back then. So the way people communicated were very much, there weren’t even blogs back then. You would write articles and you’d post them, often in news groups like that’s what you did. But, it was the fact that I was struggling myself with an idea and had to find a way of understanding and coming at it as you’ve done with the viewbox. So, I guess why I’ve labored on this a little bit is to try and really get people interested in speaking. So, as you say, don’t wait. Don’t think you have to be an expert. In fact, your journey of, not necessarily your personal journey, but your journey of learning about the technology or the practice is actually probably similar to what other people are kinda wanna go through. And so telling that will be very valuable to them. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yes, especially like, I also, there’s another thing that I had, one of the speakers, SmashingConf a couple of weeks ago, he was talking about a topic he wanted to talk about and then he said that someone else was talking about the same topic. So, that made him not talk about it anymore. And I was like, why? Don’t, a lot of, a lot of people on Twitter say I wanted to write this article about that something but then I realized there are a million articles about that so I decided not to do it. That’s so wrong. Everyone has their different aspect, different perspective, I mean, and the way you explain things, as they say, it’s all about style. So, everyone has their own style. And some people can relate to that person’s style and other people will be able to relate to yours not that person’s. So, definitely don’t let that stand in the way. </dd> <dt> <h4>John</h4> </dt> <dd>And in three months I will have inevitably forgotten that article (laughs) </dd> <dt> <h4>Sara</h4> </dt> <dd>Exactly. </dd> <dt> <h4>John</h4> </dt> <dd>We have a very short memory on the web a lot of the time. So, shifting things a little bit. I guess at the moment what we’re seeing is an increasing complexity of what we do on the front end. We were using pre-processors, we’re using lots of libraries and frameworks and they’re doing more and more of the heavy lifting. Are you a person who tends to go toward those layers of abstraction, or you tend to stay with the core foundational technologies? </dd> <dt> <h4>Sara</h4> </dt> <dd>I stay with the core. I’ve always liked staying with the core. Even in college, we had this assembly course, assembly language and then we had the C and C++ courses. Assembly is like the lower level and C is not. I was super comfortable dealing with assembly and really not comfortable with C and I’m still like that with CSS Javascript. I don’t know Angular. I don’t know React. I know Javascript. I know CSS. I only use a pre-processor. I used Less for a while. It didn’t really feel like it was for me. So, I tried Sass. It was simpler, sort of. I do use it these days, but I only use it for variables and nesting which hopefully will come to CSS some day. </dd> <dt> <h4>John</h4> </dt> <dd>Variables is they’ve landed a WebKit now. So, WebKit had an implementation at Con a decade ago of variables. </dd> <dt> <h4>Sara</h4> </dt> <dd>So, the only reason I use Sass is for variables and nesting. </dd> <dt> <h4>John</h4> </dt> <dd>I suspect that’s probably 99% of the use cases with them. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah. </dd> <dt> <h4>John</h4> </dt> <dd>And I tend to like to keep my workflow as simple as possible, and probably pay a bit more of a high cost at the other side. Like I do miss, the variables and nesting are probably the two things that I would hanker after. But still not enough to actually go and actually use a pre-processor. </dd> <dt> <h4>Sara</h4> </dt> <dd>No, I do think they are worth it because they’re time savers and especially when it comes to organizing things. I do like to use them. But frameworks, I’ve never used Bootstrap. I’ve never used, I don’t even know a lot of CSS frameworks actually. </dd> <dt> <h4>John</h4> </dt> <dd>Well, there tend to be less emphasis on them now than there was certainly, I think, three, two, three, four years ago. I think, now why it is because everyone just uses Bootstrap, I don’t know. Or maybe they’ve, sort of, come and they’ve somewhat gone again. Because we were talking a little bit before we were on camera around whether or not in the Arabic world is web design very similar or different? So, I made the observation that, in my experience, certainly some years ago Japanese web design was quite different from what you might call western web design. Amongst my Japanese friends, we’d just discuss why that be different. But you sort of suggested the Arabic way of designing isn’t really too