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Agenda
See also: IRC log
<bob> meeting: WS-Addressing Teleconference
<bob> chair: Bob Freund
<scribe> Scribe: anish
Agenda
<scribe> Agenda:
Minutes approved.
<scribe> Chair: bob
Paul Knight to respond to commenter: Paul not on the call
Tony Rogers to post a new editors’ draft – Done
Anish: what is the status of embedded policies in EPRs
Bob: they decided not the engage on that
Tom: epr has a metadata section and no one has addressed how to embed policy assertion
Philippe: do we have more information to give them?
Bob: don't know how they decided on not dealing with this issue
<plh>
Philippe: looks like that issue in ws-policy wg is reopened
<TRutt_>
Philippe: we might want to
express interest in this issue to ensure that we are inthe
loop
... any recommendation that we would like to give them?
paco: my view is that we can't take over every metadata
plh: now that we are doing a metadata document but we could certainly do this
paco: not in favor of doing this
tom: why don't we ask them to do this
bob: somebody has to do this or it is going to show up in ws-i
plh: some people argue that it is the job of the metadata exchange
anish: little different from metadata exchange
paco: but it is part of metadata
anish: seems like the syntax is within our purview
paco: policy in a EPR opens a lot
of questions
... some assertions are message specific
... more of a policy thing rather than ws-addr thing
bob: agree with paco
tom: not our job to do that
anish: do we need to point out that we thing it is their job
bob: we can just say that we are
interested in the outcome of issue 4129
... is that a reasonable approach?
... any other point that we would like to provide feedback on?
... we'll provide that feedback
Tony: changes raised more questions than expected
<scribe> ... new version is up as an editors draft
UNKNOWN_SPEAKER: big changes:
delection of section 3.2 and added new section 3.2. New section
is David's text.
... with the modification of s/AddresingRequired/Addressing/
<bob> ACTION: bob to sent a LC review response to WS-Policy wrt bugzilla 4129 [recorded in]
UNKNOWN_SPEAKER: 1st note is
about policy attachment option
... using prefix wsaw, should this be called something else like wsam
plh: i though we decided to use /metadata instead of /wsdl for the namespace, including for UsingAddressing
<gpilz> +1
Tony: the old UsingAddressing is
a policy assertion as well. The new one is a policy assertion
only
... new NS prefix will be 'wsam'
... most of 3.2 is a list of example
... will need minor revision to change the prefix
... David, would you tell if there are any errors?
David: will read it and let you know
<bob> ACTION: david will review sec 3.2 examples in a day or two [recorded in]
<bob> ACTION: bob to sent a LC review response to WS-Policy wrt bugzilla 4129 [recorded in]
<discussion of editorial issues between plh and tony. details not captured>
<plh>
<Zakim> plh, you wanted to follow up on empty nested policy
plh: on the issue of empty nested policy, i don't think it is required to have the empty nested policy for the intersection to work
David: the policy framework section 4.3.2 has a Note. That note makes me think that it needs an empty wsp:Policy element
bob: would you like to provide that as an input to the ws-poilcy WG as an LC comment
Marc: i agree with David. I got some quick confirmation from some folks. I believe that it is right.
Bob: I would suggest going to the policy wg if the describe is not clear
plh: i believe david is right
Bob: the note to ws-policy wg is not required then
<plh> [[/> ]]
<plh> from
Tony: the next Q is related to
the bibliography. I have put in ws-policy framework and primer
as normative.
... the docs are working draft
anish: does primer need to be normative rather than informative?
tony: don't have a problem with
that
... if the other 2 docs (framework and attachments) are normative, is that a problem?
plh: we can't be a rec until policy is PR
marc: but we are going back to LC so they are ahead
bob: but now we need their implementation to advance
Katy: we need to specify the wsp prefix in the table
tony: good point. will add that.
Marc: we still need to note the subject-level of the assertion
plh: my email covers that
bob: are folks in agreement with that?
no disagreement
<plh>
plh: one thing to note is that in my note i recommend staying silent.
tony: makes sense
<plh> s/one thing to note is that in my note i recommend staying silent./one thing to note is that i recommend staying silent for other attachment points./.
Tony: on action, i changed the reference. reference to explicit association and reference to rules for the default.
<bob> tony's first mail:
<plh> "The inclusion of wsaw:Action without inclusion of wsaw:UsingAddressing has no normative intent and is only informational."
tony: we probably need UsingAddressing or the presence of addressing policy assertion
plh: worried about saying
'presence'
... can be optional
tony: will have to think about this.
anish: we could talk in terms of policy alternative
<scribe> ACTION: tony to propose words to resolve this [recorded in]
<bob> ACTION: Tony to tinker up some words which will confuse everyone [recorded in]
<scribe> ACTION: 3 to [recorded in]
ACTION 3-
ACTION 3=
ACTION 5=
<plh> ACTION 3=Tony to tinker up section 4.4.1 to include the policy assertions as well
<bob>
Tony: the next email that i sent
concerns CR33
... i went ahead and did (a) but not (b). Did include (c), and (d)
... one Q is 'we are still using UsingAddressing?'
bob: that is another issue
Tony: next email is about CR38.
which we have already dealt with.
... then there are DavidHull's point
plh: they are editorial, we can do this on the ML
bob: there was some sympathy
about shortening, breaking up of sentences.
... we'll continue the editorial discussion on the ML
... noticed that there is no change to the issues list
tony: there have been changes.
bob: did not see any changes
tony: the remaining CR issue on
ed issues: 34 (moot now), 33 (we just resolved), 32 (is about
'none' uri -- still not done), 38 (we settled today)
... so the only remaining is 36.
... is that an erratum
bob: no, as an edition
... as a PER then then a 2nd edition
tony: will finish the metadata doc by friday
katy: minor thing -- in the
conformance section do we need something about conformance to
the assertion
... section 6
tony: will do that using my editorial powers
anish: if we have changed the NS, then we don't need this
tony: if people want to indicate addressing in wsdl then they won't have anything any more
katy: the disadvantage of having this would be that we would have to specify how it interacts with the assertion
tony: agree that it should be cut
bob: anyone in favor of retaining it?
noone favors it
no objections to removing it.
decision: UsingAddressing will be removed
<bob> resolution: usingaddressing shall be cut
Announcement of new public working draft 2007-01-16
LC start 2007-01-30
LC end 2007-02-20
LC issue resolution estimate – 4 weeks ~ 2007-02-26
CR start <Policy dependency?> ~2007-02-27
CR end start plus four weeks ~2007-03-20
<bob> Proposed:
<bob> Announcement of new public working draft 2007-01-16
<bob> LC start 2007-01-30
<bob> LC end 2007-02-20
<bob> LC issue resolution estimate – 4 weeks ~ 2007-02-26
CR Issue resolution estimate – 2 weeks
PR start 2006-03-27
<bob> CR start <Policy dependency?> ~2007-02-27
<bob> CR end start plus four weeks ~2007-03-20
<bob> CR Issue resolution estimate – 2 weeks
<bob> PR start 2006-03-27
bob: do we need to announce what
we have as a new WD
... prior to the begining of the LC period
... I was suggesting that we make a public draft available as early as next week
... i would like to get the completed document and review it and hopefully can be within a small delta of the public draft
plh: the LC announcement can be at the same time as the public WD
<plh> [[ After republication as a Working Draft, the next forward step available to the Working Group is a Last Call announcement. The Last Call announcement MAY occur at the same time as the publication of the Working Draft. ]]
bob: start of LC end of this
month
... and minimum LC is 3 weeks
... it is a SHOULD
plh: i would suggest asking all the WG if they would be able to review them in the time frame given
bob: will start spreading the word
plh: send email to wsdl and policy wg regd this
bob: will do that
plh: can skip the TAG
tony: CG meeting would also be a good place to bring this up
bob: assuming 3 week minimum and
assuming that we'll get some comments: 4 weeks of comment
resolution.
... CR start time may be policy dependent
... guessing around 27th feb
... may impact their spec as we have changed our assertion
David: only their primer would be affected
bob: testing resources needed
during end of feb - end of march
... what we have now is going to be easier to test
tom: do we need a f2f
bob: may be good to schedule
one
... david, do u think a 4 week schedule is appropriate?
david: we do have a lot of the design/test, but dependents on how long policy implementation takes
bob: this puts PR at march 27 (with some assumptions)
plh: that is optimistic
... policy wg is starting their CR in march and ending in july
bob: so this could be delayed
because of policy implementations
... any other business?
none
Meeting adjourned. Next meeting, next week
<bob> thanka | http://www.w3.org/2002/ws/addr/7/01/08-ws-addressing-minutes.html | CC-MAIN-2015-27 | refinedweb | 1,707 | 67.59 |
0
I'm writing a pennies game in which a player and the computer take coins from a pile until only one remains. The trouble is I keep getting an error saying "warning C4700: uninitialized local variable 'nuCoins' used" though I thought after the user input a value it would be.
Any help would be much appriciated.
#include <cstdlib> #include <ctime> #include <iostream> using namespace std ; void main() { srand((unsigned)time(0)) ; int number ; int gameStrtNo ; int lowest = 1, highest = 5 ; int range =(highest - lowest) + 1 ; for(int index = 0 ; index < 200 ; index++) { int randNo = lowest+int(range*rand()/(RAND_MAX + 1.0)) ; cin >> gameStrtNo ; int nuCoins = 50 - (number || randNo); if (gameStrtNo <=5) { cout << "Player goes first!\n" ; cout << "Pick between 1 and 5 coins.\n" ; cin >> number ; cout << "There are "<<nuCoins<<" left.\n" ; //ERROR HERE } else { cout << "Computer goes first!\n" ; cout << "Computer picked "<<randNo<<" coins.\n" ; cout << "There are "<<nuCoins<<" left.\n" ; } } } | https://www.daniweb.com/programming/software-development/threads/231690/error-message-c4700 | CC-MAIN-2018-22 | refinedweb | 153 | 66.03 |
Christophe Jolif wrote:
>
> Hello,
>
> Moving from JAXP1.0.x to JAXP1.1, the crimson DOM has deprecated the
> factory API. That's why instead of using it, I would like to subclass
> the XmlDocument and redefine the createElement and createElementNS
> methods to return customized elements for some tag names. It works fine
> with createElementNS but createElement is final and thus cannot be
> redefine.
>
> Is it really intended? Is their any chances that it changed?
I'm not sure what the original reason was for doing this, since that
decision was made before I started working on the code. Probably the
original author wanted to steer developers to the element factory code
or maybe it was for performance. I would expect newer apps would be
using Namespaces and thus the createElementNS() method. The old element
factory code still works for non-namespace XML docs for backward
compatibility. In any case, I just made it non-final in the latest CVS
version.
-Edwin
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For additional commands, e-mail: general-help@xml.apache.org | http://mail-archives.apache.org/mod_mbox/xml-general/200105.mbox/%3C3B09CC0A.3AEBB12F@sun.com%3E | CC-MAIN-2014-52 | refinedweb | 190 | 51.55 |
Wrong window size and coordinates mapping using QML(QQuickView) on Windows 8 (Acer ICONIA W700) with Intel HD Graphics 4000
I have a problem with QML/Qt detecting incorrect screen resolution of Acer W700 (Windows 8) with Intel HD Graphics 4000 (I've tried different versions of the video driver with the same result), while using Qt 5.0.1 for Windows 32-bit (VS 2010).
The actual screen resolution is 1920x1080, while the following code outputs 1536x864:
@
// main.cpp
#include <QGuiApplication>
#include <QtQuick/QQuickView>
int main(int argc, char **argv)
{
QGuiApplication app(argc, argv);
QQuickView view; view.setSource(QUrl("qrc:///main.qml")); view.setResizeMode( QQuickView::SizeRootObjectToView ); view.showFullScreen(); return app.exec();
}
@
@
// main.qml
import QtQuick 2.0
Rectangle {
id: mainRect
Text {
id: thisText
anchors.fill: parent
font.pointSize: 30
font.family: "Helvetica"
horizontalAlignment: Text.AlignHCenter
verticalAlignment: Text.AlignVCenter
text: parseInt( mainRect.width ) + "x" + parseInt( mainRect.height )
}
}
@
The Rectangle actually fills the entire screen and if I draw anything inside it gets properly anchored (everything is drawn properly if I use relative sizes to mainRect).
Since relative drawing works ok, I would be fine with it, but when I use touch interface the coordinates are reported in the correct resolution scale i.e. x: 0..1920; y: 0..1080, this breaks all the code related to touch, especially properties like pressed(). What is more confusing, if I use MouseArea, coordinates are being translated to this incorrect 1536x864 space.
I though at first that my touch screen drivers are broken, but it looks like Qt itself has a defect. Same code works perfectly fine on Windows 7 with NVidia GeForce GT 610 and NVidia GeForce 310.70 drivers, reporting correct screen resolution.
I was wondering if anyone had similar problems and are there any workarounds for this issue? Or maybe I missed something fundamental about mapping screen resolution and internal widget size?
After further investigation, it seems that something more fundamental got broken/changed during transition from Qt 4.8.4 to Qt 5.0.1. The same code for full screen behaves in a similar way if I use QWidget and QApplication classes, so the problem is not Qt Quick / QML specific, moreover I don't have this issue in Qt 4.8.4, only 5.0.1 is affected.
- chrisadams
Please file a bug. This is an area I know nothing about, unfortunately.
Cheers,
Chris.
[quote author="chrisadams" date="1362959588"]Please file a bug. This is an area I know nothing about, unfortunately.[/quote]
I have already submitted one: "QTBUG-30063":
As for now the status is still "Not Evaluated". I hope I used a proper bug tracker.
- chrisadams
Thanks.
Yes, that's the correct bug tracker.
Cheers,
Chris.
when I see this it reminds me a bit on the "device-pixel-ratio" magic that current smart-phones are using when displaying web-content ... maybe Qt5 is using some similar "logical resolution" thing
... at least there seems to be a bigger change behind the "QDesktopWidget::screenGeometry()" API (Qt5 replaced a lot of the platform specific magic with more streamlined QPA-code)
I first thought QScreen(Qt5) might give some more physical vs. logical information, but on a 2nd look there is not really such a separation ...
It turns our that Qt 5.0.1 was not calling SetProcessDPIAware function before the initialization. More details are "here": and "here": | https://forum.qt.io/topic/24859/wrong-window-size-and-coordinates-mapping-using-qml-qquickview-on-windows-8-acer-iconia-w700-with-intel-hd-graphics-4000 | CC-MAIN-2017-51 | refinedweb | 559 | 59.6 |
C is for Cocoaby Seth Roby
07/22/2003
Editor.
Lesson 1: Stay within the Lines
Showing messages 1 through 66 of 66.
- Integers and Whole numbers
2003-12-28 12:15:29 anonymous2 [View]
This is a great tutorial, but I'd like to point something out. Integers are not "the numbers you can count on your fingers". Those are called the "natural numbers". An integer is, in face a number with no fractional or decimal part, but it may also be negative. Whole numbers, then are integers starting at and including 0. What makes natural numbers different is that they don't include 0. I suppose you could count that on your fingers, though the result would be a fist.
- Great job!
2003-09-10 23:32:28.
- Great job!
2003-09-10 23:32:00.
- i think i read something like this on
2003-08-19 19:07:29 anonymous2 [View]
i think i read something like this on
- i think i read something like this on
2003-08-19 19:07:29 anonymous2 [View]
i think i read something like this on
- Way to go!
2003-08-16 08:52:24 anonymous2 [View]
After reading all the posts, all I can say is "Great Job!" I have been struggling with C for 5 years off and on, have bought and read through a number of c books, but ALL OF THEM assume things that you aren't assuming.
- Maybe you should simply recommend particular books for people to learn C from
2003-07-31 08:23:22 anonymous2 [View]
I do not mean to be terribly harsh, but the fact that this article qualified as an article blows my mind. I am a senior in Computer Science at LSU where we have learned C from day 1 and used it ever since as our program is more of a system development program. There is so much more that these people will need to know that you cannot possible fit into even a moderate number of articles.
Here.
- Maybe you should simply recommend particular books for people to learn C from
2003-07-31 10:43:00 tallama [View]
Hi, this is the author.
Yes,).
- Maybe you should simply recommend particular books for people to learn C from
2003-08-29 15:00:09 anonymous2 [View]
I liked this article, but no newer ones seem to be arriving or a book being written on the same idea. Maybe I bookmarked the wrong page (The first C is for Cocoa page) and can't see easily the follow-ups.
Are
- C for the masochists
2003-07-30 00:58:07 anonymous2 [View]
Compared with Perl and Java, C is a difficult language because of the need to manage memory manually and fiddle with pointers. If you are a casual programmer, I would recommend that you stick with languages with automatic garbage collection such as shell/Python/Ruby/PERL/Python/AppleScript. Furthermore, you will probably write more programs in these languages than in C because of their built-in features (regular expressions, etc.).
- C for the masochists
2003-08-02 16:17:52 retro .
- It's about time!!
2003-07-28 15:11:35 anonymous2 [View]
I can't tell you how long I've been waiting for this article!
Please Seth, don't make us wait too long for the next installment. (And as a token of appreciation to your earliest fans, a discount on your book when it is published!)
;)
- Excellent!
2003-07-28 12:52:01 anonymous2 [View]
Thanks for the easy start.
How about a Tutorial for Applescripters to Obj-C?
We already know the structures of a language but need help in translation of concepts from one to the other.
- Learning C first and a word of caution
2003-07-26 03:11:40 anonymous2 [View]
Hi,
With
- Learning C first and a word of caution
2003-07-26 16:31:07 anonymous2 [View]
There's a tutorial for Project Builder at CocoaDevCentral:
I guess you'll be able to find your way in Xcode with that one (basically, just create a Standard Tool project and type in your code into the main.c file...)
- How will new installments be announced?
2003-07-25 02:16:57 hiramnl [View]
I was very happy to discover this tutorial, because just as the author says, an entry into Cocoa that didn't require prior C programming experience was what a lot of people needed. Thanks a bundle! I'd like to be notified, somehow, of new installments. In the O'Reilly mailing list options, I don't see a Cocoa category. Will this be a weekly tutorial? Is e-mail notification of new installments offered?
- Where is part 2 ?
2003-07-24 14:50:05 anonymous2 [View]
Some of us will pay for this type of help.....
- Where is part 2 ?
2003-07-24 21:39:48 anonymous2 [View]
Does anybody know when Part 2 will be released? I'm afraid of missing the next installment. I just don't know what I'd do. If I were to miss it I might just start a spiral downward that could ruin my life. When? Somebody tell me!
- This article is an excellent idea for a book
2003-07-24 05:00:51 anonymous2 [View]
You should write a book, called Programming Objective C. That's the book that's missing from O'Reilly's OS X library: One that isn't focused on teaching you how to use Project Builder and such, but concentrates on teaching the basics of C, then the Objective C superset.
Examples.
- This article is an excellent idea for a book
2003-07-24 06:09:51 cothomps [View]
O'Reilly did publish "Building Cocoa Applications" that starts with Objective C basics (assumes C knowledge.) The book starts off with creating an Objective C program in a plain text editor, compiling on the command line, etc. (Just like you would when programming in C itself)
The book then Introduces Interface Builder, etc. It might not be exactly what you're looking for, but it might come close.
- This article is an excellent idea for a book
2003-07-25 04:56:50 anonymous2 [View]
No, it's not what I'm looking for. As I say, if it were up to me you could skip the Interface Builder part completely (except for (perhaps) a -very- brief introduction in an appendix)..
- This article is an excellent idea for a book
2003-07-25 08:32:18 anonymous2 [View]
I agree. I know C++ and Java, and while I've been told many times that if you know C++ you can figure out C, it'd be much easier for me to just start at the very basics, like this article, and build up. In a book, I'd probably just skip the first chapter and relearn the rest.
- Can I use objective C in Windows?
2003-07-23 22:53:08 anonymous2 [View]
Is there an objective C compiler for MS Windows? I'm afraid I'm stuck with it for the time being.
Thanks.
- Can I use objective C in Windows?
2010-07-20 15:54:32 cleverapps [View]
If you just want to experiment, there's an Objective-C compiler for .NET (Windows) here:
- Can I use objective C in Windows?
2003-07-29 06:02:59 retro [View]
You can use Objective-C with one of the compilers already mentioned, but that alone is not going to allow you to build "Cocoa" applications per se. "Cocoa" is a "framework" or set of prewritten classes and methods (in C they call them "functions") that is unique to the Mac OS X platform. Unfortunately, you will not be able to program applications that use Cocoa from your Windows box.
- Can I use objective C in Windows?
2003-07-29 08:03:17 tallama [View]
Hi, this is Seth A. Roby (the author).
The
- Can I use objective C in Windows?
2003-07-24 07:54:45 anonymous2 [View]
Yes. Check out DJGPP at.
- Can I use objective C in Windows?
2003-07-24 00:17:06 senjaz [View]
While I can't answer that question with a definite I'm reasonably certain: yes.
First
- This made me install the dev tools
2003-07-23 20:10:14 anonymous2 [View]
Thanks. Excellent article. Looking forward to lesson 2.
I had been hesitant to download the developer tools until now. This article convinced me to give it a try.
- Re: This made me install the dev tools
2003-07-23 21:04:40 anonymous2 [View]
If you're anxious to get Mr. Roby's little sample to compile and run, let me give you a little nudge.
Getting()
{
/);
}
- Re: This made me install the dev tools
2003-07-23 22:17:35 anonymous2 [View]
Presuming somebody interested in this tutorial is going to be working on a Mac, why would they bust out vi or emacs or pico?
You can do all your typing in Project Builder. It's a perfectly servicable text editor. Or use BBEdit / BBEdit Lite. Much friendlier.
- Re: This made me install the dev tools
2003-07-23 21:07:56 anonymous2 [View]
misssing
return (0);
are we? :)
- Why not avoid ObjC?
2003-07-23 19:13:26 anonymous2 [View]
Java, AppleScript(gag), and now python can be used to create cocoa apps. I think there is a ruby bridge as well.
I haven't done anything more than the examples, but pyobjc seems to work very well.
- Why not avoid ObjC?
2003-07-23 21:18:30 tallama [View]
Hi, this is Seth Roby..
- Great
2003-07-23 17:13:23 anonymous2 [View]
Great work. Please give me more. This is just what I have been looking for.
- C/Obj-C/and blasted OO
2003-07-23 14:58:00 anonymous2 [View]
I agree with your first paragraph very much. Though I have been using C for several years and still hit a wall. I simply loath OO programming. Though ObjC.pdf on the Mac Dev site has helped a bit for learning OO particularly with ObjC..
- Re: C/Obj-C/and blasted OO
2003-08-01 15:29:40 halliday [View]
You ask for "2.) A good, C->Obj-C tutorial." Does this have something to do with your statement about how you "simply loath OO programming?"
When]?)
- C/Obj-C/and blasted OO
2003-07-24 01:46:29 anonymous2 [View]
"Is it possible to do this all from an editor like emacs?"
If you mean how to programmically build nib files I know you can. If you look into nib files they are just XML, and you should be able to find info on that somewhere.
Nib = next interface builder
- C/Obj-C/and blasted OO
2003-07-23 15:29:30 anonymous2 [View]
"Is it possible to do this all from an editor like emacs?"
Sure. ;-)
- THANK YOU!
2003-07-23 14:56:21 anonymous2 [View]
This is _exactly_ what I've been looking for.
You have a comfortable place to sleep and dinner anytime you're in Santa Barbara!
- Recommended Book for C Programmers
2003-07-23 14:12:07 cothomps [View]
If you are a beginner at C Programming, one of the best books out there is actually an O'Reilly book:.
- For the impatient...
2003-07-23 13:52:40 anonymous2 [View]
...I'd recommend picking up a copy of the canonical C book, "The C Programming Language" by Kernigan and Ritchie (published by Addison-Wesley, but hopefully O'Reilly won't be too upset about me mentioning it here!). It's very small, yet gives you absolutely everything you need to know (and more!) as a foundation for Objective-C.
- For the impatient...
2003-07-23 15:08:17 anonymous2 .
- Good but impractical
2003-07-23 13:14:31 anonymous2 [View]
I am happy to see articles on Cocoa programming for programmers at any level of expertise. Good job! I know people have day jobs that don't involve programming and nevertheless want to learn Cocoa. I think that is great!.
- Good but impractical
2003-07-23 16:00:11 anonymous2 [View]
I disagree that attempting serious use of Cocoa before completely learning C is bad. However, I completely agree that the importance of learning C needs more emphasis everywhere in the Cocoa world. It's often sold as being some magical new kingdom unto itself where you can just "get it" and make things happen. You and I both know it doesn't work like that. I don't think your concerns are misplaced, but I think this series is an excellent start to move aspiring Cocoa programmers from nothing to something and maybe entice them to learn more about this craft.
- just what I was looking for...
2003-07-23 12:18:28 anonymous2 [View]
..."exactly how much C do I need for cocoa" is a question I've been asking for a while now. big question is, what's the schedual for this series? I'd be hopeing a couple a week if all the articles are paced as this one is. (That being said, it looks like a great start)...
- just what I was looking for...
2003-07-23 15:42:47 anonymous2 [View]
"exactly how much C do I need for cocoa" answer: Exactly all of it. Seriously, objective C is not another language, it's a superset of C. It ADDS object oriented features to C. Objective C is not a redefinition of C, it IS C with some new features. IOW, you need to know C. C, C, C, C, C!!!! Si! I mean yes! No good shortcuts to this one I'm afraid. That said, there ARE powerful things you can do with Cocoa knowing only a limited amount of C and it's Obj C addendum. Learn a lot of C, it's not all that hard.
- just what I was looking for...
2003-08-01 16:41:23 anonymous2 [View]
So C is procedural? I was always under the impression that it was OO......
- just what I was looking for...
2003-07-24 01:59:28 anonymous2 [View]
If you are new to the C set of languages, and you want to learn to do something cool, you don't need to be a master at C. I agree that in the long run, having a good understanding of C will be required, but everyone wants to jump in and start writing programs that they are familiar with, with windows and menus, not just a command line tool that prints "Hello World".
People.
- Thanks!
2003-07-23 10:46:08 anonymous2 [View]
As a beginner with no lower level programming experience, this series is shaping up to be absolutely perfect for me. Having used Applescript Studio for some time now, I felt eager to move to Cocoa, but was reluctant to teach myself C because I could not foresee using it frequently enough to become comfortable with it quickly (can't give up the day job). This feels like the right pace and approach - please keep 'em coming!
- Good idea... but...
2003-07-23 10:21:46 arkham999 [View]
I think this is a really useful idea. However, at this pace it could take months to get to the point of a simple GUI Cocoa app that does anything consequential.
Maybe when you get to that point, you could offer the articles together in PDF format or something, rather than having to read the articles in distinct sections.
- Good idea... but...
2003-07-23 17:29:33 tallama [View]
Hello, this is the author speaking.
The.
- Excellent!
2003-07-23 08:00:47 plumcreek [View]
Finally! A series that teaches Cocoa without assuming a bajillion years of C experience.
Thank you!
- A well-written start...
2003-07-22 21:16:54 anonymous2 [View]
Were I a beginner, this is the kind of tutorial to look for. You explain things well and I think your column, should you choose to continue, will be a boon to those with no previous C knowledge and an excellent starting point for Mike Beam's articles.
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.
MMA7260Q and MMA8451Q
I’m using a my Processor Expert driver for the Freescale MMA7260Q accelerometer for multiple years in multiple projects. That MMA7260Q is present on many Freescale evaluation boards, including many of the Tower Boards. The MMA7260Q is an accelerometer with an analog interface, and the driver I have created for it is available on GitHub.
So when I was thinking to extend the MMA8451Q driver, I wanted to have the connection to be compatible as much as possible. That way I easily can switch my existing software to the MMA8451Q. The MMA8451Q has a nice digital I2C interface, with a lot of cool features (tap detection, orientation detection) I consider to use.
MMA8451Q Properties
The component properties have been extended with calibration values and Shell support:
💡 The MMA8451Q is factory calibrated, and has the ability to store calibration values on the device. Right now I store the calibration values in the driver, and not on the device yet.
The optional Shell interface is something I recently have added to the MMA7260Q too: it allows me to inspect/configure the device. More about this later in this post.
💡 I continue to add a command line (Shell) interface to my components, as feedback has been that this is very useful. And I’m using it all the time too: it allows me to work with a device using a command line interface. And with the modular way of Processor Expert components I can enable/disable it on a component by component base.
MMA8451Q Methods
The following picture shows the currently implemented interface:
The
ParseCommand() method is only enabled if the Shell is enabled in the component properties. This is done in the component .CHG (Change) script:
%ifndef Shell %set ParseCommand Selection never %else %set ParseCommand Selection always %endif
I2C
To simplify the communication with I2C to the device, two more methods (
WriteByteAddress8() and
ReadByteAddress8()) have been added to the GenericI2C component. This makes e.g. the driver method to enable the accelerometer really easy:
byte %'ModuleName'%.%Enable(void) { uint8_t val, res; res = inherited.I2C.ReadByteAddress8(MMA8451_I2C_ADDR, MMA8451_CTRL_REG_1, &val); if (res!=ERR_OK) { return res; } val |= MMA8451_ACTIVE_BIT_MASK; /* enable device */ return inherited.I2C.WriteByteAddress8(MMA8451_I2C_ADDR, MMA8451_CTRL_REG_1, val); }
Little Or Big Endian
One thing (again!) I was running into was that the Kinetis/ARM is Little Endian, while my brain is thinking (always? most of the time?) in Big Endian mode :-(. As I want the driver to work both with LE (Little Endian) and BE (Big Endian) cores, I created a macro to the driver code to deal with both worlds:
%if (CPUfamily = "Kinetis") #define %'ModuleName'_CPU_IS_LITTLE_ENDIAN 1 /* Cpu is little endian */ %else #define %'ModuleName'_CPU_IS_LITTLE_ENDIAN 0 /* Cpu is big endian */ %endif
❓ Note sure if there is a better way in Processor Expert CDE to know if the CPU is BE or LE?
Then I can use this in my driver code like this:
%-************************************************************************************************************ %-BW_METHOD_BEGIN MeasureGetRawX %ifdef MeasureGetRawX %define! RetVal %include Common\MMA8451QMeasureGetRawX.Inc word %'ModuleName'%.%MeasureGetRawX(void) { union { uint8_t buf[2]; /* value from device is in big endian */ uint16_t be; } val; static const uint8_t addr = MMA8451_OUT_X_MSB; if(inherited.I2C.ReadAddress(MMA8451_I2C_ADDR, (uint8_t*)&addr, sizeof(addr), &val.buf[0], sizeof(val.buf))!=ERR_OK) { return 0; /* failure */ } #if %'ModuleName'_CPU_IS_LITTLE_ENDIAN return (uint16_t)((val.buf[0]<<8)|val.buf[1]); /* transform into LE value */ #else return val.be; /* already in BE */ #endif } %endif %- MeasureGetRawX %-BW_METHOD_END MeasureGetRawX
Shell Interface
The Shell interface offers following commands:
With the status command I get the following information:
- raw: the raw (14bit, left shifted) values, both in hexdecimal and signed decimal
- calibOffset: the calibration offsets (as defined in the component properties or set by the calibration methods).
- calib 1g: The value the device uses for 1 g acceleration.
- GetX, Y, Z: the values returned by the
GetX(),
GetY()and
GetZ()methods. These values are compensated with the calibration values
- mg X, Y, Z: the values returned by
GetXmg(),
GetYmg()and
GetZmg(), in milli-g
As I have added the I2CSpy component as a bonus to my project, it allows me to read/write/dump the I2C memory map of the accelerometer:
💡 Using the I2CSpy I can explore the device settings without the need to download/write special code: I can inspect the bits and settings, write to the device and immediately see the impact. Really cool (at least I think this :-))
Sources
As always, things are available on GitHub. This link points to the driver code.
Summary and Outlook
The new Processor Expert driver works very well for me. It does not cover all the features of the device yet (tap detection, low power modes, orientation detection, different g sensitivity levels). So there is still a lot of room for extensions, and this will be added as soon as I find the time :-). But for now, I think it is a good starting point.
Happy Accelerating 🙂
Can you give me the link to the component.
Please.
The link to it is at the end of the post, under ‘Sources’. The ‘beans’ folder is here:
See this link how you can import the component(s):
I’m a fan of yours since I’ve started playing with freedom board a couple weeks ago. I’m following along with this article and start noticing when I enable the MMA8451Q; It only allow a selection to create new component with Shell. But I’ve already used FSShell with other components up to now. And I’d really like to access the MMA8451Q with all the above command lines with FSShell. Any suggestion ? Thank you for a great library.
Hi,
I had to redesign the FSShell, as it had too much lumped into it. The shell part is now in the ‘Shell’ component, while now FatFS has an interface to it. What I suggest is:
a) disable the FSShell (so you have it as backup)
b) Add the Shell component. You can link it to your serial interface (e.g. Asynchroserial)
c) link accelerometer/FatFS/FreeRTOS or whatever you have to the new Shell
Should be fairly easy. Otherwise let me know.
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Hi. It’s possible to use this with the MMA8452 accelerometer? Thanks!
Hi Juan,
I did a quick data sheet comparison, and it looks the MMA8452 has only different number of A/D bits, and everything else is the same. So you should be able to use the driver with it. Same for the MMA8453.
Hi Erich, I´m using MMA8453QR1 in a custom board of mine and I´d like to know where I can change the resolution (14 to 10 bits from MMA8451 bean) to port this project? Another question is: what is the full-scale value range? Is it set to 8g?
Hi Marcio,
you would have to use the accelerometer with SetFastMode(FALSE). Setting the ScaleRange requires that the sensor is disabled.
I have now extended the component with methods to set and get the range (GetScaleRangeG() and SetScaleRangeG()). Or you could use the following code below:
uint8_t MMA1_GetScaleRangeG(uint8_t *gScale)
{
uint8_t val, res;
res = GI2C1_ReadByteAddress8(MMA1_I2C_ADDR, MMA1_XYZ_DATA_CFG, &val);
if (res!=ERR_OK) {
return res;
}
switch(val&0x3) { /* check FS1 and FS2 bits */
case 0: *gScale = 2; /* 00: 2g */
return ERR_OK;
case 1: *gScale = 4; /* 01: 4g */
return ERR_OK;
case 2: *gScale = 8; /* 10: 8g */
return ERR_OK;
default: break;
} /* switch */
*gScale = 0; /* error case */
return ERR_RANGE;
}
There is an updated component available on SourceForge too: and an example project using it is on
I hope this helps?
Erich
Right now I´m getting a ERR_BUSY code when I try to use SetFastMode(FALSE) method. I do that right after I call MMA1_Init() with no error, so unfortunately I couldn´t test GetScaleRangeG() yet : (
Did you faced this problem before or have some tip to help me to solve it?
I have found that the accelerometer after writing some settings, needs some delay time (because the sensor is busy storing the settings?).
Try to add a delay after the MMA1_Init(), e.g. with
WAIT1_Waitms(10);
In fact, even in the FRDM-KL25Z board I`m getting this ERR_BUSY error and I don´t know why.
With the project I have posted on GitHub, or your own version of it?
ERR_BUSY means that the device does not respond with an ACK when the driver wants to talk to it.
It happens with your project too, but it seems to work properly when I turn off and then turn on the board again (FRDM-KL25Z or my board).
Hi Marcio,
yes, I noticed that as well: if the accelerometer somehow internally is screwed up, it only can be brougth back with a power cycle. That’s why in my designs I usually add a FET to the Vcc/supply pin of the accelerometer so the microcontroller can reset it.
Ok Erich. I´d like to use the shell to test the commands, but I´m little confused here: When I enable it on MMA8451Q component I need to choose one default serial, which one? Why I can use the FreeMaster bean that is already on project?
Hi Marcio,
I have added shell support to the example on GitHub (), so you can use that as an example how to use it. That example uses the OpenSDA serial connection.
I hope this helps,
Erich
Oh, it´s true! I have forgot this step, sorry about that. I already make this changes and now it´s working, thanks Erich!
The only problem now it´s about the strange axis values I´m reading here when I´m doing the calibration.
Doing my tests I found some weird (errors?) here: right after calling MMA1_SetFastMode(FALSE) I used MMA1_CalibrateX1g() method and I found that in fact this function is switched with MMA1_CalibrateY1g(), in other words the X and Y axis are inverted and for MMA1_CalibrateZ1g() method positioning the FRDM-KL25Z in horizontal position I got a 0g and turning it up side down I found -2g (near 8192 in decimal). Did you find the same result at your side? Obs: The scale range for your project came with 2g.
Hi Erich,
Another issue I´m facing here is that it seems I can´t change the scale range using MMA1_SetScaleRangeG method. It was set to 2g and until now I couldn´t change it to 4g or 8g, even with no error codes. I used this code below:
uint8_t res=ERR_OK, ret, scale;
res = MMA1_Init();
WAIT1_Waitms(10);
res = MMA1_SetFastMode(FALSE);
WAIT1_Waitms(10);
ret = MMA1_SetScaleRangeG(8);
And then I used this code to read the scale range:
res = MMA1_Init();
WAIT1_Waitms(10);
// res = MMA1_SetFastMode(FALSE);
// WAIT1_Waitms(10);
ret = MMA1_GetScaleRangeG(&scale);
Using MMA1_SetFastMode(FALSE) or not doesn´t make difference here and when I call MMA1_GetScaleRangeG, I allways read scale equals to 2. Did you find the same problem there?
Hi Marcio,
as noted earlier (and in the documentation of the component too) you have to disable the sensor if you want to do change the settings.
So have you called MMA1_Disable() first?
Hi Marcio,
as noted in the comments of these functions, you have to place the board with that respective axis in a 1g position. So if you do the Z calibration, you have to put the board flat (the sensor is exposed 1g). In a smilar way, you have to change the board orientation if you do the other calibration functions.
I hope this helps,
Erich
Yes, that is correct Erich. I just would like to know if you have tested there this calibrations and got the same results or behavior I´m got here at my side.
Below is the output of my calibration, and that looks ok to me?
------------------------
FRDM-KL25Z Accel
------------------------
Device is enabled, disable it before applying settings...
Setting G mode to 2 g.
Enable device.
X axis calibration (1g for X): place the board with the USB connector pointing to the sky and press a key...
Y axis calibration (1g for Y): place the board with the right arduino rows down and press a key...
Z axis calibration (1g for Z): place the board flat on a table and press a key...
done!
x: -11 y: -11, z: 3969
x: 17 y: 21, z: 4005
x: 21 y: 3, z: 3995
x: 19 y: -7, z: 4007
x: 21 y: 17, z: 4007
x: 19 y: 29, z: 4021
x: 29 y: 13, z: 4019
x: 25 y: 15, z: 4003
x: 19 y: 13, z: 3995
x: 39 y: -1, z: 4003
x: -3 y: -7, z: 4017
x: 9 y: 21, z: 4017
x: 15 y: 9, z: 4003
x: 23 y: -1, z: 4021
x: 17 y: -1, z: 4027
x: 15 y: 25, z: 4051
x: 21 y: 25, z: 4025
x: 23 y: 13, z: 4003
x: 33 y: 13, z: 4043
For 2g I think is correct. Are you using Shell? Can you please tell me how to set it on this project to do this tests either?
Yes, it is using the shell. See
Hello Erich,
Thanks for great posts on pretty much a huge number of topics….
I tried to use the component with the Shell interface but I do not understand
which API should be called regularly to parse commands entered in the termite shell…
I did not find any example code using the extended driver (with non OS)…
Could you please give me a hint ?
Thanks
Vince
Hi Vince,
Just put the code from the Shell task into a loop:
static void ShellLoop(void) {
unsigned char buf[48];
buf[0] = ”;
(void);
LEDG_Neg();
}
}
instead of its own loop, call it from your main() loop. There is really nothing special with or without an RTOS.
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Sorry for posting on an old topic however I’m struggling with the GenericI2C component in Kinetis Design Studio 3.0.0.
I’m trying to adapt this code to work for an LSM9DS0 combined acc, mag and gyro device however I’m having difficulty when trying to do multi-byte reads. As an example, reading the 3×16 bit accelerometer values:
static const uint8_t addr = LSM9DS0_REG_OUT_X_L_A;
int16_t xyz[3];
GI2C1_ReadAddress(LSM9DS0_ADDR_XM, (uint8_t*)&addr, sizeof(addr), (uint8_t*)xyz, 6);
When inspecting the “xyz” array, each element has the same value. The value is different each time the ReadAddress function is called but still the value in each array element is identical.
Am I using this ReadAddress function incorrectly?
Thanks in advance,
Kevin
Hi Kevin,
your usage looks ok. I think you have a different problem down the wire. Could you use a logic analyzer or scope to check what is sent and received over SCL and SDA and matches what your LSM9DS0 needs? It might be that there is something wrong.
I hope this helps,
Erich
Hi Erich,
Thank you for your quick reply.
I haven’t used a logic analyzer as of yet as the WHO_AM_I and single-byte reads all seem to work correctly – returning the expected values.
I shall investigate with a logic analyzer later this evening.
Kind regards,
Kevin
Hi Erich,
I’ve been working on FRDM kl25z to interface MMA8451q via I2C0.
My code is something like this
As soon as I initialize the I2C0, I’m read WHO_AM_I continuously with 3 seconds delay, but after 1st read, SCL is pulled low forever. SDA seems to be fine.
What might be the possible problem? Can you please suggest something which I can try?
Regards,
Bharath
Hi Bharath,
can you try the code I have used in that post instead? There are so many things which could go wrong with your code example. What you could try is to do single stepping through your code while watching with a logic analyzer the SDA and SCL line. I hope this helps, good luck!
Hi Erich,
Yes I’ve tried stepping through the code and the controller wasn’t able to generate the STOP condition hence the SCL remained low. I used the different frdm kl25z board, and things started working. I believe the board I was using has some problem. Thank you for your input.
Regards,
Bharath
Erich
If I want to use the (GetXmg, GetYmg, GetZmg) and send those values to freemaster I have to change those three lines in “Appliction.c”:
#if USE_PEX_COMPONENT
xyz[0] = MMA1_GetX()>>8; to xyz[0] = MMA1_GetXmg()>>8;
xyz[1] = MMA1_GetY()>>8; to xyz[1] = MMA1_GetYmg()>>8;
xyz[2] = MMA1_GetZ()>>8; to xyz[2] = MMA1_GetZmg()>>8;
or do I have to do something more?
That depends what values you want to show? The shift by 8 is simply to only send the MSBits, but that’s up to you.
Hi,
I have used the Generic I2C Component and Accelerometer code downloaded from GitHub for making the LEDs blink according to tilt. This is my main() program.
/*for(;;)
{
LED1_On();
LED2_On();
LED3_On();
res = MMA1_Init();
while (res==ERR_OK) {
res = MMA1_GetRaw8XYZ(&xyz[0]);
LED1_Put(xyz[0]>50);
LED2_Put(xyz[1]>50);
LED3_Put(xyz[2]>50);
}
LED1_Off();
LED2_Off();
LED3_Off();
}*/
I am not sure if I need to include other methods on that are available on the accelerometer driver like the writereg8/readreg8 etc. In a previous tutorial where you built separate events for the accelerometer you had used such methods. I would like to get some pointers with regard to that.
The GenericI2C driver is a wrapper to deal with different I2C driver implementations (LDD, non-LDD, bitbanging, etc). Your posted example make sense, and you should not need any other functions. The writereg8/readreg8 methods are there for you to read/write registers directly in case you need them.
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It can feel daunting to build a new microservice. It feels like there are a lot of things to keep in mind. Fortunately, Spring has a variety of libraries that can get us started quickly. We can focus on the bits that matter to us and let Spring scaffold the rest. In this post, we’re going to take a look at what makes microservices different from other types of applications and how Spring helps us get up and running fast.
What Do We Mean by “Microservice”?
So, what exactly do we mean when we talk about microservices? They have their origins in a very specific type of service. It’s not just any deployment artifact. In Martin Fowler’s article about microservices, he mentions a few key characteristics that separate microservices from just another deployed app:
- Componentization via services.
- Organized around business capabilities.
- Products, not projects.
- Decentralized data management.
- Design for failure.
We’re going to take a look at which Spring libraries help us achieve these characteristics. But before that, let’s talk about how we can easily set up a new microservice with any set of libraries.
Spring Initializr, Our Launchpad
You’re about to find out just how overwhelming the amount of Spring libraries that exist for building microservices is. Fortunately, there are two great tools to help us in our path. The first is Spring Initializr. This little site will get you up and running with a new Spring project in minutes, along with all the components you want to use.
