text stringlengths 454 608k | url stringlengths 17 896 | dump stringclasses 91
values | source stringclasses 1
value | word_count int64 101 114k | flesch_reading_ease float64 50 104 |
|---|---|---|---|---|---|
The plan was that this story would cover XML in IE5, including
the base language, setting up the server, CSS, XSL, and the DOM.
Unfortunately, we had a hard deadline (IE5 went public on March 18th), and
when it arrived, I'd invested so much time in learning XSL, without getting
anything based on the public drafts working in IE5, that it occupied all the
time we'd budgeted for both that and the DOM.
We'll keep struggling with XSL until we get something that actually works and
plays by the rules.
Following that, we'll go on and do some DOM coverage.
The event that motivates publishing this article at this time is, of
course, the arrival of Microsoft
Internet Explorer Release 5.
While we will try out one or two things in the bleeding-edge pre-alpha
Netscape "Gecko" code, the main focus of this article is publishing and
browsing XML in a standards-compliant way using IE5.
Of course, when there is actually some sort of real released product from
Netscape, we'll publish an even more interesting article - how to publish and
browse XML in an interoperable way.
This is after all XML.com, and it's about time that we started
publishing in XML. The subject of the story, naturally, enough, is how to go about publishing and browsing XML on the Web.
There are a bunch of different ways to deliver XML over the Web.
The first, and most obvious, is to give up and not try; after all, it's going
to be years, probably, before most people will have XML-capable browsers on
their desktops.
So you could just take the XML and turn it into HTML and
deliver that. (And in fact, if you're not adventurous, that version of this
article may be what you're now reading).
A second option is to just go ahead and deliver XML, as-is, don't
sweat stylesheets or anything, and just see what
happens. With IE5, this turns out to be not as useless as you might
think.
The right thing to do is to send the XML to a browser with
a stylesheet, today in
in CSS and before too
long, in XSL.
This has a bunch of advantages:
If you are running Apache 1.3.4, you are in luck, since the mime type for xml files is already configured. If you are running an earlier version of Apache and you have access to the server configuration:
Edit the mime.types file and add the mime type by adding the line:
text/xml xml
then restart the Apache server.
If you don't have access to your server configuration, or don't want to mess with the configuration files, ask your system administrator to add the mime type:
text/xml xml
Other servers have slightly different methods for adding mime types.
Before you can worry about browing XML, you have to find a server (or
set up your own) that serves it properly.
We've enclosed a note from one of XML.com's webmasters that
explains how you might go about doing that.
If you just want to read the XML out of a file (as I'm doing right now while
writing this article) things are a lot easier; when IE5 opens a file whose
name ends with ".xml", it assumes that it's going to contain XML and does the
right things.
At this point, now that you're ready to serve, you need something to
serve.
For this document, just to keep things clear, I invented the tags as I went
along, choosing reasonable-sounding names, and didn't bother
with a DTD.
In many cases, you can use someone else's pre-cooked DTD; one good
candidate would be the
HTML-in-XML
currently under development at the W3C.
Whether you've got a DTD or whether you're just making it up as you go
along, you're going to need something to type it in with.
The really basic approach is your usual text editor; that's what I do, except
for my usual text editor is GNU emacs, which isn't basic at all.
Emacs is really a tool for the hard-core geeks; you'd probably be better off
having a look through
XML.com's list of
authoring tools.
Of course, you wouldn't want to invent all your own tags.
If you need a list, or a hypertext reference, HTML has those already built in,
and with the magic of XML
namespaces, you should be able to use those HTML elements.
Here's how it ought to work, in theory:
For example:
<start xmlns:
<H:ol>
<H:li>Declare a namespace prefix and bind it to the official
namespace for HTML.</H:li>
<H:li>Use the names of HTML elements in your document, but
attach that prefix you declared.</H:li>
</H:ol>
</start>
This kind of works, which is a little surprising.
Since the W3C hasn't gotten around to declaring an official namespace
name for HTML, the IE team has a tough problem in figuring out how to follow
the rules.
If it didn't work, you wouldn't see all the nice bullet-lists and
hyperlinks in the XML version of this document..
If you want to use stylesheets, you'll have to tell the browser.
The way to do that is to put a "stylesheet linking PI" at the top of your
document; here's an example:
<?xml-stylesheet href="first-x.css" type="text/css" ?>
Which leads us to the first nasty bug. That little fragment is supposed
to begin with "<?xml-stylesheet...", but in all the IE5 examples
I've seen, it begins with "<?xml:stylesheet...", a now-obsolete
version that grossly violates the "Namespaces in XML" specification.
When I was preparing the example just above, I ran across another really
ugly problem.
I wanted to show the stylesheet linking PI, but
I couldn't just cut-n-paste it in as-is, because it
has a "<" character, which you can't have in XML text. So I "escaped"
it using the standard
built-in XML (and HTML) "<" technique:
<?xml-stylesheet href="first-x.css" type="text/css" ?>
Unfortunately, this made the whole example vanish!
It seems that IE gets confused somehow and sees the "<" as a
"<" unless it's followed by a space,
and starts parsing away.
After pondering this one for quite a bit, I ended up with the
following:
<<no-op/>?xml-stylesheet href="first-x.css" type="text/css" ?>
The trick is that the empty "<no-op />" element keeps IE from getting
confused.
Another trick would be to use "CDATA Sections" for examples like this.
But they seem pretty well completely broken in IE5 as well; it complains
about undeclared namespace prefixes and so on.
Sigh, release 1.0 of anything is always exciting, even when it's called
release 5.0.
If you load an XML document into IE5 with no stylesheet at all, you get
a nice tree-structured display with little +/- icons that you can click to
hide subtrees.
I've actually started using this quite a bit to have a quick look at XML
documents that people send me; it's a good way to get a feeling for the
content and structure of some arbitrary XML.
At this point in history, there is only one official, approved, stable,
production-quality standard for stylesheets, and it's named Cascading
Style Sheets, or CSS for short.
CSS 1 has been
around since December 1996, and
CSS 2 since May 1998.
I don't really have the time and space to do a full investigation on CSS
compliance, but I don't need to, because my colleagues on the
Web Standards Project are
hard at work on this even as I write.
In general I found the IE's CSS handling pretty good; i.e. everything I
tried worked more or less first time. It's probably worth your while to grab
the CSS stylesheet that's being used here and have a look at it; it's not
rocket science, but it does illustrate a few tricks that I think will
be useful for a lot of people.
In particular, I'm fond of the float technique; in
the XML+CSS form of this article, the sidebar and examples and little
good/bad/bug graphics are done with
CSS floats; previously, you would have had to use <TABLE> kludges to
achieve this kind of effect.
But I have to end on kind of a sour note.
We may be moving the paperless office, but a lot of us still need to print
quite a few of our documents.
With XML+CSS, IE5 can't; that is to say, when you print, you get an
unformatted dump.
So near, and yet so far.
I wondered whether the XML+CSS display would work in the
pre-pre-pre-release of Mozilla.
Since I hadn't downloaded that in a few weeks, I went
over there and
pulled down a recent build, ignoring all the blood-curdling warnings about
using this untested and pre-cooked software.
Good news! It worked not too badly at all, first time out.
Mozilla is a lot pickier about margins and so on, and does
the floats a little bit differently from IE (I'm not enough of a CSS scholar
to say which is right) - but we are looking at two pieces of software with
strongly converging behavior.
Maybe there's hope for standards yet.
It is perfectly crystal-clear that Microsoft is un-enthused about CSS.
The Microsofties who helped us out with this article kept reminding us that we
should show off formatting with XSL.
And in fact, if you have links both to a CSS and an XSL stylesheet, IE picks
the XSL version.
Just to review,
XSL - Extensible Stylesheet Language - is a W3C work-in-progress which is
scheduled for completion sometime later in 1999.
It comes in two parts - a "transformation language" used for preparing
documents for display, and a "formatting object set" that is used for actual
visual styling.
At this point in history, several groups (including Microsoft) have
implemented a snapshot of the transformation language, but no-one has got the formatting
part going.
What Microsoft would like us to do, apparently, is to use the XSL
transformation engine to turn XML into HTML before displaying it.
This is going to cause problems.
For example, in order to write this article, I needed to teach myself
XSL, so I went and looked at the XSL Working Draft - it's called a "Working
Draft" because it's in-progress and might change; if I may quote from the
introduction:
It quickly became obvious that the Microsoft XSL examples contain many
things that aren't in the XSL Working Draft.
Is this because they, as members of the XSL Working Group, know about things
that will be in a soon-to-arrive draft of XSL?
I don't know.
Is it safe to use them?
I don't know.
The bottom line was that when the deadline for this article rolled
around, I didn't have XSL working.
This is a pity, because XSL has a couple of tremendously attractive
properties. Perhaps the most important is that it will run both in the
browser and in the server; so you can send XML+XSL to XSL-capable browsers,
and for the rest, run the same code on the server to generate HTML.
But in XML.com, we try hard to do things by the rules, so you won't see
any XSL in production here until we can figure out how to use it by the book -
we assume that IE5 will be able to do this.
After our little expedition force had washed up on the rocks of XSL, we
were left with a document, in XML only, that couldn't display in the
real-world (rev 4 and behind) browsers that real people have on their real
desktops.
But we were undismayed, because we opened our grease-stained tool box,
and whipped out the all-purpose tool.
127 lines of perl later (using, of course, the brand-new "XML::Parser" module),
we had a less-pretty form of the article (probably
what some of you are reading), in HTML generated automatically from the XML.
It'll be interesting to note, after we get the job done with XSL, whether it
turns out to be more or less code than in perl.
Also it'll be interesting to make a judgement on which is more maintainable
and flexible.
First, you have to install it.
Microsoft kindly sent us a CD before the rest of the world got it (thanks,
Dave); and the installation on my NT box was pretty pain-free.
Following the advice of my local expert, I uninstalled the IE5 beta first, and
rebooted just to be sure.
Firing up the CD reveals that it contains not just IE but NT Service Pack 4,
which I hadn't installed.
So, installing the service pack and taking all the defaults, you're
looking at 3 or so reboots, and a lot of waiting while watching polite
messages from Windows about how it's optimizing your system.
I thought it was interesting that the CD-ROM contains 198 MB of data;
you probably don't need to get that much to get yourself an IE5,
but it's safe to say that IE5 is going to be a great big honkin' download.
Microsoft has in recent times been making their browser updates available on
CD-ROM for almost nothing, basically the cost of duplication and shipping; my
experience suggests that this is probably the best way to go about getting
IE5.
This article isn't a Web browser review, but IE5 seems like a pretty
nice Web browser, except the XML-related problems.
It runs fast (faster than IE4, much faster than
any version of Communicator, about the same as the Mozilla pre-releases)
and looks good. As before, the smooth scrolling and
cleaner
screen are improvements over Netscape. As before, it insists, when you create
a new browser window, at starting in the same page that was active, rather
than your home page.
It does one thing better than any previous version of IE - namely, when you
use the "back" button, it does a fine job of coming back to a point in the
page not too distant from what you left behind.
IE's error-handling seems exactly per the spec, which is delightful.
I've been giving speeches for a couple of years now telling people that
XML-style error handling in the browser wouldn't really change work patterns;
you'd bash out your XML, and when it displayed in the browser, you could ship
it. I'm glad to have discovered that I've been telling the truth.
At least,
that's how this article got created - whenever I stupidly put a tag in the
wrong place or forgot a quotation mark, IE politely but firmly told me
where the problem was.
IE's error handling becomes very irritating, of course, when there's
not really an error - for example, when the browser refuses to bypass escaped
"<" characters.
But we can assume that Microsoft will work on fixing that.
Is the glass half-empty or half-full?
It's too early to call; rendering XML with CSS is nice (and will be even nicer
once IE 5.x fixes a few more bugs), but the real value-add of XML in the
browser isn't so much displaying it as processing it right there in the browser.
For that, you need the DOM; if IE5 turns out to have a nice clean usable DOM,
that will make up for a lot of little awkwardness in the parser.
If not, this will look like a (huge amount of) wasted effort.
Stay tuned.
Be the first to post this article to del.icio.us | http://www.xml.com/pub/a/1999/03/ie5/first-x.html | crawl-001 | refinedweb | 2,693 | 67.69 |
Paolo Bonzini <pbonzini@redhat.com> writes: > On 22/07/21 16:02, Markus Armbruster wrote: >> Double-checking: the other fields are not accessible via this visitor. >> Correct? > > Correct. > >>> >>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> >>> --- >>> include/qapi/forward-visitor.h | 27 +++ >>> qapi/meson.build | 1 + >>> qapi/qapi-forward-visitor.c | 307 ++++++++++++++++++++++++++++++ >>> tests/unit/meson.build | 1 + >>> tests/unit/test-forward-visitor.c | 165 ++++++++++++++++ >>> 5 files changed, 501 insertions(+) >>> create mode 100644 include/qapi/forward-visitor.h >>> create mode 100644 qapi/qapi-forward-visitor.c >>> create mode 100644 tests/unit/test-forward-visitor.c >> >> Missing: update of the big comment in include/qapi/visitor.h. Can be >> done on top. > > Also because I'm not sure what to add. :) > > * There are four kinds of visitors: input visitors (QObject, string, * and QemuOpts) parse an external representation and build the * corresponding QAPI object, output visitors (QObject and string) * take a QAPI object and generate an external representation, the * dealloc visitor takes a QAPI object (possibly partially * constructed) and recursively frees it, and the clone visitor * performs a deep clone of a QAPI object. a sentence along the lines of "The forwarding visitor is special: it wraps another visitor, and shares its type." >>> +static bool forward_field_translate_name(ForwardFieldVisitor *v, const >>> char **name, >>> + Error **errp) >>> +{ >>> + if (v->depth) { >>> + return true; >>> + } >> >> Succeed when we're in a sub-struct. >> >>> + if (g_str_equal(*name, v->from)) { >>> + *name = v->to; >>> + return true; >>> + } >> >> Succeed when we're in the root struct and @name is the alias name. >> Replace the alias name by the real one. >> >>> + error_setg(errp, QERR_MISSING_PARAMETER, *name); >>> + return false; >> >> Fail when we're in the root struct and @name is not the alias name. >> >>> +} >> >>? >>> + /* >>> + * The name of alternates is reused when accessing the content, >>> + * so do not increase depth here. >>> + */ >> >> I understand why you don't increase @depth here (same reason >> qobject-input-visitor.c doesn't qobject_input_push() here). I don't >> understand the comment :) > > See above: the alternate is not a struct; the names that are passed > between start_alternate and end_alternate are within the same namespace > as the toplevel field. Yes. > As to the comment, the idea is: if those calls used e.g. name == NULL, > the depth would need to be increased, but the name will be the same one > that was received by start_alternate. Change to "The name passed to > start_alternate is also used when accessing the content"?. | https://lists.gnu.org/archive/html/qemu-devel/2021-07/msg05921.html | CC-MAIN-2021-43 | refinedweb | 393 | 58.58 |
Details
- Type:
Bug
- Status: Closed
- Priority:
Major
- Resolution: Fixed
- Affects Version/s: Scala 2.9.1
- Fix Version/s: Scala 2.10.0-M4, Scala 2.10.0
- Component/s: Misc Compiler
- Labels:
- Environment:Hide
$ uname -a Darwin gagarin.local 11.4.0 Darwin Kernel Version 11.4.0: Mon Apr 9 19:32:15 PDT 2012; root:xnu-1699.26.8~1/RELEASE_X86_64 x86_64 $ scalac -version Scala compiler version 2.9.1.final -- Copyright 2002-2011, LAMP/EPFL
Description
Given the following files:
// Base.java public class Base { public boolean foo() { return true; } } // Abstract.java public abstract class Abstract extends Base { public abstract boolean foo(); // force re-implementation in derived classes } // DerivedJava.java public class DerivedJava extends Abstract {} // DerivedScala.scala class DerivedScala extends Abstract // Main.scala object Main extends App { new DerivedScala().foo() }
WIth these present, javac will fail to compile DerivedJava, complaining that foo needs to be defined. However, scalac will not fail to compile DerivedScala.scala, and when Main.scala is compiled and run, it crashes with AbstractMethodError (shown here from the REPL):
scala> class Derived extends Abstract defined class Derived scala> new Derived().foo() java.lang.AbstractMethodError: Derived.foo()Z at .<init>(<console>:9):680)
Activity
Class DerivedScala extends the abstract class Abstract. I expected that the compiler flags an error on class DerivedScala, as its base class contains a deferred definition of a method, similarly to
scala> class A {def foo = 0 } defined class A scala> abstract class B extends A { def foo: Int } defined class B scala> class C extends B <console>:9: error: class C needs to be abstract, since there is a deferred decl aration of method foo in class B of type => Int which is not implemented in a su bclass class C extends B ^
The check that should fire here ("there is a deferred declaration of ... which is not implemented in a subclass") is disabled by a condition added in:
Dominik,
I understand that in order to compile successfully that DerivedJava must be declared abstract. The DerivedJava class is there to demonstrate an expected compilation failure. The description doesn't make sense if DeclaredJava compiles, so I have returned the description to its original state. The class is not "used" except as an example of where javac should (and does) fail to compile.
The compiler does not flag an error on DerivedScala, which is the point of the bug report.
Tentative fix:
Thanks so much for getting this fixed quickly. Is there any chance of getting a backport to a 2.9 patch release?
May I ask why? This seems a pretty obscure bug that wouldn't really be a blocker.
The policy, given limited resources, is to only backport if the interested party either:
1. does the leg-work to cherry-pick the commit to the 2.9.x branch and checks that the test suite passes, and submits a pull request, or
2. has a support contract with TypeSafe.
It's also not clear if there will be a 2.9.3 release at all.
No, it's not a blocker, though it is a bug generator, as a Java dependency of a Scala project I maintain added a new abstract method in a version upgrade; not having the compiler fail created a latent bug at runtime.
I understand there may not be a 2.9.3, but if there is I would predict it will before 2.10, and have less impact to development (and more importantly, my end users) than a 2.10 upgrade.
I'll take a look at doing the cherry-pick legwork, in the hopes that a 2.9.3 release happens. Thanks again for the quick fix.
Jason, maybe you could apply some of the same sauce as with
SI-4989 | https://issues.scala-lang.org/browse/SI-6013 | CC-MAIN-2014-15 | refinedweb | 629 | 66.64 |
In this article, we’ll identify high-quality Python code and show you how to improve the quality of your own code.
We’ll analyze and compare tools you can use to take your code to the next level. Whether you’ve been using Python for a while, or just beginning, you can benefit from the practices and tools talked about here.
What is Code Quality?
Of course you want quality code, who wouldn’t? But to improve code quality, we have to define what it is.
A quick Google search yields many results defining code quality. As it turns out, the term can mean many different things to people.
One way of trying to define code quality is to look at one end of the spectrum: high-quality code. Hopefully, you can agree on the following high-quality code identifiers:
- It does what it is supposed to do.
- It does not contain defects or problems.
- It is easy to read, maintain, and extend.
These three identifiers, while simplistic, seem to be generally agreed upon. In an effort to expand these ideas further, let’s delve into why each one matters in the realm of software.
Why Does Code Quality Matter?
To determine why high-quality code is important, let’s revisit those identifiers. We’ll see what happens when code doesn’t meet them.
It does not do what it is supposed to do
Meeting requirements is the basis of any product, software or otherwise. We make software to do something. If in the end, it doesn’t do it… well it’s definitely not high quality. If it doesn’t meet basic requirements, it’s hard to even call it low quality.
It does contain defects and problems
If something you’re using has issues or causes you problems, you probably wouldn’t call it high-quality. In fact, if it’s bad enough, you may stop using it altogether.
For the sake of not using software as an example, let’s say your vacuum works great on regular carpet. It cleans up all the dust and cat hair. One fateful night the cat knocks over a plant, spilling dirt everywhere. When you try to use the vacuum to clean the pile of dirt, it breaks, spewing the dirt everywhere.
While the vacuum worked under some circumstances, it didn’t efficiently handle the occasional extra load. Thus, you wouldn’t call it a high-quality vacuum cleaner.
That is a problem we want to avoid in our code. If things break on edge cases and defects cause unwanted behavior, we don’t have a high-quality product.
It is difficult to read, maintain, or extend
Imagine this: a customer requests a new feature. The person who wrote the original code is gone. The person who has replaced them now has to make sense of the code that’s already there. That person is you.
If the code is easy to comprehend, you’ll be able to analyze the problem and come up with a solution much quicker. If the code is complex and convoluted, you’ll probably take longer and possibly make some wrong assumptions.
It’s also nice if it’s easy to add the new feature without disrupting previous features. If the code is not easy to extend, your new feature could break other things.
No one wants to be in the position where they have to read, maintain, or extend low-quality code. It means more headaches and more work for everyone.
It’s bad enough that you have to deal with low-quality code, but don’t put someone else in the same situation. You can improve the quality of code that you write.
If you work with a team of developers, you can start putting into place methods to ensure better overall code quality. Assuming that you have their support, of course. You may have to win some people over (feel free to send them this article 😃).
How to Improve Python Code Quality
There are a few things to consider on our journey for high-quality code. First, this journey is not one of pure objectivity. There are some strong feelings of what high-quality code looks like.
While everyone can hopefully agree on the identifiers mentioned above, the way they get achieved is a subjective road. The most opinionated topics usually come up when you talk about achieving readability, maintenance, and extensibility.
So keep in mind that while this article will try to stay objective throughout, there is a very-opinionated world out there when it comes to code.
So, let’s start with the most opinionated topic: code style.
Style Guides
Ah, yes. The age-old question: spaces or tabs?
Regardless of your personal view on how to represent whitespace, it’s safe to assume that you at least want consistency in code.
A style guide serves the purpose of defining a consistent way to write your code. Typically this is all cosmetic, meaning it doesn’t change the logical outcome of the code. Although, some stylistic choices do avoid common logical mistakes.
Style guides serve to help facilitate the goal of making code easy to read, maintain, and extend.
As far as Python goes, there is a well-accepted standard. It was written, in part, by the author of the Python programming language itself.
PEP 8 provides coding conventions for Python code. It is fairly common for Python code to follow this style guide. It’s a great place to start since it’s already well-defined.
A sister Python Enhancement Proposal, PEP 257 describes conventions for Python’s docstrings, which are strings intended to document modules, classes, functions, and methods. As an added bonus, if docstrings are consistent, there are tools capable of generating documentation directly from the code.
All these guides do is define a way to style code. But how do you enforce it? And what about defects and problems in the code, how can you detect those? That’s where linters come in.
Linters
What is a Linter?
First, let’s talk about lint. Those tiny, annoying little defects that somehow get all over your clothes. Clothes look and feel much better without all that lint. Your code is no different. Little mistakes, stylistic inconsistencies, and dangerous logic don’t make your code feel great.
But we all make mistakes. You can’t expect yourself to always catch them in time. Mistyped variable names, forgetting a closing bracket, incorrect tabbing in Python, calling a function with the wrong number of arguments, the list goes on and on. Linters help to identify those problem areas.
Additionally, most editors and IDE’s have the ability to run linters in the background as you type. This results in an environment capable of highlighting, underlining, or otherwise identifying problem areas in the code before you run it. It is like an advanced spell-check for code. It underlines issues in squiggly red lines much like your favorite word processor does.
Linters analyze code to detect various categories of lint. Those categories can be broadly defined as the following:
- Logical Lint
- Code errors
- Code with potentially unintended results
- Dangerous code patterns
- Stylistic Lint
- Code not conforming to defined conventions
There are also code analysis tools that provide other insights into your code. While maybe not linters by definition, these tools are usually used side-by-side with linters. They too hope to improve the quality of the code.
Finally, there are tools that automatically format code to some specification. These automated tools ensure that our inferior human minds don’t mess up conventions.
What Are My Linter Options For Python?
Before delving into your options, it’s important to recognize that some “linters” are just multiple linters packaged nicely together. Some popular examples of those combo-linters are the following:
Flake8: Capable of detecting both logical and stylistic lint. It adds the style and complexity checks of pycodestyle to the logical lint detection of PyFlakes. It combines the following linters:
- PyFlakes
- pycodestyle (formerly pep8)
- Mccabe
Pylama: A code audit tool composed of a large number of linters and other tools for analyzing code. It combines the following:
- pycodestyle (formerly pep8)
- pydocstyle (formerly pep257)
- PyFlakes
- Mccabe
- Pylint
- Radon
- gjslint
Here are some stand-alone linters categorized with brief descriptions:
And here are some code analysis and formatting tools:
Comparing Python Linters
Let’s get a better idea of what different linters are capable of catching and what the output looks like. To do this, I ran the same code through a handful of different linters with the default settings.
The code I ran through the linters is below. It contains various logical and stylistic issues:
1 """ 2 code_with_lint.py 3 Example Code with lots of lint! 4 """ 5 import io 6 from math import * 7 8 9 from time import time 10 11 some_global_var = 'GLOBAL VAR NAMES SHOULD BE IN ALL_CAPS_WITH_UNDERSCOES' 12 13 def multiply(x, y): 14 """ 15 This returns the result of a multiplation of the inputs 16 """ 17 some_global_var = 'this is actually a local variable...' 18 result = x* y 19 return result 20 if result == 777: 21 print("jackpot!") 22 23 def is_sum_lucky(x, y): 24 """This returns a string describing whether or not the sum of input is lucky 25 This function first makes sure the inputs are valid and then calculates the 26 sum. Then, it will determine a message to return based on whether or not 27 that sum should be considered "lucky" 28 """ 29 if x != None: 30 if y is not None: 31 result = x+y; 32 if result == 7: 33 return 'a lucky number!' 34 else: 35 return( 'an unlucky number!') 36 37 return ('just a normal number') 38 39 class SomeClass: 40 41 def __init__(self, some_arg, some_other_arg, verbose = False): 42 self.some_other_arg = some_other_arg 43 self.some_arg = some_arg 44 list_comprehension = [((100/value)*pi) for value in some_arg if value != 0] 45 time = time() 46 from datetime import datetime 47 date_and_time = datetime.now() 48 return
The comparison below shows the linters I used and their runtime for analyzing the above file. I should point out that these aren’t all entirely comparable as they serve different purposes. PyFlakes, for example, does not identify stylistic errors like Pylint does.
For the outputs of each, see the sections below.
Pylint
Pylint is one of the oldest linters (circa 2006) and is still well-maintained. Some might call this software battle-hardened. It’s been around long enough that contributors have fixed most major bugs and the core features are well-developed.
The common complaints against Pylint are that it is slow, too verbose by default, and takes a lot of configuration to get it working the way you want. Slowness aside, the other complaints are somewhat of a double-edged sword. Verbosity can be because of thoroughness. Lots of configuration can mean lots of adaptability to your preferences.
Without further ado, the output after running Pylint against the lint-filled code from above:
No config file found, using default configuration ************* Module code_with_lint W: 23, 0: Unnecessary semicolon (unnecessary-semicolon) C: 27, 0: Unnecessary parens after 'return' keyword (superfluous-parens) C: 27, 0: No space allowed after bracket return( 'an unlucky number!') ^ (bad-whitespace) C: 29, 0: Unnecessary parens after 'return' keyword (superfluous-parens) C: 33, 0: Exactly one space required after comma def __init__(self, some_arg, some_other_arg, verbose = False): ^ (bad-whitespace) C: 33, 0: No space allowed around keyword argument assignment def __init__(self, some_arg, some_other_arg, verbose = False): ^ (bad-whitespace) C: 34, 0: Exactly one space required around assignment self.some_other_arg = some_other_arg ^ (bad-whitespace) C: 35, 0: Exactly one space required around assignment self.some_arg = some_arg ^ (bad-whitespace) C: 40, 0: Final newline missing (missing-final-newline) W: 6, 0: Redefining built-in 'pow' (redefined-builtin) W: 6, 0: Wildcard import math (wildcard-import) C: 11, 0: Constant name "some_global_var" doesn't conform to UPPER_CASE naming style (invalid-name) C: 13, 0: Argument name "x" doesn't conform to snake_case naming style (invalid-name) C: 13, 0: Argument name "y" doesn't conform to snake_case naming style (invalid-name) C: 13, 0: Missing function docstring (missing-docstring) W: 14, 4: Redefining name 'some_global_var' from outer scope (line 11) (redefined-outer-name) W: 17, 4: Unreachable code (unreachable) W: 14, 4: Unused variable 'some_global_var' (unused-variable) ... R: 24,12: Unnecessary "else" after "return" (no-else-return) R: 20, 0: Either all return statements in a function should return an expression, or none of them should. (inconsistent-return-statements) C: 31, 0: Missing class docstring (missing-docstring) W: 37, 8: Redefining name 'time' from outer scope (line 9) (redefined-outer-name) E: 37,15: Using variable 'time' before assignment (used-before-assignment) W: 33,50: Unused argument 'verbose' (unused-argument) W: 36, 8: Unused variable 'list_comprehension' (unused-variable) W: 39, 8: Unused variable 'date_and_time' (unused-variable) R: 31, 0: Too few public methods (0/2) (too-few-public-methods) W: 5, 0: Unused import io (unused-import) W: 6, 0: Unused import acos from wildcard import (unused-wildcard-import) ... W: 9, 0: Unused time imported from time (unused-import)
Note that I’ve condensed this with ellipses for similar lines. It’s quite a bit to take in, but there is a lot of lint in this code.
Note that Pylint prefixes each of the problem areas with a
R,
C,
W,
E, or
F, meaning:
- [R]efactor for a “good practice” metric violation
- [C]onvention for coding standard violation
- [W]arning for stylistic problems, or minor programming issues
- [E]rror for important programming issues (i.e. most probably bug)
- [F]atal for errors which prevented further processing
The above list is directly from Pylint’s user guide.
PyFlakes
Pyflakes “makes a simple promise: it will never complain about style, and it will try very, very hard to never emit false positives”. This means that Pyflakes won’t tell you about missing docstrings or argument names not conforming to a naming style. It focuses on logical code issues and potential errors.
The benefit here is speed. PyFlakes runs in a fraction of the time Pylint takes.
Output after running against lint-filled code from above:
code_with_lint.py:5: 'io' imported but unused code_with_lint.py:6: 'from math import *' used; unable to detect undefined names code_with_lint.py:14: local variable 'some_global_var' is assigned to but never used code_with_lint.py:36: 'pi' may be undefined, or defined from star imports: math code_with_lint.py:36: local variable 'list_comprehension' is assigned to but never used code_with_lint.py:37: local variable 'time' (defined in enclosing scope on line 9) referenced before assignment code_with_lint.py:37: local variable 'time' is assigned to but never used code_with_lint.py:39: local variable 'date_and_time' is assigned to but never used
The downside here is that parsing this output may be a bit more difficult. The various issues and errors are not labeled or organized by type. Depending on how you use this, that may not be a problem at all.
pycodestyle (formerly pep8)
Used to check some style conventions from PEP8. Naming conventions are not checked and neither are docstrings. The errors and warnings it does catch are categorized in this table.
Output after running against lint-filled code from above:
code_with_lint.py:13:1: E302 expected 2 blank lines, found 1 code_with_lint.py:15:15: E225 missing whitespace around operator code_with_lint.py:20:1: E302 expected 2 blank lines, found 1 code_with_lint.py:21:10: E711 comparison to None should be 'if cond is not None:' code_with_lint.py:23:25: E703 statement ends with a semicolon code_with_lint.py:27:24: E201 whitespace after '(' code_with_lint.py:31:1: E302 expected 2 blank lines, found 1 code_with_lint.py:33:58: E251 unexpected spaces around keyword / parameter equals code_with_lint.py:33:60: E251 unexpected spaces around keyword / parameter equals code_with_lint.py:34:28: E221 multiple spaces before operator code_with_lint.py:34:31: E222 multiple spaces after operator code_with_lint.py:35:22: E221 multiple spaces before operator code_with_lint.py:35:31: E222 multiple spaces after operator code_with_lint.py:36:80: E501 line too long (83 > 79 characters) code_with_lint.py:40:15: W292 no newline at end of file
The nice thing about this output is that the lint is labeled by category. You can choose to ignore certain errors if you don’t care to adhere to a specific convention as well.
pydocstyle (formerly pep257)
Very similar to pycodestyle, except instead of checking against PEP8 code style conventions, it checks docstrings against conventions from PEP257.
Output after running against lint-filled code from above:
code_with_lint.py:1 at module level: D200: One-line docstring should fit on one line with quotes (found 3) code_with_lint.py:1 at module level: D400: First line should end with a period (not '!') code_with_lint.py:13 in public function `multiply`: D103: Missing docstring in public function code_with_lint.py:20 in public function `is_sum_lucky`: D103: Missing docstring in public function code_with_lint.py:31 in public class `SomeClass`: D101: Missing docstring in public class code_with_lint.py:33 in public method `__init__`: D107: Missing docstring in __init__
Again, like pycodestyle, pydocstyle labels and categorizes the various errors it finds. And the list doesn’t conflict with anything from pycodestyle since all the errors are prefixed with a
D for docstring. A list of those errors can be found here.
Code Without Lint
You can adjust the previously lint-filled code based on the linter’s output and you’ll end up with something like the following:
1 """Example Code with less lint.""" 2 3 from math import pi 4 from time import time 5 from datetime import datetime 6 7 SOME_GLOBAL_VAR = 'GLOBAL VAR NAMES SHOULD BE IN ALL_CAPS_WITH_UNDERSCOES' 8 9 10 def multiply(first_value, second_value): 11 """Return the result of a multiplation of the inputs.""" 12 result = first_value * second_value 13 14 if result == 777: 15 print("jackpot!") 16 17 return result 18 19 20 def is_sum_lucky(first_value, second_value): 21 """ 22 Return a string describing whether or not the sum of input is lucky. 23 24 This function first makes sure the inputs are valid and then calculates the 25 sum. Then, it will determine a message to return based on whether or not 26 that sum should be considered "lucky". 27 """ 28 if first_value is not None and second_value is not None: 29 result = first_value + second_value 30 if result == 7: 31 message = 'a lucky number!' 32 else: 33 message = 'an unlucky number!' 34 else: 35 message = 'an unknown number! Could not calculate sum...' 36 37 return message 38 39 40 class SomeClass: 41 """Is a class docstring.""" 42 43 def __init__(self, some_arg, some_other_arg): 44 """Initialize an instance of SomeClass.""" 45 self.some_other_arg = some_other_arg 46 self.some_arg = some_arg 47 list_comprehension = [ 48 ((100/value)*pi) 49 for value in some_arg 50 if value != 0 51 ] 52 current_time = time() 53 date_and_time = datetime.now() 54 print(f'created SomeClass instance at unix time: {current_time}') 55 print(f'datetime: {date_and_time}') 56 print(f'some calculated values: {list_comprehension}') 57 58 def some_public_method(self): 59 """Is a method docstring.""" 60 pass 61 62 def some_other_public_method(self): 63 """Is a method docstring.""" 64 pass
That code is lint-free according to the linters above. While the logic itself is mostly nonsensical, you can see that at a minimum, consistency is enforced.
In the above case, we ran linters after writing all the code. However, that’s not the only way to go about checking code quality.
When Can I Check My Code Quality?
You can check your code’s quality:
- As you write it
- When it’s checked in
- When you’re running your tests
It’s useful to have linters run against your code frequently. If automation and consistency aren’t there, it’s easy for a large team or project to lose sight of the goal and start creating lower quality code. It happens slowly, of course. Some poorly written logic or maybe some code with formatting that doesn’t match the neighboring code. Over time, all that lint piles up. Eventually, you can get stuck with something that’s buggy, hard to read, hard to fix, and a pain to maintain.
To avoid that, check code quality often!
As You Write
You can use linters as you write code, but configuring your environment to do so may take some extra work. It’s generally a matter of finding the plugin for your IDE or editor of choice. In fact, most IDEs will already have linters built in.
Here’s some general info on Python linting for various editors:
Before You Check In Code
If you’re using Git, Git hooks can be set up to run your linters before committing. Other version control systems have similar methods to run scripts before or after some action in the system. You can use these methods to block any new code that doesn’t meet quality standards.
While this may seem drastic, forcing every bit of code through a screening for lint is an important step towards ensuring continued quality. Automating that screening at the front gate to your code may be the best way to avoid lint-filled code.
When Running Tests
You can also place linters directly into whatever system you may use for continuous integration. The linters can be set up to fail the build if the code doesn’t meet quality standards.
Again, this may seem like a drastic step, especially if there are already lots of linter errors in the existing code. To combat this, some continuous integration systems will allow you the option of only failing the build if the new code increases the number of linter errors that were already present. That way you can start improving quality without doing a whole rewrite of your existing code base.
Conclusion
High-quality code does what it’s supposed to do without breaking. It is easy to read, maintain, and extend. It functions without problems or defects and is written so that it’s easy for the next person to work with.
Hopefully it goes without saying that you should strive to have such high-quality code. Luckily, there are methods and tools to help improve code quality.
Style guides will bring consistency to your code. PEP8 is a great starting point for Python. Linters will help you identify problem areas and inconsistencies. You can use linters throughout the development process, even automating them to flag lint-filled code before it gets too far.
Having linters complain about style also avoids the need for style discussions during code reviews. Some people may find it easier to receive candid feedback from these tools instead of a team member. Additionally, some team members may not want to “nitpick” style during code reviews. Linters avoid the politics, save time, and complain about any inconsistency.
In addition, all the linters mentioned in this article have various command line options and configurations that let you tailor the tool to your liking. You can be as strict or as loose as you want, which is an important thing to realize.
Improving code quality is a process. You can take steps towards improving it without completely disallowing all nonconformant code. Awareness is a great first step. It just takes a person, like you, to first realize how important high-quality code is.
What Do You Think?
Real Python Comment Policy: The most useful comments are those written with the goal of learning from or helping out other readers—after reading the whole article and all the earlier comments. Complaints and insults generally won’t make the cut here. | https://realpython.com/python-code-quality/ | CC-MAIN-2018-34 | refinedweb | 3,932 | 64.51 |
Some Tips, Tricks, and Common Errors¶
These are small summaries of ideas, tips, and commonly seen errors that might be helpful to those beginning Python.
Functions¶
Functions help us with our mental chunking: they allow us to group together statements for a high-level purpose, e.g. a function to sort a list of items, a function to make the turtle draw a spiral, or a function to compute the mean and standard deviation of some measurements.
There are two kinds of functions: fruitful, or value-returning functions, which calculate and return a value, and we use them
because we’re primarily interested in the value they’ll return. Void (non-fruitful) functions
are used because they perform actions that we want done — e.g. make a turtle draw a rectangle, or
print the first thousand prime numbers. They always return
None — a special dummy value.
Tip:
None is not a string
Values like
None,
True and
False are not strings: they are special values
in Python, and are in the list of keywords we gave in chapter 2 (Variables, expressions, and statements). Keywords are special
in the language: they are part of the syntax. So we cannot create our own
variable or function with a name
True — we’ll get a syntax error.
(Built-in functions are not privileged like keywords: we can define our own
variable or function called
len, but we’d be silly to do so!)
Along with the fruitful/void families of functions, there are two flavors of the
return statement in Python: one that returns
a useful value, and the other that returns nothing, or
None. And if we get to the end of
any function and we have not explicitly executed any
return statement, Python automatically
returns the value
None.
Tip: Understand what the function needs to return
Perhaps nothing — some functions exists purely to perform actions rather than to calculate and return a result. But if the function should return a value, make sure all execution paths do return the value.
To make functions more useful, they are given parameters. So a function to make a turtle draw
a square might have two parameters — one for the turtle that needs to do the drawing, and another
for the size of the square. See the first example in Chapter 4 (Functions) — that function can be used with any turtle,
and for any size square. So it is much more general than a function that always uses a specific turtle,
say
tess to draw a square of a specific size, say 30.
Tip: Use parameters to generalize functions
Understand which parts of the function will be hard-coded and unchangeable, and which parts should become parameters so that they can be customized by the caller of the function.
Tip: Try to relate Python functions to ideas we already know
In math, we’re familiar with functions like
f(x) = 3x + 5. We already understand
that when we call the function
f(3) we make some association between the parameter x
and the argument 3. Try to draw parallels to argument passing in Python.
Quiz: Is the function
f(z) = 3z + 5 the same as function
f above?
Problems with logic and flow of control¶
We often want to know if some condition holds for any item in a list, e.g. “does the list have any odd numbers?” This is a common mistake:
Can we spot two problems here? As soon as we execute a
return, we’ll leave the function.
So the logic of saying “If I find an odd number I can return
True” is fine. However, we cannot
return
False after only looking at one item — we can only return
False if we’ve been through
all the items, and none of them are odd. So line 6 should not be there, and line 7 has to be
outside the loop. To find the second problem above, consider what happens if you call this function
with an argument that is an empty list. Here is a corrected version:
This “eureka”, or “short-circuit” style of returning from a function as soon as we are certain what the outcome will be was first seen in Section 8.10, in the chapter on strings.
It is preferred over this one, which also works correctly:
The performance disadvantage of this one is that it traverses the whole list, even if it knows the outcome very early on.
Tip: Think about the return conditions of the function
Do I need to look at all elements in all cases? Can I shortcut and take an early exit? Under what conditions? When will I have to examine all the items in the list?
The code in lines 7-10 can also be tightened up. The expression
count > 0
evaluates to a Boolean value, either
True or
False. The value can be used
directly in the
return statement. So we could cut out that code and simply
have the following:
Although this code is tighter, it is not as nice as the one that did the short-circuit return as soon as the first odd number was found.
Tip: Generalize your use of Booleans
Mature programmers won’t write
if is_prime(n) == True: when they could
say instead
if is_prime(n): Think more generally about Boolean values,
not just in the context of
if or
while statements. Like arithmetic
expressions, they have their own set of operators (
and,
or,
not) and
values (
True,
False) and can be assigned to variables, put into lists, etc.
A good resource for improving your use of Booleans is
Exercise time:
- How would we adapt this to make another function which returns
Trueif all the numbers are odd? Can you still use a short-circuit style?
- How would we adapt it to return
Trueif at least three of the numbers are odd? Short-circuit the traversal when the third odd number is found — don’t traverse the whole list unless we have to.
Local variables¶
Functions are called, or activated, and while they’re busy they create their own stack frame which holds local variables. A local variable is one that belongs to the current activation. As soon as the function returns (whether from an explicit return statement or because Python reached the last statement), the stack frame and its local variables are all destroyed. The important consequence of this is that a function cannot use its own variables to remember any kind of state between different activations. It cannot count how many times it has been called, or remember to switch colors between red and blue UNLESS it makes use of variables that are global. Global variables will survive even after our function has exited, so they are the correct way to maintain information between calls.
This fragment assumes our turtle is
tess. Each time we call
h2() it turns, draws, and increases
the global variable
sz. Python always assumes that an assignment to a variable (as in line 7) means
that we want a new local variable, unless we’ve provided a
global declaration (on line 4). So
leaving out the global declaration means this does not work.
Tip: Local variables do not survive when you exit the function
Use a Python visualizer like the one at to build a strong understanding of function calls, stack frames, local variables, and function returns.
Tip: Assignment in a function creates a local variable
Any assignment to a variable within a function means Python will make a local variable,
unless we override with
global.
Event handler functions¶
Our chapter on event handling showed three different kinds of events that we could handle. They each have their own subtle points that can trip us up.
- Event handlers are void functions — they don’t return any values.
- They’re automatically called by the Python interpreter in response to an event, so we don’t get to see the code that calls them.
- A mouse-click event passes two coordinate arguments to its handler, so when we write this handler we have to provide for two parameters (usually named
xand
y). This is how the handler knows where the mouse click occurred.
- A keypress event handler has to be bound to the key it responds to. There is a messy extra step when using keypresses: we have to remember to issue a
wn.listen()before our program will receive any keypresses. But if the user presses the key 10 times, the handler will be called ten times.
- Using a timer to create a future-dated event only causes one call to the handler. If we want repeated periodic handler activations, then from within the handler we call
wn.ontimer(....)to set up the next event.
String handling¶
There are only four really important operations on strings, and we’ll be able to do just about anything. There are many more nice-to-have methods (we’ll call them sugar coating) that can make life easier, but if we can work with the basic four operations smoothly, we’ll have a great grounding.
- len(str) finds the length of a string.
- str[i] the subscript operation extracts the i’th character of the string, as a new string.
- str[i:j] the slice operation extracts a substring out of a string.
- str.find(target) returns the index where target occurs within the string, or -1 if it is not found.
So if we need to know if “snake” occurs as a substring within
s, we could write
It would be wrong to split the string into words unless we were asked whether the word “snake” occurred in the string.
Suppose we’re asked to read some lines of data and find function definitions, e.g.:
def some_function_name(x, y):,
and we are further asked to isolate and work with the name of the function. (Let’s say, print it.)
One can extend these ideas:
- What if the function def was indented, and didn’t start at column 0? The code would need a bit of adjustment, and we’d probably want to be sure that all the characters in front of the
def_posposition were spaces. We would not want to do the wrong thing on data like this:
# I def initely like Python!
- We’ve assumed on line 3 that we will find an open parenthesis. It may need to be checked that we did!
- We have also assumed that there was exactly one space between the keyword
defand the start of the function name. It will not work nicely for
def f(x)
As we’ve already mentioned, there are many more “sugar-coated” methods that let us
work more easily with strings. There is an
rfind method, like
find, that searches from the
end of the string backwards. It is useful if we want to find the last occurrence of something.
The
lower and
upper methods can do case conversion. And the
split method is great for
breaking a string into a list of words, or into a list of lines. We’ve also made extensive use
in this book of the
format method. In fact, if we want to
practice reading the Python documentation and learning some new methods on our own, the
string methods are an excellent resource.
Exercises:
- Suppose any line of text can contain at most one url that starts with “http://” and ends at the next space in the line. Write a fragment of code to extract and print the full url if it is present. (Hint: read the documentation for
find. It takes some extra arguments, so you can set a starting point from which it will search.)
- Suppose a string contains at most one substring “< ... >”. Write a fragment of code to extract and print the portion of the string between the angle brackets.
Looping and lists¶
Computers are useful because they can repeat computation, accurately and fast. So loops are going to be a central feature of almost all programs you encounter.
Tip: Don’t create unnecessary lists
Lists are useful if you need to keep data for later computation. But if you don’t need lists, it is probably better not to generate them.
Here are two functions that both generate ten million random numbers, and return the sum of the numbers. They both work.
What reasons are there for preferring the second version here?
(Hint: open a tool like the Performance Monitor on your computer, and watch the memory
usage. How big can you make the list before you get a fatal memory error in
sum1?)
In a similar way, when working with files, we often have an option to read the whole file contents into a single string, or we can read one line at a time and process each line as we read it. Line-at-a-time is the more traditional and perhaps safer way to do things — you’ll be able to work comfortably no matter how large the file is. (And, of course, this mode of processing the files was essential in the old days when computer memories were much smaller.) But you may find whole-file-at-once is sometimes more convenient! | http://7-fountains.com/7FD/thinkcspy3/thinkcspy3/app_e.html | CC-MAIN-2018-51 | refinedweb | 2,201 | 69.72 |
On Thu, 2006-11-16 at 20:45 -0800, Roland Dreier wrote:> > +struct t3_send_wr {> > + struct fw_riwrh wrh; /* 0 */> > + union t3_wrid wrid; /* 1 */> > +> > + enum t3_rdma_opcode rdmaop:8;> > + u32 reserved:24; /* 2 */> > Does this do the right thing wrt endianness? I'd be more comfortable> with something like> > u8 rdmaop;> u8 reserved[3];> > (although the __attribute__((packed)) on enum t3_rdma_opcode does make> it OK to use here, I guess)> > > + u32 rem_stag; /* 2 */> > + u32 plen; /* 3 */> > + u32 num_sgle;> > + struct t3_sge sgl[T3_MAX_SGE]; /* 4+ */> > +};I don't really like the bit fields either. I inherited these structs andI'm not adverse to changing them as you suggest to get rid of bitfields. But I think they are correct wrt endianness. I wrote a testprogram and on a LE machine it put the u8 first in memory followed bythe 24 bit reserved. However, I think if you use bit fields less than 8bits its not endian safe.BTW: I don't have a PPC system (yet) to test this code on BE...Here's a dumb program that plays around with bit fields...#include <sys/types.h>#include <inttypes.h>#include <stdint.h>#include <stdio.h>struct foo { uint32_t a:8; uint32_t b:24; uint32_t c:16; uint32_t d:8; uint32_t e:8;};struct bar { uint8_t a; uint8_t b[3]; uint16_t c; uint8_t d; uint8_t e;};struct bits {#if 0 /* BE */ uint32_t a:4; uint32_t b:4;#else /* LE */ uint32_t b:4; uint32_t a:4;#endif uint32_t c:8; uint32_t d:8; uint32_t e:8;};main(){ struct foo foo; struct bar bar; struct bits bits; uint8_t *cp; int i; foo.a = 0x01; foo.b = 0x020304; foo.c = 0x0506; foo.d = 0x07; foo.e = 0x08; printf("foo cpu: 0x%" PRIx64 "\n", *(uint64_t *)&foo); printf("foo mem: "); cp = (uint8_t *)&foo; for (i=0; i<8; i++) printf("%02x", *cp++); printf("\n"); bar.a = 0x01; bar.b[0] = 0x02; bar.b[1] = 0x03; bar.b[2] = 0x04; bar.c = 0x0506; bar.d = 0x07; bar.e = 0x08; printf("bar cpu: 0x%" PRIx64 "\n", *(uint64_t *)&bar); printf("bar mem: "); cp = (uint8_t *)&bar; for (i=0; i<8; i++) printf("%02x", *cp++); printf("\n"); bits.a = 0x1; bits.b = 0x2; bits.c = 0x3; bits.d = 0x4; bits.e = 0x5; printf("bits cpu: 0x%08x\n", *(uint32_t *)&bits); printf("bar mem: "); cp = (uint8_t *)&bits; for (i=0; i<4; i++) printf("%02x", *cp++); printf("\n");}-To unsubscribe from this list: send the line "unsubscribe linux-kernel" inthe body of a message to majordomo@vger.kernel.orgMore majordomo info at read the FAQ at | https://lkml.org/lkml/2006/11/17/182 | CC-MAIN-2014-15 | refinedweb | 421 | 75.91 |
Recently, I've written an article about using a .NET third party library to generate reports from apps. You can find it on this in my previous post. In my opinion, the whole idea might be useful, for instance, for performance tests. I often try to make such in my blog. Basically you do some tests and then output results to the console or a txt file...
But, wouldn't it be great to write results directly to a spreadsheet and draw some charts automatically? Can it be done in C++ as well?
Introduction and managed code.
That way, we can run our algorithms and benchmarks at full speed, with crazy native code optimizations. At the end we, simply, pass results to the reporter module. Then, we have our reports ready to analyze.
Of course another way would be to copy results from a txt file (or a console output) to a spreadsheet file. I've used this option often, and I must say that sometimes it wastes a lot of your time!
Managed code called from native
It is easy to call C++ from C#. All you have to do is use some kind of
PInvoke and Interoperability mechanisms and call a native function from managed code.
However, how can we call C# from C++? In other words: how can we use reverse
PInvoke?
Fortunately, it should be also quite easy:
- We need to create a reporter module DLL in C++ CLI.
- C++ CLI enables use to use third party library written in C# (.NET)
- From native code we can use the above DLL as 'normal DLL'.
- I've use this tutorial: tigerang/reverse-pinvoke
As always with interop, things gets complicated when you want to pass from one side to another (managed/native) a complex data. In my example I managed to use only simple, basic types that are handled automatically by the framework.
Implementation
Source code can be found here: github.com/fenbf/AutoPerfReport
Reporter interface: C++/CLI
#pragma once #ifdef REPORTER_EXPORTS #define REPORTER_API __declspec(dllexport) #else #define REPORTER_API __declspec(dllimport) #endif namespace reporter { class REPORTER_API Reporter { private: class *Result _results; public: Reporter(); ~Reporter(); void AddResult(const char *colName, int n, double elapsedTime); void SaveToFile(const char *fname); }; }
This interface is not that generic. But for a simple tests can be useful. For each test run you would call
AddResult method with a test name,
n - size of a test case and
elapsedTime.
Native code:
for (int n = startCount; n <= endCount; n += stepCount) { for(auto &test : perfTests) { test->run(n); report.AddResult(test->name(), n, pt->elapsedTimeSec()); } }
Managed code:
void Reporter::AddResult(const char *colName, int n, double elapsedTime) { _results->_res[colName][n] = elapsedTime; }
To hold the results I've used map of maps:
class Results { public: std::map<std::string, std::map<int, double>> _res; };
This map stores for each test case (its name), a map of number of 'N' and elapsed time for such test run.
So
_res["hello"][100] - means elapsed time for test run 'hello' with 100 elements.
And the main method:
void Reporter::SaveToFile(const char *fname) { Workbook ^workbook = gcnew Workbook(); workbook->CreateEmptySheets(2); String ^range = ""; String ^labelRange = ""; writeData(_results, workbook, range, labelRange); createChart(workbook, range, labelRange); std::cout << "Workbook with data created!" << std::endl; String ^filename = gcnew String(fname); workbook->SaveToFile(filename, ExcelVersion::Version2007); std::cout << "Workbook written to " << fname << std::endl; }
The C++CLI code looks almost like C#, but with those funny
^ characters :)
As name suggests
writeData and
createChart functions writes data to a spreadsheet (fills the rows) and then create a chart out of this data.
In the above example I've profit from Spire.XLS library. This is very handy and easy to use module. I've used the free version (max 150 rows per file) - but this is enough for most of my cases.
Basically the library lets you manage XLS files without having Office installed in your system. Additionally, I had no problems with adding references in Visual Studio 2013 Express and even in C++ CLI. Of course, it will work flawlessly with .NET Framework (any above 2.0)
The output
Actually my output from native/managed example is the same as in my original article. But, that was my purpose! :)
Spire.XLS library created a file, wrote some rows, formed a chart and saved it successfully to disk. Of course, the test results now comes from native, not managed, code!
Summary
In the above example I've shown how easily output test results from native code into a worksheet file. Spire.XLS< library makes our life very easy and with several lines of code you can create a file, chart perform calculation.
For a simple test case this might be optional, but when you develop a bigger project such automation will save you a lot of time.
Resources
What do you think about this design?
Do you know any other library that can help with such automation?
What method do you use to output test results from your experiments? | http://www.bfilipek.com/2014/06/automated-reports-with-c.html | CC-MAIN-2018-05 | refinedweb | 835 | 63.8 |
This is your resource to discuss support topics with your peers, and learn from each other.
11-14-2013 03:08 AM
I am not familiar with c++ but I need to use some for my sqldatabase. I have looked at the Quotes, CRUD samples available but I need to tweak some of the bits for my app but, as I am not familiar with it, I am not sure how to.
Basically, I have a C++ class (db_class.cpp, .h) to help me write/edit my sqlite database. The examples given seems to use this to create the main.qml file directly. However, I do not want to do that as I need that main.qml to be created by another class. So the forms dealing with the database class directly would be a few different qml (like add.qml, update.qml), as well as components inside a ListView.
*For example, one of the things I need to do is to create a checkbox for each component in my Listview such that when the user presses a button, it will interact with the database and mark it true/false.
My questions are:
1) So should I use the db_class.cpp to create those multiple qml? If so how do I do that? I know the basic is:
QmlDocument *qml = QmlDocument::create("asset:///add.qml").parent(thi
AbstractPane *root = qml->createRootObject<AbstractPane>();
app->setScene(root);
But if I have a few files that will need to use the class, do I have to repeat all 3 lines? can I still call each *qml?
2) Is there a better way?
I am not sure which of the methods described in
Given that all I would need to do is interact with my class to modify the database via submit buttons, what is the best way that I can call on the c++ in qml?
Thanks!
11-14-2013 03:15 AM
11-14-2013 04:11 AM
I am not sure what you meant by create QML in QML. Do you mean to use the c++ to create a .qml file, and then to basically just include it inside another qml file as a Custom qml?
I have tried to do this in the mean time but it is actually causing the entire project to not built at all. It had also marked the line dbHelper *sqldatabase = new dbHelper(); as undefined reference to `dbHelper::dbHelper()'.
applicationui.cpp
#include "applicationui.hpp" #include "dbHelper.h" #include <bb/cascades/AbstractPane> #include <bb/cascades/Application> #include <bb/cascades/QmlDocument> #include <bb/data/SqlDataAccess> #include <bb/data/DataAccessError> #include <bb/system/SystemDialog> #include <QtSql/QtSql> #include <QDebug>
ApplicationUI::ApplicationUI(bb::cascades::Applica
tion *app) :tion *app) :
QObject(app)
{
dbHelper *sqldatabase = new dbHelper();
QmlDocument *qml = QmlDocument::create("asset:///main.qml").parent(th
is);is);
qml->setContextProperty("_sqlDatabase", sqldatabase);
// ... default set root code
}
I did not add anything to the applicationui.hpp
I am not sure what it means...
11-14-2013 04:14 AM
11-14-2013 04:17 AM
11-14-2013 04:34 AM - edited 11-14-2013 04:36 AM
After I cleaned and rebuilt it, it now causes more error including declaring that bb::cascades is not a recognised namespace
I have tried rebuilding it twice now, still the same problem!
(although the actual problem: my custom class, is now not throwing up an error by itself)
11-14-2013 04:35 AM
Yes, I have been using ComponentDefinition for the qml files.
I guess my question is, as I have seen from the samples, the 'sub' - qml files usually call on the c++ classes by _classname.someFunction();
For example, I will call on my 'edit.qml' file from my main.qml's ListView. On that page, it will then have a button that, onClicked, will probably trigger '_app.editRecord' or something.
For me, I am confused because in the examples, the 'app' class immediately creates the main.qml, and everything seems to flow from there. I do not want to create the 'main.qml' directly. So I want to INCLUDE the class so that say my 'edit.qml' (and maybe other qml files) can use the same class!
11-14-2013 04:43 AM
11-14-2013 05:48 AM
I guess it is because every single sample app does that, I am not sure what to do when I want to use more than one of these examples. For example, the BBM integration examples seem to want to do that too. I am not familiar enough with C++ to know how to modify at least one of them!
11-14-2013 05:51 AM | https://supportforums.blackberry.com/t5/Native-Development/Calling-c-in-qml-for-sql/m-p/2670643/highlight/true | CC-MAIN-2017-09 | refinedweb | 773 | 73.68 |
pycom
The
pycom module contains functions to control specific features of the Pycom devices, such as the heartbeat RGB LED.
Quick Usage Example
import pycom pycom.heartbeat(False) # disable the heartbeat LED pycom.heartbeat(True) # enable the heartbeat LED pycom.heartbeat() # get the heartbeat state pycom.rgbled(0xff00) # make the LED light up in green color
Methods
pycom.heartbeat([enable])
Get or set the state (enabled or disabled) of the heartbeat LED. Accepts and returns boolean values (
True or
False).
pycom.heartbeat_on_boot([enable])
Allows you permanently disable or enable the heartbeat LED. Once this setting is set, it will persist between reboots. Note, this only comes into effect on the next boot, it does not stop the already running heartbeat.
pycom.rgbled(color)
Set the colour of the RGB LED. The colour is specified as 24 bit value representing red, green and blue, where the red colour is represented by the 8 most significant bits. For instance, passing the value
0x00FF00 will light up the LED in a very bright green.
pycom.nvs_set(key, value)
Set the value of the specified key in the NVRAM memory area of the external flash. Data stored here is preserved across resets and power cycles. Value can only take 32-bit integers at the moment. Example:
import pycom pycom.nvs_set('temp', 25) pycom.nvs_set('count', 10)
pycom.nvs_get(key)
Get the value the specified key from the NVRAM memory area of the external flash. Example:
import pycom pulses = pycom.nvs_get('count')
If a non-existing key is given the returned value will be
None.
pycom.nvs_erase(key)
Erase the given key from the NVRAM memory area.
pycom.nvs_erase_all()
Erase the entire NVRAM memory area.
pycom.wifi_on_boot([enable])
Get or set the WiFi on boot flag. When this flag is set to
True, the AP with the default SSID (
lopy-wlan-xxx for example) will be enabled as part of the boot process. If the flag is set to False, the module will boot with WiFi disabled until it's enabled by the script via the
WLAN class. This setting is stored in non-volatile memory which preserves it across resets and power cycles. Example:
import pycom pycom.wifi_on_boot(True) # enable WiFi on boot pycom.wifi_on_boot() # get the wifi on boot flag
pycom.wdt_on_boot([enable])
Enables the WDT at boot time with the timeout in ms set by the function
wdt_on_boot_timeout. If this flag is set, the application needs to reconfigure the WDT with a new timeout and feed it regularly to avoid a reset.
import pycom pycom.wdt_on_boot(True) # enable WDT on boot pycom.wdt_on_boot() # get the WDT on boot flag
pycom.wdt_on_boot_timeout([timeout])
Sets or gets the WDT on boot timeout in milliseconds. The minimum value is 5000 ms.
import pycom pycom.wdt_on_boot_timeout(10000) # set the timeout to 5000ms pycom.wdt_on_boot_timeout() # get the WDT timeout value
pycom.pulses_get(pin, timeout)
Return a list of pulses at
pin. The methods scans for transitions at
pin and returns a list of tuples, each telling the pin value and the duration in microseconds of that value.
pin is a pin object, which must have set to
INP or
OPEN_DRAIN mode. The scan stops if not transitions occurs within
timeout milliseconds.
Example:
# get the raw data from a DHT11/DHT22/AM2302 sensor from machine import Pin from pycom import pulses_get from time import sleep_ms pin = Pin("G7", mode=Pin.OPEN_DRAIN) pin(0) sleep_ms(20) pin(1) data = pulses_get(pin, 100)
pycom.ota_start()
pycom.ota_write(buffer)
pycom.ota_finish()
Perform a firmware update. These methods are internally used by a firmware update though FTP. The update starts with a call to
ota_start(), followed by a series of calls to
ota_write(buffer), and is terminated with
ota_finish(). After reset, the new image gets active.
buffer shall hold the image data to be written, in arbitrary sizes. A block size of 4096 is recommended.
Example:
#()
Instead of reading the data to be written from a file, it can obviously also be received from a server using any suitable protocol, without the need to store it in the devices file system. | https://docs.pycom.io/firmwareapi/pycom/pycom.html | CC-MAIN-2019-26 | refinedweb | 679 | 68.57 |
On Thu, 03 Jan 2008 07:21:42 -0600 Ted Zlatanov <address@hidden> wrote: TZ> Third question: namespaces. I feel that it's much better TZ> for the user to store all the files in a single mailbox: TZ> INBOX.storage holds /a/b/c, /d/e/f, and /g/h/i TZ> I believe you proposed that instead we should auto-create: TZ> INBOX.storage.a.b to hold /a/b/c TZ> INBOX.storage.d.e to hold /d/e/f TZ> INBOX.storage.g.h to hold /g/h/i I realized there is a third option: don't allow directories. Everything is at the top level /, and make-directory fails. That would simplify the code tremendously though users may not like it. Ted | https://lists.gnu.org/r/tramp-devel/2008-01/msg00007.html | CC-MAIN-2021-43 | refinedweb | 127 | 75.91 |
A.
Creating graphics
The GNU Image Manipulation Program (GIMP)
It doesn’t need to be introduced. The GIMP is the ultimate software for graphics creation in the free software world. It’s so good all over that its toolkit has been adopted to create the Gnome desktop, it has been ported to most platforms able to support a colour screen, it is very often compared with the proprietary champion Adobe Photoshop... Now in version 2.2 (stable) or 2.3 (development), it makes use of top-notch input hardware (it really likes my Wacom Intuos3 tablet at least), provides clever functionalities and tools, and is getting much easier to use due to an increasingly better layout (version 1.x was often a mess to find the right tool, versions 2.x keep getting better).
Basically bitmap based, it is still able to import and generate paths and vector graphics for better resolution on some pieces of work: its layers manager is basically the same as the one used in Photoshop, apart from some nuances (and even then, that may just depend on the version it’s being compared to).
Version 2.3.12 handles ICC colour profiles, in both RGB and CMYK colour space—but there isn’t much you can do with it yet. More on that later.
Inkscape
Still not in its final version (0.44.1 at the time of writing), it is much better at managing vectors than the GIMP is; converting a bitmap into a path is a few clicks away, managing the curves and points is easy, creating contents, curve thickness, filling etc. is pretty well done... And it works on a slightly modified Software Vector Graphics (SVG) file format—meaning that you can actually see the result in the GIMP or in recent Mozilla browsers.
While you can define colours based on CMYK values, it doesn’t yet include the profile in the file, and is still RGB based. Yes, more on that later too.
Scribus
In the proprietary world, most publishers use Quark Xpress to define page layouts—or, sometimes, MS Publisher—but it doesn’t run on POSIX systems (yet). Which left the space open for Scribus, a Postscript-based desktop publishing application. Frankly, it works—pretty well (I must admit not having used it too much yet, I prefer OOo Writer for my simple work).
It can also work with RGB and CMYK colour spaces, and it can manage ICC profiles—but it won’t turn one into the other.
Of colour spaces and continuous headaches
RGB
It stands for Red-Green-Blue (it can sometimes be used to refer to ARGB, which is actually not the same), a way to code colour values on the three primary colours used by our eyes to reconstruct the light spectrum. Mixing red and green for example creates yellow, blue and red give magenta, blue and green give cyan... Because light frequencies cumulate (mixing high red, green and blue values of equal values give gray, none means black, all maxed out means pure white).
Given enough resolution (levels per colour channel), you can recreate most of the colour values. If you add a transparency value to this, you have basically recreated the whole range of perceived colours: it’s usually called an Alpha channel, and all four channels together are called an ARGB colour space. More often than not, each channel is coded on 8 bits (meaning 256 levels) which amounts to 4 billion possible values.
CMYK
Cyan, Magenta, Yellow, blacK are the four basic ink colours used in the printing industry to recreate most photographic content. Mixed on white paper, it allows one to recreate a lot of colours with little hassle—yet it has limitations.
Basically, if you define a printed photo as a series of dots, each would get more or less yellow, blue, magenta, or black ink; a little black and nothing else will appear gray, some yellow and blue, light green, magenta and cyan would make blue or purple (depending on how much magenta you use) and no ink would give... white.
There can be quite a lot of variations with this system, however. And that’s where it gets hard—it is intended to be used on a non luminous media (paper) which makes matching RGB and CMYK quite a hassle.
The price of this system is a lightly moired result on paper (due to all the dots used); when a document has a dominant colour, it may sometimes be much better to add an already mixed ink to the basic colours, so as to get better uniformity. It however adds one more printing pass to the media, thus usually resulting in a 20% printing price increase.
To give you an idea, the Pantone colour range (which covers over a thousand ink colours) when printed on a sampler makes each of those samplers over two thousand bucks apiece! If you get your hands on one (it’s supposed to fit in a big pocket), keep it—even worn down, it’s worth a lot.
Trouble in Paradise
Web pages are displayed on a screen; as such, web graphics are usually RGB based. So are cameras (snapshot or video) and scanners (they project harsh light on paper, making it “luminous”). Since screens are RGB based too, most graphics editing is done in the RGB space, since it requires little to no translation (at worst, a change in channel resolution).
But as soon as you need to print what you’ve painstakingly edited on paper, you’re in for a rough ride.
Basically, since both colour spaces are so different (one rates grayness on equivalent values of red, green and blue, the other rates grayness on the amount of black it puts in, one has an alpha channel, the other doesn’t...), you need translators; in fact, tables that match some values from one colour space to another. No absolute translation can be used (different inks, different papers, different screens), so you usually “glue” a value table to the source and a value table to the output, and ask the software to mix’n’match. Those tables are the ICC profiles I’ve mentioned previously.
RGB covers many colours that CMYK can’t do (bright white etc.), while CMYK does some stuff RGB can only hint at (hued blacks for example).
Desktop printers usually apply filters to whatever is sent their ways; they result in more vivid images, however they usually strip contrast off the result and don’t make use of the full CMYK capabilities—something a serious printing business can’t afford.
What to do then? Well, basically, values that overlap are kept pretty much as is, but non overlapping values are usually in the extremes, and those are over stretched upon translation.
As such, when converting a RGB image for printing, you need to take into account the discrepancies. And, in fact, you usually create your RGB image so as to make use of the translation process to make use of the broadest results range possible. But, if you don’t know about that, your bright green will look flat, the great yellows will turn greenish and the blues will turn purple. Interestingly, the reds are usually the ones that get the least change (probably because your eyes can’t get them very precisely, thus any corruption will go hardly noticed).
A brighter future
Now, the last thing that is missing to turn your GNU/Linux desktop into a free desktop publishing station is a tool to convert RGB to CMYK easily without need for too much juggling. And right now, the fine people of the GIMP are implementing just that; until version 2.2, you could use a plugin (called Separate) to artificially convert your RGB flat file into a 4 layers file where you could work on the colour calibration depending on profiles, but it was awkward and required a lot of finger crossing.
In version 2.3.12, you can now specify your RGB ICC profile, a CMYK ICC profile (download Adobe’s, they are freely available) and do some basic work on CMYK separated layers.
Too bad though, I still don’t know how to save or proof the result before I send it to printing... My colour printer has a crappy driver which doesn’t accept alternate colour profiles.
Now, if anyone has any knowledge on the Pantone colour range values, it would be terrific for the next phase: multi coloured printed media (much more precise than CMYK).
Krita
Don't forget Krita, which recently replaced GIMP on my desktop. And it also support CMYK among other nice features.
About Krita...
I must admit to not having tried Krita; I'm not using KDE, and installing Krita alone is a bit of a hassle; moreover, it is not available on platforms other than POSIX ones - while the GIMP is.
---
A computer is like air conditioning: it becomes useless when you open windows.
RE: About Krita...
I'm not using KDE, and installing Krita alone is a bit of a hassle
Just install KOffice from your package manager, it should pull everything in, shouldn't it?
it is not available on platforms other than POSIX ones
That is a weird reason for not mentioning a tool in an article called "Graphics creation on GNU/Linux".
weird reason, true...
...but you may want to transfer your in-progress image to another platform (say, a Mac) without going through a translation; thus, having the Gimp allows you to move your image from one platform to another without hassle, while it isn't so with Krita (which may very well handle Gimp images, but it isn't its native format - and we're talking precision work here).
Moreover, Krita is still young in its present incarnation. It may surpass the Gimp one day, sooner than later even, but personally I don't feel comfortable using 'young' software for professional work. When it reaches version 2, I'll very much reconsider it.
Now the tied-with-KDE thing: a distribution will almost always decide to freeze the version of KDE it ships, and Koffice gets the freeze too. Now if I want to update Krita, I have to update Koffice, and probably pieces of KDE along with it - which is far from practical, and leads to recompiles and tarball hell.
On the other hand, I can install an updated Gimp binary on pretty much any system (Linux, BSD, Mac, Win32...) that has a recent gtk+2 toolkit available, without need to touch the rest of the system.
As a side note, since I use Gnome, installing Krita results in over 250 Mb of packages to download just to get it to run. I get Konqueror and all the rest of kdebase with it, of that I could care less.
---
A computer is like air conditioning: it becomes useless when you open windows.
Inkscape
Inkscape adds a namespace to the the SVG format, but it is all compliant and whatnot. Most of the things you write about are being addressed in Inkscape's upcoming release.
Well then, as soon as it's
Well then, as soon as it's out I'll proof-test it; you do realise though that GIMP 2.2 was already supposed to support CMYK (but didn't), so I'll wait for the actual release to say more about this.
Please note that Inkscape got kudos for actually supporting CMYK, but the trick in pre-publishing is to be able to actually calibrate the result - something that is unfortunately quite difficult to do, and pretty much in alpha stage in the Free software world.
---
A computer is like air conditioning: it becomes useless when you open windows.
How about Xara?!
You ommited an important program: Xara!
It is now open-source and it's near release 1.0, which means it's about to match the commercial version in terms of free functionality.
I read that Pantone will be available to Xara Linux in a commercial version. Why only in the commercial version? Well, you could say that Pantone is a proprietary colour technology.
Anyway, just try Xara and you'll be impressed, especially by its speed and rendering quality compared to Inkskape. It also has a far much more appealing user interface then Inkscape. The Inkscape team really needs to put more work in the interface.
I've heard about Xara
It is indeed very interesting and is a professional-grade tool. Last time I looked at it though (it was a few months ago, still), it was far from complete and had some severe stability problems. It probably got better, and I'm eager to test the release 1.0 version.
The Pantone colour range needs licencing and certification, sadly any serious prepress business requires it. Now if a project called, say, Phantome, managed to get VERY close to the Pantone colour range...
---
A computer is like air conditioning: it becomes useless when you open windows.
Graphics rendition
Graphics rendition would better fit what you convey, huh ?
________________________
Let's go party.
xara extreme
xara extreme is now open source for linux as well. It a svg tool like Inkscape. I like Inkscape MUCH more though. I think it may just be because I'm used to it.
graphics
I agree.
BUT, I'm searching for a Linux programwith the ease of use SMARTDRAW. QCAD is to complicated to use now and then. That's one of the two reasons for me for needing a dual boot system with Win XP.
I need to draw navigational figures, mainly vectors and some figures like a circle, a trangle and a figure resembling a boat (with and without sails).
The second reason is an online bridgeprogram STEPBRIDGE that does not WANT to function with WINE.
Any suggestions.
Thanks from Belgium
Qcad, SmartDraw... huh?
I'm not sure I see your point: SmartDraw is a flow chart creation software (which could be replaced with, say, Kchart and Kformula) which may have more powerful CAD drawing capabilities, which Qcad could supplement.
You need to learn how to separate WHAT you want to do from what a piece of software can do. Remember that most free softwares are modular in design (they come from the desire to scratch someone's particular itch), not monolithic like SmartDraw is, so you may install one piece of software for one particular use:
- Kchart for fast or evolved charts,
- Kformula for math formulas,
- Qcad for CAD drawing,
- The Gimp or Krita for pixel and layer based drawings,
- Xara or Inkscape for vector based drawings...
- OOo or Koffice for office productivity work,
- Scribus for pre-print pagination.
---
A computer is like air conditioning: it becomes useless when you open windows.
The GIMP does support CMYK
You just need to insall the module, for whatever reason (perhaps stability) it is not included by default, but it is available...
What module?
On versions 2.2 and earlier, I installed the 'separate' plugin. It indeed works, at a very basic level though (I haven't found any other CMYK plugin for the GIMP after quite an extensive search on the Web). Version 2.3 uses a different approach though. Maybe by the time 2.4 is out, we'll have a 'real' CMYK manager in the GIMP...?
---
A computer is like air conditioning: it becomes useless when you open windows.
Does any seriouse print professionals using linux out there?
Hi, Meyran thanks!! for sharing your knowledge with us. I am freelance designer. I too want to shift to linux as my primary os for print desginging. I need apps for ad designing and layout designing. In short to replace my Indesign and illustrator.
For layout scribus seems to be best choice. But don't know about its output capabilties. Does it outputs in cmyk format. How is the quality of the output. Does it mactch with of Quark and Indesign.
For ad desiging and creative work i think inkscape is best. But it exports to png only which too is rgb. How will i use for print publishing.
And the most important question i have is : Is any serious print professional using linux. Or i will be the only fool doing so. Is linux cmyk capabilities still not mature enough for cmyk printing.
What apps should i use if i need to work for Print publishing.
Please suggest. Thanking you in anticipation.
Regards
Leo
short answer
Right now, if print publishing is your bread n butter, stick with your current platform (probably MacOS). If your use of it is more incidental (one ad design every now and then, or graphically light composing) then I don't think you'd find yourself alone; at least, a lot of Web graphics designers do use Linux.
Check out this guy: Ayo of 73lab (), for successful ad/print/Web design under Linux.
Under Linux, I know that earlier versions of Photoshop actually work quite well under Crossover Office. Dunno about more recent versions though.
Color (including CMYK) profiles are supported by Linux and X. I know that personally I managed to use Adobe's ICC profiles under several apps. X can be calibrated for R, G and B channels and is provided with a basic calibration tool (but it is always better to calibrate your screen first).
Scribus outputs PostScript format; in short, same as AdobeAcrobat, and it does support CMYK (what it doesn't support is converting RGB to CMYK). Its quality is quoted as being on par with Acrobat's.
Inkscape stores colors as RGB, but gives equivalence in CMYK colors. Presumably, version 0.5 should support embedded color profiles (and CMYK too). It outputs SVG, but exports PNG.
Presumably, you're better off creating your artwork under Inkscape, import the SVG under the Gimp - which will then do a vector rendering to bitmap - and calibrate it using the same source and destination profiles, for better consistency.
---
A computer is like air conditioning: it becomes useless when you open windows. | http://www.freesoftwaremagazine.com/comment/41463 | CC-MAIN-2015-35 | refinedweb | 3,015 | 70.43 |
MIke Milinkovich of the Eclipse Foundation has just published an important update on the Jakarta EE project. As noted in a prior post here, and in Dmitry's blog, Eclipse GlassFish 5.1 has been certified as Java EE 8 compatible. We intend for Eclipse GlassFish to become a compatible implementation of Jakarta EE 8 specifications. In addition, Oracle Java EE 8 TCK sources are available now at Jakarta EE. We intend to evolve them to become the Jakarta EE 8 TCKs that will verify compatibility with Jakarta EE 8 specifications. So we have the core technologies in place to deliver a Jakarta EE 8 platform, and commitment and funding from major vendors to make it happen.
The next phase in Jakarta EE Platform delivery is delivery of the specifications themselves. The Jakarta EE Working Group has defined the Jakarta EE Specification Process, and work is underway to begin execution of this process. Oracle and Eclipse had jointly hoped to come to agreement on terms that would allow the evolution of the javax package namespace and use of Java trademarks in Jakarta EE specifications. Unfortunately, we have been unable to agree on such terms. Mike has described the implications in his post, which reflects the review and consensus of the full Jakarta EE Working Group. I will not repeat this all here, but we will proceed on the basis of the agreement we have reached.
From Oracle's perspective, we remain committed to work with the Jakarta EE Working Group and the Jakarta EE Specification Process to create the Jakarta EE Platform. I believe the other members of the Jakarta EE Working Group feel the same way. We intend to deliver a Jakarta EE 8 Platform and evolve that Platform going forward so that the entire community can contribute to, and leverage, Jakarta EE. We have key technologies, strong leadership from key vendors, and broad engagement from the community, and the right place at the Eclipse Foundation, the home of Jakarta EE and MicroProfile, to evolve cloud native Java technology. And Oracle continues to evolve our support for WebLogic Server running in Kubernetes, improve our MicroProfile support in Helidon, and work towards delivery of Java EE 8 (and Jakarta EE 8) support in WebLogic Server soon. Expect to hear more from us in coming days and weeks. | https://blogs.oracle.com/theaquarium/jakarta-ee-update | CC-MAIN-2021-04 | refinedweb | 387 | 50.97 |
FITS File handling (
astropy.io.fits)¶
Introduction¶
The
astropy.io.fits package provides access to FITS files. FITS
(Flexible Image Transport System) is a portable file standard widely used in
the astronomy community to store images and tables.
Getting Started¶
This section provides a quick introduction of using
astropy.io.fits. The
goal is to demonstrate the package’s basic features without getting into too
much detail. If you are a first time user or have never used Astropy or PyFITS,
this is where you should start. See also the FAQ for
answers to common questions/issues.
Note
If you want to read or write a single table in FITS format then the simplest method is often via the high-level Unified file read/write interface. In particular see the Unified I/O FITS section.
Reading and Updating Existing FITS Files¶
Opening a FITS file¶
Note
The
astropy.io.fits.util.get_testdata_filepath() function,
used in the examples here, is for accessing data shipped with Astropy.
To work with your own data instead, please use
astropy.io.fits.open(),
which takes either relative or absolute path.
Once the
astropy.io.fits package is loaded using the standard convention
[1], we can open an existing FITS file:
>>> from astropy.io import fits >>> fits_image_filename = fits.util.get_testdata_filepath('test0.fits') >>> hdul = fits.open(fits_image_filename)
The
open() function has several optional arguments which will be
discussed in a later chapter. The default mode, as in the above example, is
“readonly”. The open function returns an object called an
HDUList
which is a
list-like collection of HDU objects. An HDU (Header Data Unit) is
the highest level component of the FITS file structure, consisting of a header
and (typically) a data array or table.