distinct. </dd> <dt> <h4>Sara</h4> </dt> <dd>It’s not really that different, no. And I still get a lot of requests from people, Arabic and non-Arabic, who ask me to build a web site, and one of their requirements is always use Bootstrap. And that’s actually one of the reasons I don’t do it. I don’t wanna be forced to use a framework. I prefer to write my CSS from scratch, from knowing exactly what everything is for, paying attention to progressive enhancement accessibility and all of that stuff without having to worry about being restricted by what Bootstrap has to offer. If you want me to build a web site, I’ll build it the way you want it, but I can do it from scratch. I don’t wanna be restricted by some CSS framework. CSS is simple enough to be written from scratch. Plus there’s a lot of accessibility problems with frameworks and spending time fixing those frameworks is a lot more than doing things from scratch. </dd> <dt> <h4>John</h4> </dt> <dd>Well, I was having a similar conversation with Russ Weekly yesterday. And Russ I’ve known for many years and has been a passionate advocate for accessibility in all that time. And we talked about how it’s kind of ironic, now that we have in the front end things like React, and somebody said Angular, Bootstrap, we’re actually getting worse accessibility rather than better, in some respects. Even though, in a sense, if these tools implemented accessibility well, then it’d almost completely come for free. There wouldn’t be, and yet people seem to find ways of using these technologies in ways that are less accessible, not more. And it’s almost like we don’t care about accessibility as much as we might have ten years ago. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah, I hear this. I do hear this from certain developers. </dd> <dt> <h4>John</h4> </dt> <dd>I think old people. Because our eyes are getting worse, right (laughs). </dd> <dt> <h4>Sara</h4> </dt> <dd>Well, so are mine. </dd> <dt> <h4>John</h4> </dt> <dd>That’s what happens, I used to joke and now it’s not a joke anymore that, if you’re lucky you will become disabled, because you will get older and you will become less mobile and you will be, and when you’re, I probably first said that when I was 29 and now I’m 49 and I think it’s hard to, it’s harder to empathize broadly when you’re young and able-bodied and fit, and your eyes work well. I think it can be a bit more challenging. We can understand theoretically the challenges of accessibility, but I think we need to be, empathy can often come with personal experience or maybe going in, as Russ talked about yesterday, going and watching people use your web site and being humiliated by how you’ve made someone’s life more difficult than it should have been. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yes, you know, I think it gets dangerous when certain developers, which happened yesterday, one of them said, “I don’t care about that one person out of 1300.” And that’s when I personally, where I personally draw the line. I mean, why wouldn’t you care? Maybe you’re that person. Maybe you’re the one having that problem. So, how would you feel if someone treated you the same way? </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah, I certainly think we all lose sight of the fact that the w-w bit of world wide web is worldwide and Tim Berners-Lee, so I sort of have this idea that Tim Berners-Lee gave the world an enormous gift. And it came with, and we’ve got this enormous privilege of being involved with it and helping make it happen and it’s rewarded us individually as professionals, enormously. </dd> <dt> <h4>Sara</h4> </dt> <dd>True. </dd> <dt> <h4>John</h4> </dt> <dd>And the kind of reciprocal responsibility is that always should, we should listen to and try to embody it’s values. And there are a set of values that Tim Berners-Lee has expressly enunciated about the web. And they are about inclusiveness and the very name, worldwide, access regardless of disability, to information. I think those are really important things. So, my blood does, literally, boil, well it doesn’t literally, figuratively boils (laughs) when I hear things like that. Because we’ve been hearing that for 20 years. And it’s a shame, here we go, we have to start all over again. And where do I, how do I, what? You know, maybe we just have to do that. It’s part of our responsibility is to educate newer generations. </dd> <dt> <h4>Sara</h4> </dt> <dd>Exactly, we need more speakers speaking about accessibility at conferences, because I don’t see those a lot. </dd> <dt> <h4>John</h4> </dt> <dd>It went away, right? It used to be a big thing and it’s gone away. We’ve got a bit of it coming up in this conference and the one we’ve got