The second tool is the website Baeldung, which is chock-full of in-depth Spring tutorials on all of the libraries we’ll be using. You can use this site to dive deeper to any library for interest. They also have open-source code examples for their tutorials, from which we will be borrowing.
Now, onto the libraries.
Componentization Via Services
Componentizing into services is the idea that a microservice is independently deployable and runnable. In this vein, let’s look at libraries that help us start up our application.
Spring Boot
Let’s start with the foundation of everything: Spring Boot. This library is the basis of almost every other Spring library out there. Spring Boot sets up our application context, wiring up all our software components It also makes it really easy to execute our JAR—our software package—as a console application.
To include Spring Boot in your project, use Spring Initializr or add the following:
buildscript { ext { //This is the most recent version at the time of writing. springBootVersion = '2.1.1.RELEASE' } dependencies { //This makes the jar executable. classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}") } } ... apply plugin: 'org.springframework.boot' //This makes it easier to manage the correct versions of the Spring libraries. The bill of materials ensures the versions are compatible with each other. apply plugin: 'io.spring.dependency-management' ... repositories { mavenCentral() //Some of the libraries we discuss are stored in the milestones repository. maven { url " } } ... dependencies { //This let's our code sping up a Spring ApplicationContext in our Main method implementation('org.springframework.boot:spring-boot-starter') //This gives us some unit testing utilities and runners testImplementation('org.springframework.boot:spring-boot-starter-test') } ... dependencyManagement { imports { //This is the actual bill of materials for spring dependencies mavenBom "org.springframework.cloud:spring-cloud-dependencies:${springCloudVersion}" } }
For the examples in this post, I’ll be using Gradle for dependency management, but you can also use Maven. Spring Initializr supports both.
With our dependencies in place, our application main method can look like this:
@SpringBootApplication public class Application { public static void main(String[] args) { SpringApplication.run(Application.class, args); } }
And that’s all you need to get started! Note, however, that there’s a lot more functionality built into Spring Boot than this; explore it at your leisure.
Organized Around Business Capabilities
Microservices should be aligned only with business concepts like ordering, fulfillment, shipping, and customer service. They shouldn’t be centered around concepts like data access, authentication, or email. Spring doesn’t directly help with figuring out proper business boundaries. In fact, this is probably one of the hardest aspects of creating healthy microservices, and it’s out of scope for this article. However, once you figure out your boundaries, Spring provides some libraries that will let you expose this functionality to your customers.
Web
Spring Web is a classic library that allows us to serve up both web pages and HTTP endpoints to our users. It also spins up an embedded Tomcat web server and binds to a port, so we can talk to the wider world.
The web dependency will look like this:
dependencies { //This can replace the "spring-boot-starter" dependency from above. implementation('org.springframework.boot:spring-boot-starter-web') ... }
With that in place, we can build HTTP endpoints:
@Controller public class SimpleController { @GetMapping("api/hello") public String homePage() { return "hello"; } }
If I GET /hello with curl or Postman, I’ll see a response with “hello” as the only content.
There are loads more capabilities with Spring Boot Web. What I have shown here just barely scratches the surface. You’ll have the ability to add security, deal with exceptions, add request/response middleware, and much more. Try out some tutorials on it.
Alternatives
Spring has a newer variant of building web apps called Spring WebFlux. This variant aims to be more reactive and to more easily support asynchronous, scalable operations.
Products, Not Projects
Products over projects is the spirit of DevOps. You build it, you run it. You can’t just deploy a microservice into the ether—you have to monitor it and maintain it. Spring has a couple of libraries that can help us not only build but also run our microservices.
Actuator
Spring Actuator is a powerful library that gives us production-monitoring capabilities for our microservices out of the box with little effort. It provides various endpoints that give insight into the health and status of your service.
You set it up like so:
dependencies { implementation('org.springframework.boot:spring-boot-starter-actuator') ... }
By default, only the /actuator/info and /health endpoints are enabled. You can enable all endpoints in your property file with:
management.endpoints.web.exposure.include=*
There are many endpoints in Actuator, and I recommend exploring them all. You can also see them through the /actuator endpoint. My favorite is /actuator/metrics. Its response looks something like this:
{ "names" : [ "jvm.memory.max", "jvm.memory.used", "jvm.memory.committed", "jvm.buffer.memory.used", "jvm.buffer.count", "jvm.buffer.total.capacity" ] }
If you drill into a specific one, such as /actuator/metrics/jvm.memory.max, you can see something like this:
{ "name" : "jvm.memory.max", "description" : "The maximum amount of memory in bytes that can be used for memory management", "baseUnit" : "bytes", "measurements" : [ { "statistic" : "VALUE", "value" : 2.384986111E9 } ], "availableTags" : [ { "tag" : "area", "values" : [ "heap", "nonheap" ] }, { "tag" : "id", "values" : [ "Compressed Class Space", "PS Survivor Space", "PS Old Gen", "Metaspace", "PS Eden Space", "Code Cache" ] } ] }
This immediately gives you a level of insight into your latency, error rates, and so on. You can also customize existing or new actuator endpoints as you desire.
Sleuth
It’s highly likely that our microservices aren’t running in isolation. At the end of the day, they have to communicate with queues, databases, and even other microservices to do their job fully. When things go wrong, it can be hard to track all the work that has happened in a request. If I want to be able to quickly debug issues across multiple deployed services, I need some tooling. Spring Sleuth lets us trace these requests across microservice boundaries. It can even let us trace to database calls.
We add it like so:
dependencies { implementation('org.springframework.cloud:spring-cloud-starter-sleuth') ... }
After this, we technically don’t need to wire up any more code. It works with other Spring libraries to add tracing context when calling other services and databases. You can see this context when you log:
2018-01-10 22:36:38.254 INFO [Microservice Starter,4e30f7340b3fb631,4e30f7340b3fb631,false] 12516 --- [nio-8080-exec-1] c.b.spring.session.SleuthController : Hello Sleuth
The first GUID is the trace ID, which is the same across the request. The next GUID is the span ID, which represents the current unit of work. Having this context lets us query and group our log messages in a way that lets us see the life cycle of a request. You can also report these traces to external storage, but that is outside the scope of this article. Read this article by Baeldung for more information.
Decentralized Data Management
A microservice should own its data through and through and have minimal coupling to another service’s data. No one else should be able to access its data directly.
JPA With SQL Server
Spring makes it easy for a microservice to own its own data for multiple data stores. Using the Spring JPA library lets us use Hibernate and the JPA specification to interact with a relational database like SQL Server.
You can wire it up like this:
dependencies { implementation('org.springframework.boot:spring-boot-starter-data-jpa') runtimeOnly('com.microsoft.sqlserver:mssql-jdbc') ... }
You then enable it in your application or an @Configuration:
@EnableJpaRepositories("org.scalyr.persistence.repo") @EntityScan("org.scalyr.persistence.model") @SpringBootApplication public class Application { ... }
Then we can map our classes to database tables:
@Entity public class Book { @Id @GeneratedValue(strategy = GenerationType.AUTO) private long id; @Column(nullable = false, unique = true) private String title; @Column(nullable = false) private String author; }
and use Spring repositories to work with the data:
public interface BookRepository extends CrudRepository<Book, Long> { List<Book> findByTitle(String title); }
For more information, check out this tutorial.
Cloud Stream With Rabbit
Decentralizing data is a powerful way to keep microservices autonomous, but it’s inevitable that some of this data will need to be shared across services. We don’t want to share our databases, and we want to avoid runtime coupling on other services when possible. After all, we can’t count on those services always being up and running. We can have our cake and eat it, too, by sharing data through event-driven messaging. Spring Cloud Stream with RabbitMQ makes this relatively easy to do.
We can add the dependencies as so:
dependencies { implementation('org.springframework.cloud:spring-cloud-starter-stream-rabbit') testImplementation('org.springframework.cloud:spring-cloud-stream-test-support') }
Then we can publish and subscribe to messages through Rabbit queues in our application:
())); } }
INPUT and OUTPUT are built-in channels that let us specify from where we subscribe to messages and to where we publish them. We need to bind Rabbit to these channels:
spring: cloud: stream: bindings: input: destination: queue.log.messages binder: local_rabbit group: logMessageConsumers output: destination: queue.pretty.log.messages binder: local_rabbit binders: local_rabbit: type: rabbit environment: spring: rabbitmq: host: localhost port: 5672 username: guest password: guest virtual-host: / server: port: 0 management: health: binders: enabled: true
The application code remains blissfully ignorant of the specific transportation being used to publish or receive messages—we push all of that to the above configuration. You can see that we bound the INPUT and OUTPUT channels to specific exchanges in Rabbit. These exchanges and queues are automatically declared for us by the Cloud Stream Rabbit library. For more information, check out this article.
Alternatives
Spring also has support for NoSQL databases, like MongoDB. Spring supports just about any popular persistence mechanism. If using Cloud Stream support, we can use Kafka instead of RabbitMQ.
Design for Failure
When dealing with distributed, autonomous services, we can’t count on them being up at all times. When communicating with other services, we should be ready to handle the inevitable.
Hystrix
Netflix built a library called Hystrix that lets us apply the circuit breaker pattern when communicating with other services. Using circuit breakers when communicating externally gives us a measure of resiliency to system outages. We can fall back to a default behavior when the service with which we want to communicate is unavailable.
The dependency is:
dependencies { implementation('org.springframework.cloud:spring-cloud-starter-netflix-hystrix') }
The configuration is dead simple:
); }
You can see that if the repository call fails, we can use a cached version. Feel free to read more here.
Retry
In many cases, circuit breaking may be a bit of overkill. Often we have intermittent network failures that we can overcome with a simple retry. Enter Spring Retry.
We add it to our Gradle build with:
dependencies { implementation('org.springframework.retry:spring-retry')) ... }
We then enable it via:
@Configuration @EnableRetry public class AppConfig { ... }
And we implement it with:
@Service public interface MyService { @Retryable( value = { SQLException.class }, maxAttempts = 2, backoff = @Backoff(delay = 5000)) void retryService(String sql) throws SQLException; ... }
This says, “Please retry ‘retryService’ up to two times if you see an SQLException, and wait 5,000 ms between each retry.”
… And Many More
As you can see, Spring provides a myriad of libraries we can use to get a large boost into building microservices. We have much of what we need, from providing APIs to accessing data and even monitoring our application once it’s in production. There are many more libraries you can use for more advanced use cases, so go out and explore using Spring for your own microservices.
Want to read more about Spring? We covered it in our “getting started quickly with logging” series, so head there next! | https://www.sentinelone.com/blog/spring-boot-microservices/ | CC-MAIN-2022-21 | refinedweb | 2,242 | 56.66 |
10 November 2009 15:10 [Source: ICIS news]
BERLIN (ICIS news)--Bioplastics companies will grow 30% or more per year after the global economy exits the recession, an industry expert said on Tuesday.
Rates of growth of between 30% and 60% a year would be similar to those achieved over the past five years, Andy Sweetman, global marketing manager of sustainable technologies at packaging films group Innovia Films said at the 4th European bioplastics conference in ?xml:namespace>
“Even throughout the recession if you speak to most people in the bioplastics industry they will say they are still growing,” Sweetman said.
“I think we will see there would have been a slowing in 2008 and 2009. Companies will probably see only 10% growth this year. However, it is still a double digit growth rate. I think the industry will accelerate and we will see those 30% plus growth rates again.
“In the packaging market there are a lot of brand owners realising they have to start looking at waste and raw material issues. I think they are using the recession as a breathing space to learn about the subject, make themselves ready and pick the right product, and launch in the next year or so,” he added.
Sweetman said that the biggest driver for the industry initially was that consumers liked things to be biodegradable and compostable and that the bioplastics market had been driven as a waste management idea, particularly in
“We are going to get to a point where instead of food and garden waste being seen as a problem they will be seen as an asset, which completely changes businesses ways of thinking. For this waste to be taken somewhere to be digested anaerobically and turned into an energy or fertilizer source there will be a need for an infrastructure and that is where biomaterials will come in,” Sweet | http://www.icis.com/Articles/2009/11/10/9262518/bioplastics-firms-to-grow-at-30-or-more-a-year-after-recession.html | CC-MAIN-2014-52 | refinedweb | 312 | 59.87 |
. Overview
In this article, we will cover some multimedia and graphic aspects in Android. The Android SDK provides a set of APIs to handle multimedia files, such as audio, video and images. Moreover, the SDK provides other API sets that help developers to implement interesting graphics effects, like animations and so on.
The modern smart phones and tablets have an increasing storage capacity so that we can store music files, video files, images etc. Not only the storage capacity is important, but also the high definition camera makes it possible to take impressive photos. In this context, the Multimedia API plays an important role.
2. Multimedia API
Android supports a wide list of audio, video and image formats. You can give a look here to have an idea; just to name a few formats supported:
Audio
- MP3
- MIDI
- Vorbis (es: mkv)
Video
- H.263
- MPEG-4 SP
Images
- JPEG
- GIF
- PNG
Android, moreover, can handle local files, meaning files that are stored inside the smart phone or tablet or remote file using data streaming. We can leverage these capabilities in order to build very interesting apps.
All the classes provided by the Android SDK that we can use to add multimedia capabilities to our apps are under the
android.media package. In this package, the heart class is called
MediaPlayer. This class has several methods that we can use to play audio and video file stored in our device or streamed from a remote server.
This class implements a state machine with well-defined states and we have to know them before playing a file. Simplifying the state diagram, as shown in the official documentation, we can define these macro-states:
- Idle state: When we create a new instance of the MediaPlayer class.
- Initialization state: This state is triggered when we use
setDataSourceto set the information source that
MediaPlayerhas to use.
- Prepared state: In this state, the preparation work is completed. We can enter in this state calling
preparemethod or
prepareAsync. In the first case after the method returns the state moves to
Prepared. In the async way, we have to implement a listener to be notified when the system is ready and the state moves to
Prepared. We have to keep in mind that when calling the
preparemethod, the entire app could hang before the method returns because the method can take a long time before it completes its work, especially when data is streamed from a remote server. We should avoid calling this method in the main thread because it might cause a ANR (Application Not Responding) problem. Once the
MediaPlayeris in prepared state we can play our file, pause it or stop it.
- Completed state: Te end of the stream is reached.
We can play a file in several ways:
// Raw audio file as resource MediaPlayer mp = MediaPlayer.create(this, R.raw.audio_file); // Local file MediaPlayer mp1 = MediaPlayer.create(this, Uri.parse("....")); // Remote file MediaPlayer mp2 = MediaPlayer.create(this, Uri.parse(""));
or we can use
setDataSource in this way:
MediaPlayer mp3 = new MediaPlayer(); mp3.setDataSource("");
Once we have created our
MediaPlayer we can “prepare” it:
mp3.prepare();
and finally we can play it:
mp3.start();
Please keep in mind the observations above regarding preparing the state. According to them, we can use an async operation so that we will not stop the main thread. In this case, we have:
// Remote file MediaPlayer mp2 = MediaPlayer.create(this, Uri.parse("")); mp2.setAudioStreamType(AudioManager.STREAM_MUSIC); mp2.setOnCompletionListener(new MediaPlayer.OnCompletionListener() { @Override public void onCompletion(MediaPlayer mp) { mp.start(); } }); mp2.prepareAsync();
We used a listener to be notified when the
MediaPlayer is in the prepared state so we can start playing. At the end, when we don’t need the instance of
MediaPlayer anymore, we should release it:
mp2.release();
2.1. Using Android Camera
If we want to add to our apps the capability to take photos using the integrated smart phone camera, then the best way is to use an
Intent. For example, let us suppose we want to start the camera as soon as we press a button and show the result in our app.
In the
onCreate method of our
Activity, we have to setup a listener of the
Button and when clicked to fire the intent:
Button b = (Button) findViewById(R.id.btn1); b.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // Here we fire the intent to start the camera Intent i = new Intent(MediaStore.ACTION_IMAGE_CAPTURE); startActivityForResult(i, 100); } });
In the
onActivityResult method, we retrieve the picture taken and show the result:
@Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { // This is called when we finish taking the photo Bitmap bmp = (Bitmap) data.getExtras().get("data"); iv.setImageBitmap(bmp); }
Running the app we have:
In the example above, we used an emulated camera.
3. Graphics
By now, we talked about standard components that we can be used in our UI. This is good but it is not enough when we want to develop a game or an app that requires graphic contents. Android SDK provides a set of API for drawing custom 2D and 3D graphics. When we write an app that requires graphics, we should consider how intensive the graphic usage is. In other words, there could be an app that uses quite static graphics without complex effects and there could be other app that uses intensive graphical effects like games.
According to this usage, there are different techniques we can adopt:
- Canvas and Drawable: In this case, we can extend the existing UI widgets so that we can customize their behavior or we can create custom 2D graphics using the standard method provided by the
Canvasclass.
- Hardware acceleration: We can use hardware acceleration when drawing with the
CanvasAPI. This is possible from Android 3.0.
- OpenGL: Android supports OpenGL natively using NDK. This technique is very useful when we have an app that uses intensively graphic contents (i.e games).
The easiest way to use 2D graphics is extending the
View class and overriding the
onDraw method. We can use this technique when we do not need a graphics intensive app.
In this case, we can use the
Canvas class to create 2D graphics. This class provides a set of method starting with
draw* that can be used to draw different shapes like:
- lines
- circle
- rectangle
- oval
- picture
- arc
For example let us suppose we want do draw a rectangle. We create a custom view and then we override
onDraw method. Here we draw the rectangle:
public class TestView extends View { public TestView(Context context) { super(context); } public TestView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); } public TestView(Context context, AttributeSet attrs) { super(context, attrs); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); Paint p = new Paint(); p.setColor(Color.GREEN); p.setStrokeWidth(1); p.setStyle(Paint.Style.STROKE); canvas.drawRect(5, 5, 120, 120, p); invalidate(); } }
As it is clear from the code above, in the
onDraw method, we used the
drawRect
Canvas method. Notice that we used another class called
Paint. This class specifies how the shape will be drawn; it specifies its color, if it has to be filled, the border width and so on.
In this case the layout looks like:
" > <com.swa.customview.TestView android: </RelativeLayout>
Running the app, we have:
Suppose we want to fill the rectangle with a gradient color, so the
onDraw method becomes:
protected void onDraw(Canvas canvas) { super.onDraw(canvas); Paint p = new Paint(); p.setColor(Color.GREEN); p.setStrokeWidth(1); p.setStyle(Paint.Style.FILL_AND_STROKE); LinearGradient lg = new LinearGradient(0F, 0F, 115F,115F, Color.GREEN, Color.YELLOW, TileMode.CLAMP); p.setShader(lg); canvas.drawRect(5, 5, 120, 120, p); invalidate(); }
Running the app we have:
As we told before, beginning from Android 3.0 (API 11), we can use hardware acceleration. In this case, if we want to use it, we have to modify the
Manifest.xml and add the following line:
<application android:
or we can use it at
Activity level.
4. Drawable
In Android, a
Drawable is a graphical object that can be shown on the screen. From API point of view all the
Drawable objects derive from
Drawable class. They have an important role in Android programming and we can use XML to create them. They differ from standard widgets because they are not interactive, meaning that they do not react to user touch.
Images, colors, shapes, objects that change their aspect according to their state, object that can be animated are all drawable objects. In Android under
res directory, there is a sub-dir reserved for
Drawable, it is called
res/drawable.
Under the
drawable dir we can add binary files like images or XML files.
As we saw in the previous articles, we can create several directories according to the screen density we want to support. These directories have a name like
drawable-<>.
This is very useful when we use images; in this case, we have to create several image versions: for example, we can create an image for the high dpi screen or another one for medium dpi screen. Once we have our file under
drawable directory, we can reference it, in our class, using
R.drawable.file_name. While it is very easy add a binary file to one of these directory, it is a matter of copy and paste, if we want to use a XML file we have to create it.
There are several types of drawable:
- Bitmap
- Nine-patch
- Layer list
- State list
- Level list
- Transition drawable
- Inset drawable
- Clip drawable
- Scale drawable
- Shape drawable
An interesting aspect is that we can create such elements using XML or directly from code. There is a correspondence between the elements shown above and the API class. We can add the
Drawable suffix and we create the corresponding class name: for example if the corresponding class of
Bitmap drawable is
BitmapDrawable and so on.
You can have a look here if you want to have more information. We will not cover all these objects in this article but only the most popular.
4.1. Shape drawable
This is a generic shape. Using XML we have to create a file with shape element as root. This element as an attribute called
android:shape where we define the type of shape like rectangle, oval, line and ring. We can customize the shape using child elements like:
Table 1
For example, let us suppose we want to create an oval with solid background color. We create a XML file called for example
oval.xml:
<shape xmlns: <solid android: <size android: </shape>
In this way, we create an oval shape having red as background color and with size 120dpx100dp. Then we can reference it in our layout file:
<ImageView android:
Running the app, we obtain:
For example, we can suppose we want to change the
Button widget look. We want to create a rectangle with rounded corners and as background a gradient color. We define a shape in XML file called
round_corner.xml and we add it to
drawable dir:
<shape xmlns: <stroke android: <gradient android: <corners android: <padding android: </shape>
and in the layout file we have:
<Button android:
Running the app, we have:
As we can see, just using XML we can modify the widget background or create shapes.
4.2. State list
This drawable object can display several drawables depending on the object state. It is very useful when we want to customize some object that has an internal states. For example, the
Button widget is one of these objects, it has several states: pressed, focused and so on.
In XML this drawable is represented by selector tag. This tag has item child elements:
<selector xmlns: <item android: <item android: </selector>
Let’s suppose we want to customize a
Button widget in our layout when it is pressed. Additionally, we want to change its background to a red gradient color. So the first thing we do is to define two shapes:
<shape xmlns: <solid android: </shape>
green.xml
<shape xmlns: <gradient android: </shape>
Once we have our shapes we can assign them to different object states:
<selector xmlns: <item android: <item android: </selector>
In this way, we assign the red_gradient drawable when the button is pressed and the green drawable in the default state. Running the app we have:
4.3. Nine-patch
Nine-patch image is a special background image that can be resized, so that it can hold the
View content. You can look here if you want to have more information. It can be used when we want to create an image but we do not know the exact size of the
View content.
Briefly, while creating this image we define the borders that can be stretched and the static area. Android provides a tool to help us creating this kind of images located under the tools directory. Suppose we want to create a
Button widget background, we can create an image like the one shown below:
Now we can run
draw9patch.bat under the tools directory. Now we can drag&drop this image on the window just opened:
The window is divided in two areas: the left one is the “working window” while on the right side we have the final result. Now we have to choose the area of the image that can scale, we can do it drawing lines on the left and top side, as you can see in the picture:
Now we set the content area, selecting the right and bottom side of the image.
We can see on the right side the final result. Now we can save our work. When we have finished, we can copy this image under
res/drawable of our Android project.
To see the final effect we can create a layout like the one shown below:
<Button android: <Button android:
In the first button we used a standard image the simple red box as shown above, while in the second button we use a
9-patch image.
Running the example we have:
You can notice the
9-patch images scales better than the standard image.
5. Download the Source Code
This was a lesson on how to use Multimedia with Android. You may download the source code here: | https://www.javacodegeeks.com/2015/09/android-ui-adding-multimedia-to-an-app.html | CC-MAIN-2020-16 | refinedweb | 2,383 | 61.06 |
Basically, I need to write a program that takes a user input for multiple text files, and then prints them out into one file.
I usually try not to pose questions here back to back, but alas, I need the help this time round. What really has me baffled is the start of the code I was given to work with. It has many lines that I'm not sure what the actual use is, or how I'm supposed to work with them.
Here is the code:
import java.io.IOException; import java.io.FileReader; import java.io.PrintWriter; import java.util.Scanner; /** * This program concatenates contents of several files into one file. */ public class CatFiles { public static void main(String[] args) throws IOException { Scanner in = new Scanner(System.in); int j = 0; boolean done = false; while(!done) { System.out.print("Enter input file: "); if(in.nextLine().toLowerCase().equals("q")) { System.out.print("Enter Destination file: "); String output = in.next(); PrintWriter writer = new PrintWriter(output); done = true; } else { String input = in.next(); } } if (args.length < 2) { System.out.println( "Usage: CatFiles sourcefile1 sourcefile2 . . . targetfile"); return; } String target = args[args.length - 1] ; for (int i = 0; i < args.length - 1; i++) { String source = args[i]; } } } | https://www.daniweb.com/programming/software-development/threads/132154/concactinating-multiple-text-files-into-one | CC-MAIN-2017-47 | refinedweb | 205 | 71.31 |
Source: Deep Learning on Medium
As discussed earlier, Gluon is an imperative API available on top of the symbolic API implemented by Apache MXNet.
One of the cool features of Gluon is the extensive collection of pre-trained computer vision models available in Gluon CV. Using these models with the Gluon API is extremely easy, but sometimes we’d rather use the symbolic API instead.
One reason could be language support: Gluon is Python only whereas MXNet supports a whole list of languages including C++, which you may need to get the best prediction performance possible. Unfortunately, the MXNet model zoo is not synchronized with the Gluon model zoo, so you can’t just grab the same models.
One easy solution to this problem is to use the Gluon API to download models, export them to symbolic format and then load them using the MXNet API.
It goes like this.
from gluoncv import model_zoo
import mxnet as mx
import numpy as np
# Download the model from the Gluon model zoo
# You'll find it in ~/.mxnet/models
net = model_zoo.get_model('resnet50_v1', pretrained=True)
# Convert the model to symbolic format
net.hybridize()
# Build a fake image to run a single prediction
# This is required to initialize the model properly
x = np.zeros([1,3,224,244])
x = mx.nd.array(x)
# Predict the fake image
net.forward(x)
# Export the model
net.export('resnet50_v1')
This will export the model weights and the JSON file containing the symbolic definition of the model.
$ ls -1 resnet50*
resnet50_v1-0000.params
resnet50_v1-symbol.json
Now you can load this model as usual with the model.load_checkpoint() API. Just make sure you use a recent version of MXNet, as Gluon models could be incompatible with older ones. YMMV.
That’s it. Now you can enjoy all these models with the symbolic API :) | http://mc.ai/quick-tip-converting-gluon-models-to-symbolic-format/ | CC-MAIN-2019-09 | refinedweb | 306 | 56.55 |
containerArray at Run-time
Before talking of stack implementation in Java using array of generics see that stack is a container to which objects are added and removed by following last-in-first-out strategy. To insert objects into and remove from stack a pointer usually called top is maintained that points to last inserted item.
Web browsers do use stack data structure to remember the list of visited sites. Every time when a new web-page is visited its address is added to the stack. The browser then allows visiting the previous page again by clicking on 'back' button.
A stack by definition supports two methods, one method,
push for adding objects to the stack, and second,
pop for removing the latest added object from the stack. To point the last item, stack uses a special pointer called
top. The following methods we plan to implement as part of our stack implementation in Java..
getTop(): Return the top object from the stack but does not remove it, return null, if stack is empty.
While implementing stack in Java, there are two choices: one is array based implementation, and second is linked implementation. Here we will implement stack in Java using arrays in object oriented way.
As Java is an object oriented programming language so we will harness object oriented features of the language during implementation of stack in Java. In order to make end user independent from implementation details of the stack implementation in Java whether it is implemented using array or linked list, we define an interface
Stack as follows. The following
Stack interface can be assigned any object that implements this interface no matter the underlying implementation uses Array based or linked list based implementation.
/* Stack.java */ public interface Stack <Item> { Item getTop(); // return the top item without removing it from stack Item pop(); // return the top item and removes it from stack void push(Item itm); //. Now define the class
ArrayStack that implements
Stack interface as follows:
/* ArrayStack.java */; return container[top--]; } public void push(Item itm) { container[++top] = itm; } public int size() { return (top + 1); } }
Let's examine the implementation of
ArrayStack class. The very first thing you will notice is that
ArrayStack takes a type parameter
Item which would be replaced with concrete type by the client code when the
ArrayStack object will be created. For example,
During stack implementation in Java, inside the
ArrayStack() constructor you will find that an array of ten items of type
Object is being created and then it is casted to generic type
Item. Could we have created generics array as
container = new Item[10]; rather than the way we implemented in
ArrayStack? The answer is NO; Java does not allow generic array creation. Now, you may be interested to know that why does Java not allow creation of generic array? This is left unanswered for your exercise.
You will also notice that inside the
ArrayStack() constructor we create container array of 10 objects. In real life situations this stack implementation in Java will soon be failed because you will not be able to place more than 10 elements in stack. This issue will be addressed by resizing array at run time. Java provides a nice mechanism of resizing array at run time, not straightforwardly but you can create another array of bigger size and then assign the newly created array object to the existing reference of previously created array.
A very important aspect of any data structure implementation is that it should use memory very prudently. The above implementation of stack in Java has a hidden flaw, where memory would not be offered to garbage collector for adding it to the free memory pool even after popping an item from the stack. This is because when the item is popped the
top pointer of stack data structure is decremented by one but the object still is there in
container, though this item would never be accessed again. If a reference to an object that is no longer needed is kept into memory aimlessly, it is called loitering. We can stop loitering by modifying the code of
pop() method as follows:
public Item pop() { if (top == -1) return null; Item itm = container[top]; container[top--] = null; // avoid loitering return itm; }
containerArray at Run-time
It is nicer idea to resize
container array for stack data structure on run time if it is about to be full, rather than to create a very big array initially. When the
container array is resized at run time, it should be sufficiently large to hold all of the existing items plus some free space but, not so large to waste excessive amount of space. To achieve this goal we implement a new method
resize() private to
ArrayStack. This new method will be declared
private because it will be called only by
push() and
pop() methods of stack data structure. The
resize() method goes as follows:
private void resize (int newSize) { Item t[] = (Item[]) new Object[newSize]; for (int i = 0; i <= top; i++) t[i] = container[i]; container = t; }
We will call above method two times, once before pushing an item to stack to check whether there is space to accommodate the new item. And second, after popping an item to check if there is much space left vacant, if so, resize the container to a smaller size. Modified versions of
push() and
pop() are as follows:
/* Modified versions of push() and pop() */ public Item pop() { if (top == -1) return null; Item itm = container[top]; container[top--] = null; if(top > 0 && top == container.length / 4) resize (container.length/2); return itm; } /*-------------------------------------------*/ public void push(Item itm) { if (top == container.length - 1) resize(2 * container.length); container[++top] = itm; }
By above implementation (resizing
container at run time) the
ArrayStack will not result into overflow and not become less than one quarter full (except when the stack is empty).
Array
Array
ArrayStackIterator to
ArrayStack. To complete the code first modify the existing signature of interface
Stack in
Stack.java as follows, no change required in interface's body.
Thereafter modifying
Stack interface, we need to modify
ArrayStack class as follows:
/* ArrayStack.java */ import java.lang.Iterable; import java.util.*;; Item itm = container[top]; container[top--] = null; if(top > 0 && top == container.length / 4) resize (container.length/2); return itm; } public void push(Item itm) { if (top == container.length - 1) resize(2 * container.length); container[++top] = itm; } public int size() { return (top + 1); } private void resize (int newSize) { Item t[] = (Item[]) new Object[newSize]; for (int i = 0; i <= top; i++) t[i] = container[i]; container = t; } public Iterator<Item> iterator() { return new ArrayStackIterator(); } private class ArrayStackIterator implements Iterator <Item> { private int i = top; public boolean hasNext() { return (i > -1); } public Item next() { return container[i--]; } public void remove() { // not needed } } }
To test the above implementation define a driver class as follows:
/* ArrayStackDriver.java */ class ArrayStackDriver { public static void main (String a[]) { Stack <Integer> s = new ArrayStack<Integer>(); s.push(20); s.push(30); s.push(40); s.push(50); s.push(60); s.push(70); System.out.println("Size of the stack: " + s.size()); // iterate through stack System.out.println("Following items pushed to Stack as of now:"); for (Integer i : s) System.out.println(i); } } OUTPUT ====== Size of the stack: 6 Following items pushed to Stack as of now: 70 60 50 40 30 20
If you observe the output generated by
ArrayStackDriver class, you will find that stack items are processed in reverse order of their insertion. It is because we processed all the items with help of
top pointer.
In array implementation of the stack data structure you will not result into overflow after implementing resizing at run time. But you still cannot claim the efficient use of memory. For example, you have an array of 16384 elements, and it runs out of space then you will expand it by double of 16384 that is 32768. Now if you have a few items to store e.g., 10, then space of 16374 elements is occupied by the array aimlessly.
In this tutorial we talked of implementation of stack in Java using array of generics. We saw what issues could rise while array based stack implementation in Java. We implemented generic stack in Java using arrays to create a stack of any user defined type. In this implementation of stack in Java we also discussed array resizing, memory loitering, and iteration through stack | http://cs-fundamentals.com/data-structures/stack-implementation-in-java.php | CC-MAIN-2017-17 | refinedweb | 1,411 | 51.58 |
Monthly Archives: May 2013
Multithreading and the C Type System | Introduction | InformIT
Multithreading and the C Type System | Introduction | InformIT.
“The Best Programming Advice I Ever Got” with Andrei Alexandrescu | | InformIT
“The Best Programming Advice I Ever Got” with Andrei Alexandrescu | | InformIT.
learning how to learn is more important than learning anything else….)
Project Euler Problem#13 solution in C++
Work out the first ten digits of the sum of the following one-hundred 50-digit numbers.
37107287533902102798797998220837590246510135740250
46376937677490009712648124896970078050417018260538
74324986199524741059474233309513058123726617309629
91942213363574161572522430563301811072406154908250
23067588207539346171171980310421047513778063246676
89261670696623633820136378418383684178734361726757
28112879812849979408065481931592621691275889832738
44274228917432520321923589422876796487670272189318
47451445736001306439091167216856844588711603153276
70386486105843025439939619828917593665686757934951
62176457141856560629502157223196586755079324193331
64906352462741904929101432445813822663347944758178
92575867718337217661963751590579239728245598838407
58203565325359399008402633568948830189458628227828
80181199384826282014278194139940567587151170094390
35398664372827112653829987240784473053190104293586
86515506006295864861532075273371959191420517255829
71693888707715466499115593487603532921714970056938
54370070576826684624621495650076471787294438377604
53282654108756828443191190634694037855217779295145
36123272525000296071075082563815656710885258350721
45876576172410976447339110607218265236877223636045
17423706905851860660448207621209813287860733969412
81142660418086830619328460811191061556940512689692
51934325451728388641918047049293215058642563049483
62467221648435076201727918039944693004732956340691
15732444386908125794514089057706229429197107928209
55037687525678773091862540744969844508330393682126
18336384825330154686196124348767681297534375946515
80386287592878490201521685554828717201219257766954
78182833757993103614740356856449095527097864797581
16726320100436897842553539920931837441497806860984
48403098129077791799088218795327364475675590848030
87086987551392711854517078544161852424320693150332
59959406895756536782107074926966537676326235447210
69793950679652694742597709739166693763042633987085
41052684708299085211399427365734116182760315001271
65378607361501080857009149939512557028198746004375
35829035317434717326932123578154982629742552737307
94953759765105305946966067683156574377167401875275
88902802571733229619176668713819931811048770190271
25267680276078003013678680992525463401061632866526
36270218540497705585629946580636237993140746255962
24074486908231174977792365466257246923322810917141
91430288197103288597806669760892938638285025333403
34413065578016127815921815005561868836468420090470
23053081172816430487623791969842487255036638784583
11487696932154902810424020138335124462181441773470
63783299490636259666498587618221225225512486764533
67720186971698544312419572409913959008952310058822
95548255300263520781532296796249481641953868218774
76085327132285723110424803456124867697064507995236
37774242535411291684276865538926205024910326572967
23701913275725675285653248258265463092207058596522
29798860272258331913126375147341994889534765745501
18495701454879288984856827726077713721403798879715
38298203783031473527721580348144513491373226651381
34829543829199918180278916522431027392251122869539
40957953066405232632538044100059654939159879593635
29746152185502371307642255121183693803580388584903
41698116222072977186158236678424689157993532961922
62467957194401269043877107275048102390895523597457
23189706772547915061505504953922979530901129967519
86188088225875314529584099251203829009407770775672
11306739708304724483816533873502340845647058077308
82959174767140363198008187129011875491310547126581
97623331044818386269515456334926366572897563400500
42846280183517070527831839425882145521227251250327
55121603546981200581762165212827652751691296897789
32238195734329339946437501907836945765883352399886
75506164965184775180738168837861091527357929701337
62177842752192623401942399639168044983993173312731
32924185707147349566916674687634660915035914677504
99518671430235219628894890102423325116913619626622
73267460800591547471830798392868535206946944540724
76841822524674417161514036427982273348055556214818
97142617910342598647204516893989422179826088076852
87783646182799346313767754307809363333018982642090
10848802521674670883215120185883543223812876952786
71329612474782464538636993009049310363619763878039
62184073572399794223406235393808339651327408011116
66627891981488087797941876876144230030984490851411
60661826293682836764744779239180335110989069790714
85786944089552990653640447425576083659976645795096
66024396409905389607120198219976047599490197230297
64913982680032973156037120041377903785566085089252
16730939319872750275468906903707539413042652315011
94809377245048795150954100921645863754710598436791
78639167021187492431995700641917969777599028300699
15368713711936614952811305876380278410754449733078
40789923115535562561142322423255033685442488917353
44889911501440648020369068063960672322193204149535
41503128880339536053299340368006977710650566631954
81234880673210146739058568557934581403627822703280
82616570773948327592232845941706525094512325230608
22918802058777319719839450180888072429661980811197
77158542502016545090413245809786882778948721859617
72107838435069186155435662884062257473692284509516
20849603980134001723930671666823555245252804609722
53503534226472524250874054075591789781264330331690
Solution:
#include <stdio.h> #include <iostream> #include "projectEulerProblem13.h" //data is stored in char data[100][51] in this file. int main () { int x, y, columnSum[50], carry = 0; for (x = 49; x >= 0; x--) { columnSum[x] = carry; for (y = 0; y < 100; y++) { columnSum[x] += (int)data[y][x] - 48; } carry = columnSum[x] / 10; } std::cout << carry << std::endl; for (x = 0; x < 50; x++) { std::cout << (columnSum[x] % 10) << std::endl; } return 0; }
Related articles
- Project Euler Problem#10 solution in C++ (alikhuram.wordpress.com)
- Project Euler Problem#12 solution in C++ (alikhuram.wordpress.com)
- Project Euler Problem#11 solution in C++ (alikhuram.wordpress.com)
Some advice for college freshmen
I don’t know the author but this seems a very good advise for fresh Graduates.
Strong skill of one or more good languages like C++, Java and C#:
Must have strong skills with control structures. Don’t mess up if you’re asked to print out triangle or other shaped piles of ‘x’s with loops.
Must have strong skills with recursion. You must know how to transform a looped task into a recursive one and vice versa, for example: multiplication using addition recursively.
If your language is C/C++, you must know how to play with pointers and references.
Understand pass by value and reference.
Clearly understand scopes and memory allocation, de-allocation. Know when an object is destroyed and when to destroy.
Know the usage of all operators including bit-wise ones.
In-depth knowledge of OOP:
Only being able to write classes and doing encapsulation and inheritance is not what you should call good OOP.
Clearly understand how function overloading, overriding, polymorphism works.
Clearly understand how constructor/destructor (if any) works with inheritance.
Clearly know the difference and use of Interfaces and Abstract classes.
Know how to overload operators. Why and how copy constructor is defined/used.
Know common data structures:
At least know the common data structures like stack, queue, linked list, doubly linked list (know circular version of all of them) and trees.
Be a skilled implementer of any of those, have clear concept of how push, pop, add, delete, peek etc method works on those data structures.
Know most common algorithms well:
You don’t need to memorize pseudo codes line by line but you need to have clear concept of most common algorithms of sorting(bubble, quick, merge, heap, bucket, etc), searching (including DFS, BFS), etc.
As a fresher you must know their time and space complexities, pitfalls and improvements (if any).
General computing concepts:
Know processes and threads, how are they related to each other, how to program them, etc.
Understand TCP/IP: Don’t think it’s only the network administrator’s task to understand TCP/IP. All programmers ever doing any network or web programming should have clear TCP/IP concepts and understanding.
Be skilled in debugging in IDEs:
Be skilled in any of Visual Studio/Visual Studio.Net, Eclipse, Netbeans, KDevelop, etc.
Know how to debug your code.
Have basic knowledge of Software Engineering and SDLC.
General Advise:
Start with C++ or Java, avoid starting with scripting languages:
If you’re learning programming for the first time, avoid starting with scripting or loosely typed languages like: PHP, ASP, Perl, etc or Visual Basic. It may destroy your understanding of program execution, data types, memory allocation, etc.
Start with C++ or Java. If you want to me to be specific, start with C++, you’ll love it for the rest of your life.. 🙂 It’ll be easier for you to learn (almost) any other language (like: C#, PHP, ASP, etc).
If you ask, do you need to know C to start with C++? Or should you learn C first and then C++? C definitely helps a lot for learning C++ but it’s not mandatory to start with C.
If you want to be a good programmer, keep on coding at least 20 hours a week for the next 4 years :). Never stop learning new technologies that are coming out everyday. Know some of the many languages/technologies but be master of one. Know at least one language very well.
Related articles
- 10 Reasons to Learn Java Programming Language and Why Java is Best (javarevisited.blogspot.com)
- Busting KDevelop myths (scummos.blogspot.com)
- How to represent OOP concepts in algorithms in a standard way? (cs.stackexchange.com)
- 7 Habits Of Successful College Freshmen (howtolearn.com) | https://alikhuram.wordpress.com/2013/05/ | CC-MAIN-2017-47 | refinedweb | 915 | 63.59 |
Books, blogs, comments and code samples
Fastware, slow progress
Few would argue with Scott Meyers’ claim to have written one of “the most important C++ books … Ever”. There is not (and could never be) a K&R for C++, but every C++ programmer should have access to the current edition of Meyers’ classic book, Effective C++, which makes sense of a subtle and complex language.
Naturally, then, I was interested to discover Meyers has started writing a new book, working title Fastware! Or maybe I should say that he will be starting on a new book just as soon as he can settle on a suitable toolchain. His new Fastware Project blog explores the issues.
Why are the tools he used so successfully to produce Effective C++ no longer adequate?
… my writing has been stalled for quite some time as I’ve wrestled with the question of what it means to write a book these days. For conventional print books, things are easy for an author, because the game is pretty well understood: ink is black, paper is white, standard font size is around 10 point, page dimensions are generally around 9"x6" with maybe a margin of around 1" on all sides …
But I don’t think the ink-on-paper world is the one I want to write for any more. I still want to write something that is recognizably a book, but I want to think of ink on paper as but one of many possible output devices. Others include computer screens (big with color support), portable ebook readers like Kindle (smaller and currently with no color support), and portable devices that happen to support text (e.g., iPhones — very small with color support).
— Scott Meyers, Two Projects in One
Here’s an example of the distinctions: Meyers corrects any errors he discovers in Effective C++ each time it gets reprinted, trying to ensure that no pages are renumbered as a result of these changes. So if you’re directed e.g. to page 44 of the 3rd edition of Effective C++, you’ll find what you’re looking for no matter which print run your copy happened to come from. Page numbers are the canonical way of referring to positions in a book, so they’d better persist.
For web based presentation of the same content, page breaking problems should be easier to avoid, but a fixed URL scheme is crucial; further, readers should be able to discover and use subsection links within a page (e.g. clicking on a subsection header could copy its permanent link to the clipboard).
On the Fastware blog, Meyers ponders more interesting examples, such as the representation of audio content and animations in different output formats. One key topic he has yet to discuss in depth is perhaps the most important of all: what to do about code samples?
Code and document editors
Consider the problem of including code in a book, or indeed an online article. Obviously, there’s a formatting problem. You can’t just paste (e.g.) C++ from your programming IDE into an HTML page or a .tex file: you’ll lose the formatting, and the angle brackets and ampersands need escaping. Not so very hard to solve, maybe, but still an issue to overcome. Experienced programmer and author Pete Goodliffe complains:
Putting code examples into blogger is hateful. HTML-conversion of templated C++ code is not my idea of a good time!
(Templated C++ code isn’t my idea of a good time either, but I think Pete Goodliffe means all those <angle> <brackets> are giving him grief.)
The formatting problem is amplified when it comes to comments. One advantage of web publishing is that readers can add comments, and may even offer code samples in their comments. One danger of web publishing is that crackers may try and attack your server by including code in their comments! As a result, comments must be sanitised, which often mangles code samples. This problem is far from being solved, as I realised when a reader posted some code in a comment on this site, which unfortunately the comment handler ruined.