After the above open call,
hdul[0] is the primary HDU,
hdul[1] is
the first extension HDU, etc (if there are any extensions), and so on. It
should be noted that Astropy is using zero-based indexing when referring to
HDUs and header cards, though the FITS standard (which was designed with
FORTRAN in mind) uses one-based indexing.
The
HDUList has a useful method
HDUList.info(), which
summarizes the content of the opened FITS file:
>>> you are done with the opened file, close it with the
HDUList.close() method:
>>> hdul.close()
You can avoid closing the file manually by using
open() as context
manager:
>>> with fits.open(fits_image_filename) as hdul: ... exiting the
with scope the file will be closed automatically. That’s
(generally) the preferred way to open a file in Python, because it will close
the file even if an exception happens.
If the file is opened with
lazy_load_hdus=False, all of the headers will
still be accessible after the HDUList is closed. The headers and data may or
may not be accessible depending on whether the data are touched and if they
are memory-mapped, see later chapters for detail.
Working with large files¶
The
open() function supports a
memmap=True argument that allows the
array data of each HDU to be accessed with mmap, rather than being read into
memory all at once. This is particularly useful for working with very large
arrays that cannot fit entirely into physical memory. Here
memmap=True by default, and this value is obtained from the configuration item
astropy.io.fits.Conf.use_memmap.
This has minimal impact on smaller files as well, though some operations, such as reading the array data sequentially, may incur some additional overhead. On 32-bit systems arrays larger than 2-3 GB cannot be mmap’d (which is fine, because by that point you’re likely to run out of physical memory anyways), but 64-bit systems are much less limited in this respect. integers. For example, when writing
the value
0 as an unsigned 32-bit integer, it is stored in the FITS
file as
-32768, along with the header keyword
BZERO = 32768.
Astropy recognizes and applies this convention by default, so that all data
that looks like it should be interpreted as unsigned integers is automatically
converted (this applies to both images and tables). In Astropy versions prior
to v1.1.0 this was not applied automatically, and it is necessary to pass the
argument
uint=True to
open(). In v1.1.0 or later this is the
default.
Even with
uint=False, the
BZERO shift is still applied, but the
returned array is of “float64” type. To disable scaling/shifting entirely, use
do_not_scale_image_data=True (see Why is an image containing integer data being converted unexpectedly to floats? in the FAQ
for more details).
Working with compressed files¶
Note. Keywords
are usually unique within a header, except in a few special cases.
The header attribute is a Header instance, another Astropy object. To get the value associated with a header keyword, simply do (a la Python dicts):
>>> hdul = fits.open(fits_image_filename) >>> hdul[0].header['DATE'] '01/04/99'
to get the value of the keyword “DATE”, which is a string ‘01/04/99’.
Although keyword names are always in upper case inside the FITS file,
specifying a keyword name with Astropy is case-insensitive, for the user’s
convenience. If the specified keyword name does not exist, it will raise a
KeyError exception.
We can also get the keyword value by indexing (a la Python lists):
>>> hdul[0].header[7] 32768.0
This example returns the 8th (like Python lists, it is 0-indexed) keyword’s value–a float–32768.0.
Similarly, it is easy to update a keyword’s value in Astropy, either through keyword name or index:
>>> hdr = hdul[0].header >>> hdr['targname'] = 'NGC121-a' >>> hdr[27] = 99
Please note however that almost all application code should update header values via their keyword name and not via their positional index. This is because most FITS keywords may appear at any position in the header.
It is also possible to update both the value and comment associated with a keyword by assigning them as a tuple:
>>> hdr = hdul[0].header >>> hdr['targname'] = ('NGC121-a', 'the observation target') >>> hdr['targname'] 'NGC121-a' >>> hdr.comments['targname'] 'the observation target'
Like a dict, one may also use the above syntax to add a new keyword/value pair (and optionally a comment as well). In this case the new card is appended to the end of the header (unless it’s a commentary keyword such as COMMENT or HISTORY, in which case it is appended after the last card with that keyword).
Another way to either update an existing card or append a new one is to use the
Header.set() method:
>>> hdr.set('observer', 'Edwin Hubble')
Comment or history records are added like normal cards, though in their case a new card is always created, rather than updating an existing HISTORY or COMMENT card:
>>> hdr['history'] = 'I updated this file 2/26/09' >>> hdr['comment'] = 'Edwin Hubble really knew his stuff' >>> hdr['comment'] = 'I like using HST observations' >>> hdr['history'] I updated this file 2/26/09 >>> hdr['comment'] Edwin Hubble really knew his stuff I like using HST observations
Note: Be careful not to confuse COMMENT cards with the comment value for normal cards.
To update existing COMMENT or HISTORY cards, reference them by index:
>>> hdr['history'][0] = 'I updated this file on 2/27/09' >>> hdr['history'] I updated this file on 2/27/09 >>> hdr['comment'][1] = 'I like using JWST observations' >>> hdr['comment'] Edwin Hubble really knew his stuff I like using JWST observations
To see the entire header as it appears in the FITS file (with the END card and
padding stripped), simply enter the header object by itself, or
print(repr(hdr)):
>>> hdr SIMPLE = T / file does conform to FITS standard BITPIX = 16 / number of bits per data pixel NAXIS = 0 / number of data axes ... >>> print(repr(hdr)) SIMPLE = T / file does conform to FITS standard BITPIX = 16 / number of bits per data pixel NAXIS = 0 / number of data axes ...
Entering simply
print(hdr) will also work, but may not be very legible
on most displays, as this displays the header as it is written in the FITS file
itself, which means there are no linebreaks between cards. This is a common
source of confusion for new users.
It’s also possible to view a slice of the header:
>>> hdr[:2] SIMPLE = T / file does conform to FITS standard BITPIX = 16 / number of bits per data pixel
Only the first two cards are shown above.
To get a list of all keywords, use the
Header.keys() method just as you
would with a dict:
>>> list(hdr.keys()) ['SIMPLE', 'BITPIX', 'NAXIS', ...]
Examples:
See also Edit a FITS header.
Working with Image Data¶
If an HDU’s data is an image, the data attribute of the HDU object will return
a numpy
ndarray object. Refer to the numpy documentation for details
on manipulating these numerical arrays:
>>> data = hdul[1].data
Here,
data points to the data object in the second HDU (the first HDU,
hdul[0], being the primary HDU) which corresponds to the ‘SCI’
extension. Alternatively, you can access the extension by its extension name
(specified in the EXTNAME keyword):
>>> data = hdul['SCI'].data
If there is more than one extension with the same EXTNAME, the EXTVER value needs to be specified along with the EXTNAME as a tuple; e.g.:
>>> data = hdul['sci',2].data
Note that the EXTNAME is also case-insensitive.
The returned numpy object has many attributes and methods for a user to get information about the array, e.g.:
>>> data.shape (40, 40) >>> data.dtype.name 'int16'
Since image data is a numpy object, we can slice it, view it, and perform mathematical operations on it. To see the pixel value at x=5, y=2:
>>> print(data[1, 4]) 348
Note that, like C (and unlike FORTRAN), Python is 0-indexed and the indices have the slowest axis first and as:
>>> data[30:40, 10:20] array([[350, 349, 349, 348, 349, 348, 349, 347, 350, 348], [348, 348, 348, 349, 348, 349, 347, 348, 348, 349], [348, 348, 347, 349, 348, 348, 349, 349, 349, 349], [349, 348, 349, 349, 350, 349, 349, 347, 348, 348], [348, 348, 348, 348, 349, 348, 350, 349, 348, 349], [348, 347, 349, 349, 350, 348, 349, 348, 349, 347], [347, 348, 347, 348, 349, 349, 350, 349, 348, 348], [349, 349, 350, 348, 350, 347, 349, 349, 349, 348], [349, 348, 348, 348, 348, 348, 349, 347, 349, 348], [349, 349, 349, 348, 350, 349, 349, 350, 348, 350]], dtype=int16)
To update the value of a pixel or a sub-section:
>>> data[30:40, 10:20] = data[1, 4] = 999
This example changes the values of both the pixel [1, 4] and the sub-section [30:40, 10:20] to the new value of 999. See the Numpy documentation for more details on Python-style array indexing and slicing.
The next example of array manipulation is to convert the image data from counts to flux:
>>> photflam = hdul[1].header['photflam'] >>> exptime = hdr['exptime'] >>> data = data * photflam / exptime >>> hdul.close()).
Examples:
See also Read and plot an image from a FITS file.
Working With Table Data¶
This section describes reading and writing table data in the FITS format using
the
fits package directly. For simple cases, however, the
high-level Unified file read/write interface will often suffice and is somewhat easier to use.
See the Unified I/O FITS section for details.
Like images, the data portion of a FITS table extension is in the
.data
attribute:
>>> fits_table_filename = fits.util.get_testdata_filepath('tb.fits') >>> hdul = fits.open(fits_table_filename) >>> data = hdul[1].data # assuming the first extension is a table
If you are familiar with numpy
recarray (record array) objects, you
will find the table data is basically a record array with some extra
properties. But familiarity with record arrays is not a prerequisite for this
guide.
To see the first row of the table:
>>> print(data[0]) (1, 'abc', 3.7000000715255736, False)
Each row in the table is a
FITS_record object which looks like a
(Python) tuple containing elements of heterogeneous data types. In this
example: an integer, a string, a floating point number, and a Boolean value. So
the table data are just an array of such records. More commonly, a user is
likely to access the data in a column-wise way. This is accomplished by using
the
field() method. To get the first column (or “field” in
Numpy parlance–it is used here interchangeably with “column”) of the table,
use:
>>> data.field(0) array([1, 2]...)
A numpy object with the data type of the specified field is returned.
Like header keywords, a column can be referred either by index, as above, or by name:
>>> data.field('c1') array([1, 2]...)
When accessing a column by name, dict-like access is also possible (and even preferable):
>>> data['c1'][1].columns
This attribute is a
ColDefs (column definitions) object. If we use the
ColDefs.info() method from the interactive prompt:
>>> cols.info() name: ['c1', 'c2', 'c3', 'c4'] format: ['1J', '3A', '1E', '1L'] unit: ['', '', '', ''] null: [-2147483647, '', '', ''] bscale: ['', '', 3, ''] bzero: ['', '', 0.4, ''] disp: ['I11', 'A3', 'G15.7', 'L6'] start: ['', '', '', ''] dim: ['', '', '', ''] coord_type: ['', '', '', ''] coord_unit: ['', '', '', ''] coord_ref_point: ['', '', '', ''] coord_ref_value: ['', '', '', ''] coord_inc: ['', '', '', ''] time_ref_pos: ['', '', '', '']
it will show the attributes of all columns in the table, such as their names, formats, bscales, bzeros, etc. A similar output that will display the column names and their formats can be printed from within a script with:
>>> hdul[1].columns ColDefs( name = 'c1'; format = '1J'; null = -2147483647; disp = 'I11' name = 'c2'; format = '3A'; disp = 'A3' name = 'c3'; format = '1E'; bscale = 3; bzero = 0.4; disp = 'G15.7' name = 'c4'; format = '1L'; disp = 'L6' )
We can also get these properties individually; e.g.:
>>> cols.names ['c1', 'c2', 'c3', 'c4']
returns a (Python) list of field names.
Since each field is a Numpy object, we’ll have the entire arsenal of Numpy tools to use. We can reassign (update) the values:
>>> data['c4'][:] = 0
take the mean of a column:
>>> data['c3'].mean() 5.19999989271164
and so on.
Examples:
See also Accessing data stored as a table in a multi-extension FITS (MEF) file.
Save File Changes¶
As mentioned earlier, after a user opened a file, made a few changes to either
header or data, the user can use
HDUList.writeto() to save the changes.
This takes the version of headers and data in memory and writes them to a new
FITS file on disk. Subsequent operations can be performed to the data in memory
and written out to yet another different file, all without recopying the
original data to (more) memory:
hdul.writeto('newtable.fits')
will write the current content of
hdulist to a new disk file newfile.fits.
If a file was opened with the update mode, the
HDUList.flush() method can
also be used to write all the changes made since
open(), back to the
original file. The
close() method will do the same for a FITS
file opened with update mode:
with fits.open('original.fits', mode='update') as hdul: # Change something in hdul. hdul.flush() # changes are written back to original.fits # closing the file will also flush any changes and prevent further writing
Creating a New FITS File¶
Creating a New Image File¶
So far we have demonstrated how to read and update an existing FITS file. But how about creating a new FITS file from scratch? Such tasks are very easy in Astropy for an image HDU. We’ll first demonstrate how to create a FITS file consisting only the primary HDU with image data.
First, we create a numpy object for the data part:
>>> import numpy as np >>> n = np.arange(100.0) # a simple sequence of floats from 0.0 to 99.9
Next, we create a
PrimaryHDU object to encapsulate the data:
>>> hdu = fits.PrimaryHDU(n)
We then create a HDUList to contain the newly created primary HDU, and write to a new file:
>>> hdul = fits.HDUList([hdu]) >>> hdul.writeto('new1.fits')
That’s it! In fact, Astropy even provides a shortcut for the last two lines to accomplish the same behavior:
>>> hdu.writeto('new2.fits')
This will write a single HDU to a FITS file without having to manually
encapsulate it in an
HDUList object first.
Creating a New Table File¶
Note
If you want to create a simple binary FITS table with no other HDUs,
you can use
Table instead and then write to FITS.
This is less complicated than “lower-level” FITS interface:
>>> from astropy.table import Table >>> t = Table([[1, 2], [4, 5], [7, 8]], names=('a', 'b', 'c')) >>> t.write('table1.fits', format='fits')
The equivalent code using
astropy.io.fits would look like this:
>>> from astropy.io import fits >>> import numpy as np >>> c1 = fits.Column(name='a', array=np.array([1, 2]), format='K') >>> c2 = fits.Column(name='b', array=np.array([4, 5]), format='K') >>> c3 = fits.Column(name='c', array=np.array([7, 8]), format='K') >>> t = fits.BinTableHDU.from_columns([c1, c2, c3]) >>> t.writeto('table2.fits')
To create a table HDU is a little more involved than image HDU, because a table’s structure needs more information. First of all, tables can only be an extension HDU, not a primary. There are two kinds of FITS table extensions: ASCII and binary. We’ll use binary table examples here.
To create a table from scratch, we need to define columns first, by
constructing the
Column objects and their data. Suppose we have two
columns, the first containing strings, and the second containing floating point
numbers:
>>> import numpy as np >>> a1 = np.array(['NGC1001', 'NGC1002', 'NGC1003']) >>> a2 = np.array([11.1, 12.3, 15.2]) >>> col1 = fits.Column(name='target', format='20A', array=a1) >>> col2 = fits.Column(name='V_mag', format='E', array=a2)
Note
It is not necessary to create
Column object explicitly
if the data is stored in a
structured array.
Next, create a
ColDefs (column-definitions) object for all columns:
>>> cols = fits.ColDefs([col1, col2])
Now, create a new binary table HDU object by using the
BinTableHDU.from_columns() function:
>>> hdu = fits.BinTableHDU.from_columns(cols)
This function returns (in this case) a
BinTableHDU.
Of course, you can do this more concisely without creating intermediate
variables for the individual columns and without manually creating a
ColDefs object:
>>> hdu = fits.BinTableHDU.from_columns( ... [fits.Column(name='target', format='20A', array=a1), ... fits.Column(name='V_mag', format='E', array=a2)])
Now you may write this new table HDU directly to a FITS file like so:
>>> hdu.writeto('table3:
>>> hdr = fits.Header() >>> hdr['OBSERVER'] = 'Edwin Hubble' >>> hdr['COMMENT'] = "Here's some commentary about this FITS file." >>> primary_hdu = fits.PrimaryHDU(header=hdr)
When we create a new primary HDU with a custom header as in the above example,
this will automatically include any additional header keywords that are
required by the FITS format (keywords such as
SIMPLE and
NAXIS for
example). In general, users should not have to manually manage such keywords,
and should only create and modify observation-specific informational keywords.
We then create a HDUList containing both the primary HDU and the newly created table extension, and write to a new file:
>>> hdul = fits.HDUList([primary_hdu, hdu]) >>> hdul.writeto('table4.fits')
Alternatively, we can append the table to the HDU list we already created in the image file section:
>>> hdul.append(hdu) >>> hd
astropy.io.fits. In the
following chapters we’ll show more advanced examples and explain options in
each class and method.
Examples:
See also Create a multi-extension FITS (MEF) file from scratch.
Convenience Functions¶
astropy.io.fits.
The first of these functions is
getheader(), to get the header of an HDU.
Here are several examples of getting the header. Only the file name is required
for this function. The rest of the arguments are optional and flexible to
specify which HDU the user wants to access:
>>> from astropy.io.fits import getheader >>> hdr = getheader(fits_image_filename) # get default HDU (=0), i.e. primary HDU's header >>> hdr = getheader(fits_image_filename, 0) # get primary HDU's header >>> hdr = getheader(fits_image_filename, 2) # the second extension >>> hdr = getheader(fits_image_filename, 'sci') # the first HDU with>> hdr = getheader(fits_image_filename, 'sci', 2) # HDU with>> hdr = getheader(fits_image_filename, extname='sci', extver=2)
Ambiguous specifications will raise an exception:
>>> getheader(fits_image_filename, ext=('sci', 1), extname='err', extver=2) Traceback (most recent call last): ... TypeError: Redundant/conflicting extension arguments(s): ...
After you get the header, you can access the information in it, such as getting and modifying a keyword value:
>>> fits_image_2_filename = fits.util.get_testdata_filepath('o4sp040b0_raw.fits') >>> hdr = getheader(fits_image_2_filename, 0) # get primary hdu's header >>> filter = hdr['filter'] # get the value of the keyword "filter' >>> val = hdr[10] # get the 11th keyword's value >>> hdr['filter'] = 'FW555' # change the keyword value
For the header keywords, the header is like a dictionary, as well as a list. The user can access the keywords either by name or by numeric index, as explained earlier in this chapter.
If a user only needs to read one keyword, the
getval() function can
further simplify to just one call, instead of two as shown in the above
examples:
>>> from astropy.io.fits import getval >>> # get 0th extension's keyword FILTER's value >>> flt = getval(fits_image_2_filename, 'filter', 0) >>> flt 'Clear' >>> # get the 2nd sci extension's 11th keyword's value >>> val = getval(fits_image_2_filename, 10, 'sci', 2) >>> val False
The function
getdata() gets the data of an HDU. Similar to
getheader(), it only requires the input FITS file name while the
extension is specified through the optional arguments. It does have one extra
optional argument header. If header is set to True, this function will return
both data and header, otherwise only data is returned:
>>> from astropy.io.fits import getdata >>> # get 3rd sci extension's data: >>> data = getdata(fits_image_filename, 'sci', 3) >>> # get 1st extension's data AND header: >>> data, hdr = getdata(fits_image_filename, 1, header=True)
The functions introduced above are for reading. The next few functions demonstrate convenience functions for writing:
>>> fits.writeto('out.fits', data, hdr)
The
writeto() function uses the provided data and an optional header to
write to an output FITS file.
>>> fits.append('out.fits', data, hdr)
The
append() function will use the provided data and the optional header
to append to an existing FITS file. If the specified output file does not
exist, it will create one.
from astropy.io.fits import update update(filename, dat, hdr, 'sci') # update the 'sci' extension update(filename, dat, 3) # update the 3rd extension update(filename, dat, hdr, 3) # update the 3rd extension update(filename, dat, 'sci', 2) # update the 2nd SCI extension update(filename, dat, 3, header=hdr) # update the 3rd extension update(filename, dat, header=hdr, ext=5) # update the 5th extension
The
update() function will update the specified extension with the input
data/header. The 3rd argument can be the header associated with the data. If
the 3rd argument is not a header, it (and other positional arguments) are
assumed to be the extension specification(s). Header and extension specs can
also be keyword arguments.
The
printdiff() function will print a difference report of two FITS files,
including headers and data. The first two arguments must be two FITS
filenames or FITS file objects with matching data types (i.e., if using strings
to specify filenames, both inputs must be strings). The third
argument is an optional extension specification, with the same call format
of
getheader() and
getdata(). In addition you can add any keywords
accepted by the
FITSDiff class
from astropy.io.fits import printdiff # get a difference report of ext 2 of inA and inB printdiff('inA.fits', 'inB.fits', ext=2) # ignore HISTORY and COMMMENT keywords printdiff('inA.fits', 'inB.fits', ignore_keywords=('HISTORY','COMMENT')
Finally, the
info() function will print out information of the specified
FITS file:
>>> fits.info(fits_image_filename)
This is one of the most useful convenience functions for getting an overview of what a given file contains without looking at any of the details.
Using
astropy.io.fits¶
- FITS Headers
- Image Data
- Table Data
- Verification
- Less Familiar Objects
- Executable Scripts
- Miscellaneous Features
Command-line utilities¶
For convenience, several of Astropy’s subpackages install utility programs on your system which allow common tasks to be performed without having to open a Python interpreter. These utilities include:
fitsheader: prints the headers of a FITS file.
fitscheck: verifies and optionally re-writes the CHECKSUM and DATASUM keywords of a FITS file.
- fitsdiff: compares two FITS files and reports the differences.
- Scripts: converts FITS images to bitmaps, including scaling and stretching.
- wcslint: checks the WCS keywords in a FITS file for compliance against the standards.
Other Information¶
Reference/API¶
A package.
- File Handling and Convenience Functions
- HDU Lists
- Header Data Units
- Headers
- Cards
- Tables
- Images
- Differs
- Verification options
Footnotes | https://docs.astropy.org/en/stable/io/fits/ | CC-MAIN-2019-13 | refinedweb | 4,116 | 54.83 |
Hello programmers, in today’s article, we will discuss the Matplotlib ylim() in Python. The Matplotlib library in Python is a numerical – mathematical extension for the NumPy library. The Pyplot module of the Matplotlib library is a state-based interface providing MATLAB-like features. The matplotlib.pyplot.ylim() function is used to get or set the y-limits of the current axes. Before we cite examples for the matplotlib ylim() function, let me briefly brief you with the syntax and return type.
Syntax of Matplotlib ylim()
matplotlib.pyplot.ylim(*args, **kwargs)
Parameters:
- bottom: This parameter sets the ylim to bottom.
- top: This parameter sets the ylim to top.
- **kwargs: Text properties that are used to control the appearance of the labels.
Return type
The matplotlib ylim() function returns:
bottom, top : The tuple of the new y-axis limits.
Example of Matplotlib ylim() in Python
# Implementation of matplotlib function import matplotlib.pyplot as plt import numpy as np.title(" matplotlib.pyplot.ylim() Example") plt.show()
OUTPUT:
EXPLANATION:
In the above example, first, the subplot of the figure is defined. Then the figure plots by passing parameters to the plt.plot() function. Also, annotation added for the plot using the plt.annotate() function. The text to be annotated is ‘local max’ placed at the position x = 3 and y = 1.5. Finally, we have set the Matplotlib ylim as plt.ylim(-2, 2). We get the y -limits for the y-axis from -2 to 2. Thus, -2 is the bottom limit, and 2 is the top limit for the y – axis.
Matplotlib ylim() default
import matplotlib.pyplot as plt fig = plt.figure() a1 = fig.add_axes([0,0,1,1]) import numpy as np x = np.arange(1,10) a1.plot(x, np.log(x)) a1.set_title('Logarithm') plt.show()
OUTPUT:
EXPLANATION:
In the above example, an array ‘x’ is defined using np.arrange(1, 10). And it is plotted bypassing the np.log(x) argument to the a1.plot() function. Since log(x) is used, a logarithmic plot is obtained. But, the limits for the x-axis and y-axis have not been mentioned explicitly. So the plot takes default values of xlim() and ylim(). As a result, the limit of the x-axis is from 1 to 9. And the bottom limit of the y-axis is 0, and 2.0 is the top limit. To mention limits for the y-axis as per our choice, the set_ylim() method exists.
Set axis range using Matplotlib ylim()
import matplotlib.pyplot as plt import numpy as np # creating an empty object a= plt.figure() axes= a.add_axes([0.1,0.1,0.8,0.8]) # adding axes x= np.arange(0,11) axes.plot(x,x**3, marker='*') axes.set_ylim([0,25]) plt.show()
OUTPUT:
EXPLANATION:
In the above example, we have created a plot of x-coordinates of 0 to 10. The y-coordinates are to be the cube of each of these x-coordinates. We thus modify the range of the y-coordinates from 0 to 25 by using the set_ylim() function. The set_ylim() function takes two arguments, i.e., the lower limit as 0 and the upper limit as 25, to change the y-axis range.
Matplotlib ylim() in Python to reverse axis
import numpy as np import matplotlib.pyplot as plt x=np.linspace(-3,3,100) y=3*x+4 plt.plot(x, y) plt.title("Reverted axes") plt.xlim(max(x),min(x)) plt.ylim(max(y),min(y)) plt.show()
OUTPUT:
EXPLANATION:
The xlim() and ylim() functions are used to set or get limits for X-axis and Y-axis. If we pass the maximum value in the axis as the lower limit and the minimum value in the axis as the upper limit in the above functions, we get a reverted axis. We have passed max(x) as the lower limit and min(x) as the upper limit, which consequently reverses the axis.
Conclusion:
In this article, we learned about implementing the Matplotlib ylim() in python programs. We discussed how to set axis range and also reverse axis using the ylim() function. When the limits of axes are not mentioned, it uses the default value of xlim() and ylim() for the plot. Refer to this article in case of any queries regarding the Matplolib ylim() function.
However, if you have any doubts or questions, do let me know in the comment section below. I will try to help you as soon as possible.
Happy Pythoning! | https://www.pythonpool.com/matplotlib-ylim/ | CC-MAIN-2021-43 | refinedweb | 751 | 68.67 |
HY-SRF05 // Again
- Login or register to post comments
- by falconunknown
January 24, 2013
Hi.
I have read this:
HY-SRF05 //
Start here robot ultrasonic sensor //
I want to build this bot:
Beta of Next generation "Start here robot" //
So, I bought this items:
- Picaxe 28x2 (Axe401)
- Instant robot shield (Axe408)
- HY-SRF05 ultrasonic sensor
I have tried to test the sensor but I don't know if really works, I can only hear one kind of sound, even if I bring my hand or anything else close of the sensor.
I have added a picture to have a better idea.
Also, I have read many datasheets and I found two modes of wires connection (single pin mode // dual pin mode).
So, ultra command is used with SINGLE pin mode connection (It also have 2 modes: 5 way header or 3 way header)...
And pulsin/pulsout commands are used with DUAL pin mode connection?
Am I right?
I noticed in SRF005 datasheet, the order of pins (Vcc / Echo / Trigger / Mode / Gnd).
Vs
The order of HY-SRF05 pins (Vcc / Trigger / Echo / OUT / Gnd).
It matter?
I tried connecting the wires of sensor in the same order:
Sensor = (Vcc / Trigger / Echo / OUT / Gnd)
To
Board = (Vcc / Trigger / Echo / OUT / Gnd)
And, also I tried connecting, but following the SRF005 pin order (Out and Mode not connected):
Sensor = (Vcc / Trigger / Echo / OUT / Gnd)
To
Board = (Vcc / Echo / Trigger / MODE / Gnd)
My testing code is this:
'symbol trig = 3 ; Define output pin for Trigger pulse (A, M, X, X1 parts)
'symbol echo = 6 ; Define input pin for Echo pulse (A, M, X, X1 parts)
symbol trig = b.3 ; Define output pin for Trigger pulse (M2, X2 parts)
symbol echo = b.6 ; Define input pin for Echo pulse (M2, X2 parts)
symbol range = w1 ; 16 bit word variable for range
main:
pulsout trig,2 ; produce 20uS trigger pulse (must be minimum of 10uS)
pulsin echo,1,range ; measures the range in 10uS steps
pause 20 ; recharge period after ranging completes
let range = range * 5 / 58
if range>20 then '**My Own Test**
sound S.12, (50, 20) 'One kind of sound, if something is far.
elseif range<10 then
sound S.12, (112, 1) 'Another kind of sound, if something is close.
endif
goto main 'And around forever
I'll be honest, I don't know how to use the debug window in Axepad or Programming Editor.
So, What can I do? I just want the sensor work correctly.
Thks.
Jorge.
May I first say an excellent
Re: May I first say an excellent
Thks a lot.
Finally my bot it's working!
Just do I have to check out the code, understand it and go ahead.
Thks again JAX.
Debug
I would use the debug window to see what value is actually in W1. I have a feeling there is some math being done funny here.
Yes. Debug window --what are your actual numbers contained in W1 (and do they change the way you think they should with distance)?
Re: Debug
Hi.
Add a pic with debug windows as you wish.
But it doesn't show anything (I can be wrong).
I repeat... I don't know about debug window in Axepad, I just know that show values of the all variables, etc, etc.
I thought if placed some object close to sensor, the values of the variables could change on debug window.
But didn't change, this is right?
I still think the "issue" could be the pins on Axe408 (Instant robot shield) vs HY-SRF05 pins.
Are they (wires) well connected?
How to connect SRF05 to picaxe 28 pin project board (by Fritsl) //
Re: I use this code for HC-SR04 on a 08m2
Hi ChuckCrunch.
Modifying your code, I tried with:
main:
pulsout 1,1
pulsin 3,1,w1
let w1= w1 * 34 /2 /10
if w1>20 then 'Added line
sound S.12, (50, 20) 'Added line
elseif w1<10 then 'Added line
sound S.12, (112, 1) 'Added line
endif 'Added line
debug w1
pause 20
goto main
But, still no hear other sound, just one kind of sound.
Add this link:
Thks.
i use this code for HC-SR04 on a 08m2
pulsout 1,1
pulsin 3,1,w1
let w1= w1 * 34 /2 /10
debug w1
pause 20
goto main | http://letsmakerobots.com/node/35892 | CC-MAIN-2015-11 | refinedweb | 724 | 78.89 |
Create Your Own bit.ly Using Base58
Join the DZone community and get the full member experience.Join For Free
The implementation is quite straightforward: store the underlying URL in a database and return your primary key. This primary key when displayed as a number (Base10) is longer than strictly necessary; since each character can hold more than numbers, you are wasting space by constraining yourself to a decimal [0-9] range.
Enter Base58
Base58 is what you get after taking Base62 [a-zA-Z0-9] and removing any character that may induce to error when introduced by hand: 0 (zero), O (uppercase 'o'), I (uppercase 'i'), and l (lowercase 'L'). This concept was introduced to the general public by Flickr, which uses the following String:
123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ
To me, it makes more sense to use the natural order in the ASCII chart:
123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz
I will post here an example of the latest. For a Flickr implementation you can go here.
public class StringUtils {
private static final char[] BASE58_CHARS =
"123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz".toCharArray();
public static String numberToAlpha(long number) {
char[] buffer = new char[20];
int index = 0;
do {
buffer[index++] = BASE58_CHARS[(int) (number % BASE58_CHARS.length)];
number = number / BASE58_CHARS.length;
} while (number > 0);
return new String(buffer, 0, index);
}
public static long alphaToNumber(String text) {
char[] chars = text.toCharArray();
long result = 0;
long multiplier = 1;
for (int index = 0; index < chars.length; index++) {
char c = chars[index];
int digit;
if (c >= '1' && c <= '9') {
digit = c - '1';
} else if (c >= 'A' && c < 'I') {
digit = (c - 'A') + 9;
} else if (c > 'I' && c < 'O') {
digit = (c - 'J') + 17;
} else if (c > 'O' && c <= 'Z') {
digit = (c - 'P') + 22;
} else if (c >= 'a' && c < 'l') {
digit = (c - 'a') + 33;
} else if (c > 'l' && c <= 'z') {
digit = (c - 'l') + 43;
} else {
throw new IllegalArgumentException("Illegal character found: '" + c + "'");
}
result += digit * multiplier;
multiplier = multiplier * BASE58_CHARS.length;
}
return result;
}
}
An example of the expected output size:
44 = m
1431117682956369 = abc123ABC
// Long.MAX_VALUE
9223372036854775807 = CFq8pKn6mQN
This is hardly rocket science. You can find libraries to do this for ruby, javascript, PHP or even perl.
It's Base58 everywhere
Once you start doing this, it's nothing short of addictive. You can configure your web framework to use a Base58 converter for the key attributes in your URLs and start using '/shows/cr5W' instead of '/shows/234324323423'.
Everybody is doing this right now: Flickr, Facebook or YouTube (which seems to be using [0-9a-zA-Z_-]).
News - News - News
These days life is getting interesting by the minute. Last week our SimpleDS pet project got referenced by Google AppEngine Blog, and next April we are bringing the Javaspecialist Master Course to Madrid!
It's going to be awesome. This is the most advanced Java course I can refer to, and after some conversations with Dr. Kabutz he agreed to bring it to Madrid. It consists of four days of intense performance tuning, concurrency debugging, introspection, memory profiling and some neat, challenging Java puzzles. If you feel interested, you should consider to join us in April!
From
Opinions expressed by DZone contributors are their own. | https://dzone.com/articles/create-your-own-bitly-using | CC-MAIN-2020-45 | refinedweb | 513 | 61.77 |
About
TEN: B-movie psychological thriller full of twists!!!
$12,001
258
I've spent most of my creative life writing, performing, and recording music (), but have always dreamed about filmmaking. I've been obsessed with low-budget movies since I was a young lad and have always dreamed of using the B-movie aesthetic to make a film that is approached completely seriously. Over the past year, I've had an opportunity to make several short films and music videos and am now eager to make my first feature to tell a story with the depth and complexity I've always hoped to be able to attempt.
Recently, the historic Brattle Theatre in Harvard Square (Cambridge, MA) held a trailer-making competition. We worked to develop the above two-minute trailer for a non-existent film TEN. It was a tremendously fun opportunity to work with a really talented cast and crew of friends and make something in a short time (on almost no budget) that we were very proud of. We were extremely honored to also be selected for Brattle Creative Director Ned Hinkle's "Curator's Choice" award.
Now, we're looking to make this film a reality.
Some more info about making the trailer:
While the trailer is a little bit unstructured (in terms of revealing plot), we did outline the full plot while working on it, and it quickly became apparent that we had the workings of an interesting feature film. We're ready to move forward to develop the script over the next several months and shoot near the end of 2012. Some of the cast and crew involved in the making of the trailer will return (some already confirmed, to be announced during this campaign). We also have strong interest from some really talented camera and crew folks. I'll announce everyone involved here as we progress through this campaign and they officially sign on to production.
Note: The trailer was shot on a Panasonic HDC-HS900 High Definition Camcorder. The film will be shot on DSLRs (something along the lines of 5D/T3i/T4i).
As for budget, here is roughly what we're looking at for absolute minimum production cost. This campaign goal is set to that minimum. If we do not raise at least $11,000, this film WILL NOT get made. Your contribution is what can make this a reality. Let me emphasize: without your contribution, there will be no film.
Absolute minimum budget: Cast - 10 roles - $4000
Crew - DP, Sound, PAs, Makeup, etc. - $3000
Location/lodging - $2000
Food - $1000
Props - $1000
Total: $11,000
We have talent and crew that we can work with within this budget, but it is below what will allow us to pay everyone "fairly." We realistically need to raise closer to $20,000 to pay everyone appropriately, to cover rewards, to cover Kickstarter fees, and to position ourselves well for post-production costs. The more we raise, the more we can involve professionals in post-work like editing, effects, and color correction (taking it out of my limited-experience hands and making for a better final product).
Production Manager Sophia Cacciola and I are used to working on music projects on a tiered financial model. I.e., the more money we have budgeted for a project, the more it can be realized in an ideal way, but we can also work with a minimum pool. Sophia and I won't personally take any pay for this project. All funds raised will go toward film costs only: production (the minimum goal listed), post-production, promotion, etc.
About our film trailer (and why we hope to make a feature): Ten women are stranded and killed off by a mysterious murderer, The Butcher. They soon realize that the killer may actually be someone among them. The story (set in the 1970s), explores our creepy psychological association with the disturbing content of children's nursery rhymes, particularly focused on those involving pigs. There are a lot of complex ideas associated with the imagery that are to be explored in the feature film that couldn't be thoroughly examined in the 2-minute trailer, including: the irrational, unusual behavior resulting from survivalist paranoia, ideas associated with both pigs (animals, greedy, filthy, overeating, chauvinism) and women as pigs (meat market, etc.). In short, most of the important ideas remain as pure subtext in the short trailer form and I'm very eager to get a chance to tell this meaningful and important story.
Note: Kickstarter doesn't allow backers to make multiple pledges (although you can always upgrade your pledge to another level, even after making it). If you want to work something out to combine multiple rewards, please send me a message. Also, please send along any questions!
As much of our notoriety lies in the realm of music, we are offering a lot of rewards taking advantage of our music expertise. We are also offering reward levels that allow for ownership of unique instruments that we've used heavily on recordings and/or for live shows.
Thank you so much for taking the time to consider helping out with our film! We hope you decide to be a part of making it a reality.
Swine and Roses,
Michael J. Epstein
MJE@MichaelJEpstein.com
Questions about this project? Check out the FAQ
Support
Funding period
- (30 days) | https://www.kickstarter.com/projects/michaeljepstein/ten-b-movie-psychological-thriller-full-of-twists | CC-MAIN-2018-47 | refinedweb | 898 | 60.14 |
Ted Ts'o <tytso@mit.edu> writes:> On Mon, Oct 10, 2011 at 07:05:30PM -0700, Matt Helsley wrote:>>.>> If things are not working with containers, I would submit to you that> we're doing something wrong(tm). That is what this discussion is about. What we are doing wrong(tm).Mostly it is about the bits that have not yet been namespacified butneed to be.I am totally in favor of not starting the entire world. But justlike I find it convienient to loopback mount an iso image to seewhat is on a disk image. It would be handy to be able to justdownload a distro image and play with it, without doing anythingspecial.We can pair things down farther for the people who are running 1000copies of apache but not requiring detailed distro surgery beforestarting up the binaries on a livecd sounds handy.> Things should just work, except that> processes in one container can't use more than their fair share (as> dictated by policy) of memory, CPU, networking, and I/O bandwidth.You have to be careful with the limiters. The fundamental reasonwhy containers are more efficient than hardware virtualization isthat with containers we can do over commit of resources, especiallymemory. I keep seeing implementations of resource limiters that wantto do things in a heavy handed way that break resource over commit.> Something which is baked in my world view of containers (which I> suspect is not shared by other people who are interested in using> containers) is that given that kernel is shared, trying to use> containers to provide better security isolation between mutually> suspicious users is hopeless. That is, it's pretty much impossible to> prevent a user from finding one or more zero day local privilege> escalation bugs that will allow a user to break root. And at that> point, they will be able to penetrate the kernel, and from there,> break security of other processes.You don't even have to get to security problems to have that concern.There are enough crazy timing and side channel attacks.I don't know what concern you have security wise, but the problem thatwants to be solved with user namespaces is something you hit muchearlier than when you worry about sharing a kernel between mutuallydistrusting users. Right now root inside a container is root routoutside of a container just like in a chroot jail. Where this becomes aproblem is that people change things like like/proc/sys/kernel/print-fatal-signals expecting it to be a setting localto their sand box when in fact the global setting and things startbehaving weirdly for other users. Running sysctl -a during bootup has that problem in spades.With user namespaces what we get is that the global root user is not thecontainer root user and we have been working our way through thepermission checks in the kernel to ensure we get them right in thecontext of the user namespace. This trivially means that the thingsthat we allow the global root user to do in /proc/ and /sysfs andthe like simply won't be allowed as a container root user. Whichmakes doing something stupid and affecting other people much moredifficult.What the user namespace also allows is an escape hatch from thebonds of suid. Right now anything that could confuse an existingapp with that is suid root we have to only allow to root, or riskadding a security hole. With the user namespaces we can relaxthat check and allow it also for container root users as wellas global root users. When we are brave enough and certainenough of our code we can allow non-root users to create theirown user namespaces.There is the third use for containers where for some reasonwe have uid assignment overlap. Perhaps one distroy assignsuid 22 to sshd and another to the nobody user. Or perhaps thereare two departments who have that have done the silly thingof assigning overlapping uids to their users and we want toaccesses filesystems created by both departments at the sametime without a chance of confusion and conflict.With my sysadmin hat on I would not want to touch two untrusting groupsof users on the same machine. Because of the probability there is atleast one security hole that can be found and exploited to allowprivilege escalation.With my kernel developer hat on I can't just say surrender to theidea that there will in fact be a privilege escalation bug thatis easy to exploit. The code has to be built and designed so thatprivilege escalation is difficult. Otherwise we might as wellassume if you visit a website an stealthy worm has taken over yourcomputer.It is my hope at the end of the day that the user namespaces will be onemore line of defense in messing up and slowing down the evil omnicientworms that seem to uneering go for every privilege exploit there is.Eric | https://lkml.org/lkml/2011/10/11/26 | CC-MAIN-2020-34 | refinedweb | 816 | 59.64 |
A mail order house sells five products whose retail prices are as follows: Product 1 $2.98; product 2, 4.50; product 3, 9.98; product 4, 4.49; product 5, 6.87. Write an application that reads a series of pairs of numbers as follows:
a) product number
Your program should use a swich statement to determine the retail price for each product. It should calculate and display the total retail value of all products sold. Use a sentinel-controlled loop to determine when the program should stop looping and display the final results.
Right now I know I have a lot of work left to do on my code, but I am stuck at a part that hopefully someone can bring a little light on. I cannot for the life of me figure out how to get the cases to be read within the switch statement with the given values. After I prompt the user to enter in the product number, I dont know what to get and if I have enough variables declared above. Again I know that there is still a lot to do afterwards, and I am not asking for assistance on that right now because I am stuck at this particular point and cannot get the basic portion of this application to run properly. Any assistance would be appreciated! Below is my code as is right now.
import java.util.Scanner; public class TotalRetailValue { public static void main(String[] args) { Scanner input = new Scanner (System.in); int product = 0; double product1; double product2; double product3; double product4; double product5; int quantity; String done = "y"; double totalSales = 0; while (done.equals("y")) { System.out.println("Enter product number: "); System.out.println("Enter how many were sold: "); quantity = input.nextInt(); switch (product) { case 1: product1 = 2.98; break; case 2: product2 = 4.50; break; case 3: product3 = 9.98; break; case 4: product4 = 4.49; break; case 5: product5 = 6.87; break; } totalSales = product * quantity; System.out.println("Would you like to enter another sale? (y/n): "); done = input.next(); } } }
*edit: Please use code tags in the future, thanks!
This post has been edited by Martyr2: 28 May 2009 - 08:36 PM | http://www.dreamincode.net/forums/topic/107534-in-need-of-some-help-please/ | CC-MAIN-2017-34 | refinedweb | 366 | 67.76 |
Revision history for Dist-Zilla-Plugin-Test-Kwalitee 2.12 2015-09-30 03:59:46Z - use TODO around tests that fail on perl 5.8.x due to the buggy handling of qr/...$/m - fix licencing metadata 2.11 2014-08-27 01:40:14Z - fix test failures with new metrics added in MCA 0.93_01 2.10 2014-08-23 17:55:26Z - fix pod error (thanks haarg!) - generated test filename is now configurable 2.09 2014-08-23 08:40:01Z - sort the arguments to kwalitee_ok, for smaller diffs between iterations - now again running the generated test during tests, but without attempting to capture its output cleverly 2.08 2014-08-16 04:56:06Z - line numbers in shipped code are now almost the same (within 3) as the repository source, for easier debugging - use kwalitee_ok() interface newly added in Test::Kwalitee 1.21 2.07 2013-10-15 02:18:02Z - include in the generated test the exact version of the plugin that generated the test - warnings tests bypassed during installation - update minimum required version of Test::Kwalitee 2.06 2013-08-17 02:41:24Z - removed old and deprecated Dist::Zilla::Plugin::KwaliteeTests, which is no longer indexed by PAUSE anyway - fixed tests broken on win32 - Test::Kwalitee is now required to be present when the test is run (by authors, at release time) - cleaned up prerequisite list 2.05 2013-08-11 21:18:58Z - adjust tests to handle recent changes to Test::Kwalitee and Module::CPANTS::Analyse 2.04 2013-07-26 00:29:10Z - fix installation failures with Test::Kwalitee 1.09 (issue #4, harleypig's repo) 2.03 2011-10-19 14:56:47Z 2.020000 2011-09-08 02:47:05Z - Provide a deprecation warning (Mike Doherty) - Moved switch_namespace branch to master ( HarleyPig ) - brought dist.ini up to date ( HarleyPig ) 1.112410 2011-08-29 15:57:31Z - Made pod coverage test pass ( HarleyPig ) - Fixed error with tests needing 'plan' defined ( Kent Fredric) - Replace 2-phase inject/munge with 1-phase inject ( Kent Fredric ) - Add some tests for our test being run ( Kent Fredric ) 1.112400 2011-08-28 15:34:37Z 1.112390 2011-08-27 03:11:01Z 1.101420 2010-05-22 15:47:26Z - removed weaver.ini since that's handled in Dist::Zilla's [@MARCEL] now - list Test::Kwalitee in dist.ini so we don't use() it anymore 1.100690 2010-03-10 22:43:35Z - original version | https://web-stage.metacpan.org/dist/Dist-Zilla-Plugin-Test-Kwalitee/changes | CC-MAIN-2021-31 | refinedweb | 414 | 67.15 |
Use OAuth 2.0 to Secure Your ASP.NET Core App
Use OAuth 2.0 to Secure Your ASP.NET Core App
Secure your ASP.NET application with OAuth.
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Imagine having an app where you can write and store your notes efficiently. Today, we are going to build an app that will keep track of your notes. We’ll use ASP.NET Core to build the app. We’ll also use .NET Core’s OAuth 2.0 authentication middleware to make sure the personal notes are kept secure.
My Private Notes App
As mentioned earlier, you'll use an ASP.NET app to build your note-keeping app. Here's how the app works: The home page will keep track of all your recent notes, and if you include more than three notes, the oldest will be shelved. Once we've built the app, you'll learn how to secure it with OAuth. Read this starter project from GitHub to get started.
You may also like: API Security: Ways to Authenticate and Authorize.
Run the project to make sure it starts. You should see a "Hello, World" message displayed and some other basic app scaffolding.
Start by replacing the contents of
Controllers\HomeController.cs with the code below.
using System.Collections.Generic; using Microsoft.AspNetCore.Authorization; using Microsoft.AspNetCore.Mvc; namespace OAuthNotes.Controllers { public class HomeController : Controller { private static List<string> _notes; public HomeController() { if (_notes == null) { _notes = new List<string> {"", "", ""}; } } public IActionResult Index() { return View(_notes); } [HttpPost] public IActionResult Add(string note) { _notes.Add(note); if (_notes.Count > 3) { _notes.RemoveAt(0); } return RedirectToAction("Index"); } } }
As you can see, notes are kept in a static list, which is initialized the first time the controller is loaded. Then, there are methods to show the list and add items to it.
Next, you need to replace the contents of
Views\Home\Index.cshtml with this code:
@model List<string> @{ ViewData["Title"] = "My Notes"; } <h1>My Notes</h1> <ul> @foreach (var note in Model) { <li>@note</li> } </ul> <form asp- <input type="text" name="note" /> <input type="submit" value="Add Note" /> </form>
Now, the home page should allow you to add up to three notes. That was easy, wasn’t it? But what if you don’t want curious eyes looking at your notes? How can you keep your notes private? Let’s use OAuth 2.0 to secure access to the app.
Set up ASP.NET OAuth 2.0 Authentication Middleware
OAuth 2.0 is a popular security protocol used by many organizations to protect sensitive systems and information. Many websites use OAuth to allow users to sign into their applications and other people’s applications.
ASP.NET Core comes with OAuth authentication middleware, which makes it easy to use a third-party OAuth 2.0 server for login. Many social networks and websites provide an OAuth 2.0 service for public use, so regardless of whether you want to log in with Facebook, BitBucket, Stack Overflow, or Trello, it’s just a matter of setting them up as the Identity Provider.
For this tutorial, you will use Okta's OAuth service to protect your app. The ASP.NET OAuth Middleware will be connected to Okta and use Okta as the Identity Provider. One neat feature of Okta’s service is that it can federate many different authentication services and provide your app just one point of integration for them all.
First, you’ll need to open up
Startup.cs and add this line right above
app.UseMvc in the
Configure method:
app.UseAuthentication();
Then, add this at the top of the
ConfigureServices method:
services.AddAuthentication(options => { // If an authentication cookie is present, use it to get authentication information options.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme; options.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme; // If authentication is required, and no cookie is present, use Okta (configured below) to sign in options.DefaultChallengeScheme = "Okta"; }) .AddCookie() // cookie authentication middleware first .AddOAuth("Okta", options => { // Oauth authentication middleware is second var oktaDomain = Configuration.GetValue<string>("Okta:OktaDomain"); // When a user needs to sign in, they will be redirected to the authorize endpoint options.AuthorizationEndpoint = $"{oktaDomain}/oauth2/default/v1/authorize"; // Okta's OAuth server is OpenID compliant, so request the standard openid // scopes when redirecting to the authorization endpoint options.Scope.Add("openid"); options.Scope.Add("profile"); options.Scope.Add("email"); // After the user signs in, an authorization code will be sent to a callback // in this app. The OAuth middleware will intercept it options.CallbackPath = new PathString("/authorization-code/callback"); // The OAuth middleware will send the ClientId, ClientSecret, and the // authorization code to the token endpoint, and get an access token in return options.ClientId = Configuration.GetValue<string>("Okta:ClientId"); options.ClientSecret = Configuration.GetValue<string>("Okta:ClientSecret"); options.TokenEndpoint = $"{oktaDomain}/oauth2/default/v1/token"; // Below we call the userinfo endpoint to get information about the user options.UserInformationEndpoint = $"{oktaDomain}/oauth2/default/v1/userinfo"; // Describe how to map the user info we receive to user claims options.ClaimActions.MapJsonKey(ClaimTypes.NameIdentifier, "sub"); options.ClaimActions.MapJsonKey(ClaimTypes.Name, "given_name"); options.ClaimActions.MapJsonKey(ClaimTypes.Email, "email"); options.Events = new OAuthEvents { OnCreatingTicket = async context => { // Get user info from the userinfo endpoint and use it to populate user claims var request = new HttpRequestMessage(HttpMethod.Get, context.Options.UserInformationEndpoint); request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", context.AccessToken); var response = await context.Backchannel.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, context.HttpContext.RequestAborted); response.EnsureSuccessStatusCode(); var user = JObject.Parse(await response.Content.ReadAsStringAsync()); context.RunClaimActions(user); } }; });
I added a lot of comments in the code you just pasted in to help you understand what the middleware is doing, but I’ll also describe it step-by-step here.
Enforce OAuth Authorization Code Flow
If an unauthenticated user tries to access a URL that requires authorization, the authentication middleware will be triggered. In this case, it will use the Okta OAuth service, since the
DefaultChallengeScheme is set to
"Okta".
The OAuth middleware will kick off the OAuth 2.0 authorization code flow, which works like this:
- Your app redirects the user to the
AuthorizationEndpointwhere they can authenticate (sign in with a username and password) and authorize the app to get access to the requested resources. In this case, we request access to some identity information, including the user’s name and email address, via some predefined scopes.
- The authorization server redirects the user back to your app’s
CallbackPathwith an authorization code in the URL. The middleware intercepts this request and gets the authorization code.
- Your app sends the authorization code, the
ClientId, and
ClientSecretto the
TokenEndpoint.
- The authorization server returns an access token.
- Your app sends the access token to the
UserInformationEndpoint.
- The authorization server returns the identity information that was requested.
Once the flow is complete, the middleware in your app maps the identity information it received to claims and creates a secure cookie to save the authenticated user’s information. On subsequent requests, the user identity is populated from the cookie, saving all of the back-and-forth communication between your app and the authentication server.
Now, you just need to add an
[Authorize] attribute right above the
HomeController class in
Controllers\HomeController.cs so that only authenticated users can access the app.
Configure the Authorization Server in Okta
Although you have set up the app to authenticate with Okta, Okta won’t recognize your app until you register it.
Sign in to
ListAppfor the Name.
- Change the Base URIs to the exact URL that your application runs on locally, including the trailing backslash. This should be something like(change the port number to match your port number and make sure it is https).
- Change the first of the Login redirect URIs to have the same scheme, host, and port number as above. It should still end with
authorization-code/callback
- Click Done.
On the next screen, you will see an overview of settings. Below, the General Settings section, you’ll see the Client Credentials section. Note the Client ID and the Client Secret on the next page and add them to your
appsettings.json file, like this:
"Okta": { "ClientId": "{yourOktaClientId}", "ClientSecret": "{yourOktaClientSecret}", "OktaDomain": "https://{yourOktaDomain}" }
Your Okta Domain is the Org URL displayed in the top left corner of the main Okta Dashboard page.
(Note that in order to keep these secrets out of source control you should move the
ClientId and
ClientSecretsettings to your User Secrets file before you commit. You can skip this step for now since this is just a tutorial.)
Now, you should be all set. When you run your app, Okta should prompt you to sign in. After signing in, you will be able to access your private notes.
If you want to keep your notes truly private, you will need to adjust the
HomeController to maintain separate lists for each authenticated user. For example, you could create a dictionary of user lists, using the unique identifier in
User.Claims.First(c => c.Type == ClaimTypes.NameIdentifier).Value as a dictionary key. I’ll leave that coding to you.
Limitations of OAuth 2.0
Although the OAuth protocol can be used for user authentication, it wasn’t actually designed for it. The OAuth protocol was designed for delegated access. The access tokens that are issued by OAuth servers are like hotel key cards. They grant access to certain rooms, but they often don’t have any identifying information attached. Of course, the staff at the front desk of a hotel will probably require you to present identification before they hand out a key card, but each hotel’s process could be a bit different.
As people began to use OAuth for authentication, there were a variety of different ways that the authentication process was handled. For example, there is no standard way to do a logout process with OAuth. The app you just created clears a local cookie when you click on Sign out, but you are still signed in at the Okta server, so if you click Sign in again you will be automatically signed in again without being prompted for a password! (If you want, you can close your browser to clear Okta’s cookie.)
To overcome the confusion of using OAuth for authentication without having a shared standard for how to use it, the OpenID Connect standard was built on top of OAuth. If you’re interacting with an OAuth authorization server that also supports OpenID Connect (like Okta), using the .NET Core OpenID Connect middleware (or Okta’s even simpler OpenID Connect middleware) will save you a lot of effort. See the links below for more information on how to use OpenID Connect for authentication in your app.
Learn More About OAuth 2.0 and ASP.NET
Interested in learning more about ASP.NET Core, Oauth 2.0, OpenID Connect, or building secure applications with Okta? Check out our Product Documentation or any of these great resources:
- What is OAuth?
- OAuth 2.0 and OpenID Connect.
- OpenID Connect for User Authentication in ASP.NET Core.
- Create Login and Registration in Your ASP.NET Core MVC App.
- Add Login to Your ASP.NET Core MVC App.
As always, if you have comments or questions about this post, feel free to leave them in the comments below.
Further Reading }} | https://dzone.com/articles/use-oauth-20-to-secure-your-aspnet-core-app | CC-MAIN-2019-51 | refinedweb | 1,887 | 50.43 |
Problem Statement
Contest Source
Author, Tester and Editorialist : Rohail Alam
DIFFICULTY:
Easy-Medium
PREREQUISITES:
Fluency with observation-based problems
PROBLEM:
Given a string, you need to find out whether the characters can be arranged to obtain the lexicographically smallest form of the same with the help of swap operations bound by conditions mentioned in the problem statement.
QUICK EXPLANATION
Hint
Try to find out whether you can swap any two letters with the help of a vowel and a consonant.
EXPLANATION
This problem has a purely observation based solution. The answer will always be “YES” if there is at least one vowel and one consonant each in the given string. If not, the answer will still be “YES” if the string is already in the lexicographically smallest order, else the answer is “NO”.
To make the initial statement more clear, we can consider an example string “bayd”
The string we want to obtain after the swapping operations is “abdy”
First, we swap ‘a’ (vowel) with ‘b’ (consonant) to get “abyd”
Now we need to just swap ‘y’ and ‘d’ to get the desired string, but both of them are consonants so this is not possible to do directly. But observe that the presence of vowel ‘a’ aids in making this possible as such:
- Swap ‘a’ and ‘y’ to get “ybad”
- Move ‘d’ to the desired position by swapping ‘a’ and ‘d’ : “ybda”
- Move ‘a’ back to its original position by swapping ‘a’ and ‘y’ : “abdy”
Notice that through these steps we were able to swap two consonants with the help of a vowel.
From this observation, we can make out that the presence of at least 1 vowel and 1 consonant(to swap the vowel with) is a necessary and sufficient condition to obtain the desired string.
If the above condition is broken, then the answer is always “NO” as no swapping operation can be carried out, unless of course if the string is already in the lexicographically smallest order. In that case, the answer will be “YES”
SOLUTION
Click Me
#include<bits/stdc++.h> using namespace std; int main(){ int t; cin>>t; while(t--){ int n; cin>>n; string s; cin>>s; string cpy = s; sort(cpy.begin(),cpy.end()); // cpy is the lexicographically smallest form of s set<char> vowels{'a','e','i','o','u'}; int vow=0,conso=0; int size = (int)s.size(); for(int i=0;i<size;++i){ if(vowels.find(s[i]) == vowels.end()) conso++; // Counting the number of vowels and consonants in the given string else vow++; } if(vow>=1 && conso>=1){ cout<<"YES\n"; // Condition described in the explanation is checked } else{ (s==cpy)? cout<<"YES\n" : cout<<"NO\n"; // If condition is not followed, checking if the given string is already in desired form } } } | https://discuss.codechef.com/t/benjvow-editorial/95967 | CC-MAIN-2021-49 | refinedweb | 465 | 51.52 |
I am using the method described in this answer to dynamically update a bar graph. The bar graph I want however should show values coming from the zero-point rather than the bottom of the graph. This is my bar initialisation code:
oxBar = aBar.bar(0, 200, bottom=-100, width=1)
Matplotlib as default autosizes plot but you can set
ylim to have constant size/height and then
0 can be always in middle.
Example
import matplotlib.pyplot as plt import matplotlib.animation as animation import random def animate(frameno): x = random.randint(-200, 200) n = [x, -x] for rect, h in zip(rects, n): rect.set_height(h) return rects # --- init --- fig, ax = plt.subplots() rects = plt.bar([0,1], [0,0], width=1) plt.ylim([-200, 200]) ani = animation.FuncAnimation(fig, animate, blit=True, interval=100, frames=100, repeat=False) plt.show() | https://codedump.io/share/i8Y0cs1nhMMR/1/matplotlib---updating-bar-graph-with-positive-and-negative-values | CC-MAIN-2017-09 | refinedweb | 143 | 62.54 |
This is the technical documentation for older versions of Odoo (formerly OpenERP).
See the new Odoo user documentation.
See the new Odoo technical documentation.
QWeb¶
QWeb is the template engine used by the OpenERP Web Client. It is an XML-based templating language, similar to Genshi, Thymeleaf or Facelets with a few peculiarities:
It's implemented fully in javascript and rendered in the browser.
Each template file (XML files) contains multiple templates, where template engine usually have a 1:1 mapping between template files and templates.
It has special support in OpenERP Web's Widget, though it can be used outside of OpenERP Web (and it's possible to use Widget without relying on the QWeb integration)..
Here's an example demonstrating most of the basic QWeb features:
<templates> <div t- <h4 t-<t t-</h4> <ul> <li t- <t t- <t t- </t> </li> </ul> </div> <t t- <t t- <dl> <t t- <dt><t t-</dt> <dd><t t-</dd> </t> </dl> </t> </templates>
rendered with the following context:
{ "class1": "foo", "title": "Random Title", "items": [ { "name": "foo", "tags": {"bar": "baz", "qux": "quux"} }, { "name": "Lorem", "tags": { "ipsum": "dolor", "sit": "amet", "consectetur": "adipiscing", "elit": "Sed", "hendrerit": "ullamcorper", "ante": "id", "vestibulum": "Lorem", "ipsum": "dolor", "sit": "amet" } } ] }
will yield this section of HTML document (reformated for readability):
<div class="base foo"> <h4>Random Title</h4> <ul> <li class="even"> foo <dl> <dt>bar</dt> <dd>baz</dd> <dt>qux</dt> <dd>quux</dd> </dl> </li> <li class="odd"> Lorem <dl> <dt>ipsum</dt> <dd>dolor</dd> <dt>sit</dt> <dd>amet</dd> <dt>consectetur</dt> <dd>adipiscing</dd> <dt>elit</dt> <dd>Sed</dd> <dt>hendrerit</dt> <dd>ullamcorper</dd> </dl> </li> </ul> </div>
API¶
While QWeb implements a number of attributes and methods for customization and configuration, only two things are really important to the user:
- class QWeb2.Engine()¶
The QWeb "renderer", handles most of QWeb's logic (loading, parsing, compiling and rendering templates).
OpenERP Web instantiates one for the user, and sets it to instance.web.qweb. It also loads all the template files of the various modules into that QWeb instance.
A QWeb2.Engine() also serves as a "template namespace".
- QWeb2.Engine.render(template[, context])¶
Renders a previously loaded template to a String, using context (if provided) to find the variables accessed during template rendering (e.g. strings to display).
The engine exposes an other method which may be useful in some cases (e.g. if you need a separate template namespace with, in OpenERP Web, Kanban views get their own QWeb2.Engine() instance so their templates don't collide with more general "module" templates):
- QWeb2.Engine.add_template(templates)¶ or Node
QWeb will traverse the first level of the document (the child nodes of the provided root) and load any named template or template override.
A QWeb2.Engine() also exposes various attributes for behavior customization:
- QWeb2.Engine.prefix¶
Prefix used to recognize directives during parsing. A string. By default, t.
- QWeb2.Engine.debug¶
Boolean flag putting the engine in "debug mode". Normally, QWeb intercepts any error raised during template execution. In debug mode, it leaves all exceptions go through without intercepting them.
- QWeb2.Engine.jQuery¶
The jQuery instance used during template inheritance processing. Defaults to window.jQuery.
Directives¶
A basic QWeb template is nothing more than an XHTML document (as it must be valid XML), which will be output as-is. But the rendering can be customized with bits of logic called "directives". Directives are attributes elements prefixed by prefix (this document will use the default prefix t, as does OpenERP Web).
A directive will usually control or alter the output of the element it is set on. If no suitable element is available, the prefix itself can be used as a "no-operation" element solely for supporting directives (or internal content, which will be rendered). This means:
<t>Something something</t>
will simply output the string "Something something" (the element itself will be skipped and "unwrapped"):
var e = new QWeb2.Engine(); e.add_template('<templates>\ <t t-<t>Test 1</t></t>\ <t t-<span>Test 2</span></t>\ </templates>'); e.render('test1'); // Test 1 e.render('test2'); // <span>Test 2</span>
Note
The conventions used in directive descriptions are the following:
directives are described as compound functions, potentially with optional sections. Each section of the function name is an attribute of the element bearing the directive.
a special parameter is BODY, which does not have a name and designates the content of the element.
special parameter types (aside from BODY which remains untyped) are Name, which designates a valid javascript variable name, Expression which designates a valid javascript expression, and Format which designates a Ruby-style format string (a literal string with #{Expression} inclusions executed and replaced by their result)
Note
Expression actually supports a few extensions on the javascript syntax: because some syntactic elements of javascript are not compatible with XML and must be escaped, text substitutions are performed from forms which don't need to be escaped. Thus the following "keyword operators" are available in an Expression: and (maps to &&), or (maps to ||), gt (maps to >), gte (maps to >=), lt (maps to <) and lte (maps to <=).
Defining Templates¶
- t-name=name
Templates can only be defined as the children of the document root. The document root's name is irrelevant (it's not checked) but is usually <templates> for simplicity.
<templates> <t t- <!-- template code --> </t> </templates>
t-name can be used on an element with an output as well:
<templates> <div t- <!-- template code --> </div> </templates>
which ensures the template has a single root (if a template has multiple roots and is then passed directly to jQuery, odd things occur).
Output¶
- t-esc=content
Evaluates, html-escapes and outputs content.
- t-raw=content
Similar to t-esc but does not html-escape the result of evaluating content. Should only ever be used for known-secure content, or will be an XSS attack vector.
- t-att=map
Evaluates map expecting an Object result, sets each key:value pair as an attribute (and its value) on the holder element:
<span t-
will yield
<span foo="3" bar="42"/>
- t-att-ATTNAME=value
Evaluates value and sets it on the attribute ATTNAME on the holder element.
If value's result is undefined, suppresses the creation of the attribute.
Flow Control¶
- t-set=name (t-value=value | BODY)
Creates a new binding in the template context. If value is specified, evaluates it and sets it to the specified name. Otherwise, processes BODY and uses that instead.
- t-if=condition
Evaluates condition, suppresses the output of the holder element and its content of the result is falsy.
- t-foreach=iterable [t-as=name]
Evaluates iterable, iterates on it and evaluates the holder element and its body once per iteration round.
If name is not specified, computes a name based on iterable (by replacing non-Name characters by _).
If iterable yields a Number, treats it as a range from 0 to that number (excluded).
While iterating, t-foreach adds a number of variables in the context:
- #{name}
If iterating on an array (or a range), the current value in the iteration. If iterating on an object, the current key.
- #{name}_all
The collection being iterated (the array generated for a Number)
- #{name}_value
The current iteration value (current item for an array, value for the current item for an object)
- #{name}_index
The 0-based index of the current iteration round.
- #{name}_first
Whether the current iteration round is the first one.
- #{name}_parity
"odd" if the current iteration round is odd, "even" otherwise. 0 is considered even.
- t-call=template [BODY]
Calls the specified template and returns its result. If BODY is specified, it is evaluated before calling template and can be used to specify e.g. parameters. This usage is similar to call-template with with-param in XSLT.
Template Inheritance and Extension¶
- t-extend=template BODY
Works similarly to OpenERP models: if used on its own, will alter the specified template in-place; if used in conjunction with t-name will create a new template using the old one as a base.
BODY should be a sequence of t-jquery alteration directives.
- t-jquery=selector [t-operation=operation] BODY
If operation is specified, applies the selector to the parent template to find a context node, then applies operation (as a jQuery operation) to the context node, passing BODY as parameter.
Note
replace maps to jQuery's replaceWith(newContent), inner maps to html(htmlString).
If operation is not provided, BODY is evaluated as javascript code, with the context node as this.
Warning
While this second form is much more powerful than the first, it is also much harder to read and maintain and should be avoided. It is usually possible to either avoid it or replace it with a sequence of t-jquery:t-operation:.
Escape Hatches / debugging¶
- t-log=expression
Evaluates the provided expression (in the current template context) and logs its result via console.log.
- t-debug
Injects a debugger breakpoint (via the debugger; statement) in the compiled template output.
- t-js=context BODY
Injects the provided BODY javascript code into the compiled template, passing it the current template context using the name specified by context. | https://doc.odoo.com/trunk/web/qweb | CC-MAIN-2020-16 | refinedweb | 1,540 | 52.8 |
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Start a Thread | Settings
Hello everybody,
I have a problem with a global variable. This variable is declared as
extern.
It is reset to 0 automatically inside the Keil µVisionb 4
debugger when used in a function written in different C file.
I make deeper reference.
I declared variable in a header like this
#ifdef __VAR_G
#define __DEF
#else
#define __DEF extern
#endif
__DEF uint32_t SystemCoreClock;
__DEF uint32_t Init_OK;
I use this variable twice :
Firstly in a.c file
#define __VAR_G
#include "stm32f4xxiut.h"
void SystemInit()
{
Init_OK = Init_OK | HSE_FAIL;
SystemCoreClock=16000000;
}
Secondly in b.c file
#include "stm32f4xxiut.h"
void main()
{
int b=0;
if (Init_OK==1)
b=2;
}
My problem is the following.
In the keil debugger, with STM32F4XX, first, system init is executed.
The both variable are declared as global and a value is assigned to
them. Then, the core branch to main and the both variable are reset
to zero in spite of the extern keyword used inside the
definition.
Do you know why there is this strange behaviour.
Thank you.
Then, the core branch to main and the both variable are reset
to zero in spite of the extern keyword used inside the
definition
ALL variables, except those in noinit (I)RAM segments will be set to
zero on the entry of main.
I do not see what "the extern keyword" has to do with it
Erik
ALL variables, except those in noinit (I)RAM segments will be
set to zero on the entry of main.
I think you meant to say that all variables, except those in
noinit, will be initialised just prior to the entry of main (and not
necessarily set to zero).
Ok, it is a normal behaviour.
I don't know that the entry in main has this kind of effect.
Then, how can I do to avoid this problem and locate variable in
noinit (I)RAM segments ?
Thanks.
It's not so much the behaviour of main() that should have you
surprised. That's perfectly ordinary, well-defined behaviour of
every C program.
The thing you should wonder about is that System_Init() is called
before main(). That's not something a C program usually
allows. So this function SystemInit() must be rather special.
The question you should have asked yourself earlier is: what
limitations are documented in your system manual about what
you can and cannot do in this function? In particular, are you sure
you're supposed to use ordinary C variables in there, as opposed to,
say, only set up some special purpose registert to configure clocks,
enable peripherals, etc.?
I found a solution by making these variables in noinit zone with
zero_init option in declaration.
This avoid resetting selected variable at the entry inside main
function.
Thanks a lot for your help and this amount of knownledge you bring
to me.
This avoid resetting selected variable at the entry inside main
function.
this is not done "inside main function" it is done by the "secret
sauce initializer code" that the linker insert before
main()
Just note that the Cortex chips have a design where the processor
sets up the stack, allowing a C function to get activate directly on
reset with zero assembler instructions involved. And the core
performs the required background stuff to allow interrupt handlers to
be ordinary C functions - no interrupt keyword needed.
But if the reset code is written in C, that code must still be
written based on the knowledge that the processor hasn't been fully
configured yet and that C libraries etc can't be used.
The C standard doesn't really consider C functions called before
main() - it considers main() to be the entry function and specifies a
number of rules that must be fulfilled at entry to main().
I found a solution by making these variables in noinit zone
with zero_init option in declaration.
I contest your assessment of that being a "solution". It's
actually more of the same problematic behaviour piled upon what's
already there. But two wrongs don't make a right.
The real problem is that you're doing stuff in the wrong place.
SystemInit() is a special function that exists for a couple of very
specific purposes. Initializing ordinary C variables is not
one of those. You ignore such details at your own peril.
The solution is for you to stop fighting your tools and
just use them as they're meant to. Leave initialization of C
variables to the C compiler and linker or, if you really think you
have to do it manually, do it in main().
In other words, you created that problem yourself. All it woould
take to solve it is to stop creating it.
I constest your assesment.
System_Init() initializes clock.
These two variables are to save clock frequency and the second is a
kind of register to know what is working or not inside initialization
without checking every register.
It is not classical C variable for my program which them will be
declare and initialize inside main.
I found a solution by making these variables in noinit zone
with zero_init option in declaration.
This avoid resetting selected variable at the entry inside main
function.
This is absurd!
Here is reset handler of my LPC1788 bootloader:
Reset_Handler PROC
EXPORT Reset_Handler [WEAK]
IMPORT SystemInit
IMPORT __main
IF :DEF:MBOOT
IMPORT sdram_init
ENDIF
LDR R0, =SystemInit
BLX R0
IF :DEF:MBOOT
; init SDRAM before scatter loading starts...
LDR R0, =sdram_init
BLX R0
ENDIF
LDR R0, =__main
BX R0
ENDP
SystemInit call call _BEFORE_ scatter loading (__main...)!
There is no justification for making that variable non-zero init.
I suggest to you that you actually listen to us, instead of going
into a tail spin...
System_Init() initializes clock.
Exactly. And that's all you're supposed to do in there.
Writing normal C variables is stricly outside the set of things
you're allowed to do in there.
These two variables are to save clock frequency
And why on earth would you need a variable to store this
in, although it is beyond all reasonable doubt a compile-time
constant?
and the second is a kind of register to know what is working or
not inside initialization without checking every register.
Except that it's not any kind of register. It's a C variable.
It is not classical C variable for my program which them will
be declare and initialize inside main.
Now you're being ridiculous. Well, either that, or you have not
the slightest idea what the words you're using actually mean.
Because, in contrast to what you say now, that's exactly what
those things are: plain ordinary C variables. Your own code treats
them every bit as if it were one: you set the variable to some value
in one place, and expect it to keep that value until modified by an
assignment later.
The following is straight from ST's system_stm32f0xx.c (my
emphasis added) - I imagine that the OP's STM32F4xx would be
similar:
/**
******************************************************************************
* @file system_stm32f0xx.c
* @author MCD Application Team
* @version V1.0.0
* @date 23-March-2012
* @brief CMSIS Cortex-M0 Device Peripheral Access Layer System Source File.
* This file contains the system clock configuration for STM32F0xx devices,
* and is customized for use with STM32F0-DISCOVERY Kit.
* The STM32F0xx is configured to run at 48 MHz, following the three
* configuration below:
* - PLL_SOURCE_HSI (default): HSI (~8MHz) used to clock the PLL, and
* the PLL is used as system clock source.
* - PLL_SOURCE_HSE : HSE (8MHz) used to clock the PLL, and
* the PLL is used as system clock source.
* - PLL_SOURCE_HSE_BYPASS : HSE bypassed with an external clock
* (8MHz, coming from ST-Link) used to clock
* the PLL, and the PLL is used as system
* clock source.
*
*
* 1. This file provides two functions and one global variable to be called from
* user application:
* - SystemInit(): Setups the system clock (System clock source, PLL Multiplier
* and Divider factors, AHB/APBx prescalers and Flash settings),
* depending on the configuration selected (see above).
* This function is called at startup just after reset and
* before branch to main program. This call is made inside
* the "startup_stm32f0xx.s" file.
*
* - SystemCoreClock variable: Contains the core clock (HCLK), it can be used
* by the user application to setup the SysTick
* timer or configure other parameters.
*
* - SystemCoreClockUpdate(): Updates the variable SystemCoreClock and must
* be called whenever the core clock is changed
* during program execution.
So they do seem to be suggesting that the user code
can just read this global?!
This will work provided you call
SystemCoreClockUpdate() before the user code first uses
the SystemCoreClock variable - but the documentation above certainly
doesn't make that clear! | http://www.keil.com/forum/20737/ | CC-MAIN-2013-20 | refinedweb | 1,447 | 63.09 |
CS::NumberedFilenameHelper Class Reference
Helper to deal with numbered filename. More...
#include <cstool/numberedfilenamehelper.h>
Detailed Description
Helper to deal with numbered filename.
Takes a mask for a filename, which can contain digits, as input and returns filenames with subsequently increasing numbers. Also can automatically pick an unused filename.
Definition at line 34 of file numberedfilenamehelper.h.
Constructor & Destructor Documentation
Initialize helper.
See SetMask() for the meaning of
mask.
Definition at line 42 of file numberedfilenamehelper.h.
Member Function Documentation
Returns the next unused filename.
- Parameters:
-
Returns the filename with the next higher number.
Definition at line 63 of file numberedfilenamehelper.h.
Resets the counter to 0.
Definition at line 50 of file numberedfilenamehelper.h.
Set the mask for the filename.
The rightmost cluster of digits in the filename is replaced with the value of the counter. The format is chosen such that the digits are filled up with leading zeroes. If the filename does not contain any digits, the counter is inserted before the last dot or appended to the end of the name.
The documentation for this class was generated from the following file:
- cstool/numberedfilenamehelper.h
Generated for Crystal Space 1.4.1 by doxygen 1.7.1 | http://www.crystalspace3d.org/docs/online/api-1.4/classCS_1_1NumberedFilenameHelper.html | CC-MAIN-2014-52 | refinedweb | 201 | 53.47 |
This!
This week S. Somasegar , Senior Vice President Developer Division, announced on his blog that we've released
If i create a SQL CLR UDF and/or stored proc, can my .net clr code (the .net assembly tha is deployed to the sql server) use the TPL, so that portions of my .net SQL CLR code can run in parallel across multiple CPU cores?
I am still wondering what could be an advantage over CCR.
S. Somasegar , Senior Vice President Developer Division heeft deze week op zijn blog geannounceerd dat
June 2008 CTP - Parallel Extensions to the .NET FX
Havok, ya disponible gratuitamente : El motor de físicas más empleado en el mundo de los videojuegos
Hi Jose-
To do its job well and to maintain high reliability guarantees, SQL Server needs to have strict control over code that executes in its processes. Explicitly creating new threads and doing synchronization between threads in SQL/CLR code is something SQL Server tries to avoid, and thus most of the types in the System.Threading namespace, including the Task Parallel Library, are marked with HostProtectionAttributes that prohibit their use within SQL Server. This potentially can be worked around by loading the assemblies into SQL Server with the UNSAFE permission set, but doing so could open the system up to greater risk. Another interesting facet to the question is that, in many situations, an instance of SQL Server fields many requests simultaneously, and thus it already can provide a significant amount of concurrency, even without individual SQL/CLR procedures being parallelized. The main point here is that SQL Server already does a good job at parallelizing, so it's not clear how much additional value there is to gain by using Parallel Extensions in SQL/CLR code. All that said, we are investigating what kind of support we can reasonably provide for this scenario moving forward.
Best,
Stephen Toub
Hello Hans,.
Thanks.
[原文地址]： June 2008 CTP - Parallel Extensions to the .NET FX [原文发表时间]： Monday, June 02, 2008 2:18 PM 这周
what?,i don't know what you say.
Last week, Microsoft released a new Community Technology Preview (CTP) of the .NET Task Parallel Library...
at 06/02, Microsoft just released the latest CTP of Parallel Extension to .NET 3.5 (as PFX later), available
Randy Smith
4601 S Crysler
Independence, mo 64055
358-2638
Could Parallel Extensions be used in an unmanaged C++ application?
Albert,
You could use Parallel Extensions from a native application through interop (such as by using C++/CLI to create a wrapper for the native application to consume), but the results would likely be less than stellar. Managed/native interop is relatively expensive, and unless you were doing a serious amount of work in a task or in the body of a loop, you wouldn't want each invocation to have to make such a transition, as the overheads would likely be prohibitive. You can, however, use Parallel Extensions from a managed application written in C++, and there's actually an example of doing so in the samples included with the June 2008 CTP (there are also examples for other languages, including F# and Visual Basic).
That said, the same team that's developing Parallel Extensions to the .NET Framework is also working on extensive parallelism support for native applications. No CTP of that work has been released yet, but you can read more about it at.
If you would like to receive an email when updates are made to this post, please register here
RSS
Trademarks |
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by Darryl Gove
Published February 2014
RAW hazards are a performance issue that can impact all types of processors. The cost of a RAW hazard can be surprisingly large. In many cases, these hazards can be easily avoided. To understand the problem, we need to understand a little bit about how processors work.
A RAW hazard is a read-after-write problem. An application has stored a value to memory, and subsequently it wants to load that value back from memory. This is a common situation, so most chips contain hardware that makes this an efficient operation. If this hardware were not present, there would be a cost to this common style of code. However, there are some situations where this hardware is unable to work, and this will cause the processor to stall due to a RAW hazard.
When a processor stores a value, the value does not instantly get sent to memory. Memory is divided into chunks called cache lines—often 64 bytes in size. In order to store a value into a cache line, the entire cache line needs to be fetched from memory, the stored bytes need to be updated, and then the modified cache line needs to be written back to memory. This process takes some time: basically the time needed to fetch the cache line from memory.
To ensure that the processor does not stall waiting for the cache line to be fetched from memory, there is a structure that holds a list of all the pending store operations. This structure could be called a store queue or a store buffer. When a store operation is performed, the stored value is added to this list, and it remains in the list until the cache line, where the value will be stored, has been fetched from memory. Once the cache line has been fetched, the store can proceed, and the modified cache line can be written out to the caches and, eventually, to memory. The value may remain in the store queue for a significant number of cycles, while it waits for the cache line to be fetched from memory.
If there is a store of a value to an address, and then later there is a load from that address, it would take a long time for the load to obtain the value if the processor had to wait for the completion of the fetch of the cache line from memory. So rather than having to wait, most processors have a bypass operation where a load operation will check the store queue for the most recent data, before fetching it from memory.