later in the year. But, one of the reasons why we didn’t really have as much in our conferences for a long time, we’re sort of like, that’s all done, people have got it now. People get it. It’s a set of practices. And to me, the challenge is less the practices, that’s part, it’s actually the belief that it is fundamentally important. </dd> <dt> <h4>Sara</h4> </dt> <dd>Sure. </dd> <dt> <h4>John</h4> </dt> <dd>I feel it’s no different to when we started our first conference in 2004. We’ve almost gotta go back and start again. But, maybe that’s just, as I said, the price, that we pay for for our place in the industry. I’ll finish by looking to the future. So, how long would you consider yourself as being professionally doing web things? How long? </dd> <dt> <h4>Sara</h4> </dt> <dd>Two years. </dd> <dt> <h4>John</h4> </dt> <dd>Two years? Only two years? </dd> <dt> <h4>Sara</h4> </dt> <dd>Maybe three, two and a half, or something. </dd> <dt> <h4>John</h4> </dt> <dd>Okay, so, and you’ve been using the web, so when was the first time the web became really a significant part of your day-to-day life? </dd> <dt> <h4>Sara</h4> </dt> <dd>Three years ago. </dd> <dt> <h4>John</h4> </dt> <dd>Really, so before that you really weren’t much of a web user or? </dd> <dt> <h4>Sara</h4> </dt> <dd>I’m not that into tech. </dd> <dt> <h4>John</h4> </dt> <dd>All right. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah, so it’s kinda ironic how I ended up as a geek. </dd> <dt> <h4>John</h4> </dt> <dd>Yeah? </dd> <dt> <h4>Sara</h4> </dt> <dd>Yes, so but I like it. I love it, actually. </dd> <dt> <h4>John</h4> </dt> <dd>You say that, this is the woman who said, “Yeah, I prefer assembly over C.” That is a pretty geeky thing to say. I think the geek kind of genes were deeply in you there. I don’t think it happened, the web just came along and found you. But you were ready for it. </dd> <dt> <h4>Sara</h4> </dt> <dd>Absolutely. The first time I ever touched HTML was in eighth grade and it felt like a natural language. My teacher started talking, putting the P paragraph tags and as soon as I saw them, I was like, wow, I can use these few lines and I have a web page in front of me. So, I did that and I ended up making the best project in school and I did a couple of side projects at home. I got a book from college, from a friend of mine was in college, that was all about HTML and I started reading and reading and reading, and I made, you know the holy grail layout? You have main, sidebar, and header? </dd> <dt> <h4>John</h4> </dt> <dd>I think I have a whole chapter in one of my books on it. </dd> <dt> <h4>Sara</h4> </dt> <dd>I did that using iframes and I felt so proud. </dd> <dt> <h4>John</h4> </dt> <dd>With iframe? </dd> <dt> <h4>Sara</h4> </dt> <dd>Yes. </dd> <dt> <h4>John</h4> </dt> <dd>Right, okay. </dd> <dt> <h4>Sara</h4> </dt> <dd>Yeah, so I fell in love but then the next year, we didn’t take a computer course, so for like four, five years after that I didn’t touch any HTML. I didn’t do anything. And then in college, I didn’t have a lot of options to choose from because we weren’t the richest people in Lebanon, so, there were only a few colleges that I could go to. And so only a few options for majors. Computer science was the least bad, like, I didn’t like the others, so it was like, okay. I’ll just take computer science. I almost switched majors to architecture, to physics, halfway through but then things happened that led me to this path and I’m more than thankful to be here. </dd> <dt> <h4>John</h4> </dt> <dd>All right, so looking forward then those two to three years, so that’s like looking forward the same period of time as looking back, what do you see yourself doing? What do you imagine? </dd> <dt> <h4>Sara</h4> </dt> <dd>What I see myself doing? I don’t know. </dd> <dt> <h4>John</h4> </dt> <dd>Will it still be SVG a big part of that? Or other aspects of web interesting you right now? </dd> <dt> <h4>Sara</h4> </dt> <dd>I’m already shifting away from SVG a little bit. I was talking to a friend of mine awhile back and I was talking about, I used to focus a lot on SVG itself in the last couple of years, and now I’m just focusing at SVG as being part of the bigger tool set, as how it can be used alongside other tools to help us solve bigger design problems and development problems. I’m very much, very much excited about progressive web apps. It’s fantastic. I can’t wait to see it, with the manifest, with HTML5 manifest, the service workers, and just the ability to have that an icon on your home screen that opens the web site that looks exactly like an application that works off-line. That’s incredibly exciting. So, I’m excited about that. I see myself working on side projects