Document editors and code
Pasting from a code editor into a document editor can lead to problems. So can writing code directly in a document editor — even if you’re Bjarne Stroustrup and the code is in C++, a language you invented and implemented. Here’s what happened when I tried compiling some code copied directly from Stroustrup’s paper Abstraction, libraries, and efficiency in C++ (PDF).
The code reads:
string s; in >> s; // “in” is an input stream connected to a data source cout << “I read “ << s.length() << “characters”;
The compiler barfs: '\157' in program ... bs.cpp:3: error: 'I' was not declared in this scope bs.cpp:3: error: expected `;' before 'read'
Not a bad haul of errors for code which the author found “trivial to write”!
Of course, Stroustrup has been caught out by some (not so!) smart quoting applied by his authoring tools.
(Any programming editor should expose this problem by failing to highlight “I read ” and “characters” as string literals, and if you’re reading this article served directly from wordaligned.org, rather than in a feed reader, then the javascript prettifier should do just this. The poorly spaced output bug may not be spotted until the code actually executes.)
Serious problems with code examples
Whether or not you can paste source code directly into the source text of your book/article depends on the format used for that source. I can and do copy code directly into the articles I post to wordaligned.org. A documentation toolchain based around Markdown takes care of conversion to HTML, and a clever javascript program handles syntax highlighting. The more serious problems here are twofold:
Whenever you cut and paste code between documents, more than one version of that code exists. You’ve introduced a branch.
Once code leaves its normal development environment, it can no longer be executed in the usual way.
Both of these problems can be overcome, and many conscientious authors have put together their own solutions, but I think it’s fair to say there is no single, accepted, way of solving them.
Programmers are familiar with build systems, and this is exactly Scott Meyers’ approach to book production:
… it’s crucial that I have a single master source for each book, and it’s also crucial that the various target versions of the book can be automatically built from the single master source. If this sounds like the usual requirement for cross-platform software development, it should, because that’s exactly how I think of it.
He doesn’t mention if his build system includes regression tests, which, in this case, would involve extracting the various code examples, building them, testing the output — ideally (especially for a language as close to the platform as C++) using multiple compilers on multiple platforms.
Python’s Doctest module
I haven’t cracked these problems myself and have often come to regret this flaw in the toolchain I use for code examples on this site. I’ve published syntax errors, off-by-one bugs, logical inversions — and this despite the fact that my programming and documentation editors are one and the same.
When writing about Python life should be a little easier since the compilation phase doesn’t exist, and perhaps this explains my laziness. Python’s doctest module also allows a degree of sanity checking, at least for any interpreted Python code. For example, a bug has somehow crept into the string reversal shown below:
>>> 'wordaligned.org'[::-1] 'gro.dengliadrow' >>>
Doctest exposes this problem by reading in the file, finding anything which looks like an interpreted Python session, and playing it back, checking for errors.
python -c 'import doctest; doctest.testfile("code-samples")' ********************************************************************** File "code-samples", line 104, in code-samples Failed example: 'wordaligned.org'[::-1] Expected: 'gro.dengliadrow' Got: 'gro.dengiladrow' ********************************************************************** 1 items had failures: 1 of 1 in code-examples ***Test Failed*** 1 failures.
Note though, that to properly check this article, with its intentional mistake, doctest alone is no longer up to the job, since I need to confirm the mistake fails correctly.
Subtle problems with code examples
So, formatting problems should be simple to solve. Testing code examples for correctness is hard. There are more subtle problems, too.
How do you annotate sample code? Authors frequently use comments for such annotations, resulting in code examples which are far from exemplary. Here’s another Stroustrup program, taken from Learning Standard C++ as a New Language (PDF).
#include<iostream>//get standard I/O facilities #include<string>//get standard string facilities int main() { using namespace std; //gain access to standard library cout << "Please enter your first name\n"; string name; cin >> name; cout << "Hello " << name << ’\n’; }
It’s seductively easy to adopt this style of annotation, and it’s employed in many of the best programming texts (including Effective C++). Nonetheless, it’s poor programming style. I’d like to see authors find a better way.
Can code in a book ever differ from production code? I’m more convinced by Jon Bentley’s up front note in the preface to his excellent and code-packed book, Programming Pearls:
The programs use a terse programming style: short variable names, few blank lines, and little or no error checking. This is inappropriate in large software projects, but it is useful to convey the key ideas of algorithms.
He’s right: this particular book would be less accessible if the code (e.g.) checked inputs rigorously, or employed the variable naming conventions Bentley prefers for large software projects. The difference is that the code in his book exists to illustrate the key ideas dealt with more fully in the text; whereas, in a software project, the code is the text.
Bentley balances code and text superbly, switching between pseudocode, real code and prose to find a solution matching the precise needs of his book. My only complaint is that you can’t download the code examples from the website referenced in the book (, don’t go there!) because someone has snatched the domain. Other books have different goals and it would be a severe failing if, for example, Effective C++ were to include code examples which weren’t exception safe. How often does “exercise for the reader” sound like “excuse for the writer”?
Content and presentation
Testing code samples is really a diversion from the points Meyers raises on his blog: he’s more concerned with multiple format presentation. How exactly do you arrange for suitable syntax highlighting in print, on a computer screen, in a podcast?
Traditionally, authors deliver content to publishers, and publishers control the presentation of that content. Both sides do what they’re best at. In the world of computing books, this model often isn’t the case. Programmers are capable of driving and configuring the software involved with book production — and indeed of writing new software if what exists isn’t good enough. Many programmers are ahead of the game when it comes to understanding the opportunities with newer formats. (I could also add that programmers like to be self-sufficient, enjoy tinkering, value control, and think they know better!) Reading Meyers’ blog, it becomes apparent that he takes immense care — and exercises complete control — over the final presentation of his traditional book content, in fact delivering his publishers camera-ready copy.
I write my books with a goal of their remaining useful for at least five years, and there are generally at least one or two reprints each year, so camera-ready copy for one of my books should have to be produced at least 10 times. It’s often more than that. More Effective C++, which I wrote in 1996, is now in its 26th printing.
Perfectionism and programming
Perfectionism and programming is a rare combination. Donald Knuth’s famous typesetting program, TeX, is reputedly as close as a substantial program ever gets to perfection, and it continues to set the standard for printed material (and looks likely to play a role in the print version of Fastware). TeX was born from a dissatisfaction with the available tools. Knuth simply couldn’t accept the content of The Art of Computer Programming being spoiled by ugly presentation
I had spent 15 years writing those books, but if they were going to look awful I didn’t want to write any more1
and he had the determination, passion and ability to take a ten year detour and do something about.
The outlook for Fastware!
Will Meyers find himself similarly diverted? I don’t know, but I’m enjoying reading his thoughts.
On reflection, I suggest Effective C++ succeeds because of its narrow scope. It doesn’t aim to teach programming, or even programming in C++: it’s a concise survival guide for those who work with the language. As such, its traditional printed form serves it well. It’s not an entertainment (you wouldn’t want to listen to it on a long journey) and nor is it strictly a reference (you won’t be using it to cut and paste code from): rather, it’s packed with material you need to read carefully and understand.
Fastware! a language-agnostic, multi-format book, will clearly be something very different.
Notes
DocBook aims to solve the multiple output formats problem. Loosely speaking, it comprises an XML vocabulary to describe a book’s content, together with XSLT transforms and other tools to convert that content into web pages, PDFs and so on. You can read about my experience with DocBook here.
I also recommend More Effective C++ and Effective STL, both by Scott Meyers.
1 This Knuth quotation appears in the links section of the Wikipedia page on TeX. | http://wordaligned.org/articles/code-samples | CC-MAIN-2021-49 | refinedweb | 2,308 | 60.65 |
Hey
Just wanted to share some functions I made for getting first and last days of a month and also monday and sunday of a week. Just send any date to the functions and they will return dates for you.
function getFirstDay(d){ // Returns date of first day in month var dt = new Date(d); return new Date(dt.getFullYear(), dt.getMonth(), 1); } function getLastDay(d){ // Returns date of last day in month var dt = new Date(d); return new Date(dt.getFullYear(), dt.getMonth() + 1, 0); } function getMonday(d) { // Returns date of monday in the week of date you send to the function d = new Date(d); var day = d.getDay(), diff = d.getDate() - day + (day === 0 ? -7 : 0); return new Date(d.setDate(diff)); } function getSunday(d) { // Returns date of sunday in the week of date you send to the function d = new Date(d); var day = d.getDay()-7, diff = d.getDate() - day; return new Date(d.setDate(diff)); }
They are nice to have when you have to calculate range in dates before making a data collection query.
Thank you Andreas, this is really helpfull.
But, what about date increment? how can I add 30 Days to the current date? I have problems with February and with months with 31 days. I ended up doing an extremely large function not too clean to the eyes. I'm sure there must be a straightforward solution.
Any help will be very much appreciated
Thank you!
I will look into that later
I knew there would be an easy way to do arithmetic operations with dates, actually pretty simple:
var TodaysDate = new Date();
TodaysDate.setMonth(TodaysDate.getMonth()+1);
There is a complete set of Methods for date objects specifically designed to perform arithmetic operations with dates.
Thanks for the reply
Is there a way to calculate a value based on a fixed start date and the current date?
Hi Jerry,
What value do you want? If it's the difference between two dates, then it would be something like this:
For different date calculations, you can do an Internet search and find gobs of useful stuff.
I hope this helps,
Yisrael
I am having a problem with your code Yisrael. Its hows there is an error with last bracket. Here is smy code;
import wixData from 'wix-data'; $w.onReady(function () { $w("#dataset3").onReady( () => { var date1 = itemData._createdtedDate; var date2 = new Date(); // today var timeDiff = Math.abs(date2.getTime() - date1.getTime()); // get time diff in milliseconds var diffDays = Math.ceil(timeDiff / (1000 * 3600 * 24)); $w("#dataset3").onReady( () => { { if(timeDays > 0) { $w("#text16").text = "40" } else { let daysLeft =40* timeDays; $w("#text16").text = daysLeft.toString(); } }
I want to get the total records less than 12 hours as well as more than 12 hours and less than 24 hours and records more than 24 hours.
Note . I have a data containing requests and recorded by dates
Can you help me by asking an example
make the total im textbox
This should get your started:
JavaScript getTime() Method
Use something like this to establish your boundaries:
Then do a query on your records with these boundaries:
Query between values
Something like:
wooow .... this is another code I look
nice code I will use in another process
thank brainstorrrm
But my question is how late orders are calculated
Example: I have orders that are either closed or still open
I would like to know the count number of orders that are still open and not closed
The method you mentioned is a query by today's date
While I want to query based on the date of the orders ( use order date in my data )
count : Order date + 12 hours?
count : Order date more than 12 hours and less than 24 hours
count : Order date more than 24 hours
my data collection name : data937
date field : orderdate
status field : status
and add the results in $w('#textcount12)
$w('#textcount24)
" The method you mentioned is a query by today's date (only)"
You need to read up on how Unix/JS does date and time.
Any date variable by definition has time included (whether you specify it or not) and at the core represents milliseconds since 01/01/1970. You can then take this moment in time and display it in whatever form you need.
Once you understand that, you'll understand what this simple code does.
You set the boundaries as needed (moments in time), then make your queries accordingly.
I'm assuming you are looking back 12 hours and 24 hours and you want just a count of orders in these time frames (last 12 hours, between 12 and 24, more than 24 hours) based on their status (open, closed).
Use the code above to establish the 12 and 24 hour boundaries.
Then use between queries with a simple count:
A query for all orders that have been placed in the last 12 hours and are still "open"
A query for all orders that have been placed between the last 12 hours to 24 hours and are "closed"
I can't write your code for you, but these examples should help you get started on your quest.
Thanks for the help me
But the result is 0
Can you explain why
Take a look at wix-dataset
Place all your code inside the dataset ".onReady()" statement.
You want your code to execute once the database connection is loaded and operating - otherwise you get "0" or random results.
Also, add a few console.log statements to verify that the date/time variables are the way you intend them to be - if you don't know what that is, google "browser console."
To open the developer console window on Chrome, use the keyboard shortcut Ctrl Shift J (on Windows) or Ctrl Option J (on Mac). Alternatively, you can use the Chrome menu in the browser window, select the option "More Tools," and then select "Developer Tools."
I'm really sorry ...... brainstorrrm
The code is working properly
But it seems that the problem I have is the date format
Is there a solution to this problem?
Not sure where you're hanging.
If you placed the query inside the dataset.onReady you should be getting results with this code and the dates you're showing in the collection.
Another thing to consider to do this correctly - you need to ensure that the query time is compatible with the collection time as far as timezone is concerned. To prevent timezone problems, I do all my date/time collections, queries and calculations in UTC time, with:
JavaScript setUTCDate() Method
JavaScript setUTCFullYear() Method
JavaScript setUTCHours() Method
Looking at your console.log and collection orderdate, it seems that this should not be a problem for you.
Wow I found the problem
The old history must be put first and then the new history
Between (Old History) and (New History)
The code is working properly
Really thank brainstorrrm
Oh, but of course.
Glad you figured it out. | https://www.wix.com/velo/forum/community-discussion/tip-about-getting-date-ranges | CC-MAIN-2021-10 | refinedweb | 1,166 | 69.82 |
English Code
I happened across Eric Gunnerson's blog on "Why static import is bad..." (sidenote: blogs.msdn.com is a great diversion when you're resting your eyes -- I've read a lot of interesting design compromise articles, as well as about technologies I otherwise would have ignored).
Interesting enough posting. One reader comment, by Darren Oakey, caught my eye:
`my test of readability =
"how long would it take someone who spoke english, but has never seen a computer in their life, to understand the code" '
Ignoring the rest of Mr. Oakey's comment, and his perception that the world is one of exteme contrasts with clear rights and wrongs, I find his opinion on code readability interesting. It hits a sore point with me given that this sort of "race to the bottom' mentality dictates a lot of the ridiculously contrived "code standards" out there, and it undermines the profession (I once had to deal with a manager who would rate code based upon how easily he, untrained in the language, could understand it).
Should code aspire to being readable by any untrained dummy, or should it seek to be readable by someone reasonably versed in the particular language and technology? Should I seek to make my C++ easily readable by a HTML web slinger, or should I program with the artifacts and benefits of C++ and appropriately have the expectation that said HTML slinger will perhaps learn C++ to a credible level before complaining about the readability of my code? I won't even get started on Perl... English is clearly more readable than German, as I can read English right now, but German would require me to go and learn a new language first.
Bah.
.
Thursday, July 8, 2004
"(I once had to deal with a manager who would rate code based upon how easily he, untrained in the language, could understand it)"
I can see why this would irritate you (or any other trained coder), but for the life of me I can't see this as a bad thing, given a certain minimal familiarity on the part of the reader with the basic syntax of the language.
Code readability isn't about operators, it's about comments, formatting, variable/function names, nesting, and flow of control. Good code *should* be readable by the (relatively) untrained, if they have the patience to actually read it. That's not to say that they'll grasp the subtleties, but your manager has surely been around enough code that he can get a general sense of it.
Justin Johnson
Thursday, July 8, 2004
"Code readability isn't about operators, it's about comments, formatting, variable/function names, nesting, and flow of control."
This particular manager had a Visual Basic background, and my code on that project was in C++. His evaluation of it was thus based upon the extreme dumbing down of C++ so that, without any responsibility on his part, he could fully understand it - a lowest common denominator. So C++ features such as operator overloading, which can dramatically improve readability to someone versed in C++, confused him and were declared evil. In other words what makes the code readable to someone with knowledge of C++ is entirely different than what makes the code readable to someone without C++ knowledge.
Some languages like Perl, or meta-languages like regular expressions or XSLT, unavoidably have a learning curve, by design, because the power they encapsulate cannot be simplified without dramatically diluting their productivity and value. It is absurd to judge those languages based upon whether the lowest-common-denominator can understand them, as it would be absurd to have Jimmy Sixpack rate the readability of a medical journal, or Johnny Fairplay rating the merits of an advanced mathematics essay.
.
Thursday, July 8, 2004
If your manager's a dumbass, then he's a dumbass. You can't judge C++ by VB terms, and that's it. But that's a different problem than posted in the OP.
The point made by the person you quote is hyperbole, but it contains a lot of truth: namely, that coding for expressiveness that only experts will appreciate is a recipe for obfuscated, dense code. For any construct you look at that's ugly and dense, the coder can simply say "but someone familiar with the idiom will think it's beautiful."
Someone with a bare understanding of the language, and without extra-linguistic hangups (like your boss with VB) should be able to understand at least 50% of the code, from the highest level stuff to about halfway down. It may take an expert to really grasp the subtle details, but if a newbie can't come along and understand what's generally going on, then you're coding for experts, and the result is going to be ugly, dense, and difficult to understand for anyone else.
This gets into a major problem area, because writing a script is a good deal different than writing an app, a proof of concept, or something even more complicated. Scripts are just automations of things that many of us could do with the computer. Applications, on the other hand, often interface with O/S-level drivers and functions. Also, more complicated pieces of technology can't be easily described using anything (i.e. some sorts are pretty complicated). If you don't have a science background (I don't believe I.T. and computer science are the same thing), or the necessary abstract thinking capability (i.e. those pesky managers), then perhaps that person shouldn't be involved with the project at that depth.
sir_flexalot
Thursday, July 8, 2004, and will probably have to look for your comments in the source where you overloaded the addition operator to see what the result is supposed to be when you add Foos together.
"
Sigh. Such is the pitfall of arbitrary examples.
Having said that, you're perpetuating the lowest common denominator approach. How does an expert programmer know what any custom function in a program does beyond that absolutely superficial verbose naming? The simple fact is that he doesn't and ultimately he has to take his body of C++ knowledge and build upon it with some project knowledge to reasonably expect to understand the project.
First the lowest-common-denominator (LCD) people tried to convince use that no one should have to bother with understanding the project before undertaking to do changes. Now we're being told that they shouldn't even know the language.
Such is the pitfall of straw men arguments. The person you quoted wasn't arguing for anything remotely like you're arguing against.
He was saying that good, readable code should be conceptually accessible to people even if they know only the basics of the language. That doesn't qualify them to change the code, it merely means that the code is as accessible as it can possibly be to others who have to work with the code. The learning curve has the gentlest possible slope, rather than the steepest, as you would seem to have it.
If I were to argue a straw man against you, I would suggest that you want people to have to grasp zen koans of code that take a decade of meditation to achieve satori with the perfection that spews from your keyboard. But I doubt that's what you're arguing.
The idea that code should be readible to someone with no knowledge of computers is the same as the idea that schematics should be readible to someone with no knowledge of electricity.
There are readible schematics that are well laid out and designed and there are schematics that are chicken scratches that no one can make out. The same goes for code. The only person qualified to judge whether code is readible is someone who is reasonable skilled in the craft.
It's lunacy to suggest code should be readible to the general public and spending time making code this way is wasteful when that time could have been spent making the code more understandable to another practictioner - someone who is far more likely to be the one who would benefit from doing so than that man on the street.
David Histerhoff
Thursday, July 8, 2004
Rather than saying code should be accessible to someone without a good understanding of the language, I would submit that it should be easily understood by a person without thorough knowledge of the project. For example, the more circular dependencies and global data you have in the project, the harder it will be for someone new to the project to start locating and fixing bugs. The same goes for badly named functions, "magic numbers" and string literals, and so forth.
Operator overloading can be very useful in making the code easier to read and understand. Conversely, it can also make what the the code actually does less obvious. Anybody who unilaterally decides that every instance of X is bad is just being ignorant (like that other thread where a programmer decided that database fields must never be null).
Derek
Thursday, July 8, 2004
> how long would it take someone who spoke english, but has never seen a computer in their life, to understand the code
I reckon that equates to "whether the source contains sufficient Enlish-language comments".
I like the comments to state what the code is doing (or is supposed to be doing), and the code to explain how it's doing that.
I'm a believer in the 'PDL-to-Ccomments' technique described in version 1 of _Code Complete_.
Christopher Wells
Thursday, July 8, 2004
"Such is the pitfall of straw men arguments. The person you quoted wasn't arguing for anything remotely like you're arguing against."
Did you actually read the context of the discussion? The subject of the OP was advocating that
StaticClass.Method()
Is too confusing, and throws off someone. Do you _really_ believe they believe a practitioner of development is thrown off by this?
"I reckon that equates to "whether the source contains sufficient Enlish-language comments".
I like the comments to state what the code is doing (or is supposed to be doing), and the code to explain how it's doing that."
This is an entirely fair comment, and for example if someone has a complex regular expression (because regular expressions can be quite obscure if you don't know regular expressions), I'd like to see something like
// Pull out the area code, exchange and number from the source
// form (AAA) XXX-NNNN
However the commenter wasn't talking about comments, they were talking about code, about such utter trivialities of code (like namespace or static class prefixes) that it is absolutely the supreme dumbing down of software development. When he talks about a non-programmer reading the code, it is literal.
Isn't that like expecting my cardiologist to explain everything there is to know about reading EKGs to me when I visit him.
I don't expect him to dump years worth of knowledge just to talk down to my level. Nor would I expect someone who doesn't know a byte from a bit to do the same to me.
5v3n
Thursday, July 8, 2004
> Isn't that like expecting my cardiologist to explain everything there is to know about reading EKGs to me when I visit him.
No, that's what the comments in the code are doing: explaining things in English.
Apparently what's being asked for is "worse": they're asking that the EKGs be presented in a format that let *you* (not the cardiologist) read them.
Perhaps it's (theoretically) possible to do that: you run the EKG signal through an expert system that inteprets the EKG and outputs the results for you in English ... I'm not sure why that isn't possible with software ... perhaps because the size of the "language" expressible with EKG is smaller than the size of the language expressible with software (e.g. only 70 cardiac conditions, compared with zillions of software applications).
Back on topic, what the difference between the "static import" (being discussed) and C#'s "using namespace" statement?
Static import is the idea of your class sideways deriving the static members of a class, so if classA exposes the static member Sin(), you can static import it into classB so you can simply call Sin() rather than classA.Sin().
This would similar to if namespaces contained root level functions (i.e. they didn't have to be members of classes).
I think that Darren's comments may have been misinterpreted in this thread. My interpretation was not that he really expected non-programmers to read the code, but that, if code is easier to read, that benefits _programmers_.
For instance
x = Sin(y)
is easier to read than
x = Math.Sin(y)
You think to yourself, "I want to find the sine of y", you don't think to yourself "I want to find the Math sine of y". The point being that the more closely the code matches what we're thinking, the easier it will be to work with.
On the other hand, Eric Gunnerson did post a fairly presuasive counter-argument on his blog.
John Rusk
Thursday, July 8, 2004
This is a tough call. I write a good amount of Perl.
There is plenty of obscure Perl around, and I have written some.
So the question, how hard to push a language to make full use of the features, while sacrificing legibility for the non-expert?
dot for this one
Thursday, July 8, 2004
Who cares if non experts can't read your perl code? They shouldn't read it if they are non-experts.
Matthew Lock
Thursday, July 8, 2004
"Who cares if non experts can't read your perl code? They shouldn't read it if they are non-experts."
I'm not sure if you're trying to be sarcastic (I suspect you are), however what we're really talking about isn't "expert versus normal", we're talking about "marginally competent versus has-some-general-idea-that-language-exists". Perhaps because of the .COM boom, we have such a bunch of marginal programmers in this profession with such ridiculously superficial knowledge of languages and technologies, and we believe that we have to cater to them without any demands. Spend the god damn 4 hours and read a "Language for Dummies" book.
If you want code that reads like English your ideal language would be... Cobol.
Case closed.
Chris Nahr
Friday, July 9, 2004
Chris, we are not talking about a language that reads like English, we are talking about it being comprehensible in English what your program DOES.
So, you make sure the documentation explains the general idea, where the language is obscure.
Clarity isn't 'dumbing down'.
Stephen Jones
Friday, July 9, 2004
Stephen,
Comments or documentation are hardly relevant to the discussion. You can document code in any language, so what would be the point of discussing the language at all?
Also, I wasn't talking about dumbing down but about being extremely long-winded. Conciseness brings its own clarity, and anyone who is programming a computer can be expected to have some basic grasp of mathematic expressions.
The clearest language wouldn't be one that you can grasp just with English skills (that would be Cobol) nor one that is just a string of mathematical symbols (that would be APL or obfuscated C++) but rather one that has "just the right mix" of the two extremes.
Incidentally, I think that most widely used languages today already meet this criterion, depending on which side of the middle point your tastes fall (usually begin/end vs curly braces).
Recent Topics
Fog Creek Home | https://discuss.fogcreek.com/joelonsoftware5/default.asp?cmd=show&ixPost=160563&ixReplies=22 | CC-MAIN-2018-17 | refinedweb | 2,643 | 58.01 |
Throwable class is the super class of all the exceptional class and error class. Only objects of this class can be thrown & caught and handled by try-catch blocks. In java you can throw exception Object which are derived from throwable class. To create your own class of throwable objects, you need to declare it as a subclass of some member of the Throwable family.
Here is the code:
public class ThrowableClass { public static void main(String args[]) { try { int i = 9; int j = 0; int result = i / j; System.out.println(result); } catch (Throwable t) { System.out.println(t); } } }
Output: | http://www.roseindia.net/tutorial/java/core/throwableClass.html | CC-MAIN-2016-30 | refinedweb | 101 | 64.2 |
Bean Validation in RF 3.3.3John Leed Jan 13, 2010 10:18 AM
Is Bean Validation supposed to work out of the box in RichFaces 3.3.3? I have the constraint annotations placed on my JPA entities, but there aren't any Faces messages popping up for invalid input. However, when I try to commit changes JPA is reporting a ConstraintValidationException, so it looks like everything is working correctly except for JSF calling the bean validator during the appropriate phase.
By the way, I'm using RF 3.3.3 BETA1 with Facelets 1.1.15 on Glassfish v3.
1. Re: Bean ValidationJohn Leed Jan 12, 2010 3:52 PM (in response to John Leed)
If I add Ctrl-V... Ctrl-V... Right-click... WTF, the new forum doesn't paste?
Anyway, if I add <f:validator to an input field, then bean validation will validate that field as expected. According to the JSF 2 spec section 2.5.7, JSF is supposed to pretty much do that for every UIInput.
So I figured maybe I could add this:
<application>
<default-validators>
<validator-id>javax.faces.Bean</validator-id>
</default-validators>
</application>
No luck there.
2. Re: Bean ValidationIlya Shaikovsky Jan 19, 2010 5:36 AM (in response to John Leed)
import javax.validation.constraints.Size; /** * Created by JBoss Tools */ public class Person { @Size(min = 2, max = 3) private String name; public Person() { } public String getName() { return name; } public void setName(String name) { this.name = name; } }
and
<h:form> <h:inputText <rich:beanValidator /> </h:inputText> <h:commandButton <a4j:commandButton <rich:messages/> </h:form>
both buttons causes messages to appear for me. I've used for test next env:
- hibernate-validator-4.0.2.GA,
- RichFaces 3.3.3 - snapshot
- JSF 2.0.1
- tomcat 6
3. Re: Bean ValidationJohn Leed Jan 19, 2010 9:52 AM (in response to Ilya Shaikovsky)
I'm running on Glassfish v3, so everything I need should be in the classpath, aside from Facelets 1.1.15 and RF 3.3.3.
As long as a JSR-303 implementation is available, JSF 2 should automatically add the validator to every UIInput, unless the context-param javax.faces.validator.DISABLE_DEFAULT_BEAN_VALIDATOR is set to true. See JSF 2.0 spcc, section 2.5.7.
So - at least from my understanding - it shouldn't be necessary to add <rich:beanValidator /> in JSF 2. I mean, I can understand why we can't use JSF 2 tags like f:ajax with RichFaces 3.3.3 - they simply don't exist in Facelets 1.1.15. But this shouldn't have anything to with the PDL, should it?
4. Re: Bean ValidationIlya Shaikovsky Jan 19, 2010 10:38 AM (in response to John Leed)thanks for this update. I will continue investigation.
5. Re: Bean ValidationIlya Shaikovsky Jan 22, 2010 8:35 AM (in response to Ilya Shaikovsky)
Can't find precise place in JSF 2 specification but it seems for me that validators not instantiated by default if running in jsf 1.2 compatibility mode. I tried to create simple JSF 2 project from scratch and validators worked as you told till I added Facelets 1.1.15 and turned default VDL viewHandler off. Then I tried different definitions but default validators no more working without to be explicitly defined.
Thanks! I will add this to compatilibity limitations wiki document.
6. Re: Bean ValidationJohn Leed Jan 22, 2010 9:39 AM (in response to Ilya Shaikovsky)I don't think javax.faces.VALIDATE_EMPTY_FIELDS works either. I've gotten BV to work without the rich:beanValidator tag by using a phase listener that adds BeanValidator to all UIInputs, but I still have to put required=true on the inputs.
7. Re: Bean ValidationJohn Leed Jan 22, 2010 4:11 PM (in response to Ilya Shaikovsky)I filed an issue with Mojarra; maybe this limitation will get some attention: | https://developer.jboss.org/thread/146709 | CC-MAIN-2019-39 | refinedweb | 650 | 58.28 |
(moved from SyntaxConsiderations)
[JamesSnell] We should formally capture the data model as an InfoSet. This will help abstract the model so we can switch easily between multiple syntaxes if necessary
[SeanMcGrath RefactorOk] Please, please avoid going down the Infoset road. Yes, use XML syntax, just enough XML to get the job done yet still be easily "round-trippable" and "lossless."
I agree with Joe [AsbjornUlsberg]
[JeremyGray] 0 to infoset. +1 to namespaces. +1 to core in a single namespace. +1 to core namespace as default (saves bandwidth, increases ViewSourceClan clarity, and is processed no differently by real XML tools). -1 to modules in core namespace (should be in a separate namespace, and I would much prefer one per module.). The core namespace should be the baseline of what is required and what is optional but generally expected to work in Atom-powered applications.
[JamesSnell] Ok, well, It appears I'm not going to get my way so I'll concede the point of not having an infoset model... BUT, with that being the case, we need to be extra careful to fully articulate our model while describing the syntax.
[JoeGregorio] Please, no infosets. Just straight XML syntax. As for namespaces, I would like to see the 'core' of this new format be in a single namespace. The core needs to be simple to 'view-source' and implement. Using a slew of different elements from different namespaces would make that more difficult. I wouldn't mind the single namespace chosen being the nil namespace, though I am sympathetic to arguments against that. I would also like to see as many of the optional modules in the core namespace as well.
[DannyAyers] -1 to infoset (I'd favour an RDF/OWL version, but that doesn't look like happening), +1 to namespaces. +1 to core in a single namespace, +1 to we need to be extra careful to fully articulate our model while describing the syntax.
[RahulDave] On Infoset vs XML syntax,. (copied from NamespaceDiscussion)
[DougRansom] Would the specification be hosted on a RDDL page and include some form of XmlSchema -- maybe Schematron?
I think it is a good idea to have an Infoset; after all, XML tagged text may not be the only serialization. There have been suggestions on this wiki to use yaml, etc.
CategoryArchitecture, CategoryModel, CategorySyntax | http://www.intertwingly.net/wiki/pie/InfoSetDiscussion?action=highlight&value=JoeGregorio | CC-MAIN-2017-47 | refinedweb | 387 | 64.61 |
Head-to-Head: PHP vs. ASP.NET
You guys know by now that I do not realy like PHP for projects beyond the 1 or 2 pages of simple select ... from, right?
Just me (Sir to you)
Thursday, May 8, 2003
As someone who has used both PHP and ASP.NET (though I'm not primarily a web developer) that comparison is surprisingly fair, considering it was posted (presumably) to promote ASP.NET.
PHP is pretty nice for small to mid-sized sites, but I do agree the function names are a big mismash of inconsistent naming styles, and since there is virtually no object orientation in the base libraries, it can be a pain to search through the hundreds of built in functions for the one you are looking for. ASP.NET, in my experience, scales a lot better to large projects and the variety of languages available for development is a real plus.
Of course one thing they don't highlight much in that article is that you can deploy PHP for free (free OS, free web server, free framework) whereas with ASP.NET you have to pay for, at a minimum, the base server-level OS it is running on (since you can get by without an IDE and just use the framework SDK to do development). Of course this cost is meaningless to a big project, but for small mom & pop sites this cost can be a factor.
George McBay
Thursday, May 8, 2003
You claim that, in PHP, the functions are hard to find.
The PHP library is indeed a procedural one, and not Object-Oriented, BUT, except for very few functions, they all start with the group name.
For example, all the functions dealing with MySQL start with "mysql_", etc.
It is, in my experience, EXTREMELY easy to find the functions.
PHP has the advantage of richness - download the PHP help file (in .CHM format) and look at it. It's library is very rich. It can talk to a lot of e-commerce systems, databases, and do A LOT of things like create flash files on the fly, create PDF, send e-mail without requiring an external component like the old ASP did, etc.
PHP is a very, very rich language.
Also, the language itself is very cool - it is highly optimized for the way developers use it - for example, if I have a variable called $a, and I want to output it, I can even put it in a string:
echo "Here is the value of the variable \$a: $a";
Variable expansion does not happen with single quotes strings!
The container object (the array) is VERY powerful, almost like the Python containers!
There are many such optimizations, and the language is a pleasure to develop with.
On the other hand, ASP .NET has the advantage of a powerful RAD environment behind it. It also has components.
These things matter A LOT: no more writing code by hand to display and edit a table or a query result, for example.
So, I belive ASP .NET is superior to PHP because of the RAD environment. It is an advantage that is far more important than the other advantages of PHP.
Michael K.
Thursday, May 8, 2003
"PHP is a very, very rich language.
Also, the language itself is very cool ..."
I must respectfully disagree. I recently did a small website for a local nonprofit. An ISP offered free hosting, and they had PHP.
PHP isn't a rich language - it's a syntactical mishmash that happens to have a lot of libraries. None of which helped me, because our web host didn't have any of them installed.
I don't buy the "rich library" argument, because there didn't seem to be any of the really helpful things. Where's the libraries to help in generating forms? In validating input? If they're there, I couldn't find it.
The very weak OO support, plus the default "assignment is copy" semantics results in a language that's very easy to make mistakes in.
And there's NO DEBUGGER!
Chris Tavares
Thursday, May 8, 2003
I used to be an ASP programmer (no .NET) but after evaluating a number of technologies I switched to PHP3 (this was back in the day). It was heads above ASP -- you could do things in PHP that were just plain impossible in ASP in a general hosting environment.
Those who say that PHP isn't good for large projects just haven't been using it correctly. I have a project that's 5MB of source code an over 1,000 files. It's very easy to maintain and is very object-oriented.
The biggest mistake I see is that people don't understand what do with all the PHP functions. Most of the PHP functions should not be called directly. For database access, you should be using a high-level object-oriented database abstraction. For those used to using ADO, there is the excellent ADODB library for PHP. PHP also comes with PEAR, which is a large class library for all kinds of operations. PHP functions are mostly just loose wrappers around standard unix libraries (like the MySQL C client library, GD graphics library, etc). This allows PHP developers to build the abstractions rather than rely on a built-in abstractions that would, in turn, just calls these library functions anyways.
PHP is not without it's problems (and I should know!) Though I'm constantly impressed with the rate of development on PHP. PHP5, which is well on it's way to being released, fixes a number of the architecture problems listed in the article and in this forum.
I do think that ASP.NET is an excellent platform and it fixes many of the issues that caused me to run away for ASP. In fact, I'm hoping to get a consulting gig to convert an existing large-scale ASP application into an ASP.NET application.
The ultimate biggest problem with ASP.NET is Windows and IIS. For general hosting, a unix/apache solution is far superior. I would recommend IIS and ASP.NET only for projects were there is already a strong Microsoft software basis (like a web-frontend to an existing corporate backend).
Wayne Venables
Thursday, May 8, 2003
I'm not a big user of symbolic debuggers. Sure a stack backtrace is nice and breakpoints can help find well hidden bugs. I end up using mostly printf's or the local equivalent. Usually I make stand-alone version of anything remotely tricky so I can do the debugging on the component/function(s) alone. That's my approach with PHP as well. But if you need a debugger get Zend's I've heard good things about it and it's not that expensive at 195$ to 245$ for the IDE.
The functions do have an irregular naming convention. I've been following the developement of PHP for a while and they've been slowly renaming them as they go (although the "traditional" names remain.)
The attacks on the OO capacity of PHP are quite justified since the class in PHP4 they're mostly useful to manage the namespace. PHP5 will add much richer OO features as well as exceptions handling with try...catch blocks.
Also, there's a trend of merging the most popular optional library with the main distribution. Witness the early inclusion of the mysql client libraries and now gd (graphics.) PEAR is still maturing but that will add even more options to add external components.
Alex
Thursday, May 8, 2003
The latest version of PHP (4.3.x) includes a function to retrieve the backtrace of an error. Very handy. I have all errors automatically emailed to me with as much information as possible. It's amazing the number of errors you can find and fix that way.
Typically, they don't like to include client libraries directly with the distribution. GD2 was included because the library wasn't being maintained -- PHP developers had a large number of bug fix and enhancement patches that were not being added to library's official distribution. I'm glad they did that, GD2 has been in "beta" since forever and there were always build problems with it.
> I don't buy the "rich library" argument, because
> there didn't seem to be any of the really helpful
> things. Where's the libraries to help in generating
> forms? In validating input? If they're there, I
> couldn't find it.!
Also, let's say you have to generate an image (for a graph, etc). ASP contains absolutely NOTHING to help you with this. PHP contains a full and powerful library of functions which help you do that.
> And there's NO DEBUGGER!
There are MANY debuggers for PHP, which work well.
Just try ActiveState Komodo, or Zend Studio. I have worked with both, and they are good, solid debuggers once you learn to use them.
!
Who cares? The discussion is on ASP.NET not classic ASP.
Arab who worships Camels
Thursday, May 8, 2003
Besides, you're wrong. IIS ships with an SMTP server, which can be drive by the CDONT COM objects from classic ASP with just a few lines of code.
Brad Wilson (dotnetguy.techieswithcats.com)
Thursday, May 8, 2003
> Who cares? The discussion is on ASP.NET not
> classic ASP.
Comparing ASP .NET with PHP is meaningless.
ASP and PHP are in the same generation of server-side scripting languages.
ASP .NET is the next generation, which has a RAD environment. This is, or has the potential to be a HUGE improvement in productivity.
So, comparing PHP with ASP .NET is like comparing Quick Basic 1.0 (the one that came with DOS) with Visual Basic 3.0.
There is simply no way to compare them - they are different things.
Will there be an PHP .NG (next generation) which will be equal to ASP .NET, or even better?
I don't really know, but I don't think so.
PHP is developed by a community of Unix / Linux / open source fans who don't seem to understand the importance of RAD.
For example, they consider that Linux has excellent develpment tools, because, look, it has GCC and Perl. :)
They are entitled to their opinion, but in my opinion, a superior development tool, in this day and age, MUST be a RAD one.
Yet, PHP is developed by people who consider that GCC + VI = a great development tool.
:-(
<sarcasm> And, as we all know, nothing good has ever come out of all those projects that use gcc and vi.... </sarcasm>
:sigh: Give me four terminal windows and vi over Visual Studio any day...and yes, I've used both.
Brent P. Newhall
Friday, May 9, 2003
Hey! I'm not saying you can't develop using GCC and VI!
But a RAD environment is a lot more productive, compared to that.
I know that RAD has a bad name among many programmers, especially because of Visual Basic, which has many problems, like interpreted code (no longer true in VB 5 and 6), crappy programming language, buggy components, etc.
But there are also RAD environments, like Delphi, C++ Builder, JBuilder, that don't have the disadvantages of VB, and are very cool.
ASP .NET is highly superior to PHP because there is a good RAD environment for ASP .NET, and that environment will be mainstream / used by most ASP .NET programmers.
Unless PHP gets a strong RAD environment used by most PHP programmers, it will fall farther and farther behind ASP .NET.
Michael K.
Friday, May 9, 2003
----
:sigh: Give me four terminal windows and vi over Visual Studio any day...and yes, I've used both.
----
You know, even Bill Joy gave up on vi eons ago...
Paul
Friday, May 9, 2003
"ASP .NET is the next generation, which has a RAD environment. This is, or has the potential to be a HUGE improvement in productivity."
That's the crunch question. What ASP.NET gains on PHP in tools it loses again by being (apart from JScript which no one seems to be interested in) strongly typed. Put a (experienced) PHP coder with just a text editor and their prefered choice of PHP class libraries alongside a .NET coder and my guess is they'll be equally productive.
The .NET class library is excellent yes but PHP is not lacking in libraries of it's own, though not of the same scale, which do offer some of what the article claims PHP doesn't have. Also check out PHP based frameworks like eZ publish () for an idea of how far well written PHP scales (e.g. - the guys behind alltheweb.com).
With PHP5 (probably 7 months away), aside from an object model which looks much like Java, PHP will have great interop, being able to access both the Java and .NET libraries (plus COM and even Python, Perl and Ruby (may be)) natively without additional layers like SOAP. So thanks MS for designing it. All that remains is a PHP parser to bind ASP.NET markup to the class library, which isn't so hard.
Anyway - .NET is a great technology but late to the game IMO. PHP effectively already is the "monopoly" solution for building dynamic web sites so there's plenty of time for perfection...
Harry
Wednesday, May 21, 2003
ASP.NET has a much better answer to separation of code and presentation than PHP does. ASP.NET web controls are a GREAT way to get reuse. PHP just gives you tag soup.
Chris Tavares
Thursday, May 22, 2003
I use PHP because there are plenty of free libraries and classes available for free using which you can accomplish pretty much anything. I don't feel like spending $100s on ASP components that are free for PHP.
Alex
Saturday, May 31, 2003
From a Marketing and sales perspective.
I would choose PHP over ASP as running a database driven website it is much easier to convert PHP urls's to search friendly data.
I have not seen anything for ASP to do this easily. :-)
James Tervit
Monday, April 19, 2004
Recent Topics
Fog Creek Home | https://discuss.fogcreek.com/joelonsoftware2/42872.html | CC-MAIN-2020-10 | refinedweb | 2,376 | 74.08 |
We can think of the attributes that the class provides the instance as class attributes. Notice that all instances of the class share the same attributes as they are provided by the class object.
How can the instance acquire its own attributes?
The answer is that instance attributes are created when you assign to an instance.
In this case the usual rule in Python that assignment creates an attribute or a variable is followed.
This means that after assignment the instance has its own attribute.
For example:
myObject=myClass()
print(myClass.myAttribute)
myObject.myAttribute=3
myClass.myAttribute=2
print(myClass.myAttribute)
print(myObject.myAttribute)
In this case after assignment to myObject.myAttribute the instance no longer uses the class attribute and so you see 1, 2, 3 printed.
Assigning to the class attribute has no effect on the instance attribute and vice versa.
The rule is that changes to an instance’s dictionary never update the class dictionary. For example, you can delete an instance’s attribute and after this the class attribute of the same name will be used.
Also notice that you can add attributes to an instance that are not defined in the class.
That is, you are not restricted to simply overriding the class attributes. However, it is a good idea not to add attributes to an instance that are not defined in the class because this spoils the idea that the class is in some way a definition of all of the instances it creates. It is ad-hoc programming and likely to result in a very messy program.
These ideas are discussed more in Chapter 7.
Attributes can be any object but when attributes are functions things are slightly different. A function that is an attribute of an object created using a class is converted into a method.
Before we look at how this works it is worth spending a few minutes looking at the general problem and exactly what a method is.
When we first started writing programs in higher-level languages, best practice was to write a function for whatever sets so.
So the key point is that:
is a function that accepts the data it is going to work with as its first parameter and:
is a method that belongs to the myArray object.
You can see that if you want to use a function as a method all you have to do is convert that call to the:
myArray.sort(*args)
method into a call to the:
myArray(sort,*args)
function.
In Python this transformation from method to function works in a very direct way. Within the class you create an attribute as a function attribute and the first parameter, usually called self, is the instance that the function is to be a method of.
class myClass:
myAttribute=1
def myFunc(self):
print(self,myAttribute)
myFunc is just a standard function object. The first parameter is only named self by convention – you can use any name you like but be prepared to confuse everyone if you do.
If you call myFunc as an attribute of the myClass object then there is nothing new:
print(myClass.myFunc(myClass))
and it prints 1 as you would expect. Notice that you have to explicitly pass a value for self and this is just the object you want the function to operate on.