If the bypass operation works, then the load can quickly get the value from the store queue. A RAW hazard occurs when there has been a prior store to the address, but for some reason the bypass operation is unable to work. In this case, the load has to wait until the stored value reaches the caches. This can take a significant number of cycles.
There are a number of reasons why the bypass operation might not work. The exact situations will depend on the complexity of the bypass hardware. More-complex hardware can avoid more situations.
Bypass hardware should always be able to handle a situation in which there is a single store of a value to an address, and there is a subsequent load from the same address of a value of the same size as the store. For example, if an integer is stored to an address in memory, then the hardware should be able to bypass this value to a subsequent load of an integer from the same address.
There are some situations in which the bypass might not be able to work. If the bypass does not work, then there will be a stall until the stored data is available from the cache. This stall will often have the same kind of cost as a load from memory. The following is a non-exhaustive list of the kinds of situations in which the hardware might not be able to bypass a value from an earlier store to a later load:
There are some situations in which code, that looks reasonable to a developer, can cause a RAW hazard in the hardware. A common code pattern is when a developer needs to manipulate bytes and concatenate the bytes into an integer. This operation might be to load four misaligned bytes of data from a buffer into an integer, or it could be to simulate a big endian load on little endian hardware. Consider the snippet of code shown in Listing 1:
int misaligned_load_int(char* ptr) { int temp; memcpy(&temp, ptr, sizeof(int)); return temp; }
Listing 1
The memory pointed to by
ptr has no alignment guaranty, so on hardware that cannot handle misaligned loads, the call to
memcpy() might well become a sequence of byte loads and stores equivalent to the code in Listing 2. In fact, many developers might write the code shown in Listing 2 in order to perform the same operation.
int misaligned_load_int(char* ptr) { int temp; ((char*)&temp)[0] = ptr[0]; ((char*)&temp)[1] = ptr[1]; ((char*)&temp)[2] = ptr[2]; ((char*)&temp)[3] = ptr[3]; return temp; }
Listing 2
From the code in Listing 2, the compiler will generate a sequence of four load-byte instructions, together with four store-byte instructions, followed by an integer load. This is a situation in which we are storing data of one size and then attempting to load data of a different size; consequently, the hardware might not be able to perform the bypass from the stored value to the load.
Another situation in which code might cause a potential RAW hazard is when the compiler is unable to directly use the value being stored to memory, and it needs to reload the code to ensure correctness. This happens when a variable is declared as being
volatile or when there might be another pointer that could alias to the address. Consider the code in Listing 3:
void update(int *value1, int *value2) { *value1++; *value2++; return *value1; }
Listing 3
In Listing 3, the store to
value1 needs to be performed because the compiler does not know whether
value1 and
value2 point to the same location. If they are held at the same location, then the update of
value2 will change the result returned from the read of
value1.
This case is interesting for a couple of reasons. Most hardware should be fine with bypassing the store of
value1 to its subsequent load. So although the code has a potential RAW hazard, most processors will be able to deal with it. However, if
value1 and
value2 do point to the same location in memory, then there might be two stores to the same location in the store queue, and the bypass operation might not work.
Many situations with RAW hazards have trivial fixes. The fix is typically to avoid loading a value that has just been stored to memory. Sometimes the compiler can do this automatically, and sometimes it needs intervention from the developer.
The situation in which the RAW hazard is caused by different sizes requires the developer to recode using logical operations rather than passing the data through memory. If we need to access data stored using byte-sized store operations as an integer, we can load the bytes, and then combine them in a register, rather than combining them in memory. We can rewrite the
misaligned_load_int() example shown in Listing 2, for big endian hardware, as shown in Listing 4:
int misaligned_load_int(char* ptr) { int temp; temp = (ptr[3]<<24) + (ptr[2]<<16) + (ptr[1]<<8) + ptr[0]; return temp; }
Listing 4
If we take the earlier example of
update() in Listing 3, we can manually check whether the two locations are separate and handle the two situations appropriately, as shown in Listing 5. Such a code sequence introduces the overhead of testing the two pointers and branching based on the results. So it is likely to be slower than the original code if the two pointers are different. However, if the processor does suffer from RAW hazards, and the two pointers frequently point to the same location, then the cost of the branches might be less than the cost of the RAW hazard.
void update(int *value1, int *value2) { if (value1==value2) { *value1+=2; return value1; } else { int temp = *value1++; *value2++; return temp; } }
Listing 5
A RAW hazard in a profile looks like time spent on a load instruction. It is often hard to tell that the time spent on the load is due to RAW hazards and not due to some other reason for a load taking time, for example, cache misses.
There are some clues in the disassembly. For the cause to be a RAW hazard, there must be previous stores to the same address. If the data is being held on the stack, then the disassembly will clearly indicate that the address is the same offset from the stack pointer.
However, inspecting the disassembly can require some patience. Many processors will provide hardware counters that indicate whether a RAW hazard occurs or not. So this can be an easy way to determine whether RAW hazards are occurring. Combining the performance counters with a profiling tool will often indicate the exact places in the code where the RAW hazards are occurring.
Listing 6 is an example of using the Oracle Solaris Studio Performance Analyzer on one of the example code snippets. The application has been profiled on a SPARC T4 processor from Oracle using the hardware performance counter named
RAW_hit_st_buf, which counts RAW hazard events.
$ collect -h RAW_hit_st_buf ./a.out $ er_print test.1.er (er_print) metrics e.RAW_hit_st_buf (er_print) src misaligned_load_int_bad2 Excl. RAW_hit_st_buf Events ... 42. int misaligned_load_int_bad2(char* ptr) 0 43. { 44. int temp; 0 45. ((char*)&temp)[0] = ptr[0]; 0 46. ((char*)&temp)[1] = ptr[1]; 0 47. ((char*)&temp)[2] = ptr[2]; 0 48. ((char*)&temp)[3] = ptr[3]; 0 49. return temp; 100000302 50. }
Listing 6
The profile indicates the locations in the code where RAW hazards are a problem.
The code in Listing 7 contains examples of routines that have a RAW hazard and alternative versions of the code which avoid the RAW hazards. Note that the code uses the Oracle Solaris call
gethrtime(), which is a low-overhead way of getting a high-resolution time stamp. A more portable way of doing this would be to use a call such as
gettimeofday(), but this would have a higher overhead.
#include <stdio.h> #include <sys/time.h> #include <string.h> void tick() { hrtime_t now = gethrtime(); static hrtime_t then = 0; if (then>0) printf("Elapsed = %f ns\n", 1.0*(now-then)/100000000.0); then = now; } int update_bad(int *value1, int *value2) { (*value1)+=1; (*value2)+=1; return *value1; } int update_good1(int *value1, int *value2) { if (value1==value2) { (*value1)+=2; return *value1; } else { int temp = *value1+=1; (*value2)+=1; return temp; } } int misaligned_load_int_bad1(char* ptr) { int temp; memcpy(&temp, ptr, sizeof(int)); return temp; } int misaligned_load_int_bad2(char* ptr) { int temp; ((char*)&temp)[0] = ptr[0]; ((char*)&temp)[1] = ptr[1]; ((char*)&temp)[2] = ptr[2]; ((char*)&temp)[3] = ptr[3]; return temp; } int misaligned_load_int_good(char* ptr) { int temp; temp = (ptr[3]<<24) + (ptr[2]<<16) + (ptr[1]<<8) + ptr[0]; return temp; } #define COUNT 100000000 #define COUNT2 300000000 void main() { char buffer[1000]; tick(); printf("Misaligned load v1 (bad) memcpy()\n"); for(int i=0;i<COUNT;i++) misaligned_load_int_bad1(&buffer[1]); tick(); printf("Misaligned load v2 (bad) byte copy\n"); for(int i=0;i<COUNT;i++) misaligned_load_int_bad2(&buffer[1]); tick(); printf("Misaligned load good\n"); for(int i=0;i<COUNT;i++) misaligned_load_int_good(&buffer[1]); tick(); int value1, value2; printf("\nUpdate bad -- different addresses\n"); for(int i=0;i<COUNT2;i++) update_bad(&value1,&value2); tick(); printf("Update bad -- same address\n"); for(int i=0;i<COUNT2;i++) update_bad(&value1,&value1); tick(); printf("Update good -- different addresses\n"); for(int i=0;i<COUNT2;i++) update_good1(&value1,&value2); tick(); printf("Update good -- same address\n"); for(int i=0;i<COUNT2;i++) update_good1(&value1,&value1); tick(); }
Listing 7
As with all microbenchmarks, you need to be careful that the compiler does not realize that the code is pointless and optimize it all out, or optimize it in other ways that break the effect that the code is trying to demonstrate.
For the code in Listing 7, the compiler must not perform a couple of optimizations. Function inlining needs to be switched off; if it is enabled, the compiler will almost certainly recognize that no useful work is being performed by the code, and it will eliminate all the loops. The second optimization that needs to be disabled is recognition of
memcpy() function calls. If the compiler recognizes the
memcpy() call, it will probably replace it with more-efficient code, and it might even generate code that removes the RAW hazard.
For the Oracle Solaris Studio compiler, an optimization level of
-O will not enable function inlining, and the flag
-xbuiltin=%none will tell the compiler not to replace calls to
memcpy() with inline code. The results from compiling the microbenchmark and running it on an old Oracle Solaris x86 system are shown in Listing 8:
$ cc -O -xbuiltin=%none raw.c $ ./a.out Misaligned load v1 (bad) memcpy() Elapsed = 24.738033 s Misaligned load v2 (bad) byte copy Elapsed = 11.100576 s Misaligned load good Elapsed = 4.348355 s Update bad -- different addresses Elapsed = 13.264937 s Update bad -- same address Elapsed = 17.670419 s Update good -- different addresses Elapsed = 13.888094 s Update good -- same address Elapsed = 13.587685 s
Listing 8
The results in Listing 8 show that code to handle misaligned data using
memcpy() is quite painfully slow—about 6x slower than the logical operations that replace it: 24 seconds versus 4 seconds. This is partly due to the cost of a function call to
memcpy(), but also due to the RAW hazard. The results from the code that uses loads and stores of bytes still has the RAW hazard and is about 3x slower than the logical operations: 11 seconds versus 4 seconds.
The results in Listing 8 from the code that updates two memory locations shows interesting, but expected, behavior. If the two locations are different, then the original code is marginally faster than the code that includes the overhead of checking for potential RAW hazards: 13.3 seconds versus 13.9 seconds. However, if the two addresses are the same, then the original code hits a significant slowdown: performance drops from 13.3 seconds to 17.7 seconds. The alternative code has some overhead above the original code, but avoids the slowdown when the two pointers indicate the same location; the original code took 13.3 seconds, and the code with the workaround takes about 13.6 seconds. The important thing to recognize here is that the new code is perhaps slightly slower, but it avoids a significant potential slowdown.
RAW hazards can become a significant cause of processor stall. However, they are a condition that can be resolved or avoided in many situations.. He has a blog at.
Blog | Facebook | Twitter | YouTube | http://www.oracle.com/technetwork/articles/servers-storage-dev/raw-hazards-solaris-studio-2152944.html | CC-MAIN-2015-32 | refinedweb | 2,542 | 58.92 |
I want to search and blank out those sentences which contain words like “masked 111″,”My Add no” etc. from another sentences like “XYZ masked 111” or “Hello My Add” in python.How can I do that? I was trying to make changes to below codes but it was not working due to spaces.
def garbagefin(x): k = " ".join(re.findall("[a-zA-Z0-9]+", x)) print(k) t=re.split(r's',k) print(t) Glist={'masked 111', 'DATA',"My Add no" , 'MASKEDDATA',} for n, m in enumerate(t): ##to remove entire ID if m in Glist: return '' else: return x
The outputs that I am expecting is:
garbagefin("I am masked 111")-Blank garbagefin("I am My Add No")-Blank garbagefin("I am My add")-I am My add garbagefin("I am My MASKEDDATA")-Blank
Answer
You can also use a regex approach like this:
import re Glist={'masked 111', 'DATA',"My Add no" , 'MASKEDDATA',} glst_rx = r"b(?:{})b".format("|".join(Glist)) def garbagefin(x): if re.search(glst_rx, x, re.I): return '' else: return x
See the Python demo.
The
glst_rx = r"b(?:{})b".format("|".join(Glist)) code will generate the
b(?:My Add no|DATA|MASKEDDATA|masked 111)b regex (see the online demo).
It will match the strings from
Glist in a case insensitive way (note the
re.I flag in
re.search(glst_rx, x, re.I)) as whole words, and once found, an empty string will be returned, else, the input string will be returned.
If there are too many items in
Glist, you could leverage a regex trie (see here how to use the
trieregex library to generate such tries.) | https://www.tutorialguruji.com/python/how-to-search-a-string-with-spaces-within-another-string-in-python/ | CC-MAIN-2021-43 | refinedweb | 277 | 84.17 |
Difference between revisions of "Textmode IDE development"
Revision as of 11:43, 6 May 2012
See also Textmode IDE for more user-oriented hints, and go32v2 development for hints about the particular dos problems of the IDE.
Contents
General problems
While the obvious task for the textmode IDE is of course fixing several or some of the 80 bugs, some other stuff comes to mind as future projects. Nearly all have to do with the fact that the IDE effectively stopped evolving significantly since 1.0 times. A lot of problems and uglinesses lie in the TP/DOS legacy from this period:
- the fact that it uses Dos, rather than Sysutils for its filename operations.
- Now that the compiler uses sysutils mostly, the Dos versions are the less tested ones.
- the fact that shortstrings (or parts of them) are used for filenames.
- under windows there is no support for unc-paths
- Even the shortstring filename handling is far from perfect, since the IDE clearly hasn't had the end-user testing for *nix targets that dos/win32 had. Grepping for fixfilename() might yield such problems (like e.g. bug #5614), where filenames are pretty printing, however effectively killing case sensitive filesystems. Bringing this up to ansistring/sysutils level might also help to unify these routines between textmode IDE and Lazarus.
- Some functionality is deprecated or not active or documented. Examples are browser and code folding (see comments of bug #6696 Some of the functionality mentioned in #11583 might also be "newer"). Note that this kind of functionality is often not finished, e.g. afaik there is no way to save folds. (make them persistent some how). Also the editor components seem to have incremental syntaxhighlighting under ifdef.
- Another major problem is that the docs have significantly grown. On a PII-233 (128MB and a more recent 20GB disc) it took 20-40 minutes to install the html files from the help. Nowadays we have chm support in the FPC tree, maybe it is time to kill all the old helpfile formats and standarize on CHM for a while. (removing the need to have separate files html is I think more important than killing e.g. .tph) Initial CHM support added to trunk See the separate section about this topic.
- On *nix, terminals are swiftly adopting UTF-8 as output type. Supporting this, even very minimally (say ISO8859-1+linedrawing) will be a quite complex task. All output unicode support requires a FV rewrite.
Compatibility
In the past the textmode IDE was compatible with lots of compilers and platforms that are dead. This compability has not been maintained/tested for close to a decade, so it is doubtful it works at all. So IMHO it can be removed, and dependancies on things like sysutils are no longer forbidden.
ansistringification
Since FV has reduced in meaning, maybe it can be modernised using the delphi model a bit (streaming and constructors/destructors). I know this is heresy, but a tpobj version could continue to exist. It is mainly for the IDE. I also don't know if it is worthwhile at all (most notably exploiting if FV exploits the static nature of objects...).
Maybe a good first approximation would be to try to introduce ansistring everywhere. (Florian has said he has tried this in the past, but that he got stuck. I did an attempt and also got stuck.
I did a real minor attempt to kill some redundant string routines, but are stuck with the fact that one can't import sysutils into a major TV or IDE because that will cause incompatabilities due to the pstring type. (which is defined both by TV as by sysutils). This is probably the reason why wutils wraps so many sysutils routines, together with the fact that cross-unit overloading seems a bit ambiguous if the relevant parameter types are convertable to eachother (e.g. shortstring and ansistring, or char) It would be major FV reengineering, and a significant loss of backwards compat to fix this. )
It could be easily remedied by reworking TV/IDE to use a "pshortstring" everywhere, which is still compatible with pstring for backwards compatibility as long as sysutils isn't added.
A second stage would replace all path related strings by ansistrings.
For this it is also interesting to look at the C++ version, since there some features only more recently introduced to pascal are added (operator overloading, generics). However a new codebase doesn't have to strictly follow C++, since FPC has certain features that are useful (open arrays, arrays of const, dyn arrays) too.
note: it seems that (static) TP objects are not initialized/finalized. Using ansistrings with them is thus hazardous. Heap TP objects seem to be initialized/finalized. Fixed by Sergei r16632,16635
Chm Support
The chm support was mainly meant to remedy the defects of the loose html based help; mostly install time, HD size (fragmentation, uncompressed) the fact that indexing must be done on the fly, and the constant little problems with filenames in generated html files.
Extract the loose html help on a Athlon XP2000 takes 8 minutes, and creating the index another 5. CHM reduces this to effectively zero, and adds the fulltext search capability. On the P-II 233MHz that I occasionally use for Dos testing, times can be over an hour on plain dos.
The CHM support has been in the IDE since 2.2.4, and most seems to be working. Sometimes the html generation from the latex documents has problems, but strictly speaking that is not a chm problem
The LaTeX docs used to be a problem, but recently there has been progress in this department, see Chm backend for fpdoc, latex part. Other improvements to be done:
- Links over CHM file bounderies still have to be fixed, this is needed for an effective main page. I already have created a simple main page that works in Windows. (and can generate it) (done an initial implementation)
- installation into the IDE by the installer. (done but not properly installed yet)
- Index majeur?
- index for latex pages. (done for ref archive from ref.kwd)
- preparing the main index takes several seconds on a XP 2000+, specially with LCL.chm installed. Might be annoying on slow computers. Cache? It might also be that the index collection, suffers from the inserted sorting dimensioning problem. (tcollections and tlist are both one big array of pointers. (Ordered) Inserting in such an large array requires a lot of fields to move to make room )
- there are problems with labels. E.g. from the main TOCs. For now they are stripped, but maybe first labels should be tried, and only then revert to main page.
- The ref/user/prog chms are in UTF-8 which is not nice for the textmode IDE. (fixed in +/- 2.4.0, there might be detail bugs left though)
CHM bounderies problem
This problem is partial to a deeper problem in the textmode IDE. The way a help page/topic is identified in the textmode IDE is by two (16-bit?) integers. One is the fileid, the other is the topicid in the file.
HTML and CHM's however work string based. IOW a string for file, and a string for the topic (combination of path/file#label). This is solved by allocating a fileid for each chm dynamically onload, and similarly for the topic files. The html subsystem maintains a links-in-current topic cache, and the indexes into that cache act as topicids. (iow a bit dynamic, not all URLs in the chm have one).
However since helpfiles are loaded on a need-to basis, and one might encounter a link to a.chm/path/file in another chm before a.chm is loaded, making it hard to resolve the IDs. This is currently solved by having a registry of CHM files as a global. However that totally bypasses the central helpsystem.
The plain html help didn't suffer from this because they cheated: all html must be installed in one directory, and links are fixed in the html itself. (refer to hardcoded paths ../prog/) So the entire html became one big helpfile in practice. Which is fine as a hack, but not really nice or reproducable for other formats.
A minor rewrite that changes the idenfification to something else (a record with both string and topic id's?) is a possibility, but for that I must first dig up examples of all helpfile types supported and test how they work.
Files of the IDE
Here a short list of the units in the IDE, and their contents. A rough size in kb is added to indicate the relative size of the unit.
Some functionality seems to be split between a w* unit and a fp* unit. (wini,fpini, wviews, fpview). Possibly this is an artifact of an older division between reusable and non reusable units. The fact that there are multiple utility units is also a bit of an indicator for this.
If you know/find out what the criteria herefore is, please add it here. If you find out something about a certain unit, make a link out of it prefixed with fv: (see the wutils example).
Besides units, there are also a bunch of include files, most of which seem to be part of fpide, and group routines according to menu category (file, edit, compile etc)
Classchart of objects + FV + IDE
An improvised classchart (objectchart?) of all code containing TP style objects ( unit objects, FV and the IDE source) is available here: Object Chart (Postscript view with GV) or pdf version, less often updated
Debugging the IDE
Note that the methods describe here are mostly for *nix.
With GDB tty
Normally one would debug the IDE as follows (Unix)
Terminal Window 1:
tty
Example output:
/dev/pts/5
Terminal Window 2:
gdb ./fp tty /dev/pts/5 r
The tty command should then reroute all I/O to tty /dev/pts/5 (Terminal window 1), leaving Terminal Window 2 free to communicate with GDB.
Unfortunately, due to the special keyboard support of the textmode IDE (to capture all ctrl-alt variants) input is not properly rerouted. This means you can debug IDE startup (and more if you save state smartly), but not the normal working. This method is mainly useful when debugging the start of the IDE.
With GDB attach
This method works better if you want to debug after the IDE has start up.
Terminal Window 1:
Run the IDE from the commandline, and wait till it has start up.
Terminal Window 2:
Find the PID of the running IDE In window 1 using ps aux |grep fp Start gdb with the correct "fp" file (the one that is running!) Type attach <pid> on the GDB cmdline Note that gdb will immediately break upon attach. If you want to carry on, type "c" (continue)
Writeln like
While developing the CHM package I needed to debug browsing also. For this, at first I simply wrote to stderr, and pipe the output to a different terminal (using bash as shell)
Terminal Window 1
tty
Example output:
/dev/pts/5
Terminal Window 2
./fp 2> /dev/pts/5
However, while this would work, it seems sometimes buffering is a problem. Adding a flush would help, but then you have to go after all those writelns again. So it is better to extract it to a procedure. Such a procedure already existed in wutils, and I enhanced it a bit. There are two versions now. "DebugMessage" is the old one, and DebugMessageS is the new one.
To avoid any garbage on the cmdline, all debug messages are always placed under IFDEF. Historically the define "DEBUG" was used for it, but apparantly this is also used in the compiler, and a broken debug feature in the compiler breaks debugging the IDE this way. So I use WDEBUG (mostly in whtmlhlp). The typical debug code fragment then becomes:
{$IFDEF WDEBUG} DebugMessageS({$i %file%',' Adding Name "'+Name+'"',%line%,'1'); {$endif WDEBUG}
Note that we use a compiler feature to fill in filename + linenumber for us.
On Windows:
fp.exe 2> logme.txt
Exceptions to stderr
When debugging the IDE, I often change the RTL to log errors to stderr instead of stdout, since stderr is logged using the above 2> redirects, I use the following patch:
=================================================================== --- sysutils/sysutils.inc (revision 12440) +++ sysutils/sysutils.inc (working copy) @@ -234,7 +234,7 @@ i : longint; hstdout : ^text; begin - hstdout:=@stdout; + hstdout:=@stderr; Writeln(hstdout^,'An unhandled exception occurred at $',HexStr(PtrUInt(Addr),sizeof(PtrUInt)*2),' :'); | https://wiki.freepascal.org/index.php?title=Textmode_IDE_development&diff=prev&oldid=58797&printable=yes | CC-MAIN-2020-45 | refinedweb | 2,100 | 63.19 |
Rob Hunter wrote: I'm trying to compile the applet code on the Linux machine and it's complaining about the line :
warning: The import javax.swing.JApplet is never used
import javax.swing.JApplet;
I'm trying to extend JApplet in this class.
Pat Farrell wrote:Expanding on what Tim H said, there are limits. Which raises the question: why are you trying to use applets in 2010? They made sense last century.
Tim Holloway wrote: Sometimes you have really gnarly logic that is best handled client-side. Your options are:
1. JavaScript (which I like less every time I use it)
2. ActiveVirus, er ActiveX controls. Assuming that you never intend to sell anything to anyone who uses anything but IE/Windows
3. Flash. Assuming you like security issues and having to do your editing with non open-source products
4. Java Applets. | http://www.coderanch.com/t/522547/Linux-UNIX/Applets-Linux | CC-MAIN-2014-49 | refinedweb | 145 | 68.57 |
Manage sitemaps with the Sitemaps report
A sitemap is a file you create for web crawlers, such..
- Where possible, use absolute or complete links rather than relative links. For instance, when linking to another page in your site, link to than simply
mypage.html.
URL not allowed
Your sitemap includes some URLs that are at a higher level or different domain than the sitemap file.
Higher level: If your sitemap is listed under, the following URLs are not valid for that sitemap:- it's at a higher level than the sitemap- it's in a directory parallel to the sitemap
Different domain: Check that the URLs all begin with the same domain as your sitemap location. For instance, if your sitemap is at, the following URLs are not valid for that sitemap:- Missing "www"- Missing "http"- Using https rather than http
Compression error
Google encountered an error when trying to uncompress your compressed sitemap file. Recompress your sitemap (using a tool such as gzip), upload it to your site, and resubmit it.
Empty sitemap
Your sitemap doesn't contain any URLs. Check your sitemap and ensure that it is not empty. If your sitemap uses the sitemap protocol, ensure that the URLs are tagged correctly.
Sitemap file size error: Your sitemap exceeds the maximum file size limit...
Your sitemap is larger than 50MB when uncompressed. If your sitemap is larger than the limit, break it into several smaller sitemaps and list these in a sitemap index file and submit the sitemap index file(s).
Invalid attribute value
You assigned an invalid value to an XML tag attribute. Check your sitemaps to make sure that only the allowed attributes are present, and that you assign only allowed values according to the sitemap specifications. Check your attributes and values for typos.
Invalid date
Your sitemap contains one or more invalid dates. This error could be because a date is in the incorrect format, or the date itself is not valid. Dates must use W3C Datetime encoding, although you can omit the time portion. Make sure your dates match one of the following W3C Datetime formats:
2005-02-21 2005-02-21T18:00:15+00:00
Specifying time is optional (the time defaults to 00:00:00Z), but if you do specify a time, you must also specify a time zone.
Invalid tag value
Your sitemap contains one or more tags with an invalid value. sure that the URLs listed in your sitemap are encoded for readability and escaped properly. Check for any incorrect characters such as spaces or quotes. You also try copying the URL into a browser to see if the browser can understand the URL and load the page.
Invalid URL in sitemap index file: incomplete URL
Your sitemap index file doesn't include the full URL for each Sitemap file.
Update your sitemap index file to include the complete path to each listed sitemap file, then resubmit.
Invalid XML: too many tags
Your sitemap contains duplicate tags. For example, the following entry would cause this error because the <loc> tag is listed twice:
<url> <loc></loc> <loc></loc> <lastmod>2005-01-01</lastmod> <changefreq>monthly</changefreq> <priority>0.8</priority> </url>
The error lists the problematic tag and the line number. Remove the duplicate tag and resubmit your sitemap.
Missing XML attributeA tag in your sitemap is missing a required attribute. Check your sitemaps to make sure that no required attributes are missing. Once you have fixed the attribute values, resubmit your sitemap.
Missing XML tag
One or more entries in your sitemap is missing a required tag. The error message lists the line number. Review the sitemap fundamentals page for information on required tags.
Missing thumbnail URL
One or more video entries is missing a URL to a thumbnail image. Make sure that the location of any thumbnail URLs are specified using the <video:thumbnail_loc> tag.
Missing video title
One or more video entries is missing a title. Make sure that each video in your sitemap has a title, specified in the the <video:title> tag.
Incorrect sitemap index format: Nested sitemap indexes
One or more entries in your sitemap index file uses its own URL or the URL of another sitemap index file.
A sitemap index file can't list other sitemap index files, but only sitemap files.Remove any entries pointing to sitemap index files, then resubmit your sitemap.
Parsing errorGoogle could not parse the sitemap's XML.
Often, this problem is caused by an unescaped character in the URL. As with all XML files, any data values (including URLs) must use entity escape codes for certain characters such as & ' " < > symbols. Be sure that your URLs are properly escaped.
Temporary error
Our system experienced a temporary problem that prevented us from processing your sitemap. Generally, when you receive this error, you do not need to resubmit your sitemap. Google can try to retrieve your sitemap again later. If the error still exists after several hours, try resubmitting your sitemap.
Too many sitemaps in sitemap index file
Your sitemap index file lists more than 50,000 sitemaps. Split your sitemap index into multiple sitemap index files and ensure that each lists no more than 50,000 sitemaps.
Too many URLs in sitemap
Your sitemap lists more than 50,000 URLs. Split your sitemap into multiple Sitemaps and ensure that each contains no more than 50,000 URLs. You can also use a sitemap index file to manage your sitemaps.
Unsupported formatYour sitemap is not in a supported format. Sitemaps must be in XML format, and use the correct header.
Common XML mistakes:
- Your sitemap must use the correct header. For example, if your sitemap contains video information, it would have the following header:
<?xml version="1.0" encoding="UTF-8"?> <urlset xmlns="" xmlns:
- The namespace in the header must be "" (not .9).
- All XML attributes must enclosed in either single quotes (') or double quotes (") and those quotes must be straight, not curly. Word-processing programs such as Microsoft Word can insert curly quotes.
Path mismatch: Missing www
The path to your sitemap does not contain the
www prefix (for example,), but the URLs it lists do (for example,)., modify your sitemap to add "www" to all the URLs to match your sitemap location.
Incorrect namespace
The root element of your sitemap doesn't contain the correct namespace, or the namespace is declared incorrectly, or has a typo or incorrect URL.
Be sure that you are using the correct namespace for your file type. For example:
- A sitemap file:
xmlns=""
- A video sitemap file:
xmlns:video=""
- A sitemap index file:
- Other sitemap types...
Leading whitespace
Your sitemap begins with leading whitespace, rather than a namespace declaration. XML files should begin with the XML declaration that specifies the version of XML being used.
This error won't prevent Google from processing your sitemap, but you might want to remove the whitespace so that the file adheres to the XML standard and you no longer see this error.
HTTP error [specific code]
Google encountered an HTTP error when when attempting to download your sitemap. This message displays the status code we received (for example, 404). Make sure that the sitemap URL you specified is correct and that the sitemap exists at that location. Then, resubmit your sitemap.
Thumbnail too large
The video thumbnail image specified in your sitemap is too large.. | https://support.google.com/webmasters/answer/183669?hl=en&ctx=cb&src=cb&cbid=3kxez3xw70yp&cbrank=1&visit_id=0-636231455604251266-1569013554&rd=1 | CC-MAIN-2017-09 | refinedweb | 1,231 | 72.56 |
I also blog frequently on the Yesod Web Framework blog, as well as the FP Complete blog.
See a typo? Have a suggestion? Edit this page on Github
In this lesson, we just want to get set up with the basics: tooling, ability to compile, basic syntax, etc. Let’s start off with the tooling, you can keep reading while things download..
Your gateway drug to Rust will be the
rustup tool, which will
install and manage your Rust toolchains. I put that in the plural,
because it can manage both multiple versions of the Rust compiler, as
well as cross compilers for alternative targets. For now, we’ll be
doing simple stuff.
Both of these pages will tell you to do the same thing:
curl -sSf | sh
Read the instructions on the rust-lang page about setting up your
PATH environment variable. For Unix-like systems, you’ll need
~/.cargo/bin in your
PATH.
Along with the
rustup executable, you’ll also get:
cargo, the build tool for Rust
rustc, the Rust compiler
Alright, this part’s easy:
cargo new hello && cd hello && cargo run.
We’re not learning all about Cargo right now, but to give you the basics:
Cargo.tomlcontains the metadata on your project, including dependencies. We won’t be using dependencies quite yet, so the defaults will be fine.
Cargo.lockis generated by
cargoitself
srccontains your source files, for now just
src/main.rs
targetcontains generated files
We’ll get to the source code itself in a bit, first a few more tooling comments.
For something this simple, you don’t need
cargo to do the
building. Instead, you can just use:
rustc src/main.rs && ./main.
If you feel like experimenting with code this way, go for it. But
typically, it’s a better idea to create a scratch project with
cargo new and experiment in there. Entirely your decision.
We won’t be adding any tests to our code yet, but you can run tests in
your code with
cargo test.
Two useful utilities are the
rustfmt tool (for automatically
formatting your code) and
clippy (for getting code advice). Note
that
clippy is still a work in progress, and sometimes gives false
positives. To get them set up, run:
$ rustup component add clippy-preview rustfmt-preview
And then you can run them with:
$ cargo fmt $ cargo clippy
There is some IDE support for those who want it. I’ve heard great things about IntelliJ IDEA’s Rust add-on. Personally, I haven’t used it much yet, but I’m also not much of an IDE user in the first place. This crash course won’t assume any IDE, just basic text editor support.
Alright, we can finally look out our source code in
src/main.rs:
fn main() { println!("Hello, world!"); }
Simple enough.
fn says we’re writing a function. The name is
main. It takes no arguments, and has no return value. (Or, more
accurately, it returns the unit type, which is kind of like void in
C/C++, but really closer to the unit type in Haskell.) String literals
look pretty normal, and function calls look almost identical to other
C-style languages.
Alright, here’s the first “crash course” part of this: why is there an
exclamation point after the
println? I say “crash course” because
when I first learned Rust, I didn’t see an explanation of this, and it
bothered me for a while.
println is not a function. It’s a macro. This is because it takes
a format string, which needs to be checked at compile time. To prove
the point, try changing the string literal to include
{}. You’ll get
an error message along the lines of:
error: 1 positional argument in format string, but no arguments were given
This can be fixed by providing an argument to fill into the placeholder:
println!("Hello , world! {} {} {}", 5, true, "foobar");
Take a guess at what the output will be, and you’ll probably be
right. But that leaves us with a question: how does the
println!
macro know how to display these different types?
More crash course time! To get a better idea of how displaying works,
let’s trigger a compile time error. To do this, we’re going to define
a new data type called
Person, create a value of that type, and try
to print it:
struct Person { name: String, age: u32, } fn main() { let alice = Person { name: String::from("Alice"), age: 30, }; println!("Person: {}", alice); }
We’ll get into more examples on defining your own
structs and
enums later, but you can cheat and read the Rust
book
if you’re curious.
If you try to compile that, you’ll get:
error[E0277]: `Person` doesn't implement `std::fmt::Display` --> src/main.rs:11:28 | 11 | println!("Person: {}", alice); | ^^^^^ `Person` cannot be formatted with the default formatter | = help: the trait `std::fmt::Display` is not implemented for `Person` = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead = note: required by `std::fmt::Display::fmt`
That’s a bit verbose, but the important bit is
the trait `std::fmt::Display` is not implemented for `Person` . In Rust, a
trait is similar to an interface in Java, or even better like a
typeclass in Haskell. (Noticing a pattern of things being similar to
Haskell concepts? Yeah, I did too.)
We’ll get to all of the fun of defining our own traits, and learning about implementing them later. But we’re crashing forward right now. So let’s throw in an implementation of the trait right here:
impl Display for Person { }
That didn’t work:
error[E0405]: cannot find trait `Display` in this scope --> src/main.rs:6:6 | 6 | impl Display for Person { | ^^^^^^^ not found in this scope help: possible candidates are found in other modules, you can import them into scope | 1 | use core::fmt::Display; | 1 | use std::fmt::Display; | error: aborting due to previous error For more information about this error, try `rustc --explain E0405`. error: Could not compile `foo`.
We haven’t imported
Display into the local namespace. The compiler
helpfully recommends two different traits that we may want, and tells
us that we can use the
use statement to import them into the local
namespace. We saw in an earlier error message that we wanted
std::fmt::Display, so adding
use std::fmt::Display; to the top of
src/main.rs will fix this error message. But just to prove the
point, no
use statement is necessary! We can instead us:
impl std::fmt::Display for Person { }
Awesome, our previous error message has been replaced with something else:
error[E0046]: not all trait items implemented, missing: `fmt` --> src/main.rs:6:1 | 6 | impl std::fmt::Display for Person { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ missing `fmt` in implementation | = note: `fmt` from trait: `fn(&Self, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>`
We’re quickly approaching the limit of things we’re going to cover in a “kicking the tires” lesson. But hopefully this will help us plant some seeds for next time.
The error message is telling us that we need to include a
fmt method
in our implementation of the
Display trait. It’s also telling us
what the type signature of this is going to be. Let’s look at that
signature, or at least what the error message says:
fn(&Self, &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error>
There’s a lot to unpack there. I’m going to apply terminology to each bit, but you shouldn’t expect to fully grok this yet.
Selfis the type of the thing getting the implementation. In this case, that’s
Person.
&at the beginning makes it a reference to the value, not the value itself. C++ developers are used to that concept already. Many other languages talk about pass by reference too. In Rust, this plays in quite a bit with ownership. Ownership is a massively important topic in Rust, and we’re not going to discuss it more now.
&mutis a mutable reference. By default, everything in Rust is immutable, and you have to explicitly say that things are mutable. We’ll later get into why mutability of references is important to ownership in Rust.
Formatter. What’s the
<'_>thing after
Formatter? That’s a lifetime parameter. That also has to do with ownership. We’ll get to lifetimes later as well.
->indicates that we’re providing the return type of the function.
Resultis an
enum, which is a sum type, or a tagged union. It’s generic on two type parameters: the value in case of success and the value in case of error.
(), or unit value. This is another way of saying “I don’t return any useful value if things go well.” In the case of an error, we return
std::fmt::Error.
Resulttype to track things going wrong. This is more explicit than exception-based languages. But unlike languages like C, where it’s easy to forget to check the type of a return to see if it succeeded, or tedious to do error handling properly, Rust makes this much less painful. We’ll deal with it later.
NOTE Rust does have the concept of panics, which in practice behave similarly to runtime exceptions. However, there are two important differences. Firstly, by convention, code is not supposed to use the panic mechanism for signaling normal error conditions (like file not found), and instead reserve panics for completely unexpected failures (like logic errors). Secondly, panics are (mostly) unrecoverable, meaning they take down the current thread.
A previous version of this document said that panics are unrecoverable, and that they take down the entire thread. However, as pointed out by J Haigh, this isn’t quite true: the function
catch_unwind allows you to usually capture and recover from a panic without losing the current thread. I’m not going to go into more details here.
Awesome, that type signature all on its own gave us enough material for about 5 more lessons! Don’t worry, you’ll be able to write some Rust code without understanding all of those details, as we’ll demonstrate in the rest of this lesson. But if you’re really adventurous, feel free to explore the Rust book for more information.
Let’s get back to our code, and actually implement our
fmt method:
struct Person { name: String, age: u32, } impl std::fmt::Display for Person { fn fmt(&self, fmt: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> { write!(fmt, "{} ({} years old)", self.name, self.age) } } fn main() { let alice = Person { name: String::from("Alice"), age: 30, }; println!("Person: {}", alice); }
We’re using the
write! macro now, to write content into the
Formatter provided to our method. This is beyond the scope of our
discussion, but this allows for more efficient construction of values
and production of I/O than producing a bunch of intermediate
strings. Yay efficiency.
The
&self parameter of the method is a special way of saying “this
is a method that works on this object.” This is quite similar to how
you’d write code in Python, though in Rust you have to deal with pass
by value vs pass by reference.
The second parameter is named
fmt, and
&mut Formatter is its type.
The very observant among you may have noticed that, above, the error
message mentioned
&Self. In our implementation, however, we made a
lower
&self. The difference is that
&Self refers to the type of
the value, and the lower case
&self is the value itself. In fact,
the
&self parameter syntax is basically sugar for
self: &Self.
Does anyone notice something missing? You may think I made a
typo. Where’s the semicolon at the end of the
write! call? Well,
first of all, copy that code in and run it to prove to yourself that
it’s not a typo, and that code works. Now add the semicolon and try
compiling again. You’ll get something like:
error[E0308]: mismatched types --> src/main.rs:7:81 | 7 | fn fmt(&self, fmt: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> { | _________________________________________________________________________________^ 8 | | write!(fmt, "{} ({} years old)", self.name, self.age); | | - help: consider removing this semicolon 9 | | } | |_____^ expected enum `std::result::Result`, found () | = note: expected type `std::result::Result<(), std::fmt::Error>` found type `()`
This is potentially a huge confusion in Rust. Let me point out
something else that you may have noticed, especially if you come from
a C/C++/Java background: we have a return value from our method, but
we never used
return!
The answer to that second concern is easy: the last value generated in
a function in Rust is taken as its return value. This is similar to
Ruby and—yet again—Haskell.
return is only needed for
early termination.
But we’re still left with our first question: why don’t we need a
semicolon here, and why does adding the semicolon break our code?
Semicolons in Rust are used for terminating statements. A statement
is something like the
use statement we saw before, or the
let
statement we briefly demonstrated here. The value of a
statement is always unit, or
(). That’s why, when we add the
semicolon, the error message says
found type `()` . Leaving off
the semicolon, the expression itself is the return value, which is
what we want.
You’ll see the phrase that Rust is an expression-oriented language, and this kind of thing is what it’s referring to. You can see mention of this in the FAQ. Personally, I find that the usage of semicolon like this can be subtle, and I still instinctively trip up on it occasionally when my C/C++/Java habits kick in. But fortunately the compiler helps identify these pretty quickly.
Last concept before we just start dropping in some code. We’re going to start off by playing with numeric values. There’s a really good reason for this in Rust: they are copy values, values which the compiler automatically clones for us. Keep in mind that a big part of Rust is ownership, and tracking who owns what is non-trivial. However, with the primitive numeric types, making copies of the values is so cheap, the compiler will do it for you automatically. This is some of that automatic magic I mentioned in my intro post.
To demonstrate, let’s check out some code that works fine with numeric types:
fn main() { let val: i32 = 42; printer(val); printer(val); } fn printer(val: i32) { println!("The value is: {}", val); }
We’ve used a let statement to create a new variable,
val. We’ve
explicitly stated that its type is
i32, or a 32-bit signed
integer. Typically, these kinds of type annotations are not needed in
Rust, as it will usually be able to infer types. Try leaving off the
type annotation here. Anyway, we then call the function
printer on
val twice. All good.
Now, let’s use a
String instead. A
String is a heap-allocated
value which can be created from a string literal with
String::from. (Much more on the many string types later). It’s
expensive to copy a
String, so the compiler won’t do it for us
automatically. Therefore, this code won’t compile:
fn main() { let val: String = String::from("Hello, World!"); printer(val); printer(val); } fn printer(val: String) { println!("The value is: {}", val); }
You’ll get this intimidating error message:
error[E0382]: use of moved value: `val` --> src/main.rs:4:13 | 3 | printer(val); | --- value moved here 4 | printer(val); | ^^^ value used here after move | = note: move occurs because `val` has type `std::string::String`, which does not implement the `Copy` trait error: aborting due to previous error
Exercise 1 there are two easy ways to fix this error message: one
using the
clone() method of
String, and one that changes
printer
to take a reference to a
String. Implement both
solutions. (Solutions will be posted separately in a few days.)
We’re going to tie off this lesson with a demonstration of three different ways of looping to print the numbers 1 to 10. I’ll let readers guess which is the most idiomatic approach.
loop creates an infinite loop.
fn main() { let i = 1; loop { println!("i == {}", i); if i >= 10 { break; } else { i += 1; } } }
Exercise 2 This code doesn’t quite work. Try to figure out why without asking the compiler. If you can’t find the problem, try to compile it. Then fix the code.
If you’re wondering: you could equivalently use
return or
return () to exit the loop, since the end of the loop is also the end of the
function.
This is similar to C-style while loops: it takes a condition to check.
fn main() { let i = 1; while i <= 10 { println!("i == {}", i); i += 1; } }
This has the same bug as the previous example.
For loops let you perform some action for each value in a collection. The collections are generated lazily using iterators, a great concept built right into the language in Rust. Iterators are somewhat similar to generators in Python.
fn main() { for i in 1..11 { println!("i == {}", i); } }
Can you leave out any semicolons in the examples above? Instead of just slamming code into the compiler, try to think through when you can and cannot drop the semicolons.
Implement fizzbuzz in Rust. The rules are:
Next time, the plan is to get into more details on ownership, though plans are quite malleable in this series. Stay tuned!
Rust at FP Complete | Introduction | https://www.snoyman.com/blog/2018/10/rust-crash-course-01-kick-the-tires | CC-MAIN-2019-47 | refinedweb | 2,954 | 73.58 |
Python Line of Code Help
Bütçe $2-8 CAD / saat
Hello,
I am trying to extract the full name,first name and last name from an email.
The data comes in as follows:
| Name | Diana Yu |
What gets extracted from this is:
fullname: Name | Diana Yu |
firstN: Name
lastN: | Diana Yu |
The code is:
code: import string
import re
weblead = input_data['webleads_body']
value = [login to view URL]('\n', 26)
regex= [login to view URL](".*(Name).*")
name = [[login to view URL](0) for l in value for m in [[login to view URL](l)] if m]
fullname = name[0]
fullname = [login to view URL](' ', 1)[1]
fullname = [login to view URL]()
firstN = [login to view URL](' ', 1)[0]
firstN = [login to view URL]()
lastN = [login to view URL](' ', 1)[1]
lastN = [login to view URL]()
Seçilen:
hi there! i've been using python for over three years. and your task is to split the string. i mean, you can just use split() function to split the string. ^_^ for example. code: full_name='Name | Diana Yu |' first_nam Daha Fazla
Bu iş için 6 freelancer ortalamada $5/saat teklif veriyor
hi can you share the file and code I can help you with your project thanks.................................
Hello, I am a computer science grad (Master's degree) and a Java/Python expert with 5 years experience. I understand your project description and I can confidently help you with your task. I have a track record of Daha Fazla
hi i am python programmer.i did work similar to yours before in web scraping(clean data) .i can do your work [login to view URL] me for more information and check me profile. have a nice day
Hi, sir. Nice to meet you. I read your project description carefully and I have understood fully your requirements. I am professional in Python and have many experiences for 5+ years. So I'm very interested in your pro | https://www.tr.freelancer.com/projects/python/python-line-code-help/ | CC-MAIN-2020-16 | refinedweb | 321 | 79.8 |
Hello, which comment(s) to reply to so those people could be notified... that would be great and would be a wonderful way to learn and benefit from HubPages.
I always reply comments if I feel it is necessary or if a question is asked.People normally see the answers. Many times I get mails for the same. I think this a good practice.
jyoti kothari
It would be an ok idea, most people leave a comment for the person and never return (because you said what you wanted to, they could accept it or delete it, they got your feedback). If you wanted an ongoing discussion with someone you would need to notify them by email or something, or if it's about a topic, make a forum post of it and then you can talk back and forth!
At least this is the way I understand it,
-thranax
Glassvisage I would love this idea. There are so many times where I'll make a comment on a hub with the intention on going back and seeing if the hubber replied to a statement or question, but completely forget about it. Most of the time I'll run across the hub months later and in deed there was a reply posted.
Thranax, I think she's talking about for hubbers and not unregistered people, as if they want the answer, they'll more than likely bookmark the page and come back unless they find the answer in the meantime. On one of my hubs, I'll frequently get a discussion going as to care and what's up with their pet, as unregistered hubbers never seem to notice the contact button.
But, in terms of hubbers, most of the time the hubber makes a comment or asks a "light" non-serious question, but they may want to read the answer or check for a reply, and in this case it seems unrealistic to bookmark every hub that a hubber comments on to go back and pull it up later that day or a day or so later to check the comment. If that makes sense>
True, but your posts, and have pictures etc. I think this would be a better idea for what your thinking of personally
Here is an example of what the idea is:
^I made that up quickly
So in your comment section you just want a bunch of "You hub is great," "Good information," etc. opinions? I'd much rather more discussion than that. That's just me though. I'm not a fan of simplle one phrased comments like that. I mean I get tons of unregistered users who come back and ask questions and talk and even try to help out other people from what I've told them. This makes me feel like my hubs and how I've tried to help people with my replies to their comments truly helpful and meaningful to that person.
I always forget about this, and by the time I find it again, it's been weeks or months after the fact. :-/
That would be great if HP could do that. It is nice that we get an email when someone comments on our own hubs so we can respond within a reasonable time.
Most of the time when I comment I just look back at the Hub to see what the Hubber wrote about my comment. Most people are pretty good at writing back comments in my experience.
Have you tried the "comments you made" link in the "your account" section?
It shows all the hubs you commented on, and also shows how recently other comments have been made on the same hub.
Tharanx,
There is no such option in profile page. So one has to discuss the matter in the comments section itself as not everybody comes to forum.
Isabella
I have tried comments you made option in ...it is a good one.
by Liz Elias2 months ago
So, I've always thought it was the polite thing to do to reply to commenters, and thank them for their time and input, and I've made an effort to do so consistently.However, I'm wondering if this is now being... Sherri6 years ago
I'm sure there are many reasons for and against responding to comments left by your readers. What do you think?
by Dale Mazurek LongTimeMother6 days ago
For years I have been diligent about responding to questions left on my hubs. But now I've discovered comments are being published on my articles without appearing in my Comments section, so I look like I'm rude and...
by David Livermore9 days. | http://hubpages.com/community/forum/5993/replying-to-comments-with-a-comment | CC-MAIN-2017-13 | refinedweb | 781 | 77.16 |
Agenda
See also: IRC log
Guus: PROPOSED to accept minutes of 8 May telecon:
Guus: Resolved, minutes accepted
Guus: Next telecon: May 22
Guus: Regarding a F2F meeting -- action continued []
<TomB:> ACTION: TomB to start questionnaire on date for f2f -- options are weeks of Nov 4 and Nov 11 [recorded in] [CONTINUES]
SKOS Use Cases Working Draft Document
<scribe:> ACTION: Jon to contact Ralph and arrange for publication of SKOS use cases as working draft (May 8 version) [recorded in] [DONE]
<scribe> See:
Ralph: Thanks to Jon for work on the document
Guus: I would like the editors to send messages to relevant mailing lists asking for feedback, with attention to the new document (like what was done for RDFa);
<scribe> [NEW] ACTION: Daniel to send messages to thesaurus list, semantic web interest, ... requesting feedback on the new SKOS use cases document [recorded in]
Sean: All lists that the questionnaire was sent to...
Daniel: I would like a list of the set of lists to send the message to.
Guus: The request should be sent to the original lists that were requested for use cases.
Daniel: Daniel et al. to get together and come up with composite list to send request to.
Grouping Construct Issues
<scribe> ACTION: Alistair to post links to grouping construct discussion in prep for next week [recorded in] [DONE] (Guus)
Guus: We need some discussion on next two actions: minimal fix and the alternative. The non-ordered approach is structured differently from ordered approach
Alistair: We can divide that into two smaller proposals. Under minimal fix, there is no way to specify that something is unordered explicitly; given an open world assumption, default reasoning is difficult. In the original SKOS Core Guide, there is a discussion of the two different layouts, which may be overly complicated.
Guus: In the minimal fix approach, for the collection case, I would not assume ordering; there is no notion of ordering, for example, with an intersection.
Alistair: As an application writer, if you want to find out that a collection is unordered, you have to examine a graph to see if there isn't something that indicates order. This is essentially default reasoning, which in practice may be a problem. In an open world situation, it would be better to state that a collection is ordered (or not) explicitly.
Guus: The minimal fix solution is Alistair's attempt to address the issue (just the ordering problem) in a minimal way. Another alternative would be to take this proposal as a starting point, and then extend that to provide an explicit feature.
<TomB>
Jon: This would be preferred -- to take this a step further, and provide the explicit feature enabling users to state whether or not a collection is ordered.
Alistair: Referring to the ordered SKOS membership rule -- if you have an ordered collection and member list, you can infer a number of things from queries against the list. This would enable you to ask whether something was a member of a list or not. As is, the minimal fix solution does not make this explicit - there is a level of indirection. With the rule, you can end up with a SKOS ordered collection, you can have both a SKOS memberlist property pointing to a list, and pointers to the members; You could assume if the property is not there, that the list is unordered. Given the minimal fix, we could raise these issues as distinct issues, or provide a strawman that would support fixing them in one go.
Guus: I propose we discuss this next week, and then keep the others as additional issues for the list which we can decide later to either address or drop.
It would be useful, given this, to address the specification of the semantics, and our definition of test cases. We might have to find additional people to work on these issues; Sean might be prepared to take on some of these issues given his experience with the OWL test cases. We need similar infrastructure to support some of this work; write test cases against the specification regarding what an application is expected to do based on the semantics. Sean would be willing to take this on.
<RalphS> [I'm concerned about alternatives such as "if the property is not present, assume..."; that may open non-monotonic issues]
Alistair -- would you be willing to make the minimal fix proposal for next week and raise one or two issues with respect to the potential problems, keeping the rule in, but raising an issue regarding the problems?
Alistair: With regard to test cases, what was the basis for these in OWL?
Sean: There were a number of different test cases, testing different things; test cases include the chunk of RDF and what the results should be.
<Guus> OWL Test Cases
If you look at the test cases, you can see examples of various issues, consisting of OWL ontologies and indications of how applications were expected to behave. So here, you would have to describe what the RDF criteria would be, how applications are expected to behave.
Guus: We should take the minimal fix proposal and spend a few minutes on that.
Sean/Alistair: The two examples are inconsistent because they use the SKOS narrowerThan property ... The difficulty with the structure of the proposal - used axiomatic triples, doesn't specify whether it is OWL inconsistent, RDF inconsistent, etc. Even with just an RDF interpreter, we should specify what the behavior should be.
Guus: If you look at OWL test cases, for example, these are the premises, and these are the conclusions expected. This might provide a little more formal form than what is currently in the document. For specification of semantics ... do we think we can handle it ourselves, or do we need additional assistance to work with us on this?
Alistair: We might basically have a number of sections in the semantics, structured similarly to the document currently. If we break up the semantics in that way, the namespace document would be comprised of the axiomatic triples. Then, the issues would be with some of the rules, such as the membership issue.
We might use the way the entailment rules are given informally in the RDF semantics, but I hadn't thought about other sorts of rules yet that might also be pertinent.
Guus: If we can keep this format, which would make it clear to application developers what they need to do, I'm not sure this would be sufficient.
Alistair: This structure follows from the way the RDF semantics is structured, but then if you start to use the OWL vocabulary in the axiomatic triples, then you're no longer building on the RDF semantics. By bringing in semantics from OWL, it would not be clear whether you are bringing in the RDF model-theoretic semantics from OWL or the direct model-theoretic semantics.
Daniel: I thought the goal was to keep it simple ...
Alistair: We could take two approaches, one stating the RDF semantics, the other using some OWL, but if we're using OWL then we have to be clear about how we're using the semantics.
Guus: I suggest that we are explicit about how we use a particular statement from OWL, not duplicating what is in the OWL specification. So if there is a notion of disjoint, we should use what is in OWL not recreate what is in the OWL spec, but could add notes about what it would mean to use a particular construct from OWL. For any formal definitions we should refer to the OWL specification.
Sean: I would like to think abit more about what we're proposing, but would be leery of proposing a kind of mix and match approach. If you're using the OWL vocabulary, shouldn't we be using the OWL semantics?
Guus: Sean might be in the best position to address this. OWL disjoint is a good example to look at - Sean can take a look from the position of an OWL application developer.
In section 2, axiomatic triples: the first four can be part of an RDF schema for SKOS. For the fifth one - disjoint - people have to understand something about OWL to understand how to use this.
Sean: The question is do the rest of the triples fit within the OWL semantics - if they fit in the OWL Full world, then you would have to fit within the RDF semantics (using RDF-compatible semantics for OWL). So there is a user who wants to use SKOS, if this is RDF with a little OWL thrown in, would the file be OWL compliant or RDF compliant?
Guus: We have to point out these cases where you're using SKOS within a DL environment, which may be concerned with property statements, in order to keep within the DL space ... may need to work through this.
<seanb> It's me for the testing!
<scribe>[NEW] ACTION: Sean to look at the test environment supporting the SKOS semantics [recorded in]
<scribe> [NEW] ACTION: Alistair will look at raising the examples from the issues to test cases [recorded in]
<scribe> ACTION: Antoine post link to Relationships between labels discussion in preparation for next week's call [recorded in] [DONE]. See
<scribe> ACTION: Jon and Alistair: Move SKOS issues over from Sandbox to Tracker on an ongoing basis [recorded in] [CONTINUED].
<scribe> ACTION: Guus revise his ISSUE-26 proposal to account for other options [recorded in] [CONTINUED].
<scribe> ACTION: Antoine to make a proposal about SKOS Use Case document [recorded in] [DONE]. See decision, May 8.
Issues admin: Antoine's message
<TomB> [RalphS, are the issues correctly being recorded as "done"?]
<scribe> Continued
<RalphS> scribenick: ralphs
Elisa: I have made some
progress
... I have pulled together a summary of goals and next steps
... I propose to update the wiki to reflect what I have gathered
... and to include Vit's notes
... Tom and I had discussed whether to identify people we might ask to provide input on their experiences w.r.t. best practices
... for version management, some of the things Daniel and his team have done in bio portal would make good examples
... we've not made much progress on identifying best practices here
... but we do know some folk who have articulated policies
... for URI schemes we might talk with Daniel and Chris Welty
... for maintenance policies we have good first-hand experience with SKOS vocabulary maintenance
... Alistair and others have done great work
... goal would be to identify a couple of people who could be good liaisons for each section
Tom: formulate a set of simple questions to ask each group
<dlrubin> FYI--I need to drop off the call now. Thanks everyone.
Tom: it's a big topic, so coming up with a set of questions might be a good first step
<seanb> Sorry -- have to go. Bye!
Tom: we also need to have more people working on this task
Elisa: in addition to myself, Vit
and Siggi both said they were interested in working on this
deliverable
... some of the folks involved in SKOS said they might contribute
<scribe> ACTION: Elisa to provide outline of work to be done by Apr 17 [recorded in] [CONTINUES]
Elisa: I hope to send summary by next week
[adjourned] | http://www.w3.org/2007/05/15-swd-minutes.html | CC-MAIN-2019-51 | refinedweb | 1,885 | 57.81 |
).
For example, a program to print the first 20 integers and their
powers of 2 could be written as:
main = print ([(n, 2^n) | n <- [0..19]]).)
main = interact (filter isAscii).
type FilePath = String
writeFile :: FilePath -> String -> IO ()
appendFile :: FilePath -> String -> IO ()
readFile :: FilePath -> IO String do notation allows programming in a more imperative syntactic
style. A slightly more elaborate version of the previous example
would be:
main = do
putStr "Input file: "
ifile <- getLine
putStr "Output file: "
ofile <- getLine
s <- readFile ifile
writeFile ofile (filter isAscii s)
putStr "Filtering successful\n"
The return function is used to define the result of an I/O
operation. For example, getLine is defined in terms of getChar,
using return to define the result:
getLine :: IO String
getLine = do c <- getChar
if c == '\n' then return ""
else do s <- getLine
return (c:s).
userError :: String -> IOError
Exceptions are raised and caught using the following functions:
ioError :: IOError -> IO a
catch :: IO a -> (IOError -> IO a) -> IO a
f = catch g (\e -> if IO.isEOFError e then return [] else ioError:
instance Monad IO where
...bindings for return, (>>=), (>>)
fail s = ioError (userError s)
The exceptions raised by the I/O functions in the Prelude are defined in Chapter 21. | https://www.haskell.org/onlinereport/io-13.html | CC-MAIN-2015-18 | refinedweb | 203 | 55.07 |
09 December 2010 09:47 [Source: ICIS news]
(Adds details throughout)
By Alfred Wong
SHANGHAI (ICIS)--Bayer plans to invest €1bn ($1.33bn) in expanding its facilities in Shanghai, in line with its aim to generate about €5bn in total sales from the Greater China region by 2015, the German chemical producer said on Thursday.
"The expansion of our capacities in ?xml:namespace>
"We want to increase group sales in Greater China to around €5bn by 2015. MaterialScience is expected to contribute at least half of this amount," said Dekkers.
The target represented about a 58% surge from actual sales last year at €2.1bn, 48% of which came from Bayer’s MaterialScience (BMS) business, based on the company’s statement.
BMS's CEO Patrick Thomas told ICIS as part of the expansion plans capacity of polyurethane raw material methyl di-p-phenylene isocyanate (MDI) would be increased to 1m tonnes/year from the existing 350,000 tonnes/year, while its capacity for polycarbonate (PC) would be increased to 500,000 tonnes/year from the current 200,000 tonnes/year.
"The existing MDI capacities in our Caojing facility are 350,000 tonnes/year and we are going to add 500,000 tonnes/year. With debottlenecking on the existing facilities, we will be able to make it 1m tonnes/year," he said.
He said the existing 200,000 tonnes/year PC capacity would be raised to 300,000 tonnes/year through debottlenecking, while an additional 200,000 tonnes/year would be added to make the total capacity 500,000 tonnes/year.
All new expansions were expected to come on stream by 2016, depending on market conditions, he said.
Thomas said the headquarters of the PC business unit would be relocated to
"We signed a memorandum with the
Thomas said the company’s global sales growth in the first three quarters of this year was around 30% year on year and it would be a bit less than that for the full 2010 because of the seasonal holiday factor in the fourth quarter.
"We are seeing a fast recovery from the recession and we are close to the pre-recession level," he said.
“We expected 12 months ago that full recovery would come in 2012 and it's surely happening faster."
The company's global revenue would grow at 5-10% and that of
In fiscal 2009, the Bayer group in Greater China recorded sales of €2.1bn, of which €1.2bn was accounted for by BMS.
($1 = €0.75) | http://www.icis.com/Articles/2010/12/09/9417932/bayer-to-invest-1bn-in-shanghai-eyes-5bn-china-sales.html | CC-MAIN-2014-10 | refinedweb | 418 | 58.52 |
From: Alberto Barbati (abarbati_at_[hidden])
Date: 2004-02-25 03:27:45
Eric Niebler wrote:
> Was that a vote in favor of an interval_min function, or a boost-wide
> utility? If we want a boost-wide utility (a good thing to have, IMO),
> what should it be called? boost::boost_min (kind of repetitive)? or
> perhaps boost::dependent_min to emphasize the fact that is uses Koenig
> lookup? Or just boost::min_?
Why not having both std::min and "dependent" min:
#define BOOST_EMPTY
template< class T >
inline T const & const std_min(T const &a, T const &b)
{
return std::min BOOST_EMPTY (a, b);
}
template< class T >
inline T const & dependent_min(T const &a, T const &b)
{
using std::min;
return min BOOST_EMPTY (a, b);
}
possibly adding suitable workarounds for implementation that put min in
the global namespace. I like the idea of having those as boost-wide
utilities. I think that std_min(x, y) is nicer and more descriptive to
read than (min)(x, y), but that's my personal taste. The separate name
dependent_min make it self-evident even to the causal reader that it's
something different from std::min/std_min.
Just my 0.01
Alberto Barbati
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/2004/02/61684.php | CC-MAIN-2021-25 | refinedweb | 219 | 66.23 |
Good looking, animated, easy to customize, MVVM charts for WPF, WinForms under MIT Licence
Hi all, I wanted to ask something about the scale of the axis and the dimension of the cartesian chart. Assuming I'm using WPF and a canvas to contain che entire chart (with labels and titles) inside another canvas for all the window content, I'd like to have:
Is that possible?
Thanks in advance!
Hello, is it possible to use differents mappers on the same class?
You can use
Charting.For<ExcitationValue>(mapper) so LiveChart know how to display
ExcitationValue values. But in this case, everytime a ExcitationValue value have to be display, the same mapper is used.
In my case, data are stored in a class with 1 X value and 4 Y values. I want to display a chart with 4 differents series (my 4 Y values).
It is possible to use one different mapper on each serie ?
public class ExcitationValue { public TimeSpan StartTime { get; set; } //X Value public int LR { get; set; } //Serie 1 public int MR { get; set; } //Serie 2 public int SR { get; set; } //Serie 3 public int GR { get; set; } //Serie 4 }
Tks ! | https://gitter.im/beto-rodriguez/Live-Charts?at=60d3f0908a40b1172825b672 | CC-MAIN-2021-39 | refinedweb | 195 | 62.38 |
From: John Maddock (john_at_[hidden])
Date: 2005-08-16 04:55:57
> In boost/regex/v4/regex_match.hpp, a number of the overloads (the ones
> that don't take a result parameter) are now bitwise-oring in
> regex_constants::match_any.
>
> As a result, a sequence like
>
> boost::regexp exp("a(bc)?")
> char *value = "abcbc";
> bool result = boost::regex_match(value, value + 5, exp);
>
> will now set result to true where it was previously false in 1.32. I
> fixed our code by passing in a dummy result object as an extra
> parameter.
>
> Was this change intentional? I couldn't find any documentation that
> mentions it.
It's intentional in the sense that or'ing with match_any *should never
effect whether a match is found or not*, only which or several possible
matches gets selected.
I can't reproduce your problem here, here's the test code I'm using:
#include <boost/regex.hpp>
#include <iostream>
int main()
{
boost::regex exp("a(bc)?");
const char *value = "abcbc";
bool result = boost::regex_match(value, value + 5, exp);
return result;
} | https://lists.boost.org/boost-users/2005/08/13284.php | CC-MAIN-2021-49 | refinedweb | 174 | 58.28 |
This paper was written by Richard Stallman in 1981 and delivered in the ACM Conference on Text Processing.
EMACS(1) is a real-time display editor which can be extended by the user while it is running..
A coherent set of new and redefined functions can be bound into a library so that the user can load them together conveniently. Libraries enable users to publish and share their extensions, which then become effectively part of the basic system. By this route, many people can contribute to the development of the system, for the most part without interfering with each other. This has led the EMACS system to become more powerful than any previous editor..
To help the user make effective use of the copious supply of features, EMACS provides powerful and complete interactive self-documentation facilities with which the user can find out what is available.
A sign of the success of the EMACS design is that EMACS has been requested by over a hundred sites and imitated at least ten times.
By a display editor we mean an editor in which the text being edited is normally visible on the screen and is updated automatically as the user types his commands. No explicit commands to `print' text are needed.
As compared with printing terminal editors, display editor users have much less need for paper listings, and can compose code quickly on line without writing it on paper first. Display editors are also easier to learn than printing terminal editors. This is because editing on a printing terminal requires a mental skill like that of blindfold chess; the user must keep a mental image of the text he is editing, which he cannot easily see, and calculate how each of his editing command `moves' changes it. A display editor makes this unnecessary by allowing the user to see the `board'.
Among display editors, a real-time editor is one which updates the display very frequently, usually after each one or two character command the user types. This is a matter of the input command language. Most printing terminal editors read a string of commands and process it all at once; a useful feature on a printing terminal. For example, there is usually an `insert' command which inserts a string of characters. When such editors are adapted to display terminals, they often update the display at the end of a command string; thus, the insertion would be shown all at once when it was over. It is more helpful to display each inserted character in its position in the text as soon as it has been typed.
A real-time display editor has (primarily!) short, simple commands which show their effects in the display as soon as they are typed. In EMACS, text (printing characters and formatting characters) is inserted just by typing it; there is no `insert' command. In other words, each printing character is a command to insert that character. The commands for modifying text are nonprinting characters, or begin with nonprinting characters. Many-character commands echo if typed slowly; if there is a sufficiently long pause, the command so far is echoed, and then the rest of the command is echoed as it is typed. Aside from this, EMACS acknowledges commands by displaying their effects.
EMACS is not the first real-time display editor, but it derives much appeal from being one. It is not necessary to know how to program, or how to extend EMACS, to use it successfully.
To illustrate and demonstrate the flexibility which EMACS derives from extensibility, here is a summary of many of the features, available to EMACS users without the need to program, to which extensibility has contributed. Many of them were written by users; some were written by the author, but could just as well have been written by users.
Many minor extensions can be done without any programming. These are called customizations, and are very useful even by themselves. For example, for editing a program in which comments start with `<**' and end with `**>', the user can tell the EMACS comment manipulation commands to recognize and insert those strings. This is done by setting parameters which the comment commands refer to. It is not necessary to redefine the commands themselves. Another sort of customization is rearrangement of the command set. For example, some users prefer the four basic cursor motion commands (up, down, left and right) on keys in a diamond pattern on the keyboard. It is easy to reassign the commands to these positions. It is also possible to rearrange the entire command set according to a different philosophy.
EMACS can be programmed to understand the syntax of the language being edited and provide operations particular to it. Many major modes are defined, one for each language which is understood. Each major mode has the ability to redefine any of the commands, and reset any parameters, so as to customize EMACS for that language. Files can contain special text strings that tell EMACS which major mode to use in editing them. For example, `-*-Lisp-*-' anywhere in the first nonblank line of a file says that the file should be edited in Lisp mode. The string would normally be enclosed in a comment.
For editing English text, commands have been written to move the cursor by words, sentences and paragraphs, and to delete them; to fill and justify paragraphs; and to move blocks of text to the left or to the right. Other commands convert single words or whole regions to upper or lower case. There are also commands which manipulate the command strings for text justifier programs: some insert or delete underlining commands, and others insert or delete font-change commands.
Many commands are controlled by parameters which can be used to further adapt them to particular styles of formatting. For example, the word moving and deletion commands have a syntax table that says which characters are parts of words. There are two commands to edit this table, one convenient for programs to use and an interactive one for the user. The paragraph commands can be told which strings, appearing at the beginning of a line, constitute the beginning of a paragraph. Such parameters can be set by the user, or by a specification in the file being edited. But normally they are set automatically by the major mode (that is, by telling EMACS what language the file is written in) and do not require attention from the user.
A very powerful extension facility is the ability to redefine the graphic and formatting characters as commands. These characters, which include letters, digits and punctuation, are normally all defined as commands to insert themselves into the text. Useful alternate definitions for these characters usually insert the character as usual, and then do additional processing which is in some way meaningfully associated with the insertion of that character.
The single most useful command for editing text is the `auto-fill space'. It is a program intended to be used as the definition of the space character. In addition to inserting a space, it breaks the line into two lines if it has become too long. With the space character redefined in this way, the user can type endlessly ignoring the right margin, and the text is divided into lines of a reasonable length. Of course, this feature is not always desirable. It is turned on or off by redefining the space command. If the auto-fill space did not exist, any user could write it and also the command to turn it on and off.
A bolder use of redefinition of self-inserting characters is the abbreviation facility, part of the standard EMACS system but still implemented as an extension maintained by the user who wrote it. The abbreviation facility allows the user to define abbreviations for words, and then type the abbreviations in order to insert the words. For example, if `cd' were defined as an abbreviation for `command', typing `i/o-cd' would insert `i/o-command' into the text. Abbreviation expansion preserves case, so `Cd' would expand into `Command'. Abbreviation works by redefining all punctuation characters (the list of which can be altered by customization) to run a program which looks at the preceding word and, if it is a defined abbreviation, replaces it with its expansion.
Yet another application of redefining printing characters is automatic parenthesis-matching. When this feature is in use, every time the user inserts a close-parenthesis, the cursor moves briefly to the matching open-parenthesis, then back again. Automatic matching is especially useful in editing Lisp code, but it is helpful with most other programming languages also. It is implemented by redefining the close-parenthesis character.
Extensibility is especially useful for editing programs. One might conceivably design in advance all the editing commands needed for editing English text, but each programming language has its own set of useful syntactic operations, which suggest useful editing commands. Because languages differ so much, simple customization is not in general enough to implement familiar operations for a new language. A new extension package is required.
EMACS commands have been written, for many languages, to move over or kill balanced expressions, to move to the beginning or end of a function definition, and to insert or align comments. But the most useful editing operation for programs, and the first one to be implemented for any programming language, is automatic indentation.
The structure of a program can be made clear at a glance by adjusting the indentation of each line according to its level of nesting. Most programming communities attempt to indent code properly but do it manually. Automatic indentation is used mostly by Lisp programmers.
Automatic indentation was traditionally done by a program which would read in an entire source file, rearrange the indentation, and write out a corrected source file. Such a tool has several disadvantages. For one thing, processing the entire file is likely to take a while. For another, the tool insists on imposing its own idea of proper formatting, which the user cannot override. Even after a lot of effort is put into heuristics for good indentation, users are still dissatisfied.
Automatic indentation in EMACS is done incrementally. The Tab character is redefined, as a command, to update the indentation of the current line only, based on the existing indentation of the preceding lines. The Tab command is used on lines whose nesting has changed. With it, the user can indent code properly as it is first typed in. If he does not agree with the Tab command's choice of indentation, he can override it.
Because the indentation function must understand the syntax of the programming language being edited, each language requires a separate indentation function. It is the job of the major mode for each programming language to redefine the Tab character to run an appropriate indenter. Users can always use the same command to indent, no matter what sort of program they are editing. In addition, another editing command can do indentation by calling the current definition of Tab as a subroutine. (One such function is the one which indents several consecutive lines.)
Conventions such as this are vital, in an extensible system, for enabling unrelated extensions to avoid interacting wrong; one user can write an indentation function for a new language, while another user writes new language-independent operations for requesting indentation, and the two automatically work properly together.
Languages which have support for indentation include Lisp, Pascal, PL/I, Bliss, BCPL, Muddle and TECO.
Comprehension of the user's program reaches its greatest heights for Lisp programs, because the simplicity of Lisp syntax makes intelligent editing operations easier to implement, while the complexity of other languages discourages their users from implementing similar operations for them. In fact, EMACS offers most of the same facilities as editors such as the Interlisp editor which operate on list structure, but combined with display editing. The simple syntax of Lisp, together with the powerful editing features made possible by that simple syntax, add up to a more convenient programming system than is practical with other languages. Lisp and extensible editors are made for each other, in this way. We will see below that this is not the only way.
Large programs are composed of many functions divided among many files. It is often hard to remember which file a given function is in. An EMACS extension called the TAGS package knows how to keep track of this.
The TAGS package makes use of a file called a tag table, which records each function in the program, stating what file it is defined in and at what position in the file. The tag table is made by running a special program named TAGS, which is not part of EMACS. Once the tag table is loaded into EMACS, the command Meta--Period(2) finds the definition of any function, using the information in the tag table to select the proper file and find the function in it.
The positions within the source file, remembered in the tag table, are used to find the function in the file instantly. Changing the file makes the remembered positions inaccurate. If this has happened, Meta--Period searches in both directions away from the remembered position until it finds the definition. So small inaccuracies cause only slight delays.
When many new functions have been added, or moved from one file to another, the TAGS program can reprocess the tag table into an updated one. To make this more automatic, the tag table also remembers which language each source file is written in. This information is needed for recognizing the function definitions in the file.
Interactiveness is useful in many activities aside from editing text. For example, reading and replying to mail from other users ought to be interactive. Many of these activities occasionally involve text editing: for example, editing the text of a reply. If a special editor is implemented for the purpose, it can easily be much more work to write than all the rest of the system. It is easier to write the other interactive system within the framework of an extensible editor.
EMACS has two extensions, RMAIL and BABYL, for reading mail. Commands in RMAIL and BABYL are not like EMACS commands; typical commands include `D' for `delete this message', and `R' for `reply to this message'. Editing the text of the reply is done with ordinary EMACS commands.
DIRED is used for editing a file directory. The normal editing commands, as extended, can be used to move the cursor through the directory listing. Other special commands defined only in DIRED delete, move, compare or examine the file whose name is under the cursor.
The INFO extension is designed for reading tree-structured documentation files. These files are divided textually into nodes, which contain text representing pointers to other nodes. INFO displays one node at a time, and INFO commands move from one node to another by following the pointers.
The primary components of the EMACS system are the text manipulation and I/O primitives, the interpreter, the command dispatcher, the library system, and the display processor.
The text and I/O primitives are used to operate on the text under the command of the program. The interpreter executes programs, using the primitives when called for. The command dispatcher remembers which program corresponds to each possible input character; it reads a character from the terminal and calls the associated function. The library system associates functions with their names and documentation, and allows groups of related functions to be loaded quickly together. The display processor updates the screen to match the text as changed by the text primitives; it is run whenever there is nothing else to do.
An EMACS system actually implements two different languages, the editing language and the programming language. The editing language contains the commands users use for changing text. These commands are implemented by programs written in the programming language. When we speak of the interpreter, we mean the one which implements the programming language. The editing language is implemented by the command dispatcher.
Previous attempts at programmable editors have usually attempted to mix programming constructs and editing in one language. TECO is the primary example of this sort of design. It has the advantage that once the user knows how to edit with the system, he need only learn the programming constructs to begin programming as well.
However, there are considerable disadvantages, because what is good in an editor command language is ugly, hard to read, and grossly inefficient as a programming language. A good interactive editing language is composed primarily of single character commands, with a few commands that introduce longer names for less frequently used operations. As a programming language, it is unreadable if the editor is to be customizable, the user must be able to redefine each character. This in a programming language would be intolerable!
When the programming language is the editing language, the built-in editing commands and the primitive operations they use have to be written in another language. Then the user cannot change part of the standard system slightly by making a small change to its definition; it has to be reimplemented from scratch as a macro. Since the primitives available are only the commands he uses for editing, this will often be impossible because the necessary primitives will be internal routines that the user cannot call. The primitives that an extension would like to use are not always the same as the editing operations the user wants.
The implementor of a macro processor is encouraged to ignore such deficiencies because he himself does not use the language in implementing the rest of the system. Since it is traditional, in designing a macro language, to ignore the standards of readability, power and robustness typically applied to the design of programming languages, these deficiencies are usually considerable. The original TECO is a good example of this sort of problem.
In EMACS, each language is designed for its purpose. The editing language has single-character redefinable commands. The programming language is TECO, modified and extended to be more suitable for writing well-structured and robust programs, and to provide the primitives needed by editing programs as opposed to editor users. It remains hard to read, so the descendents of EMACS generally use Lisp instead. TECO was used only for reasons of historical convenience.
More information on the requirements extensibility imposes on the system's programming language is in the next chapter.
An important part of any practical extensible system is the ability to use more than one extension at one time, and begin using an additional extension at any time. Extensions should be able to override or replace parts of the standard system, or previous extensions. In EMACS the library system is responsible for accomplishing this.
An EMACS library is a collection of function names, definitions and documentation that can be loaded into an EMACS in mid-session. Libraries are read-only and position-independent, so that they can be loaded just by incorporating them into the virtual memory of the EMACS. This allows all EMACSs using a library to share the physical memory. Each library contains its own symbol table which connects function names with definitions, and also with their documentation strings. Libraries are generated from source files in which each function definition is accompanied by its documentation; this encourages all functions to be documented.
When a function name is looked up, all the loaded libraries are searched, most recently loaded first. For the sake of uniformity, the standard EMACS functions also reside in a library, which is always the first one loaded. Therefore, any library can override or replace the definition of a standard EMACS function with a new definition, which will be used everywhere in place of the old. This, together with the fact that EMACS is constructed with explicit function calls to named subroutines at many points, makes it easy for the user to change parts of the system in a modular fashion without replacing it all.
Subroutines are normally called by their full names. The user can also call any command by name, and many commands are primarily intended to be used in that way. However, the most common editing operations need to be more easily accessible. This is the purpose of the command dispatcher, which reads one character and looks it up in the dispatch table, a vector of definitions to find the function to be called (the definition-object, not the name).
Functions residing in the dispatch table can be invoked either by the character command or by name. A function which does not appear in the dispatch table can be called only by name. The user calls functions by name by means of a single-character command (Meta--X) whose definition is to read the name of a function and call that function.
Each user has his own patterns of use. Many functions in EMACS are accessible only by name because we expect most users to use them infrequently. If a particular user uses one such command often, he can place the definition in the dispatch table using the function Set Key. The function calling conventions are designed so that almost any function definition will behave reasonably if called by the command dispatcher. If a function tries to read a string argument from its caller, then when called by the command dispatcher it will automatically prompt and read the argument from the terminal instead.(3)
Some libraries contain functions that are intended to be called with
single character commands. The library can arrange to place those
functions' definitions in the dispatch table by defining a function
called Setup. This will be called automatically when the library is
loaded, and it can redefine character commands as needed. However,
because EMACS is intended to be customized, no library can reasonably
make the assumption that a function belongs on a particular character
without allowing the user who loads the library to override that
assumption. For example, a library might wish to redefine
Control--S on the assumption that it invokes the search function,
but a user might prefer to keep his search on Control--T instead,
and he might prefer that same library to alter the definition of
Control--T when loaded by him. The author of the library cannot
anticipate the details of such idiosyncrasies, but he can provide for
them all by following a convention: in the Setup function of the library
(TAGS, say), he checks for a variable called
TAGS Setup Hook, and
if it exists, its value is called as a function instead of the usual
setting up.