more, less speaking. I was actually supposed to not speak a lot this year. I ended up with more than ten speaking engagements. So, maybe next year, I’ll speak less. I wanna focus more on client projects. They are my priority now. That’s why I’ve been writing less recently because I’m setting priorities. I can write if I want, but I don’t wanna sacrifice time from my personal life or from other activities. I’ve given those a priority and writing slightly less. So, I will be writing not as frequently, but I like to focus on new topics. I need to find something to inspire me and progressive web apps is probably gonna be part of that. </dd> <dt> <h4>John</h4> </dt> <dd>Excellent, all right. Well thank you very much for coming all this way. </dd> <dt> <h4>Sara</h4> </dt> <dd>Thank you for having me. </dd> </dl> <p>The post <a rel="nofollow" href="">Video: In Conversation with Sara Soueidan</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 The CSS WG updated the Working Drafts of CSS Box Alignment M… 2016-06-23T00:00:00+00:00 <div><span lang="en-us" class="updated" title="2016-06-23"><span>23</span> Jun 2016</span> The <abbr title="Cascading Style Sheets Working Group">CSS WG</abbr> updated the Working Drafts of <a href=""><cite lang="en" class="notranslate">CSS Box Alignment Module Level 3</cite></a> and <a href=""><cite lang="en" class="notranslate">CSS Scroll Snap Module Level 1</cite></a></div> W3C Cascading Style Sheets 2016-07-12T18:30:04+00:00 UniView 9.0.0 available 2016-06-21T19:39:01+00:00 <p class="floatright"><a href=""><img src="" alt="Picture of the page in action." /></a><br /><span><a href="">>> Use UniView</a></span></p> <p>UniView now supports Unicode version 9, which is being released today, including all changes made during the beta period. (As before, images are not available for the Tangut additions, but the character information is available.)</p> <p>This version of UniView also introduces a new filter feature. Below each block or range of characters is a set of links that allows you to quickly highlight characters with the property <em>letter</em>, <em>mark</em>, <em>number</em>, <em>punctuation</em>, or <em>symbol</em>. For more fine-grained property distinctions, see the <span class="kw">Filter</span> panel.</p> <p>In addition, for some blocks there are other links available that reflect tags assigned to characters. <strong>This tagging is far from exhaustive!</strong> For instance, clicking on <span class="kw">sanskrit</span> will not show all characters used in Sanskrit.</p> <p <span class="kw">currency</span> and all other characters but those related to currency will be dimmed.</p> <p>(Since the highlight function is used for this, don’t forget that, if you happen to highlight a useful subset of characters and want to work with just those, you can use the <span class="kw">Make list from highlights</span> command, or click on the upwards pointing arrow icon below the text area to move those characters into the text area.)</p> ishida blog » css r12a >> blog 2016-07-05T18:00:05+00:00 Idea of the Week – Craig Sharkie 2016-06-20T23:58:15+00:00 <p><img src="" alt="Craig Sharkie" />Craig Sharkie’s presentation at our Respond conference was on how viewport units can make web typography responsive. And a great talk it was.</p> <p>But when we asked him to write an article for our new Scroll magazine, Sharkie went off at a bit of a tangent. He refers in the talk to “contextomy”, the word for taking something out of context, changing its meaning. </p> <p>His article explores that further, digging into how changes in context can affect search results and ultimately what we think of as knowledge and truth. We’ve made that our Idea of the Week.</p> <p>You can also read this article in the first edition of our rebooted <a href="">Scroll Magazine</a>.</p> <h3>Searching for Truth</h3> <h4>by Craig Sharkie</h4> <p> You can google it. You can bing it. You can even let me google that for you. Google themselves would prefer that you didn’t google it. And Yahoo would love anyone to have yahooed it. </p> <p>“It”, of course, is using a search engine, and we’ve all done it. In all likelihood, everyone you know has done it, although you probably see a handful of people each week that haven’t, and wouldn’t.</p> <p>Figures show that 86.9% of Australians are computer literate, which is well above the global computer literacy rate of 39.0%, and safely under the Australian literacy rate of 96%. I know all those figures because I googled them. And Google happily gave me 2,870,000 results, in a breathtaking 0.51 seconds.</p> <p>And we don’t question that. Although perhaps you’re starting to, now. We’re comfortable receiving our search results in batches of 10, and if we make it 10 pages deep in a search, there’s something awry.