Things are different if we create an instance of the class and call myFunc:
myObject=myClass()
print(myObject.myFunc(myObject))
If you try this out, calling myFunc as if it was a function as before, you will find that you get an error message:
print(myObject.myFunc(myObject))
TypeError: myFunc() takes 1 positional argument but 2 were given
which, like most error messages, doesn’t actually tell you what the problem is.
More to the point when you look at it then you have to come to the conclusion that the error message lies! It is quite clear that myFunc takes one argument but “2 were given” is clearly wrong. Only one argument was given so what is going on?
The answer is that when you call a function defined on a class from an instance, the first thing that happens is that the attribute is looked up in the instance’s dictionary as usual; when it isn’t found it is accessed via the class object’s dictionary.
However, instead of returning the function object, the attribute access creates a method object as a wrapper for the function object which is something like:
def method(*args,**kwargs):
return myClass.myFunc(myObject,*args,**kwargs)
In other words, the function is converted to a method by an object which calls it with the first parameter set to the object that the function is now bound to. Now you can see why the call has two arguments – one is automatically provided by the system and the second, the one you supplied, is superfluous.
The correct way to call the instance’s method is:
myObject=myClass()
print(myObject.myFunc())
The system supplies the self parameter in the call – myObject in this case.
Notice that you don’t have to call the method to create it; accessing the attribute is enough to wrap the function object as a method object. | https://i-programmer.info/programming/python/14133-programmers-python-objects-become-classes.html?start=1 | CC-MAIN-2021-25 | refinedweb | 875 | 60.85 |
- 28 Feb, 2021 1 commit 5
For User instances that already have a token, it is now possible to manage SSH keys even if the root password is unknown to the tests. --HG-- branch : stable
We introduce a new "Group owner" CLI option to specify the relevant user, with the idea in mind that all test data will evntually be created inside this group. For now it is in the user personal namespace for simplicity. The basic idea is to avoid changing the test itself, playing on the fixtures. The first test to actually work in this mode is the very simple `push_basic` test. Of course some tests perform more server-side object creation, assuming admin powers, and would need deeper adaptation, but a good majority of our tests should work readily. To achieve this, we subclass `Heptapod` and replace preparation (of the `root` and `test_basic` users) with preparation of the given Group owner. --HG-- branch : stable
Only those tests that have the `@suitable.prod_server` mark will be run in this mode. Currently validated with the `push_basic` test. --HG-- branch : stable
- 16 Feb, 2021 1 commit
In the refactor for the users registry, we forgot to store the `User` instance for where expected users (only actual example is `test_basic`) already present in the database. Wasn't catched by CI because it runs on a fresh database. --HG-- branch : stable
- 15 Feb, 2021 1 commit
This solves a discrepancy that has plagued the heptapod-tests code base for long. In the beginning, users where represented as simple dicts, themselves kept in a registry: `user` attribute of the `Heptapod` instance. Then, more advanced manipulation needs pushed to the creation of the `User` class, but the user registry wasn't updated at the time. The tricky part, explaining why it wasn't made right away is that we often start with a partial representation of the user: for instance not knowing its numeric id. Over time some of the test code has been updated to use higher-level methods of the `Heptapod` class, such as `get_user_webdriver()`, in prevision for the present move, but still, the registry values remained at heart just dicts, while lots of needed logic is implemented in the `User` class. Now we'll have `User` instances in the registry. That still leaves us with some illogical aspects, like lazy webdriver and token initialization indirected through the `Heptapod` class, instead of being transparent properties `User`. But from now on, improving on this should be incremental and involve identifiers easy to search in the code base. --HG-- branch : stable
- 13 Feb, 2021 2 commits
Forgot to publish that before bumping the stable branch --HG-- branch : stable
Merged default branch into stable and fixed CI image --HG-- branch : stable
- 30 Jan, 2021 1 commit
In the context of the Heptapod Development Kit (HDK), we use a wrapper launch script, which gives us the opportunity to inject environment variables. Notably we can: - use the same version as Python Heptapod components (such as HGitaly - avoid the system defaults. A current use case is that pytest-parallel does not support Python 3.9 yet. With the `HDK_HEPTAPOD_TESTS_BASEPYTHON` environment variable, we can define `testenv:hdk` without local modifications to `tox.ini`. The default `python3` value should help in transition time, even if it doesn't seem likely that we'll have wrapper scripts that use the `hdk` testenv without providing the environment variable value.
- 27 Jan, 2021 1 commit
- Raphaël Gomès authored
- 19 Jan, 2021 1 commit
- 10 Jan, 2021 1 commit
- merge default branch into stable branch - updated base image in CI configuration --HG-- branch : stable
- 08 Jan, 2021) | https://foss.heptapod.net/heptapod/heptapod-tests/-/commits/c573dd3b0ebb0550460a8b87de708c8088b99ee9 | CC-MAIN-2021-43 | refinedweb | 603 | 56.89 |
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RESTfulie - A Gem To Create Hypermedia Aware Services And Clients
Guilherme Silveira writes to InfoQ on the release of a ruby gem that makes developing hypermedia aware services and clients that consume them a breeze. He said
Much has been spoken about what is and what are the advantages of using rest/restful ideas in one's application. Last year, Mark Baker wrote about hypermedia content in restful applications. There are also a few texts on more formal attempts to define HATEOAS and its advantages. Although being some good usage of the web in order to create web-based services, it is still missing the very best part of our every day life: hyperlinks and hypermedia content.
He goes on to describe an example of defining an order that goes through a well defined set of transitions for e.g. from example from unpaid to paid etc. It also allows the mapping of various transitions to a corresponding actions...
class Order < ActiveRecord::Base
state :unpaid, :allow => [:latest, :pay, :cancel] state :cancelled, :allow => :latest transition :latest, {:action => :show} transition :cancel, {:action => :destroy}, :cancelled transition :pay, {}, :preparing end
Which generates, for example, an atom based resource representation that has embedded hypermedia:
<order> <product>basic rails course</product> <product>RESTful training</product> <atom:link xmlns: <atom:link xmlns: <atom:link xmlns: </order>
And allowing the client to invoke dynamically created methods from consuming that resource representation:
order = Order.from_web '' order.pay(payment)
Jim Webber, on whose RESTBucks article and forthcoming REST book has been inspiration for the creation of this gem, said
The mulit-talented Guilherme Silveira with Adriano Almeida and Lucas Cavalcanti, has been coding up a storm on the RESTful services front. [...] More importantly, they’ve written up a generic client that can be used to explore that protocol. They’re hosting the demo service on GAE, and have released their code for all to enjoy on GitHub. Fabulous work guys, and very timely too
Savas Parastatidis, the co-author of the book had the following comment
I can’t wait for our book to finish so that everyone can check out our discussion of hypermedia and the stuff we’ve built. It’s really great to see Restfulie taking a very similar approach to ours.
Detailed examples of the gem usage for creating RESTful services and clients that consume those services are available at the GitHub project repository.
I must be dreaming
by
Jean-Jacques Dubray
order = Order.from_web resource_uri
puts "Order price is #{order.price}"
order.pay payment # sends a post request to pay this order
order.cancel
What? Actions? Dilip, are you sure you gave us the right URL? That can't be RESTful?
More seriously, what have we gained from Web Services? How does a client "adapt" to a changing lifecycle (on the "server" side)?
It's kind of sad that for the last several years the RESTafarians have talked about the "uniform interface" and all we do now in RESTafaria is encoding actions behind the HTTP verbs. That's called progress? What a waste of time, what a bunch of boloney.
What's next? a contract? Ah no, they already have one...
class Order < ActiveRecord::Base
def following_transitions
transitions = []
transitions << [:show, {}]
transitions << [:destroy, {}] if can_cancel?
transitions << [:pay, {:id => id}] if can_pay?
transitions << [:show, {:controller => :payments, :payment_id => payment.id }] if paid?
transitions
end
end
On the positive side, it's good so see yet another evidence of the emergence of the state machine / entity lifecycle in connected systems.
Re: I must be dreaming
by
Dilip Krishnan
More seriously, what have we gained from Web Services? How does a client "adapt" to a changing lifecycle (on the "server" side)
For one, the client no longer relies on "cool urls" and the server can "guide" the clients as the service as it progresses thru' the business process. Its WS-* speak its similar to using a UDDI service to provide an indirection for service locators, only a much lighter weight way of doing it.
On the question of what has been gained from web services, I would say the fact that we can have an object oriented programming model via some ruby meta-programming magic. Tho' whether thats a good thing or not is debatable.
Re: I must be dreaming
by
Dilip Krishnan
What? Actions? Dilip, are you sure you gave us the right URL? That can't be RESTful?
The link to the gem has been updated. Thank you for pointing that out.
Re: I must be dreaming
by
Jean-Jacques Dubray
Re: I must be dreaming
by
Dilip Krishnan
Could you elaborate on what it means for a programmatic client to be "guided"?
If you take the following example say you GET an order which is in a particular state that allows you to pay or cancel (demonstrated by the link/rel)
<order>
<product>basic rails course</product>
<product>RESTful training</product>
<atom:link xmlns:
<atom:link xmlns:
<atom:link xmlns:
</order>
If the seller decides to offer a coupon perhaps, for orders that meet a certain criteria; then they could add another transition. Or if the service changes the tracking uri. When the client GETs the latest order for tracking he/she sees a new available "action" and uri.
<order>
<product>basic rails course</product>
<product>RESTful training</product>
<atom:link xmlns:
<atom:link xmlns:
<atom:link xmlns:
<atom:link xmlns:
</order>
This is what I mean buy guide.
do you imply that somehow the server can change the order lifecycle and the client code will somehow know what to do? that sounds like science fiction.
The intention is not to imply that this is a mechanism to automate client interactions, for e.g. if a BOT were tasked to place 20 orders, they will not suddenly recognize that the order lifecycle has a new coupon linked to it and know exactly what to do about it and alter behavior on the fly. That would be science fiction :)
The implication is just that the client is not bound to a particular lifecycle uri. After the initial request the service can guide the clients navigation accross the "known" business process states. The client would still break if the lifecycle were to change for e.g if we add an approval process to the order after its paid etc.
Re: I must be dreaming
by
Jean-Jacques Dubray
thanks for the precisions.
>> The intention is not to imply that this is a mechanism to automate client interactions
makes sense
>> The implication is just that the client is not bound to a particular lifecycle uri.
No sure I am following what you are saying, again, assuming that actions are well known to both the client and server, I am not sure clients would easily invoke these actions on dynamic endpoints. This presents such a security threat (injection) that you would think no one in their right mind would want to do that.
Re: I must be dreaming
by
Dilip Krishnan
No sure I am following what you are saying
For some reason my formatting isnt showing up in firefox... but notice how the "latest" action is now in the second listing. Consequently the server has now changed the uri to access the "latest" orders without affecting the client. May not be the best example, but it shows how the server can evolve independently from the client, thus removing the coupling of the client to the action uri.
This presents such a security threat (injection) that you would think no one in their right mind would want to do that.
The example is probably not elaborate enough to account for security scenarios, which will most likely involve SSL/OAuth etc. Having take care of that how is this any different from an ESB?
Re: I must be dreaming
by
Jean-Jacques Dubray
I was hoping a less mundane application of HATEOAS, but I guess we agree that when the client is a software agent, there is not much that can be done in terms of adapting to changing states and transitions.
In the end, there is no gain with respect to Web Services, since we are just changing the encoding of the actions. We have circled back where we started, wasting a couple of years in the process and pushing countless people to CRUD. Now, they can invoke actions again. What a progress.
I suggest we could give a hint to the server with a custom HTTP header called RESTaction... We could also suggest a totally new and cool pattern, the wrapped resource representation (WRR) pattern whereby we wrap the resource representation that we post as part of an action invocation with a root element which is named after the action we invoke. That way we keep everything conveniently in one document for further downstream processing. That way we could actually route the action invocation in the back-end, rather than always wiring it to a Java or C# method.
Of course, by using REST we have lost everything else such as bi-directional interfaces, asynchrony, assemblies, orchestration... but who cares?
I would strongly encourage Guilherme to explain how "events" fit in the picture. The good news is that Guilherme understands the concept of a resource lifecycle and the difference with a business process (unlike Jim and Savas). Since a resource lifecycle is made up of states and events are the occurence of a state, how can REST handle events? Again, minor (and rather annoying) architecture detail.
Re: I must be dreaming
by
Guilherme Silveira
I am sorry about the delayed (and long) response.
In the end, there is no gain with respect to Web Services, since we are just changing the encoding of the actions.
I believe that even if, in the end, the result would be the same, one can not say that taking different paths to achieve the same result is the same and therefore a waste of years of research.
If that was true, why would other companies try to build cars when we already have american ones doing so? They have the technology and it would be enough if they provide us all with it: we would drive our cars - as we do today.
But koreans, japaneses, germans, chineses, french... have also their own cars, which have the same goal in mind... are we back at the same place?
The process that allows us to create different solutions for the same problems is the basis of innovation.
And it is true not only for private-research based technology as cars, but with open ones too.
If the world was a place where people would just adopt one solution and never try creating different ones for the same type of problem, corba could be the only solution for distributed systems and, following that line of thought, why would someone ever try webservices? After all, corba might solve your problems... but what would happen then? You would have to adapt your system to corba's limitations or adapt corba to your system's limitations. In the end, you would have your system up and running, but the process that took you there brought you new choices that might be cheaper and faster (or cost more and slower) than the already existing ones.
The same holds for programming languages and pretty much every other possible human evolution: we could still be living with the same technology from the 80's... but everything would have a much higher cost, being therefore less profitable and scalable (thinking about humankind reach).
Summing up, even if in the end, two ideas (web services and what has been debated), achieve the same goal, the pure existence and its competitors development process allows technologies to evolve.
An old technology which does not get ideas from others upcoming ones is faded to be outdated.
We have circled back where we started, wasting a couple of years in the process and pushing countless people to CRUD. Now, they can invoke actions again. What a progress.
Therefore I am afraid I can not agree with this sentence. There is no waste of research or money even if the result was exactly the same.
But again, the result is not the same: it involves costs, time-to-production, quality of code and so on. And that's where I believe we might be helping.
Creating a system using a full WS-stack nowadays still takes a lot of effort although some technologies (as soap4r) can really help you out.
Restfulie might help projects pretty much in the same way that SpringMVC does in the Java web frameworks path. It is not an commitee-based standardized implementation, but it helps companies on the whole world solve their problems. As there is space for Spring MVC and JSR-based framework implementations on the market, WS-stack-based and restfulie (or any other framework) based solutions can help our clients solve their problems, we just have to use the one that fits better depending on the client's reality.
Regards
Guilherme
Re: I must be dreaming
by
Guilherme Silveira
Again, sorry for the delayed response...
Having take care of that how is this any different from an ESB?
I believe your question shows one of the big issues on the previous response. I will try to ellaborate it here.
Even if the resulting system works the same way as if I had chosen another language, technology or bought a complete solution, the process that took me there varies.
I can have my team improve their coding skills, tools-usage or have them learn a new technology while solving my companie's problem by implementing the solution. The result is the same, but the money spent, time requirement and my client's company intellectual growth depends on the technology I will choose.
If one believes that both lead to the same solution (I don't but there is no need to argue), there is still no need to show the key points that differ on implementing a solution using restfulie, java RMI, http based cruds or a BPM/BPEL solution as they are quite clear: the code, the tools, the languages in which the system is described, everything differs.
Regards | http://www.infoq.com/news/2009/11/restfulie-hypermedia-services | CC-MAIN-2014-52 | refinedweb | 2,367 | 60.24 |
How to share React hooks between components
. But If you want to share It with sibling one level components or a set of scattered components, you will be frustrated.
useBetween hook is the solution to your problem 😚
// App.jsx
import React, { useState, useCallback } from 'react';
import { useBetween } from 'use-between';const useCounter = () => {
const [count, setCount] = useState(0);
const inc = useCallback(() => setCount(c => c + 1), []);
const dec = useCallback(() => setCount(c => c - 1), []);
return {
count,
inc,
dec
};
};const useSharedCounter = () => useBetween(useCounter);const Count = () => {
const { count } = useSharedCounter();
return <p>{count}</p>;
};const Buttons = () => {
const { inc, dec } = useSharedCounter();
return (
<>
<button onClick={inc}>+</button>
<button onClick={dec}>-</button>
</>
);
};const App = () => (
<>
<Count />
<Buttons />
<Count />
<Buttons />
</>
);export default App;
useBetween is a way to call any hook. But so that the state will not be stored in the React component. For the same hook, the result of the call will be the same. So we can call one hook in different components and work together on one state. When updating the shared state, each component using it will be updated too.
If you like this idea and would like to use it, please put star in github. It will be your first commit!
betula/use-between
When you want to separate your React hooks between several components it's can be very difficult, because all context…
github.com | https://betula-dev.medium.com/how-to-share-react-hooks-between-components-6c58258df886?source=post_internal_links---------1---------------------------- | CC-MAIN-2021-43 | refinedweb | 221 | 52.7 |
Removing entry from @rray
Discussion in 'Perl Misc' started by Robert Valcourt, Dec 11, 2006.
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This tutorial is the the next step in Creating a test automation framework with C#, Selenium 3 and Nunit; after creating the reporting module in the previous tutorial, we can finally start writing an automated functional test with the test automation framework we’ve just created.
- You’re here→How
Before we begin creating a functional test, we’ll need to create a new project in the Solution, in order to have a separation between the framework’s project to the automated tests themselves.
There are two main reasons for separating the framework’s project and the tests’ project:
- Modularity of the code
- Easier to maintain a project that is dedicated to the tests
The Project will be called ‘AutomatedTestCases’. Next, change the name of the class while creating the project in Sanity.cs
It should appear as follows in the screenshot:
The automated functional tests will be executed on the blog’s page in the following url:
Open the file Sanity.cs and paste the following piece of code:
using NUnit.Framework; using OpenQA.Selenium; using Test; namespace AutomatedTestCases { [TestFixture] public class Sanity : AutomationCore { [Test] public void ClickContactUs() { Browsers.getDriver.FindElement(By.Id("menu-item-1296")).Click(); } } }
Lets get into more detail about the steps of the code above:
The first step is to include the project of the automation framework into the automated tests project. This is performed by adding ‘using Test;’
Afterwards, we’ll need to inherit from the AutomationCore, in order to make the framework and browser launch before executing any tests. Next, we’ll be starting with the automated tests.
Browsers.getDriver.FindElement(By.Id(“menu-item-1296”)).Click();
We are receiving the WebDriver from our Browser’s class and then in order to locate the element we’ll be using the FindElement method while passing the element’s Id. After we have the element we can click on it.
When the functional test is complete, the results will appear in the ‘Test Explorer’ window.
Obviously, the report we created has to appear in the path we’ve configured for it.
You have now completed the last step in designing your selenium testing framework, continue on to the Next tutorial where we’ll be covering the implementation of advanced capabilities when creating a test automation framework, and specifically: Page Object Pattern: Advantages & Implementation.
I would be happy to see your questions/ ideas / stories in the comments below!
I have created two projects as mentioned in the tutorials(1
Hi Asya,
Thanks for sharing such nice tutorials. There is minor refinement required as per my point of view. Your tutorials lack the complete steps defining like currently i am facing an issue which is…..I have configured two separate projects as mentioned in the tutorial and i am not able to start them because i don’t know what Output type required for each project, currently i have configured the output type of both projects as Class library.
While i tried to start the project i am facing an error i.e. there should be one executable project. Please help me, although i have marked the Automatedtestcases project as startup project.
After that i have marked the Output type of Automatedtestcases project as Windows Application and other one as Class library but system is doing nothing upon start.
Regards,
Muhammad Islam
+92-345-4057636
Hi Islam,
You don’t need to change the Output type of project.
You don’t need to run the projects with F5 (Run) like a regular project.
You should be running the tests from the Visual studio built in TestRunner.
AutomatedTestCases -> ClickContactUs right click and Run,
Thanks for the tutorial. I tried creating test cases in AutomatedTestCases project.
Browsers.getDriver.FindElement(By.Id(“ist-ib”)) this line throws me an exception “System.NullReferenceException: ‘Object reference not set to an instance of an object”.Could you please help me to sort this problem. | https://blog.testproject.io/2017/02/09/writing-functional-test/ | CC-MAIN-2020-10 | refinedweb | 651 | 53 |
By: Charlie Calvert
Abstract: A brief synopsis of creating JavaServer Pages in JBuilder. The article is supplemented with an overview of the JSP architecture.
In this article you will learn how to use JBuilder 9 to create a simple JavaServer Page (JSP) application. JSP is a Java based technology that allows you to create web
applications. JSP applications separate the
presentation and business logic layers of your application.
In other words, they employ a model-view-controller architecture
where the model is implemented in Java and the view is implemented in a form of HTML supplimented by a few simple JSP specific tags.
This article is designed to show how to create simple JavaServer Pages.
Subsequent articles will explore the subject in more depth.
The text begins with a quick start section that steps you through the process of creating a
JSP application using the JBuilder wizard. This quick start section ends with a few sentences describing how to trouble shoot the most likely errors which might
have occurred. These errors are likely to be related to the set up of a Tomcat server.
The middle of the article contains a brief overview of the JavaServer Pages technology. Finally, I will show you
how to modify the default JBuilder JSP application in a few simple ways so that you can begin to
make it do what you want.
Open JBuilder and create a new project by choosing File | New Project. The dialog containing the JBuilder New Project Wizard is shown in Figure 1. Click
finish on the first of the three pages of the wizard to accept all the defaults.
Choose File | New from the JBuilder menu. Turn to the Web page in the Object Gallery and select JavaServer Page, as shown in Figure 2. This option should be available in JBuilder Professional or above. There are five pages in the JSP wizard. For now, just accept all the defaults and click finish on the first page, as shown in Figure 3.
You have created a simple, but valid, JavaServer Page. To run the application in JBuilder, right click on jsp1.jsp in the project pane and choose Web run using jsp1 from the pop up menu, as shown in Figure 4. If all went well, your application should launch inside the JBuilder content
pane, as shown in Figure 5.
Figure 1: Click finish on this page to accept all the defaults
when creating a new project.
Figure 02: Selecting the JavaServer Page from the Object Gallery.
Figure 3: Click finish on the first of the five pages of the JSP wizard to
accept all the defaults.
Figure 4: Running your bean from inside JBuilder.
Figure 5: Running a JSP inside of JBuilder. Note that the tab at the bottom
of the IDE says Tomcat 4.0 and the text under content pane says.
Everything I've shown you so far is fairly straight forward. The only thing
that might have gone wrong is if you did not have the Tomcat server set up correctly.
Tomcat is one of several servers available which support JavaServer Pages and Java Servlets. It is a free and well implemented server produced by the Jakarta group. It can be found at.
The regular JBuilder 9 install should have place copies of Tomcat 3.3, 4.0
and 4.1 in a directory called JBuilder9/thirdparty, where JBuilder9
is the name of the directory where you installed JBuilder. For instance, on
my system the path to these files is c:binjb9thirdparty,
as shown in Figure 6.
Assuming that these files are correctly installed, you should next choose Tools
| Configure Servers and ensure that Tomcat is correctly configured.
As shown in Figure 7, the home directory field should
be set to the location of the Tomcat JDK, which on my systems is C:binjb9thirdpartyjakarta-tomcat-4.0.6-LE-jdk14.
The Main Class field should be set to: org.apache.catalina.startup.Bootstrap.
Figure 6: A directory listing showing the Tomcat servers automatically installed
with JBuilder.
Figure 7: The JBuilder Configure Servers dialog with Tomcat Server 4.0 selected.
Note the reference to the main class: org.apache.catalina.startup.Bootstrap,
and to the home directory, which in my case is: C:binjb9thirdpartyjakarta-tomcat-4.0.6-LE-jdk14.
JBuilder is designed to work only with a certain predefined set of servers. These servers are listed on the left side of the dialog shown in Figure 7. You can install your own copies of any of these servers, and use the Configure Servers dialog to point JBuilder toward them.
Most of the other problems you are likely to have when creating a JBuilder JSP would involve inserting incorrect code. In this example, however, JBuilder generated all the code for you automatically, and so it should be correct. As a result, I won't discuss any syntactic problems that might arise in your code.
JBuilder generated several chunks of code for you when you ran the wizard
Listings 1 and 2 show the source code for the two main files in this simple JSP application. They will be explained further in the text which appears below.
Listing 1: jsp1>
</body>
</html>
Listing 2: Jsp1Bean.java
package untitled12;
public class Jsp1Bean
{
private String sample = "Start value";
//Access sample property
public String getSample()
{
return sample;
}
//Access sample property
public void setSample(String newValue)
{
if (newValue!=null)
{
sample = newValue;
}
}
}
When creating your JSP, you can focus primarily on the two files shown in Listings 1 and 2.. It is these files, and one's like them, that you will modify when creating your application. However, you need to understand that a third file, not listed above, will be generated generated behind the scenes in order to make your application complete. You will never need to edit, and will often not even need to look at, this third file. However, it is the key to the entire JSP technology. After you have compiled and run your JBuilder project, the generated file will appear in your project hierarchy, in this location: classesGenerated Source.jsp.default.
I have implied several times in this section that there is connection between the JSP and Servlet technologies. It happens that a JSP is simply a particular kind of Servlet. Why then do I not begin by talking about Servlets first, and then start talking about Java Server Pages? It turns out that JavaServer Pages are much simpler to create than Java Servlets. In fact, JavaServer Pages can be seen as nothing more than a short cut to creating a Java Servlet. JSPs are designed to be a simple technique that makes it easy to create Servlets. It therefore makes sense to study JSP basics first, and then to move on to an understanding of Servlets.
Servlets are complicated not because they are difficult to build. In fact, Servlets are quite easy to create. However, Servlets have a tendency to encourage developers to mix their HTML and Java source code in a single file in a series of println statements:
out.println("<HTML><BODY><P>Data</P></BODY></HTML>");
Code of this type can be quite difficult to read if you are working with large amounts of HTML. Furthermore, you cannot easily modify the HTML without changing the source code of your servlet. JSPs are designed to rectify this entire problem by employing a model-view architecture.
In a JSP, you separate your code into two types of files. On one side, you have HTML files like jsp1.jsp. On the other side, you have Java source code, like that found in Jsp1Bean.java. Behind the scenes, the Tomcat server will automatically generate a third file whenever you modify your source. This third file is true Java Servlet, and contains a mixture of Java source code and HTML. The whole point of the JSP architecture is to hide the details of this file from you.
In closing this section, I want to point out there is nothing in the JSP specification which prevents you from putting Java source code in your HTML based jsp file, nor from putting HTML in your Java based beans. The architecture is designed to encourage you to make a clean separation between your presentation layer and your program logic. However, it does not enforce this architecture through a set of immutable syntactical rules. I want to emphasize, however, that your success in working with this paradigm is in large part dependent on your willingness to keep your Java code in one place and your HTML code in another. If you give in to the temptation to mix the two, then you will be forfeiting a major benefit of this technology.
By this stage you should understand how to create a JSP with JBuilder, and you should have caught some glimpses of the general theory behind the JSP architecture. In future articles, I will expand on this short, general introduction to this extensive topic. To wrap up this article, let's modify the project slightly.
A modified version of the original JSP page is shown in Listing 3.
Listing 3: A single line has been added to the code shown in Listing 1. This single line of code prints out the value of the property called sample which is found in the Java bean shown in Listing 2.
<html>
<head>
<title>jsp1</title>
</head>
<jsp:useBean
<jsp:setProperty
<body bgcolor="#ffffff">
<h1>JBuilder Generated JSP foo</h1>
<p>Data from the bean: <jsp:getProperty<p></body>
</html>
<p>Data from the bean: <jsp:getProperty<p>
</body>
</html>
First notice the general structure of the file. The HTML, HEAD, BODY, and H1 tags are simple HTML rendered without modification. The first line that looks unusual is this one:
<jsp:useBean
This code uses a simple XML format to render a JSP tag. Notice the reference to the jsp namespace, and to the useBean tag: jsp:useBean. In this case the useBean tag has three attributes: id, scope and class. The class attribute specifies the name of the bean that you want to use. The scope attribute specifies the range over which this tag's definition will be available. In this particular case, the the definition is said to hold true across the entire session. Sessions will be defined in later articles in this series. Finally, the id attribute defines a means of referencing this object in other parts of your code. The id has much the same functionality here that an identifier or variable declaration would have in a standard programming language such as Java, Pascal or C. The end result of this statement is that we have an id called jsp1BeanId that references an instance of the Java bean shown in Listing 2.
After this modification, the application appears as it does in Figure 8. Notice the string in the middle of the output window that reads "Data from the bean: Start Value." The value before the colon was generated by the HTML in the presentation layer, and the value after the colon was generated by the Java code in the default bean generated by the JBuilder wizard.
Figure 8: The JSP now accesses the default property in the bean created by JBuilder when you ran the wizard. This property returns the string "Start Value."
Here is the part of the jsp page that retrieves the data from the bean: <jsp:getProperty Notice that this code is in XML format. A namespace called jsp is declared, and then there is a reference to the getProperty tag. In this instance, the tag supports two attributes called name and property. The name field specifies the name of the object we want to call, and the property field specifies the property on that object that we want to reference. The name of the object to be called is referenced via the id property of the jsp:useBean tag discussed above.
To understand this better, take a look at the Java bean itself, which is shown in Listing 2:
public class Jsp1Bean
{
private String sample = "Start value";
// code omitted here
}
Here you can see that Jsp1Bean has a single property called sample. If you look up at listing two, you will see that there are public getter and setter methods for accessing this property. By now you should be able to parse the getProperty tag: <jsp:getProperty. The code simply references the sample property of an instance of the Jsp1Bean class.
Let's add three more lines of code to our jsp file:
<form action="jsp1.jsp" method="post"><input type="text" name="sample" value="<jsp:getProperty"><input type="submit">
After adding this code, at run time the application appears as it does in Figures 9 and 10. The complete source for the modified jsp file is shown in Listing 4.
Figure 9: The JSP as it appears in the content pane when first run.
Figure 10: The JSP as it appears after the user has modified one of the fields of the Java Bean by typing in the input field. Note that the text above the submit button which accesses the sample property has been changed. The change occurred when the user pressed the submit button.
Listing 4: The modified source to the>
<p>Data from the bean: <jsp:getProperty<p>
<form action="jsp1.jsp" method="post">
<input type="text" name="sample" value="<jsp:getProperty">
<input type="submit">
</body>
</html>
The new code adds a form to the HTML file. The form references the page in which it appears: action="jsp1.jsp." In other words, a click on the submit button in the form will end up modifying this page, and not some other page. Included in the form are an input field and a submit button. Notice that the value for the input field is supplied by the sample property in our Java bean. Pressing the submit button changes that value.
In effect, the submit button completes our model-view architecture by adding a controller to it. The controller part of the model-view-controller architecture is the part that provides the communication between the model and view portions of the architecture. When the user clicks on the submit button that link is completed, and code inside the Java bean is called. This is a very simple example of how you can use an HTML file to tap into the logic supplied by Java application.
Please remember that the HTML will be on the client side, and the Java class will be back on the server. In effect, the relationship between the HTML and the Java server code is the same as that between an HTML file and a CGI application. In particular, there is normally going to be a noticeable delay while the information in the HTML file is sent back to the server, processed by the Java Servlet code, and sent back to the user in the form of a new HTML page. In that sense, this architecture is the same as that found in a CGI application. The advantages of this technology over CGI technology are two fold:
1) There is a very clean and intuited relationship between the HTML based JSP and the logic back on the server.
2) The code on the server is kept in memory at all times, so there is no overhead of the type one usually finds when launching an instance of a CGI application. A delay will occur, however, the very first time the application is accessed. At that time, the Tomcat server combines the JSP page and the beans on the server to generate the source for a Java Servlet. It then compiles the Servlet and loads it into memory. There it will stay until the source is modified or the server is shut down.
The end result is a very fast, very powerful, web application that is easy to build and at least potentially easy to maintain. That ease of maintenance is in large part dependent on the developers willingness to maintain a separation between the presentation and logic layers of the JSP.
This article has introduced the main concepts on which the JavaServer Pages architecture is based. It has also shown you how to use JBuilder to easily create a sample JavaServer Page.
A major focus of this article was to show you the basic syntax of a simple JSP application. While exploring that syntax, you learned that the JSP architecture is based on the Java Servlet technology.
Another primary focus of this article was to explain how the JSP technology supports the model-view-controller architecture. In particular, you have seen that a file with a jsp extension contains HTML and forms the presentation portion of your application. A second file, containing Java code, contains the logic for your application. Of course, a large web application will likely contain many HTML and Java files. However, the basic architecture on which those applications is based has been introduced in this article. Future articles in this series will focus on the many features found in a JSP or Servlet based application.
I will close with a warning. This article has given you just enough information to make you dangerous. Future articles will give you the information you need to correctly architect web applications that are robust and maintainable.
Server Response from: SC2 | http://edn.embarcadero.com/article/31847 | crawl-002 | refinedweb | 2,889 | 62.68 |
Hi,
I'm stuck trying to find a solution to this problem. Its a question taken from an exam for an interview.
I have this object model:
Department: DepartmentId, Name
TeacherTeacherId, FirstName, LastName, DateOfBirth, AnnualSalary, DepartmentId
CourseCourseId, Name, TeacherId, DepartmentId
Student: StudentId, FirstName, LastName, DateOfBirth, AverageScore, DepartmentId
Department has a 1 to many relationship with Teacher, Student and Course.
Teacher has a 1 to many relationship with Course
Student has a many to many relationship with Course
In a previous question I asked on here I asked how to create an interface between Student and Teacher called IPeople to highlight all commonality. I was pointed in the right direction and came up with
using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace School.Code { public interface IPeople { string FirstName { get; set; } string LastName { get; set; } Int64 DepartmentId { get; set; } DateTime DateOfBirth { get; } } }
I then needed to create an IENumerable value of IPeople which I did using
public IEnumerable<IPeople> GetAllIPeople() { foreach (IPeople person in GetAllTeachers()) { yield return person; } foreach (IPeople person in GetAllStudents()) { yield return person; } }
How ever I am stuck with the next part of this.
The question is. Write method to get all IPeople for a Course - Write a method in the SchoolManager to get all IPeople for a particular Course. Your method should return an IENumerable of IPeople and make use of the existing GetAllIPeople method you've just written in the SchoolManager.
Now at first I thought this would be easy and should just use .where(c => c.CourseId == cId) where cId was passed into the method. How ever CourseId isnt in the interface as its not a common property between Student and Teacher. I do know because of the relationships between the objects that the Course, Student and Teacher will all share the same DepartmentID.
I am however completely lost as to how I produce an answer to this question. If anyone can point me in the right direction I would be grateful. | https://www.daniweb.com/programming/software-development/threads/366720/filter-ienumerable-of-interface-with-property-of-class-outside-of-interface | CC-MAIN-2017-34 | refinedweb | 332 | 53.31 |
From: Alex Chovanec (achovane_at_[hidden])
Date: 2004-09-09 21:29:56
Hello,
A while back, I proposed a template metafunction called 'is_iterator', but
the consensus seemed to be that it was not feasible from an implementation
standpoint. At Jonathan Turkanis' suggestion, I went ahead and implemented
the less ambitions 'is_dereferenceable', along with two other metafunctions:
Requirements:
Given t of type T &, if the expression *t is not well-formed, then
it must
neither be ambiguous nor violate access.
Description:
is_lvalue_dereferenceable<T> - true if *t is well-formed and an
lvalue
is_value_dereferenceable<T> - true if *t is well-formed and non-void
is_dereferenceable<T> - true if *t is well-formed
I would like to offer these up for inclusion in boost, whether in namespace
boost or in boost::detail. (presumably the latter, since that's where the
similar 'is_incrementable' is found).
I have posted the source for these metafunctions along with a unit test in
the YahooGroups Files section in a folder called 'is_dereferenceable'.
Please let me know if these are of interest to anyone.
Alex Chovanec
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/2004/09/71700.php | CC-MAIN-2020-45 | refinedweb | 199 | 53.41 |
at least I think it is called "clearing the buffer"...
so, this is a menu driven program. If the first option is chosen, you can input a number and it will store the number in a string. Then a "for" loop reads each character from that string and displays each character. After this is done the menu comes up again and you can repeat that over and over. When the menu comes up, you can also choose a second option. This option reads from an external file. It reads & displays each line to the end. When it is done, the menu comes up ready to do the next command. Here is the problem: If I select the second option again from the menu, it won't re-read the same file starting from the top. It just re-displays the last thing stored in memory.
Is it possible to be able to re-read that same file over and over using the menu?
The external file I used has three lines of numbers (shown below).
Code:#include <iostream> #include <fstream> #include <cstdlib> #include <cstdio> #include <string> using namespace std; #define inFile "file.txt" int main () { int menuNumber; int next; ifstream inStream; string number; char ch1; do { cout << "Enter 1 to type in a number" << endl; cout << "Enter 2 to get number list from an external file" << endl; next = 0; cin >> menuNumber; switch (menuNumber) { case 1: cout << "Type in number: "; cin >> number; // option to read in string if typed in break; case 2: inStream.open(inFile); inStream >> number; // option to read in first string from batch file break; } if(menuNumber == 1) cin.ignore(100, '\n'); while(next != 1) { for(int i=0;i<(number.length());i++) { number.at(i); //This "for" loop reads every character from string "number" ch1 = number.at(i); cout << ch1; } cout << endl; if (menuNumber == 2) inStream >> number; //if reading from batch file, it reads the next line else if (menuNumber == 1) next = 1; if((menuNumber==2)&&(inStream.eof())) { cout << endl; next = 1; } } cout << endl; if (menuNumber == 2) inStream.close(); }while(1!=2); }
here is what my external file / batch file from notepad contains:
Code:1142 6851 6981 | https://cboard.cprogramming.com/cplusplus-programming/121503-clearing-buffer.html | CC-MAIN-2018-05 | refinedweb | 360 | 81.63 |
Today's post is prompted by this question from Reddit:
How do I calculate the distribution of the number of selections (with replacement) I need to make before obtaining
k? For example, let's say I am picking marbles from a bag with replacement. There is a 10% chance of green and 90% of black. I want
k=5green marbles. What is the distribution number of times I need to take a marble before getting 5?
I believe this is a geometric distribution. I see how to calculate the cumulative probability given
npicks, but I would like to generalize it so that for any value of
k(number of marbles I want), I can tell you the mean, 10% and 90% probability for the number of times I need to pick from it.
Another way of saying this is, how many times do I need to pull on a slot machine before it pays out given that each pull is independent?
Note: I've changed the notation in the question to be consistent with convention.
from __future__ import print_function, division import thinkplot from thinkstats2 import Pmf, Cdf from scipy import stats from scipy import special %matplotlib inline
Solution¶
There are two ways to solve this problem. One is to relate the desired distribution to the binomial distribution.
If the probability of success on every trial is
p, the probability of getting the
kth success on the
nth trial is
PMF(n; k, p) = BinomialPMF(k-1; n-1, p) p
That is, the probability of getting
k-1 successes in
n-1 trials, times the probability of getting the
kth success on the
nth trial.
Here's a function that computes it:
def MakePmfUsingBinom(k, p, high=100): pmf = Pmf() for n in range(1, high): pmf[n] = stats.binom.pmf(k-1, n-1, p) * p return pmf
And here's an example using the parameters in the question.
pmf = MakePmfUsingBinom(5, 0.1, 200) thinkplot.Pdf(pmf)
We can solve the same problem using the negative binomial distribution, but it requires some translation from the parameters of the problem to the conventional parameters of the binomial distribution.
The negative binomial PMF is the probability of getting
r non-terminal events before the
kth terminal event. (I am using "terminal event" instead of "success" and "non-terminal" event instead of "failure" because in the context of the negative binomial distribution, the use of "success" and "failure" is often reversed.)
If
n is the total number of events,
n = k + r, so
r = n - k
If the probability of a terminal event on every trial is
p, the probability of getting the
kth terminal event on the
nth trial is
PMF(n; k, p) = NegativeBinomialPMF(n-k; k, p) p
That is, the probability of
n-k non-terminal events on the way to getting the
kth terminal event.