The display processor is the part of EMACS which maintains on the display screen an up-to-date image of the text inside the editor. Since the size of the screen is limited, only a portion or `window' can be shown. The display processor prefers to continue to start its display at the same point in the file, so as to minimize the amount of changes necessary to the screen. However, the text where the editor's own cursor is located must appear on the screen so that the terminal's cursor can show where it is. This sometimes forces a new window position to be computed. The user can also command changes in the window position, moving the text up or down on the screen.
The EMACS display processor embodies an unusual principle which makes for much faster responses to the user: display updating has lower priority than cogitation.
Most display editors change the display after each user command. This is the simplest strategy to implement, since each command knows precisely how it has changed the text. But it is very inefficient, not just of the computer's time, but of the user's time, because it makes the user wait for the completion of display updates that have already been made obsolete by further commands waiting to be executed.
Here is an example of the problem. If the user types Carriage Return to create a new line, all the lines below that point need to be redisplayed in their new positions.
While this is still going on, if he types an additional Carriage Return to create another new line, the rest of the display update is obsolete; there is no use displaying the rest of the lines in their second positions, only to display them again in their third positions.(4)
The EMACS display processor is best understood as being a separate, lower priority process that runs in parallel with the editing process. The editing process reads keyboard input and makes changes in the text. The display process is always trying to change the screen to match the text; it keeps a record of what is on the screen, and in each cycle of operation finds one discrepancy between the editing buffer and the screen record and corrects it. After each cycle, the display process can be pre-empted by the editing process, which has higher priority. The display process can be thought of as chasing an arbitrarily moving target, the edited text, with a speed limited by the terminal baud rate.
Multiple processes are not actually used in the implementation. Instead, after each line of display output, the display processor updates its data base and polls for input.
An additional benefit of this input-before-output philosophy is that it uses less computer resources when the system is heavily loaded. When not enough computer power is available, EMACS gets behind in processing the user's input. When the first command is completed, more input is available, so no effort is put into display updating yet. By saving computer time this way, EMACS eventually catches up with the user and does its display updating all at once.
Since display updating is not necessarily done at the same time as the editing operation which necessitates it, display updating cannot be the responsibility of the editing command itself. Instead, the display update must be done by somehow comparing the hew text with the previous displayed text, or information about it. In EMACS, each editing command returns information on the range of text it has changed, but aside from that the display processor operates independently. This is good for extensibility as well: it is easier to write or change an editing command if it does not have to contain algorithms for updating the screen.
Because the TECO language is not very efficient, the display processor had to be written in assembler language to get adequate performance. This is unfortunate because extensions to the display processor could be very valuable. In later implementations of EMACS, the display processor is written in Lisp along with the editing commands, and can be extended.
Despite its syntactic obscurity, TECO is actually one of the best languages to use for implementing an extensible editor. This is because most traditional programming languages simply cannot do the job! Implementing an extensible system of any sort requires features that they intrinsically lack. Specifically, it requires a language with an interpreter and the ability for programs to access the interpreter's data structures (such as function definitions).
Adherents of non-Lisp programming languages often conceive of implementing an EMACS for their own computer system using PASCAL, PL/I, C, etc. In fact, it is simply impossible to implement an extensible system in such languages. This is because their designs and implementations are batch-oriented; a program must be compiled and then linked before it can be run. An on-line extensible system must be able to accept and then execute new code while it is running. This eliminates most popular programming languages except Lisp, APL and Snobol. At the same time, Lisp's interpreter and its ability to treat functions as data are exactly what we need.(5)
A system written in PL/I or PASCAL can be modified and recompiled, but such an extension becomes a separate version of the entire program. The user must choose, before invoking the program, which version he wants. Combining two independent extensions requires comparing and merging the source files. These obstacles usually suffice to discourage all extension.
The only way to implement an extensible system using an unsuitable language, is to write an interpreter for a suitable language and then use that one. Prime is now implementing an EMACS using a simple Lisp written in PL/I. This technique works because an editor does not require a very efficient interpreter; even the most straightforward Lisp interpreter is more efficient than the TECO interpreter which is empirically observed to be good enough. I would not regard this as implementation `in' the original language, however.
A PASCAL or PL/I implementation which uses an interpreter, and allows the user program to access the interpreter data structures sufficiently, could be used just as a Lisp implementation would be used. However, such implementations are very rare, because these languages are not designed for them. If the implementor appreciates the importance of the interpreter, and of treating functions as data, he will usually choose to implement Lisp.
It is also possible to use dynamic linking--the ability to load additional modules of compiled code during execution, and refer to subroutines therein by name--in place of an interpreter. However, dynamic linking operating systems are rarer than good Lisps, harder to implement, and not as convenient for the job. One of the few such operating systems, Multics, has an EMACS written in Lisp. SINE, the EMACS implementation on Interdata computers, uses dynamic linking to load files compiled from a language which resembles Lisp.
When a language is used for implementing extensible systems, certain control structure and data structure features become vital.
One difference between Lisp (and TECO) and most other programming languages, which is very important in writing extensible systems, is that variable names are retained at run time; they are not lost in compilation.
In typical compiled languages, variable names are meaningful only at compile time. In the compiled code, uses of one variable name become references to one location in memory, but the name itself has been discarded.
By contrast, Lisp remembers the connection between variable names and their values, so that new programs can be defined.
Global variables are essential for parameters used for customization.
EMACS has a variable named
string recognized as starting a comment in the text being edited. Its
value is supposed to be that string. This variable is used by the
comment indenting command to recognize an existing comment. The fact
that the variable name is known at run time enables the user to
Most batch languages use a lexical scope rule for variable names. Each variable can be referred to legally only within the syntactic construct which defines the variable.
Lisp and TECO use a dynamic scope rule, which means that each binding of a variable is visible in all subroutine calls to all levels, unless other bindings override. For example, after
(defun foo1 (x) (foo2)) (defun foo2 () (+ x 5))
then
(foo1 2) returns 7, because
foo2 when called within
foo1 uses
foo1's value of
x. If
foo2 is
called directly, however, it refers to the caller's value of
x,
or the global value. We say that
foo1 binds the variable
x. All subroutines called by
foo1 see the binding made by
foo1, instead of the global binding, which we say is
shadowed temporarily until
foo1 returns.
In PASCAL the analogous; program would be erroneous, because
foo2
has no lexically visible definition of
x.
Dynamic scope is useful. Consider the function
Edit Picture,
which is used to change certain editing commands slightly, temporarily,
so that they are more convenient for editing text which is arranged into
two-dimensional pictures. For example, printing characters are changed
to replace existing text instead of shoving it over to the right.
Edit Picture works by binding the values of parameter variables
dynamically, and then calling the editor as a subroutine. The editor
`exit' command causes a return to the
Edit Picture subroutine,
which returns immediately to the outer invocation of the editor. In the
process, the dynamic variable bindings are unmade.
Dynamic binding is especially useful for elements of the command dispatch table. For example, the RMAIL command for composing a reply to a message temporarily defines the character Control--Meta--Y to insert the text of the original message into the reply. The function which implements this command is always defined, but Control--Meta--Y does not call that function except while a reply is being edited. The reply command does this by dynamically binding the dispatch table entry for Control--Meta--Y and then calling the editor as a subroutine. When the recursive invocation of the editor returns, the text as edited by the user is sent as a reply.
It is not necessary for dynamic scope to be the only scope rule provided, just useful for it to be available.
Some language designers believe that dynamic binding should be avoided,
and explicit argument passing should be used instead. Imagine that
function A binds the variable
FOO, and calls the function B,
which calls the function C, and C uses the value of
FOO.
Supposedly A should pass the value as an argument to B, which should
pass it as an argument to C.
This cannot be done in an extensible system, however, because the
author of the system cannot know what all the parameters will be.
Imagine that the functions A and C are part of a user extension, while
B is part of the standard system. The variable
FOO does not exist in
the standard system; it is part of the extension. To use explicit
argument passing would require adding a new argument to B, which means
rewriting B and everything that calls B. In the most common case, B
is the editor command dispatcher loop, which is called from an awful
number of places.
What's worse, C must also be passed an additional argument. B doesn't refer to C by name (C did not exist when B was written). It probably finds a pointer to C in the command dispatch table. This means that the same call which sometimes calls C might equally well call any editor command definition. So all the editing commands must be rewritten to accept and ignore the additional argument. By now, none of the original system is left!
Suppose one file is formatted with comments starting at column 50.
Editing this file is easier if the variable
Comment Column, which
is used (by convention) to decide where to align comments, is always set
to 50 whenever this file is being editing. EMACS provides a way to
request this; but since it also provides the feature of visiting several
files at once, it must take special care to keep each file's variables
straight. Suppose one file wants
Comment Column to be 50 while
another is formatted with 40?
This is solved by allowing each file to have its own local values for any set of variables. Specially formatted text at the end of the file specifies them:
Local Modes: Comment Column:50 End:
When a file is brought into EMACS, this local modes list is parsed and the variables and values remembered in a local symbol table. While the file is not selected, its local symbol table contains the local values of the variables. While a file is selected, its local symbol table contains the global values, and the real symbol table contains the file's local values instead.
When an extensible system allows the user to provide a function to be
called on certain well-defined occasions, we call it a hook. For
example, we have already mentioned the hook which is executed whenever a
certain library is loaded; for the TAGS library, the hook is named
TAGS Setup Hook.
Another important class of hooks is executed when a major mode is
entered. Each major mode has its own hook. For example, Text mode's
hook is named
Text Mode Hook. This hook can be used to request
arbitrary actions in advance for each time text mode is entered. Many
users always define this hook to turn on Auto Fill mode, so that Auto
Fill mode is always on when Text mode is.
Hooks can be associated with variables as well. Then, each time the
value of the variable changes, its hook is run. Usually these hooks are
used to change other data structures so that they always correspond to
the value of the variable. This is often more efficient and more
modular than checking the variable itself whenever its value is
relevant. For example, changing the value of
Auto Fill Mode to
turn auto-filling on or off calls a function which automatically
redefines the Space character's command definition.
Some hooks are attached to specific points within the interpreter or display processor. For example, there is a hook which is called whenever it is time to read a character of input from the terminal. The hook program can supply the character itself. These hooks can be thought of as compensating for the fact that some parts of the system are written in assembler language and cannot simply be redefined by the user.
A system for programming editor commands needs more sophisticated facilities for handling errors and other exceptional conditions than most programming systems provide. Let us consider what an error is, and what ought to happen when there is an error.
First of all, what exactly is an error? Sometimes the user asks to do something that cannot be done (a user error). Sometimes a program asks to do something which cannot be done (a program error). Program errors often accompany user errors, but either one can happen without the other.
Program errors can be defined objectively: any event which executes a certain part of the interpreter is a program error. User errors cannot be defined objectively in this way because they are a matter of attitude toward events rather than events themselves. If a command has done nothing, we can regard this either as the response to an error or as normal functioning. And this choice of attitude has no necessary connection with whether the command definition required special code to make it do nothing in the circumstances in question.
When a program error happens, EMACS prints the error message and then gives the user the chance to invoke the error handler to debug it. If he does not do this, control returns to the innermost error return point. Programs can create error return points with a special construct. (We use a Lisp-style syntax in these examples for clarity).
(error-return (arbitrary-code-here))
The end of the error-return construct becomes an error return point which is in effect while the code inside the construct is being executed. Error returns are usually used by loops which read and execute commands of some sort, including the built-in one which reads and displays editing commands.
(do-forever (error-return (read-and-execute-one-command)))
Sometimes interpreted functions are called asynchronously or unpredictably. An example is the one which optionally saves the text every so often to reduce the amount lost if the system crashes. If this function gets a program error, it should notify the user, but should not interfere in any way with the user's explicit commands. This requires a construct known in Lisp as errset, which prevents all normal processing of errors that occur within it. An error occurring within an errset does nothing but return control immediately to the end of the errset.
The programming system does not provide any such uniform handling for user errors because the concept of a user error is not defined at that level. Instead, the designer of each editing command must decide what conditions ought to be considered errors, and what to do in each case. Sometimes the command simply does nothing. Sometimes it rings the terminal's bell and perhaps throws away type ahead. This can be best if we expect that, once the user is told that there is something wrong, it will be obvious what it is. When the cause of the error is less obvious, causing a program error deliberately with a specially chosen error message is a good way of informing him. A special primitive is used to cause a program error with an arbitrary specified error message so that the error-return processing can be invoked.
Sometimes the user error leads naturally to an error in the program, which may be all the handling it needs. This can be so if the program error's error message is an adequate explanation for the user, or if the situation is not deemed likely enough to deserve the effort required to make anything else happen.
The error handler for debugging program errors is an interpreted program itself. This is possible because primitives are provided for examining the function call stack and all other data structures which the programmer would want to examine while debugging. Users have actually written extensions and complete replacements for the standard error handler program.
Returning to the example of the user-written command loop, there has to be a command to exit the loop. How can it be done?
(do-forever (error-return (read-and-execute-one-command)))
We do it by means of a non-local control transfer. We create the transfer point by means of a catch construct around the loop. The catch creates a named transfer point at the end of the loop, which is accessible only within the loop.
(catch (do-forever (error-return (read-and-execute-one-command))) exit-my-loop)
At any time during the loop, execution of
(throw exit-my-loop)
transfers control immediately to the end of the catch, thus exiling the
loop. The catch and throw constructs were copied from Maclisp.
Like variable names, catch names have dynamic scope: the program can throw to a catch from any of the subroutines called while inside the catch. This is important because ease of extension dictates that each command which the command-reading loop understands be implemented by a separate function, so that the user can redefine one command without replacing the framework of the loop.(6)
A complex program is much easier to learn if it can answer questions about how to use it. When the program is customizable, it is important for the answers to reflect any customization that has been done. The easiest way to do this is for questions to be answered based on the same tables and data structures that control the functioning of the system. In EMACS, these include the command dispatch table and the loaded libraries.
The most basic kind of question that a user might want to ask is, "What does this command do?" He can inquire about either a function name or a command character. A library contains a documentation string for each function in it, and this is used to answer the question. When the question is about a command character, the dispatch table is used to find the function object which is currently the definition of that character. Then the library system is used to find the name of the function, and then, from that, the documentation string.
The ability to ask what a certain command does only helps users who know what commands to ask about. Other users need to ask, "What commands might help me now?" EMACS attempts to answer this by listing all the functions whose names contain a given substring. Since the function names tend to summarize what the functions do (such as `Forward Word' or `Indent for Comment') and follow systematic conventions, this is usually enough. The list also contains the first line of each function's own documentation, and how to invoke the function with one or two characters, if that is possible.
The documentation for a function is usually just a string of text, but it can also contain programs to be executed to print the documentation, interspersed with text to be printed literally. This comes in handy when the description of one function refers to another function which is usually accessed as a one or two character command. It is better to tell the user the short command, which he would actually use, than the name of the function which defines it. But exactly which command--if any--runs the function in question depends on the user's customization. What we do is to use a program, in the middle of the documentation string, which searches the dispatch table and prints the command which would invoke the desired function. Another application of this facility is for functions which simply load a library and call a function in it. The documentation string for such functions is a program to load the library and print the documentation of the function which would be called.
To help users remember how to ask these questions, we make it simple and standard. A special character, called the Help character, is used. This character is only used for asking for help, and is always available. Help is normally followed by another character which specifies the type of inquiry. If the user does not remember these characters, he can type Help again to see a list of them. To close the remaining loophole of confusion, EMACS prints a message about the Help character each time it starts up.
Help is also available in the middle of typing a command. For example, if you start to type the Replace String command and forget what arguments are required, type Help. The documentation of the Replace String function will be printed to tell you what to do next. Because questions are answered based on the data structures as they are at the moment, many changes in EMACS require no extra effort to update the documentation. It is only necessary to update the documentation of each function whose definition is changed. The format for EMACS library source files encourages this by requiring a documentation string for every function, between the function name and its definition.
I began the development of EMACS in 1974 with an improvement to TECO: the implementation of the display processor and a command dispatcher with a small fixed set of commands. These were inspired by the editor E of the Stanford Artificial Intelligence Lab. They were not considered a new editor, but rather one new feature in TECO to join many existing features. The user would give the TECO command Control-R to enter display editing mode, whose commands were suitable only for making local changes to the file. He would exit display editing mode to do anything else.
But once display editing was implemented, it was fairly easy to allow commands to be redefined to call functions written in TECO. TECO already contained considerable facilities for text manipulation, I/O, and programming, so almost immediately many users began to implement large collections of editing commands, powerful enough to do every part of editing. One of the most popular of these systems was TECMAC. Others included MACROS, RMODE, TMACS, Russ-mode and DOC. The need to exit from display editing mode to use TECO directly became less and less frequent until new users no longer learned how.
But TECO was still missing many at the important control and programming constructs which allow programs to be readable and maintainable (for example, named functions and variables!). So the early TECO-based display editors were very hard to maintain. In 1976 the TMACS system experimented with adding named functions and variables, with good results limited by the inefficiency of implementing them with TECO programs. This inspired me to implement EMACS itself.
Writing EMACS involved simultaneously adding to TECO the features which make up the library system and self-documentation, which permitted a new readable programming style, and writing a new set of display editing commands using this style. The design for the commands themselves was based on examining the command sets of the many TECO-based editors for inspiration, and choosing commands so that the most common operations would take few keystrokes. The first operational EMACS system existed in late 1976.
Since then, development has proceeded steadily, most new code being written in TECO. New features are added to TECO itself only to speed up loops such as table searching and s-expression parsing, or to make possible new kinds of I/O or interface operations.
EMACS was developed on the Digital Equipment Corporation PDP--10 computer using MIT's own Incompatible Timesharing System. By 1977, outside interest in EMACS was sufficient to motivate Mike McMahon of SRI International to adapt it to Digital's Twenex (`Tops--20') operating system. EMACS is now in use at about a hundred sites.
Several post-EMACS editor implementations have copied from EMACS both the specific command set and user interlace and the fundamental principle of being based on a programmable interpreter. The motivation for these projects was to transfer the ideas of EMACS to other computer systems. Two of them, now in use, are Multics EMACS, a Honeywell product, and ZWEI, the editor for the MIT Artificial Intelligence Lab Lisp machine.
Because EMACS supplied the implementors with a clear idea of what was to be implemented, their focus was on making the foundations clean. The essential improvement was the substitution of an excellent programming language, Lisp, for the makeshift extended TECO used in EMACS. Lisp provides the necessary language features in a framework much cleaner than TECO. Also, it is more efficient. A Lisp interpreter is intrinsically more efficient than a string-scanning interpreter such as TECO's, and Lisp compilers are also available. This efficiency is important not just for saving a few microseconds, but because it reduces the amount of the system which must be written in assembler language in order to obtain reasonable performance. This opens more of the system to user extensions. Another improvement has been in the data structure used to represent the editing buffer: Multics EMACS developed the technique of using a doubly-linked list of lines, each being a string. This technique is used in ZWEI as well.
Many other editors imitate the EMACS command set and display updating philosophy without providing extensibility. Despite that deficiency, and despite the greatly reduced set of features that results from it, these can be useful editors, though not as useful as an extensible one. For a computer with a small address space or lacking virtual memory, this is probably the best that can be done.(7)
The proliferation of such superficial facsimiles of EMACS has an unfortunate confusing effect: their users, knowing that they are using an imitation of EMACS, and never having seen EMACS itself, are led to believe that they are enjoying all the advantages of EMACS. Since any real-time display editor is a tremendous improvement over what they probably had before, they believe this readily. To prevent such confusion, we urge everyone to refer to a nonextensible imitation of EMACS as an `Ersatz EMACS'.
The conventional wisdom has it that when a program intended for multiple users is to be written, specifications should be designed in advance. It this is not done, the result will be inferior. The place to try anything new is in a research project which users will not see.
Some people know better than this, but they have been silenced.
The development of EMACS followed a path that most authorities would say is a direct route to disaster. It was the continuous deformation of TECO into something which is totally unlike TECO, from the typical user's point of view. And during the whole process, TECO and programs containing TECO were the only text editors we had on ITS.(8) Indeed, there are ways in which EMACS shows the results of not having been completely thought out in advance: such as, in being based on TECO rather than Lisp. But it is still reliable enough to be widely used and imitated. The disaster which would have been forecast has not occurred. Instead, a new and powerful way of constructing editors has been explored and shown to be good.
I believe that this is no. Each command in EMACS benefits from the experimentation by many different users customizing their editors in different ways since that time. This experimentation was possible only because a programmable display editor existed.
New implementations of EMACS can now be carefully designed, because they have the advantage of hindsight based on the original EMACS. However, the implementor must carefully restrict his careful design to the parts of the editor that are already well understood. To go beyond the original EMACS, he must experiment. But why isn't such a program of exploration doomed to be sidetracked by a blind alley, which will be unrecognized until too late? It is the extensibility, and a flexibility of mind, which solves this problem: many alleys will be tried at once, and blind alleys can be backed out of with minimal real loss.
The traditional attitude towards Lisp holds that it is useful only for esoteric amusements and Artificial Intelligence. The appearance of Multics EMACS as a Honeywell product is the death knell of this view. Now, a mainframe manufacturer is offering a system utility program written in Lisp; a program intended for heavy use by the general user community. The special properties of Lisp, which make extensibility possible, are a key feature, even though many of the users will not be programmers. Lisp has escaped from the ivory tower forever, and is a force to be reckoned with as a system programming language.
The programmable editor is an outstanding opportunity to learn to program! A beginner can see the effect of his simple program on the text he is editing; this feedback is fast and in an easily understood form. Educators have found display programming to be very suited for children experimenting with programming, for just this reason (see LOGO).
Programming editor commands has the additional advantage that a program need not be very large to be tangibly useful in editing. A first project can be very simple. One can thus slide very smoothly from using the editor to edit into learning to program with it..
The way EMACS records what remains on the screen, and compares it with what is now in the text being edited, is determined by the representation used for that text. The post-EMACS editors use better text representations that make for easier display updating algorithms.
The representation used in EMACS is a straightforward linear string of characters. A movable gap which can grow and shrink makes it unnecessary for insertion and deletion within a small region of the file to move half of the file up and down. The gap was essential in making it practical to insert characters one at a time, instead of en masse in an `insert' command, but aside from that it is made invisible at all but the lowest levels of software, so essentially the representation is just a linear string. It is the task of the display processor's auxiliary data to make sense out of the amorphous mass of text.
The lowest level of avoiding wasteful output is a checksum of the characters displayed on each line of the screen. It a screen line is about to be rewritten, the new and old checksums are compared. If they match, the rewriting is skipped. Once in every 2^36 times this will leave old incorrect text on the screen.
Higher levels of display optimization work by preserving information which is a byproduct of writing the display--namely, where in the text string the beginning of each screen line comes--and combining it with information which localizes the regions of the text string in which alteration has taken place. This allows it to restrict display update processing to a horizontal band of screen which contains all the necessary changes (often just one line). While processing the other lines on the screen would do no actual output, because of the checksums, even the time to compute the checksums is noticeable to the user as a delay. The same information can be used to decide when some lines on the screen should be moved up or down. When lines are inserted in the middle of the screen, it is much better to scroll the following lines downward (if the terminal can do this) than to rewrite them all in their new positions.
The record of where in the text string changes have taken place is maintained by requiring every command to return values saying what part of the string it has changed. It can identify a subinterval of the string which contains all the changes made, it can say that no change was made (though the cursor may have been moved), or it can say nothing, which requires the display processor to make no assumptions.
A better way, developed by Bernard Greenberg in Multics EMACS and used in ZWEI, is to represent the buffer as a doubly-linked list containing pointers to strings, one for each line. Newline characters are not actually present, but implicitly appear after each line except the last. This requires the lowest level insert, delete and search subroutines to be more complicated (for example, inserting a string cannot treat Newline characters like other characters), but this is just a finite amount of complexity; and it greatly simplifies efficient display computations. The state of the screen can be remembered in an array of pointers to the string that was displayed on each screen line. When the display is updated, one can compare the strings in the buffer with the strings in the display, both to see whether they are the same objects (the pointers are equal; EQ, in Lisp), and to see whether their contents are the same.
Multics EMACS never changes the contents of a string in the buffer. It creates new strings to replace the old ones when the text changes. Thus, the string pointers in the screen state continue to record the screen as it was.
ZWEI does change the contents of existing strings. To make sure that it does not fail to notice that the text no longer matches the screen, ZWEI maintains a `clock' which increments each time a change is made in the text. Each line records the clock tick of the last modification. Each screen line records the clock tick as of the time it was displayed. If the line in the text matches the line in the screen record, but the tick counts do not match, then the contents of the line have been changed.
Line list representations also eliminate the requirements on commands to say what they have changed. Reducing the need for the programmer to worry about how display will be done is very desirable. Another advantage is that it becomes feasible to have pointers to characters in the text which relocate when insertions or deletions are done, so that they continue to point to the same place in the text.
An EMACS sharable library contains, first of all, a symbol table which can be binary searched for the name of an object to find the object named. The symbol table points at both the names and the definitions using offsets from the beginning of the file, so that the file can be valid at any location in memory. The names and definitions are all examples of the TECO string data type, in the internal TECO format, so that the library does not need to be translated or parsed in any way when it is loaded.
The symbol table points to the documentation of functions in the library
as well as their definitions. The documentation for the function
Visit File is an object entered in the symbol table with the name
~Doc~ Visit File. There is also a string named
~Directory~ whose definition contains a list of the names of all
the objects in the file which the library wishes to advertise. This is
used for documentation purposes, not for looking up names, and it does
not contain names of auxiliary objects such as
~Doc~ V1sit File
or
~D1rectory~.
It is possible to search the symbol table in reverse, to take a
definition and find its name. Since one can tell which library an
object is in by comparing its address with the range of memory occupied
by the library, this makes it possible to find the name of any object
which has one. The ability to do this is important, because when the
user asks what the character Control-K does, it is desirable to be
able to tell him that it runs the function
Kill Line. The names
themselves are not kept in the dispatch table because looking up a name
in the loaded libraries is slow. For other implementations, that is a
reasonable strategy.
EMACS is available for distribution to sites running the Digital Equipment Corporation Twenex (`Tops-20') operating system. It is distributed on a basis of communal sharing, which means that all improvements must be given back to me to be incorporated and distributed. Those who are interested should contact me. Further information about how EMACS works is available in the same way.
A complete manual for use (but not extension) of EMACS is
Various lower level implementation strategies for parts of an EMACS-like editor are treated in
These include the true extensible descendents of EMACS, and the editors which preceded EMACS and supplied some of the ideas for it. The many ersatz EMACS editors are not included.
EMACS stood for Editing Macros, before we realized that EMACS is composed of functions written in a programming language rather than macros in the editor TECO.
Meta is the name of a shift key on the ideal EMACS terminal. On terminals which do not have this key, the ASCII character Escape is used as a prefix instead.
The process of reading the argument from the terminal is implemented by a function which the user can replace.
This particular sequence of events poses no problem on terminals which can move text up and down on the screen. But the same problem can still result from other events.
It is o.k. to use a Lisp compiler, if there is one. What counts is not using the interpreter all the time, but having it available all the time.
Normally the command
reading loop uses the name of the command to compute the name of the
function to call. For example, if RMAIL reads the letter N as a
command, it calls the function
# RMAIL N. This way the user can
easily define new commands.
The standard EMACS system is bigger than the entire 64k-byte address space of the PDP--11, despite constant strenuous efforts to reduce its size. And TECO is equally large. The post-EMACS editors are even larger.
The Incompatible Timesharing System.
This document was generated on 11 Febuary 1998 using the texi2html translator version 1.51a. | http://www.gnu.org/software/emacs//emacs-paper.html | crawl-003 | refinedweb | 10,551 | 51.58 |
How to Convert Int to Char Array in C++
- Use
std::sprintfFunction to Convert
intto
char*
- Combine
to_string()and
c_str()Methods to Convert
intto
char*
- Use
std::stringstreamClass Methods for Conversion
- Use
std::to_charsFunction to Convert
intto
char*
This article will explain how to convert
int to a
char array (
char*) using different methods.
In the following examples, we assume to store the output of conversion in-memory buffer, and for verification purposes, we’re going to output result with
std::printf.
Use
std::sprintf Function to Convert
int to
char*
First, we need to allocate space to store a single
int variable that we’re going to convert in a
char buffer. Note that the following example is defining the maximum length
MAX_DIGITS for integer data. To calculate the char buffer length, we add
sizeof(char) because the
sprintf function writes char string terminating
\0 byte automatically at the destination. Thus we should mind allocating enough space for this buffer.
#include <iostream> #define MAX_DIGITS 10 int main() { int number = 1234; char num_char[MAX_DIGITS + sizeof(char)]; std::sprintf(num_char, "%d", number); std::printf("num_char: %s \n", num_char); return 0; }
Output:
num_char: 1234
Note that calling
sprintf with overlapping source and destination buffers (e.g.
sprintf(buf, "%s some text to add", buf)) is not recommended as it has undefined behavior and will produce incorrect results depending on the compiler.
Combine
to_string() and
c_str() Methods to Convert
int to
char*
This version utilizes
std::string class methods to do the conversion, making it a far safer version than dealing with
sprintf as shown in the previous example.
#include <iostream> int main() { int number = 1234; std::string tmp = std::to_string(number); char const *num_char = tmp.c_str(); printf("num_char: %s \n", num_char); return 0; }
Use
std::stringstream Class Methods for Conversion
This method is implemented using the
std::stringstream class. Namely, we create a temporary string-based stream where store
int data, then return string object by the
str method and finally call
c_str to do the conversion.
#include <iostream> #include <sstream> int main() { int number = 1234; std::stringstream tmp; tmp << number; char const *num_char = tmp.str().c_str(); printf("num_char: %s \n", num_char);; return 0; }
Use
std::to_chars Function to Convert
int to
char*
This version is a pure C++ style function added in C++17 and defined in header
<charconv>. On the plus side, this method offers operations on ranges, which might be the most flexible solution in specific scenarios.
#include <iostream> #include <charconv> #define MAX_DIGITS 10 int main() { int number = 1234; char num_char[MAX_DIGITS + sizeof(char)]; std::to_chars(num_char, num_char + MAX_DIGITS, number); std::printf("num_char: %s \n", num_char); return 0; } | https://www.delftstack.com/howto/cpp/how-to-convert-int-to-char-array-in-cpp/ | CC-MAIN-2020-45 | refinedweb | 439 | 54.66 |
Hi, all, I am a new user of st2.
thanks for reading my questions:
(I'm using ST2 on OS X Mountain Lion.)
1. Is there any way to view all currently available tab triggers? (as I can see in textmate's toolbar menu of Bundles...) or is there any plan to add such a menu?
2. I can see many textmate bundle files, in the ~/Library/Application Support Sublime Text 2/Packages/ directory, such as html/HTML.tmLanguage, or some file ending with .tmPreferences... but how can I make use of these files?
3. In Textmate, when I edit html files, I can use supper + b to wrap text with <strong></strong>, super + i to wrap with <em></em>, how to do so (other keybinds are ok.) in ST2?
4. When I edit a rails view template file (.html.eb), syntax scope chosen as HTML(Rails), "if + tab" gives me php code: <?php if (condition): ?><?php endif ?>, why?
thanks! | http://www.sublimetext.com/forum/viewtopic.php?p=37903 | CC-MAIN-2015-32 | refinedweb | 160 | 84.17 |
The definitive testing tool for Python. Born under the banner of Behavior Driven Development.
Project description
mamba: the definitive test runner for Python
mamba is the definitive test runner for Python. Born under the banner of behavior-driven development.
Install
I recommend to use pipenv for managing your dependencies, thus you can install mamba like any other Python package.
By example:
$ pipenv install mamba
But you also can use pip:
$ pip install mamba
Getting Started
Write a very simple example that describes your code behaviour:
# tennis_spec.py from mamba import description, context, it from expects import expect, equal with description('Tennis') as self: with it('starts with 0 - 0 score'): rafa_nadal = "Rafa Nadal" roger_federer = "Roger Federer" game = Game(rafa_nadal, roger_federer) expect(game.score()).to(equal((0, 0)))
Run the example, and don't forget to watch it fail!
$ pipenv run mamba tennis_spec.py F 1 examples failed of 1 ran in 0.0023 seconds Failures: 1) Tennis it starts with 0 - 0 score Failure/Error: tennis_spec.py game = Game(rafa_nadal, roger_federer) NameError: global name 'Game' is not defined File "tennis_spec.py", line 8, in 00000001__it starts with 0 - 0 score-- game = Game(rafa_nadal, roger_federer)
Now write as little code for making it pass.
# tennis_spec.py from mamba import description, context, it from expects import expect, equal import tennis with description('Tennis') as self: with it('starts with 0 - 0 score'): rafa_nadal = "Rafa Nadal" roger_federer = "Roger Federer" game = tennis.Game(rafa_nadal, roger_federer) expect(game.score()).to(equal((0, 0)))
# tennis.py class Game(object): def __init__(self, player1, player2): pass def score(self): return (0, 0)
Run the spec file and enjoy that all tests are green!
$ pipenv run mamba tennis_spec.py . 1 examples ran in 0.0022 seconds
Settings
Mamba provides a way to configuration using
spec/spec_helper.py or
specs/spec_helper.py
This module function is read after parsing arguments so configure function overrides settings
A sample config file :
def configure(settings): # settings.slow_test_threshold = 0.075 # settings.enable_code_coverage = False # settings.code_coverage_file = '.coverage' settings.format = 'documentation' # settings.no_color = False # settings.tags = None
Official Manual
You can read more features about mamba in its official manual
Contributors
Here's a list of all the people who have contributed.
I'm really grateful to each and every of them!
If you want to be one of them, fork repository and send a pull request.
Project details
Release history Release notifications | RSS feed
Download files
Download the file for your platform. If you're not sure which to choose, learn more about installing packages. | https://pypi.org/project/mamba/ | CC-MAIN-2022-27 | refinedweb | 421 | 50.43 |
Operator Overloading
Operator Overloading
(Ref. Lippman 15.1-15.7, 15.9)
We have already seen how functions can be overloaded in C++. We can also overload operators, such as the + operator, for classes that we write. Note that operators for built-in types may not be created or modified. A complete list of overloadable operators can be found in Lippman, Table 15.1.
A Complex Number Class
In this example, we have overloaded the following operators: +, *, >, =, (), [] and the cast operator.
operator+() and operator*()
Let a and b be of type Complex. The + operator in the expression a+b, can be interpreted as
a.operator+(b)
where operator+() is a member function of class Complex. We then have to write this function so that it adds the real and imaginary parts of a and b and returns the result as a new Complex object. Note that the function returns by value, since it has to create a temporary object for the result of the addition.
Our implementation will also work for an expression like a+b+c. In this case, the operator will be invoked in the following order
(a.operator+(b)).operator+(c)
The member operator+() will also work for an expression like
a + 7.0
because we have a constructor that can create a Complex from a single double. However, the expression
7.0 + a
will not work, because operator+() is a member of class Complex, and not the built-in double type.
To solve this problem, we can make the operator a global function, as we have done with operator*(). The expression 7.0 * a will be interpreted as
operator*(7.0, a)
Since a global function does not automatically have access to the private data of class Complex, we can grant special access to operator*() by making it a friend function of class Complex. In general, friend functions and classes should be used sparingly, since they are a violation of the rule of encapsulation.
operator>()
We have overloaded this operator to allow comparison of two Complex numbers, based on their magnitudes.
operator=()
The = operator is designed to work with statements like
a = b;
a = b = c;
These statements respectively interpreted as
a.operator=(b);
a.operator=(b.operator=(c));
In this case, the operator changes the object that invokes it, and it returns a reference to this object so that the second statement will work. The keyword this gives us a pointer to the current object within the class definition.
operator Point()
This operator allows us to convert a Complex object to a Point object. It can be used in an explicit cast, like
Complex a;
Point p;
p = (Point)a;
but it could also be invoked implicitly, as in
p = a;
Hence, a great deal of caution should be used when providing user-defined type conversions in this way. An alternative way to convert from a Complex to a Point is to give the Point class a constructor that takes a Complex as an argument. However, we might not have access to the source code for the Point class, if it were written by someone else.
Note that overloaded cast operators do not have a return type.
operator()()
This is the function call operator. It is invoked by a Complex object a as
a()
Here we have overloaded operator()() to return true if the object has an imaginary part and false otherwise.
operator[]()
The overloaded subscript operator is useful if we wish to access fields of the object like array elements. In our example, we have made a[0] refer to the real part and a[1] refer to the imaginary part of the object.
operator<<()
The output operator cannot be overloaded as a member function because we do not have access to the ostream class to which the predefined object cout belongs. Instead, operator<<() is overloaded as a global function. We must return a reference to the ostream class so that the output operator can be concatenated. For example,
cout << a << b;
will be invoked as
operator<<((operator<<(cout, a),b)
complex.h
// Interface for class Complex.
#ifndef _COMPLEX_H_
#define _COMPLEX_H_
#include <iostream.h>
#include "point.h"
#ifndef DEBUG_PRINT
#ifdef _DEBUG
#define DEBUG_PRINT(str) cout << str << endl;
#else
#define DEBUG_PRINT(str)
#endif
#endif
class Complex {
private:
double mdReal;
double mdImag;
public:
// This combines three constructors in one. Here we have used an initialization list to initialize
// the private data, instead of using assignment statements in the body of the constructor.
Complex(double dReal=0.0, double dImag=0.0) : mdReal(dReal), mdImag(dImag) {
DEBUG_PRINT("In Complex::Complex(double dReal, double dImag)")
}
// The copy constructor.
Complex(const Complex& c);
~Complex() {
DEBUG_PRINT("In Complex::~Complex()")
}
void print();
// Overloaded member operators.
Complex operator+(const Complex& c) const; // Overloaded + operator.
int operator>(const Complex& c) const; // Overloaded > operator.
Complex& operator=(const Complex& c); // Overloaded = operator.
operator Point() const; // Overloaded cast-to-Point operator.
bool operator()(void) const; // Overloaded function call operator.
double& operator[](int i); // Overloaded subscript operator.
// Overloaded global operators. We make these operators friends of class
// Complex, so that they will have direct access to the private data.
friend ostream& operator<<(ostream& os, const Complex& c); // Overloaded output operator.
friend Complex operator*(const Complex& c, const Complex& d); // Overloaded * operator.
};
#endif // _COMPLEX_H_
complex.C
// Implementation for class Complex.
#include "complex.h"
#include <stdlib.h>
// Definition of copy constructor.
Complex::Complex(const Complex& c) {
DEBUG_PRINT("In Complex::Complex(const Complex& c)")
mdReal = c.mdReal;
mdImag = c.mdImag;
}
// Definition of overloaded + operator.
Complex Complex::operator+(const Complex& c) const {
DEBUG_PRINT("In Complex Complex::operator+(const Complex& c) const")
return Complex(mdReal + c.mdReal, mdImag + c.mdImag);
}
// Definition of overloaded > operator.
int Complex::operator>(const Complex& c) const {
double sqr1 = mdReal * mdReal + mdImag * mdImag;
double sqr2 = c.mdReal * c.mdReal + c.mdImag * c.mdImag;
DEBUG_PRINT("In int Complex::operator>(const Complex& c) const")
return (sqr1 > sqr2);
}
// Definition of overloaded assignment operator.
Complex& Complex::operator=(const Complex& c) {
DEBUG_PRINT("In Complex& Complex::operator=(const Complex& c)")
mdReal = c.mdReal;
mdImag = c.mdImag;
return *this;
}
// Definition of overloaded cast-to-Point operator. This converts a Complex object to a Point object.
Complex::operator Point() const {
float fX, fY;
DEBUG_PRINT("In Complex::operator Point() const")
// Our Point class uses floats instead of doubles. In this case, we make a conscious decision
// to accept a loss in precision by converting the doubles to floats. Be careful when doing this!
fX = (float)mdReal;
fY = (float)mdImag;
return Point(fX, fY);
}
// Definition of overloaded function call operator. We have defined this operator to allow us to test
// whether a number is complex or real.
bool Complex::operator()(void) const {
DEBUG_PRINT("In bool Complex::operator()(void) const")
if (mdImag == 0.0)
return false; // Number is real.
else
return true; // Number is complex.
}
// Definition of overloaded subscript operator. We have defined this operator to allow access to
// the real and imaginary parts of the object.
double& Complex::operator[](int i) {
DEBUG_PRINT("In double& Complex::operator[](int)")
switch(i) {
case 0:
return mdReal;
case 1:
return mdImag;
default:
cerr << "Index out of bounds" << endl;
exit(0); // A function in the C standard library.
}
}
// Definition of a print function.
void Complex::print() {
cout << mdReal << " + j" << mdImag << endl;
}
// Definition of overloaded output operator. Note that this is a global function. We can
// access the private data of the Complex object c because the operator is a friend function.
ostream& operator<<(ostream& os, const Complex& c) {
DEBUG_PRINT("In ostream& operator<<(ostream&, const Complex&)")
cout << c.mdReal << " + j" << c.mdImag;
return os;
}
// Definition of overloaded * operator. By making this operator a global function, we can
// handle statements such as a = 7 * b, where a and b are Complex objects.
Complex operator*(const Complex& c, const Complex& d) {
DEBUG_PRINT("In Complex operator*(const Complex& c, const Complex& d)")
double dReal = c.mdReal*d.mdReal - c.mdImag*d.mdImag;
double dImag = c.mdReal*d.mdImag + c.mdImag*d.mdReal;
return Complex(dReal, dImag);
}
complex_test.C
#include "complex.h"
void main() {
Complex a;
Complex b;
Complex *c;
Complex d;
// Use of constructors and the overloaded operator=().
a = (Complex)2.0; // Same as a = Complex(2.0);
b = Complex(3.0, 4.0);
c = new Complex(5.0, 6.0);
// Use of the overloaded operator+().
d = a + b; // Same as d = a.operator+(b);
d.print();
d = a + b + *c; // Same as d = (a.operator+(b)).operator+(*c);
d.print();
// Use of the overloaded operator>().
if (b > a)
cout << "b > a" << endl;
else
cout << "b <= a" << endl;
// Use of cast-to-Point operator. This will convert a Complex object to a Point object.
// An alternative way to handle the type conversion is to give the Point class a constructor
// that takes a Complex object as an argument.
Point p;
p = (Point)b;
p.print();
// Use of the overloaded operator()().
if (a() == true)
cout << "a is a complex number" << endl;
else
cout << "a is a real number" << endl;
// Use of the overloaded operator[](). This will change the imaginary part of a.
a[1] = 8.0;
a.print();
// Use of the overloaded global operator<<().
cout << "a = " << a << endl;
// User of the overloaded global operator*(). The double literal constant will be passed as the
// first argument to operator*() and it will be converted to a Complex object using the Complex
// constructor. This statement would not be legal if the operator were a member function.
d = 7.0 * b;
cout << "d = " << d << endl;
} | http://ocw.mit.edu/courses/civil-and-environmental-engineering/1-124j-foundations-of-software-engineering-fall-2000/lecture-notes/operator_overloading/ | crawl-003 | refinedweb | 1,563 | 50.84 |
Forums Gen
I’m trying to figure out how the data object handles its storage, and I wasn’t able to find answers to my questions in the forums or documentation. You don’t seem to be able to save a copy of what’s in it to disk and recall it later. The second you stop sending it an index and a value, it clears its contents of all other values, correct? This would be unfortunate if this was true, because one thing I want to use it for is to free up computing resources by saving results of computations, and just looking those up, instead of having to compute them every time. But if I have to do the computation just to keep the data in there, that kind of defeats the purpose.. This is at least what I observed. Is this the intended functionality, or am I doing something wrong?
Clarification:?
I would assume it has to do with the fact that the Gen patch is recompiled whenever you edit it.
A logical assumption. Still, what would be the danger in NOT clearing the data object on recompilation?
yeah, this is a recompilation thing i guess. with ‘auto-compile’ switched off, it does not happen of course. the gen~ patch is an object, and changes mean recompilation, so after a change, it is effectively a new object. the data exists in the object and is 64-bit if using the [data] object. however, if reading an external msp buffer into a gen~ [data] or [buffer] object, this is correctly replaced inside gen~ after a recompile (this used to be a bug that it did not, but now it all works). most probably a pointer to it is held in memory and then reinstantiated. i guess it is because your data exists only inside the specific gen~ namespace that it resets (clears) itself on recompile.
regarding decimal places in max/msp land – max is a 32-bit application and thus can only display up to 6 points of accuracy. i agree that it is funny that this means that it cannot display correctly from the 64-bit gen~ world. i guess global 64-bit max is around the corner at some point…
p.s. – these are all opinions, not knowledge. i could be wrong and hope that someone more knowledgable jumps in
Hi there,
Yes, gen~ currently does all processing all the time, so there’s no real way to cache computations as such. However, there’s a pretty nice feature coming soon that will allow conditional processing, which will help a lot in these situations.
And yes, since data is local to the gen~ patcher, unlike buffer~ which is global to the containing Max patcher, it gets cleared each time the patcher is recompiled (i.e. at each edit, if auto-compile is on). I admit it would be nice if this could be preserved between edits. It has been logged as a feature request (#2963), however at such a point that buffer~ stores its data in 64 bits of depth, this won’t be as much of an issue I guess…
Graham
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Computer Science Archive: Questions from December 12, 2009
- maxmax askedIn an array called ELF with 4 rows and 9 columns, write the line of code, using an assignment... More »1 answer
- maxmax askedWrite a program that reads 20 data values from a datafile to fill a one dimensional array with 20 st... Show moreWrite a program that reads 20 data values from a datafile to fill a one dimensional array with 20 storagelocations. Assume the name of the array is DATA and the nameof the data file is VALUES.cpp. Also, assume the data in thefile is in one long column. Finally, the program shouldincrement each of these values by 5 and then write these new valuesto a data file called ANSWERS.cpp.test can be made using a data file with number1 to 20 storedin there• Show less3 answers
- maxmax askedWrite a program that allows the user to enter 5 numbers in themain part of the program. It then send... Show more
Write a program that allows the user to enter 5 numbers in themain part of the program. It then sends these 5 values to afunction called SUM. This function adds all five numberstogether and returns this sum to MAIN. Finally, in MAIN,calculate the average and output both the sum and the average.
Test your program using these 5 numbers: 46,55, 86, 62, 58• Show less2 answers
- Anonymous askedWrite a small record management application for a school. Tasks will be Add Record, Edit Record, De... More »1 answer
- Anonymous askedfor i... Show moreHow do we know if a function would linear or quadratic inpython.
For example,
def silly1(L):
for i in range(len(L)):
print L[i]
for i in range(len(L) - 1, 0, -1):
print (b) [2 marks]
def silly2(L):
for i in range(300):
for j inrange(len(L)):
L[j] = L (c) [2 marks]
def silly3(L):
for i in range(len(L)):
for j inrange(len(L)):
print L[i], L[j].
The solution is supposed to be linear, linear, quadratic, but Idon't know how we are supposed to determine that right away.
Any help is appreciated. Thanks!
• Show less0 answers
- Anonymous asked1 answer
- Anonymous asked#includ... Show moreI started with my project and I need helpwith ithere all the code I did:#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
struct NODE
{
struct NODE *link;
int value;
};typedef struct NODE Node;/* NEW: count the number of times thetarget occurs in the list */
int countTarget( Node *p, int target)
{
int count = 0;
while ( p )
{
if ( p->value == target ) count++ ;
p = p->link;
}
return count ;
}/* NEW: (skip this) Delete the first nodeof the linked list */
deleteFirst( Node **head )
{/* If list is empty, do nothing */
if ( *head == NULL ) return;/* Otherwise, point head to the successorof the first node */
/* (For a one-node list, this will be NULL) */
Node *first = *head;
*head = first->link;/* Delete former first node */
free ( first );
}/* Insert a node containing val at thehead of the linked list */
Node *insertFirst( Node **head, int val )
{
Node *node = (Node *)malloc( sizeof( Node ) );/* Return NULL if memory allocationfailed */
if ( !node ) return NULL;
node->value = val;
node->link = *head;
*head = node;
return node;
}/* NEW: increment the value in each nodeby amount
|
*/
void incrementEach( Node *head, int amount)
{
while ( head )
{
head->value += amount;
head = head->link;
}
}
void traverse( Node *p )
{
while ( p != NULL )
{
printf("%3d ", p->value );
p = p->link;
}
}
void freeList( Node *p )
{
Node *temp ;
while ( p != NULL )
{
temp = p;
p = p->link;
free( temp );
}
}
int main()
{
Node *headA = NULL;
int j;/* Create a List for testing */
int testNumsA[] = { 2, 1, 4, 6, 7, 9, 7, 2, 7, -3, 0, 7};
for ( j=0; j< sizeof(testNumsA)/sizeof(int); j++ )
insertFirst( &headA, testNumsA[ j ] ) ;/* Test countTarget */
printf("Should be 4: number of 7s in list: %d\n", countTarget(headA, 7 ) );
printf("Should be 1: number of 9s in list: %d\n", countTarget(headA, 9 ) );
printf("Should be 0: number of 13s in list: %d\n", countTarget(headA, 13 ) );/* Test incrementEach */
printf("\n\nBefore increment by one:\n");
traverse( headA );
incrementEach( headA, 1 );
printf("\nAfter increment by one:\n");
traverse( headA );
freeList( headA );
getchar();
return 1;
}and I want to do two things:
1. Modify the struct so thatit includes a link to the next node (a pointer tothe
next stuct in a linkedlist.)
2.Add aninsertFirst() function and a freeList() function. Modify the restof the code so that it
works as before, but uses a linked listimplementation of the database.
The main() should write out clearprompts.
Thank you1 answer
- Anonymous asked200806 You... Show more• Show less
class Roaster
200701 Omar
200702 Mahmoud
200703 Jasem
200704 Walid
200805 Ibrahim
200806 Yousif
200809 Mohannad
200905 Hamad1 answer
- foreverdeployed askedThe function name is its operator, and the parentheses... Show moreWhich one best explains the function call?A)
B)
C)
D)3 answers
- Anonymous askedThe policy of your organization is that every employee shall begiven a 10% increment to his/her sala... Show more
The policy of your organization is that every employee shall begiven a 10% increment to his/her salary till the salary becomesequal to or greater than 15000 AED. Write a program that allows youto enter the initial salary of an individual. The program shouldprint the yearly salary of the employee till it becomes greaterthan or equal to 15000. Moreover it should also print the number ofyears in which this salary is obtained.• Show less3 answers
- Anonymous askedWrite a program that allows a teacher to enter the marks of thestudents in a class test. The program... Show more
Write a program that allows a teacher to enter the marks of thestudents in a class test. The program should print out the averagemarks, the minimum marks and the maximum marks obtained by thestudents• Show less2 answers
- Anonymous askedWhen the user chooses 3, the prog... Show more
Part 3 for book mark.3. Appen Students to theClass Roaster File.
When the user chooses 3, the program should perform thefollowing tasks:
a. Prompt the user to enterthe name of the class roaster file.
b. Open the class roaster file inappend mode so that not to destroy the file.
c. Prompt the user to enterthe student ID and student name for every student to be added andwrite them to the class roaster file. Keep looping until a (-1)
Sentinel is entered.
Sample output of choice 3
• Show less1 answer
- Anonymous asked1 answer
- Anonymous askedcomponent is clicked. The eventhand... Show moreDesign an event handler that will execute when theshowNameButton component is clicked. The eventhandler should perform the following:-store the first name in a label component namedfirstNameLabel-store the middle name in a label component namedmiddleNameLabel-store your last name in a label component namedlastNameLabel• Show less(remember to store a value in a label component, you muststore the value in the components text property)1 answer
- Anonymous askedcomponent is clicked. th... Show moredesign an event handler that will execute when thecalcAvailableCreditButton component is clicked. theevent handler should perform the following:-declare the following real variables: maxCredit, usedCredit, and availableCredit-get a value from a text box named maxCreditTextBoxand assign it to the maxCredit variable-get a value from a text box named usedCreditTextBoxand assign it to the usedCredit variable-subtract the value in usedCredit frommaxCredit and assign the result toavailableCredit• Show less-store the value in the availableCredit variable in alabel component named availableCreditLabel1 answer
- Anonymous askedWhen I hit return here after entering the students answers itdoesn't run. When I hit enter twice it... Show moreWhen I hit return here after entering the students answers itdoesn't run. When I hit enter twice it takes thats as the studentsscores! what did I do wrong?
#include<iostream>
using namespace std;
int main()
{char answers[]="TFFTFFTTTTFFTFTFTFTT";
char studanswer[21];
int question,score,ID,grade;
score=0;
cout<<"Please enter the student's ID number\n";
cin>>ID;
cout<<"Please enter the student's answers\n";
cin.ignore(10,'\n');
cin.getline(studanswer,21);
for (question=0;question<20;question++)
{if (answers[question]==studanswer[question])
score=score+2;
else
if(studanswer[question]!=' ')
score=score--;
}
cout<<"student number "<<ID<<" Has scored a"<<score;
switch((int)score/4)
{case 10:
case 9:cout<<"The student's grade is an A";
case 8:cout<<"The student's grade is a B";
case 7:cout<<"The student's grade is a C";
case 6:cout<<"The student's grade is a D";
default :cout<<"The student's grade is a F";}
system ("pause");
return 0;} • Show less1 answer
- booboo123 asked+operator=(cost queueTyp... Show more-maxQueueSize: int
-count: int
-queueFront: int
-queueRear: int
-*list: Type
+operator=(cost queueType<Type>&): constqueueType<Type>&
+initializeQueue( ): void
+destroyQueue( ): void
+isEmptyQueue( ): bool
+isFullQueue( ): bool
+addQueue(const Type&): void
+front( ): Type
+back( ): Type
+deleteQueue( ): void
+queueType(int = 100)
+queueType(const queueType<Type>&)
+-queueType( )
Which of the following members in the UML diagram keeps track ofthe number of elements in a queue at a given point in time?
a) maxQueueSize b) isFullQueue
c)count d) num
Which of the following members in the UML diagram removes anelement from the front of the queue?
a) destroyQueue b) front
c) deleteQueue d)removeQueue
Which of the following members in the UML diagram adds an elementto the front of the queue?
a)front b)addQueue
c)back d) None of the above
• Show less2 answers
- booboo123 asked
Code Sequence I:
newNode->link = q;
p->link = newNode;
Code Sequence II:
p->link = newNode;
newNode->... Show more
Code Sequence I:
newNode->link = q;
p->link = newNode;
Code Sequence II:
p->link = newNode;
newNode->link = q;
If code sequence I or II is followed which of the following MUST bepresent?
a. p b. q
c. node with value 76 d. p and q
• Show less1 answer
- booboo123 asked
Code Sequence I:
newNode->link = q;
p->link = newNode;
Code Sequence II:
p->link = newNode;
newNode->... Show more
Code Sequence I:
newNode->link = q;
p->link = newNode;
Code Sequence II:
p->link = newNode;
newNode->link = q;
Refer to the figure above. When inserting an item into a linkedlist, having to pointers prevents having to pay attention to whichof the following?
a. contents of the newnode b. address of the new node
c. the sequence ofoperations d. deletion of the head node
• Show less1 answer
- Anonymous askedThis solution is not the correct answer to the problem. It does not display the employee ids a... More »1 answer
- Romulas askedCan someone explain how backtracking can be used to yield all thepermutations of a given set? For in... Show moreCan someone explain how backtracking can be used to yield all thepermutations of a given set? For instance, if I had {1,2,3} I wouldwant the following:
{1,2,3}
{1,3,2}
{3,1,2}
{3,2,1}
{2,1,3}
{2,3,1}
There are n! permutations.
I don't want any code, just an explanation of how backtrackingworks. Please don't provide any code - I want to figure that partout on my own. I just need to understand backtracking better.
• Show less1 answer
- PurpleBoss2388 askedWri... Show more
struct node {
int key; struct node *next;
};
typedef struct node NODE;
typedef struct node *PTR;
Write a C function delete_last_occurwith thefollowing header:
void delete_last_occur (PTR *h, int j)
The parameter *h points to a listcontaining nodes of type NODE. When the list isnonempty, several
nodes in the list may have the same value forthe key field. The function should do the following.If
the list contains one or more nodes whose key values areequal to that of the parameter j, thefunction
should delete last node with key valueequal to that of j. If the list does not containany node with
keyvalue equal to that of j, the function should returnwithout modifying the list.• Show less3 answers
- PurpleBoss2388 askedstored in... Show more
In a MAL program, a two-dimensional arrayTable of type integer with 7 rows and 7 columnsis
stored in column majororder. Theaddress of the element Table[6][1]is 252(decimal). Find
thestarting address of the array. Your answer must be indecimal.• Show less1 answer
- booboo123 asked1a)The overhead associated with iterative functions is greater interms of bot... Show moreRecursion True or False
1a)The overhead associated with iterative functions is greater interms of both memory space and computer time, when compared to theoverhead associated with executing recursive functions
1b)There are two base cases in the recursive implementation ofgenerating a Fibonacci sequence
• Show less1 answer
- PurpleBoss2388 askedoriginal... Show more
For certain binary integers other thanzero, when we take the 2’s complement, we get backthe
originalinteger itself. Give an example of such an integer and explain whythis happens.• Show less1 answer
- booboo123 askedc. #i... Show moreFor stack container class;
a) which must be included?
a. #include <stack> b.use stack std;
c. #include <stl stack> d. using namespacestack;
b) which is an operation provided by stack container class?
a. push(item) b. pop(item)
c. pushItem d.delete(item)
• Show less1 answer
- Anonymous askedtest plan... Show morecan anyone please provide me an abbreviated version of asystem test plan for any softwaretest plan need not to betoo long i just want to have an rough idea how a test plan lookslike. I just want to practice the ability to use andarticulate a standard (i.e., template) IEEE 829 1998waiting for yourreplies• Show less1 answer
- booboo123 askedint rFibNum(int a, int b, int n)
{
if(n == 1)
return a;
else if( n == 2)
... Show moreint rFibNum(int a, int b, int n)
{
if(n == 1)
return a;
else if( n == 2)
return b;
else
return rFibNum(a,b, n-1) + rFibNum(a, b, n-2);
}
In the code above;
a) how many base cases are there?
b) what is the limiting condion?
a. n >= 0 b. a>= 1
c. b >= 1 d. n>= 1
• Show less1 answer
- booboo123 askedretu... Show moreint func1 (int m, int n)
{
if (m==n || n==1)
return 1;
else
return func1(m-1,n-1) + n*func1(m-1,n);
}
Based on the function above;
a) What precondition must exist in order to prevent the code abovefrom infinite recursion?
a. m >= 0 and n >=0 b. m >= 0 andn>= 1
c. m >= 1 and n >=0 d. m >= 1 andn >= 1
b) What is the value of func1(5, 3)?
a. 15 b. 21
c. 28 d. 32
c) Which of the following would be an invalid call to the functionabove?
a. func1(0,1) b. func1(1,0)
c. func1(4,9) d. func1(99999, 99999) • Show less1 answer
- Anonymous askedflow, so th... Show more
Suppose that eachsource siin a multisource, multisink problemproduces exactly piunits of
flow, so thatf(si,V) = pi. Suppose alsothat each sink tjconsumes exactlyqj units, sothat f(V,
tj) =qj,where Σipi =Σj qj. Show how toconvert the problem of finding a flow f that obeys
these additionalconstraints into the problem of finding a maximum flow in asingle-source,
single-sink flow network.• Show less1 answer
- Anonymous asked0 answers
- booboo123 askeda) In an array-based stack, the time-complexity of the destroyStackfunction is O(n) bec... Show moreTrue or False
a) In an array-based stack, the time-complexity of the destroyStackfunction is O(n) because all the elements of the stack have to bedestroyed
b) The time-complexity of the copy constructor of the classstackType is O(n).
• Show less1 answer
- booboo123 askedb) In an orde... Show moreTrue or False
a) Searching, inserting, and deleting require traversal of thelinked list.
b) In an ordered list, we need to modify the algorithms (from anormal linked list) to implement the search, insert, and deleteoperations.
• Show less1 answer
- Anonymous askedvariable.equals(v... Show moreExplain the difference between the following twostatements:
variable == variable1;
variable.equals(variable1);
• Show less4 answers
- Anonymous askedrow 2 column... Show moreSuppose we wanted to produce the following output: (java)
row 1 column 1 row 1 column 2
row 2 column 1 row 2 column 2
row 3 column 1 row 3 column 2
We could accomplish this by using the for loop below withanother loop that is nested. The nested loop is not provided.However, you will need to complete the empty section in order toproduce the desired output above.
int rowNum, columnNum;
for (rowNum=1; rowNum <=3; nowNum++)
{
COMPLETE CODE HERE!
}• Show less2 answers
- booboo123 asked1 answer
- Anonymous askedd.... Show moreOne way to implement a priority queue is to use an ordinary_____.
a. linked-list
b. array
c. stack
d. list
• Show less1 answer
- Anonymous askedC) va... Show moreAn effective way to implement a priority queue is to use a(n) _____structure.
A) stack
B) array
C) varied
D) treelike
• Show less1 answer
- Anonymous asked- desing algorithms to compute the in-degree and theout-degree of every vertex in agiven directed gr... Show more- desing algorithms to compute the in-degree and theout-degree of every vertex in agiven directed graph G=(V,E) byusing adjacent list representation and a adjacent matrixrepresentation respectively , analyse the time complextiy of youralgorithm• Show less1 answer
- Anonymous askedI need to turn in my homework by Monday morning, and I have noidea how to work with recursion. Pleas... Show more
I need to turn in my homework by Monday morning, and I have noidea how to work with recursion. Please help me out. I willrate
All of those functions have to be in the same program withoutusing any loops
-Multiply a*b, but we cannot use any arithmetic operators except++ and --;
Unsigned multiply (unsigned a, unsigned b)
-Return the number of chars in s, not counting the terminatingnull char. Don’t use strlen, have the function find out thelength
intstringLength (const char s[])
-Return 1 if all the chars in are digits, return 0 otherwise
allDigits(const char[])
-Return the number represented in the string. For instancevalue(“1234”) would return 1234. You may assume withoutchecking that if the arg were passed to allDigits. allDigits willreturn 1
value ( const char s[])
-Return the sum of all size elements of the array
double sum (const double a[], unsigned size)
-Return the product of all size elements of the array
double sum (const double a[], unsigned size)
-Return the maximum value if all size elements of the array
double max (const double a[], unsigned size)
-Return the minimum value if all size elements of the array
double min (const double a[], unsigned size)
-Return the index of the maximum value.
unsigned maxIndex (const double a[], unsigned size)
-Return the index of the minimum value.
unsigned maxIndex (const double a[], unsigned size)
-We assume that both array arg have the size elements. Thefunction’s job is to copy all the value from b to thecorresponding positions in a.
void coppyArray (double a[], const double b[], unsigned size)
Thank you so much.2 answers
- Anonymous askedWrite a program that allows the user to search an ASCII textfile loaded into main memory. The progra... Show moreWrite a program that allows the user to search an ASCII textfile loaded into main memory. The program should be able to searchby byte value, ASCII string, or address. The program should reportthe answer, surrounded by context, that is, part of the file oneither side of the answer. The program should run until the userselects an option to quit.
The program must use a command line argument to discover thename of the file to load. The program must use dynamic memoryallocation to create an array of bytes in which to load and processthe file. The array should allow addressing of individual bytesfrom the file, and it should be exactly the same size (in bytes) asthe file.• Show less1 answer
- Anonymous asked1 answer
- Anonymous asked1 answer
- Anonymous askedThe access time of a memorymodule is k.log N, where k is a constant, the logarithm is withrespect to... More »1 answer
- Anonymous askedProblem: Im working on program where a the user is playing a game(black Jack) and I need to store hi... Show moreProblem: Im working on program where a the user is playing a game(black Jack) and I need to store his scores each time he plays Ihave been working on this all day but i cant get it I know i haveto use arrays but I cant get it to work:
.......but basicly i need to know how to store variable info in anarray if possible
but if there's an alternate way please do share it with me thanks
Im working with C++ in Visual Studio Express GUI
Albert Einstein winning with 21!
AlbertEinstein losing with12!
AlbertEinstein losing with 23!
AlbertEinstein winning with 18!
AlbertEinstein winning with 16!
Mycode:(first way I tried it)
voidsetNumber(int num, int value)
{
intintscoreArray[100];
intscoreArray[num] =value;
String^ messHistory = "game1" + intscoreArray[0] + "\n\n"
+"game2 " + intscoreArray[1]+ " " + intscoreArray[2]+" ";
MessageBox::Show( messHistory );
}
int getNumber(int num)
{
int intscoreArray[100];
returnintscoreArray[num];
}
void inputData()
{
for (int i = 0 ; i <=gameCount ; i++)
{
setNumber(i,getData());
}
}
int getData()
{
int PlayerSum;
if ( PlayerSum < 16 )
{
PlayerSum= int::Parse( PlayerCardNum_1->Text )
+int::Parse( PlayerCardNum_2->Text)
+int::Parse( PlayerCardNum_3->Text);
}
else
{
if(DealerSum >= 16)
{
PlayerSum= int::Parse( PlayerCardNum_1->Text )
+int::Parse( PlayerCardNum_2->Text);
}
}
return PlayerSum;
}
then i placethe fuction void setNumber(int num, int value) where i wanted tocall it
-------------SECOND WAY
gamesPlayed =countWon + countlost;
// gameCount = gamesPlayed + 1;
// int test= 0;
// intintscoreArray[10];
//
// for(int x = 0; x <= gameCount; x++ )
// {
// //test++;
//
// if (gameCount == test)
// {
// intscoreArray[x] =PlayerSum;
//
// }
// else
// {
// if(gameCount== test)
// {
// intscoreArray[x] =PlayerSum;
// }
// }
//
//
// }
//
//
// String^ messHistory = intscoreArray[0] + " "
// + intscoreArray[1]+ " "+ intscoreArray[2]+ " ";
//
// MessageBox::Show( messHistory );
• Show less0 answers | http://www.chegg.com/homework-help/questions-and-answers/computer-science-archive-2009-december-12 | CC-MAIN-2014-35 | refinedweb | 3,567 | 60.24 |
To Azure Service Bus, Event Hubs, and Relay customers,
We have some updates regarding our presence on the classic Azure Portal. As mentioned in a previous blog post about retiring Service Bus on the classic Azure Portal this blog post is about what to expect if you decide to start using the new Azure Portal today or sometime before the October 5, 2017 retirement date (we are extending our support from the earlier stated date of September 15, 2017).
When we first announced we would be offboarding from the classic Azure Portal we acknowledged three major elements we were missing that customers were expecting for us to have on the new portal:
- Metrics for Service Bus Basic, Standard, and Premium Messaging plans as well as metrics for Azure Relay
- Support for slashes "/" in entity names
- Viewing Event Hubs in a Messaging type namespace in the portal
The good news is that two of these items will be available in the new portal around the October 5 deprecation date! Please read on to find out which two items will be supported going forward and the one that won't be.
Metrics
What metrics, in preview, are coming to the new portal for Service Bus Basic, Standard, and Premium Messaging plans?
- Incoming messages
- Length (Delayed)
- Outgoing Messages
- Failed Requests
- Internal Server Errors
- Server Busy Errors
- Other Errors
- Size (Delayed)
- Successful Requests
- Total Requests
What about Azure Relay? These metrics will be offered at an entity level.
- Active Connection
- Active Listener Connections
- Bytes Transferred
- Listener Connection Attempts
- Success
- Client Error
- Server Error
- Sender Connection Attempts
- Success
- Client Error
- Server Error
- Listener Connection Disconnects
- Sender Connection Disconnects
Slashes "/" in entity names (Supported Today)
For some quick background on the second item, "Support for slashes '/' in entity names", if you create a Queue or Event Hub under a namespace that has "/" in the name, it will not be available for you to manage in the new Azure Portal. We know it sounds strange and we have a blog post that hopefully helps explain the concept better.
To provide an answer for this in the meantime, since the new Azure Portal has a strong reliance on Azure Resource Manager, it has an implicit assumption that the names of Azure Resource Manager addressable resources should not contain multiple URI segments in the resource name.
ARM is required to parse the Resource ID URI for Routing, authorization, auditing, policy, etc. and all those functions require URI segments to be in pairs, where the first segment in the pair is the resource type and the second segment is the resource name.
For example, in the below ARM ID for a topic, ARM expects the segments in bold to denote the resource "type" and the segments in italics to be the resource name:
/subscriptions/{sub-id}/resourcegroups/{resourceGroupName}/provider/Microsoft.ServiceBus/namespaces/myServiceBusNamespace/topics/myTopicName
This assumption is obviously broken in the case of multi-segment topic names that Service Bus and Relays natively support, this means that these specific entities cannot be created or managed with Azure Resource Manager. Don't worry though, we have support for this today on the new Azure Portal, find out how we do this here.
Viewing Event Hubs in a Messaging type namespace in the portal (Not Supported)
For the third item, as part of our namespace separation plan we began working on last year, we separated Azure Service Bus, Azure Event Hubs and Azure Relay from one another to be their own stand-alone resources. There are still some remnants of the old way though. For instance, a Messaging namespace with an Event Hub entity and a Queue entity!
If you view this particular namespace in the new Azure Portal today you would see your Queue entity, but not your Event Hub entity. We will NOT be supporting the ability to manage an Event Hubs entity on a Messaging namespace type in the new portal. We recommend you split your namespace, however, if this is not an option you can use NamespaceManager or Service Bus Explorer to manage these Event Hubs. Please keep in mind you cannot create any NEW Event Hub entities under that Messaging namespace, we have disabled that option. New Event Hub entities can only be created on an Event Hubs namespace. If you wish to convert your Messaging Namespace with Event Hubs entities please read this article about our auto-convert option.
We hope you have decided to move to the new Azure Portal already or are in the process of doing so before the October 5 date. We also hope you enjoy the new experience!
Happy Messaging and Data Streaming,
The Azure Service Bus, Event Hubs, and Relay team
--Relay out--
@Justin in one of the previous posts you mentioned a workaround for segmented paths. You might want to add a link to the post () and update the statement “This assumption is obviously broken in the case of multi-segment topic names that Service Bus and Relays natively support this means that these specific entities cannot be created or managed with Azure Resource Manager.”
My bad, the link is there. | https://blogs.msdn.microsoft.com/servicebus/2017/08/29/update-azure-service-bus-presence-on-the-classic-azure-portal/ | CC-MAIN-2018-26 | refinedweb | 853 | 50.7 |
>
I have an animation called "Swing" attached to an object called FreeCharacter_01 and a script that tells it to play when the Mouse0 button is pressed. Both of these, the animation and the script, are both attached to FreeCharacter_01, but when I hit the left mouse button, it says "there is no 'animation' attached to the gameobject but a script is trying to access it". I've searched all over the internet and other forums to find the answer and all of them just don't work out. I can't figure it out? Any ideas? (P.S. I am a massive noob) Also, here's the script.
#pragma strict
function Update()
{
if(Input.GetMouseButton (0))
{
animation.Play("Swing");
}
}
Copy the animation. Lip in the array on the animator as the first element and this should work.
Are you sure that the correct "swing" animation assigned to the object?
It always helps if you show us the actual error 9and any stack trace if there is one) instead of paraphrasing it.
At a wild guess, your object is actually made up of multiple objects and your script is on one child and the animation component on another.
Another wild guess is you are confusing animation, which is the legacy system, with animator which you need to use Mechanim to use.
A third wild guess, your import of the animations is set wrong in your model importer.
Did you ever figure this out? I'm getting the same error. (And that's exactly what the error says)
Did you try changing the animation mode?
Answer by HD32
·
May 04, 2015 at 10:20 AM
Here you go sir:
var walkClip: AnimationClip;
var anim: Animation;
function Start() {
anim = GetComponent.<Animation>();
anim.AddClip(walkClip, "walk");
}
I hope that helped. If you wanted to use C# here is the code:
using UnityEngine;
using System.Collections;
public class ExampleClass : MonoBehaviour {
public AnimationClip walkClip;
public Animation anim;
void Start() {
anim = GetComponent<Animation>();
anim.AddClip(walkClip, "walk");
}
}
All of that is from the scripting API, so it should work. Just put incorporate that into the code you have right now and it should import the animation for use along side the script. =D
Answer by Crystalline
·
May 04, 2015 at 09:19 AM
The animation you are using is more than sure "legacy" type, in newer unity versions this wont work unless you mark it as legacy.
Solution:
Select animation,go into debug mode,
there is a little button with three
lines in the right corner of the
inspector , and then select
.
Multiple Cars not working
1
Answer
animated sword + script
1
Answer
I need to swing the ship on 2D
1
Answer
Walking animation problem.
0
Answers
what is the jump axis for if (Input.GetAxis(" ? ")
2
Answers | https://answers.unity.com/questions/695944/there-is-no-animation-attached-to-the-gameobject-b.html | CC-MAIN-2019-18 | refinedweb | 462 | 63.39 |
Created on 2009-02-03 13:51 by orsenthil, last changed 2009-05-05 08:54 by georg.brandl. This issue is now closed.
When using the python debugger, most often I step ('s') through the
code base and I often Call the standard library modules, whichever are
imported in the scripts.
This is often not desirable as I know that errors are within my modules
and not in standard library.
Two things which a developer can do while using pdb is:
1) Be careful as not to 's' into stdlib but use next 'n'.
2) If accidentally stepped into, then use return 'r'.
Instead of doing this repeatedly, how about having method in the
debugger to skip certain modules ( like standard library modules,
certain package's modules etc)
This would save a lot of distraction in call and returns, and developers
can just go ahead with 's' and Enters.
Added a skip keyword argument to Bdb and Pdb class constructors to allow
skipping of modules based on a list of glob-style matches (see fnmatch),
as per the following example:
import pdb;Pdb(skip=['django.command*']).set_trace()
Applied the patch, added documentation and committed it as r72322. Thanks! | https://bugs.python.org/issue5142 | CC-MAIN-2020-16 | refinedweb | 199 | 59.03 |
Scala FAQ: What does the use of three questions marks (
???) in Scala mean?
The syntax of using three question marks in Scala lets you write a not-yet implemented method, like this:
def createWorldPeace = ???
The methods you define can also take input parameters and specify a return type, like this:
def doSomething(s: String): Int = ???
Usefulness of `???`
This three question mark approach is really nice for when you want to stub out some methods as you’re working on a problem. For instance, you might be working on an IoT application to control a garage door, and you know you’re going to need methods to open and close the door, but you don’t know the details yet. In this case you can stub out your methods like this:
def openGarageDoor = ??? def closeGarageDoor = ???
Martin Odersky’s original post about ???, and an interesting discussion
In this funny and interesting post on the scala-lang.org website, Martin Odersky writes, “If people don’t hold me back I’m going to add this to
Predef,” which he later did. Here’s a link to the current Predef source code, which shows the
??? method is defined like this:
/** * `???` can be used for marking methods that remain to be implemented. * @throws NotImplementedError */ def ??? : Nothing = throw new NotImplementedError
Note: If you’ve never seen a discussion about adding a new feature to a programming lanuage, check out that funny/interesting link. People suggest using
TODOor
ToDoinstead of
???, but Mr. Odersky decides to go with
???in the end. (He also notes that he wants to use the
???syntax in training classes.)
If you ever wondered what
??? meant in Scala, I hope this is helpful. | https://alvinalexander.com/scala/what-does-three-question-marks-in-scala-mean | CC-MAIN-2020-10 | refinedweb | 279 | 76.11 |
Bible: What Does Hebrews 10:26-39 Teach Us About Apostasy?
The Law of God
Hebrews 10: 26-39: The Outcome of Apostasy
Apostates Choose to Go Their Own Way
Now the writer returns to a discussion of the consequences of repudiating the sacrifice of Christ and reverting to old ways (vv. 26-39).
“Sinning willfully” points to a rejection of the Lordship of Christ over their lives; in such a case, they know the truths of the gospel, but choose to go their own way (that is, become apostates).
No longer having available to them the only true way to God, they can expect to experience nothing but the wrath of God that will devour them (vv. 26-27).
In Moses’ day, the author states, the Israelites mercilessly executed those disobedient to God’s law after they gave the sinners their due process (v. 28).
John MacArthur
The Cross of Christ
Three Offenses
Arguing rhetorically, the author seeks to convince his readers that people who transgress against Christ deserve far worse punishment.
He delineates three specific offenses that such apostates commit:
(1) They trample the Son of God underfoot;
(2) they count the blood of the covenant by which they were set apart to God a common thing; and
(3) they insult the Spirit of grace (v. 29).
[Those who walk on Christ treat Him as someone unworthy of any regard.
Those who consider Christ’s blood as common (“unclean,” NASB) show disdain for His sacrifice for them.
(This sin seems especially heinous, because these people apparently participated in the Lord’s Table where they partook of the elements.)
That they were actually believers (“by which he was sanctified”) is not an acceptable interpretation, unless the punishment mentioned here is temporal.
Those who insult the Holy Spirit who graciously reached out to save them demonstrate hatred for Him and contempt for His gift.]
Heaven and Hell
Hell: Is it a Real Place of Punishment?
Do you believe in a literal place of eternal punishment called Hell?
Necessity for Final Salvation
view quiz statistics
God Will Punish the Wicked
As support for his view that God will surely punish the wicked, the author cites two OT verses that highlight God’s vengeance and judgment upon His people (v. 30; cf. Deut. 32:35-36).
He stresses how horrible it would be to experience the Lord’s powerful wrath (“fall into the hands of the living God”) [v. 31].
The writer asks his readers to reflect upon their early Christian experience (“after you were illuminated”) when they suffered persecution for the faith (v. 32; cf. 6:4).
Sometimes unbelievers hurled insults at them and caused them to endure hardship; at other times, the world merely abused Hebrew Christians for siding with those whom they were persecuting (v. 33).
Regarding this latter case, the author recalls how they cared for him while he was in prison, and experienced the State’s confiscation of their property in return (v. 34a).
Yet he adds that they exhibited a godly attitude (“joyfully accepted”) and employed an eternal perspective toward their plight (v. 34b).
Do Not Discard Your Reward
The author exhorts them to take their past faithfulness into consideration at the present time, and not throw away the reward God would give them for standing firm in their faith (v. 35).
He sees a need for them to persevere to the end, so that they might receive what God promised to give them (v. 36).
Quoting Habakkuk 2:3-4 as support, the author contends that his readers must learn to live by faith and wait for God to rescue them (vv. 37-38a).
[Ryrie includes a helpful discussion of the Scripture writers’ varying usage of this OT passage (New Testament Study Bible, 412).]
Those who fail to persevere God does not approve (v. 38b).
The author asserts that he (and they) (“we”) will surely persevere in belief, and God will “save” them; others who shrink back in fear and unbelief will experience God’s chastening hand (“perdition,” NKJV; “destruction,” NASB).
© 2013 glynch1 | https://hubpages.com/religion-philosophy/Hebrews-10-Part-Two-The-Outcome-of-Apostasy | CC-MAIN-2017-30 | refinedweb | 678 | 62.61 |
Arduino is a fantastic microcontroller platform, but the IDE can feel quite limiting once you go beyond “Hello world” projects. If you’ve outgrown the Arduino IDE, consider PlatformIO.
PlatformIO is a a powerful IDE for Internet of Things (IoT) devices with some great features:
- Supports Arduino, ARM Cortex, and many other IoT platforms
- Full-featured code editor based on Atom with tab-completion, inline help, multiple cursors, refactoring, the works
- Supports Build, Upload, Unit Test actions with continuous integration options
- Build files with sane library management
- Serial port monitor with automatic restart
These features really shine when you start building more complex projects.
Here I showcase how you can build and upload a simple multi-Arduino device project that would be a pain to manage otherwise.
Motivation
Let’s say you want to build a system build out of:
- a sender – an Arduino device with some attached sensors – captures information from the environment, and beams it into the air via XBee, Bluetooth, plain-jane RF, etc.
- a receiver – a second Arduino device that reads the information from the first, remote Arduino device and actuates, e.g. some motors or servos
The Arduino IDE is not well-adapted to this kind of problem, because it uses a paradigm where one sketch = one device. If you want to work on a project that uses two devices you have to use two separate .ino sketches, running in two separate processes. You have to manage these two projects separately, test and upload them on different schedules. Then what if you need to share some common headers, like, let’s say, a .h file which contains an encryption key for RF? That’s not straightforward at all.
PlatformIO makes it easy to work with multiple devices.
Hello world!