</p> <p>When Jerry Yang and David Filo launched Yahoo last century, it was a search directory and not a search engine. That just meant that human beings made recommendations about what would be the best results for your search, and not a Web bot with a flashy algorithm. </p> <p>And somewhere along the line we traded human input for a spider’s index.</p> <p>If you’re familiar with the genre you’re searching, and can recognise key personalities in your results, you actually start to apply some directory filtering back over the bot’s results. </p> <p>Interested in Web Development? If you see Mozilla Developer Network or the W3C in your results you’ll be confident you’re heading in the right direction. </p> <p>Interested in Semantic Web Development and you’ll likely skip past W3Schools, but you’ll often take a look at Stack Overflow, just to be sure. Names like Paul Irish, Chris Coyier, Remy Sharp, Eric Meyer, and Peter-Paul Koch will make you more comfortable again. Although for two of those, CSS-Tricks and Quirksmode might be more familiar.</p> <p>Search for “search?q=most+popular+search” and you’ll get 415,000,000 results in a quarter of a second, and there’s frankly no way for you to comprehend that much data in that small an amount of time. We’ve long ago traded quantity and speed for quality and fidelity. Voracity for veracity.</p> <p>And if you take brands out of the mix – think Kardashians, Kanye, Kleenex, or My Kitchen Rules – and pornography from the mix – think … well you know what to think – the most searched for term in 2015 was “weather”.</p> <p>45.5 million people per month searched for weather, and the smart money says folks wanted to know the forecast, and not the science behind the weather.</p> <p>In our hunger for information we often overlook quality. We opt for common usage, over uncommon precision. And we’re happy to do it for searches as we’ve become used to doing it for so many other parts of our shared experience. We have precedent for it and we’re familiar with it, and it’s almost an expectation. Great minds think alike, after all.</p> <p>And even the saying “Great minds think alike” has fallen victim to the race for more results. It’s become a contextomy – the selective excerpting of words from their original linguistic context in a way that distorts the source’s intended meaning. Ask Wikipedia what a contextomy is.</p> <p>“Great minds think alike, small minds rarely differ” or “Great minds think alike, and fools seldom differ” are the directory versions, and the more idiomatic “Great minds think alike” is the search engine version.</p> <p>Millions of people misquote this saying and in that misquotation change the meaning we take from the quote. </p> <p>When we find answers that fit the shape of our question, and in the face of potentially millions of answers, we excuse ourselves from the need to investigate the answers too thoroughly. Often, there is little harm in our expedience; occasionally, though that expedience is the root of our lament.</p> <p>Were we to take the time to investigate, the answer would be closer than we think, and more useful than we expect.</p> <p>Allow yourself to only need an image search for “Great minds think alike” and you’d be told the saying originated in Ancient Greece. Don’t settle for the picture-telling-a-thousand-words option, and Google can lead you to a Stack Overflow result where you’d learn that the idiom wasn’t quite that old and likely comes from the 17th Century.</p> <p>We don’t always need to go back to the source or specification to get the truth behind the answers we need, but we do need to be sure that someone has done the hard yards there for us. The answer that we desperately need might be the 11th result on Google and can save us hours of work. </p> <p>Had Jesse James Garrett not been going back to the specification, he might not have been among the drive that saw Asynchronous JavaScript + XML push the use of the Internet in new directions.<br /> Arguably, you don’t need to know that Garrett coined the term Ajax in the shower, but then that might be the information that’s your tipping point.</p> <p>And, as they say, “the rest is science”. </p> <p>Or do they? </p> <p>Maybe we should google that.</p> <p>The post <a rel="nofollow" href="">Idea of the Week – Craig Sharkie</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 Monday Profile: Jen Simmons 2016-06-20T02:16:53+00:00 <p><img src="" alt="jen simmons" />This week’s Monday profile is Jen Simmons: web designer, front-end developer, Designer Advocate at Mozilla and host of The Web Ahead podcast.