Here's a function that computes it:
def MakePmfUsingNbinom(k, p, high=100): pmf = Pmf() for n in range(1, high): r = n-k pmf[n] = stats.nbinom.pmf(r, k, p) return pmf
Here's the same example:
pmf2 = MakePmfUsingNbinom(5, 0.1, 200) thinkplot.Pdf(pmf2)
And confirmation that the results are the same within floating point error.
diffs = [abs(pmf[n] - pmf2[n]) for n in pmf] max(diffs)
8.6736173798840355e-17
Using the PMF, we can compute the mean and standard deviation:
pmf.Mean(), pmf.Std()
(49.998064403376738, 21.207570382894403)
To compute percentiles, we can convert to a CDF (which computes the cumulative sum of the PMF)
cdf = Cdf(pmf) scale = thinkplot.Cdf(cdf)
And here are the 10th and 90th percentiles.
cdf.Percentile(10), cdf.Percentile(90)
(26, 78) | https://allendowney.blogspot.com/2016/05/binomial-and-negative-binomial.html | CC-MAIN-2018-51 | refinedweb | 613 | 52.29 |
EN Activate your Warranty Plan and gain access to amazing promotional offers and after-sales service. See Page 2 TY N WARRA Y EA S R CS 450 OWNER’S MANUAL CAUTION! Read, understand and follow all Safety Rules and Operating Instructions in this manual before using this product. Save this manual for future reference. 01 TY N WARRA Y EA S R WARRANTY ACTIVATION Activating your warranty is required for coverage of warranty program and also for access to customer service for immediate response to your needs. Receive exclusive promotional offers. Warranty Conditions: See Page 17. ACTIVATE ONLINE, EMAIL COMPLETED ACTIVATION FORM VIP MEMBERSHIP CARD WARRANTY ACTIVATION ACTIVATE WARRANTY ONLINE : DUALSAW MODEL / SERIAL NO.: 1234 5678 9101 00 ACTIVATION REQUIRED FOR AFTER SALES SERVICE & SUPPORT. ACTIVATION NECESSAIRE POUR SERVICE APRES-VENTE ET GARANTIE ACTIVACIÓN NECESARIA PARA SERVICIO AL CLIENTE Y GARANTÍA ATIVAÇÃO NECESSÁRIAS PARA SERVIÇO AO CLIENTE E GARANTIA O First Name PT NA IO Last name Order Number / Invoice Number R O LF E-mail address ER M TO US Purchase date LC Serial number of your machine JM VIP Member Card Number Send Completed Form by Email: [email protected] Warranty Activation Online: 02 EN TABLE OF CONTENTS Warranty Activation Safety instructions and warnings Machine components Proper usage General safety instructions 02 04 04 05 05 Special safety instructions Fitting the support handle Operation Instructions for Cutting Various Cross Sectional Material Removal / Replacement of Saw blades Lubrication Maintenance and care Troubleshooting Technical data Repairs & Environmental protection Limited & Extendable warranty Optional Blades and Accessories Declaration of Conformity (DoC) 07 10 10 13 14 15 15 16 16 16 17 20 22 03 SAFETY INSTRUCTIONS AND WARNINGS This machine complies with the prescribed safety regulations for electrical machines. Read the operating manual carefully before using the machine. Incorrect use may result in damage or injury to people and property. People who are not familiar with the manual must not be permitted to use the machine. Keep the operating manual in a safe place. Children and young people must not be permitted to use the machine. MACHINE COMPONENTS HANDLE WAX STICK HOLDER ON/OFF SWITCH SAFETY HOOD CUTTING BLADE 04 SPINDLE LOCK EN PROPER USAGE • The machine is designed for cutting metal, stone and ceramics using the appropriate blades and accessories. • If it is not used for the purpose for which it is designed or if any modifications are made to the machine, the manufacturer cannot accept any liability. • Also refer to the safety instructions, the installation and operating manual, and the general accident prevention regulations. GENERAL SAFETY INSTRUCTIONS WORKPLACE • Keep your workplace clean and well lit at all times to prevent accidents. • Do not use electric machines in the vicinity of flammable liquids or gases, or in wet or damp environments. If you fail to follow this instruction, there is a risk of fire or explosion. • Do not leave the machine running without supervision. • Do not use the machine if you are tired or lack concentration, or your reactions are impaired due to the consumption of alcohol or medication. • Inattentiveness can cause serious injuries. ELECTRICAL SAFETY • The mains voltage must be identical with the details on the machine’s labeling. • Avoid physical contact with earthed parts, for example pipes, radiators, stoves, refrigerators, etc. to prevent receiving an electric shock. • Never carry the machine by its cable. Only pull the cable out of the socket using the plug. Always protect the cable from oil, heat and sharp edges. Damaged cables can cause an electric shock. • Before starting work, check the machine and the mains cable for signs of damage. • When you connect the mains plug, ensure that the main switch is not locked in its ON position. • For outdoor use, use only extension cables that have been specifically approved for this purpose. • If you use a cable drum, extend the whole cable to prevent the cable from overheating. Min. wire cross-section 1.5 mm². • For working outdoors the socket must be fitted with a residual current-operated circuit-breaker (RCCB). • Pull the plug when the machine is not in use or if you are making adjustments. • The cable should always be guided to the rear away from the tool. 05 PERSONAL SAFETY • • • • • • • • • • • • • • Do not wear loose-fitting clothing or jewelry. Ensure that you have a safe place to stand and that you wear non-slip shoes. Wear a hair net if you have long hair. Loose-fitting clothing, jewelry and long hair may become caught in moving parts. Always wear safety goggles. Following this instruction will reduce the risk of serious injuries. Always wear a face or dust protection mask. Following this instruction will reduce the risk of serious injuries. Always wear ear protection. Following this instruction will reduce the risk of serious injuries. Do not distract anybody working on the machine. You may cause them to lose control of the tool. Do not use the machine if its ON/OFF switch is defective. An electric tool that cannot be switched ON or OFF is dangerous and must be repaired. Always switch on the machine before making contact with the material. Remove wrenches and setting tools before you switch on the machine. Do not overload the machine. If the speed falls, reduce the load on the machine or switch it off. Using suitable electric tools you can work more safely and better within the specified capacity range. Secure the work pieces to prevent them moving with the machine, for example using a clamp or a vice. Do not cut any work pieces that are too small to secure. If you hold the work piece with your hand, you will not be able to operate the tool safely. Keep electric tools out of the reach of children. CAREFUL HANDLING AND USE OF ELECTRIC TOOLS • Keep the tools clean and functional to enable you to work better and more safely with them. • Use only accessories that have been recommended by the manufacturer. • Never cut, drill or saw into concealed areas which may contain electric cables, gas or water pipes. Use suitable detection equipment to locate these cables and pipes. • Do not cut materials that contain asbestos. • Do not cut work pieces which are thicker than the maximum cutting depth of the cutting blade. • Conduct an operating test of at least 30 seconds without loading the machine. • Always switch off the machine and allow it to reach a standstill before you set it down. SPECIAL SAFETY INSTRUCTIONS Never reach into the sawing area or into the area surrounding the saw blade. Always hold the handle or motor casing with your other hand. If you use both hands to hold the saw it will reduce the risk of injury. Ensure that you hold the saw tightly at all times so 06 EN that you do not lose control of it. Never stand in line with the saw blade. Always stand to the right or left of the saw blade. Any recoil may result in the saw jumping backwards. Never reach below the work piece. The safety hood over the saw blade does not offer any protection from the saw blade underneath the work piece. Never remove sawn pieces whilst the saw blade is still turning. Before using the saw ensure that the pivot safety hood is in good working order. The pivot safety hood must move freely and must close immediately. The pivot safety hood must never be locked in its open position. If you have dropped the saw by accident, check the pivot safety hood for signs of damage and ensure that it is in good working order. To check this, open the pivot safety hood with the handle and ensure that the safety hood moves freely and that it does not touch the saw blade or other parts at any cutting angle or cutting depth. Check the condition and function of the return spring on the pivot safety hood at regular intervals. The saw must not be used if the spring and the safety hood are not in good working order. These components must be repaired before the saw may be used again. Resin deposits or dirt accumulations can cause the pivot safety hood to move more slowly. In this case, disconnect the machine from the mains supply, remove the saw blade and clean the safety hood and the hood area. The pivot safety hood may only be opened manually for special cuts, such as submersed (plunge) or shifting cuts. In this case open the pivot safety hood using the appropriate handle. The pivot safety hood must be released again as soon as the saw blade has engaged in the material. The use of the automatic pivot safety hood function must be used for all other cuts. After you release the ON/OFF switch it will take a little time before the saw blade reaches a standstill. Before you put down the saw ensure that the pivot safety hood is completely closed and that the saw blade has reached a standstill. An unguarded, freely turning saw blade may cause the saw to catapult out of control. Never hold the work piece you wish to saw in your hand or place it on your leg. Always place work pieces in a vice or clamp. Always hold the machine using the insulated handles provided whilst it is in use. This will prevent the risk of a fatal electric shock if the saw blades come into contact with live cables. Never use normal carbide metal blades. Twin saw blades have a different shape. Normal saw blades will not fit the fastening device on the saw and may result in serious injuries. Never use damaged or non-fitting washers or bolts to fit the saw blade. Washers, bolts and flanges have been specially designed for this saw to ensure perfect operating safety and performance. Never move or carry the saw to a new location whilst it is running. If it comes into contact with your clothing there is a possibility that the pivot safety hood will open. Contact with the rotating saw blade can cause extremely serious injuries. Depending on how and for what purpose the saw is used, the service life of the ON/OFF switch may be shorter than that of the saw itself. If the switch breaks whilst the saw is in use, you may find that it is no longer possible to switch the saw off again. In both cases pull the mains plug out of the socket without delay. The saw must not be used again until it has been repaired by an expert. Always use a riving knife for sawing large panels. Remember at all times that it is possible for the saw to recoil. If the saw jams and is catapulted back at the user, this is known as a recoil (or kickback). Immediately release the switch if the saw jams or the saw blade becomes stuck. Do not use force to remove the saw from the material. Never pull the saw out of the material whilst the saw blade is 07 still moving. Do not use bent or torn saw blades. Do not solder or weld saw blade cracks or weld support parts with carbide metal teeth. Never slow down or stop the saw blades by exerting lateral pressure on them. Never use carbide metal-tipped saw blades with a residual height or thickness of less than 1 mm. WARNING Never use saw blade types other than those specified for use. This counter rotating twin blade saw is fitted with special saw blades. The use of other saw blades is not safe and may result in serious accidents. Always ensure that the saw has reached its full speed before bringing it into contact with the material. If the saw is brought into contact with the material before it has reached its top speed, it may cause very serious injuries. Always ensure that both saw blades engage simultaneously into the work piece. If the saw engages in a work piece on one side, there is a risk that the saw will suffer unexpected recoil and cause serious injury. For angled cuts, do not position the saw at an angle so that only one blade engages in the work piece, but instead position it on the top so that both blades engage at the same time. The side areas of the saw blades are not designed for cutting. When making cross cuts, therefore, ensure that the weight of the saw is not supported on the lower saw blade. Instead support the saw by raising it slightly and securing the work piece in a clamp or vice. This will prevent unexpected recoil. When the machine is working it will generate dust which may be harmful, inflammable or explosive. Take suitable safety precautions. Wear a dust protection mask. Ensure that there is good ventilation in the workplace. RECOIL (KICKBACK) – CAUSES AND PREVENTION Incorrect use and/or incorrect working methods or conditions may cause the saw to recoil. The following action can be taken to prevent recoil. Always hold the saw with two hands. Adopt a posture in which your body and your arms can withstand the recoil force. In the event that the saw blade becomes stuck in the work piece or a cut is interrupted for any reason whatsoever, release the ON/OFF switch immediately and leave the saw in the work piece until the saw blade has reached a complete standstill. Never take the saw out of a work piece whilst it is still running. This may cause the saw to recoil. Identify and rectify the cause of the saw becoming stuck. When you reposition the saw on the material, the saw blade must be placed in the centre of the cut. Ensure that the saw’s teeth do not engage in the material to the side of the cut. This may cause the saw to recoil. When sawing large panels please note that they will bend slightly under their own weight and this may cause the saw blades to become blocked, which can thus result in recoil. Support these panels using suitable equipment on both sides of the panel. Place the supports near the line along which you want to cut and close to the edge of the panel. Never use damaged or blunt saw blades. As the saw blade wears, the kerfs created by 08 EN this saw blade will become too narrow, which will cause excessive friction resulting in the saw blade jamming and possibly recoil. If you wish to cut into existing walls or other concealed areas, proceed with special care and caution. Since you cannot know what is behind the area you are cutting, you must anticipate recoil to occur at any time. ADDITIONAL INSTRUCTIONS FOR HANDLING COUNTER-ROTATING DUAL BLADE SAWS You must have read and understood all the instructions in this manual and you must also follow them. Also make sure that any other users receive a copy of this manual and your own instructions and that they have read and understood them. Any failure to follow the instructions may result in electric shocks, fire and very serious injuries. Check the cable and the ON/OFF switch on the tool at regular intervals. Have the cable and/or switch repaired immediately in an authorized repair center if it / they are damaged. Following this instruction will reduce the risk of serious injuries, electric shocks and fires. Check the saw at regular intervals for signs of damaged parts and to ensure that it is in perfect working order. Do not use the saw if it is damaged or malfunctions. Damage and malfunctions must be repaired / rectified immediately. Check at regular intervals whether moving parts are correctly aligned and are not seized. Also check that no parts are broken and that there are no other problems with the tool. Damaged parts, particularly the safety hood, must be repair by an authorized workshop. Following this instruction will reduce the risk of a possible electric shock, fire or serious injury. ABOUT THESE INSTRUCTIONS Cutting a work piece with this saw can release the chemicals contained therein which may be potential causes of cancer, congenital defects and other reproductive problems. Examples of these chemicals include the following: • Lead from coatings • Crystalline quartz from bricks, cement and various masonry products • Arsenic and chromium from chemically treated timber • How high your personal risk is dependent on how often you work with such materials. • How to reduce your personal risk when working with harmful dust: • Always work in a well ventilated area. • Use a certified dust protection mask which has been specially developed to filter microscopic particles. • Always remember than when you use this saw foreign bodies may get into your eye which can cause serious eye damage. You must therefore always wear certified goggles with side protection or sealed goggles. If necessary put on a face protection mask before you start to work with the saw. • Please note that whilst the saw is in use the gearbox head can become very hot. You should therefore not touch the gearbox head. 09 FITTING THE ADDITIONAL HANDLE The handle can be fitted on either the left-hand side or right-hand side of the saw. Secure the handle using the screw supplied. OPERATION SAW BLADES Keep the saw blades clean and sharp at all times. Ensure that the saw blades are fitted correctly. A blunt saw blade will reduce the cutting capacity, place additional strain on the saw’s motor and increase the risk of recoil. Ensure that you always have spare saw blades available. In the event that resin and pitch residue build up on to the saw blade, the blade’s speed will be reduced. Remove these residues straight away using special resin removal products, or hot water. Never use petrol to remove these residues. Never use normal saw blades in this saw. This double blade saw is fitted with specially designed saw blades. The use of other saw blades is not permitted and may result in very serious injuries. PIVOT SAFETY HOOD Never make any modifications to the pivot safety hood fitted on the saw. This hood provides you with safety and protection. Before you use the saw check the pivot safety hood to ensure it is in perfect condition and in perfect working order. The saw must not be used if the pivot safety hood is damaged or closes slowly or requires a great deal of effort to close. In this case have the safety hood repaired or replaced without delay by an authorized workshop. If you have dropped the saw, check the pivot safety hood and the fence edge for all cutting depths for signs of damage. If the pivot safety hood moves freely and returns straight away to its closed position, it is in correct working order. If the pivot safety hood cannot be closed without problems, the saw must immediately be withdrawn from use. It must be repaired by an authorized workshop before being used again. Always leave the safety hood in its prescribed working position when you are working with the saw. 10 EN blade. Any contact between parts of your body and the rotating saw blade will result in very serious injuries. SAWING Always use the saw as set out in these instructions. Always support the work piece near the cut (for example using a saw stool or the like). Always secure the work piece so that the cut is on your side. Always secure the work piece in a suitable device. The work piece must not be able to move whilst it is being sawn. Draw the line of the cut in pen on the work piece before you start the cut. Position the front of the saw blades on the actively supported part of the work piece. Never position the saw on the part of the work piece which will fall after the cut has been completed. Always keep the cable away from the sawing area. Route the cable so that it cannot become caught up on the work piece. Maintain concentration at all times when using the saw and keep it under control. This will make the sawing work easier and above all safer. If you lose your concentration whilst using the saw and thus lose control of the saw, it may cause accidents and serious injuries. In the event that the cable becomes caught on the work piece whilst you are sawing, release the ON/OFF switch immediately. Immediately pull the plug out of the socket, check the cable for signs of damage and then route it so that it can no longer become caught on the work piece. In the event that the cable has been damaged, the saw must be withdrawn from use straight away. A damaged cable may result in serious injuries or even death. Before you use the saw again have the cable replaced by an authorized workshop. Push the ON/OFF switch forwards to switch on the saw. Release the ON/OFF switch again to switch off the saw. After you have switched on the saw, wait until the saw blades have reached their top speed before you place them on the work piece. If the saw blades are brought into contact with the work piece before they have reached their top speed, this can result in recoil and serious injuries. Guide the saw calmly and with uniform pressure through the work piece as you are using it. If you exert excessive pressure it will result in irregular cutting results and will also reduce the service life of the saw blades and saw. It may also cause recoil. blade. Any contact between parts of your body and the rotating saw blade will result in very serious injuries. When you have sawn through the work piece and you then raise the saw off the work piece, the saw blades will be exposed until the pivot safety hood closes. Ensure that the safety hood is completely closed before you put down the saw. When cutting metals such as aluminium, copper, stainless steel or cast iron, always use the 11 integral lubrication device since these material tend to adhere to the saw blades. When sawing these materials, pay very close attention to ensuring that the direction of the saw is always parallel to the saw blade since otherwise the saw blade will become so hot that it could burn or the damage the saw teeth. FEED The feed speed is the speed at which you push the saw blades through the material. The correct speed depends on the hardness and thickness of the material. Finding the correct feed speed: If the feed speed is too low, the saw blades will only exert pressure on the material instead of cutting through it. The result of this is that the edges of the saw blades slip which results in wear on the material. This then results in poor cutting quality and excessive wear on the saw blades. If the feed speed is too high there is a high risk that the cut will crack. These cracks generally tend to increase in size so that ultimately the material fractures, which may cause very serious injuries. 12 EN INSTRUCTION FOR CUTTING VARIOUS CROSS SECTIONAL MATERIALS FLAT SCRIP ALUMINUM /COPPER WAX STICK 90° SQUARE TUBE U PROFILE ROUND TUBE THING SHEET METAL 90° 10 MM 13 REMOVAL / REPLACE OF SAW BLADES 01 Press and hold button. 03 Open blade guard and remove blade FACE 1 first and blade FACE 2 second. 02 Holding button. Affix key tool on bolt. Unscrew and remove bolt by rotating in counter-clockwise direction. 04 To replace blades, affix new blade FACE 1 first and blade FACE 2 second. Important Note: Blade sets and labeling vary slightly, and may be labeled FACE 1 and FACE 2, or FACE A and FACE B. 14 EN LUBRICATION • The blades are equipped with “Dry Cut” teeth. As a rule these need not be lubricated. However, in extreme cutting conditions, cutting paste (wax) can be applied. • When cutting Aluminium /Copper/ Stainless steel and cast iron, the lubricating device must always be used. • We recommend that you buy cutter paste in rod form, available from your nearest dealer. • Insert a cutter paste rod. 01 02 03 IMPORTANT! The lubricating paste is added by turning the feeder wheel. Dosage as required. MAINTENANCE AND CARE Pull the mains plug out of the socket and allow the saw to cool down before starting any assembly, modification and servicing work. This will prevent the saw being started by accident. Use a damp cloth to clean the plastic parts. Do not use cleaning products, solvents or sharp objects. Clear the ventilation openings and moving parts from deposits of dust at regular intervals using a soft brush or paintbrush. Resin and other substances that accumulate on the sides of the saw blades can cause the blade to overheat which can make the blade bend or even crack. You should therefore always clean the saw blades with great care. Never scrape the saw blade clean using hard objects. Remove these residues using special resin removal products, hot water or kerosene. Never use petrol to remove these residues. After you have cleaned the saw blade or when the saw is not in use, the blades should be treated with an anti-corrosion product. Store the saw in a dry place. We do not recommend that you use this saw to cut glass fibre products, plasterboard, filling compound or plastic for lengthy periods of time as a result of the high friction caused by these products. If you nevertheless have to cut these products, we recommend that you stop at regular intervals and clean the machine with a jet of compressed air. Always wear safety goggles with side protection or sealed goggles and a dust protection mask when using a jet of air to clean dust deposits off the saw. The bearings in this saw are lubricated for the entire service life of the saw. No other lubrication is required. The use of an extension cable may result in a slight loss of power. To prevent this loss of power and excessive heat generation in the extension cable, you must use a cable with a sufficiently large cross-section. 15 TROUBLE SHOOTING PROBLEM CAUSE SOLUTION Very high spark generation 1. Damaged teeth 2. Feed speed is too slow 3. Blunt teeth 1. Replace blades 2. Increase feed speed 3. Replace blades A lot of wear in sections 1. Feed speed is too fast 2. Damaged teeth 3. Blunt teeth 4. Not cutting parallel or perpendicular to work surface 1. Reduce the feed speed 2. Replace blades 3. Replace blades 4 Hold saw parallel to work surface Blades are breaking 1. Damaged teeth 2. Feed speed is too fast 3. Blunt teeth 4. Blades have buckled 5. Blades have burned out 1. Replace blades 2. Reduce feed speed 3. Replace blades 4. Replace blades 5. Replace blades TECHNICAL DATA DESCRIPTION Mod. CS 450 / BLACKSTAR 115 Motor Power 1050W Voltage EU 230V / 50Hz Voltage UK 240V / 50Hz Voltage US 120V/ 60Hz Blade Diameter 115mm No Load Speed 5500RPM Depth of Cut (Max.) 25mm REPAIRS & ENVIRONMENTAL PROTECTION Use only the accessories and spare parts recommended by the manufacturer. If the machine suffers a failure despite our quality controls and your care, have repair work carried out only by an authorised electrician. DISPOSAL OF OLD ELECTRICAL & ELECTRONIC EQUIPMENT Do not simply dispose of the machine, accessories and packaging in the dustbin, instead send it for recycling. This small effort will help our environment. For more detailed information about recycling of this product, please contact your local Council, your household waste disposal service, 16 EN or the place where you purchased the product. This symbol on the product or on its packaging indicates that this product (including batteries). LIMITED & EXTENDABLE WARRANTY WARRANTY/REPAIR Our Priority is striving to provide you the best customer service. We guarantee to address your problem, question or concern within 24/48 hours from receipt during normal business hours. Important! WARRANTY ACTIVATION IS REQUIRED online or via email/online. Please visit the official WARRANTY ACTIVATION section of our website OR email your completed Warranty Information Card, located in your instruction manual, to [email protected] home-shopping-express.com. Activation not only protects your investment with individual registration to the warranty program and provides exclusive access to amazing offers and new products! When you have a specific question or concern, including technical questions, you may contact our Customer Service Center directly and a member of our team will be pleased to assist with (Monday - Friday 09:00 / 17:00) CUSTOMERS IN UK (+44)(0)845 302 5761 CUSTOMERS IN SPAIN: (+34) 971 39 95 13 CUSTOMERS IN FRANCE: (+33) 0361080716 If you contact our Customer Service Center during non-business hours or if all of our representatives are helping other customers, please do not hesitate to leave a message on the answering machine and a member of our team will return your call - Guaranteed! HSE stands behind all of our products and suppliers with a firm commitment to quality and superior service. We promise to make every effort to ensure products are quality control tested and without malfunction or damage prior to leaving our distribution centers. In the event a return is necessary, you must first request a Return Materials Authorization (RMA) number. You will have to use your warranty card (DUAL SAW/STAR TWIN VIP MEMBER Card). In preparing your return shipment, please make sure to clearly indicate the RMA# (Return Materials Authorization number) on the outside of your package to ensure efficient return processing upon return to our Warehouse. If the RMA is not indicated, we may refuse the return. Without an RMA, we are not able to confirm receipt of 17 your return or process an exchange/refund. WARRANTY The Manufacturer’s warranty is limited to the terms set forth in the Warranty Information Card provided in the product instruction manual, or listed in the conditions listed in the section below: “2 YEARS SERVICE PROTECTION PLAN- LIMITED WARRANTY POLICY” The Warranty Information Card must be completed and returned per the instructions above (unless activated online) within 30 days from the order date. The EXTENDED 1-YEAR WARRANTY begins 2-Years or 730 days from the date of the order. Importantly, your warranty may be deemed null and void if the manufacturer’s VIP MEMBER Warranty Card was not activated online or via fax. The VIP MEMBER CARD provided with your machine or written in the product instruction manual must be activated online or via fax within 30 days from your original order date. A replacement instruction manual, as well as the Warranty Card, is available upon request via phone or email. Your full satisfaction is our goal - and in most cases we are flexible to varying situations, so please do not hesitate to contact us. Every Startwin tool is thoroughly inspected and tested before leaving the factory. If you are not satisfied with any Startwin tool within 7 days of purchase, return it and HSE will provide a replacement or refund. Startwin cutting tools are warranted to be free of defects from workmanship and materials for the period of TWO YEARS from the date of shipment from our warehouse. During this two-year period, if you have any problems please contact our Customer Service Center and request an exchange or return, then with your RMA and the instructions above, please return the tool inside an acceptable mailing carton/box, without the blades or accessories to the address provided by your retailer. Important: Blades, accessories, spare parts, laser, guide ruler, replacement blades, diamond replacement blades, cutting stand etc. are NOT covered under this warranty. Any accessory items, including accessories and blades will NOT be returned or exchanged. Important for Orders of: Package Precision set, all conditions precision Set, and Workstation Deluxe. Please return the tool freight prepaid, with the RMA# number clearly marked on the package (Returns without RMA number will NOT be accepted). Only orders with an RMA (Return Materials Authorization) from our Customer Service Center will be accepted: IN ANY CASE: Please contact your local Retailer/Distributor or/Importer for detailed return instructions. The easiest and fastest way to request a RMA (Return Material Authorization number) is via email to our Customer Service Center. EMAIL: [email protected] If you prefer the convenience of a personalized and immediate response in writing from one of our team members without waiting on a phone line, do not hesitate to sending your inquiry via email. Our Customer Service Email allows you direct contact with the manufacturer´s technical support service and our returns processing department. Feel free to ask any questions, and receive a response in less than 24 to 48 hours during nor18 EN mal business hours and if you can also request a Return Materials Authorization (RMA). CUSTOMER SERVICE Business Hours: Monday - Friday 09:00 / 17:00 Please have the following information ready: part number or model, detailed description of problem, and the original purchase order information. All the data collected from the customer service will be forwarded immediately to our Technical Service who will send you a response by email including the full return/exchange procedure to proceed the return (unless a phone response is specifically requested). We guarantee to answer all your questions, and resolve any concerns. Within 2-Years from the date of purchase, we will perform free of charge electrical, safety and performance checks, lubrication and replacement of parts worn under normal use. Performed at factory service centers only, transportation and freight are the responsibility of the customer. Our warranty policy is very simple; we want you to experience superior service. It means having detailed answers and immediate solutions to every question or concern. That’s why we’ve decided to not repair the damaged machines but instead to provide our customers a new replacement machine (blades and accessories not included). We can provide spare parts upon request. The first step is always that we have to receive your machine. Once we’ll receive your machine, we’ll proceed with an inspection and test to determine that the problem is covered under warranty. We appreciate if you provide any information, regarding the problem to our customer service team, or with your return package. If inspection shows that the problem was caused by a defective part, including workmanship or material, Startwin will send spare parts (or at our option, replace without charge.) This Warranty does not cover the following, where: • Repairs have been made or attempted by others • Repairs are required because of normal wear and tear • The tool has been abused, misused or improperly maintained • Alterations have been made to the tool • Parts are missing This limited warranty does not apply to accessory items such as circular saw blades, drill bits, router bits, jigsaw blades, grinding wheels, batteries and other related items. In no event shall HSE be liable for any indirect, incidental or consequential damages from the sale or use of the product. This disclaimer applies to both during and after the term of this warranty. Startwin disclaims liability for any implied warranties, including implied warranties of “merchantability” and “fitness” for a specific purpose, after the one-year extendable term of this warranty. This warranty gives you specific legal rights, and you may also have other rights, which vary from state to state. Some states do not allow the exclusion or limitation of incidental or consequential damages, so the above limitation or exclusion may not apply to you. If you have any questions or concerns, we are happy to help. Please do not hesitate to contact a member of our dedicated customer service team. 19 OPTIONAL BLADES AND ACCESSORIES STAD115TU STAD115SS TUNGSTEN 115 STAINLESS STEEL115 For universal purpose Especially for Stainless Steel STAD115DI STAD115GL DIAMOND 115 Stone, Tile, Marble, Ceramic... GLASS CUT 115 Especially for Glass STAGR115 STALA STALSP115 GUIDE RULER LASER GUIDE SPINLASER Accessory for straight cuts 20 Accessory for precise and straight cuts Accessory for perfectly straight cuts. 21 Imported and distributed by: HOME SHOPPING EXPRESS, S.A C/O GRANBY MARKETING SV., STANLEY STR. BB13BW BLACKBURN UNITED KINGDOM P. (+44) 08453025761 22
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In this tutorial, you will learn basic Vultr API v2 usage with the curl command and also with Python. By the end of this tutorial, you will know how to deploy a Vultr VPS from via the API and get it’s IP address.
Vultr API with Curl
In order to deploy a Vultr server, you need three pieces of information.
- Region
- Plan
- Operating system
Let’s determine the possible values for each of these, and choose one that meets our needs.
First, let’s determine the valid regions.
curl --location --request GET ''
The curl command will return a dictionary with all the possible regions. In this case, let’s choose syd for the datacenter in Sydney.
Next, let’s figure out what the options are for plans.
curl --location --request GET ''
The curl command will return a dictionary with all the possible Vultr plans. Let’s choose a basic vc2-1c-1gb instance.
Finally, let’s find out which operating systems are available.
curl --location --request GET ''
The curl command will return a dictionary with all the possible operating systems. I want Ubuntu 20.04 so the id associated with that is 387.
With this information, we can create spin up a Vultr server with the curl command.
curl --location --request POST '' \ --header 'Authorization: Bearer <your-api-key>' \ --header 'Content-Type: application/json' \ --data-raw '{ "region" : "syd", "plan" : "vc2-1c-1gb", "label" : "Hello from Curl", "os_id" : 387 }'
Feel free to choose your own values for region, plan, label, and os_id. Also, replace <your-api-key> with your actual Vultr API key.
The output from the curl command will contain information about your new server instance. Please take note of the instance id. We will use this next.
With your instance id, query the Vultr API again for information about your instance.
curl --location --request GET '<your-instance-id>' \ --header 'Authorization: Bearer <your-api-key>'
In the output, you will find the main_id field with the value of your instance’s IP address.
Vultr API with Python
We can use Python to interact with the Vultr API. To do this, we will primarily be using the requests Python library.
Based on the information from above, here is a full Python script that creates a Vultr VPS and gets it’s IP address.
import time import requests # private constants api_key = "<your-api-key>" # api url url = "" headers = {"Authorization": "Bearer {}".format(api_key), "Content-Type": "application/json"} data = { "region" : "ewr", "plan" : "vc2-1c-1gb", "label" : "Hello from Python", "os_id" : 387 } response = requests.post(url, json=data, headers=headers) instance_id = response.json()['instance']['id'] # wait a minute until the VPS is ready time.sleep(60) # get instance ip address instance_url = "{}/{}".format(url, instance_id) instance_response = requests.get(instance_url, headers=headers) ip_address = instance_response.json()['instance']['main_ip']
For more context, here is a video tutorial about interacting with the Vultr API that I created.
In case you still have questions, please don’t hesitate to leave a comment below or on the video. Find more Python tutorials here! | https://tonyteaches.tech/vultr-api-python-tutorial/ | CC-MAIN-2021-31 | refinedweb | 501 | 58.38 |
An Introduction to Java Servlets
written by Hans Bergsten
I assume that you're familiar with HTTP and CGI or a proprietary server API like NSAPI or ISAPI. I also assume that you are somewhat familiar with Java programming or some other object-oriented language, such as C++. Even if you're not a Java programmer you should be able to appreciate the benefits of servlets reading this article, but before you develop your own servlets I recommend that you first learn the Java basics.
The Dark Ages
Early in the World Wide Web's history, the Common Gateway Interface (CGI) was defined to allow Web servers to process user input and serve dynamic content. CGI programs can be developed in any script or programming language, but Perl is by far the most common language. CGI is supported by virtually all Web servers and many Perl modules are available as freeware or shareware to handle most tasks.
But CGI is not without drawbacks. Performance and scalability are big problems since a new process is created for each request, quickly draining a busy server of resources. Sharing resources such as database connections between scripts or multiple calls to the same script is far from trivial, leading to repeated execution of expensive operations.
Security is another big concern. Most Perl scripts use the command shell to execute OS commands with user-supplied data, for instance to send mail, search for information in a file, or just leverage OS commands in general. This use of a shell opens up many opportunities for a creative hacker to make the script remove all files on the server, mail the server's password file to a secret account, or do other bad things that the script writer didn't anticipate.
The Web server vendors defined APIs to solve some of these problems, notably Microsoft's ISAPI and Netscape's NSAPI. But an application written to these proprietary APIs is married to one particular server vendor. If you need to move the application to a server from another vendor, you have to start from scratch. Another problem with this approach is reliability. The APIs typically support C/C++ code executing in the Web server process. If the application crashes, e.g. due to a bad pointer or division by zero, it brings the Web server down with it.
Servlets to the rescue! can easily share resources as you will see in this article.
Security is improved in many ways. First of all, you rarely need to let a shell execute commands with user-supplied data since the Java APIs provide access to all commonly used functions. You can use JavaMail to read and send email, Java Database Connect (JDBC) to access databases, the File class and related classes to access the file system, RMI, CORBA and Enterprise Java Beans (EJB) to access legacy systems. The Java security model makes it possible to implement fine-grained access controls, for instance only allowing access to a well-defined part of the file system. Java's exception handling also makes a servlet more reliable than proprietary C/C++ APIs - a divide by zero is reported as an error instead of crashing the Web server.
The Servlet Run-time Environment
A servlet is a Java class and therefore needs to be executed in a Java VM by a service we call a servlet engine.
The servlet engine loads the servlet class the first time the servlet is requested, or optionally already when the servlet engine is started. The servlet then stays loaded to handle multiple requests until it is explicitly unloaded or the servlet engine is shut down.
Some Web servers, such as Sun's Java Web Server (JWS), W3C's Jigsaw and Gefion Software's LiteWebServer (LWS) are implemented in Java and have a built-in servlet engine. Other Web servers, such as Netscape's Enterprise Server, Microsoft's Internet Information Server (IIS) and the Apache Group's Apache, require a servlet engine add-on module. The add-on intercepts all requests for servlets, executes them and returns the response through the Web server to the client. Examples of servlet engine add-ons are Gefion Software's WAICoolRunner, IBM's WebSphere, Live Software's JRun and New Atlanta's ServletExec.
All Servlet API classes and a simple servlet-enabled Web server are combined into the Java Servlet Development Kit (JSDK), available for download at Sun's official Servlet site. To get started with servlets I recommend that you download the JSDK and play around with the sample servlets.
As this article is written (early March 1999), the released version of the JSDK is for the Servlet 2.0 API, with an Early Access version of the JSDK 2.1 available at Java Developer's Connection. All servlet engines mentioned above support the Servlet 2.0 API, and a few also support the 2.1 API. The examples of 2.1 API features in this article are clearly marked so you don't have to be surprised when they don't work with your 2.0 servlet engine.
Servlet Interface and Life Cycle
Let's implement our first servlet. A.
A typical example of an initialization argument is a database identifier. A servlet can read this argument from the ServletConfig at initialization and then use it later to open a connection to the database during processing of a request:
... private String databaseURL; public void init(ServletConfig config) throws ServletException { super.init(config); databaseURL = config.getInitParameter("database"); }
The Servlet API is structured to make servlets that use a different protocol than HTTP possible. The
javax.servlet package contains interfaces and classes intended to be protocol independent and the
javax.servlet.http package contains HTTP specific interfaces and classes. Since this is just an introduction to servlets I will ignore this distinction here and focus on HTTP servlets. Our first servlet, named ReqInfoServlet, will therefore extend a class named HttpServlet. HttpServlet is part of the JSDK and implements the Servlet interface plus a number of convenience methods. We define our class like this:
import javax.servlet.*; import javax.servlet.http.*; public class ReqInfoServlet extends HttpServlet { ... }
An important set of methods in HttpServlet are the ones that specialize the
service method in the Servlet interface. The implementation of
service in HttpServlet looks at the type of request it's asked to handle (GET, POST, HEAD, etc.) and calls a specific method for each type. This way the servlet developer is relieved from handling the details about obscure requests like HEAD, TRACE and OPTIONS and can focus on taking care of the more common request types, i.e. GET and POST. In this first example we will only implement the
doGet method.
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ... }
Request and Response Objects
The
doGet method has two interesting parameters: HttpServletRequest and HttpServletResponse. These two objects give you full access to all information about the request and let you control the output sent to the client as the response to the request.
With CGI you read environment variables and stdin to get information about the request, but the names of the environment variables may vary between implementations and some are not provided by all Web servers. The HttpServletRequest object provides the same information as the CGI environment variables, plus more, in a standardized way. It also provides methods for extracting HTTP parameters from the query string or the request body depending on the type of request (GET or POST). As a servlet developer you access parameters the same way for both types of requests. Other methods give you access to all request headers and help you parse date and cookie headers.
Instead of writing the response to stdout as you do with CGI, you get an OutputStream or a PrintWriter from the HttpServletResponse. The OuputStream is intended for binary data, such as a GIF or JPEG image, and the PrintWriter for text output. You can also set all response headers and the status code, without having to rely on special Web server CGI configurations such as Non Parsed Headers (NPH). This makes your servlet easier to install.
Let's implement the body of our
doGet method and see how we can use these methods. We will read most of the information we can get from the HttpServletRequest (saving some methods for the next example) and send the values as the response to the request.
protected void doGet(HttpServletRequest request, HttpServletResponse response)()); out.println("getScheme: " + request.getScheme()); out.println("getServerName: " + request.getServerName()); out.println("getServerPort: " + request.getServerPort()); out.println("getAuthType: " + request.getAuthType()); out.println("getMethod: " + request.getMethod()); out.println("getPathInfo: " + request.getPathInfo()); out.println("getPathTranslated: " + request.getPathTranslated()); out.println("getQueryString: " + request.getQueryString()); out.println("getRemoteUser: " + request.getRemoteUser()); out.println("getRequestURI: " + request.getRequestURI()); out.println("getServletPath: " + request.getServletPath()); out.println(); out.println("Parameters:"); Enumeration paramNames = request.getParameterNames(); while (paramNames.hasMoreElements()) { String name = (String) paramNames.nextElement(); String[] values = request.getParameterValues(name); out.println(" " + name + ":"); for (int i = 0; i < values.length; i++) { out.println(" " + values[i]); } } out.println(); out.println("Request headers:"); Enumeration headerNames = request.getHeaderNames(); while (headerNames.hasMoreElements()) { String name = (String) headerNames.nextElement(); String value = request.getHeader(name); out.println(" " + name + " : " + value); } out.println(); out.println("Cookies:"); Cookie[] cookies = request.getCookies(); for (int i = 0; i < cookies.length; i++) { String name = cookies[i].getName(); String value = cookies[i].getValue(); out.println(" " + name + " : " + value); } // Print the HTML footer out.println("</PRE></BODY></HTML>"); out.close(); }
The
doGet method above uses most of the methods in HttpServletRequest that provide information about the request. You can read all about them in the Servlet API documentation so here we'll just look at the most interesting ones.
getParameterNames and
getParameterValues help you access HTTP parameters no matter if the servlet was requested with the GET or the POST method.
getParameterValues returns a String array because an HTTP parameter may have multiple values. For instance, if you request the servlet with a URL like you'll see that the
foo parameter has two values:
bar and
baz. The same is true if you use the same name for more than one HTML FORM element and use the POST method in the ACTION tag.
If you're sure that an HTTP parameter only can have one value you can use the
getParameter method instead of
getParameterValues. It returns a single String and if there are multiple values it returns the first value received with the request.
You have access to all HTTP request headers with the
getHeaderNames and
getHeader methods.
getHeader returns the String value of the header. If you know that the header has a date value or an integer value you can get help converting the header to an appropriate format.
getDateHeader returns a date as the number of milliseconds since January 1, 1970, 00:00:00 GMT. This is the standard numeric representation of a timestamp in Java and you can use it to construct a Date object for further manipulation.
getIntHeader returns the header value as an
int.
getCookies parses the Cookie header and returns all cookies as an array of Cookie objects. To add a cookie to a response the HttpServletResponse class provides an
addCookie method that takes a Cookie object as its argument. This saves you from dealing with the format for different versions of cookie header strings.
If you compile the ReqInfoServlet and install it in your servlet engine you can now invoke it through a browser with a URL like. If everything goes as planned you will see something like this in your browser:
Request info
getCharacterEncoding: getContentLength: -1 getContentType: null getProtocol: HTTP/1.0 getRemoteAddr: 127.0.0.1 getRemoteHost: localhost getScheme: http getServerName: company.com getServerPort: 80 getAuthType: null getMethod: GET getPathInfo: /foo/bar getPathTranslated: D:\PROGRA~1\jsdk2.1\httproot\servlet\ReqInfoServlet\foo\bar getQueryString: fee=baz getRemoteUser: null getRequestURI: /servlet/ReqInfoServlet/foo/bar getServletPath: /servlet/ReqInfoServlet Parameters: fee: baz Request headers: Connection : Keep-Alive User-Agent : Mozilla/4.5 [en] (WinNT; I) Host : company.com Accept : image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, image/png, */* Accept-Encoding : gzip Accept-Language : en Accept-Charset : iso-8859-1,*,utf-8 Cookie : TOMCATID=TO04695278486734222MC1010AT Cookies: TOMCATID : TO04695278486734222MC1010AT
What if you want this servlet to handle both GET and POST requests? The default implementations of
doGet and
doPost return a message saying the method is not implemented. So far we have only provided a new implementation of
doGet. To handle a POST request the same way we can simply call
doGet from
doPost:
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); }
Persistent and Shared Data
One of the more interesting features of the Servlet API is the support for persistent data. Since a servlet stays loaded between requests, and all servlets are loaded in the same process, it's easy to remember information from one request to another and to let different servlets share data.
The Servlet API contains a number of mechanisms to support this directly. We'll look at some of them in detail below. Another powerful mechanism is to use a singleton object to handle shared resources. You can read more about this technique in Improved Performance with a Connection Pool.
Session Tracking
An HttpSession class was introduced in the 2.0 version of the Servlet API. Instances of this class can hold information for one user session between requests. You start a new session by requesting an HttpSession object from the HttpServletRequest in your
doGet or
doPost method:
HttpSession session = request.getSession(true);
This method takes a boolean argument.
true means a new session shall be started if none exist, while
false only returns an existing session. The HttpSession object is unique for one user session. The Servlet API supports two ways to associate multiple requests with a session: cookies and URL rewriting.
If cookies are used a cookie with a unique session ID is sent to the client when the session is established. The client then includes the cookie in all subsequent requests so the servlet engine can figure out which session the request is associated with. URL rewriting is intended for clients that don't support cookies or when the user has disabled cookies. With URL rewriting the session ID is encoded in the URLs your servlet sends to the client. When the user clicks on an encoded URL, the session ID is sent to the server where it can be extracted and the request associated with the correct session as above. To use URL rewriting you must make sure all URLs that you send to the client are encoded with the
encodeURL or
encodeRedirectURL methods in HttpServletResponse.
An HttpSession can store any type of object. A typical example is a database connection allowing multiple requests to be part of the same database transaction, or information about purchased products in a shopping cart application so the user can add items to the cart while browsing through the site. To save an object in an HttpSession you use the
putValue method:
... Connection con = driver.getConnection(databaseURL, user, password); session.putValue("myappl.connection", con); ...
In another servlet, or the same servlet processing another request, you can get the object with the
getValue method:
... HttpSession session = request.getSession(true); Connection con = (Connection) session.getValue("myappl.connection"); if (con != null) { // Continue the database transaction ...
You can explicitly terminate (invalidate) a session with the
invalidate method or let it be timed-out by the servlet engine. The session times out if no request associated with the session is received within a specified interval. Most servlet engines allow you to specify the length of the interval through a configuration option. In the 2.1 version of the Servlet API there's also a
setMaxInactiveInterval so you can adjust the interval to meet the needs of each individual application.
ServletContext Attributes
All servlets belong to one servlet context. In implementations of the 1.0 and 2.0 versions of the Servlet API all servlets on one host belongs to the same context, but with the 2.1 version of the API the context becomes more powerful and can be seen as the humble beginnings of an Application concept. Future versions of the API will make this even more pronounced.
Many servlet engines implementing the Servlet 2.1 API let you group a set of servlets into one context and support more than one context on the same host. The ServletContext in the 2.1 API is responsible for the state of its servlets and knows about resources and attributes available to the servlets in the context. Here we will only look at how ServletContext attributes can be used to share information among a group of servlets.
There are three ServletContext methods dealing with context attributes:
getAttribute,
setAttribute and
removeAttribute. In addition the servlet engine may provide ways to configure a servlet context with initial attribute values. This serves as a welcome addition to the servlet initialization arguments for configuration information used by a group of servlets, for instance the database identifier we talked about above, a style sheet URL for an application, the name of a mail server, etc.
A servlet gets a reference to its ServletContext object through the ServletConfig object. The HttpServlet actually provides a convenience method (through its superclass GenericServlet) named
getServletContext to make it really easy:
... ServletContext context = getServletContext(); String styleSheet = request.getParameter("stylesheet"); if (styleSheet != null) { // Specify a new style sheet for the application context.setAttribute("stylesheet", styleSheet); } ...
The code above could be part of an application configuration servlet, processing the request from an HTML FORM where a new style sheet can be specified for the application. All servlets in the application that generate HTML can then use the style sheet attribute like this:
... ServletContext context = getServletContext(); String styleSheet = context.getAttribute("stylesheet"); out.println("<HTML><HEAD>"); out.println("<LINK HREF=" + styleSheet + " TYPE=text/css REL=STYLESHEET>"); ...
Request Attributes and Resources
The 2.1 version of the API adds two more mechanisms for sharing data between servlets: request attributes and resources.
The
getAttribute,
getAttributeNames and
setAttribute methods where added to the HttpServletRequest class (or to be picky, to the ServletRequest superclass). They are primarily intended to be used in concert with the RequestDispatcher, an object that can be used to forward a request from one servlet to another and to include the output from one servlet in the output from the main servlet.
The
getResource and
getResourceAsStream in the ServletContext class gives you access to external resources, such as an application configuration file. You may be familiar with the methods with same names in the ClassLoader. The ServletContext methods, however, can provide access to resources that are not necessarily files. A resource can be stored in a database, available through an LDAP server, anything the servlet engine vendor decides to support. The servlet engine provides a context configuration option where you specify the root for the resource base, be it a directory path, an HTTP URL, a JDBC URL, etc.
Examples of how to use these methods may be the subject of a future article. Until then you can read about them in the Servlet 2.1 specification.
Multithreading
As you have seen above, concurrent requests for a servlet are handled by separate threads executing the corresponding request processing method (e.g.
doGet or
doPost). It's therefore important that these methods are thread safe.
The easiest way to guarantee that the code is thread safe is to avoid instance variables altogether and instead pass all information needed by a method as arguments. For instance:
private String someParam; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { someParam = request.getParameter("someParam"); processParam(); } private void processParam() { // Do something with someParam }
is not safe. If the
doGet method is executed by two threads it's likely that the value of the
someParam instance variable is replaced by the second thread while the first thread is still using it.
A thread safe alternative is:
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { someParam = request.getParameter("someParam"); processParam(someParam); } private void processParam(String someParam) { // Do something with someParam }
Here the
processParam gets all data it needs as arguments instead of relying on instance variables.
Another reason to avoid instance variables is that in a multi-server system, there may be one instance of the servlet for each server and requests for the same servlet may be distributed between the servers. Keeping track of information in instance variables in this scenario doesn't work at all. In this type of system you can instead use the HttpSession object, the ServletContext attributes, or an external data store such as a database or an RMI/CORBA service to maintain the application state. Even if you start out with a small, single-server system it's a good idea to write your servlets so that they can scale to a large, multi-server system the day you strike oil.