Install the PlaformIO IDE, fire up Atom, and start a new project. Add whatever device you want to support – I’m using the Adafruit Feather, specifically the model which has an RFM69 RF module on it for radio communication. This will initialize a minimalist project with nothing in it:
Now create a new file under src/sender/blink.cpp, which will contain Arduino’s version of Hello world, the blink sketch:
#include <Arduino.h> // The Hello world of the Arduino world! Blink at 5Hz. void setup() { pinMode(13, OUTPUT); } void loop() { delay(100); digitalWrite(13, HIGH); delay(100); digitalWrite(13, LOW); }
Now connect your initial Arduino to a USB port, and hit Upload from the PlatformIO menu.
That’s it – you should get some output to the effect that the code was successfully built, your code should be uploaded to your Arduino, and the builtin LED should start flashing.
Hint: You can access all the build actions – build, upload, and test – using the F7 key.
Static address
Use the PlatformIO > List Serial Ports menu item to find which serial port your Arduino device is using. On Linux, the name of the device you be of the form `/dev/ttyACMXXX`; Macs instead have the form `/dev/USBXXX`. Now open the platformio.ini file at the root of your project, which was auto-generated for you. Mine looks like:
[env:feather32u4] platform = atmelavr board = feather32u4 framework = arduino
We’re going to start by giving it a meaningful name, and assigning it to a specific upload port:
[env:feather32u4_sender] platform = atmelavr board = feather32u4 framework = arduino upload_port=/dev/ttyACM0
Save the file, and upload again, you should get exactly the same result. While it seems like we haven’t done much, we’ve created the skeleton for our future build file for multiple devices. When you work on bigger project, you will also manage dependencies, and many other aspects of the project, through the platformio.ini file.
Two devices
To extend this to two devices, it’s very straightforward. Make a new file in the project, src/receiver/blink.cpp. Set the interval for this one so it blinks more slowly:
#include <Arduino.h> // Blink this pup at 1Hz. void setup() { pinMode(13, OUTPUT); } void loop() { delay(500); digitalWrite(13, HIGH); delay(500); digitalWrite(13, LOW); }
Now connect your second device, list serial devices through the menu, and find out the name of the new device, e.g. /dev/ttyACM1. Now we’re ready to update the platformio.ini file:
[env:feather32u4_sender] platform = atmelavr board = feather32u4 framework = arduino src_filter = +<*> +<sender/> -<receiver/> upload_port = /dev/ttyACM0 [env:feather32u4_receiver] platform = atmelavr board = feather32u4 framework = arduino src_filter = +<*> -<sender/> +<receiver/> upload_port = /dev/ttyACM1
We’ve added a second section corresponding to the second device. The important thing here is the addition of src_filter, which specifies which files are to be compiled and sent to each device. We specified – and + to specifically include and exclude subdirectories of the source folder.
When you hit F7 this time, you’ll see many more options — you can Build, or Upload, which will send both sketches one after the other to their respective Arduinos. You can also build and upload for a specific environment, in which case only one Arduino will be updated.
If you upload both sketches, you will see your designated sender blink fast, and the designated receiver blink slowly.
Shared files
With this structure, it’s very easy to share a file between the two sketches. Simply create the src/constants.h file, with content, for example:
#DEFINE secret_key "OMGSOSECRet"
Then #include it in both the cpp files. Easy.
Optional: static addresses
The scheme here will work as long as you remember to reconnect your Arduinos in the right order — otherwise they’ll be assigned different TTY addresses and you’ll be uploading each sketch to the wrong place. To avoid this, you can change your udev rules to assign a static /dev address, e.g. `/dev/receiver`, to a given Arduino. Follow this tutorial here, and update your platformio.ini file accordingly. It’s a bit of work but it will pay off later in the hassle you save.
2 thoughts on “Multi-Arduino projects with PlatformIO”
Nice ! I didn’t know about “upload_port=xxxxxxxxx” in platform.ini when you have multiple devices | https://xcorr.net/2016/12/13/multi-arduino-projects-with-platformio/?shared=email&msg=fail | CC-MAIN-2019-26 | refinedweb | 1,007 | 62.27 |
Use Test-Driven Development with mock objects to design object oriented code in terms of roles and responsibilities, not categorization of objects into class hierarchies.
Isaiah Perumalla
WCF extensibility points allow you to customize the process by which messages are translated, formatted, and sent over the wire for more customized services.
Aaron Skonnard
MSDN Magazine December 2007
Web Service Software Factory is designed to help you build Web service solutions that follow known architecture and design patterns, as Aaron Skonnard explains here.
MSDN Magazine December 2006
We show you how .NET Services within the Azure Services Platform makes it easy to bring workflow apps to the cloud.
MSDN Magazine April 2009
This article describes how to use XHTML and ASP.NET MVC to implement REST services.
MSDN Magazine July 2009
Windows Communication Foundation supports several serialization mechanisms and provides a simple, interoperable foundation for future service-oriented applications. Here Aaron Skonnard explains it all.
MSDN Magazine August 2006
WPF is one of the most important new technologies in the .NET Framework 3.0. This month John Papa introduces its data binding capabilities.
John Papa
Chris Tavares explains how the ASP.NET MVC Framework's Model View Controller pattern helps you build flexible, easily tested Web applications.
Chris Tavares
MSDN Magazine March 2008
/Invoice//LineItem[@Sku='123']/*
// C# DOM Code
XmlNodeList nodes =
doc.SelectNodes("/Invoice//LineItem[@Sku='123']/*");
for (int i=0; i<nodes.Count; i++) {
... // process selection here
}
<xsl:apply-templates
<price>10</price>
<price>10.0</price>
<price>10.00</price>
price = '10' || price = '10.0' || price = '10.00'
number(price) = 10
data(birthdate) < xs:date('1972-01-01')
LineItem/node()[. instance of element of type xsd:double]
LineItem/*[. instance of xsd:double]
("Nathan", 1.32e0, true(), xs:date('2001-05-24'))
(//Sku, //Price, //Description)
(1, 2, 3, 4)
((1, 2), (3, 4))
(((1), (2, 3), (4)))
($node1, $node2, $node3) | ($node2, $node3, $node4) ->
($node1, $node2, $node3, $node4)
($node1, $node2, $node3) intersect ($node2, $node3, $node4)->
($node2, $node3)
($node1, $node2, $node3) except ($node2, $node3, $node4) ->
($node1)
insert((1, 3, 4), 2, 2) -> (1, 2, 3, 4)
remove((1, 2, 3), 2) -> (1, 3)
index-of((10, 20, 30), 20) -> 2
empty(()) -> true
exists((1, 2, 3)) -> true
count((1, 2, 3) -> 3
sum(1, 2, 3) -> 6
avg(1, 2, 3) -> 2
min(1, 2, 3) -> 1
max(1, 2, 3) -> 3
distinct-values(//Sku)
//Sku[not(preceding::Sku = .)]
//Price[1]
(//Price)[1]
(10, 20, 30)[2] -> (20)
$seq[count(*) > 1 and @id < 1000]
Catalog/Prices/Price = 9.95
Catalog/Prices/Price != 9.95
not(Catalog/Prices/Price != 9.95)
not(Catalog/Prices/Price = 9.95)
Price[1] is Price[1] -> true
Price[1] isnot Sku[1] -> true
some $item in //LineItem satisfies
(($item/Price * $item/Quantity) > 100)
every $item in //LineItem satisfies
(($item/Price * $item/Quantity) > 100)
some $x in (1, 2, 3), $y in (2, 3, 4)
satisfies $x + $y = 4
LineItems/(Sku|Price)/text()
LineItems/Sku/text() | LineItems/Price/text()
for $i in //LineItem return ($i/Price * $i/Quantity)
sum(for $i in //LineItem return ($i/Price * $i/Quantity))
for $sp in distinct-values(//Salesperson)
return ($sp,
for $item in //LineItem[Salesperson = $sp]
return $item/Description)
if ($Price > 100)
then ($Price * .90)
else ($Price * .95)
upper-case('Michael') -> 'MICHAEL'
string-pad('-', 7) -> '-------'
matches(SSNumber, '\d{3}-\d{2}-\d{4}')
Send your questions and comments for Aaron to xmlfiles@microsoft.com. | http://msdn.microsoft.com/en-us/magazine/cc188789.aspx | crawl-002 | refinedweb | 563 | 55.13 |
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Recent posts by Oliver Moore
Reading a UTF-8 Encoded File
Hi All,
Apparently this is a long standing bug
UTF-8 encoding does not recognize initial BOM
This class here seeems like a reasonable solution:
UnicodeReader and UnicodeInputStream
Hope this is of use.
show more
17 years ago
I/O and Streams
Reading a UTF-8 Encoded File
Hi All,
Having looked at this a bit further, I think I'm having a problem with Notepad inserting a UTF8 byte-order mark of EF=BB=BF in any files saved as UTF8.
I'm assuming that Java doesn't add this BOM when it writes a UTF8 file.
I'm just suprised that Java parses in the BOM when it reades the template, thus causing the problem I'm seeing. Is anyone aware of a way round this? I'm going to try saving the files without BOM (I think Jedit can do this) but I'd like to know if there's a better way.
I guess I could examine the incoming stream in binary and look for the BOM coming in and filter if present.
Here's a couple of useful links I found whilst looking at this issue
Sun Forums
Unicode Transformation Formats: UTF-8 & Co.
show more
17 years ago
I/O and Streams
Reading a UTF-8 Encoded File
Hi David,
Thanks for the coding tip.
I've had a look at the files being created using PSPad and the characters that seem to be present are ��� (Hex EF BB BF). If I look at the base file I'm parsing in PSPad, these charaters are not visible (in Hex or other).
If I look at the first line of any Notepad created file I parse in by printing to the console, the first charater is always ? (I assmume meaning unknown character).
If I modify the String and the write it out to file, it's fine. It's just when I insert one parsed template into another that I see these charaters carried into the file. I assume this is because the file writer discards the junk characters prior to writing if they're at the start of the string to be writen, but will carry them if they're present in the String somewhere.
I hope this information is of help.
show more
17 years ago
I/O and Streams
Reading a UTF-8 Encoded File
Hi All,
I've written a program which parses several templates inserting relevant values and then writes them to a new file.
When I read a UTF-8 encoded file created using notepad and saved as UTF-8 encoded text, a junk (unknown) character gets inserted as the first character of the resultant string created from the incoming stream.
If I write the String containing the junk character out to a file after manipulation, the file is created with no problem and the junk character is not shown.
If I insert the String representing the file into another String and then write a file out containing both Strings, the first character before the inserted String will be junk.
As you can see from my code, I'm cutting the first character off of any incoming file to resolve this. However, in some cases I need to re-read and insert Strings into files that have been written using my output code (below). If I read a file which has been created using my code, the junk character is not present on reading the file.
Is this known behaviour (E.g. notepad doesn't implement utf-8 files in the same way as Java) or is there an error in my code that is causing it? I can solve this by noting whether the file I'm reading is a native file or has been created in Windows but this seems to be a work around rather than solving the problem directly.
Any help would be much appreciated.
Regards,
Oliver
My code for reading the file:
public static String parseTemplate(String templatePath) { File aFile = new File(templatePath); InputStreamReader reader = null; String template; StringBuffer temp = new StringBuffer(); int counter = 0; try { FileInputStream inStream = new FileInputStream(aFile); reader = new InputStreamReader(inStream, "utf8"); BufferedReader inBuf = new BufferedReader(reader); while ((template=inBuf.readLine()) != null) { if(counter == 0){ template = template.substring(1,template.length()); } System.out.println("inBuf " + template); temp.append(template + "\n"); // read a line from the file counter++; } inBuf.close(); } catch (Throwable e) { e.printStackTrace(); } template=temp.toString(); System.out.println("FIO " + template); return template; }
Code for Writing File
public static void writeFile(String outFilePath, String fileText) { File aFile = new File(outFilePath); OutputStreamWriter writer = null; try { FileOutputStream outStream = new FileOutputStream(aFile); writer = new OutputStreamWriter(outStream,"utf8"); BufferedWriter outBuf = new BufferedWriter(writer); outBuf.write(fileText); outBuf.close(); } catch (Throwable e) { e.printStackTrace(); } }
show more
17 years ago
I/O and Streams
BufferedReader.readLine() skips lines
ah... that's the exact problem.... thanks...
First time I've played with IO...
show more
17 years ago
Java in General
BufferedReader.readLine() skips lines
Hi All,
I'm reading a file using BufferedReader.readline(). I've noticed that the formatting of the file you're trying to read has to be spaced by carrage returns!! Is this correct behaviour?
My Code is:
FileInputStream inStream = new FileInputStream(aFile); InputStreamReader inReader = new InputStreamReader(inStream,"unicode"); BufferedReader inBuf = new BufferedReader(inReader); String line; int recCount = 0; while ((line=inBuf.readLine()) != null) { line = inBuf.readLine(); recCount++; System.out.println(recCount + ": " + line); } inBuf.close();
If my text file is formatted as follows, only test2 and null will be output.
Start Of File
test1
test2
test3
EOF
However, if I format it as follows, test1, test2 and test3 will be output.
Start Of File
*carriage return
test1
*carriage return
test2
*carriage return
test3
EOF
Utilmately, this can be solved by carefully formatting my input first, but can anyone explain if it's an inherant Java problem or my code.
Thanks!!
show more
17 years ago
Java in General
order of validation
Hi All,
I have 3 elements on a form I wish to validate. All three elements are required, but one is an email so I am applying the email rule to it as well. However, when the form is submitted, the JS error regarding the email formatting is only returned if all three fields are populated. If I submit an invalid email address with the 2 other required elements empty, only errors for the missing elements are displayed.
Is this normal behaviour or am I doing something obviously wrong? I would expect an error to be displayed for the first level of testing an element failed at.
show more
17 years ago
Struts
Struts character encoding
Hi All,
I believe the issue I was experiencing was that all strings passed back to the server were assumed to be in ISO format, despite the page encoding being set to utf-8. As I now understand it, many browsers do not correctly support passing the encoding type of a response back to the server.
After much messing about with request/response setContentType(), <%@ page contentType="text/html; charset=utf-8" %> and modifying the Struts-config file I was having very little success until I found that there is an encoding filter included in Tomcat 5 (\jakarta-tomcat-5.0.19\webapps\servlets-examples\WEB-INF\classes\filters\SetCharacterEncodingFilter.java).
Implementing this has solved all my issues and everything seems to be carried as utf-8 now. Seeing as this corrected my issue, I assume the root cause was that the contentType of the request object was not being set correctly at some point in the application.
I've attached a few useful links below on the subject of encoding. Any comments on my fix or a definite cause of my issue would be appreciated.
Common problems with i18n and servlets/jsp-s
Tomcat User-list
Struts Guide
show more
17 years ago
Struts
Struts character encoding
Hi All,
I'm using struts 1.1 as part of my web application, but I've hit some major character encoding issues! Why does struts automatically encode all of the strings placed directly into a given form bean as ISO-8859-1?
I've set all my JSPs to UTF-8 encoding, but the � symbol still renders incorrectly as �� if I look at the contents of my form bean. I can get out of this by doing the following
String marinaTitleI = marina_page.getmarina_title(); String marinaTitleC = new String(marinaTitleI.getBytes("ISO-8859-1"), "UTF-8"); marina_page.setmarina_title(marinaTitleC);
but this is a pain to do for all strings. I guess I could put a method to do this conversion in all of my entity beans, but this issue seems so fundamental that I feel I'm missing something.
Is this normal behaviour for struts, or is there a setting I require?
My reason for using UTF-8 encoding is that the � symbol seems to be rendered incorrectly by my JSPs (be it dynamic content or hard coded in the page) as �� when I use ISO-8859-1.
Any suggestions as to either solve the struts conversion problem, or how to render � correctly with ISO-8859-1 would be much appreciated.
Regards,
Ols
show more
17 years ago
Struts
Passing parameters between actions
Hi Lasse,
Thanks, that does illustrate a few things I wasn't aware of, however, I have a couple of questions.
As I understand it from the post you suggested, the following happens:
1)form submitted
2)paramters placed into request header
3)struts places parameters into associated formbean
4)action completes then forwards to uri defined in struts config
5)2nd action instanciates, and the only paramters available to it are those it submitted by the form (1)
Is this correct?
As I understand it now, all the original paramters should be available in the request accoss the whole action chain. Placing parameters in a form bean only copies them from the request into the bean, not remove them from the request?
By stating that the request parameters cannot be be changed, I assume this means that that the original values passed into the action (and therefore used to popluate the associated actionForm) cannot be changed. However, you can add parameters to the request, such as a resultSet which is then forwarded to a JSP and those values will be available. In the case above, I can add messages to the request which are passed, but no other parameters I put in are passed. Is this what you would expect as messages use a different mechanism to attach to the request?
Whilst exploring this problem, I stopped forwarding to the 2nd action, and started going to a JSP. I also added a hidden value "test" in the form which is not associated with the formBean for the add action. I would expect this to be available to the JSP the action forwards to by using a request.getParameter, but it is not. As this "test" request paramter is part of the original input, should I not be able to access it as I'm not attempting to modify it in any way?
Thanks for your help...
show more
18 years ago
Struts
Passing parameters between actions
Hi all,
I have the following 2 actions, addGalleryPictureAction and listGalleryAction shown below, chained together with struts. The general idea is that on successful file upload, a new list of pictures should be generated and then passed to a page to display this new list. All this depends on the paramter marina_id, which is passed from the upload form to the add action. However, it does not get passed to the list action. Printing the marina_id in the list action shows it as null, even though I am explicitly setting it in the add action.
The list action definitly works both individually and as part of a chain, and the add action completes as the picture is created, as are the DB entries. The only difference between this and other code blocks with a similar flow is that the original uplaod form on the jsp is set to multipart/form-data... Should this make any difference?
Any help would be gratefully recieved...
Regards,
ols
public class AddGalleryPictureAction extends Action { public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception { // New ActionMessages instance for storing any messages in the process ActionMessages messages = new ActionMessages(); String test2=request.getParameter("marina_id"); System.out.println("test2"+test2); //New ActionErrors instance for storing any errors in the process ActionErrors errors = new ActionErrors(); //ActionForm form is cast to type ent_gallery (as defined in struts-Config.xml) Ent_gallery ent_gallery = (Ent_gallery)form; //retrieve the file representation FormFile file = ent_gallery.getfile(); //place file name in ent_gallery for Database storage ent_gallery.setfile_name(file.getFileName()); //Constructs file path to write file to on server String file_path = ent_gallery.getfile_path() + ent_gallery.getfile_name(); try { byte[] image = file.getFileData(); ByteArrayInputStream stream = new ByteArrayInputStream(image); BufferedImage bImg = ImageIO.read(stream); int width = bImg.getWidth(); int height = bImg.getHeight(); double ratio = 0.0; if (height > width) { //used to scale correctly if image is taller than wide ratio = 300*((double)width/(double)height); int scaledWidth = (int)Math.round(ratio); BufferedImage output = new BufferedImage(scaledWidth, 300, BufferedImage.TYPE_3BYTE_BGR); Graphics2D g = output.createGraphics(); g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR); g.drawImage(bImg,0,0,scaledWidth,300,null); ImageIO.write(output, "jpeg", new File(file_path)); } else { //used to scale correctly if image is wider than tall ratio = 350*((double)height/(double)width); int scaledHeight = (int)Math.round(ratio); BufferedImage output = new BufferedImage(350,scaledHeight, BufferedImage.TYPE_3BYTE_BGR); Graphics2D g = output.createGraphics(); g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR); g.drawImage(bImg,0,0,350,scaledHeight,null); ImageIO.write(output, "jpeg", new File(file_path)); } //used to create smaller thumbnail image for picture rotating file_path = ent_gallery.getfile_path() + "thumbnails\\" + ent_gallery.getfile_name(); BufferedImage output = new BufferedImage(115,95, BufferedImage.TYPE_3BYTE_BGR); Graphics2D g = output.createGraphics(); g.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR); g.drawImage(bImg,0,0,115,95,null); ImageIO.write(output, "jpeg", new File(file_path)); //close the stream stream.close(); //destroy the temporary file created file.destroy(); //Create instance of news business object GalleryBO galleryBO = new GalleryBO(); //ActionForm form is cast to type ent_gallery (as defined in struts-Config.xml) //and passed to the add method of galleryBO galleryBO.addPicture((Ent_gallery)form); // Generates message to confirm cost period added to DB ActionMessage message = new ActionMessage("gallery.successful.add"); messages.add(ActionMessages.GLOBAL_MESSAGE,message); saveMessages(request,messages); //Removes FormBean from request, so that it is not used to //populate the field of the jsp control is forwarded to request.removeAttribute(mapping.getAttribute()); request.setAttribute("marina_id",ent_gallery.getmarina_id()); //return a forward to confirm gallery add.jsp return mapping.findForward("success"); } catch (Throwable e) { //Else the message key from the exception is added to the ActionErrors errors e.printStackTrace(); ActionError error = new ActionError(e.getMessage()); errors.add(ActionErrors.GLOBAL_ERROR,error); } //Errors are saved and request is returned to the input page (as defined in struts-COnfig.xml for this action) saveErrors(request,errors); return new ActionForward(mapping.getInput()); } }
public class ListGalleryAction extends Action { public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception { Connection con = null; try { System.out.println("here"); //Create instance of class to get DB connection //Used so DB details can be changed at a single point ConnectionPool pool = new ConnectionPool(); //Get connection from DB pool con = pool.getConnection(); //Get marina_id from page action was called from String marina_id = request.getParameter("marina_id"); //create new instance of GalleryDAO and pass it the instance of the connection pool GalleryDAO galleryDAO = new GalleryDAO(con); //Create new collection, containing all races returned by findAllByMarina method Collection col = galleryDAO.findAllByMarina(marina_id); StringBuffer inputURLBuffer = request.getRequestURL(); String inputURL = inputURLBuffer.toString(); if (inputURL.endsWith("listResourcesSession.do")) { //Gets current session, or creates a new one if one does not exist HttpSession session = request.getSession(true); //Store bean in a session scope bean, the name of which is defined in BeanNames session.setAttribute(BeanNames.GALLERY_LIST,col); return mapping.findForward("success"); } else { //Create new collection, containing all categories returned by findAll method request.setAttribute(BeanNames.GALLERY_LIST,col); //If successful, the request is forwarded to the mapping corresponding to //"success" (as defined in struts-Config.xml for this action) return mapping.findForward("success"); } } catch (SQLException e) { e.printStackTrace(); throw new RuntimeException("Unable to get connection."); } catch (NamingException e) { e.printStackTrace(); throw new RuntimeException("Naming Failure."); } finally { //Close the DB connection try { if (con != null) con.close(); } catch (SQLException e) { throw new RuntimeException(e.getMessage()); } } } }
show more
18 years ago
Struts
Navigation with in application
Hi Vijay,
I've never used this extension presonally, but Struts workflow extensions seems to encapsulate what you're trying to do...
Hope it's of help...
show more
18 years ago
JSP
Steps to Converting HTML page to JSP
Hi Somshekhar,
I'm not really sure you're asking the right question here...
HTML is static, i.e. you write a pge once, and every time a user views it, it will look the same.
JSP is dynamic, i.e. it allows you to perform actions and generate data using java embedded in either the jsp page or an external class file. These actions are carried out by the JSP websever application (Tomcat, JBoss etc) to generate HTML code, which is then sent to the client browser for interpretation and display.
A very quick example of how HTML and JSP co-exist is below. The starting point is an html page with a form on, one single textbox called nameIn for the user to enter their name, and a submit button to submit the form to the jsp page below. I assume you've read some of the basics of how JSP tags work...
<html> <body> <% //get name entered in the textbox by the user String name = request.getParameter("nameIn"); %> <!-- welcome message, showing name user entered on previous form note how the <h1> html tag is used to format the text as normal --> <h1>Hi <%= name %>, welcome to this JSP page!!</h1> <br> <% //evaluate if the enter name is ols, and if it is, output the html enclosed in the jsp tags if (name.equals("ols"){ %> <font color="red"><i>this message is displayed if the username entered is ols</i></font> <% //close the if statement } %> </body> </html>
I would strongly suggest getting a book on the subject (search for JSP on amazon, and javaranch for book reccomendations).
If I was going from a static HTML page to JSP, I'd want to think about where any dynamic data is coming from (xml, DB, user input), the types of operations you want to perform on it, whether a framwork is suitable rather than JSP pages, are there different type of user accessing your site, does it require security, what web server are you using etc... I'm sure others can think of far longer lists...
I hope this is of some help...
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18 years ago
JSP
Struts 1.1 question (Might not be an easy...
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18 years ago
Struts
DB Processing Cost
Hi All,
I need to return the following to my JSP page:
A list of results from a single table (to use in a select box)
A single result from the same table to display for editing.
In this scenario, the list I return will always contain the single result I wish to display. My question is, which is the most efficient way to get the single result. I see 3 alternatives:
1) Place the key for the single result in a response, Then iterate through the list at the JSP page until I find the desired single result.
2) go to the database twice, once to generate the list from a db access, then a 2nd db access to get the single result.
3) When processing the returned result set, pull out the desired single result and place it in a seperate bean to return to the page.
I think option 1 is the best, as 2 has 2 expensive DB accesses in it, and 3 would seem to make the class file processing the result very specific. Does this sound reasonable, or is there a better way altogether?
show more
18 years ago
JDBC and Relational Databases | https://www.coderanch.com/u/46036/Oliver-Moore | CC-MAIN-2022-33 | refinedweb | 3,459 | 53.81 |
IRC log of tagmem on 2007-09-19
Timestamps are in UTC.
08:19:01 [RRSAgent]
RRSAgent has joined #tagmem
08:19:01 [RRSAgent]
logging to
08:19:13 [Zakim]
Zakim has joined #tagmem
08:19:46 [Rhys]
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08:21:48 [DanC_lap]
Topic: Agenda Review
08:22:26 [DanC_lap]
Present: Stuart, Rhys, Henry, Dan, Norm, Noah
08:23:31 [Stuart]
- Reviewing "Cool URIs..."
08:23:31 [Stuart]
- #fragId / indirect identification
08:23:31 [Stuart]
- namespaceDocument-8
08:23:31 [Stuart]
- Web 2.0
08:23:31 [Stuart]
- Noah's WebArch Presentation
08:23:32 [Stuart]
- URI Testing
08:23:35 [Stuart]
- WebArch Vol 1 2nd Ed, and/or Vol 2: How to get started?
08:27:01 [Stuart]
08:29:01 [Noah]
Noah has joined #tagmem
08:34:23 [Stuart]
08:34:29 [Norm]
Norm has joined #tagmem
08:34:48 [Stuart]
08:34:52 [DanC_lap]
Topic: Reviewing "Cool URIs..." (ISSUE-57 HttpRedirections-57 )
08:41:13 [DanC_lap]
HT: we agreed to ask to add "http: " to the "On the Semantic Web, URIs identify ..." , right? [right]
08:42:28 [DanC_lap]
NM: "On the Semantic Web, " suggests there are 2 webs. I understand this is tutorial, but I think this concern could be addressed with something like... [missed]
08:42:43 [Rhys]
q+
08:44:03 [DanC_lap]
... "With the addition of Semantic Web capabilities..."
08:46:14 [Rhys]
ack me
08:46:16 [DanC_lap]
(consensus emerges; Norm is editing a review comments message)
08:51:19 [DanC_lap]
NM: "description of a URI" is a use/mention bug... should be "description of a resource identified by a URI"
08:51:51 [DanC_lap]
DanC: not sure it's cost-effective to repair all such use-mention buglets in informal text
08:52:16 [DanC_lap]
SKW: "identified resource" works
08:52:19 [DanC_lap]
DanC: OK
08:54:00 [DanC_lap]
DanC: I wonder if people are using this "Be on the Web" box to argue against doc#term URIs. Note that "description of" is not "representation of"
08:56:15 [DanC_lap]
SKW: acme.com is used, still. needs to be example.com
08:58:19 [DanC_lap]
(hmm.. N3 syntax... it actually only uses the turtle fragment; might be better to cite turtle than N3. maybe I'll send that as an individual comment)
09:22:17 [Rhys]
DC: Draws diagram on whiteboard. SW takes picture.
09:23:20 [Rhys]
DC: Suggests that the story could be told by successive elaboration of the diagram. Starting from the statement about 'Don't be ambiguous' and refining through the various approaches that are proposed.
09:25:56 [Rhys]
q+
09:27:49 [Rhys]
ack me
09:28:20 [Rhys]
q+
09:29:56 [Rhys]
q?
09:34:14 [Rhys]
ack me
09:36:44 [DanC_lap]
[scribe missed quite a bit... picking up...]
09:38:04 [DanC_lap]
HT: there's some stuff about fragments and conneg, no? [indeed...
]
09:38:39 [DanC_lap]
HT: going back to our discussion of namespaceDocument-8 and the XML Schema datatype namespace document, we're saying that the difference between a datatype and a paragraph doesn't matter for this purpose
09:38:46 [DanC_lap]
DanC: umm... yeah.
09:44:43 [DanC_lap]
HT: on the other hand, we get a contradiction if xsd:boolean is a paragraph and a datatype [presuming datatypes and paragraphs are disjoint]. So shouldn't give a 200 for the /2001/XMLSchema namespace URI
09:45:20 [DanC_lap]
DanC: I don't think so; I prefer to ammend the HTML media type so that head/@profile takes away some constraints on fragids
09:45:47 [DanC_lap]
[there are other designs in this space too]
09:52:19 [Stuart]
Whiteboard photo is attached to:
10:04:12 [DanC_lap]
SKW: note Dan's diagram uses distinct style for URIs and resources. that seems significant
10:07:09 [DanC_lap]
NM: not clear that "err on the side of caution" is well-motivated...
10:07:27 [DanC_lap]
... e.g. in the case of a relational table, TimBL and I agreed that a 200 was ok...
10:08:03 [DanC_lap]
... it's not clear to me that doing a redirection where it's not needed isn't more harmful than doing a 200 where it shouldn't have.
10:10:15 [DanC_lap]
SKW: the "all its essential characteristics can be conveyed in a message" is a bit out of context; we didn't give that as definition of Web document, but information resource
10:12:14 [Stuart]
Stuart has joined #tagmem
10:18:16 [DanC_lap]
DC noodles... ... not well motivated; for example, we think many relational tables are information resources, and this recommendation would result in unnecesary redirections.
10:40:14 [Stuart]
seems relevant
11:10:14 [DanC_lap]
SKW: so NDW has an action to finish this review...
11:10:50 [DanC_lap]
... meanwhile, what about the hypothesis that "Cool URIs..." obviates much of Rhys's draft on HTTP URIs?
11:11:05 [DanC_lap]
DanC: in that my main goal is to help people choose URIs, yes.
11:11:50 [DanC_lap]
NM: with some reservations about other HTTP status codes and whether we're elaborating or suggesting changes to the HTTP spec, yes
11:13:53 [DanC_lap]
Rhys: I think "Cool URIs..." addresses much of what "Dereferencing HTTP URIs" was going to say, but there are some other bits that seem useful for covering other aspects of ISSUE-57/ HttpRedirections-57 and ISSUE-28 (fragments)
11:16:12 [DanC_lap]
HT: to some extent, yes [scribe struggles to capture the gist of what he actually said]... though there are some critical bits of Rhys's draft that I want us to work on
11:16:31 [DanC_lap]
q+
11:17:23 [DanC_lap]
HT: I'm somewhat sympathetic to the point that a write-up of our decision on httpRange-14 is still in order.
11:19:09 [DanC_lap]
DanC: looking at the redirections ISSUE-57, I see bits like "Particular concerns are the cachability (or otherwise) of HTTP redirection responses" that I don't think "Cool URIs..." should cover that.
11:19:11 [DanC_lap]
Rhys: quite
11:19:57 [DanC_lap]
Rhys: one possibility re more-than-a-mail-message on issue 14, perhaps webarch 2nd ed?
11:20:06 [DanC_lap]
HT: well, but I'm not holding my breath
11:21:01 [DanC_lap]
(see also Users/ndw/TAG on norm's disk)
11:21:57 [DanC_lap]
ACTION NDW: relay comments as constructed today to the SemWeb EO IG editors of "Cool URIs..."
11:22:26 [DanC_lap]
s/critical bits/critical bits around "web presence"/
11:22:34 [DanC_lap]
ACTION: Norm relay comments as constructed today to the SemWeb EO IG editors of "Cool URIs..."
11:22:34 [trackbot-ng]
Sorry, couldn't find user - Norm
11:22:39 [ht]
ht has joined #tagmem
11:22:39 [DanC_lap]
ACTION: Norman relay comments as constructed today to the SemWeb EO IG editors of "Cool URIs..."
11:22:39 [trackbot-ng]
Created ACTION-52 - Relay comments as constructed today to the SemWeb EO IG editors of \"Cool URIs...\" [on Norman Walsh - due 2007-09-26].
11:23:24 [DanC_lap]
trackbot-ng, ACTION-52 is on ISSUE-57
11:23:50 [Rhys]
PROPOSED RESOLUTION: TAG will not publish the Dereferencing URIs draft in its current form. We anticipate that a suitably updated version of the Cool URIs document will provide appropriate guidance on the httpRange-14 finding.
11:25:21 [DanC_lap]
DanC: that decision doesn't seem worthwhile, but updating the status seems worthwhile
11:25:29 [DanC_lap]
trackbot-ng, status
11:26:10 [DanC_lap]
e.g.
11:26:43 [DanC_lap]
no, that page has rlewis2
11:27:09 [Rhys]
ACTION: Rhys to update the current version of the Dereferencing URIs draft to show that we will not formally publish it.
11:27:09 [trackbot-ng]
Created ACTION-53 - Update the current version of the Dereferencing URIs draft to show that we will not formally publish it. [on Rhys Lewis - due 2007-09-26].
11:27:13 [DanC_lap]
BREAK for lunch, 'till 1:15pm
12:06:52 [ht]
I would change this sentence "The nature key is the label which allows us to distinguish between the different targets that could be used for the purpose. @
12:06:53 [ht]
to
12:07:51 [ht]
"The nature key is the label which allows us to distinguish different contributions that the same resource can make"
12:09:16 [Stuart]
recapitulating our agenda for today:
12:09:16 [Stuart]
- Reviewing "Cool URIs..."
12:09:16 [Stuart]
- #fragId / indirect identification
12:09:16 [Stuart]
- namespaceDocument-8
12:09:16 [Stuart]
- Web 2.0 (WBN)
12:09:17 [Stuart]
- Noah's WebArch Presentation (WBN)
12:09:19 [Stuart]
- URI Testing
12:09:21 [Stuart]
- WebArch Vol 1 2nd Ed, and/or Vol 2: How to get started?
12:16:24 [Noah]
Noah has joined #tagmem
12:20:20 [Rhys]
Scribe: Rhys
12:20:25 [Rhys]
Scribenick: Rhys
12:21:08 [Rhys]
Topic: namespaceDocument-8
12:21:14 [Rhys]
ISSUE: 8
12:21:30 [Rhys]
NW: Projects draft document
12:22:01 [Rhys]
DC: Asks about the full URIs for various thinkgs, such as the nature key
12:22:26 [Rhys]
DC: The proposal is that for RDDL, they will own the URIs?
12:22:29 [Rhys]
NW: Yes
12:22:53 [Rhys]
SW: Use of term key occurs earlier than it's definition.
12:23:08 [Rhys]
NW: that's an editorial issue to be fixed.
12:24:01 [Rhys]
NW: Draws diagram on whiteboard showing the relationships between namespaces, natures, ancilliary resources.
12:24:27 [Rhys]
DC: Trying to determine which of this is the generic model and which is specific to RDDL
12:24:59 [Rhys]
RL: Notes that the discussion is about Henry's example, based on RDDL
12:25:26 [Rhys]
DC: Maybe the title of section 2 should be 'using RDDL'?
12:25:46 [Rhys]
HT: But it's not about RDDL, we don't mind where the RDF comes from.
12:26:27 [Rhys]
DC: Do we need to call this 'the model'?
12:27:05 [Rhys]
HT: I think that we need to do this to address the concerns previously expressed to the TAG
12:28:42 [Rhys]
NW: A couple of years ago, we decided that we couldn't change RDDL, but that we could create a model for an abstraction that would let us represent this information.
12:29:24 [Rhys]
DC: The problem is that calling it 'The Model' is very definitive
12:29:49 [Rhys]
NM: Maybe we should look at the parts of this that are mandatory.
12:30:18 [Rhys]
HT: This part of this document is not about what you must do, it's about the resources that are available to you when writing your namespace document.
12:31:11 [Rhys]
NM: We do say that if you create a namespace we are recommending that you have a namespace and that you have some materials on the web.
12:31:56 [Rhys]
NM: We could say, that you need to put up some stuff about the namespace, and that, whatever the mechanism (RDDL or whatever), there is a set of information that you should have for the namespace
12:33:07 [Rhys]
HT: I don't agree about standardising what should be in the namespace document. RDDL provides a vocabulary for imparting the information to humans. We are extending this to machines
12:34:26 [Rhys]
NM: I thought we were defining the way that you could get something that could then be used to get back to RDF. I thought we were trying to define a preferred way to get you to a schema.
12:34:47 [Rhys]
NM: Could be stylesheets, schemas etc.
12:34:58 [Rhys]
DC: What about using RDF datatypes?
12:35:18 [Rhys]
HT: This is about connecting resources, not datatypes
12:36:07 [Rhys]
SW: This part of the narrative is about ancilliary resources to be used with the namespace. There is another set of information about the things that are in the namespace.
12:36:51 [Rhys]
HT: As of today, if you go to the namespace document, you'll find just connections to associated resources.
12:38:07 [Rhys]
HT: However, there are assertions in the old namespace document about links to names in namespaces but those anchors don't exist
12:38:34 [Rhys]
NM: So we are moving in the direction that the new description document has both connections to associated resources and datatypes
12:39:20 [Rhys]
HT: So the example includes definitions that use RDF datatypes and relate to the names in the namespace
12:41:22 [Rhys]
NM: Trying to infer what we can do in the general case. Is it correct to have the individual names in the same document as the associated resources. It's probably OK.
12:41:55 [Rhys]
NM: Maybe should be a standard way in all RDDLs of referring to a name in the namespace.
12:42:02 [DanC_lap]
(RDDL's normative reference competes with rdfs:isDefinedby. )
12:42:36 [Rhys]
HT: I think that you could conclude that the schema #boolean is either a name in the namespace or an associated resource or both.
12:43:41 [Rhys]
HT: There are two ways to improve this. Either in every datatype statement, could add an additional RDF type named thing (thing identified by something in the namespace).
12:44:07 [Rhys]
DC: Usually this is done by rdf is-defined-by
12:44:36 [Rhys]
NM: Whatever the appropriate expression of this, it seems as though a triple would be the right relationship
12:45:10 [Rhys]
DC: In practice, the processors look for a schema and then carry on processing.
12:45:44 [Stuart]
q+
12:45:47 [timbl]
timbl has joined #tagmem
12:47:24 [Rhys]
HT: Just because x#y resolves, doesn't mean that y is a name in the namespace.
12:48:06 [Rhys]
NM: my sense is that I'm asserting that the name I've defined is in the namespace
12:48:36 [Rhys]
DC: In practice the way that people do this is what Henry wrote on the board.
12:49:21 [DanC_lap]
which is: { xsd:boolean rdfs:isDefinedBy "" }
12:50:26 [Rhys]
NM: To me the namespace is a set of names.
12:50:39 [Rhys]
NW: There are a couple of puns going on here, so it works out.
12:50:40 [Stuart]
q?
12:51:16 [Rhys]
NM: I see the namespace is an information resource. The associated document is a description of the namespace.
12:53:47 [Rhys]
HT: If the W3C server were a standard Apache server, and you requested the XML Schema URI, you'd get a 404. I'd be happy if when you retrieved schema.html you got a 200, and when you asked for the schema you'd get a 303 to the HTML document and if you asked for namespace as RDF, it GRDDLs the namespace html document and returns the RDF.
12:54:35 [Rhys]
NW: You'd have to use xml:base in the RDF.
12:55:40 [Rhys]
NW: Henry's description is a little different to the 303 story we have been telling so far.
12:56:40 [Rhys]
NM: Often the representation is a rather 'noisy' representation of the resource (advertising etc.)
12:57:23 [Rhys]
NM: Since we are used to that, it seems less of a stretch to claim that Henry's story covers representations of the namespace
12:57:37 [Rhys]
NM: I don't think that we don't need the 303
12:59:50 [Rhys]
DC: Possible argument for the 303. Dan draws diagram. Shows URI of a namespace. Access to the namespace URI 302s to the HTML document. If you ask for RDF you get a 200 and an RDF representation, possibly from the GRDDL.
13:00:10 [Stuart]
10.3.3 302 Found
13:00:10 [Stuart]
The requested resource resides temporarily under a different URI.
13:00:19 [Rhys]
Scribe note: In Henry's description above, should have written 302 not 303
13:01:07 [Rhys]
NM: Why not return HTML by conneg from the namespace URI
13:01:33 [Rhys]
HT: To preserve the difference between the namespace and namespace document
13:02:06 [Rhys]
SW: I think 302 is wrong, because it is not temporarily moved.
13:02:21 [Rhys]
SW: I think it should be 301.
13:02:59 [Rhys]
NM: I don't agree, because 301 means it's permanently moved.
13:04:04 [Rhys]
NM: I think it's 303. But I also feel there is an asymmetry. Both the RDF and the HTML have the same relationship to the namespace URI.
13:04:37 [Rhys]
Scribe note - forget the change from 303 to 303. Leave it as 303.
13:07:12 [Rhys]
HT: If today, with the magic in the configuration on the W3C site, you request HTML from the namespace URI, you get it, but you also get a content header.
13:08:07 [Rhys]
NM: What is the implication of content location header?
13:08:25 [Rhys]
DC: You get the representation, but it's also a representation of this other URI
13:09:19 [Stuart]
14.14 Content-Location
13:09:19 [Stuart]
The Content-Location entity-header field MAY be used to supply the
13:09:19 [Stuart]
resource location for the entity enclosed in the message when that
13:09:19 [Stuart]
entity is accessible from a location separate from the requested
13:09:20 [Stuart]
resource's URI. A server SHOULD provide a Content-Location for the
13:09:20 [Stuart]
variant corresponding to the response entity; especially in the case
13:09:22 [Stuart]
where a resource has multiple entities associated with it, and those
13:09:24 [Stuart]
entities actually have separate locations by which they might be
13:09:26 [Stuart]
individually accessed, the server SHOULD provide a Content-Location
13:09:28 [Stuart]
for the particular variant which is returned.
13:10:39 [Rhys]
NW: I'll make the changes to the diagrams, and then hand the words over to you Henry.
13:10:57 [Rhys]
NW: Claims that his action on this document is now complete
13:11:26 [DanC_lap]
trackbot-ng, status
13:12:43 [Rhys]
ACTION: ht do in 2 weeks produce another revision of the namespaceDocument-8 draft from Norm
13:12:44 [trackbot-ng]
Created ACTION-54 - Do in 2 weeks produce another revision of the namespaceDocument-8 draft from Norm [on Henry S. Thompson - due 2007-09-26].
13:13:42 [Rhys]
Topic: URI Testing
13:13:54 [DanC_lap]
13:15:04 [Rhys]
DC: URI mailing list doesn't correspond to any working group at W3C. TAG monitors the list.
13:15:52 [Rhys]
DC: I started a Wiki page on URI testing. People copy and paste each others testing techniques. There is no current coordination.
13:16:31 [Rhys]
DC: Tempted to suggest that some kind of interest group be established on URI and IRI testing.
13:18:29 [Rhys]
DC: There is a new Java API in JCP for performing URI manipulations separate from the actual HTTP operations
13:18:49 [Rhys]
DC: I think the time is right to organise something around this.
13:19:47 [Rhys]
DC: I'd like it to be relatively disconnected for the same reason as to keep the manipulations separate from HTTP
13:22:33 [Rhys]
SW: Dan, what would you like the TAG to do?
13:24:17 [Rhys]
DC: We could say that this is a good idea and ask the director to consider starting some kind of activity.
13:27:10 [DanC_lap]
agenda + second life arch interop, action to connect to x3d
13:32:55 [Rhys]
General discussion about what the form of any such follow on activity might be
13:33:02 [DanC_lap]
ACTION Dan: work with SKW on a few paragraphs of thinking around a URI testing group (IG/WG/XG?)
13:33:23 [DanC_lap]
ACTION: Dan work with SKW on a few paragraphs of thinking around a URI testing group (IG/WG/XG?)
13:33:23 [trackbot-ng]
Created ACTION-55 - Work with SKW on a few paragraphs of thinking around a URI testing group (IG/WG/XG?) [on Dan Connolly - due 2007-09-26].
13:33:56 [DanC_lap]
agenda?
13:34:18 [Stuart]
- #fragId / indirect identification
13:34:19 [Stuart]
- Web 2.0 (WBN)
13:34:19 [Stuart]
- Noah's WebArch Presentation (WBN)
13:34:19 [Stuart]
- WebArch Vol 1 2nd Ed, and/or Vol 2: How to get started?
13:34:27 [Stuart]
plus virtual worlds
13:34:57 [DanC_lap]
- HT on declarative XHTML fix-up
13:35:45 [Rhys]
Topic: Virtual Worlds
13:35:53 [DanC_lap]
13:36:12 [Rhys]
DC: Where are we on the action?
13:37:20 [Stuart]
13:37:42 [ht]
is relevant
13:38:59 [Rhys]
NM: I've not had a response. I'll try again.
13:39:17 [DanC_lap]
(so ACTION-2 continues)
13:39:23 [Noah]
Slashdot link to standardization effort for virtual worlds protocols:
13:40:54 [Noah]
Contains link to 2nd Life Wiki:
13:43:11 [Rhys]
DC: We've not followed up with Croquet
13:43:33 [Rhys]
NM: I think that Croquet is more of a distributed environment for professional use
13:43:48 [Rhys]
NM: Do you build your own community>
13:43:55 [Rhys]
s/>/?
13:44:20 [Rhys]
DC: Tend to have your own. They are looking at more global communities
13:45:07 [Rhys]
HT: QWAQ is trying to build a business model on top of Croquet.
13:47:45 [Rhys]
Topic: Summary
13:48:24 [Rhys]
SW: About to close. 3 days was good. Enjoyed the group work and the progress has been good.
13:48:43 [Rhys]
NW: 3 days is good.
13:48:47 [Rhys]
General agreement
13:49:29 [Rhys]
NW: Don't assume that just because we don't have a third day's agenda we only need a two day meeting
13:49:54 [Rhys]
NM: Liked the ability to get some small stuff done on the third day.
13:50:39 [Rhys]
General feeling that open agendas can be useful, but we shouldn't necessarily assume this is always a good idea.
13:53:52 [Rhys]
SW: We are adjourned
13:55:05 [Rhys]
HT: I've just found that in Croquet, the connections between rooms are called portals. These are labelled with TPostcards that are not URIs. However, they are described as being similar to URLs in web browsers.
13:55:24 [Rhys]
rrsagent, make logs member visible
13:55:24 [RRSAgent]
I'm logging. I don't understand 'make logs member visible', Rhys. Try /msg RRSAgent help
13:55:44 [Rhys]
rrsagent, make minutes
13:55:44 [RRSAgent]
I have made the request to generate
Rhys
13:55:52 [ht]
rrsagent, make logs world-visible
14:05:14 [Rhys]
Rhys has left #tagmem
14:06:13 [skw]
skw has joined #tagmem | http://www.w3.org/2007/09/19-tagmem-irc | CC-MAIN-2014-52 | refinedweb | 3,859 | 67.38 |
- NAME
- VERSION
- SYNOPSIS
- DESCRIPTION
- TRAITS APPLIED
- IMPLICATIONS FOR ROLES
- CAVEATS
- SEE ALSO
- SOURCE
- BUGS
- AUTHOR
NAME
MooseX::MarkAsMethods - Mark overload code symbols as methods
VERSION
This document describes version 0.15 of MooseX::MarkAsMethods - released May 30, 2012 as part of MooseX-MarkAsMethods.
SYNOPSIS; # ...".
By default we check for overloads, and mark those functions as methods.
If
autoclean => 1 is passed to import on using this module, we will invoke namespace::autoclean to clear out non-methods.
TRAITS APPLIED); };
IMPLICATIONS FOR ROLES"
CAVEATS
Roles
See the "IMPLICATIONS FOR ROLES" section, above.
meta->mark_as_method()
You almost certainly don't need or want to do this. CMOP/Moose are fairly good about determining what is and what isn't a method, but not perfect. Before using this method, you should pause and think about why you need to.
namespace::autoclean;
SEE ALSO
Please see those modules/websites for more information related to this module.
overload, B::Hooks::EndOfScope, namespace::autoclean, Class::MOP,
-
MooseX::Role::WithOverloading does allow for overload application from
roles, but it does this by copying the overload symbols from the (not
namespace::autoclean'ed role) the symbols handing overloads during class
composition; we work by marking the overloads as methods and letting
-
SOURCE
The development version is on github at and may be cloned from git://github.com/RsrchBoy/moosex-markasmethods>
This software is Copyright (c) 2011 by Chris Weyl.
This is free software, licensed under:
The GNU Lesser General Public License, Version 2.1, February 1999
1 POD Error
The following errors were encountered while parsing the POD:
- Around line 320:
alternative text 'CMOP/Moose handle them.' contains non-escaped | or / | https://metacpan.org/pod/MooseX::MarkAsMethods | CC-MAIN-2016-40 | refinedweb | 273 | 53.71 |
Total Python noob here, probably missing something obvious. I've searched everywhere and haven't found a solution yet, so I thought I'd ask for some help.
I'm trying to write a function that will build a nested dictionary from a large csv file. The input file is in the following format:
Product,Price,Cost,Brand,
blue widget,5,4,sony,
red widget,6,5,sony,
green widget,7,5,microsoft,
purple widget,7,6,microsoft,
projects = { `<Brand>`: { `<Product>`: { 'Price': `<Price>`, 'Cost': `<Cost>` },},}
def build_dict(source_file):
projects = {}
headers = ['Product', 'Price', 'Cost', 'Brand']
reader = csv.DictReader(open(source_file), fieldnames = headers, dialect = 'excel')
current_brand = 'None'
for row in reader:
if Brand != current_brand:
current_brand = Brand
projects[Brand] = {Product: {'Price': Price, 'Cost': Cost}}
return projects
source_file = 'merged.csv'
print build_dict(source_file)
import csv from collections import defaultdict def build_dict(source_file): projects = defaultdict(dict) headers = ['Product', 'Price', 'Cost', 'Brand'] with open(source_file, 'rb') as fp: reader = csv.DictReader(fp, fieldnames=headers, dialect='excel', skipinitialspace=True) for rowdict in reader: if None in rowdict: del rowdict[None] brand = rowdict.pop("Brand") product = rowdict.pop("Product") projects[brand][product] = rowdict return dict(projects) source_file = 'merged.csv' print build_dict(source_file)
produces
{'microsoft': {'green widget': {'Cost': '5', 'Price': '7'}, 'purple widget': {'Cost': '6', 'Price': '7'}}, 'sony': {'blue widget': {'Cost': '4', 'Price': '5'}, 'red widget': {'Cost': '5', 'Price': '6'}}}
from your input data (where
merged.csv doesn't have the headers, only the data.)
I used a
defaultdict here, which is just like a dictionary but when you refer to a key that doesn't exist instead of raising an Exception it simply makes a default value, in this case a
dict. Then I get out -- and remove --
Brand and
Product, and store the remainder.
All that's left I think would be to turn the cost and price into numbers instead of strings.
[modified to use
DictReader directly rather than
reader] | https://codedump.io/share/22mV2egkRwRO/1/using-python-csv-dictreader-to-create-multi-level-nested-dictionary | CC-MAIN-2018-05 | refinedweb | 314 | 54.63 |
This post is a complete guide to building a Progressive Web App (PWA) from the beginning using Google’s Workbox. By the end of this guide, you’ll be a real PWA developer!
If you haven’t already, check out my previous article on the fundamentals of Progressive Web Apps where we explored service workers and how they work, as well as lots of concepts.
This guide will take you through your own practical build where you’ll learn Workbox to complete a real PWA! I’m excited to take you through it. Let’s dive in!
Caching
A service worker is capable of caching files aggressively so that we do not need to request them, again unless they are updated. That is called pre-caching and it happens during the install lifecycle.
Service workers can also intercept fetch events and cache the resulting information. This is called runtime caching and it is natively implemented like this:
// --> sw.js self.addEventListener('fetch', event => { event.respondWith( caches.match(event.request) .then(cachedResponse => { const fetchPromise = fetch(event.request).then(networkResponse => { cache.put(event.request, networkResponse.clone()); return networkResponse; }) // So if there's a cached version available, use it, // but fetch an update for next time. return cachedResponse || fetchPromise; } ) ); });
Don’t worry if you don’t fully understand this code snippet, that’s exactly what you’re here to learn. We are going to use Workbox right from the beginning to cover everything you need to build a PWA!
What is Workbox?
Google’s Workbox is a set of libraries that simplifies the process of caching with service workers. We will use it to both implement pre-caching and runtime caching. The service worker is registered as normal in the main thread. But in the worker thread we can start using Workbox packages right.
Workbox handles runtime caching with what they call a service worker router. This naming makes total sense since we are intercepting URLs so we need to register routes for that. Again, don’t worry if you still cannot see the big picture. You are going to learn by coding.
To each route you need to provide a callback function for the service worker in order to tell it how to cache the request. There are many runtime caching strategies but most of the time we will only need these:
- Cache Only: the service worker forces a response from the cache and never from the network. You mostly will not want to use this strategy because if a match is not found in the cache the response will look like a connection error.
- Network Only: the service worker forces a response from the network and never from the cache. This is actually the default browsers behaviour so there will be very few cases when you want to use this strategy too.
- Cache First falling back to network: the service worker tries the cache first and if there is no cached response it goes to the network. But most importantly: the response from the network is cached before being passed to the browser.
- Network First falling back to cache: the service worker tries the network first. If the request is successful the response is cached before being passed to the browser. If the request fails it falls back to the last cached response.
- Stale While Revalidate: here we only use responses from the cache but we also make a call to the network in the background and if that call is successful we cache that response for the next time. This would be the most common strategy.
Now take another look at the previous code snippet. What strategy is it following? Take a couple of seconds to think about it…
…OK. Time is up! The snippet is implementing Stale While Revalidate natively. We will not need to do that. All these usual runtime caching strategies are pre-defined in the Workbox routing module.
Rick and Morty
Our practical training is going to consist of a simple app that displays a list of 20 characters from the Rick and Morty TV show.
This choice was made based on the fact that the Rick and Morty API does not need authentication which simplifies our job. Well… and also because the show is so cool.
To fulfil this little challenge you will need the help of this public repository.
The
master branch contains a naked project: the app without the service worker blanket. However all necessary packages are already specified and the infrastructure is ready for you to take off.
Each of those steps are zero-based numbered in the shape of branches. They keep a
step-xx-title-of-the-step naming convention.
The step 0 is a replica of
master. No code to be provided there. We will just use it to picture the specific goals. The next steps/branches do involve some development. They are your tasks.
Are you ready to start?
Step 0: Non Progressive App
So first things first. Please clone the repo.
And run:
npm i git fetch --all git checkout step-00-non-progressive-app git checkout -b step-00-non-progressive-app-mine
By doing this you are first installing the dependencies and right next you are switching to the
step-00-non-progressive-app branch and then checking out a copy of it. That will be your start point.
And secondly:
npm run build npm start
Open this URL in Google Chrome:.
You are probably looking at something like this:
If you open the console you will see that you are tracing every retrieved data. On the home page we are collecting 20 random characters. By clicking on one of them you navigate to the detail card where you can find out if the character is dead or alive in the TV show. And then of course you can go back to the list, which will probably look a little different because the items are getting shuffled.
Although this is not required, if you like take a look at the source code to have a better understanding of the project.
Go offline
Open up the Chrome DevTools and go offline. One way of doing this is marking the checkbox “Offline” in the Application section.
Tip: use cmd + shift + p for Mac or ctrl + shift + p for Windows and type “offline”.
Reload the page.
You should see this:
Play with it using the space bar. How much do you score in the offline Dino Game?
Anyway, as you can see we have lost everything. This exactly what we are trying to avoid by making a PWA.
Audit with Lighthouse
Lighthouse is an excellent tool to improve the quality of web pages. It has audits for performance, accessibility, progressive web apps, and more. It is pre-installed in all Chrome browsers and you can either run it from the DevTools or from a Node command.
In our case we are ready to run our npm script, generate the corresponding HTML report and open it up automatically in our browser.
Do not forget to go online again first!
Run this in a second terminal:
npm run lighthouse
As you can see we are scoring very high in everything but in the Progressive Web App part. Click on that PWA grey rounded icon and you will be scrolled down to see what is happening.
Notice that there are a lot of things in red:
Current page does not respond with a 200 when offline.
start_urldoes not respond with a 200 when offline.
Does not register a service worker that controls page and
start_url.
Web app manifest does not meet the installability requirements.
Does not redirect HTTP traffic to HTTPS.
Is not configured for a custom splash screen.
Does not set a theme color for the address bar.
Does not provide a valid
apple-touch-icon.
The HTTPS red flag is totally expected. For security reasons service workers only run over the HTTPS protocol but if the hostname corresponds our localhost the HTTP protocol is also considered secure and we can run our service worker over it. This is intended to make development easier.
We assume that our app will run on a secure protocol in production so we can ignore this supposed failure. However we definitely need to work on the rest of them and make them into green.
Are you ready for the challenge?
From this point on you are going to start providing your own code.
Step 1: Web App Manifest
The first you need is to create a
src/manifest.json.
This file can also be commonly named
manifest.webmanifest.
As mentioned in the previous article the manifest defines the parameters of our installation.
It looks like this:
{ "name": "Google Maps", "short_name": "Maps", "description": "Find your location with Google", "icons": [ { "src": "/images/icons-192.png", "type": "image/png", "sizes": "192x192" }, { "src": "/images/icons-512.png", "type": "image/png", "sizes": "512x512" } ], "start_url": "/?launch=pwa", "background_color": "#3367D6", "display": "standalone", "orientation": "landscape", "scope": "/maps/", "theme_color": "#3367D6" }
For a detailed explanation on each property of the manifest, check out this post by Pete LePage and François Beaufort from the Chromium team.
Let’s focus on your manifest. It should:
Define both the short (
Rick & Morty) and the long (
Rick & Morty PWA) name for the app.
Only include the mandatory 192x192px and 512x512px icons. They are located in
src/assets/img/icons.
Define
/index.htmlas the opened page when the app is first launched.
Tell the browser you want your app to open in a standalone window.
Not be scoped. Either remove that property or leave it as
/.
Use the characteristic yellow from our app for the background color:
#fccf6c. And since the theme color should match the color of the tool bar we will employ
#004d40.
And let’s have some fun while doing this. Go to the Web App Manifest Generator and introduce the corresponding values. Click on the “COPY” button.
Create a
manifest.json in the
src folder and paste the generated file contents.
But that is not all. We are still missing the icons. You can copy this right after the
short_name:
{ [...], "icons": [ { "src": "/assets/img/icons/rick-morty-pwa-icon-192x192.png", "type": "image/png", "sizes": "192x192" }, { "src": "/assets/img/icons/rick-morty-pwa-icon-512x512.png", "type": "image/png", "sizes": "512x512" } ], [...] }
There you go. Your manifest has all the properties it needs for this project. However, it will not be copied to the
dist folder unless we add it to our Webpack configurations.
Open
webpack.config.js. The plugin responsible for copying static files is the
CopyPlugin. Add this line to the array:
{ from: 'src/manifest.json', to: 'manifest.json' },
Add meta and link tags
Open
src/index.html.
Below the last meta tag add these ones:
<meta name="apple-mobile-web-app-capable" content="yes" /> <meta name="apple-mobile-web-app-status-bar-style" content="black" /> <meta name="apple-mobile-web-app-title" content="Rick & Morty PWA" /> <meta name="description" content="PWA with Workbox" /> <meta name="theme-color" content="#004d40" />
Below the last link tag ad these ones:
<link rel="manifest" href="/manifest.json" /> <link rel="apple-touch-icon" href="/assets/img/icons/rick-morty-pwa-icon-512x512.png" />
And it would also be very good to add this after your scripts:
<noscript>Please enable JavaScript to continue using this application.</noscript>
Verify changes with Lighthouse
Let´s do it again:
npm run build npm run lighthouse
We can declare the PWA Optimized section resolved since the HTTPS flag does not represent a problem. In fact notice that in the Installable section we have been always getting the green color on “Uses HTTPS” since localhost is allowed as secure.
However, we still have 3 bugs to solve:
Current page does not respond with a 200 when offline.
start_urldoes not respond with a 200 when offline.
Does not register a service worker that controls page and
start_url.
But don’t worry. Everything will get better when we implement our service worker.
If you didn’t make it
git checkout step-01-web-app-manifest git checkout -b step-01-web-app-manifest-mine
Step 2: App Shell
Add the following code to your
src/index.html file, right after the script tag for
app.js:
<script> if ('serviceWorker' in navigator) { window.addEventListener('load', () => { navigator.serviceWorker.register('/sw.js').then( registration => { console.log(`Service Worker registered! Scope: ${registration.scope}`); }, error => { console.error(`Service Worker registration failed: ${error}`); }, ); }); } </script>
Does it look familiar to you? We already talked about it in the previous article. It really does not matter if we include this snippet of code in a JavaScript file or directly in the HTML’s script tag. It is a question of personal taste and many people do it like this because it looks clear and separated from anything else.
npm run build
Take a look at the console. You should be looking at such an error:
That is expected. We need to create the service worker referenced in your
index.html.
Create the App Shell
One of the nicest things of Workbox version 5 is that it provides full Typescript support. So thinking of this premises you are going to create
src/ts/sw.ts:
import { precacheAndRoute } from 'workbox-precaching'; declare var self: WorkerGlobalScope & typeof globalThis; precacheAndRoute(self.__WB_MANIFEST);
Do you remember when we talked in the previous article about JavaScript threads?
The typing definition for the
self global
this is supposed to be specified in
node_modules/typescript/lib/lib.webworker.d.ts. However there is an issue with this and therefore we need to re-declare that global variable in our file.
self.__WB_MANIFEST is just a placeholder. Webpack will take that reference and generate our final
dist/sw.js. But for that we need to add a new plugin to our
webpack.config.js:
const WorkboxPlugin = require('workbox-webpack-plugin'); module.exports = { [...], plugins: [ [...], new WorkboxPlugin.InjectManifest({ swSrc: './src/ts/sw.ts', swDest: 'sw.js', }), ], };
Do that and build the app again.
npm run build
Now take a look at
dist/sw.js, As you can see the Workbox Webpack Plugin has taken care of including the code of the necessary Workbox libraries and moreover it has automatically created a service worker that pre-caches all our static files.
Tip: search in that file for this string:
workbox_precachingand you will see it more clearly.
Verify changes
If you reload the page your console is probably looking much better now:
Now let’s run Lighthouse again.
npm run lighthouse
Another beautiful sight:
This is what a modern web app should look like!
If you didn’t make it
git checkout step-02-app-shell git checkout -b step-02-app-shell-mine-mine
Step 3: Offline Experience
Now, Google Chrome caches many things without us having a service worker in place. You need to really check if your app shell is getting pre-cached by your implementation.
So first go offline again. Then in order to make sure that the browser completely loads the whole app again, you need to right-click on the browser’s reload button and then click on “Empty Cache and Hard Reload”.
Info: this option is only available when Chrome DevTools is open.
What do you see? It is the App Shell. We lost our dear offline dinosaur.
However wouldn’t it be even cooler if we saw the complete original content when we offline-reload the page? That is our goal.
.
Cache API route
Go online again and reload the page.
Go to your DevTools Application tab and check on the Cache Storage section.
Look to the right. All our app shell, all the files specified in the dist/sw.js are cached there with their corresponding revision hash.
Now we need to cache the responses to the rickandmortyapi API.
The base URL we are using is. And we have 3 different endpoints:
/?gets all the characters. We use it on the home page.
/${charaterId}, e.g.
/1, gets the character with id 1. It is used it on the character page.
/avatar/${charaterId}.jpeg, e.g.
/avatar/1.jpeggets the picture (or avatar) of the character with id 1. It is used it on both pages.
You are going to use Workbox
registerRoute() method to cache routes in runtime. In order to do that we need to use regular expressions.
The first needed regular expression matches retrieved data but not subsequent image requests. In other words: get all calls to the characters but not to their avatar images. Since new characters can die as the TV shows goes on, we need to have the most up-to-date information so we will use the above mentioned
Network First caching strategy.
import { ExpirationPlugin } from 'workbox-expiration'; import { precacheAndRoute } from 'workbox-precaching'; import { registerRoute } from 'workbox-routing'; import { NetworkFirst } from 'workbox-strategies'; // import { NetworkFirst, StaleWhileRevalidate } from 'workbox-strategies'; // For later. declare var self: WorkerGlobalScope & typeof globalThis; precacheAndRoute(self.__WB_MANIFEST); registerRoute( /https:\/\/rickandmortyapi.com\/api\/character(?!\/avatar)/, new NetworkFirst({ cacheName: 'rickandmortyapi-cache', plugins: [ new ExpirationPlugin({ maxEntries: 20, }), ], }), );
You can replace the contents of your
src/ts/sw.ts with that.
The Workbox strategy can be provided with a custom cache name (recommended) and also plugins when needed. In this case you should only be interested in caching 20 entries so you should use the
ExpirationPlugin to set the cache expiration.
A new service worker
Now build the app again.
npm run build
What you are building is a new version of your service worker because more than one byte of the file has changed. The browser detects that automatically and assigns a new id number to it.
Go online again, reload the app and go to your DevTools Application tab again and see what has happened in the Service Workers section.
The service worker lifecycle ensures that the page is controlled by only one version of the service worker at a time. In this moment the old service worker with id
#39529 is still active and the new one with id
#39548 is waiting to be activated. We can activate the new service worker in different ways:
By closing al the windows (tabs) with the same origin (protocol + hostname + port) and then open again the app in a new one.
By clicking on skipWaiting.
By adding the
self.skipWaiting()method to our service worker.
By activating the “Update on reload” checkbox and then reloading the page.
The best practice is to go for Update on reload so please do that and reload the page.
Now the new service worker is active and we have a new cache slot.
If you implemented this route correctly you should see the cached response too:
And you couldn’t do better than taking a peek at the Network tab. You may find this interesting.
If there is a gear icon on the request it means that this is a request made by the service worker. The one without the gear icon is the served response which comes from the service worker and therefore from the Cache Storage.
Cache the images
But what happens if we go offline again and then reload the app with “Empty Cache and Hard Reload”? Well…
You have cached the response from the server but then some resource URLs are making extra calls to get the individual images. You are not caching that yet and that is why we can only see the pre-cached placeholder image on each of the characters.
You need a second regular expression that matches only the calls to avatar images. These are just avatars so we don’t need to constantly have the most up-to-date version of them. The
StaleWhileRevalidate strategy seems to fit our needs here.
registerRoute( /https:\/\/rickandmortyapi\.com\/api\/character\/avatar\/(.+)\.(?:jpeg|jpg)/, new StaleWhileRevalidate({ cacheName: 'avatar-cache', plugins: [ new ExpirationPlugin({ maxEntries: 20, maxAgeSeconds: 7 * 24 * 60 * 60, // 1 week }), ], }), );
You can add that snippet to your
src/ts/sw.ts, too.
Please don’t forget to update your Typescript imports accordingly.
Additionally in this case we choose a maximum age for the cache: the request will never be cached for longer than a week.
npm run build
Then go online and reload the page.
Now your whole app should run perfectly offline!
If you get in trouble
If either the cache or the service workers behave funny and you have the need for a fresh start you can always call on a very useful utility from the DevTools: Application Clear Storage section and then click on “Clear site data”. This will not only remove the storage from this origin but it will also unregister all existing service workers.
Just remember that if you do that you will need to reload twice to see the runtime caches since on the first load you only get the pre-cached files. The rest of the information gets cached during the first life of the app so we will only be able to see it on a second round.
If you get in even more trouble
Even though this project takes a totally framework agnostic approach, this snippet coming from the Angular framework is very useful in extreme situations to really start fresh:
self.addEventListener('install', (event) => { self.skipWaiting(); }); self.addEventListener('activate', (event) => { event.waitUntil(self.clients.claim()); self.registration.unregister().then(() => { console.log('NGSW Safety Worker - unregistered old service worker'); }); });
Just paste at the beginning of your
dist/sw.js file and reload the page.
Then you can build again:
npm run build
Of course you will also have to reload twice in this case.
If you didn’t make it
git checkout step-03-offline-experience git checkout -b step-03-offline-experience-mine
Step 4: Install Experience
You could already install the app if you wanted. Google Chrome should show an install button in the Google omnibar, also known as the address bar.
But we can do significantly better than that.
Install Script
There is already an install button provided for you in
src/index.html. It carries both the
install-btn class and the
hidden class. As you can guess the latter will force the element not to be displayed.
You just need to create an script to handle the interaction with that button. Provide it in
src/index.html, right after the script that registers your service worker and before the
<noscript> tag.
<script src="/js/install.js" type="module"></script>
And make it real by creating
src/ts/install.ts. Add these contents to it:
import { BeforeInstallPromptEvent, UserChoice } from './models/before-install-promp'; const installButton: HTMLElement = document.querySelector('.install-btn'); let deferredInstallPrompt: BeforeInstallPromptEvent | null = null; window.addEventListener('beforeinstallprompt', saveBeforeInstallPromptEvent); installButton.addEventListener('click', installPWA); function installPWA(event: Event): void { const srcElement: HTMLElement = event.srcElement as HTMLElement; // Add code show install prompt & hide the install button. deferredInstallPrompt.prompt(); // Hide the install button, it can't be called twice. srcElement.classList.add('hidden'); // Log user response to prompt. deferredInstallPrompt.userChoice.then((choice: UserChoice) => { if (choice.outcome === 'accepted') { console.log('User accepted the install prompt', choice); } else { srcElement.classList.remove('hidden'); console.log('User dismissed the install prompt', choice); } deferredInstallPrompt = null; }); } function saveBeforeInstallPromptEvent(event: BeforeInstallPromptEvent): void { // Add code to save event & show the install button. deferredInstallPrompt = event; installButton.classList.remove('hidden'); }
In this script there are 2 variables: one for the button element and another one for the
beforeinstallprompt event which we initialize to
null.
Additionally you need to listen to the click event on that button and apply the corresponding callback functions to both events.
The
saveBeforeInstallPromptEvent callback function receives
beforeinstallprompt as an event parameter and saves it in the
deferredInstallPrompt variable. It also makes the button visible by removing the
hidden class.
The
installPWA callback function prompts the banner, hides the button and depending on the user’s choice shows a different message in the console.
And last but not least. This new Typescript file needs to be transpiled by Webpack too so you need to add it to
webpack.config.js.
entry: { app: './src/ts/app.ts', install: './src/ts/install.ts', },
Try it out
npm run build
And reload the page. You should see the install button.
Now click on install. Don’t be afraid. You should see the same as when you clicked on the Google Chrome install button before.
Reject the installation this time and take a look at the console.
And then do the same but this time accept the installation. You will be prompted with the web app in its own window and the console will still be opened. Take a look at the new message before closing the console.
The app should now be displayed among your Chrome Applications.
But most importantly it should be now installed in your system.
You can even create a desktop shortcut for it.
The install button may still be there. You should close and open the app from any of the 2 mentioned sources.
This is it
You did it! If you got here it means that you are already a PWA developer.
Congratulations!
And of course….
If you didn’t make it
git checkout step-04-install-experience git checkout -b step-04-install-experience-mine
Until next time, friend
Here is where our journey ends for now. I hope you enjoyed it!
If you want you provide some feedback to this article please ping me on Twitter.
Or if you think there is something that can be improved please submit a pull request on GitHub.
Cheers! | https://ultimatecourses.com/blog/ultimate-guide-pwa-workbox | CC-MAIN-2021-21 | refinedweb | 4,242 | 66.64 |
Note that there's a difference between the platform's architecture (which is what get_platform() returns) and the pointer size of the currently running Python executable.
On 64-bit Linux, it's rather rare to have an application built as 32-bit executable. On 64-bit Windows, it's rather common to have 32-bit applications running.
The best way to determine 32-bit vs. 64-bit is by using the struct module:
# Determine bitsize used by Python (not necessarily the same as
# the one used by the platform)
import struct
bits = struct.calcsize('P') * 8
This should be portable across all platforms and will always refer to the pointer size of the currently running Python executable. | https://bugs.python.org/msg232030 | CC-MAIN-2019-35 | refinedweb | 117 | 62.17 |
I solutions demonstrate how to use these methods effectively.
Using
os.walk()
The
os module contains a long list of methods that deal with the filesystem, and the operating system. One of them is
walk(), which generates the filenames in a directory tree by walking the tree either top-down or bottom-up (with top-down being the default setting).
os.walk() returns a list of three items. It contains the name of the root directory, a list of the names of the subdirectories, and a list of the filenames in the current directory. Listing 1 shows how to write this with only three lines of code. This works with both Python 2 and 3 interpreters.
Listing 1: Traversing the current directory using
os.walk()
import os for root, dirs, files in os.walk("."): for filename in files: print(filename)
Using the Command Line via Subprocess
As already described in the article Parallel Processing in Python, the
subprocess module allows you to execute a system command, and collect its result. The system command we call in this case is the following one:
Example 1: Listing the files in the current directory
$ ls -p . | grep -v /$
The command
ls -p . lists directory files for the current directory, and adds the delimiter
/ at the end of the name of each subdirectory, which we'll need in the next step. The output of this call is piped to the
grep command that filters the data as we need it.
The parameters
-v /$ exclude all the names of entries that end with the delimiter
/. Actually,
/$ is a Regular Expression that matches all the strings that contain the character
/ as the very last character before the end of the string, which is represented by
$.
The
subprocess module allows to build real pipes, and to connect the input and output streams as you do on a command line. Calling the method
subprocess.Popen() opens a corresponding process, and defines the two parameters named stdin and stdout.
Listing 2 shows how to program that. The first variable
ls is defined as a process executing
ls -p . that outputs to a pipe. That's why the stdout channel is defined as
subprocess.PIPE. The second variable
grep is defined as a process, too, but executes the command
grep -v /$, instead.
To read the output of the
ls command from the pipe, the stdin channel of
grep is defined as
ls.stdout. Finally, the variable
endOfPipe reads the output of
grep from
grep.stdout that is printed to stdout element-wise in the
for-loop below. The output is seen in Example 2.
Listing 2: Defining two processes connected with a pipe
import subprocess # define the ls command ls = subprocess.Popen(["ls", "-p", "."], stdout=subprocess.PIPE, ) # define the grep command grep = subprocess.Popen(["grep", "-v", "/$"], stdin=ls.stdout, stdout=subprocess.PIPE, ) # read from the end of the pipe (stdout) endOfPipe = grep.stdout # output the files line by line for line in endOfPipe: print (line)
Example 2: Running the program
$ python find-files3.py find-files2.py find-files3.py find-files4.py ...
This solution works quite well with both Python 2 and 3, but can we improve it somehow? Let us have a look at the other variants, then.
Combining
os and
fnmatch
As you have seen before the solution using subprocesses is elegant but requires lots of code. Instead, let us combine the methods from the two modules
os, and
fnmatch. This variant works with Python 2 and 3, too.
As the first step, we import the two modules
os, and
fnmatch. Next, we define the directory we would like to list the files using
os.listdir(), as well as the pattern for which files to filter. In a
for loop we iterate over the list of entries stored in the variable
listOfFiles.
Finally, with the help of
fnmatch we filter for the entries we are looking for, and print the matching entries to stdout. Listing 3 contains the Python script, and Example 3 the corresponding output.
Listing 3: Listing files using os and fnmatch module
import os, fnmatch listOfFiles = os.listdir('.') pattern = "*.py" for entry in listOfFiles: if fnmatch.fnmatch(entry, pattern): print (entry)
Example 3: The output of Listing 3
$ python2 find-files.py find-files.py find-files2.py find-files3.py ...
Using
os.listdir() and Generators
In simple terms, a generator is a powerful iterator that keeps its state. To learn more about generators, check out one of our previous articles, Python Generators.
The following variant combines the
listdir() method of the
os module with a generator function. The code works with both versions 2 and 3 of Python.
As you may have noted before, the
listdir() method returns the list of entries for the given directory. The method
os.path.isfile() returns
True if the given entry is a file. The
yield operator quits the function but keeps the current state, and returns only the name of the entry detected as a file. This allows us to loop over the generator function (see Listing 4). The output is identical to the one from Example 3.
Listing 4: Combining
os.listdir() and a generator function
import os def files(path): for file in os.listdir(path): if os.path.isfile(os.path.join(path, file)): yield file for file in files("."): print (file)
Use
pathlib
The
pathlib module describes itself as a way to "Parse, build, test, and otherwise work on filenames and paths using an object-oriented API instead of low-level string operations". This sounds cool - let's do it. Starting with Python 3, the module belongs to the standard distribution.
In Listing 5, we first define the directory. The dot (".") defines the current directory. Next, the
iterdir() method returns an iterator that yields the names of all the files. In a
for loop we print the name of the files one after the other.
Listing 5: Reading directory contents with
pathlib
import pathlib # define the path currentDirectory = pathlib.Path('.') for currentFile in currentDirectory.iterdir(): print(currentFile)
Again, the output is identical to the one from Example 3.
As an alternative, we can retrieve files by matching their filenames by using something called a glob. This way we can only retrieve the files we want. For example, in the code below we only want to list the Python files in our directory, which we do by specifying "*.py" in the glob.
Listing 6: Using
pathlib with the
glob method
import pathlib # define the path currentDirectory = pathlib.Path('.') # define the pattern currentPattern = "*.py" for currentFile in currentDirectory.glob(currentPattern): print(currentFile)
Using
os.scandir()
In Python 3.6, a new method becomes available in the
os module. It is named
scandir(), and significantly simplifies the call to list files in a directory.
Having imported the
os module first, use the
getcwd() method to detect the current working directory, and save this value in the
path variable. Next,
scandir() returns a list of entries for this path, which we test for being a file using the
is_file() method.
Listing 7: Reading directory contents with
scandir()
import os # detect the current working directory path = os.getcwd() # read the entries with os.scandir(path) as listOfEntries: for entry in listOfEntries: # print all entries that are files if entry.is_file(): print(entry.name)
Again, the output of Listing 7 is identical to the one from Example 3.
Conclusion
There is disagreement which version is the best, which is the most elegant, and which is the most "pythonic" one. I like the simplicity of the
os.walk() method as well as the usage of both the
fnmatch and
pathlib modules.
The two versions with the processes/piping and the iterator require a deeper understanding of UNIX processes and Python knowledge, so they may not be best for all programmers due to their added (and unnecessary) complexity.
To find an answer to which version is the quickest one, the
timeit module is quite handy. This module counts the time that has elapsed between two events.
To compare all of our solutions without modifying them, we use a Python functionality: call the Python interpreter with the name of the module, and the appropriate Python code to be executed. To do that for all the Python scripts at once a shell script helps (Listing 8).
Listing 8: Evaluating the execution time using the
timeit module
#! /bin/bash for filename in *.py; do echo "$filename:" cat $filename | python3 -m timeit echo " " done
The tests were taken using Python 3.5.3. The result is as follows whereas
os.walk() gives the best result. Running the tests with Python 2 returns different values but does not change the order -
os.walk() is still on top of the list.
Acknowledgements
The author would like to thank Gerold Rupprecht for his support, and comments while preparing this article. | http://stackabuse.com/python-list-files-in-a-directory/ | CC-MAIN-2017-47 | refinedweb | 1,473 | 66.44 |
Sending Auto generated Emails through ASP.NET
In this article i am going to explain, how to send auto generated email through your Gmail credentials in ASP.NET. This is very simple code and you can use it in any .nET applications like sending an email to the users who have contacted you.