</p> <p>Jen spoke at our <a href="">Respond Front End Design conference</a>, and this profile appeared in <a href="">our magazine, Scroll, which you can download right now</a>.</p> <p>You can <a href="">follow Jen on Twitter</a>, and find her at <a href=""></a>.</p> <p><strong>Q </strong> Describe your family.</p> <p><strong>A</strong> I come from a long line of English folks, some of whom immigrated to Massachusetts in the days of the Mayflower, others who moved to Washington D.C. in the early 20th century, with a bunch in between. </p> <p>While there’s a bit of Scottish and a bit of German in my ancestry, it’s mostly English, English and English. There must be something to the sense of where you are from, way back, as the U.K. is now one of my favourite places to be. It does seem familiar somehow. Comfortable.</p> <p><strong>Q </strong> What book has changed your life in some way?</p> <p><strong>A</strong> There have been several books that have changed my life: <em>A Separate Peace</em>; <em>Designing with Web Standards</em>; <em>Bulletproof Web Design</em>; anything by Judy Blume. But if I were to pick one, I’d say <em>There is Nothing Wrong with You: Going Beyond Self Hate</em> by Cheri Huber. It’s a funny little book. Big hand-written-style text. Lots of drawings. It walks you through one particular idea–there’s a voice in your head that’s telling you crappy stuff all the time. And that voice is lying to you.</p> <p>Cheri Huber is a meditation teacher in the tradition of Zen Buddhism. She’s written a pile of books, including <em>The Fear Book</em> and <em>The Depression Book</em>. <em>The Fear Book</em> is another that changed me. And <em>The Depression Book</em> is the best book on depression I’ve ever seen. I think I’ve bought <em>There is Nothing Wrong with You</em> a half dozen times. I keep giving away my copy and buying it again. Really all of Cheri Huber’s many books teach the same simple truth about life and who we are. But it’s a truth that’s both the hardest thing to<br /> learn and the most helpful.</p> <p><strong>Q </strong> What formal qualifications do you have? How did you end up doing web work?</p> <p><strong>A</strong> I have a BA in Sociology with minors in Mathematics and Theatre from Gordon College. And an MFA in Film and Media Arts from Temple University. In neither did I set out to study web design or computer science. I did computer science in junior high and high school (and did very well), but dropped out because of the culture of harassment.</p> <p>I got into the web years later as a natural progression of living a career as an artist. I was designing lighting, sets and sound for theatre, producing events, teaching high school (and later college) students, and doing freelance graphic design. When the web came along, it was only natural that I also make the websites, so I taught myself HTML. </p> <p>Eventually, I stopped doing print because I was bored with it. After I moved to New York in 2008, I focused on a full-time career as a designer and front-end developer, shifting to larger budget projects with teams. And I eventually evolved my role as a teacher into what I do today. I love being both creative and technical. I find being on the forefront of a medium very exciting.</p> <p><strong>Q </strong> Describe what you do. What’s your job? Is presenting at web conferences part of that job?</p> <p><strong>A</strong> I am a Designer Advocate for Mozilla–as a member of their Developer Relations team. So yes, it is part of my job to travel around and present at conferences. I was doing so long before I got this job at Mozilla. But it’s great now to have the backing of an institution to help make it possible.</p> <p>It’s also my job to collect ideas and feedback from the web industry and take those requests back to Mozilla. The folks who make browsers usually don’t also make websites. It’s my job to research the field and bring my findings back, to advocate for designers and developers within Mozilla.</p> <p>I’m also the host and executive producer of “The Web Ahead”, a podcast about new technology and the future of the web. I started the show in 2011, and have been thrilled to reach such a large audience, bringing many of the ideas and guests we see at web conferences to folks around the world.</p> <p><strong>Q </strong> Do you give much thought to the title you apply to yourself? Does it matter?</p> <p><strong>A</strong> I do think titles can matter. They carry power. At Mozilla we can chose our own titles, and I put a lot of thought into mine. The job opening for my position was titled “Technical Evangelist”, but I don’t believe this is really about the technology. It’s about people, and what people can do with technology–not the technology for its own sake.