Resources
This article barely scratches the surface on the Servlet API and all the things you can do with servlets. You can learn more by visiting some of the Web sites below:
- Sun Microsystem's official Servlet API site
- Servlet enabled Web servers and add-on servlet engines
- The servlet chapter in Sun's Java tutorial
- Novocode's Servlet Essentials, a Servlet programming tutorial
- Servlet Central, articles about servlet technology, success stories, resources and more
- A database with many servlets, both freeware with source code and commercial products
- Information about the O'Reilly Java Servlet Programming book by Jason Hunter and William Crawford
This article originally appeared on WebDevelopersJournal.com.
Originally published on.
| http://www.developer.com/java/an-introduction-to-java-servlets-.html | CC-MAIN-2014-35 | refinedweb | 3,595 | 54.93 |
Are there any limitations to the amount of files that can be stored in Azure Storage?
I am concerned about storing all uploads in a single directory and wondering if they should be sharded somehow into a collection of directories.
I've searched the docs but can not find anything about this.
Windows Azure Storage (and I'm assuming you're referring to blobs) does not have a limit to the number of objects you can store. It's only limited by the 200TB-per-storage-account cap. And you can have multiple storage accounts in your subscription (each storage account maps to a namespace such as mystorage.blob.core.windows.net).
mystorage.blob.core.windows.net
Same goes for Table storage: no limit to the number of tables or the number of entities per table. Just the 200TB restriction.
Now, as far as directories go: Blob storage is organized by namespace.blob.core.windows.net/containername/blobname.ext. These aren't really directories. If you want true filesystem directories, you'll need to set up a disk in a blob (basically a vhd formatted as ntfs / ext3 / ext4 etc) and mounted to your OS disk. A disk is limited to 1TB (the max. size of a page blob). Once you do that, you have a complete file system to write to. Just a warning though: Only one VM can attach to a drive at a given time, so this isn't ideal if you're trying to have a file-share set up (direct blob storage is much better for that, or you'll need to set up an smb server for yourself).
namespace.blob.core.windows.net/containername/blobname.ext
One more thing about Azure storage: You don't have to worry about sharding; this is a massive-scale durable data storage system. Each blob is in its own logical partition, and the storage service organizes / reorganizes storage as necessary. This is something you don't need to worry about. The only thing I guide against is storing all objects in a single container, since enumerating blobs within a container could take a while if you have 10's of thousands of objects there. I typically don't enumerate containers, since I usually store blob uri's in another database as metadata (maybe in a SQL store, or MongoDB document store).
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Struts Built-In Actions
Struts Built-In Actions
In this section we will give a quick look to
the few of built-in utility actions shipped with Struts APIs. These
built-in utility actions provide different
Actions
Struts 2 Actions
Struts 2 Actions
In this section we will learn about Struts 2 Actions, which is a fundamental
concept in most of the web... request.
About Struts Action Interface
In Struts 2 all actions may implement
struts
struts how to make one jsp page with two actions..ie i need to provide two buttons in one jsp page with two different actions without redirecting to any other page
.
However with struts 2 actions you can get different return types other than...Struts2 Actions
When... generated by a Struts
Tag. The action tag (within the struts root node
Configuring Actions in Struts application
Configuring Actions in Struts Application
To Configure an action in struts... it is enabled the struts becomes much
friendlier and provide significant speed ...;struts-default"> </package>
defines the name of the package. Here
STRUTS ACTION - AGGREGATING ACTIONS IN STRUTS
STRUTS ACTION - AGGREGATING ACTIONS IN STRUTS... are a Struts developer then you might have experienced the pain of writing huge number of Action classes for your project. The latest version of struts provides classes
Implementing Actions in Struts 2
Implementing Actions in Struts 2
Package com.opensymphony.xwork2 contains.... Actions the contains the
execute() method. All the business logic is present....
login.jsp
<%@ taglib prefix="s" uri="/struts-tags" %>
|
Struts
Built-In Actions |
Struts
Dispatch Action |
Struts
Forward... |
AGGREGATING ACTIONS IN STRUTS |
Aggregating Actions In Struts Revisited...
configuration file |
Struts
2 Actions |
Struts 2 Redirect Action
Struts2 Actions
Struts2 Actions
Struts2 Actions... is usually generated by a Struts
Tag.
Struts 2 Redirect Action
In this section, you will get familiar with struts 2 Redirect action
Struts Tutorials
Struts Internationalization (i18n)
Struts Framework has built-in support... for version 9.0.2. Later versions of JDeveloper have built-in Struts integration...
Struts Tutorials
Struts Tutorials - Jakarta Struts
Test Actions
Test Actions
An example of Testing a struts Action is given below using...;
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts...;default" namespace="/" extends="struts-default">
<default 1 Tutorial and example programs
;
Struts Built-In Actions
- In this section... actions shipped with Struts APIs.
These built-in utility actions provide... of the Built-in Actions provided along with the struts framework
Struts 2.0 - JSP-Servlet
Struts 2.0 How to call two actions from single JSp page in Struts 2.0
struts
struts i have no any idea about struts.please tell me briefly about struts?**
Hi Friend,
You can learn struts from the given link:
Struts Tutorials
Thanks
established. Struts-based web sites are built from the ground up.... Struts-based web sites are built from the ground up to be easily modifiable...
Struts
Understanding Struts Hello,
Please I need your help on how I can understand Strut completely. I am working on a complex application which is built with Strut framework and I need to customize this application but I do
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How Red Hat killed its core product—and became a billion-dollar business(ars technica)
Posted Feb 29, 2012 22:37 UTC (Wed) by b7j0c (subscriber, #27559)
[Link]
Posted Mar 1, 2012 2:35 UTC (Thu) by lkewiu2 (guest, #83244)
[Link]
That's simply not correct. Look at the gap between RHEL 5 and RHEL 6. I fear that the gap between RHEL 6 and 7 will be even longer.
While Red Hat has proven the model of a very-long-term stable release, this can also kill the company in the long term.
Given that both RHEL 5 and RHEL 6 now have a 10 year supported lifespan, there is not much incentive to make RHEL 7 in any timely fashion (after all, the money is rolling in... "why break something that works ?")
Not doing major updates of a core product was the flawed business model of Commodore, which rehashed an antiquated design without much progress in both software and hardware (ie. the Amiga). A very similar problem occurred with the Saab car company -- it stuck with slightly updating its offerings, while competitors' products leapfrogged it (this was a large contributing factor in GM taking over the company, which eventually strangled it).
To the CEO of Red Hat, Jim Whitehurst: don't become another Commodore or Saab. The roadmap should not be entirely comprised of "a minor update to RHEL 6 every 6 months". It must also include "we are working new technologies X, Y and Z for RHEL 7, which will be released in a timely fashion".
(A simple but important example of "X" is proper C++11 support.)
Posted Mar 1, 2012 3:18 UTC (Thu) by thedevil (subscriber, #32913)
[Link]
Is that really a good example? Only if a significant part of RHEL boxes
were used for development, which doesn't feel right. Most developers
are probably using Debian - or Gentoo.
Posted Mar 1, 2012 3:56 UTC (Thu) by geofft (subscriber, #59789)
[Link]
C++11 is not evenly-distributed yet
Posted Mar 1, 2012 11:43 UTC (Thu) by jwakely (subscriber, #60262)
[Link]
Posted Mar 1, 2012 16:28 UTC (Thu) by Cyberax (✭ supporter ✭, #52523)
[Link]
Posted Mar 1, 2012 16:49 UTC (Thu) by mpr22 (subscriber, #60784)
[Link]
Posted Mar 1, 2012 17:10 UTC (Thu) by jwakely (subscriber, #60262)
[Link]
Posted Mar 6, 2012 11:42 UTC (Tue) by nix (subscriber, #2304)
[Link]
it changes the size of std::list
Posted Mar 6, 2012 13:15 UTC (Tue) by jwakely (subscriber, #60262)
[Link]
Posted Mar 7, 2012 14:19 UTC (Wed) by foom (subscriber, #14868)
[Link]
But as of right now, it's basically impossible to do without recompiling the world. And there's no easy way to know if you've screwed up either: it'll cause silent misbehavior or maybe mysterious crashes.
Basically, you can't link (even at runtime) any c++03 objects with c++11 objects and expect things to work right, if they use any standard library objects.
You're nearly certain to get symbol conflicts, because the templates in the standard library expand differently in the two modes, and all of the symbols from std:: are forced to be exported (even if you try to use -fvisibility=hidden). The differing classes from the two modes are given the same mangled name, so the linker will override one of the versions with the other, likely causing either the c++11 or c++03 code to misbehave.
After the namespace move, you should at least be able to load c++03 and c++11 objects into the same program, so long as the API used *between* them doesn't use classes from the standard lib. And if you do screw up, the failures will be an obvious link error, not a mysterious crash.
Posted Mar 7, 2012 15:02 UTC (Wed) by khim (subscriber, #9252)
[Link]
The plan seems to be to move std::* to another namespace (std::_v7::* or something like that)...eventually. I really wish that could've happened already, since I'd like to start compiling with c++11 more widely.
You can do that today: just compile two versions of GCC. Regular one for C++98 and gnu-versioned-namespace for C++11. The appropriate bug was fixed year ago.
In this case you'll not be able to use libraries compiled in C++98 mode from C++11 libraries (or vice versa), but at least you'll be able to link them together if they communicate using C interface...
Posted Mar 7, 2012 18:24 UTC (Wed) by jwakely (subscriber, #60262)
[Link]
Basically, you can't link (even at runtime) any c++03 objects with c++11 objects and expect things to work right, if they use any standard library objects.
so the linker will override one of the versions with the other, likely causing either the c++11 or c++03 code to misbehave.
If you have examples of crashes or silent changes in behaviour which match neither the C++03 nor C++11 semantics then please file a bug report and CC me.
Posted Mar 8, 2012 5:42 UTC (Thu) by foom (subscriber, #14868)
[Link]
Ehh. Not really. Sure, if you don't use any inlined or template functions/classes, you're safe for now. That's rather unlikely.
I'm not going to file a bug, because this has been explicitly stated to not be a bug. It would immediately get closed WONTFIX.
But here goes anyways, since you asked for an example...This is the most trivially obvious case of misbehavior. Constructing a similar failure using a class like std::set where the layout hasn't changed, but the implementations have is left as an exercise to the reader. (You could start with std::set::erase(iterator), which grew a return value in c++11.)
test1.cpp
========
#include <list>
#include <cstdio>
extern "C" int test2();
extern "C" int test1() {
std::list<int> x;
return x.size();
}
int main() {
// Should print 0 1.
std::printf("%d %d\n", test1(), test2());
}
test2.cpp:
========
#include <list>
extern "C" int test2() {
std::list<int> x;
x.push_back(5);
return x.size();
}
Now, compile:
g++-4.7 -std=c++11 -c -o test1.o test1.cpp
g++-4.7 -std=c++03 -c -o test2.o test2.cpp
g++-4.7 -o test test1.o test2.o
./test
Posted Mar 8, 2012 13:33 UTC (Thu) by jwakely (subscriber, #60262)
[Link]
> You could start with std::set::erase(iterator), which grew a return value in c++11
It also changed signature to std::set::erase(const_iterator) so mangles differently and the linker won't pick one over the other.
> It would immediately get closed WONTFIX.
You realise I'm one of the libstdc++ maintainers? I asked you to report specific cases of problems (except for std::list) and CC me to look at them. Even if they got closed WONTFIX at least there'll be a record of the problem and discussion, somewhere more suitable and useful than an LWN comment.
Posted Mar 8, 2012 14:25 UTC (Thu) by jwakely (subscriber, #60262)
[Link]
Ah, except that set::const_iterator and set::iterator are the same type in libstdc++ ... ok, I'll add that one to my list of potential problems!
Posted Mar 9, 2012 15:35 UTC (Fri) by foom (subscriber, #14868)
[Link]
I didn't make the connection, sorry.
> I asked you to report specific cases of problems (except for std::list) and CC me to look at them. Even if they got closed WONTFIX at least there'll be a record of the problem and discussion, somewhere more suitable and useful than an LWN comment.
Okay. Well, I admit I don't know of any more offhand. And since my app was already broken by the std::list change, it'd be way out of my way to go search for more. I'm not planning to take the risk of combining the two compilation modes again.
Move constructors being added everywhere is certainly another possible breakage point, and I'd be a little surprised if mixing c++03-variant functions in a class and c++11-variant functions in a class didn't manage to break something *somehow* related to move, but I don't know how to construct such an example.
It'll definitely cause ODR-violations aplenty, and at a minimum you'll get strange performance degradations in the C++11 code when linked with C++03 code (when a move constructor would've been called from a stdlib function in C++11 but not in C++03.). Perhaps that (somewhat harmless, but still mysterious) effect is all you'll get there, though...
Anyways, I'm quite surprised to hear that you care at all about this use case at all, since the message I got before was quite strongly: That isn't supposed to work, it *never* actually worked except, maybe, by accident, and you should have known better than to even try it.
BTW, is the list of potential problems you have public somewhere? It sure would be nice if this gotcha with std=c++11 was mentioned on GCC's C++11 status page.
Posted Mar 10, 2012 14:40 UTC (Sat) by jwakely (subscriber, #60262)
[Link]
There's no public list, but I'm keen to know where the problems are.
Posted Mar 1, 2012 3:23 UTC (Thu) by rahulsundaram (subscriber, #21946)
[Link]
There is always a bunch of features which cannot be backported easily and as time goes by, the demand for these increases. So despite a subscription model, there is enough incentive to do a new release every now and then. Red Hat has already announced that it is working on RHEL 7-...
Posted Mar 1, 2012 15:20 UTC (Thu) by dag- (subscriber, #30207)
[Link]
At some point Red Hat supported RHEL2.1, RHEL3, RHEL4 and RHEL5. With a 2 year release cycle and 7 years of support that would be the same today. But with a 10 year life-cycle, a 2 year release cycle would mean 5 to 6 distributions to support (not including ELS !) So releasing every 3 or 3.5 years (as happened with RHEL6) makes a lot more sense. Companies and consultants don't want too much diversity and shorter release cycles don't help in reducing diversity or even reducing support costs.
So I think it is safe to assume Red Hat will not release major releases more often than every 3 years. Unless you have inside information you are willing to share ? ;-)
Posted Mar 1, 2012 16:03 UTC (Thu) by rahulsundaram (subscriber, #21946)
[Link]
Posted Mar 1, 2012 5:08 UTC (Thu) by dowdle (subscriber, #659)
[Link]
Moving beyond that point... you also have to remember that while the last RHEL release cycle was longer (3.5 years), Red Hat also happens to be the most active innovator in most everything Linux. They do it via Fedora and via all of the sponsoring they do of a large number of projects. While those developments might take longer to make their way into RHEL, everyone else benefits within their own desired timeframes... so you really can't complain that Red Hat isn't innovating enough.
The main reason Red Hat has to release a newer RHEL sooner is because it becomes harder and harder to backport newer features and customers want them. If Red Hat can't provide them in a more timely fashion, then customers will look elsewhere.
While I too would like Red Hat to come out with new RHEL releases more often, I do credit them for not doing so just because some artificial timetable says they should. To mitigate things they are doing more and more rebasing... so far mostly of desktop apps. Two other examples are KVM and php53 being added to later RHEL5 updates. Expect more of that behavior in the future. I think they could definitely improve if they offered multiple / updated python and ruby stacks in future update releases. I think that would help much of the pain.
Posted Mar 1, 2012 5:52 UTC (Thu) by lkewiu2 (guest, #83244)
[Link]. (By this I do not mean a Fedora/Ubuntu-like approach of half-baked goods every 6 months. Perhaps stuff that was "proven" in Fedora for at least one release is allowed to progress to a "RHEL-non-core" repository).
The separation of course is subjective and depends on what is meant by "core". One must also question as to where and why the need has arisen to freeze almost every bit of software at a particular version. Is it the constantly shifting nature of open-source software, where each project has unique definition of what is meant by a stable version? (eg. the Boost libraries can have API changes between versions, even though all releases are "version 1.x").
Perhaps the freezing should be more selective, and apply only to software that is known not to play nice?
Posted Mar 1, 2012 6:25 UTC (Thu) by rahulsundaram (subscriber, #21946)
[Link]
Posted Mar 1, 2012 10:30 UTC (Thu) by joib (guest, #8541)
[Link]
I'd also like to see more flexibility wrt which version of a particular software in used in a distro (be it through a separation of "core" and parallel installable "apps", or whatever), but to some extent that would also increase the QA burden. But other platforms manage to do it (e.g. Windows, OSX, IOS, Android), so why not Linux distros?
Posted Mar 1, 2012 12:36 UTC (Thu) by pboddie (guest, #50784)
[Link]
Your Amiga example is actually very much off. The Amiga was in no way based on the 8-bit Commodore machines and was a complete departure... actually developed by the Atari 8-bit design team..
Your Amiga example is actually very much off. The Amiga was in no way based on the 8-bit Commodore machines and was a complete departure... actually developed by the Atari 8-bit design team.
Indeed, the Amiga architecture didn't get the improvements it needed to stay competitive. It's interesting to read the details of both introduced and planned chipsets now, almost a couple of decades after heated discussions about whether Commodore would pull through and deliver various rumoured and hyped technologies, but the inability to deliver substantial improvements (or alleviate some of the features that had become almost anti-features) in a timely fashion haunted many of the company's competitors, too.
Not that this relates directly to Red Hat, however: Red Hat's engineers are obviously involved at the tip of kernel development, and there's a steady stream of product improvements propagating through the company's product line. They certainly aren't pushing a tweaked decade-old product and pretending that it's still competitive.
I think they [RHEL] could definitely improve if they offered multiple / updated python and ruby stacks in future update releases. I think that would help much of the pain..
I think they [RHEL] could definitely improve if they offered multiple / updated python and ruby stacks in future update releases. I think that would help much of the pain.
There is demand for user-installable packages, at least amongst users. Sadly, there is also a gap between the packaging community, who frequently have sufficient privileges to install whichever packages they like and who therefore don't see any problem, and the user community who have to live with whatever gets served up.
Posted Mar 2, 2012 15:53 UTC (Fri) by michaeljt (subscriber, #39183)
[Link]
I wonder how many people think that more separation between core OS and applications would be a good thing for classical Linux-based distributions (noting along the way that other OSes seem to be going the other way with their app stores). I could imagine statically linked OS X/NextStep-like bundles where the binaries inside probe their environment a bit dynamically when they are started. I have always liked the way that bundles let the filesystem serve as both application menu and package manager (which seems to me more Unix-like than the current norm). I don't think that statically linking would be a big size problem today given modern disk and RAM sizes, though I fear that a lot of our infrastructure has subtle dependencies on dynamic linking (notable case: glibc).
And I can imagine some of the effort which goes into distribution maintenance today being put into centralised build systems which provide downloads, updates and monitoring (with automatic re-building) of static dependencies for security issues - except that upstream would choose a single build system to go along with instead of every distribution doing their own packaging with a slightly different build and running environment (especially due to subtle dynamic linking issues).
That said, OS X-style bundles work very well for typical OS X-style applications. I think that they could be made to work well for a lot more usage cases, but that is far less well explored ground.
Posted Mar 5, 2012 9:27 UTC (Mon) by dgm (subscriber, #49227)
[Link]
Posted Mar 5, 2012 11:57 UTC (Mon) by michaeljt (subscriber, #39183)
[Link]
It would be interesting to see how close one could get today though - for something which goes in that direction see the generic VirtualBox installer, which I think we can still improve on quite a bit. That sort of thing can be very handy for distributing test versions of software today, as it can be installed and run without disturbing too much in the rest of the system and due to the static linking you have a lot fewer unknowns than when a user tests a distribution version of your software. If I ever find time I would like to develop what we have now into a framework that other people can use and advertise it a bit.
Posted Mar 5, 2012 12:38 UTC (Mon) by khim (subscriber, #9252)
[Link]
Will not work. Usually you need some kind of logic to handle differences between distributions and thus the end result is something like Autopackage or InstallAnywhere: large pile of code you are supposed to run with root privileges.
Technically it should be possible to create something usable, but since distributions are expressly not interested the only feasible solution is to concentrate on MacOS/Windows (platforms which actually care about ISVs). If you want to support Linux then just pick one versions (the one you'll use internally) and forget about all others: if your program will be interesting enough and popular enough then it'll be ported to other distributions "by community" and if not, then it does not really matter.
Posted Mar 5, 2012 14:16 UTC (Mon) by michaeljt (subscriber, #39183)
[Link]
Yes, you will end up with a certain amount of code which need to be run as root to achieve full system integration. Such is life. That said, finding ways of reducing that, making it optional and/or making it as transparent as possible is an interesting aim (and binary distribution does not necessarily mean closed source!) Generally the sort of application where it is hard to get rid of are those which need to run with privileges of some sort anyway. Ditto for handing differences between distributions. Why though does this mean it won't work?
> Technically it should be possible to create something usable, but since distributions are expressly not interested the only feasible solution is to concentrate on MacOS/Windows (platforms which actually care about ISVs).
Distributions are currently interested in doing things the way they do them now, which is why I think this is more interesting for upstream developers wanting to ship test and bleeding edge versions..
As a side note, creating integration code which is as easy as possible for distribution packagers to use in their own packages is also an aim of mine (not least because we ship a generic and distribution-specific packages ourselves). There is likely to be room for both approaches for a long time to come, so reducing wasted effort is sensible.
Posted Mar 5, 2012 16:26 UTC (Mon) by khim (subscriber, #9252)
[Link]
Yes, you will end up with a certain amount of code which need to be run as root to achieve full system integration.
Not "to achieve full system integration". Just "to run it". Something like this. Simple things (register daemon, add d-bus service, etc) is system-dependent and often not backward compatible.
And binary distribution does not necessarily mean closed source!
Sure. Most such system use bash scripts! Thousands lines of bash scripts…
Why though does this mean it won't work?.
Sure, but if distributions are not in the loop then their changes will break these packages regularly.
Posted Mar 5, 2012 16:45 UTC (Mon) by michaeljt (subscriber, #39183)
[Link]
Yes, SELinux is a pain, particularly if you are doing unusual things. The rest isn't half as bad as you make it sound (we do register daemons; we don't register DBus services but I have looked at it). Our code is messier than it should be as I have learnt as I went along (it is being fixed gradually but as it works that is low priority). The biggest problem in my opinion is lack of experience among application developers at handling these things.
>.
Actually distribution-independent packages are no more badly affected than the dependent ones if you know what you are doing (or the dependent ones are affected just as badly if you like). Perhaps I was just lucky, but my experience here too is that it isn't as bad as you are making out, and that the main problem is building up the experience regarding how to do it right.
Posted Mar 5, 2012 20:48 UTC (Mon) by khim (subscriber, #9252)
[Link]
Actually distribution-independent packages are no more badly affected than the dependent ones if you know what you are doing (or the dependent ones are affected just as badly if you like).
Differences are not technical. When upgrade breaks in-distro application then it's usually fixed. But when upgrade breaks out-of-distro application, or, even worse, if out-of-distro application break the precious distro then it's ostracized and solution proposed is "don't install software not from official repo".
As long as that's the case all these projects are hopeless. It looks like distributions are finally starting to understand that it's bad position to be in. We'll see. Perhaps something will actually happen on this front. But since it's not technical problem, but mostly attitude problem it's impossible to solve it using sorely technical means. Especially without collaboration with distributions.
Posted Mar 1, 2012 18:07 UTC (Thu) by tjc (subscriber, #137)
[Link]
Jay Miner came from Atari to Amiga (which was then purchased by Commodore), but I don't recall that anyone else did.
Posted Mar 1, 2012 7:53 UTC (Thu) by AndreE (subscriber, #60148)
[Link]
Posted Mar 1, 2012 16:19 UTC (Thu) by dag- (subscriber, #30207)
[Link]
(Look at the advances the _old_ RHEL5 kernel is still making)
BTW the vast progress and usefulness of the ELRepo project would not have been as easy as it is today in the RHEL3 and RHEL4 era.
Posted Mar 1, 2012 16:21 UTC (Thu) by jengelh (subscriber, #33263)
[Link]
Now wonder why we still need updates if everything can be reimpl^Wbackported.
Posted Mar 1, 2012 10:26 UTC (Thu) by NAR (subscriber, #1313)
[Link]
Posted Mar 1, 2012 11:46 UTC (Thu) by kragil (guest, #34373)
[Link]
Posted Mar 1, 2012 15:36 UTC (Thu) by idra (subscriber, #36289)
[Link]
I think you do not understand the subscription model if you think in this terms. The money rolls in only if customers are satisfied, Red Hat is not using an old business model of selling proprietary crap for high upfront cost and then forcing you to buy maintenance to go forward. Pretty much the opposite. So in order to be appealing Red Hat has to release the requested features in a timely fashion.
That's a powerful driver for new releases because you cannot backport disruptive changes (that keep brewing in Fedora) to older releases.
Posted Mar 1, 2012 15:52 UTC (Thu) by hp (subscriber, #5220)
[Link]
The initial story may have been this one:-... and then there were follow-on stories around the web.
So the story initially came out as "Red Hat abandons retail" - which many somehow translated into "Red Hat abandons desktop" - with no mention of Fedora. Initially some took it to mean that only RHEL would exist. A bit later there was a poorly-explained false-start launch of Fedora under the name Red Hat Linux Project due to internal miscommunications at Red Hat.
And there were some sideshows like...
What Red Hat was trying to do was split Fedora and RHEL, making each more purely what Linux geeks and enterprises respectively really wanted instead of fighting that tension all the time. And yes, this included charging enterprises a lot more money because they wanted a lot more work done and a lot more support. The move wasn't supposed to relate to "the desktop" as both Fedora and RHEL contained all the desktop stuff and it turned out that Red Hat quadrupled their desktop development team soon after.
But the story got on Slashdot before Red Hat really had its ducks in a row, and by the time Red Hat had a crisp clean plan that was well-explained, everyone remembered something not-quite-right like "Fedora will be unusable" or "Red Hat only has RHEL" or "Red Hat abandoned the desktop."
Fortunately it all worked out in the end, in that Fedora and RHEL today are both doing very well and have lots of users who like them, and Red Hat's business is thriving.
Posted Mar 1, 2012 16:41 UTC (Thu) by dag- (subscriber, #30207)
[Link]
A lot of people where running Red Hat Linux 8.0 and Red Hat Linux 9 (more people stuck with Red Hat Linux 7.3 because of RPM and NPTL related issues).
And I also clearly remember disgruntled Red Hat employees making statements of how the company was taken over by shareholders and suits. While today it may be seen as necessary and contributing to where Red Hat is today, back then it looked more like a gamble, or rather, breaking with its Open Source roots. It appeared as if people were leaving Red Hat in flocks (but it might as well have been a vocal Debian community instead ;-))
Maybe unintentionally the article (title) hit the same nerve with an ironic twist.
Posted Mar 1, 2012 17:01 UTC (Thu) by hp (subscriber, #5220)
[Link]
There was a lot of controversy, and some people did leave around this time. Most had other reasons they were ready to leave though, in my opinion, even if leaving retail was part of it. Also (obviously) in my opinion, what Red Hat did turned out to be a good decision in hindsight, though messily executed and communicated.
I think it's a lot more interesting to look at how something of a mess turned out well. The cleaned-up version sounds like Red Hat was so super smart but really it was this giant painful collaborative process that eventually stumbled on a good answer...
Posted Mar 1, 2012 17:36 UTC (Thu) by rahulsundaram (subscriber, #21946)
[Link]
Posted Mar 1, 2012 19:35 UTC (Thu) by jspaleta (subscriber, #50639)
[Link]
To me the handling of the recovery associated with the false start of rhpl and the reboot as fedora with the fedora.us merge is exactly why I continue to trust Red Hat. Messy and painful...but exceedingly honest as to pain points, difficulties and expectations. This was not a promise the moon or a "trust us" endeavor. The candor as to not having a fully realized gameplan on how to leverage community involvement said to me that there was a real opportunity for externals to have a say and to influence the structure of the fedora project long term.
Yes even with the teeth pulling slowness to provide external access to a build system for Fedora Core..even with those stumbles..watching an established corporate entity re-orient so significantly with regard to open and transparent community centric approach to development is very instructive. If Red Hat can do it, other existing corporate entities can do it. There are a lot of hard fought lessons learned in that history I think that should be distilled for reference. Obviously the relationship across the corporate fenceline it not perfect, whatever that means. But it appears to be working, sustainable and significantly more beneficial for the entire linux software ecosystem, in a way that the rhl era of operation was not.
-jef
Linux is a registered trademark of Linus Torvalds | http://lwn.net/Articles/484522/ | CC-MAIN-2013-48 | refinedweb | 4,886 | 58.32 |
less typing, adding the prefix int safely.
Sometimes, we know in advance that we are not going to need negative numbers. This is common when using a variable to store the quantity or size of something (such as your height -- it doesn’t make sense to have a negative height!). An unsigned integer is one that can only hold positive values. To
Alex,
I came back here from the bitwise lesson. I think I missed something about storing integers that you may have written somewhere. But I don’t recall seeing.
How does C++ or the compiler handle all the leading zero’s when your system and mine need 4 bytes 32bits to store small integers like 1 (one}? Certainly other data types or situations require throwing out leading or trailing zero’s.
Char also come to mind here too. What happens of someone uses a long-long integer and then stores a small number there?
Can you give us some insight, Thanks
The compiler or CPU’s instruction set should handle the padding as appropriate. For example, if you assign the integer value 1 to a 32-bit memory location, it will assign the value 00000000 00000000 00000000 00000001. It’s not something you need to worry about as a programmer.
Why do we need to write "return 0;" in the last line of this program?
#include <iostream>
int main()
{
using namespace std;
unsigned short x = 0; // smallest 2-byte unsigned value possible
cout << "x was: " << x << endl;
x = x - 1; // overflow!
cout << "x is now: " << x << endl;
return 0;
}
Typos.
"See lesson 23 (2.3) -- variable sizes and the sizeof operator"
"In lesson 21 (2.1) -- Basic addressing and variable declaration"
"If there is any doubt (suspicion) that a variable might need to store a value that falls outside its range, use a larger variable!" Either say ‘suspicion that it won’t work’ or ‘doubt that it will work’, not ‘doubt that it won’t work’ (double negative). You probably just started saying one these and switched when writing.
Fixed! Many thanks.
sizeof(long) on machine is 8 and not 4 as mentioned above. (64bit Ubuntu).
4 bytes is the minimum size that C++ guarantees a long will be. However, it can be more on some architectures, such as the one you are using.
The first line calls even the negative numbers whole numbers, which is mathematically incorrect.
You are correct. I’ve updated the terminology.
Minor thing I noticed while reading through:
The decimal / binary value table would make a bit more sense if the binary values were right-aligned on the table instead of left aligned. This would imply visually that each new digit added appears on the left, rather than the right as new bits are added.
It'd technically also be useful to highlight the new digit with a bold font each time it goes up a bit for much the same reason.
It's not a big deal, but it'd likely make it easier for people to visualize what's going on with the overflow example immediately after. =3
Good idea to use right-alignment. It does make the table more comprehensible. Thanks for the suggestion.
Hi again,
around the example of overflow of 65535 + / - 1, the quotation marks are misplaced in the codes.
It should be:
instead of:
Also, some redirections have names like "24-integers" instead of "2.4-integers," although it doesn't really matter.
One final question:
I understand how 65535 + 1 becomes zero, but I can't understand how 0 - 1 becomes 65535 for unsigned shorts.
Matthew
Thanks, I fixed the quotes.
Regarding the last question, I just answered that one: here.
Why specify that an integer is signed? I understand why we’d specify it’s unsigned, but just declaring an int without adding “signed” still lets you input negative numbers. So why?
The primary use of the signed keyword is to explicitly specify whether char is signed or unsigned (since it could be either by default). Although you can use it with the other integer types, it is completely redundant.
hey im new to programming . i have one doubt.
Isnt ‘char’ used to denote characters ?
how come youre telling its an integer data type??
It is an integral data type, in the fact that it can only represent an integer, the same limitation that the other integral types (short, int, long) have.
The special handling of char traces back to the early days, when there were only 8 bits available to assign for text characters on a display screen.
You can do arithmetic with char types, you just have to be careful when you want to look at the results.
char a=65, b=66;
cout << a << b << endl;
cout << a+b << endl;
Notice how cout implicitly cast the a+b evaluation to int type so you see the actual sum of 65+66 displayed, but when simple char variables are inserted into cout then the ASCII characters are output back to you.
If you are using char to write or read text, as most uses of it are, everything is cool as can be, in fact strings are simply of type char*
Ummm….please ignore the program I put up above (it’s displayed incorrectly). Although I did use the code from the comprehensive quiz from 1.11 (using an unsigned int) to try adding up two negatives, -1 and -1 and still got a proper answer: -2. When I tried an unsigned short, I got issues (I got the number 131070, which is way more than what an unsigned short is supposed to give based on the table above (seeing as a short is an unsigned 2 bytes integer variable)).
What I also wanted to know was (and I think I might know the answer after thinking back on games), is the 0-255 supposed to be LITERALLY the number 255, or as in 255 digits?
Sorry for triple posting, but I think I found the problem. Please correct me on these assumptions (for which I’m using the comprehensive quiz question from 1.11):
1. The integer variable within the “int readnumber()” function limits the maximum/minimum number it can reach (hence with an unsigned short, it’s 65,535) while the “void writeanswer(int x)” allows for a maximum/minimum of what int is capable of (which is a larger number). Hence, if the integer variable within the readnumber function was capable of int size while writenumber is only (writenumber(short x)), then the maximum/minimum achievable is only what short is (which is 65,535).
2. Doing an unsigned short within the “int readnumber()” function, if we input -1 for the first number and -1 for the second, we get 131070 because they each take a step back from 0 and arrive at 65,535 each (hence a total of 131,070). This is still strange for me because unsigned int still gives the proper -2 after inputting -1 (for the first) and -1 (for the second). Unsigned short is NOT capable of adding up -1 and -1, but unsigned int is.
3. I think I had one more assumption, but it escapes me right now.
oh…my…god….I can actually feel my brain cells evaporating. I have NO idea what this article is talking about and can’t understand it no matter how many times I try to read it.
Using code::blocks and the program from the comprehensive quiz from chapter 1:
-------------------
main.cpp:
#include
#include “io.h”
using namespace std;
int main()
{
cout << "short: " << sizeof(short) << endl;
int b = ReadNumber();
int z = ReadNumber();
WriteAnswer(b+z);
return 0;
}
io.cpp:
#include
int ReadNumber()
{
cout <> x;
return x;
}
void WriteAnswer(int a)
{
cout << "Total: " << a << endl;
}
io.h:
#ifndef IO_H
#define IO_H
int ReadNumber();
void WriteAnswer(int a);
#endif // IO_H
When I run the program I can still calculate -10 + -10 to a total of -20, am I (grossly) misunderstanding this lesson? I'm trying to understand the whole bytes thing and such but I'm not getting it at all. When I use unsigned int, I can calculate -1 + -1, but for some reason with unsigned short, -1 + -1 gives me what I'm assuming is an overflow issue (I get 131070 as a total). Please help 🙁
* missed the last 1 off the 2nd to last line
i can understand how integer overflow happens when you increase an unsigned integer -
i.e. 65535 = 1111 1111 1111 1111
and 65536 = [1] 0000 0000 0000 0000
so only given 2 bytes of data this reverts back to meaning 0.
However, I can’t understand how this happens in reverse?
i.e. 0 = 0000 0000 0000 0000
So when you subtract one to get -1, how does this revert back to 1111 1111 1111 111
in terms of how memory is stored?
You are working with an unsigned int, there is no negative value.
So you cannot ever reach a value of -1, 0 is as low as you can go before overflow.
Counting down: 5 4 3 2 1 0 65535 65534 65533 …
You guys ask hard questions.
The C99 spec says: “the value is converted by repeatedly adding or subtracting one more than the maximum value that can be represented in the newtype until the value is in the range of the newtype”.
So in this case, -1 is converted to an unsigned int by adding (UINT_MAX + 1) to the value. The resultant value (UINT_MAX) is between 0 and UINT_MAX. UINT_MAX is the maximum int (e.g. 65535). So -1 maps to 65535.
The C++ spec essentially says the same thing, only in a much more complicated way.
An an aside, it turns out the using two’s complement as the underlying representation makes this trivial.
Consider: -1 in two’s complement:
binary representation for 1: 0000 0001
flip the bits: 1111 1110
add 1: 1111 1111 in two’s complement
1111 1111 as an unsigned = 65535
Consider: -2 in two’s complement:
binary representation for 2: 0000 0010
flip the bits: 1111 1101
add 1: 1111 1110 in two’s complement
1111 1110 as an unsigned = 65534
Consider: -65535 in two’s complement (yes, this is outside the range for a 16-bit signed number, and should take 17 bits to represent properly in two’s complement, but we only have 16 bits, so lets use them and see what happens)
binary representation for 65535: 1111 1111
flip the bits: 0000 0000
add 1: 0000 0001 in two’s complement
0000 0001 as an unsigned = 1 (it still works!)
So if the compiler is using two’s complement binary representation for signed numbers (which many do), then all that’s needed is to interpret the number as an unsigned number.
when you say, an int variable has a size of 2 bytes or 4 bytes, what do u mean? does it dynamically change size from 2 to 4 bytes as the number get larger?
No, it’s up to your compiler, which generally picks an appropriate value based on your computer’s architecture.
This means int will always have the same fixed size on a given system.
What is the difference between the “long” and “int” variable types? (They both have the same size).
They are same size on your platform. That does not guarantee they are the same size on another platform.
In your particular case there is no difference. But never assume it’s also the same for anyone else.
A long is guaranteed to be the same size or larger than an int on the same machine. That’s as far as the contract goes.
I’ve updated the tutorials to indicate that different variables have a guaranteed minimum size. For int, it’s 2 bytes. For long, it’s 4 bytes.
For “1 byte signed” the range is -128 to 127, how is -128 represented in 1 byte, does’nt it cause an overflow?
127 => 01111111
-128 => 111111111 (the right most 1 represents - negative)
Also why cant we represent 128 in 1 byte (why is the range only till 127?)
128 => 10000000
Thx
A signed char -128 in binary format is 10000000
Now you may question why is this so if the left most bit is the sign bit and the other seven bits are the value?
Well you don’t want to ever use -0, that’s kind of useless.
So the last 7 bits are actually a twos-complement of the absolute value of the negative value.
See for an explanation of twos-complement.
I discuss two’s complement in section 3.7 -- converting between binary and decimal
Can someone tell me why this does not work.
As per the above lesson char is type of INT. so this should work.
This is because when you insert a char into std::cout (which is actually basic_ostream<char>) it doesn’t display on the console as the literal value in base 10, it displays as a single ASCII character.
basic_ostream<char>
If it worked as you assumed then cout << "Hello"; would print 72101108108111 (if iomanipulator flag set to std::dec)
cout << "Hello";
72101108108111
Cast char to int before insertion:
unsigned char ch1=5;
std::cout << "The value of ch1 is : "<< (int)ch1 << endl;
Then you will see the value of the char displayed as you wished it to be.
Correct, std::cout prints characters as ASCII values instead of integer values because that is what they are more often used for.
(int)ch1 is an old-school C-style cast. In C++ you should do int(ch1).
We discuss casting in lesson 4.4 -- Type conversation and casting.
oops…
12 - 1100
13 - 1101
14 - 1110
15 - 1111
Adam,
In the overflow section, I noticed you only have 14 numbers. Shouldn’t there be 16 since you are starting from 0. Wouldn’t it be:
0, 1, 10, 11, 100, 101, 110, 111, 1000, 1001, 1010, 1011, 1101, 1111
0 - 0
1 - 1
2 - 10
3 - 11
4 - 100
5 - 101
6 - 110
7 - 111
8 -1000
9 -1001
10-1010
11-1011
12-1101
13-1110
14-1111
15-10000
?
I thing it is 0-1-10-11-100-101-110-111-1000-1001-1010-1011-1100-1101-1110 to make a 15 and to make a 16, just add a 1111……
Let me know if I am mistaken…..great tutorials…
Concrete basics of binary counting:
If you understand that in decimal system 248 stands for
2 x 10^2 +
4 x 10^1 +
8 x 10^0
and 13 for
1 x 10^1 +
3 x 10^0
then it is quite easy to convert in your head small decimals to binary and vice versa. For example 1011 is
1 x 2^3 = 8 +
0 x 2^2 = 0 +
1 x 2^1 = 2 +
1 x 2^1 = 1
= 11.
When you go one integer (1) up in whatever the base (binary, octal, decimal etc.) you increase the lowest nominator to the highest possible until it reaches maximum, then you increase the second to the lowest if possible, if not, the third to the lowest etc. For example in octal system next from 4677 is 4700, because you can’t get higher than 7 (and after that of course 4701). In binary next from 1011 is 1100 (because from right to left first two 1’s can’t get higher). After 1100 -> 1101, 1110, 1111. And you can assure it by counting:
1100 = 8 + 4 + 0 + 0 = 12
1101 = 8 + 4 + 0 + 1 = 13
1110 = 8 + 4 + 2 + 0 = 14
1111 = 8 + 4 + 2 + 1 = 15.
Yes, fixed. 🙂 Thanks for pointing that out.
The simplest method of converting decimal to binary is to write the 2 raised to powers below each binary digit and striking out the powers below 0
for e.g-
the number is 1101001
1 1 0 1 0 0 1
2^6 2^5 2^4 2^3 2^2 2^1 2^0
Now cancel all numbers below 0 i.e cancel the powers 1,2,4
add the others = 1+8+32+64
= 105
65535 is 0011011000110101001101010011001100110101
65536 is 0011011000110101001101010011001100110110
how is short able to maintain the first but not the second?
can u please explain?
I don’t think you have your binary right,
That’s called BCD (Binary Coded Decimal)
How do you prevent an integer overflow?
My program prevents users entering a number higher than a billion, that works just fine. But, however, if a user enters a number that exceeds the integer-range, my program gets stuck in a loop. Is there a way to prevent a user from entering a number that causes an overflow?
There are (at least) a few possible ways to do this:
1) Read the user’s input as a string, validate that the user entered something that fits in your variable, and then convert the string to your numeric value.
2) Read in the user’s input character by character and validate that input as they enter it (stop them from entering any character that would overflow your variable).
Neither of these is easy.
Thanks again for your excellent tutorials Alex.
Just 2 quests;
1. in the ‘Range’ table above, 4 byte unsigned 0 to 4,294,967,296: is it 4,294,967,296 or 4,294,967,295?
2. when Stroustrup says “The unsigned integer types are ideal for uses that treat storage as a bit array.”, does he mean when you are using the bits within a variable to check if they are on or off?
1) 4,294,967,295. I fixed the error.
2) A bit array is typically used when you have a bunch of independent bit-size variables (booleans) and want to store them in a compact format. So yes, using the individual bits within a variable. An unsigned variable would be better for this purpose than a signed one is because the underlying (binary) representation is well defined. The underlying (binary) representation for signed variables can vary from system to system.
What do you do if 4/8/16 bits isn’t big enough? For instance, number theorists like to do arithmetic on very big numbers, ~ 100 to 200 digits large.
On modern architectures, generally longs are 32 bits. Most modern compilers also give you access to a 64-bit integer type (often called a long long, but sometimes it has other names, like __int64).
However, if you need even larger integers, then you will have to write your own data type. You will learn how to do this in the section on classes (chapter 8).
Great tutorial! Knew nothing this morning, now already something.
Detail: the math behind the table with unsigned/signed range:
doesn’t the n-bit unsigned variable have a range of 0 to 2^n instead of 0 to 2^n-1?
As it was mentioned above:
As you learned in the last section, a variable with n bits can store 2^n different values…
As 0 (zero) is also a value, the maximum number is (2^n)-1 and range becomes 0 … (2^n)-1 (inclusive).
When overflow, does it dangerous? It can change other memory bits right (That may be used by other variables/application)?
OK, I understand after reading forward.
Dangerouse because it could change the other variables.
Thank you
Actually, overflow will just result in the most significant bits being lost. It won’t overflow into other variables.
Actually, overflow will just result in the most significant bits being lost. It won’t overflow into other variables.
It’s just because mathematical operations do not work with memory directly. The operand is put into CPU register (mostly EAX (on x86 machines) or its part - as the only register for integer mathematical purposes) for processing. The result (which can also occupy EDX register) is then taken from the initial place (EAX register) leading to higher bits lose.