Sometimes in our applications we need to send automated emails to the users. Like while the registration, forgot password link and many more. Using this article we can achieve this very eaisly-
Create a simple ASPX page (like sample.aspx) and on the button click/pageload of the form you can write the following in sample.aspx.cs, If you want at button click mail should be sent, follow the below or if you want on the page load itself, mail should get delivered- write whole code on Page_Load method itself.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Net.Mail;
public partial class sample: System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
protected void submit_Click(object sender, EventArgs e)
{
try
{
MailMessage Msg = new MailMessage();
Msg.From = new MailAddress("XXXX@gmail.com");
// Recipient e-mail address.
Msg.To.Add("ashutosh@gmail.com");
Msg.Subject = "Alert For Contacted User!";
Msg.Body = "One user " + name.Text + " with EmailID "+emailid.Text+" and Contact # "+number.Text+" has contacted you rerading query "+description.Text+ ". plesae get in touch";
SmtpClient smtp = new SmtpClient();
smtp.Host = "smtp.gmail.com";
smtp.Port = 587;
//Sender mail id and password
smtp.Credentials = new System.Net.NetworkCredential("XXXXX@gmail.com", "XXXX");
smtp.EnableSsl = true;
smtp.Send(Msg);
Msg = null;
ClientScript.RegisterClientScriptBlock(this.GetType(), "myscript", "alert('Thank you for contacting us.We will get back to you soon!');", true);
//this.ClientScript.RegisterClientScriptBlock(this.GetType(), "Close", "window.close()", true);
}
catch (Exception ex)
{
Console.WriteLine("{0} Exception caught.", ex);
}
name.Text = "";
number.Text = "";
description.Text = "";
this.ClientScript.RegisterClientScriptBlock(this.GetType(), "Close", "window.close()", true);
}
protected void reset_Click(object sender, EventArgs e)
{
name.Text = "";
number.Text = "";
description.Text = "";
}
}
Here you need to use one additional reference for the mail in namespace-
using System.Net.Mail;
This will enable the mailing feature.
In this form, i have used 4 textbox for name, email, number and message.
Below are the some of the terms that i have used in the above code.
1. msg.from - is the email id through which you want to send the emails. If you want to send it dynamically like email id from textbox, just write id of the textbox.text.
2.Msg.To.Add- Email id to whom you want to send emails. You can also make this field dynamic same as above.
3.Msg.Subject- Subject line of the email. Can be done dynamic. Suppose in your for you have a textbox with id sub then make msg.subject-sub.text.
4.Msg.Body- whatever you want to write in the body of the mail.
5.smtp.Host- gateway is smtp
6.smtp.Credentials- write the credentials. or you can use default credentials also by setting defaultcredentials prperty to true.
Thanks,
Ashutosh Jha | https://www.dotnetspider.com/resources/45721-Sending-Auto-generated-Emails-through-ASPNET.aspx | CC-MAIN-2021-39 | refinedweb | 524 | 63.25 |
Is there any way to just check what the first letter of a string is in c#? i can't find anything that can help.
Answer by Rasmus Schlnsen
·
Oct 23, 2010 at 09:12 PM
You can access chars of a string like arrays:
String s = "tada";
if (s[0] == 't'){
Debug.Log("tada");
}
Be careful, this assumes s.Length > 0. If that assumptions might not hold, either check, or use:
if (s.StartsWith("t"))
which is more flexible too.
Answer by MortenK84
·
Oct 24, 2010 at 08:09 PM
C#:
String s = "tada";
Debug.Log("The first character of the string is: " + s.Substring(0, 1));
What the substring method does is retrieve a string within the string. The first parameter 0 is the starting index (starting position of the substring), and the number 1 is the amount of characters to grab.
Thank-you - after ensuring length is >1, works perfect!
Answer by Eric5h5
·
Oct 23, 2010 at 09:10 PM
var myString = "abc";
print (myString[0]);
Answer by Bravini
·
Oct 23, 2010 at 09:02 PM
slice the string then compare the result with what you want
sorry for being so pathetic but C# isn't my "best" language. So, i would go: if (myString.slice (put what here?)) { im looking to see if it starts with ! defining it as an admin command
myString.slice(0,1) should do it
Answer by SARWAN
·
Nov 21, 2012 at 04:13 PM
return (myString[0] >= 'A' && myString[0] <= 'Z') || (myString[0] >= 'a' && myString[0] <= .
The name 'Joystick' does not denote a valid type ('not found')
2
Answers
Dialogue & GUI Text String
1
Answer
Setting Scroll View Width GUILayout
1
Answer
PlayerPrefs Question
0
Answers to array
1
Answer | http://answers.unity3d.com/questions/31264/c-check-first-letter-of-string.html | CC-MAIN-2016-26 | refinedweb | 289 | 82.04 |
On Thu, 3 Feb 2005, Fruhwirth Clemens wrote:> First attempt:> > static inline int scatterwalk_needscratch(struct scatter_walk *walk, int> nbytes) {> return ((nbytes) <= (walk)->len_this_page &&> (((unsigned long)(walk)->data) & (PAGE_CACHE_SIZE - 1)) +> (nbytes) <= PAGE_CACHE_SIZE);> }> > While trying to improve this unreadable monster I noticed, that > (((unsigned long)(walk)->data) & (PAGE_CACHE_SIZE - 1)) is always equal> to walk->offset. walk->data and walk->offset always grows together (see> scatterwalk_copychunks), and when the bitwise AND-ing of walk->data with> PAGE_CACHE_SIZE-1 would result walk->offset to be zero, in just that> moment, walk->offset is set zero (see scatterwalk_pagedone). So, better:> > static inline int scatterwalk_needscratch(struct scatter_walk *walk, int> nbytes) > {> return (nbytes <= walk->len_this_page &&> (nbytes + walk->offset) <= PAGE_CACHE_SIZE);> }> This appears to be correct. Adam (cc'd) did some work on this code, andmay have some further observations.> Looks nicer, right? But in fact, it's redundant. walk->offset is never> intended to grow bigger than PAGE_CACHE_SIZE, and further it's illegal> to hand cryptoapi a scatterlist, where sg->offset is greater than> PAGE_CACHE_SIZE (I presume this from the calculations in> scatterwalk_start). Are these two conclusions correct, James? Yes, passing in an offset beyond the page size is wrong.Also, I don't know why PAGE_CACHE_SIZE is being used here instead ofPAGE_SIZE. Even though they're always the same now, I would suggestchanging all occurrences to PAGE_SIZE.- | http://lkml.org/lkml/2005/2/8/55 | CC-MAIN-2016-22 | refinedweb | 220 | 53.51 |
We're pleased to release Beats 6.3.0. Enjoy!
Here are the highlights:
Configure Beats via Kubernetes/Docker annotations
You probably got used to the fact that each 6.x minor release is making Kubernetes monitoring even nicer, so we couldn’t disappoint you with this one. The goodie that we have prepared in 6.3 is that you can now configure Beats not only via the Beats manifest files but also via Kubernetes annotations (or Docker labels) that are assigned to the monitored Pods.
To use this, enable Autodiscover with Hints enabled in the Beats configuration:
filebeat.autodiscover: providers: - type: kubernetes hints.enabled: true
Then, when creating a new deployment, you can use Kubernetes annotations to “hint” to the Beats how the new deployment should be monitored. For example, if you deploy an Nginx container, you can add the following Kubernetes annotations to it:
annotations: co.elastic.logs/module: nginx co.elastic.logs/fileset: access co.elastic.metrics/module: nginx co.elastic.metrics/period: 10s co.elastic.metrics/hosts: "${data.host}:8080"
When Filebeat and Metricbeat receive the notification that a new Pod is created, they retrieve the annotations above and start the respective Nginx modules with the given configuration. Any Beats settings can be modified this way, and it’s a great way of keeping the logging and monitoring configuration near the application deployment configuration.
Filebeat Syslog input
Starting with 6.3, you can send logs to Filebeat using the syslog protocol, over UDP or TCP. The internal Syslog parser is a state machine built with Ragel, which makes it both efficient and flexible enough to deal with the usual variations from the Syslog standard. For the moment, RFC 3164 is supported. RFC 5424 is planned for a future release.
Here is a sample configuration:
filebeat.inputs: - type: syslog protocol.tcp: # The host and port to receive the new event host: "localhost:9000" # Character used to split new message #line_delimiter: "\n" # Maximum size in bytes of the message received over TCP #max_message_size: 20MiB # The number of seconds of inactivity before a remote connection is closed. #timeout: 300s
Spooling to disk (Beta)
Starting with this release, all Beats get an optional disk queue where they can spool their events..
The spooling to disk feature can be used to provide “at least once” guarantees for Beats like Metricbeat and Auditbeat, that don’t read from a natural queue (like Filebeat does when tailing files).
This feature is currently in Beta, so please avoid it in production, but do try it on non-production systems and give us feedback on it.
Add host metadata
Everyone loves Beats processors like
add_cloud_metadata or
add_kubernetes_metadata. Add a line in your Filebeat or Metricbeat configs, and suddenly all events are populated with things like the instance type, region, kubernetes namespace, and so on. So we’ve asked ourselves why don’t we have something similar for non-cloud non-kubernetes hosts.
The new
add_host_metadata processor adds the following fields to your event:
- host.name
- host.id
- host.architecture
- host.os.platform
- host.os.version
- host.os.family
These fields can be used in any filtering and aggregation in Kibana.
To support the new fields, we had to add a new object to the index template. This change may cause mapping conflicts for some Logstash users, even if you aren’t using the new processor. For more information, see the Beats breaking changes documentation.
Wait, there’s more: IIS, Logstash, MongoDB, Etcd modules
The 6.3 release increases our collection of Filebeat and Metricbeat modules. Filebeat comes with the following new modules:
- MongoDB
- Logstash
- IIS
.png)
Metricbeat comes with the following new modules:
- Etcd
- Graphite
- Logstash
- Munin
Feedback
If you want to make use of the new features added in Beats 6.3.0, please download it, install it, and let us know what you think on Twitter (@elastic) or in our forum. | https://www.elastic.co/blog/beats-6-3-0-released | CC-MAIN-2019-22 | refinedweb | 648 | 55.95 |
Java programming with JNI
About this tutorial
The Java Native Interface (JNI) is a native programming interface that is part of the Java Software Development Kit (SDK). JNI lets Java code use code and code libraries written in other languages, such as C and C++. The Invocation API, which is part of JNI, can be used to embed a Java virtual machine (JVM) into native applications, thereby allowing programmers to call Java code from within native code.
This tutorial deals with the two most common applications of JNI: calling C/C++ code from Java programs, and calling Java code from C/C++ programs. We'll cover both the essentials of the Java Native Interface and some of the more advanced programming challenges that can arise.
Should I take this tutorial?
This tutorial will walk you through the steps of using the Java Native Interface. You'll learn how to call native C/C++ code from within a Java application and how to call Java code from within a native C/C++ application.
All the examples use Java, C, and C++ code, and are written to be portable to both Windows and UNIX-based platforms. To follow the examples, you must have some experience programming in the Java language. In addition, you will also need some experience programming in C or C++. Strictly speaking, a JNI solution could be broken down between Java programming tasks and C/C++ programming tasks, with separate programmers doing each task. However, to fully understand how JNI works in both programming environments, you'll need to be able to understand both the Java and C/C++ code.
We'll also cover a number of advanced topics, including exception handling and multithreading with native methods. To get the most out of this part of the tutorial, you should be familiar with the Java platform's security model and have some experience in multithreaded application development.
The section on Advanced topics is separate from the more basic step-by-step introduction to JNI. Beginning Java programmers may benefit from taking the first two parts of the tutorial now and returning to the advanced topics at a later time.
Tools and components
To run the examples in this tutorial, you will need the following tools and components:
- A Java compiler:
javac.exeships with the SDK.
- A Java virtual machine (JVM):
java.exeships with the SDK.
- A native method C file generator:
javah.exeships with the SDK.
- Library files and native header files that define JNI. The jni.h C header file, jvm.lib, and jvm.dll or jvm.so files all ship with the SDK.
- A C and C++ compiler that can create a shared library. The two most common C compilers are Visual C++ for Windows and
ccfor UNIX-based systems.
Although you may use any development environment you like, the examples we'll work with in this tutorial were written using the standard tools and components that ship with the SDK. This tutorial specifically addresses Sun's implementation of JNI, which should be regarded as the standard for JNI solutions. The details of other JNI implementations are not addressed in this tutorial.
Additional considerations
In the Java 2 SDK, the JVM and run-time support are located in the shared library file named jvm.dll (Windows) or libjvm.so (UNIX). In the Java 1.1 JDK, the JVM and run-time support were located in the shared library file named javai.dll (Windows) or libjava.so (UNIX). The version 1.1 shared libraries contained the runtime and some native methods for the class libraries, but in version 1.2, the runtime is removed and the native methods are in java.dll and libjava.so. This change is important in Java code that:
- Is written using non-JNI native methods (as with the old native method interface from the JDK 1.0 JDK)
- Uses an embedded JVM through the JNI Invocation Interface
In both cases, you'll need to relink your native libraries before they can be used with version 1.2. Note that this change should not affect JNI programmers implementing native methods -- only JNI code that invokes a JVM through the Invocation API.
If you use the jni.h file that comes with the SDK/JDK, that header file will use the default JVM in the JDK/SDK installation directory (jvm.dll or libjvm.so). Any implementation of a Java platform that supports JNI should do the same thing, or allow you to specify a JVM shared library; however the details of how this is done may be specific to that Java Platform/JVM implementation. Indeed, many implementations of JVMs do not support JNI at all.
Calling C/C++ code from Java programs:
1. public class Sample1 2. { 3. public native int intMethod(int n); 4. public native boolean booleanMethod(boolean bool); 5. public native String stringMethod(String text); 6. public native int intArrayMethod(int[] intArray); 7. 8. public static void main(String[] args) 9. { 10. System.loadLibrary("Sample1"); 11. Sample1 sample = new Sample1(); 12. int square = sample.intMethod(5); 13. boolean bool = sample.booleanMethod(true); 14. String text = sample.stringMethod("JAVA"); 15. int sum = sample.intArrayMethod( 16. new int[]{1,1,2,3,5,8,13} ); 17. 18. System.out.println("intMethod: " + square); 19. System.out.println("booleanMethod: " + bool); 20. System.out.println("stringMethod: " + text); 21. System.out.println("intArrayMethod: " + sum); 22. }:
1. /* DO NOT EDIT THIS FILE - it is machine generated */ 2. #include <jni.h> 3. /* Header for class Sample1 */ 4. 5. #ifndef _Included_Sample1 6. #define _Included_Sample1 7. #ifdef __cplusplus 8. extern "C" { 9. #endif 10. 11. JNIEXPORT jint JNICALL Java_Sample1_intMethod 12. (JNIEnv *, jobject, jint); 13. 14. JNIEXPORT jboolean JNICALL Java_Sample1_booleanMethod 15. (JNIEnv *, jobject, jboolean); 16. 17. JNIEXPORT jstring JNICALL Java_Sample1_stringMethod 18. (JNIEnv *, jobject, jstring); 19. 20. JNIEXPORT jint JNICALL Java_Sample1_intArrayMethod 21. (JNIEnv *, jobject, jintArray); 22. 23. #ifdef __cplusplus 24. } 25. #endif 26. . These types are fully explained in Appendix A: JNI(env, string, 0); 17. char cap[128]; 18. strcpy(cap, str); 19. (*env)->ReleaseStringUTFChars(env, string, str); 20. return (*env)->NewStringUTF(env, strupr(cap)); 21. } 22. 23. JNIEXPORT jint JNICALL Java_Sample1_intArrayMethod 24. (JNIEnv *env, jobject obj, jintArray array) { 25. int i, sum = 0; 26. jsize len = (*env)->GetArrayLength(env, array); 27. jint *body = (*env)->GetIntArrayElements(env, array, 0); 28. for (i=0; i<len; i++) 29. { sum += body[i]; 30. } 31. (*env)->ReleaseIntArrayElements(env, array, body, 0); 32. return sum; 33. } 34. 35. void main(){}
The C++ function implementation
And here's Sample1.cpp, the C++ implementation:(string, 0); 17. char cap[128]; 18. strcpy(cap, str); 19. env->ReleaseStringUTFChars(string, str); 20. return env->NewStringUTF(strupr(cap)); 21. } 22. 23. JNIEXPORT jint JNICALL Java_Sample1_intArrayMethod 24. (JNIEnv *env, jobject obj, jintArray array) { 25. int i, sum = 0; 26. jsize len = env->GetArrayLength(array); 27. jint *body = env->GetIntArrayElements(array, 0); 28. for (i=0; i<len; i++) 29. { sum += body[i]; 30. } 31. env->ReleaseIntArrayElements(array, body, 0); 32. return sum; 33. } 34. 35. void main(){}:
java Sample1
When we run the
Sample1.class program, we should get the
following result:
PROMPT>java Sample1 intMethod: 25 booleanMethod: false stringMethod: JAVA intArrayMethod: 33 PROMPT>.
Calling Java code from C/C++ programs
Overview
JNI allows you to invoke Java class methods from within native code. Often, to do this, you must create and initialize a JVM within the native code using the Invocation API. The following are typical situations where you might decide to call Java code from C/C++ code:
- You want to implement platform-independent portions of code for functionality that will be used across multiple platforms.
- You have code or code libraries written in the Java language that you need to access in native applications.
- You want to take advantage of the standard Java class library from native code.
Four steps to call Java code from a C/C++ program
The four steps in the process of calling Java methods from C/C++ are as follows:
- Write the Java code. This step consists of writing the Java class or classes that implement (or call other methods that implement) the functionality you want to access.
- Compile the Java code. The Java class or classes must be successfully compiled to bytecode before they can be used.
- Write the C/C++ code. This code will create and instantiate a JVM and call the correct Java methods.
- Run the native C/C++ application. We'll run the application to see if it works. We'll also go over some tips for dealing with common errors.
Step 1: Write the Java code
We start by writing the Java source code file or files, which will implement the functionality we want to make available to the native C/C++ code.
Our Java code example, Sample2.java, is shown below:
1. public class Sample2 2. { 3. public static int intMethod(int n) { 4. return n*n; 5. } 6. 7. public static boolean booleanMethod(boolean bool) { 8. return !bool; 9. } 10. }
Note that Sample2.java implements two
static Java methods,
intMethod(int n) and
booleanMethod(boolean bool)
(lines 3 and 7 respectively).
static methods are class
methods that are not associated with object instances. It is easier to
call
static methods because we do not have to instantiate an
object to invoke them.
Step 2: Compile the Java code
Next, we compile the Java code down to bytecode. One way to do this is to
use the Java compiler,
javac, which comes with the SDK. The
command to use is:
javac Sample1.java
Step 3: Write the C/C++ code
All Java bytecode must be executed in a JVM, even when running in a native application. So our C/C++ application must include calls to create a JVM and to initialize it. To assist us, the SDK includes a JVM as a shared library file (jvm.dll or jvm.so), which can be embedded into native applications.
We'll start with a look at the complete code for both the C and C++ applications, then compare the two.
A C application with embedded JVM
Sample2.c is a simple. }
A C++ application with embedded JVM
Sample2.cpp is a. }
C and C++ implementations compared
The C and C++ code. Thus, these two lines of code access the same
function, but the syntax is specialized for each language, as shown
below.
A closer look at the C application
We've just produced a lot of code, but what does it all do? Before we move on to Step 4, let's take a closer look at the code for our C application. We'll walk through the essential steps of preparing a native application to process Java code, embedding a JVM in a native application, then finding and calling a Java method from within that application.
Include the jni.h file
We start by including the jni.h C header file in the C application, as shown in the code sample below.
#include <jni.h>
The jni.h file contains all the type and function definitions we need for JNI on the C side.
Declare the variables
Next, we declare all the variables we want to use in the program. The
JavaVMOption options[] holds various optional settings for
the JVM. When declaring variables, be sure that you declare the
JavaVMOption options[] array large enough to hold all the
options you want to use. In this case, the only option we're using is the
classpath option. We set the classpath to the current directory because in
this example all of our files are in the same directory. You can set the
classpath to point to any directory structure you would like to use.
Here's the code to declare the variables for Sample2.c:
JavaVMOption options[1]; JNIEnv *env; JavaVM *jvm; JavaVMInitArgs vm_args;
Notes:
JNIEnv *envrepresents JNI execution environment.
JavaVM jvmis a pointer to the JVM. We use this primarily to create, initialize, and destroy the JVM.
JavaVMInitArgs vm_argsrepresents various JVM arguments that we can use to initialize our JVM.
Set the initialization arguments
The
JavaVMInitArgs structure represents initialization
arguments for the JVM. You can use these arguments to customize the
runtime environment before you execute your Java code. As you can see, the
options are one argument and the Java version is another. We set these
arguments as follows:
vm_args.version = JNI_VERSION_1_2; vm_args.nOptions = 1; vm_args.options = options;
Set the classpath
Next, we set the classpath for the JVM, to enable it to find the required Java classes. In this particular case, we set the classpath to the current directory, because the Sample2.class and Sample2.exe are located in the same directory. The code we use to set the classpath for Sample2.c is shown below:
options[0].optionString = "-Djava.class.path=."; // same text as command-line options for the java.exe JVM
Set aside memory for vm_args
Before we can use
vm_args we need to set aside some memory for
it. Once we've set the memory, we can set the version and option
arguments, as shown below:
memset(&vm_args, 0, sizeof(vm_args)); // set aside enough memory for vm_args vm_args.version = JNI_VERSION_1_2; // version of Java platform vm_args.nOptions = 1; // same as size of options[1] vm_args.options = options;
Create the JVM
With all the setup taken care of, we're ready to create a JVM. We start with a call to the method:
JNI_CreateJavaVM(JavaVM **jvm, void** env, JavaVMInitArgs **vm_args)
This method returns zero if successful or
JNI_ERR if the JVM
could not be created.
Find and load the Java classes
Once we've created our JVM, we're ready to begin running Java code in the
native application. First, we need to find and load our Java class, using
the
FindClass() function, shown here:
cls = (*env)->FindClass(env, "Sample2");
The
cls variable stores the result of the
FindClass() function. If the class is found, the
cls variable represents a handle to the Java class. If the
class cannot be found,
cls will be zero.
Find a Java method
Next, we want to find a method inside of the class using the
GetStaticMethodID() function. We want to find the method
intMethod, which takes an
int parameter and
returns an
int. Here's the code to find
intMethod:
mid = (*env)->GetStaticMethodID(env, cls, "intMethod", "(I)I");
The
mid variable stores the result of the
GetStaticMethodID() function. If the method is found, the
mid variable represents a handle to the method. If the method
cannot be found,
mid will be zero.
Remember that in this example, we are calling
static Java
methods. That is why we're using the
GetStaticMethodID()
function. The
GetMethodID() function does the same thing, but
it is used to find instance methods.
If we were calling a constructor, the name of the method would have been "<init>". To learn more about calling a constructor, see Error handling. To learn more about the code used to specify parameter types and about how JNI types map to the Java primitive types, see Appendices .
Call a Java method
Finally, we call the Java method, as shown below:
square = (*env)->CallStaticIntMethod(env, cls, mid, 5);
The
CallStaticIntMethod() method takes
cls
(representing our class),
mid (representing our method), and
the parameter or parameters for the method. In this case the parameter is
int 5.
You will also run across methods of the types
CallStaticXXXMethod() and
CallXXXMethod(). These
call static methods and member methods, respectively, replacing the
variable (
XXX) with the return type for the method (for
example,
Object,
Boolean,
Byte,
Char,
Int,
Long, and so on).
Step 4: Run the application
Now we're ready to run the C application and make sure that the code works correctly. When you run Sample2.exe you should get a result like the following:
PROMPT>Sample2 Result of intMethod: 25 Result of booleanMethod: 0 PROMPT>
Troubleshooting
JNI's Invocation API is somewhat cumbersome because it is defined in C, a language with minimal object-oriented programming support. As a result, it is easy to run into problems. Below is a checklist that may help you avoid some of the more common errors.
- Always ensure that references are properly set. For example, when creating a JVM with the
JNI_CreateJavaVM()method, make sure it returns a zero. Also make sure that references set with the
FindClass()and
GetMethodID()methods are not zero before you use them.
- Check to see that your method names are spelled correctly and that you properly mangled the method signature. Also be sure that you use
CallStaticXXXMethod()for static methods and
CallXXXMethod()for member methods.
- Make sure you initialize the JVM with any special arguments or options your Java class may need. For example, if your Java class requires a great deal of memory, you may need to increase the maximum heap size option.
- Always be sure to set the classpath properly. A native application using an embedded JVM must be able to find the jvm.dll or jvm.so shared library.
Conclusion
Calling Java methods from C is relatively straightforward for experienced C programmers, although it does require fairly advanced quasi-object-oriented programming techniques. Although JNI supports both C and C++, the C++ interface is slightly cleaner and is generally preferred over the C interface.
One important point to remember is that a single JVM can be used to load and execute multiple classes and methods. Creating and destroying a JVM every time you interact with Java from native code can waste resources and decrease performance.
Advanced topics
Overview
Calling native code from within a Java program compromises the Java program's portability and security. Although the compiled Java bytecode remains highly portable, the native code must be recompiled for each platform on which you intend to run the application. The native code also executes outside of the JVM, so it is not necessarily constrained by the same security protocols as Java code.
Calling Java code from within a native program is also complicated. Because the Java language is object-oriented, calling Java code from a native application typically involves object-oriented techniques. In native languages that have no support or limited support for object-oriented programming, such as C, calling Java methods can be problematic. In this section, we'll explore some of the complexities that arise when working with JNI, and look at ways to work around them.
Java strings versus C strings
Java strings are stored as sequences of 16-bit Unicode characters, while C strings are stored as sequences of 8-bit null-terminated characters. JNI provides several useful functions for converting between and manipulating Java strings and C strings. The code snippet below demonstrates how to convert C strings to Java strings:
1. /* Convert a C string to a Java String. */ 2. char[] str = "To be or not to be.\n"; 3. jstring jstr = (*env)->NewStringUTF(env, str);
Next, we'll look at the code to convert Java strings to C strings. Note the
call to the
ReleaseStringUTFChars() function on line 5. You
should use this function to release Java strings when you're no longer
using them. Be sure you always release your strings when the native code
no longer needs to reference them. Failure to do so could cause a memory
leak.
1. /* Convert a Java String into a C string. */ 2. char buf[128; 3. const char *newString = (*env)->GetStringUTFChars(env, jstr, 0); 4. ... 5. (*env)->ReleaseStringUTFChars(env, jstr, newString);
Java arrays versus C arrays
Like strings, Java arrays and C arrays are represented differently in memory. Fortunately, a set of JNI functions provides you with pointers to the elements in arrays. The image below shows how Java arrays are mapped to the JNI C types.
The C type
jarray represents a generic array. In C, all of the
array types are really just type synonyms of
jobject. In C++,
however, all of the array types inherit from
jarray, which in
turn inherits from
jobject . See Appendix A: JNI types for an inheritance diagram of all the C
type objects.
s
Working with arrays
Generally, the first thing you want to do when dealing with an array is to
determine its size. For this, you should use the
GetArrayLength() function, which returns a
jsize
representing the array's size.
Next, you'll want to obtain a pointer to the array's elements. You can
access elements in an array using the
GetXXXArrayElement()
and
SetXXXArrayElement() functions (replace the
XXX in the method name according to the type of the array:
Object,
Boolean,
Byte,
Char,
Int,
Long, and so on).
When the native code is finished using a Java array, it must release it
with a call to the function
ReleaseXXXArrayElements().
Otherwise, a memory leak may result. The code snippet below shows how to
loop through an array of integers and up all the elements:
1. /* Looping through the elements in an array. */ 2. int* elem = (*env)->GetIntArrayElements(env, intArray, 0); 3. for (i=0; I < (*env)->GetIntArrayLength(env, intArray); i++) 4. sum += elem[i] 5. (*env)->ReleaseIntArrayElements(env, intArray, elem, 0);
Local versus global references
When programming with JNI you will be required to use references to Java objects. By default, JNI creates local references to ensure that they are liable for garbage collection. Because of this, you may unintentionally write illegal code by trying to store away a local reference so that you can reuse it later, as shown in the code sample below:
1. /* This code is invalid! */ 2. static jmethodID mid; 3. 4. JNIEXPORT jstring JNICALL 5. Java_Sample1_accessMethod(JNIEnv *env, jobject obj) 6. { 7. ... 8. cls = (*env)->GetObjectClass(env, obj); 9. if (cls != 0) 10. mid = (*env)->GetStaticMethodID(env, cls, "addInt", "(I)I"); 11. ... 12. }
This code is not valid because of line 10.
mid is a
methodID and
GetStaticMethodID() returns a
methodID. The
methodID returned is a local
reference, however, and you should not assign a local reference to a
global reference. And
mid is a global reference.
After the
Java_Sample1_accessMethod() returns, the
mid reference is no longer valid because it was assigned a
local reference that is now out of scope. Trying to use
mid
will result in either the wrong results or a crash of the JVM.
Creating a global reference
To correct this problem, you need to create and use a global reference. A global reference will remain valid until you explicitly free it, which you must remember to do. Failure to free the reference could cause a memory leak.
Create a global reference with
NewGlobalRef() and delete it
with
DeleteGlobalRef(), as shown in the code sample
below:
1. /* This code is valid! */ 2. static jmethodID mid; 3. 4. JNIEXPORT jstring JNICALL 5. Java_Sample1_accessMethod(JNIEnv *env, jobject obj) 6. { 7. ... 8. cls = (*env)->GetObjectClass(env, obj); 9. if (cls != 0) 10. { 11. mid1 = (*env)->GetStaticMethodID(env, cls, "addInt", "(I)I"); 12. mid = (*env)->NewGlobalRef(env, mid1); 13. ... 14. }
Error handling
Using native methods in Java programs breaks the Java security model in some fundamental ways. Because Java programs run in a controlled runtime system (the JVM), the designers of the Java platform decided to help the programmer by checking common runtime errors like array indices, out-of-bounds errors, and null pointer errors. C and C++, on the other hand, use no such runtime error checking, so native method programmers must handle all error conditions that would otherwise be caught in the JVM at runtime.
For example, it is common and correct practice in Java programs to report errors to the JVM by throwing an exception. C has no exceptions, so instead you must use the exception handling functions of JNI.
JNI's exception handling functions
There are two ways to throw an exception in the native code: you can call
the
Throw() function or the
ThrowNew() function.
Before calling
Throw(), you first need to create an object of
type
Throwable. By calling
ThrowNew() you can
skip this step because this function creates the object for you. In the
example code snippet below, we throw an
IOException using
both functions:
1. /* Create the Throwable object. */ 2. jclass cls = (*env)->FindClass(env, "java/io/IOException"); 3. jmethodID mid = (*env)->GetMethodID(env, cls, "<init>", "()V"); 4. jthrowable e = (*env)->NewObject(env, cls, mid); 5. 6. /* Now throw the exception */ 7. (*env)->Throw(env, e); 8. ... 9. 10. /* Here we do it all in one step and provide a message*/ 11. (*env)->ThrowNew(env, 12. (*env)->FindClass("java/io/IOException"), 13. "An IOException occurred!");
The
Throw() and
ThrowNew() functions do not
interrupt the flow of control in the native method. The exception will not
actually be thrown in the JVM until the native method returns. In C you
cannot use the
Throw() and
ThrowNew() functions
to immediately exit a method on error conditions, as you can in Java
programs by using the throw statement. Instead, you need to use a return
statement right after the
Throw() and
ThrowNew()
functions to exit the native method at a point of error.
JNI's exception catching functions
You may also need to catch exceptions when calling Java from C or C++. Many
JNI functions throw exceptions that you may want to catch. The
ExceptionCheck() function returns a
jboolean
indicating whether or not an exception was thrown, while the
ExceptionOccured() method returns a
jthrowable
reference to the current exception (or
NULL if no exception
was thrown).
If you're catching exceptions, you may be handling exceptions, in which
case you need to clear out the exception in the JVM. You can do this using
the
ExceptionClear() function. The
ExceptionDescribed() function is used to display a debugging
message for an exception.
Multithreading in native methods
One of the more advanced issues you'll face when working with JNI is multithreading with native methods. The Java platform is implemented as a multithreaded system, even when running on platforms that don't necessarily support multithreading; so the onus is on you to ensure that your native functions are thread safe.
In Java programs, you can implement thread-safe code by using
synchronized statements. The syntax of the
synchronized statements allows you to obtain a lock on an
object. As long as you're in the
synchronized block, you can
perform whatever data manipulation you like without fear that another
thread may sneak in and access the object for which you have the lock.
JNI provides a similar structure using the
MonitorEnter() and
MonitorExit() functions. You obtain a monitor (lock) on the
object you pass into the
MonitorEnter() function and you keep
this lock until you release it with the
MonitorExit()
function. All of the code between the
MonitorEnter() and
MonitorExit() functions is guaranteed to be thread safe for
the object you locked.
Synchronization in native methods
The table below shows how to synchronize a block of code in Java, C, and
C++. As you can see, the C and C++ functions are similar to the
synchronized statement in the Java code.
Using
synchronized with native
methods
Another way to ensure that your native method is synchronized is to use the
synchronized keyword when you declare your
native method in a Java class.
Using the
synchronized keyword will ensure that whenever the
native method is called from a Java program, it will be
synchronized. Although it is a good idea to mark thread-safe
native methods with the
synchronized keyword, it is generally
best to always implement synchronization in the native method
implementation. The primary reasons for this are as follows:
- The C or C++ code is distinct from the Java native method declaration, so if the method declaration changes (that is, if the
synchronizedkeyword is ever removed) the method may suddenly no longer be thread safe.
- If anyone ever codes other native methods (or other C or C++ functions) that use the function, they may not be aware that native implementation isn't thread safe.
- If the function is used outside of a Java program as a normal C function it will not be thread safe.
Other synchronization techniques
The
Object.wait(),
Object.notify(), and
Object.notifyAll() methods also support thread
synchronization. Since all Java objects have the
Object class
as a parent class, all Java objects have these methods. You can call these
methods from the native code as you would any other method, and use them
in the same way you would use them in Java code to implement thread
synchronization.
Wrap-up
Summary
The Java Native Interface is a well-designed and well-integrated API in the Java platform. It is designed to allow you to incorporate native code into Java programs as well as providing you a way to use Java code in programs written in other programming languages.
Using JNI almost always breaks the portability of your Java code. When calling native methods from Java programs, you will need to distribute native shared library files for every platform on which you intend to run your program. On the other hand, calling Java code from native programs can actually improve the portability of your application.
Appendices
Appendix A: JNI types
JNI uses several natively defined C types that map to Java types. These types can be divided into two categories: primitive types and pseudo-classes. The pseudo-classes are implemented as structures in C, but they are real classes in C++.
The Java primitive types map directly to C platform-dependent types, as shown here:
The C type
jarray represents a generic array. In C, all of the
array types are really just type synonyms of
jobject. In C++,
however, all of the array types inherit from
jarray, which in
turn inherits from
jobject. The following table shows how the
Java array types map to JNI C array types.
Here is an object tree that shows how the JNI pseudo-classes are related.
Appendix B: JNI method signature encoding
Native Java method parameter types are rendered, or mangled, into native code using the encoding specified in the table below.
Notes:
- The semicolon at the end of the class type L expression is the terminator of the type expression, not a separator between expressions.
- You must use a forward slash (/) instead of a dot (.) to separate the package and class name. To specify an array type use an open bracket ([). For example, the Java method:
boolean print(String[] parms, int n)
has the following mangled signature:
([Ljava/lang/Sting;I)Z
Downloadable resources
Related topics
- The C++ Programming Language, Third Edition
- Jamsa's C/C++ Programmer's Bible
- Mastering Object-Oriented Design in C++
- Structured and Object-Oriented Techniques: An Introduction Using C++
- Complete source files, j-jni-source.zip, for this tutorial | https://www.ibm.com/developerworks/java/tutorials/j-jni/j-jni.html | CC-MAIN-2017-26 | refinedweb | 5,091 | 57.98 |
Created on 2012-07-16 10:01 by sbt, last changed 2012-08-14 00:01 by sbt. This issue is now closed.
With unix, and a source build, sysconfig.get_config_var('srcdir') and sysconfig.get_path('include') misbehave:
user@mint-vm ~/Repos/cpython $ cd /
user@mint-vm / $ ~/Repos/cpython/python
Python 3.3.0b1 (default:671894ae19a2, Jul 16 2012, 10:43:27)
[GCC 4.5.2] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sysconfig
>>> sysconfig.get_config_var('srcdir')
'/'
>>> sysconfig.get_path('include')
'//Include'
The problem seems to be the else clause of
if 'srcdir' not in _CONFIG_VARS:
_CONFIG_VARS['srcdir'] = _PROJECT_BASE
else:
_CONFIG_VARS['srcdir'] = _safe_realpath(_CONFIG_VARS['srcdir'])
The else clause (in slightly modified form) was introduced in 356d0ea8ea34, and it turns a relative path into an absolute path, using the current working directory as a base.
For me, simply removing the line allows the absolute path to be calculated correctly a few lines later on.
I don't know what problem 356d0ea8ea34 was intended to fix.
I don't recall what the issue was the resulted in the check-in that you mention. Sadly enough it is not-trivial to find that check-in I mention due to the migration from Subversion to Mercurial.
How was python itself configured (configure command line)? What OS are you running on? Given the shell prompt I'd say Mint Linux. And finally, is '~/Repos/cpython/python' a checkout or installed location (that is, did you run 'make install')?
Based on code inspection I'd say that your change is correct, and my change only works when running from the build directory.
> I don't recall what the issue was the resulted in the check-in that you
> mention.
I think it was. The issue was about having srcdir != builddir. The initial patch caused a test failure, and 356d0ea8ea34 fixed (or at least silenced) the failure.
> How was python itself configured (configure command line)?
I tried it with both
./configure
make
and
mdkir release
cd release
../configure
make
It fails with both.
> What OS are you running on? Given the shell prompt I'd say Mint Linux.
Yes (in a VM).
> And finally, is '~/Repos/cpython/python' a checkout or installed
> location (that is, did you run 'make install')?
It is a checkout.
The argument passed to _safe_realpath() (either "." or ".." in my case) should be interpreted relative to the directory containing the Makefile. But os.path.realpath() assumes that its argument is either absolute or relative to os.getcwd(). It therefore returns the wrong absolute path.
It is actually simple to find the revision: :)
I have to add that I’m quite confused by srcdir vs. projectbase. There are a handful of open bugs related to sysconfig and built but uninstalled Pythons, and many commits changing code to use srcdir or projectbase after empirical testing or buildbot failures. :/
srcdir vs. project base is quite easy: srcdir is the directory containing the source files, the project base is where you ran configure. These are the same if you run configure in the root of a checkout, but don't have to be, for example when you do:
$ mkdir buildroot
$ cd buildroot
$ ../configure # ...
Now de base directory is the 'buildroot' directory, while srcdir is its parent directory.
Issue 15322 is a recently filed bug regarding srcdir: "sysconfig.get_config_var('srcdir') returns unexpected value"
In the attached patch _safe_realpath() is only called after calculating the absolute path for srcdir.
Updated patch which clarifies that for an installed python on a posix system, get_config_var('srcdir') == get_path('stdlib').
Eg, if sys.executable == '/usr/local/bin/python3.3' then get_config_var('srcdir') == '/usr/local/lib/python3.3'.
This is a little arbitrary, but seems as sensible a value as any other. (Or maybe it would be better to have get_config_var('srcdir') == None instead.)
> This is a little arbitrary, but seems as sensible a value as any other.
> (Or maybe it would be better to have get_config_var('srcdir') == None
> instead.)
'srcdir' is problematic for any installed build. Once "make install" has been performed, there is no obligation to keep the original source and build dirs around anymore. For Pythons installed on other machines via a binary installer, like the python.org OS X ones, some of the paths returned by sysconfig are not meaningful on the installed machine. For an OS X framework build, the Makefile and friends are copied into a 'config' directory that is created within the installed framework. So, with the patch, the contents of that directory (returned by the patched 'srcdir' value) is:
['Makefile',
'Setup',
'Setup.config',
'Setup.local',
'config.c',
'config.c.in',
'install-sh',
'libpython3.3.a',
'libpython3.3.dylib',
'makesetup',
'python.o']
Is that a meaningful surrogate for the build 'srcdir'?
Beyond that, I don't understand why the patch behavior depends on whether the srcdir is an absolute path or not. I often use absolute paths to configure a build. If not in a build directory, 'srcdir' should always return either the proposed value based on what get_makefile_filename() returns or it should return None. I don't have a strong opinion at the moment about which. One factor should be an inspection and running of all of the tests. A quick grep of Lib/ didn't find many references to 'srcdir'.
One other point: distutils still has its own copy of sysconfig. Strong consideration should be given to making a similar change there.
> Beyond that, I don't understand why the patch behavior depends on
> whether the srcdir is an absolute path or not.
The os.path.isabs() test is actually redundant since os.path.join(base, srcdir) == srcdir if srcdir is an absolute path. I only added that test to be explicit about what happens if the original value is an absolute path.
> I often use absolute paths to configure a build. If not in a build
> directory, 'srcdir' should always return either the proposed value
> based on what get_makefile_filename() returns or it should return
> None.
Removing the isabs() test would not change the calculated value as I indicated above.
Using None would be the sanest option, but I don't know if any current code depends on the value being a string.
> One other point: distutils still has its own copy of sysconfig.
> Strong consideration should be given to making a similar change there.
For a source build, distutils.sysconfig.get_config_var('srcdir') gives the right answer as an absolute path, *except* when the current working directory contains sys.executable. I think it should always return an absolute path. The fact that currently it does not probably explains the "mysteriously" comment below from distutils/test/support.py:
def _get_xxmodule_path():
srcdir = sysconfig.get_config_var('srcdir')
candidates = [
# use installed copy if available
os.path.join(os.path.dirname(__file__), 'xxmodule.c'),
# otherwise try using copy from build directory
os.path.join(srcdir, 'Modules', 'xxmodule.c'),
# srcdir mysteriously can be $srcdir/Lib/distutils/tests when
# this file is run from its parent directory, so walk up the
# tree to find the real srcdir
os.path.join(srcdir, '..', '..', '..', 'Modules', 'xxmodule.c'),
]
for path in candidates:
if os.path.exists(path):
return path
BTW, I was wrong in my earlier message when I claimed that srcdir == get_path('stdlib') for an installed python. That is only true if the relative srcdir is '..'. The attached patch removes that check from the unit tests.
Upon further consideration, while it sounds appealing, perhaps returning None is not the better choice. As far as I know, up until now all config vars are either of type str or type int. Adding None to the mix might be asking for trouble.
With no patch, running from an installed framework build:
>>>'
>>> dsc.get_config_var('srcdir')
'.'
With the latest patch, as above:
>>>/fw/root/Library/Frameworks/pytest_10_7.framework/Versions/3.3/lib/python3.3/config-3.3dm'
>>> dsc.get_config_var('srcdir')
'.'
The patched results looks OK except, of course, for the discrepancy with distutils.sysconfig. I think we should fix that and get this all into 3.3.0. Otherwise we'll be stuck with the current broken behavior until 3.4 at the earliest.
One nit comment on the currrent patch: s/"will not effect it"/"will not affect it" (one of those gotchas in English).
I should have noted that, in the above tests, distutils.sysconfig.get_makefile_filename() is already doing the right thing:
>>> dsc.get_makefile_filename()
'/py/dev/default/b10.7_t10.7_x4.3_cclang_d/fw/root/Library/Frameworks/pytest_10_7.framework/Versions/3.3/lib/python3.3/config-3.3dm/Makefile'
[70312 refs]
>>> sc.get_makefile_filename() == dsc.get_makefile_filename()
True
Agree on fixing this for 3.3, if it’s not possible to backport to all stable branches. Will review.
Here is an updated patch which also modifies distutils.sysconfig.
For "installed" pythons on posix systems it makes
get_config_var('srcdir') == os.path.dirname(get_makefile_filename())
(The older patches would give the same result only if the relative srcdir was '.')
Forgot to remove some unnecessary code in patch.
I'd make get_config_var('srcdir') to be None for installed systems, because the source tree is not available there.
The advantage of making the value None is that this is easy to test for and would quickly break path manipulation code that tries to construct a path to a specific file in the source tree.
Making the value to be the name of the directory containing Makefile would still break code that tries to access files relative to the source tree, but could that breakage could be harder to track.
BTW. sysconfig really needs a better description of which variables are supposed to be available, it currently exports every definition in the Makefile and pyconfig.h, and not all of those definitions are usable outside of CPython's build process.
> I'd make get_config_var('srcdir') to be None for installed systems,
> because the source tree is not available there.
While playing with a version of the patch which returns None for non-source builds, I found that distutils.support._get_xxmodule_path() depends on get_config_var('srcdir') always returning a string:
def _get_xxmodule_path():
srcdir = sysconfig.get_config_var('srcdir')
candidates = [
os.path.join(os.path.dirname(__file__), 'xxmodule.c'),
os.path.join(srcdir, 'Modules', 'xxmodule.c'),
os.path.join(srcdir, '..', '..', '..', 'Modules', 'xxmodule.c'),
]
for path in candidates:
if os.path.exists(path):
return path
It is easy enough to modify _get_xxmodule_path() to check for None. But this does suggest that returning None might break some currently working 3rd party code.
Any objection if I commit the last patch before the next beta? This is the one which on installed Pythons have
get_config_var('srcdir') == os.path.dirname(get_makefile_filename())
on posix systems.
LGTM
Does get_config_var('srcdir') always return a string or sometimes None?
> Does get_config_var('srcdir') always return a string or sometimes None?
Always a string.
distutils.support._get_xxmodule_path() is one place which (currently) would throw an exception if it returned None.
New changeset d2f448dbc30d by Richard Oudkerk in branch 'default':
Issue #15364: Fix sysconfig.get_config_var('srcdir') to be an absolute path.
Okay, so LGTM. Let’s ask the RMs if this is a new behavior or a bugfix.
The current patch should be fine, although it is IMHO not the long-term solution. For installed python's get_config_var('srcdir') still lies, but now at least returns slightly more sane path.
As I noted before the real problem is that it is not clear which config_vars are usable in which situations. One example is 'srcdir': this value is only useful in the build tree and there currently is no clean way to signal that you are retrieving a value that is not useful. Another example is 'RUNSHARED', that's also only useable when building python.
I'm not sure what the right solution for the larger issue is. It might be good enough to document generally useful config_vars and warn that other's might exist but might not be safe to use, on the other hand it might be better to explicitly reduce the set of config_vars to something sane (and document which those are and when they can be used)
New changeset c2618b916081 by Ned Deily in branch 'default':
Issue #15364: Fix test_srcdir for the installed case.
> One example is 'srcdir': this value is only useful in the build tree and
> there currently is no clean way to signal that you are retrieving a
> value that is not useful.
In the particular case of 'srcdir', sysconfig.is_python_build() tells you whether the value is useful.
Concerns about sysconfig often returning values which are meaningless for the current configuration can be discussed in another issue.
Unless there are objections I will close. | https://bugs.python.org/issue15364 | CC-MAIN-2021-21 | refinedweb | 2,088 | 58.38 |
DBD::Mock - Mock database driver for testing
use DBI; # connect to your $mock_params = $sth->{mock_params}; print "Used statement: ", $sth->{mock_statement}, "\n", "Bound parameters: ", join( ', ', @{ $mock_params } ), "\n";
Testing with databases can be tricky. If you are developing a system married to a single database then you can make some assumptions about your environment and ask the user to provide relevant connection information. But if you need to test a framework that uses DBI, particularly a framework that uses different types of persistence schemes, then it may be more useful to simply verify what the framework is trying to do -- ensure the right SQL is generated and that the correct parameters are bound.
DBD::Mock makes it easy to just modify your configuration (presumably held outside your code) and just use it instead of
DBD::Foo (like DBD::Pg or DBD::mysql) in your framework.
There is no distinct area where using this module makes sense. (Some people may successfully argue that this is a solution looking for a problem...) Indeed, if you can assume your users have something like DBD::AnyData or DBD::SQLite or if you do not mind creating a dependency on them then it makes far more sense to use these legitimate driver implementations and test your application in the real world -- at least as much of the real world as you can create in your tests...
And if your database handle exists as a package variable or something else easily replaced at test-time then it may make more sense to use Test::MockObject to create a fully dynamic handle. There is an excellent article by chromatic about using Test::MockObject in this and other ways, strongly recommended. (See "SEE ALSO" for a link)
DBD::Mock comprises a set of classes used by DBI to implement a database driver. But instead of connecting to a datasource and manipulating data found there it tracks all the calls made to the database handle and any created statement handles. You can then inspect them to ensure what you wanted to happen actually happened. For instance, say you have a configuration file with your database connection information:
[DBI] dsn = DBI:Pg:dbname=myapp user = foo password = bar
And this file is read in at process startup and the handle stored for other procedures to use:
package ObjectDirectory; my ( $DBH ); sub run_at_startup { my ( $class, $config ) = @_; $config ||= read_configuration( ... ); my $dsn = $config->{DBI}{dsn}; my $user = $config->{DBI}{user}; my $pass = $config->{DBI}{password}; $DBH = DBI->connect( $dsn, $user, $pass ) || die ...; } sub get_database_handle { return $DBH; }
A procedure might use it like this (ignoring any error handling for the moment):
package My::UserActions; sub fetch_user { my ( $class, $login ) = @_; my $dbh = ObjectDirectory->get_database_handle; my $sql = q{ SELECT login_name, first_name, last_name, creation_date, num_logins FROM users WHERE login_name = ? }; my $sth = $dbh->prepare( $sql ); $sth->execute( $login ); my $row = $sth->fetchrow_arrayref; return ( $row ) ? User->new( $row ) : undef; }
So for the purposes of our tests we just want to ensure that:
Assume whether the SQL actually works or not is irrelevant for this test :-)
To do that our test might look like:
my $config = ObjectDirectory->read_configuration( ... ); $config->{DBI}{dsn} = 'DBI:Mock:'; ObjectDirectory->run_at_startup( $config ); my $login_name = 'foobar'; my $user = My::UserActions->fetch_user( $login_name ); # Get the handle from ObjectDirectory; # this is the same handle used in the # 'fetch_user()' procedure above my $dbh = ObjectDirectory->get_database_handle(); # Ask the database handle for the history # of all statements executed against it my $history = $dbh->{mock_all_history}; # Now query that history record to # see if our expectations match reality is(scalar(@{$history}), 1, 'Correct number of statements executed' ; my $login_st = $history->[0]; like($login_st->statement, qr/SELECT login_name.*FROM users WHERE login_name = ?/sm, 'Correct statement generated' ); my $params = $login_st->bound_params; is(scalar(@{$params}), 1, 'Correct number of parameters bound'); is($params->[0], $login_name, 'Correct value for parameter 1' ); # Reset the handle for future operations $dbh->{mock_clear_history} = 1;
The list of properties and what they return is listed below. But in an overall view:
execute(). It can also contain predefined results for the statement handle to 'fetch', track how many fetches were called and what its current record is.
This may be an incredibly naive implementation of a DBD. But it works for me ...
Since this is a normal DBI statement handle we need to expose our tracking information as properties (accessed like a hash) rather than methods.
This is a boolean property which when set to true (
1) will not allow DBI to connect. This can be used to simulate a DSN error or authentication failure. This can then be set back to false (
0) to resume normal DBI operations. Here is an example of how this works:
# install the DBD::Mock driver my $drh = DBI->install_driver('Mock'); $drh->{mock_connect_fail} = 1; # this connection will fail my $dbh = DBI->connect('dbi:Mock:', '', '') || die "Cannot connect"; # this connection will throw an exception my $dbh = DBI->connect('dbi:Mock:', '', '', { RaiseError => 1 }); $drh->{mock_connect_fail} = 0; # this will work now ... my $dbh = DBI->connect(...);
This feature is conceptually different from the 'mock_can_connect' attribute of the
$dbh in that it has a driver-wide scope, where 'mock_can_connect' is handle-wide scope. It also only prevents the initial connection, any
$dbh handles created prior to setting 'mock_connect_fail' to true (
1) will still go on working just fine.
This is an ARRAY reference which holds fake data sources which are returned by the Driver and Database Handle's
data_source() method.
This takes a string and adds it to the 'mock_data_sources' attribute.
Returns an array reference with all history (a.k.a.
DBD::Mock::StatementTrack) objects created against the database handle in the order they were created. Each history object can then report information about the SQL statement used to create it, the bound parameters, etc..
Returns a
DBD::Mock::StatementTrack::Iterator object which will iterate through the current set of
DBD::Mock::StatementTrack object in the history. See the DBD::Mock::StatementTrack::Iterator documentation below for more information.
If set to a true value all previous statement history operations will be erased. This includes the history of currently open handles, so if you do something like:
my $dbh = get_handle( ... ); my $sth = $dbh->prepare( ... ); $dbh->{mock_clear_history} = 1; $sth->execute( 'Foo' );
You will have no way to learn from the database handle that the statement parameter 'Foo' was bound.
This is useful mainly to ensure you can isolate the statement histories from each other. A typical sequence will look like:
set handle to framework perform operations analyze mock database handle reset mock database handle history perform more operations analyze mock database handle reset mock database handle history ...
This statement allows you to simulate a downed database connection. This is useful in testing how your application/tests will perform in the face of some kind of catastrophic event such as a network outage or database server failure. It is a simple boolean value which defaults to on, and can be set like this:
# turn the database off $dbh->{mock_can_connect} = 0; # turn it back on again $dbh->{mock_can_connect} = 1;
The statement handle checks this value as well, so something like this will fail in the expected way:
$dbh = DBI->connect( 'DBI:Mock:', '', '' ); $dbh->{mock_can_connect} = 0; # blows up! my $sth = eval { $dbh->prepare( 'SELECT foo FROM bar' ) }); if ( $@ ) { # Here, $DBI::errstr = 'No connection present' }
Turning off the database after a statement prepare will fail on the statement
execute(), which is hopefully what you would expect:
$dbh = DBI->connect( 'DBI:Mock:', '', '' ); # ok! my $sth = eval { $dbh->prepare( 'SELECT foo FROM bar' ) }); $dbh->{mock_can_connect} = 0; # blows up! $sth->execute;
Similarly:
$dbh = DBI->connect( 'DBI:Mock:', '', '' ); # ok! my $sth = eval { $dbh->prepare( 'SELECT foo FROM bar' ) }); # ok! $sth->execute; $dbh->{mock_can_connect} = 0; # blows up! my $row = $sth->fetchrow_arrayref;
Note: The handle attribute
Active and the handle method
ping will behave according to the value of
mock_can_connect. So if
mock_can_connect were to be set to 0 (or off), then both
Active and
ping would return false values (or 0).
This stocks the database handle with a record set, allowing you to seed data for your application to see if it works properly.. Each recordset is a simple arrayref of arrays with the first arrayref being the fieldnames used. Every time a statement handle is created it asks the database handle if it has any resultsets available and if so uses it.
Here is a sample usage, partially from the test suite:
my @user_results = ( [ 'login', 'first_name', 'last_name' ], [ 'cwinters', 'Chris', 'Winters' ], [ 'bflay', 'Bobby', 'Flay' ], [ 'alincoln', 'Abe', 'Lincoln' ], ); my @generic_results = ( [ 'foo', 'bar' ], [ 'this_one', 'that_one' ], [ 'this_two', 'that_two' ], ); my $dbh = DBI->connect( 'DBI:Mock:', '', '' ); $dbh->{mock_add_resultset} = \@user_results; # add first resultset $dbh->{mock_add_resultset} = \@generic_results; # add second resultset my ( $sth ); eval { $sth = $dbh->prepare( 'SELECT login, first_name, last_name FROM foo' ); $sth->execute(); }; # this will fetch rows from the first resultset... my $row1 = $sth->fetchrow_arrayref; my $user1 = User->new( login => $row->[0], first => $row->[1], last => $row->[2] ); is( $user1->full_name, 'Chris Winters' ); my $row2 = $sth->fetchrow_arrayref; my $user2 = User->new( login => $row->[0], first => $row->[1], last => $row->[2] ); is( $user2->full_name, 'Bobby Flay' ); ... my $sth_generic = $dbh->prepare( 'SELECT foo, bar FROM baz' ); $sth_generic->execute; # this will fetch rows from the second resultset... my $row = $sth->fetchrow_arrayref;
You can also associate a resultset with a particular SQL statement instead of adding them in the order they will be fetched:
$dbh->{mock_add_resultset} = { sql => 'SELECT foo, bar FROM baz', results => [ [ 'foo', 'bar' ], [ 'this_one', 'that_one' ], [ 'this_two', 'that_two' ], ], };
This will return the given results when the statement 'SELECT foo, bar FROM baz' is prepared. Note that they will be returned every time the statement is prepared, not just the first. It should also be noted that if you want, for some reason, to change the result set bound to a particular SQL statement, all you need to do is add the result set again with the same SQL statement and DBD::Mock will overwrite it.
It should also be noted that the
rows method will return the number of records stocked in the result set. So if your code/application makes use of the
$sth->rows method for things like UPDATE and DELETE calls you should stock the result set like so:
$dbh->{mock_add_resultset} = { sql => 'UPDATE foo SET baz = 1, bar = 2', # this will appear to have updated 3 rows results => [[ 'rows' ], [], [], []], }; # or ... $dbh->{mock_add_resultset} = { sql => 'DELETE FROM foo WHERE bar = 2', # this will appear to have deleted 1 row results => [[ 'rows' ], []], };
Now I admit this is not the most elegant way to go about this, but it works for me for now, and until I can come up with a better method, or someone sends me a patch ;) it will do for now.
If you want a given statement to fail, you will have to use the hashref method and add a 'failure' key. That key can be handed an arrayref with the error number and error string, in that order. It can also be handed a hashref with two keys - errornum and errorstring. If the 'failure' key has no useful value associated with it, the errornum will be '1' and the errorstring will be 'Unknown error'.
This attribute can be used to set up values for get_info(). It takes a hashref of attribute_name/value pairs. See DBI for more information on the information types and their meaning.
This attribute can be used to set a current DBD::Mock::Session object. For more information on this, see the DBD::Mock::Session docs below. This attribute can also be used to remove the current session from the
$dbh simply by setting it to
undef.
This attribute is incremented each time an INSERT statement is passed to
prepare on a per-handle basis. It's starting value can be set with the 'mock_start_insert_id' attribute (see below).
$dbh->{mock_start_insert_id} = 10; my $sth = $dbh->prepare('INSERT INTO Foo (foo, bar) VALUES(?, ?)'); $sth->execute(1, 2); # $dbh->{mock_last_insert_id} == 10 $sth->execute(3, 4); # $dbh->{mock_last_insert_id} == 11
For more examples, please refer to the test file t/025_mock_last_insert_id.t.
This attribute can be used to set a start value for the 'mock_last_insert_id' attribute. It can also be used to effectively reset the 'mock_last_insert_id' attribute as well.
This attribute also can be used with an ARRAY ref parameter, it's behavior is slightly different in that instead of incrementing the value for every
prepare it will only increment for each
execute. This allows it to be used over multiple
execute calls in a single
$sth. It's usage looks like this:
$dbh->{mock_start_insert_id} = [ 'Foo', 10 ]; $dbh->{mock_start_insert_id} = [ 'Baz', 20 ]; my $sth1 = $dbh->prepare('INSERT INTO Foo (foo, bar) VALUES(?, ?)'); my $sth2 = $dbh->prepare('INSERT INTO Baz (baz, buz) VALUES(?, ?)'); $sth1->execute(1, 2); # $dbh->{mock_last_insert_id} == 10 $sth2->execute(3, 4); # $dbh->{mock_last_insert_id} == 20
Note that DBD::Mock's matching of table names in 'INSERT' statements is fairly simple, so if your table names are quoted in the insert statement (
INSERT INTO "Foo") then you need to quote the name for
mock_start_insert_id:
$dbh->{mock_start_insert_id} = [ q{"Foo"}, 10 ];
DBI provides some simple parsing capabilities for 'SELECT' statements to ensure that placeholders are bound properly. And typically you may simply want to check after the fact that a statement is syntactically correct, or at least what you expect.
But other times you may want to parse the statement as it is prepared rather than after the fact. There is a hook in this mock database driver for you to provide your own parsing routine or object.
The syntax is simple:
$dbh->{mock_add_parser} = sub { my ( $sql ) = @_; unless ( $sql =~ /some regex/ ) { die "does not contain secret fieldname"; } };
You can also add more than one for a handle. They will be called in order, and the first one to fail will halt the parsing process:
$dbh->{mock_add_parser} = \&parse_update_sql; $dbh->{mock_add-parser} = \&parse_insert_sql;
Depending on the 'PrintError' and 'RaiseError' settings in the database handle any parsing errors encountered will issue a
warn or
die. No matter what the statement handle will be
undef.
Instead of providing a subroutine reference you can use an object. The only requirement is that it implements the method
parse() and takes a SQL statement as the only argument. So you should be able to do something like the following (untested):
my $parser = SQL::Parser->new( 'mysql', { RaiseError => 1 } ); $dbh->{mock_add_parser} = $parser;
These properties will dispatch to the Driver's properties of the same name.
This returns the value of
mock_last_insert_id.
In order to capture begin_work(), commit(), and rollback(), DBD::Mock will create statements for them, as if you had issued them in the appropriate SQL command line program. They will go through the standard prepare()-execute() cycle, meaning that any custom SQL parsers will be triggered and DBD::Mock::Session will need to know about these statements.
This will create a statement with SQL of "BEGIN WORK" and no parameters.
This will create a statement with SQL of "COMMIT" and no parameters.
This will create a statement with SQL of "ROLLBACK" and no parameters.
Returns true if the handle is a 'SELECT' and has more records to fetch, false otherwise. (From the DBI.)
The SQL statement this statement handle was
prepared with. So if the handle were created with:
my $sth = $dbh->prepare( 'SELECT * FROM foo' );
This would return:
SELECT * FROM foo
The original statement is unmodified so if you are checking against it in tests you may want to use a regex rather than a straight equality check. (However if you use a phrasebook to store your SQL externally you are a step ahead...)
Fields used by the statement. As said elsewhere we do no analysis or parsing to find these, you need to define them beforehand. That said, you do not actually need this very often.
Note that this returns the same thing as the normal statement property 'FIELD'.
Returns an arrayref of parameters bound to this statement in the order specified by the bind type. For instance, if you created and stocked a handle with:
my $sth = $dbh->prepare( 'SELECT * FROM foo WHERE id = ? AND is_active = ?' ); $sth->bind_param( 2, 'yes' ); $sth->bind_param( 1, 7783 );
This would return:
[ 7738, 'yes' ]
The same result will occur if you pass the parameters via
execute() instead:
my $sth = $dbh->prepare( 'SELECT * FROM foo WHERE id = ? AND is_active = ?' ); $sth->execute( 7783, 'yes' );
The same using named parameters
my $sth = $dbh->prepare( 'SELECT * FROM foo WHERE id = :id AND is_active = :active' ); $sth->bind_param( ':id' => 7783 ); $sth->bind_param( ':active' => 'yes' );
An arrayref of arrayrefs representing the records the mock statement was stocked with.
Number of records the mock statement was stocked with; if never stocked it is still 0. (Some weirdos might expect undef...)
This returns the same value as mock_num_records. And is what is returned by the
rows method of the statement handle.
Current record the statement is on; returns 0 in the instances when you have not yet called
execute() and if you have not yet called a
fetch method after the execute.
Whether
execute() has been called against the statement handle. Returns 'yes' if so, 'no' if not.
Whether
finish() has been called against the statement handle. Returns 'yes' if so, 'no' if not.
Returns 'yes' if all the records in the recordset have been returned. If no
fetch() was executed against the statement, or If no return data was set this will return 'no'.
Returns a
DBD::Mock::StatementTrack object which tracks the actions performed by this statement handle. Most of the actions are separately available from the properties listed above, so you should never need this.
This module can be used to emulate Apache::DBI style DBI connection pooling. Just as with Apache::DBI, you must enable DBD::Mock::Pool before loading DBI.
use DBD::Mock qw(Pool); # followed by ... use DBI;
While this may not seem to make a lot of sense in a single-process testing scenario, it can be useful when testing code which assumes a multi-process Apache::DBI pooled environment.
Under the hood this module does most of the work with a
DBD::Mock::StatementTrack object. This is most useful when you are reviewing multiple statements at a time, otherwise you might want to use the
mock_* statement handle attributes instead.
Takes the following parameters:
Gets/sets the SQL statement used.
Gets/sets the fields to use for this statement.
Gets/set the bound parameters to use for this statement.
Gets/sets the data to return when asked (that is, when someone calls 'fetch' on the statement handle).
Gets/sets the current record number.
Returns true if the statement is a SELECT and has more records to fetch, false otherwise. (This is from the DBI, see the 'Active' docs under 'ATTRIBUTES COMMON TO ALL HANDLES'.)
Sets the state of the tracker 'executed' flag.
If set to 'yes' tells the tracker that the statement is finished. This resets the current record number to '0' and clears out the array ref of returned records.
Returns true if the current record number is greater than the number of records set to return.
Returns the number of fields set in the 'fields' parameter.
Returns the number of records in the current result set.
Returns the number of parameters set in the 'bound_params' parameter.
Sets bound parameter
$param_num to
$value. Returns the arrayref of currently-set bound parameters. This corresponds to the 'bind_param' statement handle call.
Pushes
@params onto the list of already-set bound parameters.
Tells the tracker that the statement has been executed and resets the current record number to '0'.
If the statement has been depleted (all records returned) returns undef; otherwise it gets the current recordfor returning, increments the current record number and returns the current record.
Tries to give an decent depiction of the object state for use in debugging.
This object can be used to iterate through the current set of
DBD::Mock::StatementTrack objects in the history by fetching the 'mock_all_history_iterator' attribute from a database handle. This object is very simple and is meant to be a convience to make writing long test script easier. Aside from the constructor (
new) this object has only one method.
Calling
nextwill return the next
DBD::Mock::StatementTrackobject in the history. If there are no more
DBD::Mock::StatementTrackobjects available, then this method will return false.
reset
This will reset the internal pointer to the beginning of the statement history.
The DBD::Mock::Session object is an alternate means of specifying the SQL statements and result sets for DBD::Mock. The idea is that you can specify a complete 'session' of usage, which will be verified through DBD::Mock. Here is an example:
my $session = DBD::Mock::Session->new('my_session' => ( { statement => "SELECT foo FROM bar", # as a string results => [[ 'foo' ], [ 'baz' ]] }, { statement => qr/UPDATE bar SET foo \= \'bar\'/, # as a reg-exp results => [[]] }, { statement => sub { # as a CODE ref my ($SQL, $state) = @_; return $SQL eq "SELECT foo FROM bar"; }, results => [[ 'foo' ], [ 'bar' ]] }, { # with bound parameters statement => "SELECT foo FROM bar WHERE baz = ? AND borg = ?", # check exact bound param value, # then check it against regexp bound_params => [ 10, qr/\d+/ ], results => [[ 'foo' ], [ 'baz' ]] } ));
As you can see, a session is essentially made up a list of HASH references we call 'states'. Each state has a 'statement' and a set of 'results'. If DBD::Mock finds a session in the 'mock_session' attribute, then it will pass the current
$dbh and SQL statement to that DBD::Mock::Session. The SQL statement will be checked against the 'statement' field in the current state. If it passes, then the 'results' of the current state will get feed to DBD::Mock through the 'mock_add_resultset' attribute. We then advance to the next state in the session, and wait for the next call through DBD::Mock. If at any time the SQL statement does not match the current state's 'statement', or the session runs out of available states, an error will be raised (and propagated through the normal DBI error handling based on your values for RaiseError and PrintError).
Also, as can be seen in the the session element, bound parameters can also be supplied and tested. In this statement, the SQL is compared, then when the statement is executed, the bound parameters are also checked. The bound parameters much match in both number of parameters and the parameters themselves, or an error will be raised.
As can also be seen in the example above, 'statement' fields can come in many forms. The simplest is a string, which will be compared using
eq against the currently running statement. The next is a reg-exp reference, this too will get compared against the currently running statement. The last option is a CODE ref, this is sort of a catch-all to allow for a wide range of SQL comparison approaches (including using modules like SQL::Statement or SQL::Parser for detailed functional comparisons). The first argument to the CODE ref will be the currently active SQL statement to compare against, the second argument is a reference to the current state HASH (in case you need to alter the results, or store extra information). The CODE is evaluated in boolean context and throws and exception if it is false.
new ($session_name, @session_states)
A
$session_namecan be optionally be specified, along with at least one
@session_states. If you don't specify a
$session_name, then a default one will be created for you. The
@session_statesmust all be HASH references as well, if this conditions fail, an exception will be thrown.
verify_statement ($dbh, $SQL)
This will check the
$SQLagainst the current state's 'statement' value, and if it passes will add the current state's 'results' to the
$dbh. If for some reason the 'statement' value is bad, not of the prescribed type, an exception is thrown. See above for more details.
verify_bound_params ($dbh, $params)
If the 'bound_params' slot is available in the current state, this will check the
$paramsagainst the current state's 'bound_params' value. Both number of parameters and the parameters themselves must match, or an error will be raised.
reset
Calling this method will reset the state of the session object so that it can be reused.
All functionality listed here is highly experimental and should be used with great caution (if at all).
We have added experimental erro handling in mock_add_resultset the best example is the test file t/023_statement_failure.t, but it looks something like this:
$dbh->{mock_add_resultset} = { sql => 'SELECT foo FROM bar', results => DBD::Mock->NULL_RESULTSET, failure => [ 5, 'Ooops!' ], };
The
5 is the DBI error number, and
'Ooops!' is the error string passed to DBI. This basically allows you to force an error condition to occur when a given SQL statement is execute. We are currently working on allowing more control on the 'when' and 'where' the error happens, look for it in future releases.
Basically this feature allows you to alias attributes to other attributes. So for instance, you can alias a commonly expected attribute like 'mysql_insertid' to something DBD::Mock already has like 'mock_last_insert_id'. While you can also just set 'mysql_insertid' yourself, this functionality allows it to take advantage of things like the autoincrementing of the 'mock_last_insert_id' attribute.
Right now this feature is highly experimental, and has been added as a first attempt to automatically handle some of the DBD specific attributes which are commonly used/accessed in DBI programming. The functionality is off by default so as to not cause any issues with backwards compatability, but can easily be turned on and off like this:
# turn it on $DBD::Mock::AttributeAliasing++; # turn it off $DBD::Mock::AttributeAliasing = 0;
Once this is turned on, you will need to choose a database specific attribute aliasing table like so:
DBI->connect('dbi:Mock:MySQL', '', '');
The 'MySQL' in the DSN will be picked up and the MySQL specific attribute aliasing will be used.
Right now only MySQL is supported by this feature, and even that support is very minimal. Currently the MySQL
$dbh and
$sth attributes 'mysql_insertid' are aliased to the
$dbh attribute 'mock_last_insert_id'. It is possible to add more aliases though, using the
DBD::Mock:_set_mock_attribute_aliases function (see the source code for details).
When writing the test suite I encountered some odd behavior with some
$dbh attributes. I still need to get deeper into how DBD's work to understand what it is that is actually doing wrong.
Each DBD has its own quirks and issues, it would be nice to be able to handle those issues with DBD::Mock in some way. I have an number of ideas already, but little time to sit down and really flesh them out. If you have any suggestions or thoughts, feel free to email me with them.
I would like to have the DBD::Mock::StatementTrack object handle more of the mock_* attributes. This would encapsulate much of the mock_* behavior in one place, which would be a good thing.
I would also like to add the ability to bind a subroutine (or possibly an object) to the result set, so that the results can be somewhat more dynamic and allow for a more realistic interaction.
DBD::NullP, which provided a good starting point
Test::MockObject, which provided the approach
Test::MockObject article -
Perl Code Kata: Testing Databases -
We have created a DBD::Mock google group for discussion/questions about this module.
bind_param_inout
begin_work(),
commit()and
rollback()methods.
fetchall_hashref(),
fetchrow_hashref()and
selectcol_arrayref()methods and tests.
mock_last_insert_idspatch and test
mock_can_prepare,
mock_can_execute, and
mock_can_fetchfeatures.
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
Chris Winters <chris@cwinters.com>
Stevan Little <stevan@iinteractive.com>
Rob Kinyon <rob.kinyon@gmail.com>
Mariano Wahlmann <dichoso _at_ gmail.com <gt> | http://search.cpan.org/~dichi/DBD-Mock-1.45/lib/DBD/Mock.pm | CC-MAIN-2015-18 | refinedweb | 4,580 | 51.78 |
#include <vtkFeatureEdges.h>
Inheritance diagram for vtkFeatureEdges:
vtkFeatureEdges is a filter to extract special types of edges from input polygonal data. These edges are either 1) boundary (used by one polygon) or a line cell; 2) non-manifold (used by three or more polygons); 3) feature edges (edges used by two triangles and whose dihedral angle > FeatureAngle); or 4) manifold edges (edges used by exactly two polygons). These edges may be extracted in any combination. Edges may also be "colored" (i.e., scalar values assigned) based on edge type. The cell coloring is assigned to the cell data of the extracted edges.
cxx(
/Graphics/vtkFeatureEdges.cxx)
h(
/Graphics/vtkFeatureEdges.h)
Definition at line 66 of file vtkFeatureEdges.h. | https://www.vtk.org/doc/release/4.2/html/classvtkFeatureEdges.html | CC-MAIN-2017-51 | refinedweb | 118 | 57.47 |
Hi Jedi (why not?) Thanks for the tips... > say i = putStrLn $ show i > > This already exist and is called "print" (though its type is more > general than your signature). > > So it is. > > walk i = randomRIO (0,1) >>= \r -> return (i+r*2-1) > > The >>= ... return is pretty ugly, it would rather be written as : > > > walk i = fmap (\r -> i + r * 2 - 1) $ randomRIO (0,1) > > Well, for the time being I like to see exactly what's happening with the monads. That's why I don't use do. There'll come a day when I already know and I'll bear it in mind for then. > > rep n i w s > > Passing say and walk as parameter seems a bit overkill, I seriously > doubt that you'll ever need this exact structure again, and even then > passing a single action should be enough : > > > rep n act i > > | n <= 0 = return () > > | otherwise = act i >>= \x -> rep (n-1) act x > > But what do I pass for act? walk.say? say>>walk? > rep may also be written with standard monad operations : > > rep n act i = foldM (\x _ -> act x) i $ replicate (n-1) () > > Cunning. But it seems a bit round-the-houses to me. I mean, there's no fundamental reason for that list of nothings; it's just plugging a hole in haskell. My counter looks naive but at least it's to the point. I guess it's a matter of taste. > Lastly it may be that the structure of the program itself, > particularly the use of randomRIO is suboptimal and a bit ugly, for a > throwaway program I would probably just use randomRs : > > > main = do > > g <- newStdGen > > mapM_ print . tail . scanl (\i r -> i+r*2-1) 50 . take 10 $ randomRs > (0,1) g > > Are there some extra dots in there? Actually, I can't let the number of random numbers control the number of iterations because my algorithm asks for random numbers when it feels like it. You can't predict how many unless you can predict the random numbers. My main loop is like this: step (w,i,o) = env o >>= \i' -> think w i' >>= \o' -> learn w i i' o o' >>= \w' -> return (w', i', o') I tried to tidy that up by factoring out that "remember the last iteration" business. (It's a Hebbian learning rule.) I figured I could use a comonad containing the current and previous values of i and o, a function that takes both and returns the new value, and let cobind shuffle them along. It didn't work though because I wasn't allowed to say: instance Comonad (a,a) where ... Apparently instance Comonad ((,) a) where ... is legal, but I really want to say that both elements of the tuple are the same, otherwise everything else barfs. Is there some workaround for that? The compiler seemed to imply that you can only ever have one parameter to a type in an instance declaration, but that would see rather limiting and arbitrary. What's the deal here? Adrian. -------------- next part -------------- An HTML attachment was scrubbed... URL: <> | http://www.haskell.org/pipermail/beginners/2011-March/006621.html | CC-MAIN-2014-10 | refinedweb | 517 | 71.44 |
std::ranges::uninitialized_move, std::ranges::uninitialized_move_result
From cppreference.com
1) Moves N elements from the input range
[ifirst, ilast)to the output range
[ofirst, olast)(that is an uninitialized memory area), where N is min(ranges::distance(ifirst, ilast), ranges::distance(ofirst, olast)).
The effect is equivalent to:
for (; ifirst != ilast && ofirst != olast; ++ofirst, ++if
[ifirst, ilast)that were already moved, are left in a valid but unspecified state.
2) Same as (1), but uses
in_rangeas the first range and
out_rangeas the second range, as if using ranges::begin(in_range) as
ifirst, ranges::end(in_range) as
ilast, ranges::begin(out_range) as
ofirst, and ranges::end(out_range) as
olast. by using ranges::copy_n if the value type of the output range is TrivialType.
[edit] Possible implementation
[edit] Example
Run this code
#include <cstdlib> #include <iomanip> #include <iostream> #include <memory> #include <string> void print(auto rem, auto first, auto last) { for (std::cout << rem; first != last; ++first) std::cout << std::quoted(*first) << ' '; std::cout << '\n'; } int main() { std::string in[] { "Home", "World" };(std::begin(in), std::end(in), first, last); print("after move, in: ", std::begin(in), std::end(in)); print("after move, out: ", first, last); std::ranges::destroy(first, last); } catch (...) { std::cout << "Exception!\n"; } std::free(out); } }
Possible output:
initially, in: "Home" "World" after move, in: "" "" after move, out: "Home" "World" | https://en.cppreference.com/w/cpp/memory/ranges/uninitialized_move | CC-MAIN-2021-04 | refinedweb | 221 | 51.78 |
I too added something like this based on OP_SELF. I was planning on backing it out as part of going to 5.1 just to have less to track when following versions, but if it's being done often enough, it is probably worth consideration as to: 1. What are the exact semantics desired for __methcall and the : operator. This is the trickier part. See some discussion below. 2. What additional functions are needed? I added: callmethod( obj, msg, ... ) -- invokes obj:msg( ... ) pcallmethod -- invokes obj:msg( ... ) in a protected context bindmethod( obj, msg ) -- returns a function that will invoke obj:msg( ... ) 3. Does __methcall just return a function to invoke or does it actually take the parameters? The former is easier to integrate with the existing OP_SELF but might not be as nice semantically. 4. Could this be handled by adding a third parameter to __index to indicate whether this request came from a method call context? Some of the issues with __methcall include: 1.1 What precedence is given to __methcall v table entries? 1.2 Can __methcall be a table or does it have to be a function? 1.3 What does inheritance look like in this model? It's very simple in the __index model. The big benefits of __methcall seem to be: * Easier support for safe userdata method invocation since methods can't be pulled off of one object and used on another. I could see a case for supporting __methcall just for userdata. * Separate namespaces for methods and attributes. Mark on 11/4/04 8:05 AM, Daniel Silverstone at dsilvers@digital-scurf.org wrote: >. | http://lua-users.org/lists/lua-l/2004-11/msg00057.html | crawl-001 | refinedweb | 270 | 68.26 |
Closed Bug 1112499 Opened 8 years ago Closed 6 years ago
data written to pipe/socketpair get lost in b2g emulator
Categories
(Firefox OS Graveyard :: Emulator, defect)
Tracking
(firefox48 fixed)
People
(Reporter: bagder, Assigned: bagder)
References
Details
Attachments
(1 file, 1 obsolete file)
In bug 1008091 I've been working on code that starts a new thread on FxOS (and Linux) and when shutting it down, it indicates death to the child thread using a pipe - the parent thread writes to it and the child thread poll()s it. When running this code in the b2g emulator (in the try-runs), at seemingly random intervals (but still frequent enough to be a problem) data that is written to the pipe doesn't arrive in the other end and thus it doesn't wake up poll() in the waiting thread. The result is a thread that doesn't terminate when it is supposed to. I've also tried to replace the pipe with a socketpair, but with seemlingly the same end result. This problem gets visible best when running xpcshell tests in the emulator. It is very rare that all tests manage to run without at least one of them getting hung on this problem and the test gets killed due to timeout (after 300 seconds). In bug 1008091 I intend to proceed and implement a work-around that detects when it runs in the emulator and avoids this situation only then, but it is awkward and ugly. The work-around writes to a shared variable and it makes the poll() timeout every NN milliseconds to check that variable. To repeat this problem, remove the variable-trick in nsNotifyAddrListener_Linux.cpp and run the xpcshell tests in the emulator, or before that patch has landed an earlier version of the patch that doesn't use the variable trick can be used.