</p> <p>Our department is called “Developer Relations” but I believe designers are just as important as developers–perhaps more so, since their work impacts the humans who use our sites and products more directly. Advocate is a great word, and more accurately reflects the responsibilities I have. So Designer Advocate it is. Or Designer and Developer Advocate on more wordy days.</p> <p><strong>Q </strong> Describe the first time you gave a presentation on a web topic.</p> <p><strong>A</strong> I think the first presentation I gave at a tech industry event was in 2006 at Vloggercon. I showed people how to customise their Blogger blog using CSS. I’d been on panels at conferences a few times before, but that was the first time I prepared a talk with slides, and gave it on my own. The conference was a gathering of the folks who invented the techniques for putting video on the web. It was a great community that I was honoured to be part of.</p> <p>Of course I was incredibly nervous. I didn’t feel prepared. I’d taught college courses for three years by then, so I was used to lecturing, but somehow a conference presentation seems much higher stakes.</p> <p>I think it went well. I likely left wanting to have done a much better job. I’ve been striving to get better and better ever since.</p> <p><strong>Q </strong> In <em>The Graduate</em>, Mr McGuire has just one word to say to aimless college graduate Benjamin Braddock: “Plastics”. What one word would you give to today’s prospective web professional? </p> <p><strong>A</strong> Layout.</p> <p>If an aimless college grad wanted to break into the web industry today, and wanted to know what they should focus on to get ahead–I’d tell them “layout!”</p> <p>There’s incredible opportunity coming to invent some truly new design patterns. Once CSS Grid Layout hits browsers, everything about layout will change. Anyone who knows what’s coming will have lots of work.<: Jen Simmons</a> appeared first on <a rel="nofollow" href="">Web Directions</a>.</p> Web Directions Blog Blog – Web Directions Awesome conferences for web professionals. 2016-07-22T00:00:04+00:00 | http://www.w3.org/Style/CSS/Planet/atom.xml | CC-MAIN-2016-30 | refinedweb | 43,329 | 69.72 |
68913/how-can-i-find-script-s-directory-with-python
Hii,
Consider the following Python code:
import os
print os.getcwd()
I use os.getcwd() to get the script file's directory location. When I run the script from the command line it gives me the correct path whereas when I run it from a script run by code in a Django view it prints .
How can I get the path to the script from within a script run by a Django view?
You need to call os.path.realpath on __file__, so that when __file__ is a filename without the path you still get the dir path:
import os
print(os.path.dirname(os.path.realpath(__file__)))
Thank you!!
Context Manager: cd
import os
class cd:
"""Context manager for ...READ MORE
You probably want to use np.ravel_multi_index:
[code]
import numpy ...READ MORE
You can use the Axes.set_yscale method. That allows you ...READ MORE
import os
from optparse import OptionParser, Option
class MyOption ...READ MORE
suppose you have a string with a ...READ MORE
You can also use the random library's ...READ MORE
Syntax :
list. count(value)
Code:
colors = ['red', 'green', ...READ MORE
Enumerate() method adds a counter to an ...READ MORE
Hii,
Using exc_info options may be better, to allow you ...READ MORE
Hello,
Just replace and with , and you're done:
try:
...READ MORE
OR
At least 1 upper-case and 1 lower-case letter
Minimum 8 characters and Maximum 50 characters
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#include " having #495350 in the wild? And I have at least two more non-BTS-logged reports of the same problem (*). The problem is not nice, apt just appears to go nuts which is not something an end user should have to deal with. So no, sorry, Lenny version is NOT fine and I hopped you would thrust my judgement in the upstream role here. And I wonder how can using a more stable Beta version (in Sid) be more wise then an early Alpha version (in Lenny ATM)... And mean "less risk" for a package without dependent packages. And sorry for going ad hominem but that's just like a slap in my face. Regards, Eduard. (*) Most likely, it's a Heisenbug. -- In der Wahl seiner Feinde kann der Mensch nicht vorsichtig genug sein. -- Oscar Wilde
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I have inherited about 2000 MP3 files. For the majority of them, their ID3 tags display garbled in Amarok. I need a software that upgrades the ID3 tags to v2.4 type $03 (i.e. UTF-8 encoding), removes any v1 tags, and is also smart about figuring out the original encoding on a case-by-case basis (most likely one of Windows-1252, BOM-less UTF-16 or GB18030).