However, if you’re dealing with putting the contents of the EAX register back into memory and the memory isn’t large enough to hold the register’s value (putting it into a char variable) that might cause problems.
Back to the original “is it dangerous?” if your plane altimeter value overflows and the auto-pilot now thinks you’re at 0 above ground and says CLIMB - NOW when you’re really way up in the air, who knows what could happen? Dangerous all depends on the application.
Alot.
A lot.
Thanks for your tutorial,
now i’m able to make my own String, Array, etc classes similar to std::string and vector after 4 months learning c++
Thank you very much.
I have a question- if long and int are both the same amount of bytes, do they hold the same amount?
Yes.
Another great set of examples, thanks.. 🙂
Memory is ALWAYS a huge issue. Modern games usually have more stats or more monsters to keep track of, so doubling or quadrupling the memory needs, just because you can, is never a good idea. Designing good rules usually allows to reduce the height of stats, rather than extend it.
That is actually a really difficult question. 🙂.
From the line "Using an unsigned instead of an int to gain one more bit to represent positive integers is almost never a good idea." what I understood is that unsigned integers save 1 bit in memory because their value is always positive and there is no need to use an extra bit to decide whether the value is going to be positive or negative. Am I right? Forgive me, if my English is not so good.
One comment for this tutorial in my language (Hindi):
Mast hai bhai…
That means…
This tutorial is awesome bro.
Unsigned integers don’t really “save 1 bit in memory”, they just put their bits to use in a different way.
If you look at the range for an unsigned 8-bit number, you’ll see that it’s 0 to 255.
If you look at the range for a signed 8-bit number, you’ll see that it’s -128 to 127.
Both signed and unsigned numbers use all 8 bits to represent 256 possible unique values. It’s just that the range of numbers they can represent is slightly different.
It’s better to use unsigned rather than signed, and here’s why. RISC processors like the 8051 don’t have multiply or divide instructions so it has to be done with a library. When multiplying (or dividing) signed values, the function has to do the following:
1) Extract the sign bits for both the multiplicand and multiplier
2) Convert both values to unsigned
3) Perform the multiplication
4) Use the saved sign bits to find the sign of the product
5) Apply the sign to the product
When multiplying (or dividing) unsigned values, the function has to do the following:
1) Perform the multiplication
If the application is time critical, it’s better to use unsigned to eliminate a bunch of unnecessary steps. Even if your processor has the signed multiply and divide, it’s a good habit to not use something if you don’t need it.
As for "Attempts to ensure that some values are positive by declaring variables unsigned will typically be defeated by the implicit conversion rules.”: Using signed variables to circumvent implicit conversion rules is just bad programming. You should know the rules and know what will happen if you mix unsigned and signed variables in an expression. And you should always use explicit casts when mixing variables.
I work with an embedded 8051 project that has about 50,000 lines of code. We have hundreds of variables, mostly unsigned. My estimate is we have no more than a couple dozen signed variables, and they are used for incrementing (1) and decrementing (-1) when using stepper motors. Timing is critical so using signed variables is out of the question because we use a lot of multiplication and division. I’ve seen the generated assembly code and unsigned is clearly the winner.
> It’s better to use unsigned rather than signed
No, it’s not. For your very specific performance-critical use case on a processor that has crippled handling of signed values, you might make the call to favor unsigned over signed for performance reasons.
But for general computing, the best minds in the field have decided that using signed is safer than using unsigned. Most modern processors support both signed and unsigned arithmetic operations natively, so the performance difference between the two is negligible. Even knowing the rules about how signed and unsigned values interact, it’s easy to get into trouble, especially if you mix them (which can happen inadvertently). It’s better to program defensively and optimize later where needed.
The C++ style guidelines from Google explicitly state, .”. Those Google guys are pretty smart -- they must have had a good reason to include this.
There are actually fewer error states for unsigned numbers than signed; overflow on signed is actually UNDEFINED. That means anything could happen at all. Plus, using the negation operator (-) on a minimum-value signed number is also undefined. I’ve seen it both ignored entirely, AND also sudden and unexplained program termination as a result.
gcc silently ignores that with default settings (at least my obsolete 4.4.5 version does - it’ll print the resulting x as -2147483648, whereas it prints -5 as 5), whereas I was actually getting program termination out of MSVC compiling a Windows-binary. Neither is an acceptable answer. There actually ISN’T an acceptable answer as the correct number is 2147483648, which cannot be represented by signed 32-bit integers. Keep in mind an abs() macro is probably using -x in it.
Undefined stuff is especially nasty as "modern" compiler writers (and that goes in quotes, MSVC and gcc struggle to show you where an error happened, whereas SAS/C usually points directly at the offending place in most cases.. modern != better necessarily) will often optimize away undefined behavior, even if it’s actually VALID on the target platform.
The only real error state to an unsigned value (assuming you aren’t mixing-and-matching with floating point and signed, which brings in all the error states for those two nasty number systems) is dividing by zero…which is present in all other representations too.
Plus unsigned values have some cases where you can skip tests
In the example above, there’s no need to test to see if u >= 0, as it always is. Note that it may not be the correct buffer in either case, as there’s no error states for the functions.. a user might have typed 99999999999999999999, for instance. However, the stack won’t be smashed in either case, but the unsigned case involves one fewer comparison (comparisons and branches will NEVER get cheaper).
I personally like to use an unsigned integer to represent values in the range of 1.0 > x >= 0.0. This works especially well for angles that have to be restrained to a 360-degree circle, as I can literally just add or subtract from the unsigned value and let overflow handle the rounding. I don’t have to do crap like x = x%360 or other modf/fmod performance-eating error-prone nonsense. a 32-bit uint has a higher resolution than a single-precision float (it has four effective bytes of mantissa as opposed to three for the float in this case), plus the rest of the math tends to be fp-heavy and the integer execution units/ports are idle anyways, so bonus performance. Doubly so when I can do something like SineTable[ Angle >> 16 ] instead of sin(blah)…that’s actually faster AND getting faster (memory is improving faster than CPU performance these days -- it was only two times faster in the Core 2 era, and for my i7-3820, it’s six times faster). All of that would be invalid/undefined for a signed integer. The only real drawback is that 15 degrees is 178956970, but then again, the standard math library works in radians, which would be 0.261799 (in single-precision.. approximately)..
There are some gotchas for unsigned in some common uses for novice programmers, but that’s why they’re NOVICE. Stuff like for(u=9;u>=0;u-) -- u>=0 is always true (using the "u" from the example above naturally). That would have to be rewritten to use a signed integer, or an offset, or a do/while(u!=0) sort of construct… assuming that 0 was intended to be used in the first place. The novice programmer likely included zero by mistake there anyhow 😉
BTW, just because ‘smart people’ do something, doesn’t mean it’s right. My Galaxy S7’s software (Android -- google *cough*) is a good example of that. Uses over 2.1 gigabytes of RAM (out of 4), and is less responsive than a significantly hardware-inferior iPhone.
Anyhow, I’ve been otherwise enjoying your article, even if it is biased towards new users. It’s pretty clear and well-written. A current project requires some integration with C++ code, and this has been helping me update my C++ skillset from the old pre-namespace era. When I first started on that project, I’d thought that Perl had somehow attacked the source 🙂
Would you say it is a good idea to work with signed integers even if it is unlikely the number would be negative, just as a precaution? Or maybe allow it but have a warning print to the screen?
Name (required)
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Setting up for a lesson
Step 1 - Install Microsoft Visual Studio
If you don't have a it on your system then grab a copy of Microsoft Visual Studio Community 2015. Its totally free and it has most of the features of the full version and supports everything we will need to extend Orchard.
Step 2 - Install Git Extensions
Every developer should have Git Extensions installed on their machine.
This is the easiest way to quickly clone the Orchard source code onto your dev machine. It's the easiest way to keep up to date when new code is released. As a bonus, if you haven't got to grips with Git and GitHub, this will gently introduce you to the whole process.
If you need detailed help installing Git Extensions and cloning the repository this process is described in the setting up a source enlistment tutorial in step-by-step detail.
Step 3 - Set up a braces management extension
This step is optional but recommended.
You will probably have noticed that Orchard code has the braces on the same line as the definition. It looks like this:
namespace Orchard.LearnOrchard.Example.Models { public class ExamplePart { } }
Instead of what you normally see with .NET code where the opening curly brace is on its own line, which looks like this:
namespace Orchard.LearnOrchard.Example.Models { public class ExamplePart { } }
The placement of the opening curly braces on the same line is a requirement listed in the code conventions document for Orchard CMS.
You can do it by editing the Visual Studio settings manually but this will apply it to all of your solutions whether they are Orchard-based or not.
A better solution is to let a Visual Studio extension manage this for you. Orchard supports two options out of the box:
ReSharper. (Paid) This is a powerful extension with many more features than simple brace management. It is recommended that you check this extension out if you haven't used it.
Rebracer. (Free) Orchard also supports the free Rebracer extension. This extension simply manages your brace configurations for you on a per-solution basis.
Install one of these two extensions.
Step 4 - Clone the repository to your machine
You should always work on a fresh copy of Orchard when you're following a tutorial, testing out new 3rd party modules and themes from the Gallery, or working on your own modules to keep things clean.
Database tables are going to be modified, you will make changes in the admin dashboard, you will make mistakes and change things a second time. When you install new modules or themes they can inject their own data into your database and adjust built in content types. Even if you deactivate them again these changes can get left behind.
To stop this detritus getting into your main site you should always use a fresh copy to test things out in.
With Git Extensions and Orchard's support for SqlCE databases you can have a fresh copy of Orchard up and running in just a minute or two.. Unless your lesson says differently, select
masterfor the latest stable branch.
The rest of the settings can be left as-is. Click
Clone.
Git Extensions will now pull down the files from the remote repository hosted on GitHub. This process will take a minute or two while the files are downloaded to your hard drive.
Tip: If you find yourself following this process often you can greatly speed this up by cloning from a local copy.
To do this create a fresh clone on your hard drive and keep that as your reference copy. Then, instead of using a URL in the
Repository to clone:field you can point at the location of your reference copy stored on your local hard drive.
The whole clone process should then take just a couple of seconds.
Step 5 - Complete the initial site setup process
Now you just need to follow these last few steps to create a default database and set up the admin user:
Open Visual Studio
Click
File,
Open,
Project/Solution...
Navigate to the folder you cloned the repo into
Open the main solution file located at
.\src\Orchard.sln
Ctrl-F5to start the project without debugging (it loads quicker)
You will now be presented with the
Select these options:
- Site name: Enter any name you like that's related to the lesson you're following
- User name: admin
- Password: password
- Data store: SQL Server Compact
- Recipe: Default
Click
Finish setup
The site will now do its initial prep and present you with the
Welcome to Orchard! start screen.
Preparation completed
You can now return to the lesson that brought you here. | http://docs.orchardproject.net/en/latest/Documentation/Setting-up-for-a-lesson/ | CC-MAIN-2017-26 | refinedweb | 783 | 68.6 |
Dear All,
I am new to Aspose,
I was trying to convert one of my pptx file to a jpg image.
I found some sample code from the Aspose site.I downloaded the requirements.
Please see my codes below.
try{
PresentationEx pres = new PresentationEx(“D://EmbeddedObject_excel.pptx”);
//Access the first slide
SlideEx sld = pres.getSlides().get(1);
//Create a full scale image
BufferedImage img = sld.getThumbnail(1f, 1f);
//Save the image to disk in JPEG format
ImageIO.write(img, “JPG”, new File(“D://Sample.jpg”));
} catch (IOException e) {
e.printStackTrace();
}
From the above code i got a jpg file.But it doesnt contain my required ppt. instaed it contain a green colour rectangular box.
Dint get why it is coming like that,
Your extreme help will be appreciated,
Thanks.
Hi Shajeer,
Thanks for considering Aspose.Slides.
I am afraid, you may be missing reference to JAI and JAI Image I/O jar files. Please proceed to this documentation link and add these jar files reference in your source project. If the problem still persists then please share the source presentation file, so that we can help you further.
Thanks and Regards,
After adding the jar references to the source project still it displays the same colour box.
Please find attached my input as test.pptx powerpoint file and my output as i got after compiling the below code as Sample.jpg.
I need an exact image of the ppt. Sometime my ppt will contain more than one slides.So the output woluld be like Sample1.jpg,Sample2.jpg etc.
Please find below Code,
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import com.aspose.slides.pptx.PresentationEx;
import com.aspose.slides.pptx.SlideEx;
public class PPTTest {
public static void main (String[] args) throws Exception {
try{
PresentationEx pres = new PresentationEx(“D://test.pptx”);
SlideEx sld = pres.getSlides().get(0);
BufferedImage img = sld.getThumbnail(1f, 1f);
ImageIO.write(img, “JPG”, new File(“D://Sample.jpg”));
} catch (IOException e) {
e.printStackTrace();
}
}
}
Thanks for your help.
Hi Shajeer,<?xml:namespace prefix = o
I have been able to verify the issue as specified by you and it seems to be an inconsistency in Aspose.Slides for Java. An issue with issue id 15523 has been created in our Issue Tracking System to resolve the issue. This thread has also been associated with this issue, so that you can be automatically notified as soon as this issue is resolved.We are sorry for your inconvenience,
I’m also seeing the exact same issue–replying so I’m notified when it’s updated.
I have reported same issue several mounth ago but still have no solution.
Dear All,
Our development team is working hard on resolving the issue. We will be very happy to share the findings with you, as soon as the issue is resolved.
We are sorry for your inconvenience,
The issues you have found earlier (filed as 15523) have been fixed in this update.
This message was posted using Notification2Forum from Downloads module by aspose.notifier. | https://forum.aspose.com/t/pptx-to-image-not-working-properly/93529 | CC-MAIN-2022-21 | refinedweb | 511 | 61.83 |
iSCSI is a protocol that enables clients, called initiators, to send SCSI commands to SCSI storage devices, called targets, on remote servers. It is a Storage Area Network (SAN) protocol that enables the consolidation of storage into data-center storage arrays, while providing hosts with the illusion of locally attached disks. The use of iSCSI does not require special-purpose cabling. Instead, communication is run over long distances by using the existing network infrastructure.
Observe the following guidelines for configuring iSCSI storage in an Open HA Cluster configuration:
COMSTAR – Only COMSTAR based iSCSI target implementations are supported in an Open HA Cluster 2009.06 configuration.
iSCSI target location – A disk that is exported as an iSCSI target must be a local disk that is directly attached to the cluster node that hosts the iSCSI target. You cannot use a disk as an iSCSI target if it is hosted by multiple nodes or if it is not directly attached to the cluster node.
Topology – Configure the hardware connections as shown in the following diagram. This diagram shows a two-node Open HA Cluster 2009.06 configuration that uses COMSTAR and a failover ZFS storage pool to provide high availability. The arrows indicate iSCSI connections. One or more connections provide a path from each node to the same disk on Node 1. In the cluster DID namespace, this becomes a single DID device, with paths from both nodes. Similarly, one or more connections provide a path from each node to the same disk on Node 2. This creates a second DID device. The mirroring of these two DID devices by using a ZFS storage pool creates a failover ZFS file system in the Open HA Cluster configuration. | http://docs.oracle.com/cd/E19735-01/820-7821/girgb/index.html | CC-MAIN-2014-23 | refinedweb | 285 | 53.71 |
On Saturday 09 September 2006 12:35 pm, you wrote: <snip> > But mostly I'm advocating going to the other extreme: drop GUI as a > topic and just code up a namespace, reach into the grab bag for > functions, like f(x) or cos(x). We pretend kids don't have the > background, but if they did *any* work with a TI calculator or an > algebra course, they know about functions, at least tacitly. > > My prerequisite for my Saturday Academy class is algebra only, and > typing above 30 a minute really helps (a lot of 'em are getting that > from chat rooms these days, buy a typing drill for home). > As I said below, I'm all for this kind of interaction, and when input and raw_input go away, I'll probably do more of it. > > > > I can define it for my gnu math teachers, the people I work with in > South Africa for example. This, of course, misses my whole point that you can't define "state of the art" in "programming for self" for others (me, for example). > > use interactive text input. Why? Because the whole point is to make > > something routine and automatic. Why would I write a program that forces > > me to: Start Python > > Import a module > > Recall what I'm suppose to invoke and what information it needs. > > Sounds like your "program" is one of these top-to-bottom > glued-together script thingys. We don't teach that way. Modules are > grab bags, perhaps containing rich data structures (lat/long > dictionary say). Modules define namespaces, like boxes of chocolates > (Forest Gump understands). First up, I was not talking about the way I teach, but the way I program to automate my environment. To use your terms: defining state of the art in programming for myself. Your model is less convenient for these tasks than the one I describe. Further, I highly doubt that the script I'm writing for those purposes are any less modular than they should be to get the job done. Namespaces are a wonderful tool (which I use liberally), but don't confuse being modular with being good. There's plenty of bad modularity too. > This need to glue it all together with some main() -- why? We compete > with that idea of "programming." We're not a part of *that* > particular conspiracy. Umm, the point of my program is to automate something. That's why I glue it together. If I don't do that, I haven't solved the problem I set out to solve. I'm only 'conspiring' to solve the problems I have at hand. > Last week, we were working on phi and the fibonaccis. Let's get back > to that now. Pull out a file drawer (import) and behold: all our > favorite specimens (even the bugs are back). Great. Fantastic. It has nothing to do with what I was describing. I have plenty of these experimental evnrionments as well. > > >. > > Yeah, we don't like that style. OK for you, works for your students, > I think you're probably a dynamite teacher. But... we still don't > like that style. Again, I'm talking about writing a useful tool to automate some mundane task. What's "not to like about that style"? Should I make automating that task harder so as to fit your pedagogical style? My arguments had nothing to do with how you or I go about teaching math. > Later on maybe, if/when they're committed to CS. But this is just > basic numeracy here, and they already know about functions from > calculators. > > import math > math.cos( 90 * math.degrees) > > -- that's what a first class might include. If what stops 'em isn't > the Python syntax, but the trig, then we go over the trig. Basic > numeracy. All as a bundle. Not your grandfathers math class (but > some hoped it'd be for their kids -- remember when the future was, > well, futuristic?). Again, this sounds great. I like it, and I'm glad you're doing it. And you don't need raw_input (or input). But having input available in no way impedes this, and for the tasks I'm describing, lack of the same is a hindrance. > >. > > And I'm saying using the shell to trigger namespace events is (a) > closer to what a GUI is doing and (b) is fully usable I/O. Use doc > strings to remind about inputs. raw_input prompts are the new goto > (to be avoided if possible). But it's less convenient and therefore less useful for producing real tools that automate tasks. You are talking about a different form of programming and pedagogy. Docstrings do not solve the problem I describe, because they are passive. I have to go look at them again to remind myself how to use the tool. If I write a program, the program itself knows what it needs and when. > > > > Right, but I see that as a self-serving analogy. You're *defending* > the status quo. Notice how CP4E goes for like "riding a bicycle" and > "driving a car". Anyone can do it, no big deal. Well far be it for me to suggest an anology that supports what I'm defending :-). Is it true that anyone can write a working GUI program? I don't know if that's any more true than that anyone can comprehend quantum mechanics. But let's use your example: does the fact that we expect everyone to be able to drive a car mean that we _shouldn't_ teach them to ride a bicycle? And shouldn't we even go a step further and take bicycles away because they might learn this useful mode of transportation which is _not_ car driving? Because it sounds to me like this is exactly the argument you are making w.r.t. input. > I think CS has a reflex to fight "debasement" of programming into a > "what your grandmother knows" skill. But that's what I *want* to have > happen, and expect grandmothers *will* have those skills in the not > too distant future. > I hope what you want comes to pass. I can assure you that CS academics have nothing whatsoever against programming as a universal skill, since we profess to believe that CS is much more than programming and say so at every opportunity. I, for one, can't wait to add a bunch more upper-level courses to the major when programming is taken for granted. I'm just not holding my breath... > Latin moms in Rio will tell The Monkey to block those Evil Toons > (point and click yes, but they custom-skinned the GUI, know how it > works from hours study. What, working class folk with the free time to > study what they used have to pay for, plus hold down a job? What a > concept! OK, now I just have no idea what you're talking about. Probably that's because I'm stuck in my dino-world. > > > that really make sense? The fact that there is more advanced stuff that > > they will surely learn in due course is in no way a justification for not > > teaching simpler, useful concepts first. > > Nothing much simpler than import math, using the names. Raw_input is > difficult by contrast. For Gnu-math maybe, but not for the types of useful artifacts I suggested above. And Input is no more difficult than typing expressions (as I've explained) which I assume is the starting point for your Gnu-math. > Why don't calculators have raw_input? They can't do I/O? How about > dashboards? Cockpit of an airplane. You are confusing what's easy for the user with what's easy for the programmer. Underneath, of couse, a modern calculator _does_ have the equivalent of raw_input. It grabs the string constructed in the display, parses and evaluates it. The user interface is all extra baggage built on top of that. From the programmer's standpoint, that extra baggage is more effort. If I already have a console, I can get the useful tool without the extra effort. > We use control surfaces all day long. That's what a namespace is, an > API. You don't need to tie it all together with some main(). This > isn't a script. It's a place to do work. Namespaces are like > studios. Event driven. More GUI, less "programming" (in the 1960s > sense). > Right on. But what I'm talking about _is_ a script. > > > I'm saying this'll all be common knowledge soon. > > > > Define "soon." I see the same demographic as Brad Miller. My students are > > freshman in college who have never programmed. And frankly, I'm OK with > > that. > > And frankly, I'm not. High school too wasteful. If it's really about > sports, which is OK with me, lets do more sports camps. But for kids > who want academic rigor (another kind of sport), it's just not OK to > not even *offer* OO by the end of high school. What if they're not interested in it? I know in your world the schools are hopelessly outdated because they don't teach Gnu math and OO. I'm happy if they teach our children to read and write well and to do some mathematics. I don't even care much what math they do, just as I don't care much what they read and write about. Throw in a basic understanding of science, and a healthy dose of getting along with others, and you've got a curriculum. Of course, one can argue schools are not doing this now, but I don't see how teaching them to program frees up more time for what I consider fundamental skills. If your Gnu-math is better at teaching them some mathematics, that's great; I'm all for it. But I don't care if it teaches them OO. One of the reasons for the conservatism of the educational establishment is that it can be devilishly hard to determine what the core skills are that all educated people should have (unlike other countries, our K-12 system attempts to be universal). You specifically mention OO and Python, but education (currently in the US) is a 13 year program. Will OO still be the dominant paradigm in a dozen years? I have a hunch not. OO institutionalizes side-effects (state change), and side-effects are a bane to managing concurrency. With multi-core, multi-processing machines seeming the most obvious routes to increased computing power, it could be that OO looks as old-fashioned as gotos in a dozen years. Is OO some fundamental/essential skill? I don't think you can measure the value of an education in terms of what specific technologies are learned (and OO is just a technology). Fundamental education is not about what technologies we teach or what technologies we teach with; it's about what kind of citizens we raise. Give my children a good teacher that can really communicate and get the kids excited about _learning_, and what in particular they learn doesn't matter so much. They have their whole lives ahead of them to become great at whatever is meaningful to them. > If USA voters want to keep that status quo, fine, but don't think the > rest of the world will think twice about thrashing us in the job > market if so. Or were we planning to use the Pentagon to keep the > rest of the world stone aged, while we went on being mental couch > potatoes. If so, think again. > Praise the Lord we have television. If the schools have decided to > rust in irrelevance, letting it be OK that globalization passes us by, > then we can do what we did in Sesame Street, except at a much higher > level (still using puppets though -- some of them CGI). This is an interesting juxtaposition of paragraphs. Many studies suggest that TV is the number one contributor to mental couch potatoism. I'd much rather have my kids spending time in our current (backwards, dino-era) schools (at least the ones we have here in Iowa) than watching television, no matter what show is on. Real interactions with live caring people in a social setting is what children need most. No truckloads of DVDs, screencasts, or electronic curriculum of the foreseeable future will change that truth. Until we have truly intelligent machines, there is no substitute authentic interpersonal interaction in terms of communication bandwidth. Education is at its core just communication. > Our Snake with __rib__ syntax makes fun cartoons on TV. It slithers > around like Kaa, eating stuff (eat method). Hah hah, the 3rd graders > laugh. Gnu math is just better. > I have no idea what that paragraph is about. Anyway, this is really, really my last post on this thread. --John ps. And I mean it. -- John M. Zelle, Ph.D. Wartburg College Professor of Computer Science Waverly, IA john.zelle at wartburg.edu (319) 352-8360 | https://mail.python.org/pipermail/edu-sig/2006-September/007072.html | CC-MAIN-2017-30 | refinedweb | 2,168 | 74.69 |
:).
Interesting, generating a kind of tad cloud from a speech. Gates vs. Jobs: Keynote text analysis, 2008 edition.
Great :)
Nice train map from Information Architects, from Japan.
Interesting article from Wired, The Life Cycle of a Blog Post, From Servers to Spiders to Suits — to You
I also liked the navigation design.
Seems that Brian Peek put the seed on coding4fun, but the demonstrations from Johnny Lee are awesome.
I have to try...
I'm not an expert on Exchange, but I have several projects with Exchange involved, so that poster seems useful.
Also, a printed version on the TechNet Magazine.
Finally.
Architecting systems you can build from scratch or evolve an existing one. A lot of pros and cons on both, but one of the pros of the new ones is how clean can be.
I have been for some time with SlaterLabs, building a core banking solution in .NET. As soon as we started to have the first bits we went to a HP lab in Stuttgart to see if we can compete on the big leagues.
The figures were amazing, more than 7,000 business transactions per second with a average response time under .1 second.
There is a new tool for editing XML documents, XML Notepad 2006. I haven't still used it too much, but I'm giving it a chance.
I have an environment with BizTalk 2004 and the MQSeries Adapter which I’m upgrading to BizTalk 2006. I have updated the BizTalk server and a development computer and tried to create a couple of ports. I had this error when trying to configure the MQSeries port, when opening the Queue Manager combo in the Queue Definition dialog box: issue is pretty simple; the MQSeries agent running on the MQSeries server needs to be updated also. The BizTalk setup has the option for install the MQSeries agent under the “Additional Software” branch.
Also, the MQSeries Manager needs to be updated to the Windows 2003 Server SP1 and some other new requirements.
After that I still had the message:
Retrieving the COM class factory for remote component with CLSID {86E96D72-0011-4B28-B1AC-BF52AB47F1B4} from machine failed due to the following error: 80070005.
Retrieving the COM class factory for remote component with CLSID {86E96D72-0011-4B28-B1AC-BF52AB47F1B4} from machine failed due to the following error: 80070005.
And a new “Access Denied” appeared on the old BizTalk 2004 machine. So, the Windows 2003 Server SP1 has something to do here. My first guess was about a new default security on DTC. DTCPing wasn’t running, so I did the calls anonymous and some registry changes on the client, DTCPing run perfectly but I still had the 80070005 error.
Finally I noticed a new local group called “Distributed COM Users”. Seems pretty straightforward. I added the Visual Studio user to the group for configuration and the BizTalk host user for execution, and everything running!!
If interested on running different BizTalk versions against the same MQSeries manager, the new MQSeries Agent runs side by side with 2006, 2004 and 2002 BizTalk releases. Also interesting, this new release has a wizard for configuring the COM+ Application –which avoids some common errors-, named MQSAgent2.
A.
We have launched a new community site about architecture,
The site content currently is some podcasts (the ArCast series from Channel9), articles from MSDN, the Architecture Journal and some blogs.
Also interesting, they are using 4 personas for the different kind of architects, Solution, Infrastructure, Strategic and Industry.
From time to time I have found this error when opening the Biztalk management console: "A connection to Windows Management on \\.\ROOT\MicrosoftBizTalkServer cannot be established: Invalid namespace".
It can be solved executing "mofcomp" on the BTSWMISchemaXP.mof file found on the biztalk installation directory.
Plur?
Probably you already know, but is worth to remember these sites
Microsoft Learning
MSDN Virtual labs
PDC 2005 Sessions
Shows & WebCasts | http://blogs.msdn.com/joselcs/default.aspx | crawl-002 | refinedweb | 651 | 62.98 |
On Measuring Open Source Partner Effectiveness
by jwhatcott Whatcott back to the project, saying:
No Matt, this time your idea stinks,
This way skilled consultants that care about open source and contribute to the community are being punished for doing so, whereas they should actually be getting business back from the vendors, so they can earn money and contribute more on your product you force them to waste more time on the sales side. While the people that just move boxes, don't care if its an open source application or a proprietary package gain more. For them its just business as usual .. selling boxen.
It just doesn't make sense
This concept is just bad for opensource in general, motivated people will stop contributing to products they implement, as they see that their efforts aren't appreciated by the vendors.
There is a clear tension here, and I think it arises out of a lack of clarity regarding what to measure. Kris is uncomfortable with Matt's rubric. It's perfectly reasonable for an open source vendor to favor partners who are the most loyal and make the most contributions to the vendors success and vice versa. But how do you measure loyalty and contributions? The volume of revenue from subscription pull through is one way, but it's only one of many.
If a partner does a project with the software that just blows people away, is broadly written up in the blogosphere and trade press, and substantially raises awareness of the project, should that be taken into account? If the partner makes a groundbreaking contribution to the project, something that really propels the technology forward in a way that will open up new selling opportunities, should that earn them the right to a few leads? If a partner has a guy on staff who is just this amazing heat seeking missile inside the bug queue, taking on the gnarliest issues and coming out with sensible fixes every time, should that count for something?
At Acquia, we're in the process of designing our partner program right now. It's clear to us that selling with and through Drupal solution providers is going to be an important element of our business. Right now we're still gathering information, talking to prospective partners, and iterating on various approaches. So the topics like the one discussed above are very interesting and relevant.
Despite the apparent similarities, we're different from many open source companies like Alfresco and SugarCRM and MySQL in some fundamental ways. Drupal pre-dates Acquia. We didn't invent it, nor do we control it (or want to control it). We have a huge pre-existing community pre-populated with a global network of solution providers who are all potential partners. Most of these companies have built strong businesses without Acquia up to this point, so our challenge is coming up with a value proposition for helping them expand and accelerate their business by choosing to sell our subscriptions as part of their solutions. We have neither the inclination nor the ability to use heavy-handed tactics. We'll be working through persuasion and aligned interests, not compulsion.
Even though our situation is unique, we still need to come up with a scalable and effective means of recruiting, enabling, and supporting partners who share our vision and interests. Given that our time and resources are limited, we're going to have to prioritize our partnering relationships and activities in order to maximize total return (realizing thatmoney is only one element of return). That means we'll need reliable ways of measuring partner effectiveness. So how should we go about that? I'd love your feedback.
UPDATE: Kris has posted a follow-up with some more specific suggestions.
It is unique, but not as
It is unique, but not as unique as you might think. The same issues that we face, you will face, just as Red Hat, JBoss, MySQL, etc. have all faced (and which were communities before they were companies).
My post was taken *way* out of context by Kris and others, who thought I was talking about "sticks" rather than "carrots." I wasn't. I was just talking about ways to steer financial carrots to those who steer financial carrots our way. There was absolutely no mention made of the code carrots that many non-partners provide, and for which I'm very grateful. I simply wasn't talking about that aspect.
You come from a large, successful, proprietary software company (Adobe). You know that business isn't as easy as giving everything away and hoping people pay for recognized value.
As vendors we need to have an open, productive discussion about best practices. I try to do that on my blog, and appreciate your measured response. I didn't appreciate the screams of protest that came back with little substance beyond anger and ire. First, seek to understand. Then criticize. You have done that. I wish others would, too. It would make open source more of a community, and less of an exclusive club that eats its own young. | https://www.acquia.com/comment/991 | CC-MAIN-2016-07 | refinedweb | 855 | 61.26 |
Currently JS_XDRScript serializes principals for each its nested function in addition to the top-level script. Since principals in the nested function are the same as for the script, we should fix and do the serialization only once per top-level serialization.
Created attachment 595705 [details] [diff] [review]
v1
The patch implements that serialize once idea.
Comment on attachment 595705 [details] [diff] [review]
v1
I really like this approach, but r- because of JS_XDRFunctionObject which is (as far as I can tell) provides a way to XDR a script without calling JS_XDRScript. Igor is on the case!
Created attachment 596011 [details] [diff] [review]
v2
That approach with separated principals init phase lead to unnecessary code duplication after accounting for JS_XDRFunctionObject.
So this patch adds a new structure, ScriptShared, that holds the principals and changes js_XDRScript/js_XDRFunctionObject to take explicit ScriptShared argument. This allowed to unify handling of JSScript::filename and principals, eliminate XDRScriptState and simplify CloneScipt implementation.
In the patch I dropped the requirement that originPrincipals must be null if principals is null. That did not allow to simplify anything especially since with the patch CloneScript uses the common principal initialization code shared with xdr decoding. So the patch leaves up to embedding to decide if null principal and non-null origin is a valid configuration.
Created attachment 596173 [details] [diff] [review]
v3
v2 has a bug when checking for presence of principal transcode callback. Our mochitest caught it, but that clearly points to deficiency of our api tests. So in v3 I added tests to check various aspects of principal serialization/deserialization.
Created attachment 596477 [details] [diff] [review]
v4
The new patch improves the test coverage plus changes json test not to output anything if the test is successful.
Created attachment 598007 [details] [diff] [review]
v5
In v4 I forgot in the XDR test to call JSPRINCIPALS_HOLD for the decoded principal. That was not visible as the destroy method were empty. In the new patch I fix that and replace the destroy method with NULL so the code will crash on unexpected principal release.
Comment on attachment 598007 [details] [diff] [review]
v5
In view of changes from the bug 728250 this patch goes to the wrong direction. So I create smaller one that should allow to fix the problems on branches if that becomes necessary while minimizing the changes for the bug 728250.
Created attachment 599371 [details] [diff] [review]
v6
Here is that smaller patch. As before, XDRScript just copies during the decoding the principals. But the patch avoids separated state objects and just stores principals and the filename in JSXDRState. Then principals are transcoded using couple of helpers in jsxdrapi.cpp.
Created attachment 599513 [details] [diff] [review]
v6 for real
The previous attachment had a wrong patch - I forgot to refresh it.
Created attachment 599544 [details] [diff] [review]
v7
The previous version has an interesting problem. In the patch I added a helper class, AutoDropPrincipals, to jsxdrapi.cpp. However a class with the same name was also defined in jsapi-tests/testCloneScript.cpp. On 64 bit Linux that resulted in the definition for the constructor and destructor for the test class to be used for the helper class. There were no warnings from the compiler about that.
So in the new version I have renamed the class and, just to be sure, also put the helper class in jsxdrapi.cpp into the anonymous namespace.
Comment on attachment 599544 [details] [diff] [review]
v7
luke, can you look at the patch? mrbkap do not have time due to the B2G work week.
Comment on attachment 599544 [details] [diff] [review]
v7
Review of attachment 599544 [details] [diff] [review]:
-----------------------------------------------------------------
Nicely done! It would be interesting to see if this produced a measurable decrease in total XDR time in browser startup.
::: js/src/jsapi-tests/testXDR.cpp
@@ +26,5 @@
> + jschar *chars = static_cast<jschar *>(JS_malloc(cx, nchars * sizeof(jschar)));
> + if (!chars)
> + return NULL;
> + JS_ALWAYS_TRUE(JS_DecodeBytes(cx, bytes, nbytes, chars, &nchars));
> + JSScript *script = js::frontend::CompileScript(cx, obj, NULL, principals, originPrincipals,
Perhaps you can just add the jsapi? There is no good reason for it to be missing. That avoids the unexpected call to internals from jsapi-tests.
::: js/src/jsscript.cpp
@@ +722,1 @@
> }
For the local reader, could you JS_ASSERT(script->principals, script->originPrincipals)?
@@ +1724,5 @@
> CloneScript(JSContext *cx, JSScript *script)
> {
> JS_ASSERT(cx->compartment != script->compartment());
>
> + /* Serialize script. */
As long as you are fixing these //s, there are some more below.
:::...)
(In reply to Luke Wagner [:luke] from comment #12)
> :::.
I plan to remove XDRPrincipals and friends in the bug 728250 (part 2 there). So the changes here are temporary to minimize the changes in that bug.
>
> @@ ...)
Again, wait for the bug 728250.
(In reply to Luke Wagner [:luke] from comment #12)
> Perhaps you can just add the jsapi? There is no good reason for it to be
> missing. That avoids the unexpected call to internals from jsapi-tests.
I will add the missing API. But all those versions of compile script seems to suggest to refactor (in another bug!) the API bush into a parameter struct plus a single call to the compile method.
Sweet
Verified for trunk based on passing checked in tests since we have no manual cases / steps for this.
Luke, would the patch apply to ESR10? If not, could it reasonably be backported?
Naively applied, the patch conflicts terribly. I'd also be scared to try to do a manual backporting since I believe this patch was landed in the middle of a slew of patches Igor wrote that totally redid XDR (more than just principals). | https://bugzilla.mozilla.org/show_bug.cgi?id=725576 | CC-MAIN-2016-22 | refinedweb | 927 | 56.25 |
Whether you're simply converting all-caps text to lower case to spare delicate ears, or trying to make everyone sound like the Swedish Chef, simple translation software has been a popular theme of computer environments for years. More sophisticated solutions exist as well. This article looks at the technical issues involved in translating chat messages in Second Life.
While there's certainly plenty of industrial-strength translation software out there, my first notion was to use a simple command-line one. A command-line app that requires little setup is easy to configure and check, and likewise easy to incorporate into another program. I picked Linguaphile (see Resources). While it'd certainly be possible to incorporate one of the web-based translation services, or one of the heavier-duty translation packages, Linguaphile has the key advantage that it is very simple to configure, allowing me to focus on the Second Life viewer code, rather than on translation software. It also has the key advantage over some services that it is free software, available for immediate download, and its license is permissive.
Linguaphile had no installation or build process; it's just a bundle of files and a perl script which uses them. If you run it from the directory the archive is unpacked in, it just works. So the build took a total of about 0 seconds. This was a definite strength.
The Second Life documentation for the chat system is incomplete, as of this writing. The code is mostly found in the llviewermessage.cpp file, which handles messages coming in from the simulator, and in llchatbar.cpp, which handles outgoing messages.
Listing 1. Processing incoming messages (llviewermessage.cpp)
And sure enough, there's the message, which gets unpacked into a small buffer. For starters, just to confirm this, I modified the program to smash the message into all lowercase; it's easy to see whether a message has been changed, and I always worry about going deaf from all the people online who shout habitually. This is presented as a self-contained code block because nothing outside this block ever needs to see any local variables used along the way:
Listing 2. Smashing case
The getStringFast call is from the existing code; I include it so you can see where the modification goes. After a quick rebuild (well, not so quick; I see why they use a distributed build system), I got to test this out. Sure enough, I logged in on the rebuilt client, and said something; my client, receiving the message back from the server, translated it to lower case. That test confirms that this is the right place to perform translations. Next up is the task of running a subprocess; unfortunately, this is not a task you can easily perform cross-platform. On UNIX® or UNIX-like systems (such as Linux® and Mac OS X), it's very simple. First, let's just look at the minimalist call to an external program.
Listing 3. Smashing case the hard way
This may seem a little obfuscated, but it makes perfect sense once you know what it does. Each call to pipe() makes a pair of file descriptors; data written to fd[1] can be read from fd[0]. Our program needs to do two things; first, it needs to write a message to the external utility program, second, it needs to read a response back. That requires a pair of pipes. I named them "wfd" (write file descriptor) and "rfd" (read file descriptor) respectively. In the parent program (which receives the child's process id as the return from fork), the unused halves of the pipes are closed, the message is written, and the file descriptor is closed (this makes the client detect EOF after it reads the data sent). Meanwhile, the child closes the other halves of the pipes, then uses close and dup2 to map them onto standard input and standard output. The child executes an external program; in this case, "tr".
The tr utility reads until it reaches EOF (getting the message we sent), sends the data back converted, and exits, closing the file descriptor. The parent process reads everything available up through EOF back into the message buffer, calls waitpid() to reap the now-deceased child process, and continues.
This is just a proof of concept, but now, any program you can call that converts input to output can be used instead of tr. For instance, the aforementioned translating program.
Actually using linguaphile
It would seem like it would be totally trivial to patch in linguaphile. It was close, but there were a couple of problems. One obvious problem is that the original code, for smashing case, simply assumes that the output message is the same length as the input message. This is not one bug, but two! The first bug (and I hope it's the one that leapt out at you immediately) is that a message which becomes longer could overrun the message buffer, allowing a carefully crafted message to smash the stack and potentially execute dangerous code. But what happens in the case where the translation is shorter? In early testing, using German to English, the German word "mich" got translated to "mech". Why? Linguaphile's translation ("me") was being overwritten onto a buffer containing "mich"; the result was "mech" (emphasis mine).
The corrected read code is simple enough:
Listing 4. Terminating the buffer
The "-1" is to avoid smashing another object with the terminating null byte; it would also work to just make the buffer a byte longer.
The code to call linguaphile is simplicity itself:
Listing 5. Calling linguaphile
The chdir call is used so that linguaphile can find its distribution package materials; without these, it won't run. The "-q" option suppresses the initial message identifying which languages are being translated. In testing, I just set the default source language in the code. For a production environment, you'd obviously want to specify those as arguments, and provide some way to change the translation layer.
Linguaphile's a fairly simple word-for-word translation program; it just passes unknown words through without alteration or marking. However, it did the thing that was most useful for getting this in place; it worked as a command-line app out of the box. If you desperately need to talk to someone whose language you don't know, an application like this could be enough to get you stumbling through.
One of the frustrations in pitching open source is the difficulty of convincing people not yet familiar with it that it matters. I just took a major application consisting of thousands of lines of code, and got a working proof of concept of a plug-in translator architecture working. It's pretty rough, but if I desperately needed to talk to someone in a foreign language, this might be enough to get a few concepts across. It also changes the nature of the problem; now that a way to translate incoming messages has been established, working on improving the translation is simple and nicely modular; the external program can be any program, although you'd want a responsive one; a web-based service might be problematic.
The version presented so far is far from production code. It runs only on UNIX platforms (Linux, OS X, FreeBSD; not Windows®). It's woefully inefficient, spawning an external application for every line of text it processes. There's no runtime user configuration, and it doesn't provide for any translation of outgoing text. It's a proof of concept.
Each of these issues can be addressed. The spawning overhead is harder to fix than you might think; the default behavior of handling input and output data in blocks makes it easy for the application to enter a deadlock waiting for linguaphile to send data back, while linguaphile is waiting for more data from the viewer. The hard part is that there's no trivial way for the viewer to know when the client is done sending data, without waiting to see if more data come along. Inserting an arbitrary delay is hardly ideal, either. A real solution to this would require, at the minimum, the addition of some kind of sentinel value (probably a newline) to the message, and then checking for the sentinel value while reading data from the pipe. Another solution would be to prefix incoming data with its length. All of these are more complicated; the big appeal of the original version is that the read system call will always return once it hits EOF, which is generated automatically when the client program completes and terminates.
Runtime user configuration might be a little easier to deal with. Since the translation program is already messing with incoming requests, it makes sense to add it to outgoing requests, and along the way add a feature of intercepting IRC-style "/" messages. By convention, assume that you always want to type and read in the same language. So, all you need is a pair of language settings; one for the language people will be talking to you in, one for the language you'll be talking in. I nominate /speak and /hear, which were (as of this writing) not already in use as commands in the existing emote system.
Communication goes both ways
The code I am about to present is ugly in a few ways. It works, but it's not a clean solution. The focus here was on minimal intrusion into the Second Life code, not on an elegant design. Still, it works. The goal was to add two-way communication to the Second Life chat system; that is, translate outgoing material into a language, and incoming material from it. The interface I designed was to add two "emotes", /speak and /hear. The usage of these is ambiguous; "/speak" is the language you type and read in, "/hear" is the language that other people send to you, or receive from you. If you "/speak en" and "/hear de", you write "book" and the other party hears "buch"; if they say "buch", you hear "book".