I'm wondering if this is related to the other emulator flakiness we've been seeing for ages.
I had a look into this and I think I have an idea of what's going on. Here's part of nsNotifyAddrListener::Init(): ... 348: rv = NS_NewNamedThread("Link Monitor", getter_AddRefs(mThread), this); NS_ENSURE_SUCCESS(rv, rv); #ifdef MOZ_NUWA_PROCESS nsCOMPtr<nsIRunnable> runner = new NuwaMarkLinkMonitorThreadRunner(); mThread->Dispatch(runner, NS_DISPATCH_NORMAL); #endif 356: if (-1 == pipe(mShutdownPipe)) { return NS_ERROR_FAILURE; } ... And here's part of nsNotifyAddrListener::Run(): ... struct pollfd fds[2]; 260: fds[0].fd = mShutdownPipe[0]; ... while (!shutdown) { 279: int rc = EINTR_RETRY(poll(fds, 2, pollTimeout)); ... Note that mShutdownPipe isn't actually set up (on line 356) until after the thread is created (on line 348). If the thread runs before that call to pipe, line 260 will store -1 in fds[0].fd. Then, the call to poll on line 279 will be waiting on some nonexistent fd -1. If pollTimeout is -1, that call will never return, leading to hangs.
I can only but agree and say that it seems obvious now that you point it out. And probably the timing was so that this only hit us on the b2g emulator.
Just moving the setting up the pipe should do it then. You agree? I'll take it on a try-run adventure too and see how it plays.
Attachment #8667862 - Flags: feedback?(dkeeler)
Comment on attachment 8667862 [details] [diff] [review] 0001-bug-1112499-set-up-shutdown-pipe-before-new-thread-s.patch Review of attachment 8667862 [details] [diff] [review]: ----------------------------------------------------------------- This should do it, yes. Do you think it's still necessary to have the shutdown indicator variable/B2G workaround?
Attachment #8667862 - Flags: feedback?(dkeeler) → feedback+
This second try-run was a test that didn't use the shutdown variable and then we're back to getting lots of mochitest timeouts on the B2G ICS emulator. It would indicate that it doesn't receive the shutdown signal appropriately. Clearly there's something still lurking in there.
Those all look like bug 1186440.
Daniel, can you move forward with landing this? Moving the call to pipe is at least more correct than what's going on now (without this fix, on my linux box xpcshell tests will periodically hang for 5 minutes until they're killed and then (successfully) re-run, which hurts productivity). If there's more to investigate, we can do that in a follow-up bug.
Flags: needinfo?(daniel)
Okidoki, thanks for bringing this back to my attention - it had fallen through some cracks and ended up in a dusty corner of mine. Here's a squashed and rebased version of the patch. A try-run is in progress as I write this: I'll PTO the next week so if you feel confident, feel free to move for commit. Otherwise I'll make sure it happens when I get back. I also realized I didn't get an r+ from anyone on this. Are you okay with it?
Attachment #8667862 - Attachment is obsolete: true
Flags: needinfo?(daniel)
Attachment #8724257 - Flags: review?(dkeeler)
Comment on attachment 8724257 [details] [diff] [review] v2-0001-bug-1112499-set-up-shutdown-pipe-before-new-threa.patch Review of attachment 8724257 [details] [diff] [review]: ----------------------------------------------------------------- LGTM, but I suppose a necko peer should sign off.
Attachment #8724257 - Flags: review?(dkeeler) → review?(mcmanus)
(Also, thanks for the quick response here.)
Assignee: nobody → daniel
Status: NEW → RESOLVED
Closed: 6 years ago
status-firefox48: --- → fixed
Resolution: --- → FIXED | https://bugzilla.mozilla.org/show_bug.cgi?id=1112499 | CC-MAIN-2022-27 | refinedweb | 885 | 63.7 |
#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;
int main()
{
//seed random number generator
srand(static_cast<unsigned int>(time(0)));
//max possible secret number
const int MAX_NUMBER = 100;
//random number between 1-100
int secretNumber = (rand() % MAX_NUMBER) + 1;
//welcomes player and creates two variables
int tries = 0; //number of times player has guessed
int guess; //player's current guess
cout << "\tWelcome to Guess My Number" << endl << endl;
cout << "Guess my secret number between 1 and ";
cout << MAX_NUMBER << "." << endl << endl;
//guessing loop
do{
cout << "Enter a guess: ";
cin >> guess;
++tries;
if (guess > secretNumber)
{
cout << "Too high!" << endl << endl;
}
if (guess < secretNumber)
cout << "Too low!" << endl << endl;
} while (guess != secretNumber);
cout << endl;
cout << "You win! You got it in " << tries << " tries!";
return 0;
} | http://question.onlinegdb.com/5211/is-this-a-good-beginner-game-made-by-me-cpp | CC-MAIN-2020-29 | refinedweb | 122 | 60.35 |
1.2. Getting started with exploratory data analysis
In this recipe, we will give an introduction to IPython and Jupyter for data analysis. Most of the subject has been covered in the the prequel of this book, Learning IPython for Interactive Computing and Data Visualization, Second Edition, but we will review the basics here.
We will download and analyze a dataset about attendance on Montreal's bicycle tracks. This example is largely inspired by a presentation from Julia Evans (available at). Specifically, we will introduce the following:
- Data manipulation with pandas
- Data visualization with matplotlib
- Interactive widgets
How to do it...
1. The very first step is to import the scientific packages we will be using in this recipe, namely NumPy, pandas, and matplotlib. We also instruct matplotlib to render the figures as inline images in the Notebook:
import numpy as np import pandas as pd import matplotlib.pyplot as plt %matplotlib inline
We can enable high-resolution matplotlib figures on Retina display systems with the following commands:
python from IPython.display import set_matplotlib_formats set_matplotlib_formats('retina')
2. Now, we create a new Python variable called
url that contains the address to a CSV (Comma-separated values) data file. This standard text-based file format is used to store tabular data:
url = ("" "ipython-books/cookbook-2nd-data/" "master/bikes.csv")
3. pandas defines a
read_csv() function that can read any CSV file. Here, we pass the URL to the file. pandas will automatically download the file, parse it, and return a
DataFrame object. We need to specify a few options to make sure that the dates are parsed correctly:
df = pd.read_csv(url, index_col='Date', parse_dates=True, dayfirst=True)
4. The
df variable contains a DataFrame object, a specific pandas data structure that contains 2D tabular data. The
head(n) method displays the first
n rows of this table. In the Notebook, pandas displays a
DataFrame object in an HTML table, as shown in the following screenshot:
df.head(2)
Here, every row contains the number of bicycles on every track of the city, for every day of the year.
5. We can get some summary statistics of the table with the
describe() method:
df.describe()
6. Let's display some figures. We will plot the daily attendance of two tracks. First, we select the two columns,
Berri1 and
PierDup. Then, we call the
plot() method:
df[['Berri1', 'PierDup']].plot(figsize=(10, 6), style=['-', '--'], lw=2)
7. Now, we move to a slightly more advanced analysis. We will look at the attendance of all tracks as a function of the weekday. We can get the weekday easily with pandas: the
index attribute of the
DataFrame object contains the dates of all rows in the table. This index has a few date-related attributes, including
weekday_name:
df.index.weekday_name
Index(['Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday', 'Monday', 'Tuesday', ... 'Friday', 'Saturday', 'Sunday', 'Monday', 'Tuesday', 'Wednesday'], dtype='object', name='Date', length=261)
8. To get the attendance as a function of the weekday, we need to group the table elements by the weekday. The
groupby() method lets us do just that. We use
weekday instead of
weekday_name to keep the weekday order (Monday is 0, Tuesday is 1, and so on). Once grouped, we can sum all rows in every group:
df_week = df.groupby(df.index.weekday).sum()
df_week
9. We can now display this information in a figure. We create a matplotlib figure, and we use the
plot() method of a
DataFrame to create our plot:
fig, ax = plt.subplots(1, 1, figsize=(10, 8)) df_week.plot(style='-o', lw=3, ax=ax) ax.set_xlabel('Weekday') # We replace the labels 0, 1, 2... by the weekday # names. ax.set_xticklabels( ('Monday,Tuesday,Wednesday,Thursday,' 'Friday,Saturday,Sunday').split(',')) ax.set_ylim(0) # Set the bottom axis to 0.
10. Finally, let's illustrate the interactive capabilities of the Notebook. We will plot a smoothed version of the track attendance as a function of time (rolling mean). The idea is to compute the mean value in the neighborhood of any day. The larger the neighborhood, the smoother the curve. We will create an interactive slider in the Notebook to vary this parameter in real time in the plot. All we have to do is add the
@interact decorator above our plotting function:
from ipywidgets import interact @interact def plot(n=(1, 30)): fig, ax = plt.subplots(1, 1, figsize=(10, 8)) df['Berri1'].rolling(window=n).mean().plot(ax=ax) ax.set_ylim(0, 7000) plt.show()
How it works...
To create matplotlib figures, it is good practice to create a Figure (
fig) and one or several Axes (subplots,
ax object) with the
plt.subplots() command. The
figsize keyword argument lets us specify the size of the figure, in inches. Then, we call plotting methods directly on the Axes instances. Here, for example, we set the y limits of the axis with the
set_ylim() method. If there are existing plotting commands, like the
plot() method provided by pandas on DataFrame instances, we can pass the relevant Axis instance with the
ax keyword argument.
There's more...
pandas is the main data wrangling library in Python. Other tools and methods are generally required for more advanced analyses (signal processing, statistics, and mathematical modeling). We will cover these steps in the second part of this book, starting with Chapter 7, Statistical Data Analysis.
Here are some more references about data manipulation with pandas:
- Learning IPython for Interactive Computing and Data Visualization Second Edition, Packt Publishing, the prequel of this book
- Python for Data Analysis, O'Reilly Media, by Wes McKinney, the creator of pandas, at
- Python Data Science Handbook, O'Reilly Media, by Jake VanderPlas, at
- The documentation of pandas available at
- Usage guide of matplotlib, at
See also
- Introducing the multidimensional array in NumPy for fast array computations | https://ipython-books.github.io/12-getting-started-with-exploratory-data-analysis-in-the-jupyter-notebook/ | CC-MAIN-2019-09 | refinedweb | 970 | 57.16 |
Results 1 to 3 of 3
1080p HD iMovie project import problems...
- Member Since
- Jan 29, 2010
- Location
- Palm Beach Gardens, FL
- 89
- Specs:
- 17" Macbook Pro with 2.8GHz Core 2 Duo, 4GB 1066MHz DDR3, 500GB Serial ATA @ 7200 rpm, HiRes AntiGla
So I filmed a bunch of stuff from the zoo today and was all excited about creating an HD movie in iMovie. I remember last time I imported hd video that when I finished and uploaded it to youtube, it wasn't in HD.
I've done a bit of research before bed and i think I found out that with iMovie 9 I can only import videos that are 720. Could anyone explain to me how to import my 1080p videos into iMovie and export them in 1080p?
Another question I had was that I saw something about stabilization when importing. Would that make my videos not as shakey? And since i'v already copied my videos onto my macbook, do I have to plug the HD webbie back in to import them in hd?
Thanks for any help guys!!!I love
to jump out of perfectly good airplanes!
i will help
if you want to import it set the file's on your desktop.
then go into the menu and look for import.
Don't choose import from camera but import!
then choose the file's and there it is!this is what you need to do...
step 1:pee on your windows PC
step 2:kick your windows PC
step 3:enyoy your Mac
- Member Since
- Jan 22, 2010
- Location
- Victoria, BC
- 20,911
- Specs:
- Mid-2012 MBP (16GB, 1TB HD), Monoprice 24-inch second monitor, iPhone 5s 32GB, iPad Air 2 64GB
Could anyone explain to me how to import my 1080p videos into iMovie and export them in 1080p?
For exporting, the "Share" menu is your friend.
Another question I had was that I saw something about stabilization when importing. Would that make my videos not as shakey?
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MessageComposer::ContentJobBase
#include <contentjobbase.h>
Detailed Description
The ContentJobBase class.
Definition at line 24 of file contentjobbase.h.
Member Function Documentation
Use appendSubjob() instead.
Reimplemented from KCompositeJob.
Definition at line 89 of file contentjobbase.cpp.
This is meant to be used instead of KCompositeJob::addSubjob(), making it possible to add subjobs from the outside.
Transfers ownership of the
job to this object.
Definition at line 69 of file contentjobbase.cpp.
Get the resulting KMime::Content that the ContentJobBase has generated.
Jobs never delete their content.
Definition at line 61 of file contentjobbase.cpp.
Reimplement to do additional stuff before processing children, such as adding more subjobs.
Remember to call the base implementation.
Definition at line 97 of file contentjobbase.cpp.
Get extra content that was previously added.
Definition at line 82 of file contentjobbase.cpp.
This is called after all the children have been processed.
(You must use their resulting contents, or delete them.) Reimplement in subclasses to process concrete content. Call emitResult() when finished.
Implemented in MessageComposer::TransparentJob.
Set some extra content to be saved with the job, and available later, for example, in slot handling result of job.
Job does not take care of deleting extra content.
Definition at line 75 of file contentjobbase.cpp.
Starts processing this ContentJobBase asynchronously.
This processes all children in order first, then calls process(). Emits finished() after all processing is done, and the content is reachable through content().
Definition at line 56 of file contentjobbase.cpp.
The documentation for this class was generated from the following files:
Documentation copyright © 1996-2020 The KDE developers.
Generated on Sun Aug 2 2020 23:12:03 by doxygen 1.8.11 written by Dimitri van Heesch, © 1997-2006
KDE's Doxygen guidelines are available online. | https://api.kde.org/kdepim/messagelib/html/classMessageComposer_1_1ContentJobBase.html | CC-MAIN-2020-34 | refinedweb | 290 | 54.49 |
An interesting comment was raised by @Vyadh - Are static blocks interpreted or does the JIT play a part?
When are methods optimised?A method will be optimised when it is called often enough. This is controlled by the -XX:CompileThreshold=10000 flag. The compilation occurs in the background by default and a short time later, the optimised version of the code will be used. (Which is why it doesn't always happen at exact the 10K mark)
However, loops can also be optimised if they are called often enough. This typically takes about 2-5 seconds. This is why any bound loop which does nothing takes about 2-5 seconds. (Which is how long it takes the JIT to realise the loop doesn't do anything)
How does this apply to static blocks?static block are never called more than once. Even if they are loaded by different class loaders, they are optimised independently. (In the unlikely event you loaded the same class 10,000 times, it still wouldn't be optimised)
However, it is quite possible to have a loop iterate many times in a static block (though rare) This can result in the static block begin optimised by the JIT.
public class Main { static { long start = System.nanoTime(); for (int i = 0; i < 5000; i++) ; long time = System.nanoTime() - start; System.out.printf("Took %.3f ms to iterate 5 thousand times%n", time / 1e6); long start1 = System.nanoTime(); for (int i = 0; i < 5000; i++) ; long time1 = System.nanoTime() - start1; System.out.printf("Took %.3f ms to iterate 5 thousand times%n", time1 / 1e6); long start2 = System.nanoTime(); for (int j = 0; j < 1000 * 1000; j++) for (int i = 0; i < 1000 * 1000; i++) ; long time2 = System.nanoTime() - start2; System.out.printf("Took %.3f ms to iterate 1 trillion times%n", time2 / 1e6); long start3 = System.nanoTime(); for (int j = 0; j < 1000 * 1000; j++) for (int i = 0; i < 1000 * 1000; i++) ; long time3 = System.nanoTime() - start3; System.out.printf("Took %.3f ms to iterate 1 trillion times%n", time3 / 1e6); } public static void main(String[] args) { } }run the with -XX:+PrintCompilation flag outputs.
64 1 java.lang.String::charAt (33 bytes) 75 2 java.lang.String::hashCode (64 bytes) Took 0.067 ms to iterate 5 thousand times Took 0.062 ms to iterate 5 thousand times 88 1% Main:: @ 124 (249 bytes) Took 4.860 ms to iterate 1 trillion times Took 0.001 ms to iterate 1 trillion times
You can see that a loop of 5,000 is not enough to trigger optimisation, but a much larger loop does trigger optimisation. Without the JIT, there is no way the loop of one trillion time would finish in 3 seconds.
Once the method has been optimise the last one trillion loop takes practically no time at all.
Note@Vyadh notes that the client JVM doesn't appear to perform this optimisation and will wait a very long time.
From
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29 August 2012 07:59 [Source: ICIS news]
By Chow Bee Lin
?xml:namespace>
SINGAPORE
On the flip side, prices are unlikely to fall markedly because the downward pressure could be off-set by high crude values, they added.
US crude futures have been on a gradual uptrend since the start of July, with prices increasing from about $83/bbl on 2 July to $95.47 at the close of trade on 27 August.
The new PE and PP capacities will account for 11.3% and 7.1% of
Downstream demand might improve in October because plastics processors could raise production rates in the run-up to the year-end peak consumption season, market sources said.
However, in view of the slower economic growth projected for
Restocking activity is also expected to be limited in the fourth quarter as most plastics processors and stockists have been keeping low stocks this year because of the uncertain global economic outlook, China-based traders said.
China’s interest rate cuts since late last year aimed at boosting domestic consumption have failed to lift plastics resin demand significantly because the Chinese plastics processing sector still derives much of its revenue from European and US markets.
But demand in both the regions has been dwindling.
According to a survey by the Pew Research Center (PRC) issued this month the
The recent hikes in China’s PP and PE import prices does not reflect strengthening market fundamentals because it is mainly driven by high energy and feedstock prices instead of strong demand, said a source at a Taiwanese resin producer.
China’s benchmark LLDPE and PP flat yarn import prices had risen by 2-4% over the four weeks ended 24 August to $1,280-1,320/tonne CFR (cost and freight) China, and $1,370-1,400/tonne CFR China, according to ICIS.
Additional reporting by Amy Yu, Angie Li, Rain Dong, Lizzie Yu, Doreen Zhao
( | http://www.icis.com/Articles/2012/08/29/9590625/chinas-pe-pp-import-prices-may-move-sideways-in-q4.html | CC-MAIN-2014-52 | refinedweb | 321 | 56.59 |
Troubleshooting CPU problems in production for the cloud
How can we solve CPU issues when the application is already in production for the cloud? It’s not like we can fire up Task Manager and see what process is hogging all the CPU. Or can we? In this article, Ram Lakshmanan goes over the three simple steps any developer can follow when trying to diagnose and troubleshoot CPU issues.
Diagnosing and troubleshooting CPU problems in production for a cloud environment can be both tricky and tedious. Your application might have millions of lines of code, so trying to identify exact line of code that is causing the CPU to spike up is basically the equivalent of finding a needle in a haystack. In this article, we’ll learn how to find that needle in matter of seconds.
To help readers better understand this troubleshooting technique, we built a sample application and deployed it in an Amazon Elastic Compute Cloud (aka Amazon EC2) instance. Once this application was launched, it caused the CPU consumption to spike up 199.1%. Now, let’s walk through the steps that we followed to troubleshoot this problem. Basically, there are three simple steps:
- Identify the threads that consume CPU
- Capture thread dumps
- Identify the lines of code that are causing the CPU to spike up
Let’s dive right in!
1. Identify the threads that consume CPU
In the EC2 instance, multiple processes could be running. The first step is to identify the process that is causing the CPU to spike up. The best way to do is to use the
TOP command that is present in
*nix flavor of operating systems.
Issue command
top from the console:
$ top
This command will display all the processes that are running in the Amazon EC2 instance, sorted by high CPU consuming processes displayed at the top. When we issue the command in the Amazon EC2 instance, we get the following output:
Fig: ‘top’ command issued from an AWS EC2 instance
From the output, you should notice that process#31294 is consuming 199.1% of the CPU. That’s a pretty high consumption. So, now we have identified the process in the Amazon EC2 instance that is causing the CPU to spike up. The next step is to identify the threads in this process that are causing the CPU to spike up.
Issue command
top -H -p {pid} from the console. For example:
$ top -H -p 31294
This command will display all the threads are causing the CPU to spike up in this particular #31294 process. When we issued this command in the Amazon EC2 instance, we see the following output:
Fig:
top -H -p {pid} command issued from an AWS EC2 instance
From this output, you should notice that:
- Thread ID #31306 consumes 69.3% of CPU
- Thread ID #31307 consumes 65.6% of CPU
- Thread ID #31308 consumes 64.0% of CPU
The remaining threads all consume a negligible amount of CPU.
This is good step forward, as we have identified the threads that are causing CPU to spike. In the next step we, need to capture thread dumps to identify the lines of code that are causing the CPU to spike up.
SEE ALSO: StackOverFlowError: Causes & solutions
2. Capture thread dumps
A thread dump is a snapshot of all threads that are present in the application. A thread dump reports things like the thread state, stacktrace (i.e. code path that thread is executing), and the thread ID-related information of every thread in the application.
There are eight different options to capture thread dumps. You can choose whichever option that is convenient for you. One of the simplest options for capturing a thread dump is to use tool
jstack which is packaged in JDK. This tool can be found in
$JAVA_HOME/bin folder. Here’s the command to capture thread dump:
jstack -l {pid} > {file-path}
Where
pid is the process ID of the application, whose thread dump should be captured and
file-path is the file path where thread dump will be written in to.
For example, in the example below, the dump of the process would be generated in
/opt/tmp/threadDump.txt file.
jstack -l 31294 > /opt/tmp/threadDump.txt
SEE ALSO: Turbo charge CPU utilization in Fork/Join using the ManagedBlocker
3. Identify lines of code that are causing the CPU to spike up
The next step is to analyze the thread dump to identify the lines of code that are causing the CPU to spike up. We would recommend analyzing thread dumps through fastThread, a free online thread dump analysis tool.
Now, we upload the captured thread dump to the fastThread tool. This tool generates a beautiful visual report with multiple sections. There is a search box on the top right corner of the report. We can enter the IDs of the threads that have been consuming a high amount of CPU, i.e., the thread IDs that we identified in step #1. In this case, that would be #31306, #31307, and #31308.
Here’s how the fastThread tool displayed the three threads stack trace:
Fig: FastThread tool displaying CPU consuming thread.
You can notice the three threads to be in RUNNABLE state and executing this line of code:
com.buggyapp.cpuspike.Object1.execute(Object1.java:13)
The following is the application source code:
package com.buggyapp.cpuspike; /** * * @author Test User */ public class Object1 { public static void execute() { while (true) { doSomething(); } } public static void doSomething() { } }
You can see line #13 in
object1.java is
doSomething();. You can see that
doSomething() method does nothing. However, it is invoked an infinite number of times because of a non-terminating loop in line #11. If a thread starts to loop an infinite number of times, then the CPU will start to spike up. That is what exactly happening in this sample program. If the non-terminating loop in line #11 is fixed, then then this CPU spike will go away.
SEE ALSO: Meet Osaka, a Rust async for explicit, well-defined code that doesn’t take up too much space
Conclusion
So, if you are troubleshooting a CPU problem while in production, there are a few simple things to do. First, utilize the
TOP tool to identify the thread IDs that are causing the CPU spike up. Then, capture the thread dumps. Finally, analyze the thread dumps to identify the exact lines of code that are causing the CPU to spike up. Enjoy troubleshooting, happy hacking!
It a Nice article Ram . Keep going and share more about those type issues . | https://jaxenter.com/troubleshooting-cpu-cloud-155415.html | CC-MAIN-2020-34 | refinedweb | 1,098 | 71.85 |
C# Sharp Exercises: Determine whether the string "birds" is a substring of a familiar
C# Sharp String: Exercise-38 with Solution
Write a C# Sharp program to determine whether the string "birds" is a substring of a familiar.
Note : Quotation ‘two birds with one stone'.
Sample Solution:-
C# Sharp Code:
using System; class Example38 { public static void Main() { string str1 = "Kill two birds with one stone"; string str2 = "birds"; bool x = str1.Contains(str2); Console.WriteLine("'{0}' is in the string '{1}': {2}", str2, str1, x); if (x) { int index = str1.IndexOf(str2); if (index >= 0) Console.WriteLine("'{0} begins at character position {1}", str2, index + 1); } } }
Sample Output:
'birds' is in the string 'Kill two birds with one stone': True 'birds begins at character position 10
Flowchart :
C# Sharp Code Editor:
Improve this sample solution and post your code through Disqus
Previous: Write a C# Sharp program to concatenate the array values of strings.
Next: Write a C# Sharp program to creates two string objects with different values. When it calls the Copy method to assign the first value to the second string, the output indicates that the strings represent different object references although their values are now equal. On the other hand, when the first string is assigned to the second string, the two strings have identical values because they represent the same object reference.
What is the difficulty level of this exercise?
New Content: Composer: Dependency manager for PHP, R Programming | https://www.w3resource.com/csharp-exercises/string/csharp-string-exercise-38.php | CC-MAIN-2019-18 | refinedweb | 244 | 58.21 |
Quantum Inspire and Qiskit
Last year here at QuTech we released Quantum Inspire, an on-line platform to show-case our work and enable the world to interact with quantum computing. QuTech is the advanced research center for Quantum Computing and Quantum Internet, a collaboration founded in 2014 by Delft University of Technology (TU Delft) and the Netherlands Organisation for Applied Scientific Research (TNO).
The cloud-based Quantum Inspire platform offers a graphical user interface as well as an API for more advanced use. Recently we have also released integration for IBM’s Qiskit. Quantum Inspire working in tandem with Qiskit enables users to get all the functionality and tools provided by Quantum Inspire, while also leveraging Qiskit which provides access to additional simulators, real quantum hardware and any other plugins compatible for Qiskit. All in a single development environment.
In the following paragraphs I will briefly introduce Quantum Inspire and the Qiskit integration for Quantum Inspire.
The web interface
First, let’s have a quick look at the web interface.
The main interactive element in the web interface is the editor. It provides a text-window where you can enter quantum instructions using QuTech’s cQASM 1.0 syntax. The experiments can be queued for execution from the web interface, and results can be inspected once they are done.
You do not need to have an account to run your first experiments. However, to use more advanced features (such as retaining previous experiments and results and creating multiple projects side-by-side) registration is required. It’s as simple as entering an email address and choosing a password. After confirming your email address, your account is active and ready to use.
API and SDK, programmatic access
We also wanted to offer a more programmatic way of interacting with the platform and its backends. Of course, it is possible to talk directly to the API, but that does require the user to get into the mechanics of doing http requests and parsing responses. All that distracts from the true purpose of the system: to explore quantum computing.
Qiskit provides a rich set of primitives to interact with quantum computers and quantum simulators and abstracts the mechanics of requests and responses into a more high-level domain-specific language. Instead of re-inventing the wheel and adding yet another quantum computing framework to the world, we decided to add support to Qiskit for the Quantum Inspire backends.
Example
Let’s dive right in, and show an example of how to use the Quantum Inspire backends with Qiskit. I will assume a basic understanding of Python development in general.
If you are already familiar with Qiskit, the code below will be very recognizable. Our Qiskit integration follows the BackendProvider mechanism introduced in Qiskit 0.7.0, by offering the QuantumInspireBackendProvider. Once a backend instance has been provided, it is used the same as one would use the existing AER or IBMQ backends.
I prefer to run things in a Python virtual environment to keep dependencies from different projects separated, so let’s set that up first. You can skip this step if you don’t want to use a virtual environment, although I heartily recommend you to start using them if you don’t already). Assuming you are on a unix-based system (for example, Linux or the Windows Subsystem for Linux):
python3 -m venv env
. ./env/bin/activate
On a MS Windows based environment, one would use something like:
python3 -m venv env
env\Scripts\activate
Next, we need to install Qiskit and the Quantum Inspire SDK, which can most conveniently be done using Python’s package manager, pip:
pip install qiskit
pip install quantuminspire
This will install the latest public release versions of Qiskit and the Quantum Inspire SDK. If you are interested in the latest development version instead, you can also check out the Quantum Inspire SDK on github.
Now open your favourite editor or IDE, and create a new Python file named example_qiskit_entangle.py.
First, we start with some boilerplate and the necessary imports:
"""Example usage of the Quantum Inspire backend with the QisKit SDK.A simple example that demonstrates how to use the SDK to create a circuit to create a Bell state, and simulate the circuit on Quantum Inspire.For documentation on how to use QisKit we refer to []().Specific to Quantum Inspire is the creation of the QI instance, which is used to set the authentication of the user and provides a Quantum Inspire backend that is used to execute the circuit.Copyright 2018-19 QuTech Delft. Licensed under the Apache License, Version 2.0.
"""from getpass import getpassfrom qiskit.circuit import QuantumRegister, ClassicalRegister, QuantumCircuit
from qiskit.tools.compiler import execute
from quantuminspire.qiskit import QI
After some introductory documentation, we import the relevant modules from Qiskit (the QuantumRegister, ClassicalRegister and QuantumCircuit classes and the execute method). The special bit here is the last line, where we import the Quantum Inspire BackendProvider as QI.
In order to ask for credentials, we add a convenience method that will ask the user for their email and password and return these as a tuple:
def get_authentication():
"""Gets the authentication for connecting to the
Quantum Inspire API.
"""
print(‘Enter email:’)
print(‘Enter password’)
password = getpass()
return email, password
We intend to improve on this in the near future by using API tokens that can be stored on disk to avoid having to type in the email address and password each time we run an experiment.
Now follows the main bulk of the example:
if __name__ == '__main__':
if 'authentication' not in vars().keys():
authentication = get_authentication()
QI.set_authentication_details(*authentication)
qi_backend = QI.get_backend('QX single-node simulator')
First of all, we populate the authentication tuple with email and password values. These are passed to the QI object (which is a BackendProvider) by means of the set_authentication_details method. This authenticates the backend provider with the Quantum Inspire platform.
We then obtain a Backend instance from the provider QI by asking for the backend with the name “QX single-node simulator”. If we want, we can request a list of backends from QI by calling QI.backends(). At the time of writing this, for standard users, there will be only one backend shown: the QX single-node simulator. This backend executes experiments on a cloud-hosted instance of QX simulator.
Next, we set up the quantum circuit:
q = QuantumRegister(2)
b = ClassicalRegister(2)
circuit = QuantumCircuit(q, b) circuit.h(q[0])
circuit.cx(q[0], q[1])
circuit.measure(q, b)
First we define a register q of 2 qubits. Next, we also define a classical register that is 2 bits wide named b to contain our measurement results. With these we create the QuantumCircuit named circuit.
The operations are then added to the circuit. We create a basic Bell-state by applying a Hadamard gate to qubit 0, followed by a Controlled-NOT where qubit 0 is the control qubit and qubit 1 is the controlled qubit. Finally, we measure both qubits and store the measurement result in the classical register.
Execution is as easy as specifying the qi_backend provided earlier to the execute function:
qi_job = execute(circuit, backend=qi_backend, shots=256)
This will create a BaseJob instance. We can check progress of this job through the system by calling the qi_job.status() method. But for this simple example, let’s just request the result directly:
qi_result = qi_job.result()
This will wait for the job to complete, and returns a Result object, which we can then inspect:
histogram = qi_result.get_counts(circuit)
print(‘\nState\tCounts’)
[print(‘{0}\t{1}’.format(state, counts)) for state, counts in histogram.items()]
The full source code is included in the SDK available from the github repo.
Let’s run the example and see what the result is:
(env) ~$ python example_qiskit_entangle.py
Enter email: demo@quantum-inspire.com
State Counts
00 124
11 132
(env) ~$
As expected for this Bell-state, we measure an (approximately) equal number of instances of both outcomes 00 and 11.
Of course, if you prefer you can use the backend from a jupyter notebook. Two examples have been included in the SDK:
- Grover’s algorithm example, adapted for Quantum Inspire
- Performance test based on a paper by Ryan LaRose
Future plans
What does the future hold?
While the ability to simulate qubits already allows us to explore the world of quantum computing, it does not offer us anything we can not do on classical computers (since the simulations by definition run on classical computers). It is the intention to add access to real quantum computers being developed at QuTech to Quantum Inspire. With the help of our unified API and Qiskit’s unified backend provider mechanism, it will be a seamless switch between simulation (on our or Qiskit’s simulators) and execution on real hardware.
The cQASM 1.0 language and QX Simulator support classical feedback. Based on the result of measuring a qubit, a subsequent single-qubit gate may execute or not. This feature is not yet exposed through the Qiskit integration, but it is high on our list to implement.
While cQASM 1.0 already contains constructs for classical feedback, it is expected that cQASM 2.0 will expand on this concept of classical-quantum interaction with a much richer expressive ability. Once the specification of this next version of cQASM solidifies we intend to integrate this into the platform. What this means for the Qiskit integration is not entirely thought-out yet, but the aim is to expose this new functionality through Qiskit as well.
Final words
We are quite excited to be able to offer access to Quantum Inspire through the popular, well-established and maturing platform that Qiskit has become over the past years. We invite everyone to try their algorithms on Quantum Inspire, and welcome all feedback, both on the Qiskit and SDK integration as well as on the platform in general.
If you have any issues with or feature requests for the SDK, please use the issue tracker on github. For comments on the web interface or general comments, feel free to send us an email at webmaster@quantum-inspire.com. | https://medium.com/qiskit/quantum-inspire-and-qiskit-f1be608f8955 | CC-MAIN-2022-33 | refinedweb | 1,694 | 53.71 |
I’ve been doing R/Java development for some time, creating packages both large and small with this tool chain. I have used Eclipse as my package development environment almost exclusively, but I didn’t realize how much I relied on the IDE before I had to do some serious R/C++ package development. My first Rcpp package (wordcloud) only used a little bit of complied code, so just using a standard text editor was enough to get the job done, however when I went on to a more complex project, TextWrangler just wasn’t cutting it anymore. Where was my code completion? Where were my automatically detected syntax errors?
I found myself spending more time looking up class APIs, fixing stupid errors, and waiting for R CMD INSTALL to finish than I did coding. Unfortunately the internet did not come to the rescue. I searched and searched but couldn’t find anyone who used a modern IDE for package development with compiled code. In particular I wanted the following features.
- Code completion. What methods does that class have again? What arguments does that function take? Perhaps everyone is just smarter than me, but I can’t seem to keep the whole R/Rcpp API in my head. I just want to hit ctrl+space and see what my options are:
- Syntax error detection. Oh, I meant hasAttribute. Whoops, forgot that semicolon again.
- Incremental builds. It takes a long time for R CMD INSTALL to complete. The package that I am currently working on takes 2 minutes and 30 seconds to install. I don’t want to have to wait for a full install every time I make a small change to a function I am playing with.
- R and C++ syntax highlighting. Editing good looking code makes for a better coding experience.
The solution I found is a combination of Eclipse, Rcpp and RInside. Rcpp is undeniably the best way to embed high performance C++ code within R. It makes writing C++ code with native R objects a breeze. Even John Chambers is unhappy with the lack of elegance in the R/C interface. Rcpp uses some of the more advanced language features in C++ to abstract away all of the ugliness. RInside on the other hand embeds R within a C++ program.
The steps below will show you how to link up Eclipse with Rcpp to get code completion and syntax error detection, then RInside will be used to link up R with Eclipses build and run systems allowing for incremental building and rapid prototyping.
Step 1: Download Eclipse
You will need to download the CDT version of eclipse for c/c++ development. It can be obtained at.
Step 2: Install statet
statet is an eclipse plug-in supporting R integration. Follow the installation instructions at. R will need to be configured, which is covered in section 3 of Longhow Lam’s user guide.
Step 3: Install Rcpp and Rinside
In R run:
install.packages(c("Rcpp","RInside"),type="source")
Step 4: Create a skeleton for a new C++ project
- Right click on the Navigator area and select New -> C++ Project.
- Name the project MyCppPackage and click Finish.
- In R create a cpp package skeleton with the following code:
library(Rcpp) Rcpp.package.skeleton("MyCppPackage")
- In the file system navigate to your R working directory. There you should find a new folder labeled MyCppPackage. Drag the contents of that folder into your project in eclipse.
Step 5: Making the package installable
Step 6: Setting up links and properties
- Right click on MyCppPackage and select properties.
- Add references to the header files for R, Rcpp and RInside to the G++ compiler includes.
/Library/Frameworks/R.framework/Resources/include /Library/Frameworks/R.framework/Resources/library/Rcpp/include /Library/Frameworks/R.framework/Resources/library/Rcpp/include/Rcpp /Library/Frameworks/R.framework/Resources/library/RInside/include (note: these may be different on your system depending on your R_HOME and library paths)
- Add a reference to the R library to G++ linker – Libraries.
- Add linkages to the Rcpp and RInside libraries to G++ linker – Miscellaneous
/Library/Frameworks/R.framework/Resources/library/Rcpp/lib/x86_64/libRcpp.a /Library/Frameworks/R.framework/Resources/library/RInside/lib/x86_64/libRInside.a
- Add the “-arch x86_64” architecture flag for g++ compiler. This option is found in the Miscellaneous settings. If your computer’s architecture is different, set the flag accordingly.
- Set the g++ Compiler – Preprocessor symbol INSIDE. This is used in the main.cpp file in the next section.
Step 7: Enabling building and launching
- Create a new c++ file main.cpp in the src folder with the following code
#ifdef INSIDE
#include
#include // for the embedded R via RInside #include "rcpp_hello_world.h"
using namespace Rcpp; using namespace std;
int main(int argc, char *argv[]) { RInside R(argc, argv); // create an embedded R instance SEXP s = rcpp_hello_world(); Language call("print",s); call.eval(); return 0; }
#endif
- Execute Project – “Build All”. You should see the project building in the eclipse console, ending with **** Build Finished ****.
- Next, go to Run – “Run Configurations”.
- Create a new C++ run configuration set to launch the binary Debug/MyCppPackage
- Hit run. You should then see the binary building and running. The output of main.cpp will be emitted into the Eclipse console. This allows you to do rapid prototyping of c++ functions even if they require the full functionality of R/Rcpp.
You can also make use of Eclipse’s extensive and very useful code sense to both detect errors in your code, and to assist in finding functions and methods. ctrl+space will trigger code completion
Final thoughts
Rcpp has made R package development with C++ code orders of magnitude easier than earlier APIs. However, without the features modern IDE, the developers life is made much harder. Perhaps all the old school kids with Emacs/ESS have trained their brains to not need the features I outlined above, but I am certainly not that cool. I found that I was at least 4-5 times more productive with the full Eclipse set-up as I was prior.
After following the steps above, you should have a template project all set up with Eclipse and are ready build it out into your own custom Rcpp based package. These steps are based on what worked for me, so your milage may vary. If you have experiences, tips, suggestions or corrections, please feel free to post them in the comments. I will update the post with any relevant changes that come up.
Update: If you are having trouble with your standard headers, this SO post may be helpful
Update: Windows users may find this SO helpful
————————————–
Fellows Statistics provides experienced, professional statistical advice and analysis for the corporate and academic... | https://www.r-bloggers.com/eclipse-rcpp-rinside-magic/ | CC-MAIN-2018-47 | refinedweb | 1,124 | 64.91 |
SSL.clientConnection: Session tickets (RFC 4507 and RFC 5077).
Client side support for session tickets.
Implementation only verified against itself.
Backported from 95ad6e4388b6576d7012110efe0edb3479a8422f by Tobias
Josefowitz..
Backported from 372b2a05d05fa0d0e052e6634d2acf8d03629ed4 by Tobias
Josefowitz.
Documentation [SSL]: Fixed typo.
SSL.Context: Fix typo causing compilation failure
SSL.Constants: Renamed some EdDSA-related constants for consistency.
SSL.Context: get_signature_algorithms() now knows about ed25519.
SSL.Context: Fixed another place.
SSL: Use SignatureScheme instead of array({Hash,Signature}Algorithm).
SSL.Context: Updated cipher_suite_sort_key() to new HASH_*.
Default to keylength 256 in configure_suite_b()
Merge remote-tracking branch 'origin/8.1' into peter/travis
Sparse list of version support added.
Implemented supported_versions
SSL: Survive Context()->ecc_curves being empty.
Fixes some more of [bug 7825].
Fixed autodoc.
Use random_string instead of Crypto.Random.random_string
SSL: Prefer AEAD suites to CBC suites of double the key length.
This makes eg AES128/GCM to be preferred to AES256/CBC.
SSL.Context: Fixed documentation typo.
Rename preferred_auth_methods to client_auth_methods, and fill it with actual certificate type information.
Updated comments and types.
Get rid of the undefined authlevel that used to be the default.
SSL.Context: Deprecated variable require_trust.
Setting of this variable is now equivalent to setting the
auth_level to AUTHLEVEL_require.
Added AUTHLEVEL_verify to documentation and compat.
SSL.Context: Fixed bug in setter for encrypt_then_mac.
Stop supporting compression by default.
SSL.Context: TLS 1.1 and before don't support hashes other than md5 and sha1.
Improves interoperation with some versions of OpenSSL.
SSL.Context: Added some references to RFCs.
SSL.Context: Added some documentation for trusted_issuers_cache.
Fix documentation issue.
SSL: Encrypt then MAC mode is an RFC now...
Rename HASH_sha to HASH_sha1.
NSA IA now only recommends AES-256, P-384, SHA-384, 3072+ bit DH, 3072+ bit RSA
Documentation fix.
A very, very small fix.
Missed a sentence.
Allow fine grained control over what extensions to use.
SSL.Context: Added option to disable renegotiation.
This is a feature required by HTTP/2 (RFC 7540 9.2.1).
Disable extended master secret extension by default. It isn't standardized yet, and currently doesn't interopt with Chrome.
Truncated HMAC may be a security issues, and isn't really supported by anyone else. Disable it by default.
Documentation updates.
Merge branch '8.1' into per/substrings
Comment update
Support linking direct to RFC anchor.
Use @rfc{@} autodoc syntax.
SSL.Context: Default to the FFDHE2048 group.
Changes the default DHE group from MODP group 24 to FFDHE2048.
This makes SMACKTest () happy, and reduces
the risk of precalculated attacks against the MODP group.
Do the cheap test before the expensive one.
Removed unused variable.
SSL.Context: Block RC4 a bit more.
TLS 1.3 prohibits RC4.
SSL.Context: Fixed warning about unused variable.
SSL [SNI]: Match against specific globs before the fallback glob.
Fixes glob cert matching when there also are fallback ("*") certificates.
Indentation fix.
Be less aggressive with when to prune old sessions.
Keep track of Session activity, so they can be removed when inactive, not just old.
SSL.Context: Reduce aggressivity of purge_session() for <= TLS 1.2.
In TLS 1.2 and earlier it is possible to have multiple concurrent
connections using the same session. In particular there may be a
concurrent connection performing session resumption handshaking
at the same time as the session is being purged.
Fixes "Internal server error: Bad argument 1 to sizeof()." in
__builtin.Nettle.Hash() called via Connection.hash_messages(),
which was often triggered by Google Chrome.
Optimize export crypto a bit for the testsuite.
No one is seriously using export ciphers, so stop optimizing them and throw out some code. (My desktop is doing 710 keys per second)
Don't use RC4 by default.
SSL.Context: Added support for private FFDHE-groups.
SSL.Constants: Added KE_rsa_export.
This is in preparation for breaking out the export-RSA handshaking
from KeyExchangeRSA.
Remove trailing white spaces.
Moved common preprocesor defines to tls.h
Added support for DHE PSK.
Return appropriate alert if key id or hint was not recognized.
Some documentation. Perhaps we want to move all this to an abstract class PSKContext?
Support for plain PSK.
SSL.Context: get_suites() now also filters on the version range.
Updated comment.
Deprecated verify_certificates, as auth_level does the same thing. This breaks some tests that appears to be incomplete, so disable them.
SSL: Support the Negotiated FF-DHE Parameters draft.
NB: This draft has been incorporated into the TLS 1.3 draft.
OO more.
UUID v4 is essentially just an random string, so let's use random string directly instead.
SSL.Context: Ensure that session identifiers are unique.
Now uses Standards.UUID to generate the session identifiers.
This works around a bug in the testsuite where session identifiers
apparently could be reused.
SSL.Context: purge_session() now works client-side too.
Moved deprecated methods to compat.
Make TLS 1.0 loweset default TLS in Pike 8.0 too.
Put the default lower version at TLS 1.0. IE users on pre XP need to upgrade.
Added get_certificates().
Merge remote-tracking branch 'origin/8.0' into string_alloc
Conflicts:
src/stralloc.c
Allow add_cert private key to be a DER encoded string.
Select DH group based on symmetric key strength.
Silence type warning when Crypto.ECC.Curve is missing (old nettle)
filter() seems to get the return type wrong.
SSL: Updated to the new Crypto.Sign API.
Make heartbleed probing optional and default off.
Improved some comments.
No SNI in Pike 7.8.
These didn't exists in 7.8, so no compat.
Refactored certificate lookup.
OO harder. Let CertificatePair sort themselves according to perceived certificate strength.
Moved and trimmed code to generate CipherPair glob array to separate function.
Sort Context items into Global, Cryptography, Certificates/authentication and Sessions
SSL.Context: Added get_signature_algorithms().
Also extends the documentation for the signature_algorithms
variable a bit.
SSL: Support EXTENSION_encrypt_then_mac.
This draft extension improves security for old CBC suites by
hashing the encrypted data including the padding. This works
around the various TLS padding attacks.
sslfile -> File and sslport -> port
Removed #if 0 code.
Don't use dsa-sha512 is there is no PKCS id for it.
Fixes for Nettle < 2.1 and Nettle < 2.8
Have list of acceptable hash-signature-pairs in context.
SSL.ClientConnection: Improved SNI API.
Made SNI handling an explicit argument to create(), to allow for using
the same SSL.Context for client connections to multiple servers.
Documentation and debug updates.
SSL: Added support for the ChaCha20-Poly1305 suites.
Don't assume zlib.
0..255 -> 8bit
import .
Renamed SSL.context to SSL.Context. | http://pike-librarian.lysator.liu.se/log.xml?module=pike.git&file=lib/modules/SSL.pmod/Context.pike | CC-MAIN-2020-05 | refinedweb | 1,078 | 55.3 |
the search icon without entering a search term. It gives you a few more options to restrict your search to different namespaces. Tick the boxes for namespaces you wish to search. If you want a different default setting for these, go to Special:Preferences and the 'Search' tab. Note: Searching all namespaces might be the most logical thing to do. In fact the latest versions of MediaWiki have that as the default.
The wiki is divided into namespaces. Most content is on the 'Main' namespace, although there's a fair amount of wiki discussion taking place in the 'Talk' namespace. Note that this is not the same thing as the 'talk' mailing list (see below)
The wiki has namespaces for some languages, which means you can now search only the german language pages by ticking the DE namespace for example.
If your search term is hitting upon an exact page name match, but you wanted a search, then you can select from the drop down which appears while you are type. Select "contain x..." at the bottom. Alternatively enter the advanced search screen rather than using the little search box.
Use google instead
You might prefer to use google, since it sometimes indexes stuff better than the wiki search mechanism (although it's not quite as current) More importantly...
Google the whole site
The custom google search set-up at a will google the wiki, mailing lists and forum all at once. There is a treasure trove of information buried in discussions on our Mailing lists.
If you do find some useful information which is not in the wiki, it probably should be added somewhere. You could add it! Editing the wiki is easy! | https://wiki.openstreetmap.org/wiki/Searching_the_wiki | CC-MAIN-2019-09 | refinedweb | 284 | 73.47 |
Asked by:
Windows 10 Group Policy Issue
Hi,
Not sure if there is another thread for this... but we are having the issue described in this spiceworks forum.
Computer policy could not be updated successfully. The following errors were encountered:
The processing of Group Policy failed. Windows attempted to read the file \\domainname.local\SysVol\domainname.local\Policies\{7FF124FD-A2DC-4F70-BAB1-9B17F4754C1E}\gpt.ini from a domain controller and was not successful
Will there be a proper update to sort this out? The registry entries make it work in the interim.
Kind Regards,
John
- Edited by Brandon RecordsMicrosoft contingent staff Thursday, December 03, 2015 8:38 PM Made link clickable.
- Moved by Brandon RecordsMicrosoft contingent staff Thursday, December 03, 2015 8:38 PM Moved to more appropriate forum.
Question
All replies
Hi John,
This issue can be caused by Remote Registry and DFS namespace services on the server.
Please check the status of these two services and make sure they are set to start automatically.
Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact tnmff@microsoft.com.
Hi,
I've checked these services on both our DC's and they are fine.
Setting the registry items as per the spiceworks article sorts it, but surely that can only be a temporary fix...
The issue is only with Windows 10 machines.... Windows 7 and 8.1 are fine.
Kind Regards,
John
Hi John,
As can been seen from the link mentioned in your post, it is a known issue and for now, there is no solution yet. We will keep an eye on this and wait for the release of a solution.
Please remember to mark the replies as answers if they help and un-mark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.
- Proposed as answer by Wendy JiangMicrosoft contingent staff, Moderator Thursday, December 10, 2015 6:08 AM
- Unproposed as answer by Amy Wang_Microsoft contingent staff, Moderator Thursday, December 10, 2015 6:49 AM
Hi,
Just a thought although it is apparently a known bug in windows 10 for UNC hardening to be enabled surely it should work...
Just a thought... Our domain functional level is still server 2003 as when I put our last domain controller into action (we currently have server 2012 and server 2008 R2) we were getting rid of our last server 2003 servers. It would seem we are also using FRS rather than DFS.... Does UNC Hardening need DFS?
Kind Regards,
John | https://social.technet.microsoft.com/Forums/en-US/24f7c3ed-1333-43c2-a7be-721dce0f163e/windows-10-group-policy-issue?forum=winserverGP | CC-MAIN-2018-17 | refinedweb | 438 | 64.91 |
Hi everyone.
In this article, I am going to walk you through the step-by-step procedure of how to control or blink an LED using the BBC micro:bit and make a traffic light system using micro:bit. Basically, I will explain how to control the LED using Micro:bit on a solderless breadboard and how to control brightness. If you're a beginner and if you don't know about micro:bit much, then please go through the articles I have posted here: About Micro:bit
So let us get started.
Tools You Need
- Micro:Bit (1)
- AA batteries (2)
- Alligator clips (4)
- Jumper wires (4)
- Resistor of 220 ohm or 470 ohm (3)
- Breadboard (1)
Connection
We need to connect the GND to any one of the terminals of the breadboard so that we can use it as GND to connect GND of the LEDs.
Our connection looks something like this. We only need to supply 3V, so we need to use the resistors so that we can limit the current to 3v only. 470 ohm is best but you can use 220 ohms also. The picture below shows the connection for only one LED.
For this, what I have done is connected PIN0 to the left-hand side of the resistor, so we need to connect the right side of the resistor to the +ve of the LED and -ve of the LED connects to the GND which is the last row of the breadboard.
Similarly, we need to connect two more LEDs, as shown below.
So this is how I have connected all three LEDs to my micro:bit.
So let us now see the coding part of this project using makecode and later we will be using micro python.
Makecode
Step 1
Go to makecode or download Windows 10 makecode app for micro:bit, if you're using Windows 10.
Step 2
Create a new project.
Step 3
Go to Basic and choose forever block.
Step 4
Click on Advanced and go to Pins. Then digital write pin block and place it inside the forever block and provide some delay, too.
We know 0 is low and 1 is high. So when we set PIN to 0, then it will turn off the light and when we set PIN 1 to 1, then it will turn on the LEDs. This is the code for only one LED; similarly we can code by changing the pins of the micro:bit.
Full code
So in the above code, first I am turning on the PIN0 for 4 secs and turning it off for 1 sec, and the same goes for PIN1 and PIN2 respectively. Now let us see the microPython code.
microPython Code
1. Open your mu code editor and create a new project.
2. Import the micro:bit libraries.
from microbit import *
The above code will load the libraries we need to code the micro:bit.
3. Now we need to create a loop for turning on and off the LEDs. So we will make a while loop like this:
while True: pin0.write_digital(1) # turn pin0 (and the LED) on sleep(4000) # delay for half a second (4000 milliseconds) pin0.write_digital(0) # turn pin0 (and the LED) off sleep(1000)
So the above code will turn on PIN0 for 4 seconds and again turn it off for 1 sec like this.
Full code
from microbit import * while True: pin0.write_digital(1) # turn pin0 (and the LED) on sleep(4000) # delay for half a second (4000 milliseconds) pin0.write_digital(0) # turn pin0 (and the LED) off sleep(1000) pin1.write_digital(1) # turn pin1 (and the LED) on sleep(4000) # delay for half a second (4000 milliseconds) pin1.write_digital(0) # turn pin1 (and the LED) off sleep(1000) pin2.write_digital(1) # turn pin2 (and the LED) on sleep(4000) # delay for half a second (4000 milliseconds) pin2.write_digital(0) # turn pin2 (and the LED) off sleep(1000)
Javascript code
basic.forever(() => { pins.digitalWritePin(DigitalPin.P0, 1) basic.pause(4000) pins.digitalWritePin(DigitalPin.P0, 0) basic.pause(1000) pins.digitalWritePin(DigitalPin.P1, 1) basic.pause(4000) pins.digitalWritePin(DigitalPin.P1, 0) basic.pause(1000) pins.digitalWritePin(DigitalPin.P2, 1) basic.pause(4000) pins.digitalWritePin(DigitalPin.P2, 0) basic.pause(1000) }) | https://microbit.hackster.io/anish78/traffic-light-system-using-bbc-micro-bit-da2f47 | CC-MAIN-2019-09 | refinedweb | 713 | 73.27 |
Hi,
Before starting, please know that I am a complete begginer in programming (and not english native speaker)
I’m trying to build a simple small project using :
Arduino Uno
Mini bread board
Led
Servo
Ultrasonic sensor (4 pins)
I found several videos on youtube and managed to salvage some code parts, yet i’m strugling with 2 parts in my code
Here’s the goal of the project :
IF something is a detected by sensor (less than 20cm)
for at least 10 seconds
and ONCE it goes away for at least 10 seconds
THEN light up led and move servo for 3 seconds
then servo goes back to original positions
My problems :
- What does buffer means ? I can not understand what it is used for ? Is there another way easier to write what it does ?
- On my code, servo is triggered even in objet is still in front of sensor
Here is the code :
#include <Servo.h> // servo library Servo servo1; //name servo int buffer; //two more integer variables we will use as buffers const int led = 2; const int trigPin = 3; const int echoPin = 4; long duration; int distance; void setup() { pinMode(trigPin, OUTPUT); pinMode(echoPin, INPUT); servo1.attach(5); //set the servo to pin 5 pinMode(led, OUTPUT); //set the led pin as an); if (distance< 20) flusher(); //if the reading is less than 20 start the flush function else //if the reading is not less than 20 { buffer--; //decrease the buffer if (buffer < 0) buffer = 0; //make sure the buffer cant be less than 0 servo1.write(360); //put the servo in the far right position digitalWrite(led, LOW); //turn off the LED } delay(1000); //wait a 1 second before checking again } void flusher() { buffer++; //increase the buffer counter if (buffer > 15) //if the buffer counter is over 15 (which would be 1500 or 1.5 seconds) { servo1.write(41); //put the servo in the far left position digitalWrite(led, HIGH); //turn the led on delay(1000); //wait one second servo1.write(360); //put the servo in the far right position delay(3000); //wait 3 second buffer = 0; //reset the buffer } }
How could I improve this code and make it work for what I need ?
Thanks in advance for the help
| https://forum.arduino.cc/t/simple-code-help-needed/503524 | CC-MAIN-2022-27 | refinedweb | 375 | 55.71 |
This article will learn to work with graphical LCDs on the example of the Nokia 5110 screen. This is a rather popular display, which stands out for its low cost and ability to display in a convenient form not only text but also graphical data (graphics, images, etc.). The resolution of the Nokia 5110 screen is 48×84px. We will learn how to connect the Nokia display to the Arduino and give an example of a sketch to work with it.
Connecting the 5110 Display to the Arduino
To begin with, let’s look at connecting this display to the Arduino and look at the data interface. The display board has 8 pins:
- RST – Reset;
- CE – Chip Select (device selection);
- DC – Data/Command select (mode selection);
- DIn – Data In (data);
- Clk – Clock (clocking signal);
- Vcc – 3.3V power supply;
- BL – Backlight 3.3V;
- GND – grounding.
As you have already noticed, the display (Vcc) should be powered with a voltage no higher than 3.3V; the same voltage is maximum for backlighting the display (BL). However, the logic outputs are tolerant of the 5V logic used by Arduino. However, it is still recommended to connect the logic pins through 10 kOhm resistors so that you can extend the life of the display.
It should also be noted that there are versions of displays (usually with a red board) with LIGHT output instead of BL. In this case, you can turn on the backlight by connecting this output to the power minus (GND).
Pin RST (active LOW) is responsible for rebooting the display, and with the help of pin CE (active LOW), the display controller is informed that the data exchange occurs with it. DC input is responsible for the input mode – data input or command input (LOW – data, HIGH – commands). Clk input allows the display controller to determine the data rate, and through pin DIn, the data is directly transferred to the display controller.
Sketch and Library for Work with the Display
To work with this display there are many libraries, but we will use a very simple and functional library
Let’s consider the work with the display using this library on the example of a simple sketch:
#include <LCD5110_Basic.h> LCD5110 LCD(7, 6, 5, 4, 3); //include the display with the pins of connection extern uint8_t SmallFont[]; // specify the presence of an array with font SmallFont in the library extern uint8_t MediumNumbers []; // specify the presence of an array with font MediumNumbers in the library void setup() { LCD.InitLCD(); //initialize display } void loop() { LCD.disableSleep(); //display out of sleep mode LCD.clrScr(); //cleaning display LCD.setFont(SmallFont); // install font SmallFont LCD.print("Hello World!", CENTER, 2); //return "Hello World!" on the second line with center equalization LCD.setFont(MediumNumbers); // set font MediumNumbers for (int i=0; i<=5; i++) { LCD.clrScr(); //cleaning the screen LCD.print(i, CENTER, 20); // Output the value of i in the center of 20 lines delay(1000); } LCD.enableSleep(); // put the display in sleep mode for a long pause delay(5000); }
After we have considered the library’s basic functions, let’s take a closer look at the drawBitmap function and consider the features of displaying images on the screen.
To start with, we will need the image of interest in .bmp format.
Then you need to download the program for generating images. In the program window, set the necessary resolution of our image on display (should be less than 84 pixels horizontally and 48 vertically).
Then we get an array and copy the appeared array to a new sketch.
#include <LCD5110_Basic.h> LCD5110 LCD(7, 6, 5, 4, 3); //announce the display indicating the connection pins static const char lcd_image_mas[288] = {} // image array void setup() { LCD.InitLCD(); //initialize display } void loop() { LCD.clrScr(); //cleaning display LCD.drawBitmap(18, 0, lcd_image_mas, 48, 48); //retrieve the image from an array of 48x48 pixels starting from the point 18x0 LCD.enableSleep(); // Enter display into sleep mode while(1); }
Conclusions
In this way, we reviewed in detail the basic capabilities of the Nokia 5110 display using the
LCD5110_Basic library, learned how to quickly and easily display your own images on the screen, and understood the nuances associated with connecting the display to the Arduino platform. | https://nerdytechy.com/connecting-nokia-5110-lcd-with-arduino/ | CC-MAIN-2021-31 | refinedweb | 708 | 61.97 |
grp.h - group structure
#include <grp.h> *); [TSF]
int getgrgid_r(gid_t, struct group *, char *, size_t, struct group **); int getgrnam_r(const char *, struct group *, char *, size_t , struct group **);int getgrgid_r(gid_t, struct group *, char *, size_t, struct group **); int getgrnam_r(const char *, struct group *, char *, size_t , struct group **);
[XSI][XSI]
struct group *getgrent(void); void endgrent(void); void setgrent(void);struct group *getgrent(void); void endgrent(void); void setgrent(void);
None.
None.
None.
<sys/types.h>, the System Interfaces volume of IEEE Std 1003.1-2001, endgrent(), getgrgid(), getgrnam()
First released in Issue 1.
The DESCRIPTION is updated for alignment with the POSIX Threads Extension.
The following new requirements on POSIX implementations derive from alignment with the Single UNIX Specification:
-
The definition of gid_t is mandated.
-
The getgrgid_r() and getgrnam_r() functions are marked as part of the Thread-Safe Functions option. | http://pubs.opengroup.org/onlinepubs/009604599/basedefs/grp.h.html | CC-MAIN-2019-30 | refinedweb | 139 | 62.58 |
>>, great for those fed up with J2EE. (Score:5, Interesting)
Even when using newer frameworks like Spring, Tapestry and Hibernate (I hate you so much Struts) Rails still manages to be easier.
I highly suggest any developers looking for a change of pace at least give Ruby on Rails a few hours of your evening. While it's not nearly as comprehensive as Java, it's gaining libraries and functionality by leaps and bounds.
And just so I don't get labeled as a Rails fanboy/Java basher: Rails is not perfect, I still would recommend using J2EE for large corporate projects. It's just a much more mature solution with less unknowns. I think Rails needs another year at least before people are ready to really give it a shot in the corporate environment.
Re:Rails, great for those fed up with J2EE. (Score:3, Interesting)
RoR, IMHO, is a major step forward to web deployed applications becomming mainstream.
Re:Rails, great for those fed up with J2EE. (Score:2)
Re:Rails, great for those fed up with J2EE. (Score:2)
Damn right! Databases all ought to be like Oracle, where even typing in a query is a hellish quest involving obscure replacements for DNS (tnsnames), client software that's incompatible when even a minor versionnumber changes, convoluted connectstrings and non-gui client tools (un
Re:Rails, great for those fed up with J2EE. (Score:2)
Seriously, I don't know how Oracle gets away with sqlplus... Would it be *that* hard to add readline support?
Re:Rails, great for those fed up with J2EE. (Score:2)
readline is also obsolete. (Score:2)
Re:Rails, great for those fed up with J2EE. (Score:2)
Oracle's "brilliant" product for developers - Developer 2000 - involved TWO - count 'em! - TWO 800 page books on how to develop forms.
Forms which have absolutely NO WAY to be documented as to how they are constructed (other than printing out individual screens of trigger code and the like.)
One of the most pathetically incompetently designed products I've ever seen.
Anybody who uses Oracle (other than the database itself - with nothing else) is out of their minds.
Re:Rails, great for those fed up with J2EE. (Score:3, Interesting)
Our company recently tried to do a web-project (workflow management application for a publishing house) based RoR. It was a spectacular failure - LOTS of things are mostly absent from RoR: caching and transaction support, object-relational mapping is inferior (yes, ActiveRecord is NOT enough), etc.
RoR is nice, but it needs lots of polishing and some redesign. In its present state RoR can't be compared with J2EE solutions, they are far m
Re:Rails, great for those fed up with J2EE. (Score:5, Informative)
Re:Rails, great for those fed up with J2EE. (Score:2)
And Ruby's transaction support is very limited, for example it's impossible to detach record from a transaction, save it to session and then reattach this record to a new transaction (with concurrency control based on timestamps/verisons, of course). Hibernate ( [hibernate.org]) supports this, BTW.
Re:Rails, great for those fed up with J2EE. (Score:4, Informative)
Re:Rails, great for those fed up with J2EE. (Score:2)
Yes, you are talking out of your ass. (Score:2)
Re:Yes, you are talking out of your ass. (Score:2)
Usualy cache coherence is ensured using distributed evictions (like in SwarmCache) or clever locking strategies (like in Coherence). Most of this can be abstracted into separate layer, but still some interaction from the host container is required.
What are you talking about? (Score:3, Informative)
Re:Rails, great for those fed up with J2EE. (Score:4, Interesting)
Ruby can't do complex things java can??? You meant rails, probably, and such confusion of terms is not a good sign.
Have you checked out the latest rails versions' API? I see transaction support and caching of db data and cgi actions too.
As for the 'inferior' object relational mapping: indeed Active record tries to keep things simple: I'm grateful for it. Rails developers got too far sometimes, as you see if you have a column named 'type' in your tables
But, that's not being inferior, it's being different. If your app requires convolute mappings, either extend active record to suit your needs or do without it (possibly dropping rails altogether and wasting precious ram with a JVM
Re:Rails, great for those fed up with J2EE. (Score:3, Interesting)
Re:Rails, great for those fed up with J2EE. (Score:2, Insightful)
The moral is, no matter how complex a system build on Ruby will get, it will always be more simple to use than a system build on Java, just because Java carries the characteristics of a systems programming language while Ruby carries the characteristics of a scripting programming language.
Re:Rails, great for those fed up with J2EE. (Score:3, Insightful)
Advantages of dynamic languages (Score:3, Insightful)
Re:Rails, great for those fed up with J2EE. (Score:2)
I'm just saying that Ruby in its current state can't really handle complex web-applications. I don't say anything about future RoR versions.
Active record tries to keep things simple, yes. But sometimes things just can't be simple: we've had lots of problems with cascaded deletes/updates, inverse mappings and bi-directional structures. Finally, we just used Active records like a plain SQL query engine with little additional benefit.
Re:Rails, great for those fed up with J2EE. (Score:2)
By saying "Ruby doesn't have ____" and being shown to be wrong? Heh.
As for being able to handle complex web apps, depends on your definition, I suppose. I'd certainly consider things like Basecamp [basecamphq.com] to be a "complex web app," but perhaps Java lets sites like that remotely read your mind using ESP or something else nifty.:4, Interesting)
This, I think, is the crux.
My company has a library, too, that makes certain assumptions about the DB. We're really wicked-fast when using it, when building an app from the gound up. It has hooks for overriding some assumptions, so we can shoe-horn it in to some other projects. But if the DB is hopeless, the game is over, and we have to do things like everyone else.
And nearly every company out there has a hopelessly messy DB, that can't be refactored because of X, where X is legacy apps, no money, management resistance, [...]
Hell, even Hibernate/middlegen has a problem related to this: all it takes is one clueless app developer that scorns DB constraints, and you have a Situation that can cost 10s of K to fix.
Rails is neat (I'm a pretty big perl bigot, and I like it), but it isn't designed for integration. Folks playing around with it should recognize that up front, so that they don't try to do the wrong thing with it.
Re:Rails, great for those fed up with J2EE. (Score:5, Interesting)
True, you can't just drop J2EE on your desktop because there's no such _thing_ as J2EE. J2EE is a set of standards (which contains just about everything).
The only things you need to start developing J2EE applications are: Tomcat ( [apache.org]), optionally a web-framework (like [apache.org]) and you can start developing tomorrow (if you know Java of course) and a decent IDE ( [eclipse.org]). It will cost you about $0.
Java has some metaprogramming featues starting from version 1.5. Right now we're writing application in C++ and Python, so I don't miss metaprogramming features
RoR is extensible, but some features are just very hard to implement: maintaning persistent object identity, complex mappings support, distributed caching and long-running transactions with optimistic locking.
We had previous expirience in dynamic languages (Python, Perl, PHP). This project was a sort of expirement - we wanted to see what can be done with RoR.
Re:Rails, great for those fed up with J2EE. (Score:3, Insightful)
You forgot the "learn J2EE" part, which is going to be a task at least a magnitude more complex than learning Java itself.
Re:Rails, great for those fed up with J2EE. (Score:3, Insightful)
Rails itself could be put on top of any persistence layer. Instiki uses Madeliene instead of AR and it works fine. It just comes, o
Re:Rails, great for those fed up with J2EE. (Score:2)
workflow, caching, object based database, transaction, etc. I don't know if it's easier than Java, but it's easy enough for me.
Re:Rails, great for those fed up with J2EE. (Score:2)
No, you hold the hype for 3 months. (Score:5, Insightful)
Re:Rails, great for those fed up with J2EE. (Score:2)
I guess what I really want is a Java equivalent of Rails. Java On Crutches or something like it.
P.S. Slashdot just said:
Fucktards.
Re:Rails, great for those fed up with J2EE. (Score:2)
It uses a lot of assumptions and works best with MySQL. Once you start using it with a legacy database and start
Re:Curious (Score:2)
I've been working with struts as of late, and although setting things up can be a little tedious, what specifically don't you like about it?
Re:Rails, great for those fed up with J2EE. (Score:2)
Neither should it be to wipe out your database by setting the rake testing database to the same as you store your important data in.
Re:Rails, great for those fed up with J2EE. (Score:2)
Get real. (Score:2)
Re:Get real. (Score:2)
I suppose the 3 interviews and 2 job offers I recently got for sysadmin positions with heavy Tomcat must be an illusion.
Yeah, you're right, nobody is using it.
Read harder. (Score:2)
Substitute for s (Score:2, Interesting)
Re:Substitute for s (Score:2)
BTW I recommend giving rails a try, it's really a well thought out environment for your web apps. The site linked in my sig is a quick and dirty powerdns + lighttpd + rails experiment on a debian UML host (still on 2.4)
Ruby on Rails as a threat to PHP? (Score:5, Insightful)
Re:Ruby on Rails as a threat to PHP? (Score:2)
And what transition would that be, excatly? PHP5 is almost completely back-compatible with PHP4.
Re:Ruby on Rails as a threat to PHP? (Score:3, Interesting)
Re:Ruby on Rails as a threat to PHP? (Score:3, Funny)
Re:Ruby on Rails as a threat to PHP? (Score:2)
Also, PHP is already a larger language than perl,
having 3,000 built in functions.
And worse, it still doesn't have namespaces.
Thankfully PHP 5 actually has some decent OO features.
Rails book from the Pragmatic Bookshelf (Score:4, Informative).
Extract from Web 2.0 chapter available there (Score:2)
As mentioned in Curt's great article, the Agile Web Development with Rails (beta) book has a nice chapter on Ajax support. You can even get an extract of the chapter at the pragmatic programmer's site: PDF Extract of Chap 18: Web 2.0 [pragprog.com]
Figure 18.1 should make Ajax clear. The book is highly recommended, and the 2nd Beta was just released last week.
Which is the bigger irony: (Score:4, Insightful)
b) Microsoft's own technology being used by Google to loosen Redmond's deathgrip on the market?
Re:Which is the bigger irony: (Score:3, Interesting)
This isn't quite correct. IFrame and hidden IFrame communication was invented before that. The catch is that browsers weren't stable enough or compatible enough to make use of these channels.
XMLHttpRequest does more or less the same thing as an IFrame (via an ActiveX contarol), except that it adds the over
Re:Which is the bigger irony: (Score:2)
That't a pity...
Go try it at [google.com]
Re:Which is the bigger irony: (Score:2)
Re:Which is the bigger irony: (Score:2)
Re:Which is the bigger irony: (Score:3, Informative)
Google Suggest uses XMLHttpRequest, while Google Maps uses a iframe
Re:Which is the bigger irony: (Score:2)
No it doesn't. There is no requirement to actually request XML. Indeed many uses of it do not use XML at all. So far, none of mine use XML.
Re:Which is the bigger irony: (Score:2)
Microsoft's own technology being used by Google to loosen Redmond's deathgrip on the market
This is nothing new to Microsoft - they have long been creating tools for their own competitors. Microsoft create a platform and sell development tools for the platform. However MS is also an ISV for that same platform (e.g. MS Office). Hence there is an inherent conflict of interest - the platform side is developing and selling the tools that will be used by competitors to compete with the ISV side.
This is one o
Re:Which is the bigger irony: (Score:2)
Re:Which is the bigger irony: (Score:2)
Dont Forget Zope (Score:4, Insightful)
On the other hand remember Zope - If you can get your head around Aqusition, the ZODB and Product Deveopment then Zope is a super-fast development platform.
Re:Dont Forget Zope (Score:3, Interesting)
I recenty became the web administrator at a small university and the college I work for uses Zope. I knew a little Zope and Python beforehand and it helped me get the job. I was all hot and heavy to switch them to a PHP/MySQL solution, though my first love is Perl. Doing stuff in PHP was fast. As I studied Zope and Python more and more I came to realize that my initial impre
Re:Dont Forget Zope (Score:2)
I said small university. I am the team.
What would you recomend?
A few of them there know Zope but not Python. Since Plone doesn't cost anything I'm not wasting their money. If Python is good enough for Google and ILM, it's good enough for me. I'm not wasting their time. They already have a history with Zope. Plone was
it's an illusion alright (Score:4, Funny)
It's illusory alright, when I start at the US and scroll due west the first thing that I come to is the UK. Where'd all the other countries go?
Re:it's an illusion alright (Score:5, Funny)
Re:it's an illusion alright (Score:2)
Wherever you threw your eyeballs I suppose. The first country to appear should be Ireland (not taking smaller islands into account).
Thomas-
Re:it's an illusion alright (Score:2)
Best to read these things closely before you start hurling around insults.
And the funny thing is... (Score:2, Insightful)
Re:And the funny thing is... (Score:2)
Um, was that actually hated by anybody? Did anybody know about it except Microsoft?
I think IE is hated for its complete lack of support for just about anything standard and less so for ITS non-standard features - especially the one nobody knew about (until it became useful.)
AJAX meme (Score:3, Informative)
However, Ruby on Rails is clearly rising,
moving steadily upward for over a year. Thanks to a reader for bringing this to my attention.:AJAX meme (Score:2)
Rails changes the whole Web development game (Score:4, Interesting)
I've also developed a large marketing system for the restaurant industry in Rails which lets restauranteurs develop e-cards, e-gifts, and send them to their customers on certain days.. or certain days away from their birthdays, etc.. and that will be going fully live soon.
My 10,000 user strong RSS Digest [bigbold.com] will be making the leap to Rails soon (July 1st) and this is a system driving over half a million uses a day.
I developed a del.icio.us-style tagged Code Snippets [bigbold.com] site in Rails within two days! It's had further refinements since then, but less than two weeks after launch, it was getting thousands of pageviews a day and hundreds of visitors a day from Google.
I was ready to give up development work 6 months ago, and now it's the most fun and profitable work out there for me. Ruby on Rails deserves the attention it's getting. You can put together your ideas in a fraction of the time you'd have ever imagined.
Wow.. (Score:2)
Will that be 5 or 10 years experience? (Score:5, Funny)
(To all potential employeers: I kid!)
Re:Will that be 5 or 10 years experience? (Score:2)
Hell, I was doing AJAX back in my System/32 RPG II days!
(Yeah, right! Ajax cleanser, maybe...)
(As an aside, I just read some article about some major financial company trying to get away from doing RPG II programming on one of their mainframes. I'm like, WHAT? Some asshole is STILL programming in RPG II?)
Ruby? (Score:2)
I started using Ruby a long time ago, back when no one knew about it. I liked it because it was like a better Perl (better OO support but with Perl syntax). However, I quickly tired of its lackluster performance. I mean it was a lot slower than even Perl or Python. I eventually moved on hoping to return when Rudy had matured and performance was kicking. Last time I checked the performance was the same as always. So much for the "tune
No, its still slow. (Score:2)
Re:Ruby? (Score:2)
Whether that's a good tradeoff for faster development and less maintenance time is, of course, a matter of opinion..
JavaScript libraries comparison (Score:2)
Re:JavaScript libraries comparison (Score:2)
Q: Can you mix PHP and RoR? (Score:2)
Re:Q: Can you mix PHP and RoR? (Score:3)
Hope that helps.
(This comes from someone who runs XMMS on a Mac
ASP.Net 2.0 (Score:3, Informative)
Re:ASP.Net 2.0 (Score:2)
The advantage of Ruby is the way in which the callbacks are attached to the controls. In C# or J2EE or VB you basically need to create a special type of class to handle the callback, and create an instance of it. In Ruby you basically pass in a code block representing the action you want without having to create new classes
Please explain: What is the big fat hairy deal? (Score:2)
But this is called Ajax and suddenly everyone goes crazy.
Then there is ROR. I checked Ruby on Rails about a year ago. Then again a little more just the other month. It looks like Zopes younger brother. Not half as powerfull, and 5 years to late. But with Ruby, as to add even more extra geekness or what?
Please unders
Re:Please explain: What is the big fat hairy deal? (Score:2)
Rails: It's great! (but doesn't work) (Score:2)
Whatever.
My DBD::DBI applications are able to athenticate against MySQL just fine, but this app throws large gaudy errors when trying to connect to my (non-crippled) MySQL instance. (Yes, I ran through the tutorial in the hopes that the bug would have a
PHP Rails Ripoff (Score:2)
They use the exact same Javascript library that is used in Rails as well: Prototype [conio.net].
Rails is pretty decent. I guess the only issue is performance... you pretty much have to count out your typical web hosting account and have your own server. Mod_ruby [modruby.net] pretty much takes care of the performance issues and it installed without incident in my Apache 2.xx web server wi
Re:ASP.NET (Score:2)
Re:ASP.NET (Score:2, Funny)
Re:ASP.NET (Score:2)
Yeah, proof by assertion. That must be why Slashdot, Amazon, Livejournal and zillions of other "large scale site" don't use them, or what? Amazon and Slashdot use Perl, btw...
Either one is a vast improvement over Ruby/PHP/Perl is both performance and features.
What features of ASP.NET and J2EE are so unique and essential that they make them a "vast improvement" and the only v
Re:ASP.NET (Score:3, Insightful)
You don't understand one of the most important necessary preconditions for a larger web app in corporations - someone to approve it.
J2EE and ASP.NET have rich organizations that they can loan you to take key decision makers (CFOs) out to lunch to help approve expensive J2EE projects.
Compared to the Oracle sales guy flying my previous CFO out to some g
Re:ASP.NET (Score:2)
> corporate inter/intranet site you really have two
> choices ASP.NET and J2EE.
Agree with the parent, disagree with the GP.
Any large corporation has many layers of Web presence. There's their customer-focused Internet site, and I agree it'd be brave (not necessarily foolhardy) to use Rails for that.
However, there's also a LOT of intranet stuff going on, under the covers so to speak. Every person in that corporation needs access to internal information,
Re:ASP.NET (Score:2)
By George I think he's got it!
Why was it somebody wanted to use ASP.NET?
Re:Article's examples dont work (Score:2, Informative)
Re:AJAX, not Rails (Score:2)
By George I think he's got it!
Re:Suspicious until... (Score:2)
And when was the last time you found a site that just had plain HTML - no JavaScript, no Flash, no CSS, no nothing but hand-written (in NotePad) HTML?
Face it, the world is not going to change for your PDA or cellphone.
Re:Is RoR Part of Scientology? (Score:2)
Damn you, I spit up my coffee. L. Ron Hansson?
Yes, there appears to be a core set of Rails fanboys who never miss a chance to slag off ABR (Anything But [Ruby|Rails]). This is quite sad, as the freakish hype and nonsense coming from many of these people denigrates both the general Ruby community and the truly good things in Rails.
FWIW, I hope people do not equate Railers with the more general Ruby community, which is overwhelmingly tolerant and open to new ideas and alt | http://developers.slashdot.org/story/05/06/11/1317218/ajax-on-rails/insightful-comments | CC-MAIN-2014-10 | refinedweb | 3,727 | 74.19 |
Mapping GWT RequestFactory proxies to GXT components
Mapping GWT RequestFactory proxies to GXT components
I'm trying to use TreeLoader and TreeBeanModelReader to directly map the returned beans from server. This is the code:
Code:
TreeBeanModelReader tbmr = new TreeBeanModelReader(); BaseTreeLoader<ModelData> treeLoader = new BaseTreeLoader<ModelData>(tbmr); TreeStore<ModelData> store = new TreeStore<ModelData>(treeLoader); treePanel = new TreePanel(store); //do a Request to return a list of CityProxy that implement BeanModelTag req.getAllCities(cp, "extra_param_value").fire( new Receiver<List<CityProxy>>() { @Override public void onSuccess(List<CityProxy> cities) { treeLoader.load(data); } });
All these instances are not implementing BeanModelTag since only my proxy, CityProxy implements it. TreeBeanModelReader tries to do this:
Code:
BeanModelFactory factory = BeanModelLookup.get().getFactory(beans.get(0).getClass());
Is there any way to make this work?
Thank you!
RequestFactory is a new GWT feature that relies on knowing everything there is to know about the models it mocks at compile-time, whereas the current version of GXT allows for models to be somewhat more flexible, though admittedly this is not taken advantage of for BeanModels. This difference is what leads to the issue you are encountering - GXT expects to find types that have the BeanModelTag marker interface, and GWT's RF generators don't know to add that interface.
That being said, it appears someone has come up with the changes required to make this possible with current versions of GXT.