$03
Before I start programming this on my own on top of TagLib, is there already such a complete solution I could use?
Do not recommend Musicbrainz – it is heavily biased to United States published music and near useless to me. Do not recommend general ID3 tagging software without testing it first against my requirements – most of them
I am also not (yet) interested in tag cleaning, mass renaming or categorisation software only; I first have do the afore-mentioned normalisation step.
You want Ex Falso, the tag editor included in the Quod Libet project. Picard (the MusicBrainz tagger) may use the same tagging library, but QL originated it.
In particular, you want the Mutagen tagging library, which supports id3v2.4 (and by "support" I mean "enforce" ...militarily...). It is also excellent with character encodings, and includes a basic scriptable commandline tagger (mid3v2). As far as your normalization step goes, Mutagen only saves tags in ID3v2.4. It is certainly capable of converting all text into UTF-8, but you may need to script that yourself (I believe that the mid3v2 tool's defaults are to keep the current encoding where possible, and I don't know if it can be told to save everything in a particular encoding). Mutagen is written in Python.
mid3v2
Ex Falso is a nice, clean GUI , and supports most of the major retag-multiple-files features you'd expect. I don't think it does much in the way of internet lookups and I don't know how it is with album artwork -- Quod Libet may support that; Ex Falso can do it with a plugin, should one exist, though one might not exist. I've never needed that functionality -- I use EF and mid3v2 in concert to handle my retagging needs.
Latin1
Windows-1252
iconv
I don't think you're going to find a standalone application that will fix up your particular selection of incorrectly-tagged encodings. Having a mixture of cp1252, UTF-16 and GB-18030 is quite unusual and I don't think existing software will be able to solve that automatically.
So I'd download Mutagen and write a custom Python script to automate your own decisions about how to fix up unknown encodings. For example:
musicroot= ur'C:\music\wonky'
tryencodings= 'gb18030', 'cp1252'
import os
import mutagen.id3
def findMP3s(path):
for child in os.listdir(path):
child= os.path.join(path, child)
if os.path.isdir(child):
for mp3 in findMP3s(child):
yield mp3
elif child.lower().endswith(u'.mp3'):
yield child
for path in findMP3s(musicroot):
id3= mutagen.id3.ID3(path)
for key, value in id3.items():
if value.encoding!=3 and isinstance(getattr(value, 'text', [None])[0], unicode):
if value.encoding==0:
bytes= '\n'.join(value.text).encode('iso-8859-1')
for encoding in tryencodings:
try:
bytes.decode(encoding)
except UnicodeError:
pass
else:
break
else:
raise ValueError('None of the tryencodings work for %r key %r' % (path, key))
for i in range(len(value.text)):
value.text[i]= value.text[i].encode('iso-8859-1').decode(encoding)
value.encoding= 3
id3.save()
The above script makes a few assumptions:
Only the tags marked as being in encoding 0 are wrong. (Ostensibly encoding 0 is ISO-8859-1, but in practice it is often a Windows default code page.)
If a tag is marked as being in UTF-8 or a UTF-16 encoding it's assumed to be correct, and simply converted to UTF-8 if it isn't already. Personally I haven't seen ID3s marked as UTF (encodings 1-3) in error before. Luckily encoding 0 is easy to recover into its original bytes since ISO-8859-1 is a 1-to-1 direct mapping of the ordinal byte values.
When an encoding 0 tag is met, the script attempts to recast it as GB18030 first, then if it's not valid falls back to code page 1252. Single-byte encodings like cp1252 will tend to match most byte sequences, so it's best to put them at the end of the list of encodings to try.
If you have other encodings like cp1251 Cyrillic, or a lot of cp1252 filenames with multiple accented characters in a row, that get mistaken for GB18030, you'll need a cleverer guessing algorithm of some sort. Maybe look at the filename to guess what sort of characters are likely to be present?
How about Mp3Tag with Wine?
Features (among others):.
Foobar has pretty complete tagging support. It runs under wine.
there's also EasyTag.
also you might want to know that id3v2.3 is usually preferable format, because windows media player doesn't support 2.4
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