Full support for RequestFactory and AutoBeans should be available in the next version of GXT.
Edit: Well now I feel stupid – you are the other individual in that other thread... Digging a little further, I'll reply again later if I come up with anything that can help.
Okay, looking more precisely at your issue with TreeBeanModelReader, the issue appears to be that it is trying too hard to get too precise of an instance of the factory, when you think it should settle for one further away.
The basic issue can be explained as this - If I make a model object, and tag it with the marker interface, then subclass it but do _not_ tag the subclass, the present system does not hunt it down and built it an factory - you didn't indicate that you wanted one, so it didnt make one. One can argue whether or not doing so would be a good idea on the merits of being rigorous or a bad one as it could make for some unnecessarily large code, but the point still stands - if you ask it to obtain a factory instance for you, it tries to be very precise.
My suggestion to you would be to not use TreeBeanModelReader as is, but copy and change it, replacing the possibilities for loading a factory with a factory instance that you pass in. This way, when you create a factory, you will say
TreeAutoBeanModalReader reader = new ...(BeanModelLookup.get().getFactory(MyModelProxy.class);
Using that reader will ensure that you are always using the correct factory instance. Note that RequestFactory at this time does not appear to support polymorphism, so you shouldn't have an issue with the wrong subtype of MyModelProxy being requested.
The read method in this TreeBeanModelReader could look like this:
Code:
public List<ModelData> read(Object loadConfig, Object data) { if (data instanceof List) { List<Object> beans = (List) data; if (beans.size() > 0) { return (List) factory.createModel(beans); } return (List) beans; }
As in my last post, RequestFactory entities and AutoBean instances will be supported natively in the next version of GXT, so this will no longer be necessary. Sorry for the confusion in my first post, I am not generally in the habit of checking user names across various posts, but I will be now...
Hello Colin,
Thank you for taking the time and reply on my issue. I appreciate it.
Until now I've tried to extend BeanModelGenerator with a custom generator that generates an implementation of BeanModelLookupImpl. This BeanModelLookupImpl would test the super-interface of the given class to getFactory. If it finds that class implements an interface extended from BeanModelTag then it would return an appropriate factory.
This was my strategy and it seemed sound from the start, but unfortunatelly I've learned that GWT doesn't have a Class.getInterfaces() method implemented yet. So it's not possible to implement my idea.
As of this moment, the implemented interfaces of a given GWT class can only be found out inside a Generator while at code generation stage. Since the BeanModelLookupImpl itself and the proxy implementations are generated by a generator, it is not possible to get the class parameter given to BeanModelLookupImpl.getFactory(Class clazz) and provide it to the generator. Nor it is possible to get all implementing generated classes of the proxy interface inside the generator because they're generated and don't exist statically(i.e. they're not included in the TypeOracle).
Your idea sounds like a good way to go if the client would know that all beans returned are of the same type. But in a tree-like structure it is possible that you could have something like:
* Folder [1]
** Melody
** Folder
*** Melody
so that the tree consists of multiple types of beans. If you expand the [1] folder, the list returned from server would contain different types. These would be returned as: {AutoBean_MelodyProxy, AutoBean_FolderProxy}. The issue here is that the client can't know which interface AutoBean_MelodyProxy implements, hence I don't know how to provide a factory like you said for this case. Since these classes are automatically generated by GWT's RequestFactory generator, I can't create a map like {AutoBean_MelodyProxy->MelodyProxy, AutoBean_FolderProxy->FolderProxy} and pass it to TreeBeanModelReader. One way perhaps to do this would be to have my server beans encode for each bean a property that specifies the name of the Proxy(i.e. getProxyName() -> FolderProxy). I'm not sure if you considered this case but if you did, I hope you could provide me with a bit more insight.
Since I'm not a premium user yet, could you give me a rough estimate when the next GXT version will come out with RequestFactory and AutoBean support?
Thank you!
Giving it a another thought, I don't know if it makes sense to go down this "reinvent the wheel" road.
I've talked with @Stigrv in this thread and while he said he upgraded to RequestFactory I don't have a clear understanding of how much work is involved.
Even if I'd fix the above thing, I'd still have to modify the BaseLoader which uses this reader into something that works with RequestFactory. Now, BaseLoader uses the DataProxy interface which uses AsyncCallback that is RPC specific.
If you could help me with this I'd appreciate it very much.
Thank you!
I'm going to try to reply to a lot of things here, not just your last reply, because there are lots of options available.
It gets a little deeper than this - BeanModelFactory.newInstance() is supposed to be able to construct new instances of the types it manages, which is clearly not possible out of the box when wrapping interfaces that will be implemented at runtime. Truly, this was intended for bean classes, and the new RF and AB stuff is a totally different mechanism.
Before moving on, I'd like to point out a solution that still uses the idea I gave before, and fits the use case you just mentioned. Instead of passing in a single factory to a general RF-ready treereader, make a specialized treereader that expects only your two types. Have it then verify that any given instance is a Folder or Melody subclass before selecting the proper factory for it. I can help with the code if you don't yet see what I mean.
If you are using the loader/proxy to get data, there shouldn't be issues with violations going off, so just have receiver.onSuccess call asyncCallback.onSuccess, and the same for onFailure, plus some exception unwrapping code if you like.
One final thought –
final MyRequestFactory rf = GWT.create(MyReqyestFactory.class);
rf.startMyRequest().loadSomeData().fire(new Receiver(){
public void onSuccess(MyDataModel model) {
EntityProxyId<MyDataModel> id = model.stableId();
//what does this return:
id.getProxyClass();
}
});
If, as I suspect, this returns the interface that the EntityProxyImpl was created to wrap, you can pass that to getFactory(Class), and always get the correct factory. I make this assumption because:
AbstractRequestContext (the superclass to any MyRequest interface) has create(Class), which calls
IdFactory.allocateId (IDFactory is a superclass of AbstractRequestFactory), which calls
IdFactory.createId(Class, int), which calls
new SimpleProxyId(Class, int), which sets the SimpleProxyId's proxyClass field to that class object.
This may only apply for creating new instances, but that would surprise me, as you can turn strings into instances with a little extra type info. Further, you can get history tokens from RF that refer to the proxy interface.
Good luck! From the SenchaCon 2010 slides, GXT 3 is expected this summer, but that is all I know for certain.
Thank you! You wrote a very comprehensive reply.
I'll try to understand all you said, and I'll come with feedback later if anything's unclear.
I appreciate it very much! Have a great day!
Stop by #extgwt on irc.freenode.net if you want to chat.
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#include <inttypes.h>
#include "avcodec.h"
#include "mathops.h"
#include "lsp.h"
#include "libavcodec/mips/lsp_mips.h"
#include "libavutil/avassert.h"
Go to the source code of this file.
Interpolate LSP for the first subframe and convert LSP -> LP for both subframes (3.2.5 and 3.2.6 of G.729).
Definition at line 171 of file lsp.c.
Referenced by decode_frame().
Convert LSF to LSP.
Definition at line 83 of file lsp.c.
Referenced by decode_frame().
Floating point version of ff_acelp_lsf2lsp().
Definition at line 93 of file lsp.c.
Referenced by amrwb_decode_frame(), hb_synthesis(), lsf2lsp_3(), and lsf2lsp_for_mode12k2().
LSP to LP conversion (3.2.6 of G.729).
Definition at line 123 of file lsp.c.
Referenced by ff_acelp_lp_decode().
Reconstruct LPC coefficients from the line spectral pair frequencies.
Definition at line 209 33 of file lsp.c.
Referenced by lsf_decode().
LSP to LP conversion (5.2.4 of AMR-WB).
Definition at line 145 of file lsp.c.
Referenced by amrwb_decode_frame(), hb_synthesis(), and sipr_decode_lp().
Definition at line 73 of file lsp.c.
Referenced by ff_acelp_lsf2lsp().
Compute the Pa / (1 + z(-1)) or Qa / (1 - z(-1)) coefficients needed for LSP to LPC conversion.
We only need to calculate the 6 first elements of the polynomial.
Definition at line 191 of file lsp.c.
Referenced by ff_acelp_lspd2lpc(), and ff_amrwb_lsp2lpc(). 51 of file lsp.c.
Referenced by amrwb_decode_frame(), ff_sipr_decode_frame_16k(), lsf2lsp_3(), lsf2lsp_for_mode12k2(), and lsf_decode_fp().
Sort values in ascending order.
Definition at line 228 of file lsp.c.
Referenced by decode_lsp(), and lsf_decode_fp().
decodes polynomial coefficients from LSP
Definition at line 106 of file lsp.c.
Referenced by ff_acelp_lsp2lpc().
Initial value:
{, }
Definition at line 61 of file lsp.c. | http://ffmpeg.org/doxygen/1.0/lsp_8c.html | CC-MAIN-2016-26 | refinedweb | 275 | 57.23 |
Drawing geometry with CCDrawNode
CCDrawNode provides methods for drawing primitive objects such as lines, circles, and triangles.
The
CCDrawNode class in CocosSharp provides multiple methods for drawing common geometric shapes. It inherits from the
CCNode class, and is usually added to
CCLayer instances. This guide covers how to use
CCDrawNode instances to perform custom rendering. It also provides a comprehensive list of available draw functions with screen shots and code examples.
Creating a CCDrawNode
The
CCDrawNode class can be used to draw geometric objects such as circles, rectangles, and lines. For example, the following code sample shows how to create a
CCDrawNode instance which draws a circle in a
CCLayer implementing class:
public class GameLayer : CCLayer { public GameLayer () { var drawNode = new CCDrawNode (); this.AddChild (drawNode); // Origin is bottom-left of the screen. This moves // the drawNode 100 pixels to the right and 100 pixels up drawNode.PositionX = 100; drawNode.PositionY = 100; drawNode.DrawCircle ( center: new CCPoint (0, 0), radius: 20, color: CCColor4B.White); } }
This code produces the following circle at runtime:
Draw method details
Let’s take a look at a few details related to drawing with a
CCDrawNode:
Draw methods positions are relative to the CCDrawNode
All draw methods require at least one position value for drawing. This position value is relative to the
CCDrawNode instance. This means that the
CCDrawNode itself has a position, and all draw calls made on the
CCDrawNode also take one or more position values. To help understand how these values combine, let’s look at a few examples.
First we’ll look at the
DrawCircle example above:
... drawNode.PositionX = 100; drawNode.PositionY = 100; drawNode.DrawCircle (center: new CCPoint (0, 0), ...
In this case, the
CCDrawNode is positioned at (100,100), and the drawn circle is at (0,0) relative to the
CCDrawNode, resulting in the circle being centered 100 pixels up and to the right of the bottom-left corner of the game screen.
The
CCDrawNode can also be positioned at the origin (bottom left of the screen), relying on the circle for offsets:
... drawNode.PositionX = 0; drawNode.PositionY = 0; drawNode.DrawCircle (center: new CCPoint (50, 60), ...
The code above results in the circle’s center at 50 units (
drawNode.PositionX + the
CCPoint.X) to the right of the left side of the screen, and 60 (
drawNode.PositionY + the
CCPoint.Y) units above the bottom of the screen.
Once a draw method has been called, the drawn object cannot be modified unless the
CCDrawNode.Clear method is called, so any repositioning needs to be done on the
CCDrawNode itself.
Objects drawn by
CCNodes are also impacted by the
CCNode instance’s
Rotation and
Scale properties.
Draw methods do not need to be called every frame
Draw methods need to be called only once to create a persistent visual. In the example above, the call to
DrawCircle in the constructor of the
GameLayer –
DrawCircle does not need to be called every-frame to re-draw the circle when the screen refreshes.
This differs from draw methods in MonoGame, which typically will render something to the screen for only one frame, and which must be called every-frame.
If draw methods are called every frame then objects will eventually accumulate inside the calling
CCDrawNode instance, resulting in a drop in framerate as more objects are drawn.
Each CCDrawNode supports multiple draw calls
CCDrawNode instances can be used to draw multiple shapes. This allows complex visual objects to be encased in a single object. For example, the following code can be used to render multiple circles with one
CCDrawNode:
for (int i = 0; i < 8; i++) { drawNode.DrawCircle ( center: new CCPoint (i*15, 0), radius: 20, color: CCColor4B.White); }
This results in the following graphic:
Draw call examples
The following draw calls are available in
CCDrawNode:
DrawCatmullRom
DrawCircle
DrawCubicBezier
DrawEllipse
DrawLineList
DrawPolygon
DrawQuadBezier
DrawRect
DrawSegment
DrawSolidArc
DrawSolidCircle
DrawTriangleList
DrawCardinalSpline
DrawCardinalSpline creates a curved line through a variable number of points.
The
config parameter defines which points the spline will pass through. The example below shows a spline which passes through four points.
The
tension parameter controls how sharp or round the points on the spline appear. A
tension value of 0 will result in a curved spline, and a
tension value of 1 will result in a spline drawn by straight lines and hard edges.
Although splines are curved lines, CocosSharp draws splines with straight lines. The
segments parameter controls how many segments to use to draw the spline. A larger number results in a smoothly curved spline at the cost of performance.
Code example:
var splinePoints = new List<CCPoint> (); splinePoints.Add (new CCPoint (0, 0)); splinePoints.Add (new CCPoint (50, 70)); splinePoints.Add (new CCPoint (0, 140)); splinePoints.Add (new CCPoint (100, 210)); drawNode.DrawCardinalSpline ( config: splinePoints, tension: 0, segments: 64, color:CCColor4B.Red);
DrawCatmullRom
DrawCatmullRom creates a curved line through a variable number of points, similar to
DrawCardinalLine. This method does not include a tension parameter.
Code example:
var splinePoints = new List<CCPoint> (); splinePoints.Add (new CCPoint (0, 0)); splinePoints.Add (new CCPoint (80, 90)); splinePoints.Add (new CCPoint (100, 0)); splinePoints.Add (new CCPoint (0, 130)); drawNode.DrawCatmullRom ( points: splinePoints, segments: 64);
DrawCircle
DrawCircle creates a perimeter of a circle of a given
radius.
Code example:
drawNode.DrawCircle ( center:new CCPoint (0, 0), radius:20, color:CCColor4B.Yellow);
DrawCubicBezier
DrawCubicBezier draws a curved line between two points, using control points to set the path between the two points.
Code example:
drawNode.DrawCubicBezier ( origin: new CCPoint (0, 0), control1: new CCPoint (50, 150), control2: new CCPoint (250, 150), destination: new CCPoint (170, 0), segments: 64, lineWidth: 1, color: CCColor4B.Green);
DrawEllipse
DrawEllipse creates the outline of an ellipse, which is often referred to as an oval (although the two are not geometrically identical). The shape of the ellipse can be defined by a
CCRect instance.
Code example:
drawNode.DrawEllipse ( rect: new CCRect (0, 0, 130, 90), lineWidth: 2, color: CCColor4B.Gray);
DrawLine
DrawLine connects to points with a line of a given width. This method is similar to
DrawSegment, except it creates flat endpoints as opposed to round endpoints.
Code example:
drawNode.DrawLine ( from: new CCPoint (0, 0), to: new CCPoint (150, 30), lineWidth: 5, color:CCColor4B.Orange);
DrawLineList
DrawLineList creates multiple lines by connecting each pair of points specified by a
CCV3F_C4B array. The
CCV3F_C4B struct contains values for position and color. The
verts parameter should always contain an even number of points, as each line is defined by two points.
Code example:
CCV3F_C4B[] verts = new CCV3F_C4B[] { // First line: new CCV3F_C4B( new CCPoint(0,0), CCColor4B.White), new CCV3F_C4B( new CCPoint(30,60), CCColor4B.White), // second line, will blend from white to red: new CCV3F_C4B( new CCPoint(60,0), CCColor4B.White), new CCV3F_C4B( new CCPoint(120,120), CCColor4B.Red) }; drawNode.DrawLineList (verts);
DrawPolygon
DrawPolygon creates a filled-in polygon with an outline of variable width and color.
Code example:
CCPoint[] verts = new CCPoint[] { new CCPoint(0,0), new CCPoint(0, 100), new CCPoint(50, 150), new CCPoint(100, 100), new CCPoint(100, 0) }; drawNode.DrawPolygon (verts, count: verts.Length, fillColor: CCColor4B.White, borderWidth: 5, borderColor: CCColor4B.Red, closePolygon: true);
DrawQuadBezier
DrawQuadBezier connects two points with a line. It behaves similarly to
DrawCubicBezier but only supports a single control point.
Code example:
drawNode.DrawQuadBezier ( origin:new CCPoint (0, 0), control:new CCPoint (200, 0), destination:new CCPoint (0, 300), segments:64, lineWidth:1, color:CCColor4B.White);
DrawRect
DrawRect creates a filled-in rectangle with an outline of variable width and color.
Code example:
var shape = new CCRect ( 0, 0, 100, 200); drawNode.DrawRect(shape, fillColor:CCColor4B.Blue, borderWidth: 4, borderColor:CCColor4B.White);
DrawSegment
DrawSegment connects two points with a line of variable width and color. It is similar to
DrawLine, except it creates round endpoints rather than flat endpoints.
Code example:
drawNode.DrawSegment (from: new CCPoint (0, 0), to: new CCPoint (100, 200), radius: 5, color:new CCColor4F(1,1,1,1));
DrawSolidArc
DrawSolidArc creates a filled-in wedge of a given color and radius.
Code example:
drawNode.DrawSolidArc( pos:new CCPoint(100, 100), radius:200, startAngle:0, sweepAngle:CCMathHelper.Pi/2, // this is in radians, clockwise color:CCColor4B.White);
DrawSolidCircle
DrawCircle creates a filled-in circle of a given radius.
Code example:
drawNode.DrawSolidCircle( pos: new CCPoint (100, 100), radius: 50, color: CCColor4B.Yellow);
DrawTriangleList
DrawTriangleList creates a list of triangles. Each triangle is defined by three
CCV3F_C4B instances in an array. The number of vertices in the array passed to the
verts parameter must be a multiple of three. Note that the only information contained in
CCV3F_C4B is the position of the verts and their color – the
DrawTriangleList method does not support drawing triangles with textures.
Code example:
CCV3F_C4B[] verts = new CCV3F_C4B[] { // First triangle: new CCV3F_C4B( new CCPoint(0,0), CCColor4B.White), new CCV3F_C4B( new CCPoint(30,60), CCColor4B.White), new CCV3F_C4B( new CCPoint(60,0), CCColor4B.White), // second triangle, each point has different colors: new CCV3F_C4B( new CCPoint(90,0), CCColor4B.Yellow), new CCV3F_C4B( new CCPoint(120,60), CCColor4B.Red), new CCV3F_C4B( new CCPoint(150,0), CCColor4B.Blue) }; drawNode.DrawTriangleList (verts);
Summary
This guide explains how to create a
CCDrawNode and perform primitive-based rendering. It provides an example of each of the draw calls. | https://docs.microsoft.com/en-us/xamarin/graphics-games/cocossharp/ccdrawnode | CC-MAIN-2018-34 | refinedweb | 1,534 | 50.94 |
Number of downloads: 1868
In this tutorial series I will walk you through the process of creating an Asteroids clone. It will take quite a few tutorials. I'm assuming for these tutorials that you have a good grip on C# and a basic understanding of how the XNA Framework works. I'm not going to be explaining things like what a method is or what a variable is. I will be using Visual C# 2008 Express Edition. I don't have an XBOX controller so I won't be able to add t
So, let's get started. Create a new Windows Game project, I called mine AsteroidsClone. If you copy and paste the code for these tutorials you will have to make sure you are in the right namespace. To this project you will want to add a new class and call it Sprite. This is the code for the Sprite class:
using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework; namespace AsteroidsClone { class Sprite { Texture2D texture; Vector2 position; Vector2 center; Vector2 velocity; float rotation; float scale; bool alive; int index; public Sprite(Texture2D texture) { this.texture = texture; position = Vector2.Zero; center = new Vector2(texture.Width / 2, texture.Height / 2); velocity = Vector2.Zero; Rotation = 0.0f; Scale = 1.0f; alive = false; index = 0; } public Texture2D Texture { get { return texture; } } public Vector2 Position { get { return position; } set { position = value; } } public Vector2 Center { get { return center; } } public Vector2 Velocity { get { return velocity; } set { velocity = value; } } public float Rotation { get { return rotation; } set { rotation = value; if (rotation < -MathHelper.TwoPi) rotation = MathHelper.TwoPi; if (rotation > MathHelper.TwoPi) rotation = -MathHelper.TwoPi; } } public float Scale { get { return scale; } set { scale = value; } } public bool Alive { get { return alive; } } public int Index { get { return index; } set { index = value; } } public void Create() { alive = true; } public void Kill() { alive = false; } } }
You will notice that all of the variables in the class are private and I've written properties to access them. I did this because eventually you may want to add validation so that improper values can't be set in the variables. You will also notice that you had to add two using statements to the class. One for the XNA Framework and one for the Graphics.
The constructor for the class takes one parameter, the texture of the sprite. It sets most of the other fields to zero, except for center which is set to the center of the texture and how the sprite should be scaled, which is set to 1.0f.
Most of the properties are get and set. I made the Center, Texture and Alive properties as get only as the center and texture of the sprite shouldn't change. I could have made Alive get and set but I decided to write two methods Create and Kill. One other thing I did is with the Rotation property. I made it so that the degree of the rotation, in radians, is between Pi * 2 and -Pi * 2. This isn't really a necessary step but since the trigonometric functions used are cyclical there is no need to exceed these values.
Before you can continue you will have to add some assets to the project. I will be attaching the sprites that I will be using for this project to this tutorial. Just remember, I will never claim to be a graphics artisit.
Once you have the sprites, create a new folder in the Content folder and call it Sprites. Then right click the Sprites folder and select Existing Item.... Find where you unzipped the sprites and select them all.
In this step I will help you write the code to draw the ship, rotate it and fire bullets. I will cover moving the ship in another tutorial.
This is the code for the the Game1.cs AsteroidsClone { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; SpriteBatch spriteBatch; Sprite ship; int ScreenWidth, ScreenHeight; KeyboardState oldState; Sprite bullet; List<Sprite> bullets = new List<Sprite>(); public Game1() { graphics = new GraphicsDeviceManager(this); Content.Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.Black); spriteBatch.Begin(SpriteBlendMode.AlphaBlend); spriteBatch.Draw(ship.Texture, ship.Position, null, Color.White, ship.Rotation, ship.Center, ship.Scale, SpriteEffects.None, 1.0f); foreach (Sprite b in bullets) { if (b.Alive) { spriteBatch.Draw(b.Texture, b.Position, null, Color.White, b.Rotation, b.Center, b.Scale, SpriteEffects.None, 1.0f); } } spriteBatch.End(); base.Draw(gameTime); } } }
Now, I will explain the code. First I created six variables. A variable for the ship, variables to hold the ScreenWidth and ScreenHeight, a variable to hold the old state of the keyboard, a variable to hold the bullet information and a list of bullets. I made a variable to hold the keyboard state because when the player presses and releases the space bar I want a bullet to be shot, I don't want an autofire game.
In the constructor of Game1 I set the height and width of the window. I thought 500 x 500 was a good size. The field should be square, but it doesn't have to be. You can change these to whatever you like.
In the Initialize method I made a call to a method called SetupGame that will be written next. The SetupGame method sets the ScreenWidth and ScreenHeight variables and calls the method SetupShip to set the ship in the start position and make the ship to be alive.
The next method is the LoadContent method. This is where you load the content for your project. Right now all you need for now are the ship and the bullet.
Now is when things start to get interesting. There are two methods in XNA, the Update and the Draw method. The Update method is where you perform the logic of the game. The Draw method is where you render your scene.
I will tackle the Update method first. XNA creates some code for you in the Update method to give a way for the game to end using a XBOX controller. After that is where I added the logic to rotate the ship and fire off a bullet. I also added a feature that will end the game if the player presses Escape. The code for rotating the ship is simple. If you are holding down the Left key the rotation of the ship is decreased and the other way around for the Right key.
To tell if the Spacebar has been pressed I did things a little different than the way it is usually done. Usually you check to see if the current state of the key/controller button is down and the last state of key/controller button is up. I like to do it the other way around. You don't have to for a simple game like this but when you get to doing more advanced things it does help. If the Spacebar has been pressed and released I call a method to fire a bullet called FireBullet. Then I store the current state of the keyboard and call a method to update the bullets, UpdateBullets.
The FireBullet method does something interesting. First, a creates a new bullet that will be added to the list of bullets. Finding the position and velocity if the bullet takes a little bit of calculations. Velocity is a little harder than position. To get the direction of the bullet is travelling is a little complicated. You need to find the cosine of the ship's rotation and the sine of the ships rotation. The way I set up the game, you have to subtract Pi/2 from the rotation angle. If you don't the bullet will shoot 90 degrees to the right.
The position of the bullet took a little figuring out. If you just use the position of the ship, it will start in the middle of the ship. I tried just adding the velocity of the bullet to the ship's position. It still started inside the ship. So I messed around with different multipliers and found one that I liked,
1.75f. After finding the position of the bullet I create the bullet and add it to the list of bullets.
The code in the UpdateBullets method is a little interesting. I used a foreach and a for loop in this method. The foreach loop goes through all of the bullets in the list of bullets. It adds the velocity of the bullet to the bullet's position. If the bullet has travelled outside of the boundries of the screen it kills the bullet.
The for loop goes through the list. If it finds a dead bullet it removes it from the list of bullets. When going through a list and removing items from the list inside a for loop if you remove an item from the list, you need to decrease the counter by 1, otherwise you will get an exception.
Now that the ship and bullets are created and updating it is time to draw the ship and the bullets. To draw a 2D object you use a SpriteBatch object. When you are drawing sprites, you do it inside a Begin and End method call of the SpriteBatch object. In the Begin method call I used SpriteBlendMode.AlphaBlend because there are transparent parts of the images. The overload of the Draw method I used has nine parameters. I will explain them. The first one is the texture that is being drawn. Next there is the position you want to draw the texture. The third is the source rectangle you want to use. If you have all of your images in one bitmap you would use the source rectangle to find where the texture is in the image. I used seperate images so I just set it to null to say I don't want to use one. The next is the tint color that you want to use. If you don't want to tint the texture just set it to Color.White. Next is the angle of rotation you want to use, in radians. After rotation comes origin. You can choose different points to rotate your texture around with different effects. I chose the center of the texture. Next is the scale you want to use to draw the texture. Then is the SpriteEffects that you want to use, in this case SpriteEffects.None. Finally there is the layer depth you want to draw at. In this game it is not important so just set it to 1.0f all the time.
I think that is more than enough for one tutorial. I will try and have the next part up soon which will be adding asteroids to the game. | http://www.dreamincode.net/forums/topic/100575-xna-30-game-tutorial-part-1/ | CC-MAIN-2017-34 | refinedweb | 1,816 | 74.79 |
SYNOPSIS
#include <sys/msg.h>
int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);
DESCRIPTION
The msgsnd() function operates on XSI message queues (see the Base Def-
initions argu-
ment exe-
cution until one of the following occurs:
* The condition responsible for the suspension no longer exists, in
which case the message is sent.
* msg_lspid shall be set equal to the process ID of the calling
process.
* msg_stime shall be set equal to the current time.
RETURN VALUE
Upon successful completion, msgsnd() shall return 0; otherwise, no mes-
sage shall be sent, msgsnd() shall return -1, and errno shall be set to
indicate the error.
ERRORS.
The following sections are informative.
EXAMPLES);
SEE ALSO . | http://www.linux-directory.com/man3/msgsnd.shtml | crawl-003 | refinedweb | 116 | 55.13 |
A water pulse meter using interrupts and the ATMEGA328P "power save" mode
Hello everyone!
I'm back here with an exciting project and an exciting issue
, after my post regarding the "pilot wire" (which works well by the way)!
First, a bit of context, as usual:
My new goal is know how much water is consumed in the house, still via HomeAssistant. The specifications I imposed to myself:
- The node will be powered on batteries. It should consume the minimum amount of power and therefore sleep as much as possible.
- I would like to send the amount of water consumed "reliably" every 5 minutes to avoid spamming the gateway and to save energy. And 5 minutes, no more (>= 5'01"), no less (<= 4'59").
Similarly to my previous project, I am not using any Arduino board. Only an ATMEGA328P using its own internal 8MHz clock.
To measure the amount of water I am using, I chose to buy a second-hand two-wires "Itron Cyble sensor", where "K=1". It is a very basic sensor which outputs a "signal equivalent to a dry contact signal (e.g. reed switch)".
More information about it can be found in its brochure:
Considerations:
To consume as less energy as possible, the circuit must be interrupt-driven. I can see two interrupts here:
On the water sensor side: whenever the sensor simulates a pushed button (meaning I've consumed a liter of water), this has to increment a variable. Once done, the chip should go back to sleep.
To measure 5 minutes: I've spent quite a bit of time searching for solutions to reliably measure 5 minutes, without using external components (an RTC for instance).
It seems I wasn't the only one to wonder how to have interrupts and a timer and I found this post for instance:. However, I didn't like the solution given, which didn't look elegant to me...
Moreover, the
sleep()function provided by the MySensors API wakes the radio up after sleeping and I don't need waking it up when I simply have to increment the "water consumed" variable!
And then, I discovered that the ATMEGA328P can run an asynchronous timer (called Timer2) and trigger interrupts on overflows / compare matches. But the really nice thing here is that this timer continues running in the power saving mode "SLEEP_MODE_PWR_SAVE", if a 32.768 kHz quartz is connected!
Where I am right now:
Right now, I have finished wiring the circuit on a breadboard and developing the code. Regarding the wiring, I have:
- An ATMEGA328P flashed with my code (with encryption enabled) and using its internal 8 MHz clock to operate.
- An RFM69W radio connected to the chip.
- A button connected to the arduino-equivalent pin #3 (pin 2 is used by the RFM69W radio, DI0), to simulate my Itron sensor.
- A 32.768 kHz quartz connected on the XTAL pins of the ATMEGA.
- A few other capacitors here and there, where they are needed.
Now, here is the code of my sketch:
// MySensors configuration #define MY_RADIO_RFM69 #define MY_RFM69_NEW_DRIVER #define MY_RFM69_ENABLE_ENCRYPTION // Include the libraries #include <avr/power.h> #include <avr/sleep.h> #include <MySensors.h> // Global settings #define CHILD_ID 0 // Global variables volatile bool time_elapsed = true; volatile int liters_consumed = 0; MyMessage measure_msg(CHILD_ID, V_VOLUME); // Interrupt triggered on Timer2 overflow ISR(TIMER2_COMPA_vect){ // variable to count the number of overflows static byte timer2_ovfs = 0; // Increment the counter timer2_ovfs++; // Set the flag and reset the counter if (timer2_ovfs >= 40) { time_elapsed = true; timer2_ovfs = 0; } } void sensor_interrupt() { liters_consumed++; } void presentation() { sendSketchInfo("Compteur d'eau", "1.0"); present(CHILD_ID, S_WATER); } void setup() { // Setup Timer2 ASSR = (1<<AS2); // Make Timer2 asynchronous TCCR2A = (1<<WGM21); // CTC mode TCCR2B = (1<<CS22)|(1<<CS21)|(1<<CS20); // Prescaler of 1024 OCR2A = 239; // Count up to 240 (zero relative!) TIMSK2 = (1<<OCIE2A); // Enable compare match interrupt // Setup interrupt on pin (INT1) pinMode(3, INPUT); attachInterrupt(digitalPinToInterrupt(3), sensor_interrupt, RISING); // Disable unneeded peripherals power_adc_disable(); // Analog to digital converter power_twi_disable(); // I2C // Set the sleep mode as "Power Save" set_sleep_mode(SLEEP_MODE_PWR_SAVE); // Enable interrupts interrupts(); } void loop() { // The 5 minutes period has passed if(time_elapsed) { // Wake up the radio transportReInitialise(); // Send the value send(measure_msg.set(liters_consumed)); // Reset the timer time_elapsed = false; // Make the radio sleep transportDisable(); } // Go back to sleep sleep_mode(); }
The problem:
However, there is a problem right now (otherwise, I wouldn't post in the "troubleshooting" section
).
On the gateway side, I can see that the node successfully registers and gets its ID. But for an unknown reason, after a few seconds, it keeps sending data as if
time_elapsednever changed to
false. And it never goes to sleep.
Here are the gateway logs after startup:
Aug 18 17:01:05 INFO Starting gateway... Aug 18 17:01:05 INFO Protocol version - 2.3.1 Aug 18 17:01:05 DEBUG Serial port /dev/ttyMySensorsGateway (115200 baud) created Aug 18 17:01:05 DEBUG MCO:BGN:INIT GW,CP=RPNGLS-X,REL=255,VER=2.3.1 Aug 18 17:01:05 DEBUG TSF:LRT:OK Aug 18 17:01:05 DEBUG TSM:INIT Aug 18 17:01:05 DEBUG TSF:WUR:MS=0 Aug 18 17:01:05 DEBUG TSM:INIT:TSP OK Aug 18 17:01:05 DEBUG TSM:INIT:GW MODE Aug 18 17:01:05 DEBUG TSM:READY:ID=0,PAR=0,DIS=0 Aug 18 17:01:05 DEBUG MCO:REG:NOT NEEDED Aug 18 17:01:05 DEBUG MCO:BGN:STP Aug 18 17:01:05 DEBUG MCO:BGN:INIT OK,TSP=1 Aug 18 17:01:05 DEBUG TSM:READY:NWD REQ Aug 18 17:01:05 DEBUG TSF:MSG:SEND,0-0-255-255,s=255,c=3,t=20,pt=0,l=0,sg=0,ft=0,st=OK: Aug 18 17:01:06 DEBUG TSF:MSG:READ,2-2-0,s=255,c=3,t=21,pt=1,l=1,sg=1:0 Aug 18 17:01:15 DEBUG TSF:MSG:READ,3-3-255,s=255,c=3,t=7,pt=0,l=0,sg=0: Aug 18 17:01:15 DEBUG TSF:MSG:BC Aug 18 17:01:15 DEBUG TSF:MSG:FPAR REQ,ID=3 Aug 18 17:01:15 DEBUG TSF:PNG:SEND,TO=0 Aug 18 17:01:15 DEBUG TSF:CKU:OK Aug 18 17:01:15 DEBUG TSF:MSG:GWL OK Aug 18 17:01:16 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=8,pt=1,l=1,sg=0,ft=0,st=OK:0 Aug 18 17:01:17 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=24,pt=1,l=1,sg=0:1 Aug 18 17:01:17 DEBUG TSF:MSG:PINGED,ID=3,HP=1 Aug 18 17:01:17 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=25,pt=1,l=1,sg=0,ft=0,st=OK:1 Aug 18 17:01:17 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=15,pt=6,l=2,sg=0:0100 Aug 18 17:01:18 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=15,pt=6,l=2,sg=0,ft=0,st=OK:0100 Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=0,t=17,pt=0,l=5,sg=0:2.3.1 Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=6,pt=1,l=1,sg=0:0 Aug 18 17:01:18 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=6,pt=0,l=1,sg=0,ft=0,st=OK:M Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=11,pt=0,l=14,sg=0:Compteur d'eau Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=12,pt=0,l=3,sg=0:1.0 Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=0,c=0,t=21,pt=0,l=0,sg=0: Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=255,c=3,t=26,pt=1,l=1,sg=0:2 Aug 18 17:01:18 DEBUG TSF:MSG:SEND,0-0-3-3,s=255,c=3,t=27,pt=1,l=1,sg=0,ft=0,st=OK:1 Aug 18 17:01:18 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:34 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:36 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:37 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:38 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:39 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:41 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:42 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:43 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:0 Aug 18 17:01:44 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:1 Aug 18 17:01:46 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:3 Aug 18 17:01:47 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:7 Aug 18 17:01:48 DEBUG TSF:MSG:READ,3-3-0,s=0,c=1,t=35,pt=2,l=2,sg=0:7
As you can see, a few seconds after registering, the node spams the gateway, sending the
liters_consumedvariable every second.
Do you guys know why? What can be wrong in this code?
Also, does the MySensor library generate other kind of interrupts?
Thanks in advance for your help!
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Appendix / bonus: how I get the 5 minutes period.
As mentioned, a 32.768 kHz quartz generates 32,768 clock cycles per second.
The clock prescaler has been set to 1024, meaning that I need 1024 clock cycles to add "1" to Timer2. This means that each second, 32 is added to timer2.
The "output compare register A" was set to 239, meaning that it will trigger an "Output Compare A interrupt" every time the counter reaches 239 (starting from 0 in CTC mode). So, such an interrupt will be triggered every 240 / 32 = 7.5s, waking up the microcontroller from sleep mode and adding 1 to the timer2_ovfs variable.
Finally, when I reach 40 output compare interrupts, I'm (supposed) to send the data to the controller. Since 7.5s * 40 = 300s = 5 minutes!
If you are using watch crystal (32khz) connected to TOSC1/2, I have an "rtc" one second tick counter you can use (from an unrelated project):
You can extend this to different tick periods with different prescalers.
But i think any interrupt will bring mysensors out of wait? Which means you will need to enter sleep yourself, and decide whether to go back to sleep or hand control back to main loop for mysensors to do reporting thing.
Here are some examples i put together for directly controlling entering/exiting low-power sleep:
You can also use watchdog timer as (less accurate) wakeup timer.
(But you said you need more exact, <1 sec, accuracy to send at [exactly] 5 sec boundaries, which means you'll need timer2/rtc/watch crystal for that level of accuracy)
You can use a separate counter, e.g. timer1 in counter mode to capture sensor pulses as an external clock for the counter. You probably only need interrupt on counter overflow, so you can capture overflow counts. Then when you wake up on an interval and check the number of pulses you can evaluate overflows + remaining counter value, and determine number of pulses since previous wakeup, etc. (without needing wakeup/cpu to keep track of individual pulses)
also, declaring static var inside isr is strange to me (maybe it works?) but I have always seen that you should declare any vars to be manipulated in isr to be
global andvolatile
Hello @Jens-Jensen!
Thanks for your answer, I'm asking a kind of tricky question here it seems!
Thanks for your link regarding the RTC project.
I actually more or less based my code on the Sparkfun's BigTime watch project () in which they handle interrupts the same way.
As I explained in my first post, I'm indeed generating a Timer2 compare interrupt every 7.5s, waking up the microcontroller, making it add 1 to the overflows count and then it is (supposed) to go back to sleep. But it doesn't, for some reason.
I may have found a clue regarding my problem, after spending more time Googling. There may be some kind of method to call before entering into the AVR sleep mode, to make the "MySensors state machine" aware of that.
Here is the link about the post I found:
@scalz may have an idea about my issue if he is around? He seems to have a very good knowledge about what's happening under the hood...
Cheers!
Also, regarding the static keyword in the ISR, it should be working fine.
I first played with the asynchronous mode of Timer2 before integrating MySensors, the code successfully toggled an LED every 5 minutes.
- zboblamont last edited by zboblamont
@encrypt K=1 means a pulse every litre, the Itron may be a fet type head rather than a reed..
No idea why you are doing this at the Node, the increased wakeups will reduce battery run-time IMHO... The 2xAA alkaline powered (pro-mini) water meter Node here is still at 2.8v after nearly 18 months, but that is on a boosted supply sucking the batteries to below 2v (ie dead). It is on a fet triggered Class D meter on the domestic supply, the updated value sent on every litre passing, the Controller does the rest, in this case Domoticz, no idea on HomeAssistant.
Admitedly this summates the readings into hourly volumetric consumptions, but there are other ways to sift the data (NodeRed?) if it is essential to have finer time based data.
@Encrypt
yes, interesting... i also had strange issues trying to implement rtc first time, but it was due to arduino lib mucking with Timer2 registers (due to Tone libs). The answer was to make sure all registers were not assumed to be default, but explicitly set in setup(). You seem to have that here.
I did a quick scan of mysensors repo code, but I don't see where it is touching any of Timer2's registers, so not sure.
Did you toggle led/pin in the current code's ISR, to be 100% sure your the issue is that the isr is getting triggered at unexpected interval? (maybe sanity check that with scope.) That should bifurcate the problem either to the timer implementation/configuration, or something else.
@zboblamont I also agree here. But it should be totally possible to setup Timer1 as externally clocked counter, i.e. pulse from meter can increment Timer1 counters without interrupting CPU from sleep, and only interrupt and increment another counter variable on Timer1 overflow (if it happens) so you can be sure you have complete, accurate count when you wake up from your long sleep to do your accounting and reporting..
Hello everyone!
@zboblamont: well, I guess that sending the number of liters consumed "in batch" should consume less energy, since it reduces the number of radio wake-ups and transmissions.
According to the datasheet:
- The ATMEGA328P "typically" consumes 5.2 mA in Active mode.
- The RFM69W consumes 45 mA (when RFOP = 13 dBm) when it transmits data
So I believed that doing so was a better option.
Also, the SparkFun documentations regarding the BigTime Watch Kit (which basically does what I am trying to do) states that: « Thanks to some low-level hackery, the ATMega is running at super low power and should get an estimated 2 years of run time on a single CR2032 coin cell! ».
@Jens-Jensen: I read somewhere that:
- Timer0 is used for functions like delay(), millis()...
- Timer1 is used for sound generation
- Timer2 isn't used by defaults in Arduino libraries
So if the MySensors library uses time somewhere, it probably uses Timer0. So it should be safe playing with Timer2
Regarding my tests, I toggled LEDs both in the ISR and in the loop() function.
I've had a closer look at how MySensors implements the sleep() function.
It seems that @tekka is the one that essentially worked on it according to the history of the code.
So, @tekka, if you're around, would you have an idea?
- Jens Jensen last edited by
So this is where I see for atmega 168/328, Tone lib is modding Timer2:
So that's why it's important to explicitly set every Timer2 register.
Reviewing AVR130 app note, I think I was incorrect about being able to sleep and externally clock T1 (to count pulses), as T0/T1 seem to be synchronous, meaning they require the system (i/o) clock to be running to latch in the edges of external source, and only IDLE power save mode supports running the clk_io. This mode will use way more current, e.g. w/ internal rc osc at 8MHz at 3.3v about 700uA.
Seems that only Timer2 can allow an "asynchronous" external clocking event (pulse counting) with cpu clocks off (in very low power modes).
Just blabbering, yet another aproach could be to, instead of bothering with RTC crystal on Timer2:
- use watchdog timer as a wakeup (interrupt only) source, for either an approximately 4 or 8 second interval (5 mins = 300 secs, 300 / 4 = 75 wakeups)
- use Timer2 as external event counter to count the pulses (without interrupt/wakeup?)
regarding the mysensors lib, I'm not an expert, but reviewing the code, seems like you covered it:
mysensors sleep overloads call _sleep in MySensorsCore.cpp
which call transportDisable() like you do then call hwSleep() variants in MyHwAVR.cpp (depending upon how you call sleep, e.g. with pin interrupt setups or not), which eventually call hwPowerDown()
which seems to do pretty much what you are doing (maybe a few other things, etc..) to call sleep. ref:
So I dont really see any additional state machine stuff happening w.r.t. MySensors itself.
- Jens Jensen last edited by
This post is deleted!
- zboblamont last edited by
@encrypt said in A water pulse meter using interrupts and the ATMEGA328P "power save" mode:
well, I guess that sending the number of liters consumed "in batch" should consume less energy, since it reduces the number of radio wake-ups and transmissions.
I thought similarly but practice demonstrates minimal if any measurable saving, ignoring the dual method wakeup you are examining. Have not looked into how the radio is handled (rfm69), but battery life is astonishing on the MySensors sleep (dominant condition).
eg - The gas node was initially set up to accumulate 5 pulses before updating the gateway, the water node does so every pulse.
There was no appreciable difference in battery decay over the winter months when both were running regularly, and the water node is over 92,000 notifications in on the same 2xAA, but this is a higher mAh than a CR2032.
- zboblamont last edited by zboblamont
@jens-jensen said in A water pulse meter using interrupts and the ATMEGA328P "power save" mode:.
The K value is an industry standard usually printed on gas and water meters for volume passing per pulse. eg - On my treated water Elster is stamped "K1" with a FET head, the outside raw water Zenner is "100L/imp" but not currently fitted with a reed, the gas meter has "1imp=0.01m3" with a reed. The gas meter threw me with interrupts until a continuity check revealed the reed was on for ca 6 seconds in full flow, therafter handled by a timer loop/sleep until it changed state, then going deep sleep.
I get the curiosity aspect over timers, simply not the reasons for using a specific form at the Node. As I understood it, Sleep and timing are in reality low energy loops of the CPU, the interrupt triggered by the sensor is what begins the higher energy process, hence maximum Sleep = long battery life.
Your Controller will usually expect a cumulative value (eg Domoticz), the only unforeseen I encountered was when the cumulative total incremented and overflowed giving Domoticz a brainfart. Changing the numeric type (long?) sent by the node rectified that, and is now well beyond the 65k..
@encrypt said in A water pulse meter using interrupts and the ATMEGA328P "power save" mode:
On the gateway side, I can see that the node successfully registers and gets its ID. But for an unknown reason, after a few seconds, it keeps sending data as if time_elapsed never changed to false. And it never goes to sleep.
Please be aware that sleeping on interrupts is rather tricky to get right!
When going to sleep, pending interrupts will immediately wake the AVR again. See the MySensors code from on.
In your case pending interrupts are very likely, as you use a mechanical button that hasn't been debounced.
Furthermore you are using MySensors internal functions that might work for now, but are not guaranteed to work in the future.
I would suggest to stick to the official API whenever possible.
MySensors development branch offers the ability to sleep for a fixed time and report remaining sleep time. Your node should just go back to sleep until 5 minutes have passed; see my post here:
Only drawback on AVR is the usage of the watchdog as a sleep timer, which makes it impossible to exactly get 5 minutes sleep interval.
- Alex Kubrinsky last edited by
I think mysensors sleep function is not suitable for this purpose.
Here is example from avr/sleep.h:
#include <avr/interrupt.h> #include <avr/sleep.h> ... set_sleep_mode(<mode>); cli(); if (some_condition) { sleep_enable(); sleep_bod_disable(); sei(); sleep_cpu(); sleep_disable(); } sei();
Hello everyone!
First of all, thank you for all your answers!
I've put in standby this project since I last replied here, however I wanted to give you an update about what I'm considering to do now.
As a few of you pointed out, I don't consume water "fast enough" to spam the MySensors gateway with messages and I don't consume a cubic meter of water per day either.
Moreover, I plan to solar-power this node with the AEM10941 chip from e-peas and a tiny solar cell.
Therefore, sending a message to the MySensors gateway and making the ATMEGA328P wake up only when it gets an interrupt from the itron water sensor (= 1L consumed) seems to be a good idea, at the end...
I'll probably do that and present my project in the '"Projects" section of the forum once it is done!
That being said, it seems I'm not the only one who would be interested in using the SLEEP_MODE_PWR_SAVE mode of the ATMEGA328P to keep Timer2 running. I guess it could be worth adding it to the library?
Cheers!
- zboblamont last edited by
@encrypt "making the ATMEGA328P wake up only when it gets an interrupt from the itron water sensor (= 1L consumed) seems to be a good idea" works for me for two meters and two timer activated ultrasonics.
Once you have that interrupt working reliably, only then I'd consider looking at power options. My Elster water meter (similar Itron) is now into year 3 on two AA alkalines, it makes no sense financially to consider solar, but as an experiment, sure, good luck...
Thanks for the feedback @zboblamont!
I was probably overthinking the whole thing | https://forum.mysensors.org/topic/10598/a-water-pulse-meter-using-interrupts-and-the-atmega328p-power-save-mode/17 | CC-MAIN-2020-16 | refinedweb | 4,124 | 59.84 |
The stack trace of an exception in a log file is a sign that something went wrong. Even if nobody complains it is wise to take a bit time and investigate it before it really hurts.
Exactly the same applies to JavaScript errors in a web application. I believe that each JavaScript error should be considered as a bug and they should all be fixed before delivering, no matter if they directly impact the user experience or not.
Many great tools (JavaScript Console, Firebug, WebDeveloper Toolbar, …) allow to see the JavaScript errors while developing with Firefox as well as with other browsers and a wisely used error handler can report JavaScript errors to the server in production.
Sadly the support is not good while running automated tests. HtmlUnit provides a great help for that (see for instance this) but often integration tests should run in “real” browsers and not in HtmlUnit (for some good and many bad reasons). I don’t know currently any browser automation tool providing access to the JavaScript errors and to other information available in browsers like Firefox or Chrome that can be helpful for developers conscientious of the quality of their work
WebDriver is here not better than its concurrents and the issue “API for checking for JavaScript errors on the page” is opened since 2 1/2 years without any sign of life from the project’s members. The Selenium 1 issues SEL-522 and SEL-613 are equally asleep. Luckily WebDriver provides the possibility to configure additional extensions when using the FirefoxDriver, what allows to improve the situation.
Tester’s friendly application and injected error handler
The simpliest way to catch JavaScript errors for later retrieval is to add something like that
<script type="text/javascript"> window.jsErrors = []; window.onerror = function(errorMessage) { window.jsErrors[window.jsErrors.length] = errorMessage; } </script>
in every page of your application (see for instance this post).
This allows you to retrieve the captured errors with
((JavascriptExecutor) driver).executeScript("return window.jsErrors");
This is a simple solution but it has different drawbacks. First you need to add this code at the beginning of all your HTML pages. If you’re in the ideal situation to be both developer and tester of the application it’s “just” one Ctrl+C and a lot of Ctrl+V. If you need to convince your colleagues or your management that the web pages should be modified for testability, it will be more difficult. From my experience it is not always easy to make such a requirement accepted.
To overcome this problem we could imagine injecting the handler while running the test:
String script = "window.collectedErrors = [];" + "window.onerror = function(errorMessage) { " + "window.collectedErrors[window.collectedErrors.length] = errorMessage;" + "}"; ((JavascriptExecutor) driver).executeScript(script);
but besides the fact that it has to be done on every page, we can’t do it early enough: a lot of JavaScript may already have been executed in the page when our
executeScript statement is reached.
The second problem of an error handler per window is the difficult access to the captured errors. The JavaScript errors won’t necessarily occur in the currently focused window forcing you to iterate through all (i)frames and windows to check for errors. This can still be seen as a minor issue but the real problem is that captured errors get lost when a new document is loaded. At the end this solution allows to capture some JavaScript errors but not all JavaScript errors.
Add support within the FirefoxDriver
Firefox allows extensions to get notified of JavaScript errors, no matter where they occur.
This mechanism is used for instance by Chris Pederick’s famous Web Developer Toolbar to display a warn/error icon when an error has occurred on a page. Once you’ve succeeded in overcoming the sandbox mechanism separating extensions and loaded pages, it is quite easy to write a new Firefox extension that captures the JavaScript errors and makes them available in each content window.
WebDriver on its side allows to add custom extensions to run in a
FirefoxDriver. If you simply add this errors capturing extension to the
FirefoxProfile you’ll have access to all JavaScript errors from within your tests. Luckily you don’t need to write it again and you can simply use my JSErrorCollector (Apache 2 Licence). It allows to write following:
... import net.jsourcerer.webdriver.jserrorcollector.JavaScriptError; ... final FirefoxProfile profile = new FirefoxProfile(); JavaScriptError.addExtension(profile); final WebDriver driver = new FirefoxDriver(profile); // ... // navigate to some pages // ... List jsErrors = JavaScriptError.readErrors(driver); assertThat(jsErrors, is(empty())
The
JavaScriptError class holds the message, source name and line number of a JavaScript error just like what you can see in Firefox’s JavaScript console.
Next steps
Other browsers
It would be nice to have a simple access to JavaScript errors as well in the other browsers supported by WebDriver. For HtmlUnit it is a no-brainer. For Chrome it should be quite simple as an extension can register a global error listener. No idea what concerns IE and Opera.
Integration
Ideally the API should be provided natively by WebDriver, let’s see what will be the interest in my JSErrorCollector (follow issue 148 to stay informed).
Retrieving the JavaScript errors is a first step on which different interesting features could be based. Verifying the absence of JavaScript errors after each test (using for instance JUnit’s @After) works fine but is tedious. One interesting feature would be to let the tests directly fail on the first JavaScript error (I’ll address wrapping drivers in a future post). Alternatively a precise dedicated reporting would have great benefits too. Some filtering features to ignore errors in third party libraries would be a nice feature as well.
JSErrorCollector is open source therefore patches are welcome. If you can’t/don’t want to contribute directly, I’m available to work on it on a contract base.
Aaron Broad said,
October 11, 2011 at 3:35 pm
How difficult would it be to use your Firefox Extension in Ruby?
I’ll be experimenting to find out this afternoon…
Marc Guillemot said,
October 11, 2011 at 5:52 pm
I don’t know WebDriver’s Ruby binding but according to you can add an extension to the Firefox profile and according to you can execute JavaScript code as well. It will therefore be possible to use the extension from Ruby as well.
Aaron Broad said,
October 11, 2011 at 5:54 pm
Thanks.. I”ll get it working and make a github fork with a ruby example. This is a lifesaver on my current project if I get it working. Thanks for your efforts!
Gabe Kopley said,
November 17, 2011 at 12:27 am
Here’s how I am using it with Rails+Capybara+Cucumber:
Yaci said,
November 7, 2011 at 11:43 am
I am using different extension that I found somewhere on the web. It captures the content of Firefox error console and saves it to a file.
Quite easy way of checking for JS errors is setting XRE_CONSOLE_LOG environmental variable, which will cause Firefox to automatically log all sort of errors. However in this case a log is produced after closing the browser, so there’s no way of relating an error with a page on which it occured.
Nice post btw, thanks for sharing. :)
Gibeden said,
November 30, 2011 at 7:13 am
Hello.
Is it possible to use your Firefox Extension in C#?
Marc Guillemot said,
November 30, 2011 at 7:28 am
Sure. The extension itself (the .xpi file) has nothing to do with Java. Just have a look in the code to see how errors are retrieved and you can do the same in C# (you can look at the Java code or at Gabe Kopley’s Ruby code). Feel free to send me a push request for your C# integration if you find it could be useful for other users.
Tim said,
February 5, 2012 at 2:27 pm
where can I find .xpi file ??
I did not find it :(
Marc Guillemot said,
February 9, 2012 at 7:53 am
The XPI file was available in the jar file but I agree that it was not easy to get it.
I’ve now made it directly available:
Gibeden said,
December 15, 2011 at 3:12 pm
Hello.
How to clear all JS errors catched by JSErrorCollector?
I just want get all JS errors after some action (click e.g.), not all JS errors from start of my test case.
Marc Guillemot said,
December 15, 2011 at 3:34 pm
Just call for captured errors before the action and discard the result.
Gibeden said,
December 15, 2011 at 7:24 pm
I’m sorry, but i think i didn’t understand you =(
could you please explain more?
Gibeden said,
December 16, 2011 at 11:41 am
if you don’t mind i allowed myself to make some changes in your overlay.js on line 17:
this.list = [];
now it works exactly what i need.
A Smattering of Selenium #83 « Official Selenium Blog said,
March 14, 2012 at 7:41 pm
[…] WebDriver: capture JS errors while running tests is a JS way of capturing JS errors on a page […]
Yong said,
March 16, 2012 at 5:35 am
If this can be used for RemoteWebDriver?
Marc Guillemot said,
March 19, 2012 at 8:16 am
No idea. It depends wether a Firefox extension can be deployed to a RemoteWebDriver instance or not.
Alper said,
March 16, 2012 at 11:07 pm
Does not work for me. I use selenium-java 2.20 and Firefox 11. The browser displays “JSErrorCollector: 0″ in the addon bar. But if an error occurs, the counter is still zero and “JavaScriptError.readErrors(webDriver)” returns an empty list. Any ideas?
Marc Guillemot said,
March 19, 2012 at 8:11 am
Surprising. Is the JavaScript error visible in Firefox JavaScript console?
Alper said,
March 19, 2012 at 9:59 am
No it is not showing in the console.
Marc Guillemot said,
March 19, 2012 at 10:25 am
If FF console doesn’t show any error then it means… that there is no (un-catched) JS error and therefore no error can be captured ;-)
Alper said,
March 19, 2012 at 10:51 am
Makes sense. Nevertheless, Selenium/Webdriver says:
org.openqa.selenium.WebDriverException: null (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 24 milliseconds
Build info: version: ‘2.20.0’, revision: ‘16008’, time: ‘2012-02-28 15:00:40′
System info: os.name: ‘Linux’, os.arch: ‘amd64′, os.version: ‘2.6.35-32-generic’, java.version: ‘1.6.0_20′
Driver info: driver.version: RemoteWebDriver
Marc Guillemot said,
March 23, 2012 at 7:37 am
Hmm, this looks like an internal WebDriver error, not like a JS error on the tested page :-(
Alper said,
March 23, 2012 at 9:19 am
I am sure that these are JavaScript errors. Because if everything works fine and I execute invalid js code, the error above is thrown.
yishai said,
March 20, 2012 at 3:52 pm
I’m using Chrome, so I don’t have the benefit of FF profiles.
Instead, my test inserts the code you suggested at the beginning of your post.
Unfortunately, when an error is triggered, all I get in window.collectedErrors is “Script error.”, instead of the full error description with source and line number.
I’ve found a StackOverflow thread that this may be due to chrome’s same-origin policy.
Has anyone run into this?
Suggestions?
Thanks for your work and the great post
Andreas Tolf Tolfsen (@tolfsen) said,
March 22, 2012 at 5:08 pm
There are plans for adding ways of opting in on the JavaScript console in the WebDriver. That said, not much work has so far been done on specifying this in the forthcoming WebDriver specification
You can have a look at the work in progress here:
If you have time and energy to submit for a patch for it, please feel free to.
Opera already has a console-logger Scope service which allows you to tap in to one or more of the ecmascript, java, m2, network, xml, html, css, xslt, svg, bittorent, voice, widget or selftest logs during runtime. This has however not been exposed in OperaDriver yet, but my plan is to do so once we’ve established a good API for it.
Marc Guillemot said,
March 26, 2012 at 3:31 pm
You’re right, the OperaDriver features have some advance in this area compared to other drivers. Congratulations for it!
Sadly my feeling is that the persons involved in other drivers are not particularly interested in such a feature. The resonance to the opened issue was really limited.
Jan Kester said,
March 23, 2012 at 11:55 am
Is this JSErrorCollector also available from maven repository?
Marc Guillemot said,
March 23, 2012 at 12:02 pm
No, it isn’t. I have some other “WebDriver goodies” I’d like to pack together before publishing them to the Maven repository but I haven’t found time to continue working on it.
Sumit said,
May 9, 2012 at 4:49 pm
Hi Marc
Can you please help me out for the same java script error for Internet Explorer webdriver in selenium.
It will be really great help
Marc Guillemot said,
May 10, 2012 at 5:58 am
Hi Summit,
as written above, I have no idea how something similar could be done with IE :-(
Manpreet Singh said,
May 10, 2012 at 10:03 pm
Hello Marc,
Thanks for the brilliant effort. It helped me. Works on FF#12 and Selenium 2.21. Keep up the good work.
sai said,
July 12, 2012 at 12:05 pm
Hi mark
unable to get jserror.
i have tried the following code, putting some java script error on the page load.
import java.io.File;
import java.io.IOException;
import java.net.*;
import java.util.List;
import net.jsourcerer.webdriver.jserrorcollector.JavaScriptError;
import org.junit.*;
import org.junit.runner.RunWith;
import org.junit.runners.BlockJUnit4ClassRunner;
import org.openqa.selenium.*;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeDriverService;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.firefox.FirefoxProfile;
import org.openqa.selenium.remote.DesiredCapabilities;
import org.openqa.selenium.remote.RemoteWebDriver;
public class selOneGrid {
static WebDriver driver;
public static void main(String []args) throws Exception{
FirefoxProfile ffProfile = new FirefoxProfile();
JavaScriptError.addExtension(ffProfile);
final WebDriver driver = new FirefoxDriver(ffProfile);
driver.get(“”);
List jsErrors = JavaScriptError.readErrors(driver);
System.out.println(“Js errors….”+jsErrors.isEmpty());
//assertTrue(jsErrors.toString(), jsErrors.isEmpty());
}
}
sai said,
July 12, 2012 at 12:08 pm
getting exception Exception in thread “main” org.openqa.selenium.UnhandledAlertException: Modal dialog present
iam using selenium-standalone-server-2.19.jar and firefox 13
Marc Guillemot said,
July 13, 2012 at 8:14 am
Just read the name of the exception class, it says everything ;-)
Arun said,
March 20, 2013 at 5:43 pm
Hi Mr Sai.
i am new to selenium and i get the same exception
org.openqa.selenium.UnhandledAlertException: Modal dialog present
as you get.
did you over come this problem?
can you please give me a sample example.
I appreciate you help
Arun
Jan Kester said,
July 19, 2012 at 11:41 am
I don’t get it working. I see the eror collector gets installed (in lower right corner of firefox browser, it says errorcollector 0 items).
Then I try to invoke a js error with:
String statement = “addsdsd();”
JavascriptExecutor js = (JavascriptExecutor) driver;
js.executeScript(statement);
I get a failure on selenium client side:
Exception thrown: null (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 41 milliseconds
Build info: version: ‘2.24.1’, revision: ‘17205’, time: ‘2012-06-19 15:28:49′
System info: os.name: ‘Windows 7′, os.arch: ‘x86′, os.version: ‘6.1’, java.version: ‘1.6.0_25′
Driver info: driver.version: RemoteWebDriver
Session ID: 3d3635cd-f06e-40d8-aa31-0dc8658e6690
So no information on JS error (function not defined I was expecting). Afterwards my JSErrorCollector is empty :-(. It also does not show me the error.
I am using selenium java driver 2.24.1, and firefox 13.0.1.
Regards, Jan Kester.
skhanam said,
August 7, 2012 at 10:21 am
Hi There,
Would someone let me know how to use it with C# pls.
Am on WebDrover C# bindings 2.25.1 & FF14
cheers,
s
promdesign said,
August 29, 2012 at 1:42 pm
yes, you can.
look here
skhanam said,
August 7, 2012 at 1:15 pm
Hi There,i’ve got it highlighting JSError has 1 issue
How do i grab that jsError message ..
i want to grab is how
Bryan said,
August 14, 2012 at 11:31 pm
A really useful addition would be to clear the errors, not just read them. Would help when you have multiple tests running and you want to more easily isolate where the errors happened.
Marc Guillemot said,
August 16, 2012 at 3:25 pm
This is already the case: each call to read the errors resets the captured errors list.
Bryan said,
August 16, 2012 at 4:18 pm
Well that was easy! Awesome tool!
Benjamin Söltenfuß said,
August 30, 2012 at 7:35 am
Hi,
first of all I want to thank you for this great Tool!
I have a topic which is simliar to this and as you are the only one which i know, who has solved to communicate between selenium webdriver and a firefox plugin, i ask you ;-) .
I want to call a js function from a plugin called wave () . Namely the “wave_viewIcons()”-js-function.
So similiar to your JS_Error_collector, i tried it with:
((JavascriptExecutor) selenium).executeScript(“window.wave_viewIcons()”);
(also some other calls which neither work)
to call this function via Javascript (The Addon is already running in the Firefox profile from the webdriver and i can see it in the toolbar). Sadly this is not working. So my question:
How can you communicate with a Firefox-Plugin? Do you have an Idea how to communicate and call a js-function from wave?
Thanks a lot for your help!
Marc Guillemot said,
August 30, 2012 at 11:47 am
I suppose that this is a problem of scope.
JavascriptExecutor.executeScript executes the provided script in the scope of the current window and therefore can only see objects/functions defined in this scope. For this reason, the JSErrorCollector places a reference to the object containing the collected errors as “JSErrorCollector_errors” in each window.
Benjamin Söltenfuß said,
August 30, 2012 at 12:17 pm
Sadly i am not so into JS, can you explain how to place such a reference in each window? You would help me very much!
promdesign said,
September 26, 2012 at 9:54 am
Is it possible to use with Google chrome?
If yes – how?
Graham Wheeler (@geekraver) said,
September 28, 2012 at 4:28 pm
Could you please add a software license to this? I would like to use it at work but cannnot without a clear license.
maria said,
December 3, 2012 at 4:36 pm
Hi ,
I’m glad that i found this article . I am having a problem . I’ve used the first ,method and injected the js code into a VerifyedLoading function and tested manually and seems to work.
The thing is that when using webdriver to click on an element (a js error should occure) and it doesn’t appear any error in the console .
There are some differnces between user click and webdriver click ?
Or it could be something eles?
Thanks
Kay Wattel Te said,
December 13, 2012 at 8:34 am
I am using jsErrorCollector and getting following error while running a test on Win 7 machine with Firefox 16:
window.JSErrorCollector_errors.pump is not a function
Same code works well on my Win XP with Firefox 16.
Kay Wattel Te said,
December 13, 2012 at 9:28 am
Oops. That was because of Firefox 17 (not 16) on the other machine.
Fixed by downloading latest jar (JSErrorCollector-0.4.jar)
Thanks.
Michael said,
September 9, 2013 at 5:43 pm
I am getting the same thing with version 0.4 and 0.5. I am running with FireFox v19.xx.
Actually, with these two more recent versions the error message just says:
window.JSErrorCollector_errors is undefined
Using WebDriver to automatically check for JavaScript errors on every page | WatirMelon said,
December 19, 2012 at 11:51 am
[…] checking for JavaScript errors on page load. There’s a couple of approaches out there, one involves copying and pasting a small snippet of JavaScript into each page. Since our application we […]
Sandy said,
January 28, 2013 at 3:03 pm
Mark,
I am using JUnit webdriver to test my pages. I am trying to use your amazing extension in my firefox profile. You have given an example how to use it in Ruby. Can you please give a snippet how to do it in Java Junit? I mean I can add the extension using driver.addExtension(.xpi file). But how should I catch the errors? Shall I call the method window.JSErrorCollector_errors.pump() on each page load? shall I call it after testcase? I am bit confused here. Kindly help
Marc Guillemot said,
January 29, 2013 at 6:57 am
Sandy, if you look at, you’ll see that the code example is in Java.
How often you call
JavaScriptError.readErrors(driver);is up to you. I would call it at least once at the end of each test.
Sandy said,
January 31, 2013 at 9:19 am
Thanks Mark.
Simeon said,
February 14, 2013 at 6:46 am
Dear Marc.
Please tell me, how to make it work with Google Chrome?
John said,
February 15, 2013 at 10:41 am
I have the same question!
Marc Guillemot said,
February 15, 2013 at 12:31 pm
As mentioned above I think that it should be possible to write an extension for Chrome doing the same thing but I don’t know such an extension.
Peter said,
February 15, 2013 at 2:21 pm
I’m testing JSErrorCollector, with Selenium 2.29 and FF 18 and don’t work ….. the extesion is installed in FF correctly, is ther any problem with these versions?
Simeon said,
February 15, 2013 at 2:24 pm
I’m testing with the same configuration: FF 18.0.2, WD 2.29.1.0 – works perfect.
Peter said,
February 15, 2013 at 2:39 pm
If I execute window.JSErrorCollector_errors.pump() it’s return nothing []… I insure that the web is loaded completely, any help
Peter said,
February 18, 2013 at 10:33 am
Hi,
It is necessary install other extension, firebug?, Simeon could you tell me witch extensions have installed? thanks
Peter said,
February 18, 2013 at 10:32 am
Hi,
It is necessary install other extension, firebug?, Simeon could you tell me witch extensions have installed? thanks
Simeon said,
February 18, 2013 at 10:49 am
Hello Peter. It works properly with firebug installed and without. Checked myself.
Peter said,
February 18, 2013 at 12:30 pm
My code is, could you help me please, I don’t Know what is incorrect
FirefoxProfile profile = new FirefoxProfile();
profile.addExtension(JavaScriptError.class, “c:\\JSErrorCollector.xpi”);
profile.setPreference(“javascript.enabled”, true);
FirefoxBinary binary= new FirefoxBinary(new File(“C:\\Archivos de programa\\Mozilla Firefox\\firefox.exe”));
driver = new FirefoxDriver(binary,profile);
driver.get(URL);
System.out.println(“Result document.readyState: “+ ((JavascriptExecutor)driver).executeScript(“return document.readyState”));
The docuemnt is completed
System.out.println(“Result JSError: “+ ((JavascriptExecutor) driver).executeScript(“return window.JSErrorCollector_errors.pump()”));
System.out.println(“Result JSError: “+ ((JavascriptExecutor) driver).executeScript(“return window.JSErrorCollector_errors.list”));
Nothing is written
jsErrors = JavaScriptError.readErrors(driver);
System.out.println(“###start displaying size errors: “+ jsErrors.size());
for(int i = 0; i < jsErrors.size(); i++) {
System.out.println(jsErrors.get(i).getErrorMessage());
System.out.println(jsErrors.get(i).getLineNumber());
System.out.println(jsErrors.get(i).getSourceName());
}
System.out.println("###start displaying errors");
Thread.sleep(3000L);
Nothing is written
Thanks!!!
Skip Huffman said,
March 6, 2013 at 4:13 pm
Excellent tool. Thank you.
Brad said,
April 26, 2013 at 1:36 am
Thanks for your post..that was handy..
At the moment i’m facing an issue when I executed this script, it displays the output in the browser which is correct but the script did not complete its execution and browser keep on running infinitely which displays “connecting..” on top of browser.
It requires me to close the browser manually which throws another exception connecting to remote browser. But my question is why the test script did not complete execution and why the browser keep on running once it has rendered the output. I’m using Selenium Webdriver (selenium-2.31.0) and I’m using Java as my programming language. If anyone can help me to address this one that’ll be helpful
driver – new FirefoxDriver();
htmlString =”return document.write (‘Print the Test values in html format’);”;
((JavascriptExecutor) driver).executeScript(htmlString);
Any help on this will be helpful as i’m struck on this.
Marc Guillemot said,
April 26, 2013 at 4:26 am
This has nothing to do with capturing JS errors, isn’t it? I think that this is rather a question for WebDriver’s mailing list… or that you should simply NOT use document.write.
Brad said,
April 26, 2013 at 4:49 am
Yep..i think this is more relevant to Webdriver’s mailing list.. sorry if I’m at the right place.. but if you have any updates on this.. Pls let me know..
Thanks,
Brad
Simeon said,
August 13, 2013 at 8:43 am
Now we have the same plug-in for Chrome. It’s here –
It is very similar to JSErrorCollector.
Jeff said,
August 27, 2013 at 3:21 pm
Use JSErrorCollector.xpi and Chris Pederick’s Web Developer Toolbar (web_developer_1_2_5_sm_fx.xpi) together. JSErrorCollector will catch the error inside Web Developer Toolbar:
{u’sourceName': u’’, u’errorMessage': u’TypeError: $.browser is undefined’, u’console': u’Error extracting content of Firebug console: Firebug.currentContext.getPanel(…) is null’, u’__fxdriver_unwrapped': True, u’lineNumber': 12}
Benno said,
January 2, 2014 at 9:28 pm
This is a great tool! I used it when I took over a project from someone else. I wasn’t sure about the javascript code quality, so I placed JSErrorCollector into existing Webdriver tests. And so it gave me a heads up on which pages had errors.
Again great work!
Thoughts on a Selenium interactive exploratory test and debug tool | autumnator said,
January 24, 2014 at 7:12 am
[…] (sort of) cross browser javascript error collector functionality for debugging with Selenium. Have buttons to inject the javascript error collection […]
pooja said,
February 21, 2014 at 1:34 pm
Hi Marc ! Excellent work! thanks for writing it…
however does it support capturing warnings? I did try but it didn’t find any warning (jsErrors comes empty list, though teher is a warning on the navigated page) . Kindly please update.
Rashi said,
April 9, 2014 at 6:43 pm
When will this jar be available in Maven?
kaat said,
May 29, 2014 at 1:52 pm
A maven jar would be really great
Fix Capturer.js Errors - Windows XP, Vista, 7 & 8 said,
October 3, 2014 at 10:06 pm
[…] WebDriver: capture JS errors while running tests | Marc … – Oct 11, 2011 · The stack trace of an exception in a log file is a sign that something went wrong. Even if nobody complains it is wise to take a bit time and investigate …… […]
sarose said,
November 25, 2014 at 12:40 am
Hi Marc,
I have implemented this code in my script, to test it, I invoked some js errors on the web page, and executed this method, when I checked the log I am getting window.JSErrorCollector_errors is undefined
Can you tell me what wrong am I doing here? I can email you the related code if you can take a look. thanks,
Thanks,
-Sarose
Fix Junit Errorcollector Api Windows XP, Vista, 7, 8 [Solved] said,
November 30, 2014 at 6:09 am
[…] WebDriver: capture JS errors while running tests | Marc … – Oct 11, 2011 · January 28, 2013 at 3:03 pm. Mark, I am using JUnit webdriver to test my pages. I am trying to use your amazing extension in my firefox profile. You have …… […]
Inconsistent results when capturing javascript errors with WebDriver | CL-UAT said,
December 29, 2014 at 6:53 pm
[…] using a technique I found here, to capture javascript errors for testing purposes. It’s a technique that is frequently […] | https://mguillem.wordpress.com/2011/10/11/webdriver-capture-js-errors-while-running-tests/ | CC-MAIN-2015-22 | refinedweb | 4,773 | 65.12 |
» Publishers, Monetize your RSS feeds with FeedShow: More infos (Show/Hide Ads)
NFLweather.com has an interesting RSS feed of all NFL game weather reports. They also have widgets..
It's funny. If you look, there's neat little XML Web services all over the Internet. And behind those Web services is data. Also known as virtual gold.
The last week or two, I've been playing extensibly with FOAF (Friend Of A Friend). This is an XML/RDF vocabulary intended to describe people and their friends. This is a great idea and something we really need to tie the Web together and make it work the way us uber-geeks invision the Web working. Imagine if social websites could share information? The similar friends. Import friends. Import profile data.
Unfortunately, FOAF has major problems and as such is not good enough for this job. The biggest part of the problem is ownership and intellectual violence. By this, I mean that this vocabulary is controlled by few people who are unable to put the time into the language that is necessary to make it succeed. Also, these people suffer from an intellectual superiority complex that makes working with them impossible. This is true of pretty much anybody involved with RDF or for that matter XML.
FOAF was apparently created in 2000 (11 yrs ago) and remains in the pre-version 1.0 state. How can it possibly take 11 yrs to create the initial version of this language? I've been complaining on this blog about the half-baked FOAF spec since 2004. In fact, no updates to the specification have been made in the last 16 months.
Eleven years now and only one version of the grammar exists; 0.1 according to the namespace. Yet this 0.1 version contains archaic elements. A large percentage of the published FOAF is using elements which are no longer valid.
The slow pace of this spec is allowing it to fall behind the times and get further away from the reality of today. Old news Internet chat sites like AIM and ICQ are tightly integrated into the vocabulary while modern day Web successes like twitter and Facebook are rarely ever implemented by publishers.
Today, I was wondering how to implement cell, work and home phone numbers. I was unable to discover a method that doesn't break the basics of RDF. In fact, I found threads discussing this problem that date back years and no acceptable solution was found.
Recommendation: Either the people who control FOAF release it to people who have the time to move it forward or they deprecate the XML and allow something else to step in and take it's place.
References hour per secondary domain. Don't wanna piss anybody off. I might increase that in time. I'm gonna make the data available online at some point.
Update: Most recent stats
Continuing to play with the twitter API. See Part Un.
Last couple days, I made a new C# program to find ppl I'm following on Twitter that didn't follow me back. I, of course, unfollowed them.
I had to cache my friends XML, since the 150 call per hour rate limit, made it impossible to run once. The code follows. Hope you like and re-use.
static string userid = "137692493"; static void FindNoFollows() {( string.Format("//id[text()='{0}']", userid)); if (dt != null) { continue; } s = string.Format("{0}", e.InnerText); d = new System.Xml.XmlDocument(); d.Load(s); dt = (System.Xml.XmlElement)d.SelectSingleNode("//screen_name"); System.Diagnostics.Process.Start(string.Format("{0}", dt.InnerText)); } catch { break; } } }
Yesterday, I did something fun and played with the twitter API. I was trying to reduce my twitter followings and want to purge all followings with no activity in the last month. With 900+ followings, that would be too much to hand manually, so automation to the rescue.
This required the use of 2 API calls.{0}{0}
One to load the list of my friends and the 2nd to turn that list of ids into user profiles. You can then check the creation date of the users status to get his last activity date.
Because of the REST XML API style, this was trivial to use. Not to mention the documentation on the website was better than adequate. I did find a few problems using the API.
- Complete lack of use of XML attributes. Even when attributes are called for, they use XML elements instead. Not the 1st time I've seen this usage style. Not a biggy either.
- Date times don't use the standard XML date-time format. In fact, I don't recognize the format at all. Neither did the C# Convert.ToDateTime function.
- Usage rate of 150 calls an hour was completely inadequate. I needed almost 1000 calls to accomplish my simple task.
Code follows
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace ConsoleApplication1 { class Program { static void Main(string[] args) {("//status/created_at"); if (dt != null) { string dt2 = dt.InnerText; dt2 = dt2.Substring(4, 6); System.DateTime dateTime = Convert.ToDateTime(dt2); if (System.DateTime.UtcNow.AddMonths(-1) < dateTime) { continue; } } dt = (System.Xml.XmlElement)d.SelectSingleNode("//screen_name"); System.Diagnostics.Process.Start(string.Format("{0}", dt.InnerText)); } catch { break; } } } } }
Fun and task accomplished. Thanks twitter. I got rid of a few dozen twitter followings.%.
Even when I get notifications, its usually pokes. I really don't want to be notified of pokes.
The only thing I like about is the Places functionality which allows me to put on my wall my cureent location. Other than that, FB for Crackberry royally sucks.
Thought I'd publish some interesting Web browser stats from my site.
- Internet Explorer fell from 53% share of visits to 43% comparing the last 12 months to the 12 previous to that.
- Firefox fell from 23% to 18%
- Safari is up from 17% to 23%
- Chrome is up from 4% to 8%
- Android browser went from 0 visits to 1%
OS
- Windows fell from 78% to 67%
- Mac grew from 14% to 15%
- iPhone from 3% to 7%
- Android from 1% to 4%
- Blackberry from 1% to 2%
- iPod from 1% to 2%
- iPad from near 0 to 2% whether economical or natural or
otherwise from undergoing domestic crises similar to those in the Middle East.
Not even.
One thing I can't stand is websites that are designed for mobile devices, but that simply don't work on my Blackberry. Are they testing on the Blackberry. Makes you wonder.
Today my complaint is formspring.me. There's a nav bar at the top of the page that is repositionned when you scroll. I scroll down to see more content and the nav bar repositions itself, quite often over top of the area I'm trying to read. When I try to scroll right, the nav bar respositionning forces the screen back to the left. I can't see anything on the right side of the screen.
You know when you click on a new tab in Internet Explorer 8. The tab is created and the tab title says "Connecting...". It actually takes a second to connect. Then the tab appears with the address about:Tabs. Why is that? What is it connecting to? Why does it take a second? Just a thought for any Microsoft engineers out there.
If you want to have an effective and successful online business it’s essential to have a visible web site. Regardless if your business is new or not, you’re main goal should be to increase your online traffic. More traffic translates into more clients, advertisers, and sales. If you have these essential components then you’re going to make more money.
The quality of your product or service is key, but if no one knows about it then you’re not going to be successful. There are several methods of increasing traffic but most of this derives from the use of search engines. High traffic received through free sites, such as Google, Yahoo, and others, make the effectiveness of your site’s search engine ranking paramount.
If you’re currently looking for ways to improve your online traffic and ranking, then you’ve probably already come across an SEO consultant offering their expertise. If you’ve never contacted an SEO company before, you’re’s search engine optimization takes time, but it’s long term results will pay you back in dividends. In the end, it can be more costly not to seek the assistance of one of these companies.
I'm looking for ways to integrate twitter into the website. Listing a few URLs that I've found.
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I'll report back with my successes latter. TwitThis looks like an easy 1st step, but I've suprised you'd need a 3rd party hack to get this. Search apiwiki for similar.
Update: Tweet Button is exactly the 1st step I was looking for. | http://reader.feedshow.com/show_items-feed=f0084f25b0af3ef06c6fb2a1eadf9356 | CC-MAIN-2014-49 | refinedweb | 1,496 | 67.86 |
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