My solution to keep this isolated was a single function with static local variables to hold the language type. The function is a close relative of the code previously presented in llviewermessage.cpp:
Listing 6. The translation function
The most significant change to the actual translation logic is the addition of the -s (source) and -d (destination) flags to linguaphile. These are set based on the current values for the hear and speak variables, and whether the message is "outgoing". The rather awkward calling sequence lets you specify languages with one call, or a message to translate with another. It's ugly, but it doesn't pollute the global namespace. The assumption that all language codes are two letters is actually wrong, but many of them were, and it was good enough for testing. There's no real error-checking here; it might make sense in production to add return codes to translate_in_place and some kind of diagnostic output for the user. The essential algorithm is clearer without it, though. The code which calls this to set these variables goes in llchatbar.cpp, in the LLChatBar::sendChat() function:
Listing 7. Handling the /speak and /hear emotes
This code is ugly beyond words, but, as long as useful arguments are given to it, it does what is intended; it modifies the "hear" and "speak" values in the translation function. Finally, a call to the translator goes later in this function. The utf8_revised_text variable holds the text as modified by the viewer's native "emote" system which detects strings like "/smoke" and turns them into visible actions.
Listing 8. Translating outgoing text
With this code in place, the system does what you expect; on the default settings, if you use a word that linguaphile can translate, the word is translated. Other words are left alone. You might not realize it's working right away, as your translated words are translated back when the game echoes your statements! I did find a corner case, though; with the default English/German translation, where "table" gets translated to "tisch", but "tisch" doesn't get translated back to table.
The code's still rough; it needs error checking to indicate what languages are known or unknown, and of course, it wouldn't hurt to buff the translation engine. However, the essential goal, of creating something that could let you talk to someone who doesn't speak your native language, without any effort on their part, has been met. Don't use this in production; if you give it an invalid language code, it may well simply eliminate all incoming or outgoing text, or otherwise act up. There's no real handling of translation problems, and there's no error-checking. This is a proof of concept; don't rely on it in real life. (Or second life, for that matter.)
Looking around the system and modifying it has been enlightening. The Second Life implementation seems to be fairly well organized, but not perfectly. For instance, the logic to handle users using "/me" in messages to indicate actions ("/me says hi" turns into "Yourname says hi") occurs in more than one place. Still, it's consistent and fairly easy to find. Names are well-chosen and code doesn't generally try to poke around in class internals.
That speaks to a good development model, and one well suited to an open source release. Modules are modular; that's a good thing. It's fairly easy to find the right place to make a given change, and the system provides a broad range of helpful tools, such as the llinfos stream. Years of playing around with other peoples' code have left me generally skeptical, but in this case, the experience was rewarding and fairly fun. Compared to other projects I've seen, the code is quite good; I find myself wondering if one of the biggest objections to open source isn't just that some companies don't feel their code would withstand careful scrutiny.
Learn
- Read more Second Life articles on developerWorks.
- The Second Life Open Source portal is the place for information about the open source Second Life client.
- The Second Life open source client build instructions for Linux; note that these are stored on a wiki!
- The SCons home page has a fair amount of information, and even a little evangelism.
- Linguaphile is a simple translation program.
- Wikipedia reveals that JFK never actually claimed to be a jelly doughnut, funny though it would have been.
-. | http://www.ibm.com/developerworks/linux/library/l-second-life-3.html | crawl-002 | refinedweb | 2,442 | 60.95 |
We're going to explore various uses of the Arduino MKR 1400 GSM for cellular projects! From wardriving for cell towers to connecting to IoT platforms!Objectives:
- Activate Hologram.io SIM card
- Install Arduino IDE along with MKR 1400 board definition, MKRGSM and ArduinoMQTTClient libraries
- Set up the Arduino MKR 1400
- Test SMS and GPRS connections (to verify everyone is in a workable state)
- Cellular wardriving example
- Network hopping
- Use MQTT over cellular to connect to an IoT platform.
We'll provide Free Credit codes, so you wont have to put in any billing information for this workshop!
Its important to do this part first so that your SIM has time to activate as we set up our coding environment.Install Arduino IDE
Download the Arduino IDE at the following link. We will not be using the online code editor for this project. MKR 1400 Board Definition
- Open Arduino IDE
- Go to Tools > Board > Boards Manager
- Search MKR and an entry for "Arduino SAMD Boards" will show up, install that
- Open the Arduino IDE
- Go to Sketch > Include Library > Manage Libraries
- Insert the SIM card into the Arduino MKR 1400 as shown above
- Attach the antenna
- Plug in the battery (Needs to be at least 1500 maH)
- Connect the USB cable
- Open the Arduino IDE, select "Arduino MKR 1400" in Tools > Board
- In Tools > Port select your board (it should be obvious which one to select)
This example demonstrates quickly jumping to different carriers on the fly. It scans and prints available carriers to the serial monitor and waits for user input.
The custom function "jumpCarrier" sends AT commands directly to the modem.
Available Commands:
"att" - AT&T 3G
"tmo2" - T-Mobile 2G
"tmo3" - T-Mobile 3G
Copy the code from the above link into a new sketch, upload, and open the Serial Monitor and give it a try!
A combination of this method and the Wardriving example could be used for some interesting network exploration shenanigans...Test SMS
- In Arduino, open Examples > MKRGSM > Receive SMS
- Click upload!
- Click the magnifying lens icon to open the Serial Monitor
- Go back to dashboard.hologram.io and select your device
- Click the "via SMS" tab under "Send a Message"
- Type some arbitrary message and hit send!
You should see output in the Serial Monitor similar to this!
SMS Messages Receiver
GSM initialized
Waiting for messages
Message received from:
+44793740520
Hello World!
END OF MESSAGE
Test GPRS
MESSAGE DELETED
This code will simply attempt to connect to GSM and GPRS and confirm success or fail.
APN Information
When connecting to a GPRS network you typically need to include an Access Point Name and login credentials. In the case of the Hologram.io network you simply need to include "hologram" as the APN and leave login credentials blank!
- In Arduino, click File > New
- Paste in the code from below
- Upload!
- Open the Serial Monitor
#include <MKRGSM.h> const char PINNUMBER[] = " "; // APN data const char GPRS_APN[] = "hologram"; const char GPRS_LOGIN[] = " "; const char GPRS_PASSWORD[] = " "; // initialize the library instance GPRS gprs; GSM gsmAccess; and GPRS Success"); } else { Serial.println("Not connected"); delay(1000); } } } void loop() { }
Output should look like this
Starting Arduino web client.
Begin GSM Access
CELLULAR WARDRIVING EXAMPLE \m/
GSM Access and GPRS Success
Ever been curious about the locations of cell towers and coverage?
There are plenty of awesome utilities and functions available in the MKRGSM Library (See Reference), we'll be using the Location and Scan Networks instances for this example. The expected output is triangulated GPS location along with any nearby carriers and their signal strength.
- Copy the code from to a new sketch
- Upload!
- Open the Serial Monitor (starting the get the idea yet?)
Example Output:
GSM networks scanner
Starting GSM location.
Modem IMEI: 357520074233053
> T-Mobile
> AT&T
Current carrier: 0041005400260054
Signal Strength: 13 [0-31]
Location: 38.0000000, -97.0000000
Altitude: 0m
Connecting to MQTT
Accuracy: +/- 4100000m
MQTT (Message Queuing Telemetry Transport) is probably the most commonly used messaging protocol for the Internet of Things. We're going to connect the Arduino MKR 1400 to an MQTT broker to create a very basic IoT application!
Thankfully, the MKRGSM library gives us a client object that is interchangeable with WiFi or Ethernet clients. Meaning we can just drop it into existing network libraries.
We'll be creating an MQTT connection to a public MQTT broker and using it to publish and subscribe to topics. The example sketch provided will print out incoming messages from the subscribed topic to the serial console. It will also periodically publish a sensor value to a separate topic.
We'll use chirpers.io to interact with the Arduino remotely! Chirpers is essentially a fork of node-red that runs entirely client-side in the browser and lets you interact with hardware and web services to build IoT applications visually!Program the sketch!
- Create a new sketch
- Copy into the main sketch
- Create a new tab and name it "arduino_secrets.h"
- Copy in to the arduino_secrets file
The secrets file has all your credentials for GPRS, in this case we only need the APN which is already set to Hologram. We're going to add the MQTT server credentials next.
Broker
: iot.eclipse.org
Port
: 1883
topic
: hologram-YOUR-NAME/to (this is for messages to your device)
publishTopic
: hologram-YOUR-NAME/from (messages from your device)
Upload the code and open the Serial Monitor!Chirpers!
We don't need to create an account to use chirpers.com . Since it runs in your browser, it also saves everything in your local storage.
- Go to
- Drag in an inject node. This is basically a trigger to kick off a message. By default it outputs a timestamp.
- Drag in an MQTT out node. This lets us publish messages. Connect the inject node to it.
- Double click on the MQTT out node. Click the edit icon to add a new broker.
Broker Settings
Server
: wss://iot.eclipse.org:443/ws
- Click update
- Add your hologram/to topic in the topic field.
- Do the same with an MQTT out node to a Debug node but use your hologram/from topic.
- Click Run!
Clicking the inject should send a timestamp to your Arduino MKR which will reflect on the Serial Monitor.
Sensor values from your Arduino MKR should show in the Debug tab on Chirpers!
Your main loop is where you can change what messages you are sending. Bonus points if you do something interesting ;)
void loop() { // call poll() regularly to allow the library to receive MQTT messages and // send MQTT keep alives which avoids being disconnected by the broker mqttClient.poll(); // Set the rate at which we send our values delay(1500); // read the first Analog pin int sensorVal = analogRead(0); // Publish our sensor value mqttClient.beginMessage(publishTopic); mqttClient.print(sensorVal); mqttClient.endMessage(); }
This function at the end of the sketch handles incoming messages
void onMqttMessage(int messageSize) { // we received a message, print out the topic and contents Serial.println("Received a message with topic '"); Serial.print(mqttClient.messageTopic()); Serial.print("', length "); Serial.print(messageSize); Serial.println(" bytes:"); // use the Stream interface to print the contents while (mqttClient.available()) { Serial.print((char)mqttClient.read()); } Serial.println(); Serial.println(); }
Chirpers Flow
If you wanna cheat you can copy this and import it into your flow from the chirpers.io menu. Just be sure to change the topics to match yours!
[{"id":"5199e666.cafc58","type":"mqtt-broker","z":"91xN7kD2zjI","server":"wss://iot.eclipse.org:443/ws","clientId":"","username":"","password":""},{"id":"SDgXjXm8EXM","type":"mqtt in","z":"91xN7kD2zjI","name":"","topic":"hologram/from","broker":"5199e666.cafc58","x":96,"y":117,"wires":[["q-msFzzDVmw"]]},{"id":"q-msFzzDVmw","type":"debug","z":"91xN7kD2zjI","name":"","active":true,"console":"false","complete":"false","x":287,"y":116,"wires":[]},{"id":"mib-Z2IUCWQ","type":"inject","z":"91xN7kD2zjI","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"allowDebugInput":false,"x":101,"y":39,"wires":[["TCHX2DIYKn4"]]},{"id":"TCHX2DIYKn4","type":"mqtt out","z":"91xN7kD2zjI","name":"","topic":"hologram/to","broker":"5199e666.cafc58","x":267,"y":39,"wires":[]}] | https://www.hackster.io/virgilvox/cellular-wardriving-and-other-iot-shenanigans-8d0008 | CC-MAIN-2022-33 | refinedweb | 1,330 | 55.13 |
* A. M. Kuchling | | * Two critical issues for version 1.0 of the XML package are | namespaces and Unicode. I'm not so sure that we need to worry about namespaces. From what I hear enthusiasm about them in the W3C is waning, nor does there seem to be all that much enthusiasm among implementors. | Namespace support will probably be added as an extension to SAX and | the DOM interface; we'll have to discuss what this should look like. The trouble is that it will be very hard (if at all possible) to do this without doing damage to backwards compatibility. In other words, we should wait and see what happens with SAX and DOM and then follow up on it. I think we can go ahead and do 1.0 without namespaces. Other than that everything looked good to me. I'll take a look at the wstring module you mentioned. --Lars M. (who wishes he could have been there...) | https://mail.python.org/pipermail/xml-sig/1998-November/000476.html | CC-MAIN-2017-22 | refinedweb | 161 | 83.66 |
Introduction:
This blog deals with MNIST Data. Actually, MNIST is ‘Modified National Institute of Standards and Technology. This dataset consists of handwritten digits from 0 to 9 and it provides a pavement for testing image processing systems. This is considered to be the ‘hello world program in Machine Learning’ which involves Deep Learning.
Steps Involved are:
- Importing Dataset
- Split the Dataset into Test and Train
- Model Building
- Train the Model
- Predicting the Accuracy
1) Importing Dataset:
To proceed further with the code we need the dataset. So, we think about various sources like datasets, UCI, kaggle, etc. But since we are using Python with its vast inbuilt modules it has the MNIST Data in the keras.datasets module. So, we don’t need to externally download and store the data.
from keras.datsets import mnist data = mnist.load_data()
Therefore from keras.datasets module we import the mnist function which contains the dataset.
Then the data set is stored in the variable data using the mnist.load_data() function which loads the dataset into the variable data.
Next, let’s see the data type we find something unusual as it of the type tuple. We know that the mnist dataset contains handwritten digit images, stored in the form of tuples.
data type(data)
2) Split the Dataset into Train and Test:
We directly split the dataset into train and test. So for that, we initialize four variables X_train, y_train, X_test, y_test to sore the train and test data of dependent and independent values respectively.
(X_train, y_train), (X_test, y_test) = data X_train[0].shape X_train.shape
While printing the shape of each image we can find that it is 28×28 in size. Meaning the image has 28pixels x 28pixels.
Now, we have to reshape in such a way that we have we can access every pixel of the image. The reason to access every pixel is that only then we can apply deep learning ideas and can assign color code to every pixel. Then we store the reshaped array in X_train, X_test respectively.
X_train = X_train.reshape((X_train.shape[0], 28*28)).astype('float32') X_test = X_test.reshape((X_test.shape[0], 28*28)).astype('float32')
We know the RGB color code where different values produce various colors. It is also difficult to remember every color combination. So, refer to this link to get a brief idea about RGB Color Codes.
We already know that each pixel has its unique color code and also we know that it has a maximum value of 255. To perform Machine Learning, it is important to convert all the values from 0 to 255 for every pixel to a range of values from 0 to 1. The simplest way is to divide the value of every pixel by 255 to get the values in the range of 0 to 1.
X_train = X_train / 255 X_test = X_test / 255
Now we are done with splitting the data into test and train as well as making the data ready for further use. Therefore, we can now move to Step 3: Model Building.
3) Train the Model:
To perform Model building we have to import the required functions i.e. Sequential and Dense to execute Deep Learning which is available under the Keras library.
But this is not directly available for which we need to understand this simple line chart:
1) Keras -> Models -> Sequential
2) Keras -> Layers -> Dense
Let’s see the way we can import the functions with the same logic as a python code.
from keras.models import Sequential from keras.layers import Dense model = Sequential() model.add(Dense(32, input_dim = 28 * 28, activation= 'relu')) model.add(Dense(64, activation = 'relu')) model.add(Dense(10, activation = 'softmax'))
Then we store the function in the variable model as it makes it easier to access the function every time instead of typing the function every time, we can use the variable and call the function.
Then convert the image into a dense pool of layers and stack each layer one above the other and we use ‘relu’ as our activation function. The explanation of ‘relu’ is beyond the scope of this blog. To learn more about it you can refer to it.
Then again, we stack a few more layers with ‘softmax’ as our activation function. To learn more about ‘softmax’ function you can refer to this article as it is beyond this blog’s scope again as my primary aim is to get the highest possible accuracy with the MNIST Data Set.
Then finally we compile the entire model and use cross-entropy as our loss function, to optimize our model use adam as our optimizer and use accuracy as our metrics to evaluate our model.
To get an overview of our model we use ‘model.summary()’, which provides brief details about our model.
Now we can move to Step 4: Train the Model.
4) Train the Model:
This is the penultimate step where we are going to train the model with just a single line of code. So for that, we are using the .fit() function which takes the train set of the dependent and the independent and dependent variable as the input, and set epochs = 10, and set batch_size as 100.
Train set => X_train; y_train
Epochs => An epoch means training the neural network with all the training data for one cycle. An epoch is made up of one or more batches, where we use a part of the dataset to train the neural network. Meaning we send the model to train 10 times to get high accuracy. You could also change the number of epochs depending on how the model performs.
Batch_size => Batch size is a term used in machine learning and refers to the number of training examples utilized in one iteration. So basically, we send 100 images to train as a batch per iteration.
Let’s see the coding part of it.
Hence, after training the model we have achieved an accuracy of 97.88% for the training data set. Now, it’s time to see how the model works in the test set and see whether we have achieved the required accuracy. Therefore, we now move on to the ultimate step or Step 5: Predicting Accuracy.
5) Predicting Accuracy:
So to know how well the model works in the testing dataset I use the scores variable to store the value and use the .evaluate() function which takes the test set of the dependent and the independent variables as the input. This computes the loss and the accuracy of the model in the test set. As we are focused on accuracy we print only the accuracy.
Finally, we have achieved the result and we secured an accuracy of more than 96% in the test set which is very much appreciable, and the motive of the blog is achieved. I have scripted the link to the notebook for your(readers) reference.
Please feel free to connect with me through Linkedin as well. And thanks for reading the blog.
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| https://www.analyticsvidhya.com/blog/2021/06/mnist-dataset-prediction-using-keras/ | CC-MAIN-2021-25 | refinedweb | 1,197 | 72.46 |
New Ghostbusters Video Game in the Works 204.
Oh god (Score:2, Funny)
Re:Oh god (Score:5, Funny)
Re: (Score:2)
Re: (Score:2, Funny)
"Is this true?"
"Yes sir, it's true. This man has no dick."
Re: (Score:3, Funny)
who ya gonna call? (Score:5, Funny)
Scraping the bottom of the barrel. (Score:2, Insightful)
Re: (Score:2)
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Too bad movie-themed games almost always suck...I'd love to see a good Ghostbusters game, but I don't have much hope that it will be any fun to play.
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You had your choice of three ghostbusters and each had different abilities. Also, near the end you fought the marshmallow man.
Scraping bottom? (Score:4, Insightful)
it's based on an epic from 1300 years ago!
Talk about unoriginal!
I mean it's 1300 years old! who would want to see those characters in a different medium...
Has it been done before? (Score:2)
Ghostbusters II
A couple of games.
As from your example, there are LITERALLY CENTURIES of material available.
Yet we seem to keep getting rehashes of the same things. I'm not talking about the same plots. I'm talking movies that were already done.: (Score:2)
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Damn, that would make a great horror game.
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I hate to be one of those nit-picking jerks, but Odin hanged himself for nine days, as in:
I know that I hung on a high windy tree for nine long nights;
I had a spear wound -- that was my work -- I struck myself...
They brought me no bread, no horn to drink from...
Crying aloud, I seized the runes; finally I fell...
Thus I learned the secret lore, prospered and waxed in wisdom...
And I agree, a great many of the epic myths and sagas would make for awesome games.... but knowing the game companies, there'd be a
Beowulf... (Score:2, Offtopic)
And it'll probably be just as shitty a movie too.
Re: (Score:2)
I'm waiting for the sequel set in medieval times, as portrayed by The Brothers Grimm -- "Hansel und Grendel"
Re: (Score:2): (Score:2)
The Warriors videogame wasn't even written by the same people and it's a great game! If they can combine solid game programmers with the script they're gonna have for Ghostbusters, it should be an awesome game.
Now all we need is Sam Raimi to write the script for an Army of Darkness videogame, if they don't simply do the plot from the movie.
Re:Scraping the bottom of the barrel. (Score:5, Interesting).
Re: (Score:2)
Because a lot of the people making those movies were kids in the 80s, just like us. It's no coincidence, and it's not just cynical targeting of a given demographic. The people making them are making them because *they* think they're cool too.
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There was a surge in popularity for a Ghostbusters game when that demo video flew around the web about a year ago. Ghostbusters is not 'bottom of the barrel', and though the hurting for new material bit may be true, this is hardly proof of it.
Save this meme for when they announce the Filmation Ghostbusters game.
Re: (Score:2)
Or are you saying that games based on movies suck in general? If that's the case, then why does the age of the
Re: (Score:2)
One word: Transformers.
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There was already a script and lots of ideas. The material was there, and we were never going to get to see it. I hope the game finally lets us see what Sony denied us.
Re: (Score:3, Interesting)
Funny you should mention Lovecraft in connection with modern movies. Guilermo del Torro is directing "At the Mountains of Madness." I'm not sure if this is the Guillermo del Toro who directed Hellboy or the one that directed Pan's Labyrynth, but either way it's going to be a Lovecraft film with an actual budget. Also, at the other end of the scale the H P Lovercraft Historical Society produced a Call of Cthulhu [cthulhulives.org] film last year which is actually very entertaining (really!). They've also just released the tra
To heck with the game (Score:4, Insightful)
Given hollywood's abysmal track record in late-sequals though, I think perhaps it would be better off without any, regardless of whether it is a movie or game.
Re: (Score:3, Insightful)
Re: (Score:2)
Re: (Score:2)
Lines from it come up all the time in my circle of friends (sad? maybe)
"I had part of a slinky once... but I straightened it"
I might have to rewatch it soon actually...
Re: (Score:3, Funny)
Re: (Score:2)
Re:To heck with the game (Score:5, Insightful)
I think the second one had a "proper" script. Naturally, lightning didn't strike twice.
-Peter
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I've been saying for years that they should do another movie. Provided that they keep with the spirit (pun not intended) of the first two, modern special effects combined with a good script could make for a great movie.
Given hollywood's abysmal track record in late-sequals though, I think perhaps it would be better off without any, regardless of whether it is a movie or game.
As long as it has Bill Murray, Dan Aykroyd, and Harold Ramis it'll be a fun movie. Hell even if it's just bill murray.
Re: (Score:2)
In Soviet Russia (Score:5, Funny)
What do you mean big? (Score:5, Funny)
Re:What do you mean big? (Score:4, Funny)
Re: (Score:3, Funny)
Re: (Score:2)
Keeping fingers crossed (Score:4, Interesting)
Re: (Score:2)
Re: (Score:2)
Multiplayer? (Score:4, Funny)
I see an opportunity to coin a term here... when you're engaged in multiplayer, and your teammate crosses streams with you, resulting in both your deaths... we'll call that streamkilling. Or teamcrossing. I'm still working on it.
Re: (Score:2)
Because that's the only bad thing that ever happened when I "crossed streams" with my brothers growing up.
Re: (Score:2)
Soviet Rush.
Re: (Score:2, Funny)
#include <stdio.h>
int main() {
printf("Hello, world!\n");
return(0);
}
compiled with gcc 3.4:
-rwxrwxr-x 1 me users 6788 Nov 15 16:50 hello
almost 7k.
~
Re: (Score:2)
Re: (Score:3, Informative)
If setting it to "release" mode is all you rely on you'll be unhappy. You can enter project settings and set options such as align on 1-Byte boundaries instead of the default 16, REALLY remove debugging information (strangely, some still sticks around), set the linker to exclude the default libs, things like that. Look at the options, think about what they would do, and set it to the one you think is appropriate. When d
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You might have to dig around the Win32 API to get the "native" equivalent to printf (it'd probably be easier to just call one of the messagebox functions), but you can do it.
That library call would be
... printf.
Win32 is a small, solid API that's been mostly unchanged now for >10 years. There are 100 layers of crap built on top of it, but you don't have to use those.
Ya gotta trick Microsoft's compiler into doing what you want (as opposed to just passing parameters to gcc) but it can get done.
You can also just pass parameters to cl. You didn't think Microsoft built anything internally using projects and solutions, did you? (Well, maybe stuff in C#, but that's a different story).
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If they had enough game to give actual screenshots, they'd show more than one.
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Here's some spoiler cheat info for you (Score:5, Funny)
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Hilarious screenshot: (Score:4, Informative)
Interesting way to avoid the strike. (Score:5, Interesting)
Frankly, non-WGA people should do what they want. (Score:2)
If you're not a member of the WGA, they do not represent you and you therefore do not represent them.
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Will This Replace the Third Film? (Score:4, Interesting)
Who you gonna call? (Score:2)
Take the Marx Brothers movies, someone watching them for the first time today will find them boring because *everyone* has ripped off the Marx brothers to the point where they are not even funny anymore. Everyone knows every punchlin
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Ghostbusters Doom (Score:4, Interesting)
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Oblig Quotes (Score:3, Funny)
Yes, Its true this man has no Dick.
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Ghostbusters!? (Score:4, Funny)
Wii (Score:2, Insightful)
Okay, you win, you are the fanboy of the year (Score:4, Interesting).
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b) For the record, it's streams.
c) Regarding the hotel shootup: "I feel so funky."
There's somethin' strange... (Score:2)
But.... (Score:2)
Yes, have some. (Score:3, Funny)
Variety has a better article (Score:5, Informative)
Arcade game (Score:2)
As soon as I put this thing on my shoulder, I looked at what I was wearing: what looked like a long blaster with a hose extending behind me. Past that, there was one
Who's making it? (Score:2)
Don't mess with a classic (Score:3, Insightful)
Good theme music though.: (Score:2)
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Just a hint.
Re:Video games based on movies are not fun to play (Score:2)
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I loved that game as a kid. I remember how you could upgrade your car to add cool effects. You had to avoid the ghost at first then when you're driving. Then once you got the vacuum upgrade you could suck up the ghosts as you're driving by them.
I think Ghostbusters was the first BIG game on the C64. Yeah, there were a lot of successful titles, but when it came out almost everyone had to play it.
I think it set a lot of expectations early in video games that people would just buy stuff named for a film or a tv show. There were a lot of games that were utterly horrible and unplayable to follow.
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Re: (Score:2) | https://slashdot.org/story/07/11/15/2027224/new-ghostbusters-video-game-in-the-works | CC-MAIN-2017-34 | refinedweb | 1,769 | 82.04 |
Arduino Object Avoidance with PING and Hacked RC Car
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- by Elijah912
- Collected by 4 users
Finished Bot Here:
Before I begin I am a Senior Electrical Engineer student in college. This is a project im working on for my design class. I am very new to arduino and its language. Having said that here we go:
Working on an object avoiding vehicle using Arduino and Ping ultrasound sensor. I hacked an old rc car. Basically removed all the guts and replaced it with a breadboard and the arduino. I am still using the 9V rechargeable battery pack that came with the car to power the 2 motors through an L293D chip and a regular 9v battery to power the arduino. When I turn on the robot it runs well and responds while im holding it in the air so the code seems to be working. But then things go bad. Here are the issues i've come across so far.
After a while it begins to slow down and stop as you can see in the video. Battery is charged
When changing directions it badly stutters. will post another video soon showing this.
Not enough torque to run on carpet. Runs on tile but slows to a stop when changing directions.
When I grab one wheel to stop it while its running the other slows and eventually stops. Not too much of an issue there but just wondering why it happens since they are running independantly? gueesing it has to do with the overheating of the L293D.
I left the original two capacitors going across the motors attached, tried removing them and had same issue so I put them back. Also the L293D (can handle 0.6 amps) chip gets VERY hot while its running and starts to smell like its burning. I ordered a chip called ‘SN754410‘ from Texas Instruments. It can handle double the current of the L293D and has the same pin layout. It comes in next week so hopefully that will make a difference. Will update when it comes
I have the PING sensor mounted on a servo. After these issues are addressed I would like to add a section to the code to allow the servo to pan while its driving so it will avoid it from running into anything at any angle OR when it comes to an object look left and right and choose the best direction. I am horrible at code writing so any links to similar codes I can use or if anyone can help would be greatly appreciated.
Will post more pictures and videos as soon as I can.
Heres how I connected everything: PINS
1 to pin 9 on Arduino board, 2 to pin 3 on Arduino board, 3 to motor1 (either + or -) it wont matter as its DC, 4 to the gnd rail on the breadboard, 5 to the gnd rail on the breadboard, 6 to motor1, 7 to pin 4 Arduino, 8 to power (+) rail., 9 to pin 10 Arduino, 10 to pin 5 Arduino, 11 to motor2, 12 to GND rail, 13 to GND rail, 14 to motor2, 15 to pin 6 Arduino, 16 to power (+) rail
Heres the code I used. Credit to @lucky_larry on twitter for most of the code. I made a few changes to allow it to work for my PING sensor. The original was written for the SRF05 ultrasound sensor.
#include <Ping.h>
const int pingpin = 12; // ping pin (digital 12):
Serial.begin(9600);(pingpin, OUTPUT);
pinMode(pingpin, INPUT);
// create array loop to iterate over every item in the array
for (int thisReading = 0; thisReading < numOfReadings; thisReading++) {
readings[thisReading] = 0;
}
}
void loop() {
pinMode(pingpin, OUTPUT);
digitalWrite(pingpin, HIGH); // send 10 microsecond pulse
delayMicroseconds(10); // wait 10 microseconds before turning off
digitalWrite(pingpin, LOW); // stop sending the pulse
pinMode(pingpin, INPUT);
pulseTime = pulseIn(pingpin, <=);
}
}
Any comments, help, ideas or input is definately welcome. I also hope this can be used to help someone who is also having similar issues.
I was definately thinking
I was definately thinking that might be an issue once I got it working correctly. They're spinning real fast in the video. I'm not too familiar with PWM. About to do some research tho
Don't throw the original circuitry away !
I know this was said in the shoutbox, but to immortalize for future reference, "Don't throw away stuff". If you continue to do robotics in the future and you don't have a huge budget - go to Thrift Stores, Goodwill, or Second Hand Stores - and buy the RC toys. They are cheap because:
1. Someone got a better toy, lost interest, or someone else in the family got so irritated by the toy they threw it out.
2. (More commonly) - they lost the remote control for it.
Either way there is a cornucopia of good circuitry (made and tested as consumer products) out there. I usually pick up a $5 toy, look for the H-bridge (common/simple one is just using large NPN Transistors), power it up and test the connections. You can then solder wires to it and plug it into the micro-controller. If you use the toy intact, it's components are made for one-another, so you should not experience overheating & stalling problems... With the micro-controller you can start adding stuff to turn it into a mutant, sensors, servos, etc......
Maybe, I should do a tip/walkthrough sometime...
Good Luck !
If you decide to do a
If you decide to do a walkthrough Ill read it.. still new to all of this
Turning
When you get the motors running properly, you might try to adjust the center of gravity of the bot so that you could use the torque of the drive wheels to lift the front wheels before turning. It would definitely be an interesting video to watch if you could manage it. :)
When it runs on the ground
When it runs on the ground the front wheels shoot up in the air when it takes off before it slows down and dies.. thats a good idea to consider. thanks
Measure the current draw of
Measure the current draw of your motors. That'll let you confirm if you are trying to draw more power from the L293D motor driver, though if it got hot and smells like it is burning, I think you have your answer.
More importantly, this will tell you if the motors will work within the limits of the SN754410 driver you ordered. As an engineering student, you should understand that it is important to know the requirements and limitiations of your system components. Don't make the same mistake and burn out your new chip. Determine your typical and maximum current draw of your motors, and buy/build a motor driver to match.
Also, I have a question on your mechanical design. Are you intending to turn with a turning servo up front, like a regular RC car? Your code looks like you driving the to motors differentially to turn. If you are going to turn differentially, you will have trouble unless you match the angle of your front wheels to the relative turn radii of your rear wheels. If you don't, you will be trying to drag your front wheels sideways during the turn, and it will not work well at all.
I am currently looking into this issue on my Why Tri robot.
Yea I do need to measure the
Yea I do need to measure the currents the motors require. thinking the SN754410 which can handle 1.2 amp will still not be sufficient enough. I am planning on doing differential turning where one wheel goes forward and one goes backwards resulting in a turn. I think it would be powerful enough to drag the front wheels on turning. I pretty much have been building this robot on trial and error. I jus looked at your Why Tri robot. The front wheel you made using cardboard as a bracket seems like a great idea! Thanks
Try this. Forget the motor
Try this. Forget the motor drivers and the microprocessor. Wire up one of your rear wheels directly to the battery. Leave the other disconnected. This should result in a turn with the center on the non-moving wheel, right? Except you will likely find that the front wheels drag so badly that it won't turn well (or at all).
Now try hooking up that disconnected rear wheel directly to the battery, but in reverse. So it should spin on a center point between the two rear wheels, correct? Except it probably won't. It will be trying to drag the front wheels sideways, which will work terribly.
You could turn the front wheels to match the rotation, as I'm planning with Why Try. However, this is not a great solution. I'm only trying it for the fun of learning. Instead, replace both front wheels with a roller or caster, so that the front of the car does not offer significant resistance in any direction. Now you can use differential steering with little/no problem.
Yup.. Saw your video on
Yup.. Saw your video on steering. Might just replace the wheels with a roller if theres too much resistance. | http://letsmakerobots.com/node/25837?page=1 | CC-MAIN-2015-22 | refinedweb | 1,558 | 72.16 |
NLP Learning Series: Part 2 - Conventional Methods for Text Classification
This is the second post of the NLP Text classification series. To give you a recap, recently I started up with an NLP text classification competition on Kaggle called Quora Question insincerity challenge. And I thought to share the knowledge via a series of blog posts on text classification. The first post talked about the various preprocessing techniques that work with Deep learning models and increasing embeddings coverage. In this too: What Kagglers are using for Text Classification, which talks about various deep learning models in use in NLP and how to switch from Keras to Pytorch.
So again we start with the first step: Preprocessing.
Basic Preprocessing Techniques for text data(Continued)
So in the last post, we talked about various preprocessing methods for text for deep learning purpose. Most of the preprocessing for conventional methods remains the same. We will still remove special characters, punctuations, and contractions. But We also may want to do stemming/lemmatization when it comes to conventional methods. Let us talk about them.
For grammatical reasons, documents are going to use different forms of a word, such as organize, organizes, and organizing. Additionally, there are families of derivationally related words with similar meanings, such as democracy, democratic, and democratization.
Since we are going to create features for words in the feature creation step, it makes sense to reduce words to a common denominator so that ‘organize’,‘organizes’ and ‘organizing’ could be referred to by a single word ‘organize’
a) Stemming
Stemming is the process of converting words to their base forms using crude Heuristic rules. For example, one rule could be to remove ’s’ from the end of any word, so that ‘cats’ becomes ‘cat’. or another rule could be to replace ‘ies’ with ‘i’ so that ‘ponies becomes ‘poni’. One of the main point to note here is that when we stem the word we might get a nonsense word like ‘poni’. But it will still work for our use case as we count the number of occurrences of a particular word and not focus on the meanings of these words in conventional methods. It doesn’t work with deep learning for precisely the same reason.
We can do this pretty simply by using this function in python.
from nltk.stem import SnowballStemmer from nltk.tokenize.toktok import ToktokTokenizer def stem_text(text): tokenizer = ToktokTokenizer() stemmer = SnowballStemmer('english') tokens = tokenizer.tokenize(text) tokens = [token.strip() for token in tokens] tokens = [stemmer.stem(token) for token in tokens] return ' '.join(tokens)
b) Lemmatization
Lemmatization is very similar to stemming but it aims to remove endings only if the base form is present in a dictionary.
from nltk.stem import WordNetLemmatizer from nltk.tokenize.toktok import ToktokTokenizer def lemma_text(text): tokenizer = ToktokTokenizer() tokens = tokenizer.tokenize(text) tokens = [token.strip() for token in tokens] tokens = [wordnet_lemmatizer.lemmatize(token) for token in tokens] return ' '.join(tokens)
Once we are done with processing a text, our text will necessarily go through these following steps.
def clean_sentence(x): x = x.lower() x = clean_text(x) x = clean_numbers(x) x = replace_typical_misspell(x) x = remove_stopwords(x) x = replace_contractions(x) x = lemma_text(x) x = x.replace("'","") return x
Text Representation
In Conventional Machine learning methods, we ought to create features for a text. There are a lot of representations that are present to achieve this. Let us talk about them one by one.
a) Bag of Words - Countvectorizer Features
Suppose we have a series of sentences(documents)
X = [ 'This is good', 'This is bad', 'This is awesome' ]
Bag of words will create a dictionary of the most common words in all the sentences. For the example above the dictionary would look like:
word_index {'this':0,'is':1,'good':2,'bad':3,'awesome':4}
And then encode the sentences using the above dict.
This is good - [1,1,1,0,0] This is bad - [1,1,0,1,0] This is awesome - [1,1,0,0,1]
We could do this pretty simply in Python by using the CountVectorizer class from Python. Don’t worry much about the heavy name, it just does what I explained above..
cnt_vectorizer = CountVectorizer(dtype=np.float32, strip_accents='unicode', analyzer='word',token_pattern=r'\w{1,}', ngram_range=(1, 3),min_df=3) # we fit count vectorizer to get ngrams from both train and test data. cnt_vectorizer.fit(list(train_df.cleaned_text.values) + list(test_df.cleaned_text.values)) xtrain_cntv = cnt_vectorizer.transform(train_df.cleaned_text.values) xtest_cntv = cnt_vectorizer.transform(test_df.cleaned_text.values)
We could then use these features with any machine learning classification model like Logistic Regression, Naive Bayes, SVM or LightGBM as we would like. For example:
# Fitting a simple Logistic Regression on CV Feats clf = LogisticRegression(C=1.0) clf.fit(xtrain_cntv,y_train)
Here is a link to a kernel where I tried these features on the Quora Dataset. If you like it please don’t forget to upvote.
b) TFIDF Features
TFIDF is a simple technique to find features from sentences. While in Count features we take count of all the words/ngrams present in a document, with TFIDF we take features only for the significant words. How do we do that? If you think of a document in a corpus, we will consider two things about any word in that document:
- Term Frequency: How important is the word in the document?
$$TF(word\ in\ a\ document) = \dfrac{No\ of\ occurances\ of\ that\ word\ in\ document}{No\ of\ words\ in\ document}$$
- Inverse Document Frequency: How important the term is in the whole corpus?
$$IDF(word\ in\ a\ corpus) = -log(ratio\ of\ documents\ that\ include\ the\ word)$$
TFIDF then is just multiplication of these two scores.
Intuitively, One can understand that a word is important if it occurs many times in a document. But that creates a problem. Words like “a”, “the” occur many times in sentence. Their TF score will always be high. We solve that by using Inverse Document frequency, which is high if the word is rare, and low if the word is common across the corpus.
In essence, we want to find important words in a document which are also not very common.
We could do this pretty simply in Python by using the TFIDFVectorizer class from Python..
# Always start with these features. They work (almost) everytime!') # Fitting TF-IDF to both training and test sets (semi-supervised learning) tfv.fit(list(train_df.cleaned_text.values) + list(test_df.cleaned_text.values)) xtrain_tfv = tfv.transform(train_df.cleaned_text.values) xvalid_tfv = tfv.transform(test_df.cleaned_text.values)
Again, we could use these features with any machine learning classification model like Logistic Regression, Naive Bayes, SVM or LightGBM as we would like. Here is a link to a kernel where I tried these features on the Quora Dataset. If you like it please don’t forget to upvote.
c) Hashing Features
Normally there will be a lot of ngrams in a document corpus. The number of features that our TFIDFVectorizer generated was in excess of 2,00,000 features. This might lead to a problem on very large datasets as we have to hold a very large vocabulary dictionary in memory. One way to counter this is to use the Hash Trick.
One can think of hashing as a single function which maps any ngram to a number range for example between 0 to 1024. Now we don’t have to store our ngrams in a dictionary. We can just use the function to get the index of any word, rather than getting the index from a dictionary.
Since there can be more than 1024 ngrams, different ngrams might map to the same number, and this is called collision. The larger the range we provide our Hashing function, the less is the chance of collisions.
We could do this pretty simply in Python by using the HashingVectorizer class from Python. It has a lot of parameters most significant of which are:
- ngram_range: I specify in the code (1,3). This means that unigrams, bigrams, and trigrams will be taken into account while creating features.
- n_features: No of features you want to consider. The range I gave above.
# Always start with these features. They work (almost) everytime! hv = HashingVectorizer(dtype=np.float32, strip_accents='unicode', analyzer='word', ngram_range=(1, 4),n_features=2**12,non_negative=True) # Fitting Hash Vectorizer to both training and test sets (semi-supervised learning) hv.fit(list(train_df.cleaned_text.values) + list(test_df.cleaned_text.values)) xtrain_hv = hv.transform(train_df.cleaned_text.values) xvalid_hv = hv.transform(test_df.cleaned_text.values) y_train = train_df.target.values
Here is a link to a kernel where I tried these features on the Quora Dataset. If you like it please don’t forget to upvote.
d) Word2vec Features
We already talked a little about word2vec in the previous post. We can use the word to vec features to create sentence level feats also. We want to create a
d dimensional vector for sentence. For doing this, we will simply average the word embedding of all the words in a sentence.
We can do this in Python using the following functions.
# load the GloVe vectors in a dictionary: embeddings_index = load_glove_index() print('Found %s word vectors.' % len(embeddings_index)) from nltk.corpus import stopwords stop_words = stopwords.words('english') def sent2vec(s): words = str(s).lower() words = word_tokenize(words) words = [w for w in words if not w in stop_words] words = [w for w in words if w.isalpha()] M = [] for w in words: try: M.append(embeddings_index[w]) except: continue M = np.array(M) v = M.sum(axis=0) if type(v) != np.ndarray: return np.zeros(300) return v / np.sqrt((v ** 2).sum()) # create glove features xtrain_glove = np.array([sent2vec(x) for x in tqdm(train_df.cleaned_text.values)]) xtest_glove = np.array([sent2vec(x) for x in tqdm(test_df.cleaned_text.values)])
Here is a link to a kernel where I tried these features on the Quora Dataset. If you like it please don’t forget to upvote.
Results
Here are the results of different approaches on the Kaggle Dataset. I ran a 5 fold Stratified CV.
Here is the code. If you like it please don’t forget to upvote. Also note that I didn’t work on tuning the models, so these results are only cursory. You can try to squeeze more performance by performing hyperparams tuning using hyperopt or just old fashioned Grid-search and the performance of models may change after that substantially.
Conclusion
While Deep Learning works a lot better for NLP classification task, it still makes sense to have an understanding of how these problems were solved in the past, so that we can appreciate the nature of the problem. I have tried to provide a perspective on the conventional methods and one should experiment with them too to create baselines before moving to Deep Learning methods. If you want to learn more about NLP here is an awesome course. You can start for free with the 7-day Free Trial. If you think I. | https://mlwhiz.com/blog/2019/02/08/deeplearning_nlp_conventional_methods/ | CC-MAIN-2020-40 | refinedweb | 1,822 | 58.18 |
I'm working on regular expressions homework where one question is:
Using language reference manuals online determine the regular expressions for integer numeric constants and identifiers for Java, Python, Perl, and C.
Integer constants in Perl can be
^0x
^0b
0
Following that leader is any number of valid digits in that base and also optional underscores.
Note that digit does not mean
\p{POSIX_Digit}; it means
\p{Decimal_Number}, which is really quite different, you know.
Please note that any leading minus sign is not part of the integer constant, which is easily proven by:
$ perl -MO=Concise,-exec -le '$x = -3**$y' 1 <0> enter 2 <;> nextstate(main 1 -e:1) v:{ 3 <$> const(IV 3) s 4 <$> gvsv(*y) s 5 <2> pow[t1] sK/2 6 <1> negate[t2] sK/1 7 <$> gvsv(*x) s 8 <2> sassign vKS/2 9 <@> leave[1 ref] vKP/REFC -e syntax OK
See the 3
const, and much later on the
negate op-code? That tells you a bunch, including a curiosity of precedence.
Identifiers specified via symbolic dereferencing have absolutely no restriction whatsoever on their names.
100->(200)calls the function named
100with the arugments
(100, 200).
${"What’s up, doc?"}refers to the scalar package variable by that name in the current package.
${"What's up, doc?"}refers to the scalar package variable whose name is
${"s up, doc?"}and which is not in the current package, but rather in the
Whatpackage. Well, unless the current package is the
Whatpackage, of course. Similary
$Who'sis the
$svariable in the
Whopackage.
One can also have identifiers of the form
${^identifier
}; these are not considered symbolic dereferences into the symbol table.
Identifiers with a single character alone can be a punctuation character, include
$$ or
%!.
Identifers can also be of the form
$^C, which is either a control character or a circumflex folllowed by a non-control character.
If none of those things is true, a (non–fully qualified) identifier follows the Unicode rules related to characters with the properties
ID_Start followed by those with the property
ID_Continue. However, it overrules this in allowing all-digit identifiers and identifiers that start with (and perhaps have nothing else beyond) an underscore. You can generally pretend (but it’s really only pretending) that that is like saying
\w+, where
\w is as described in Annex C of UTS#18. That is, anything that has any of these:
[0-9]
So either
^\d+$ or else
^[\p{Alphabetic}\p{Decimal_Number}\p{Mark}\p{Connector_Punctuation}]+$
ought to do it for the really simple ones if you don’t care to explore the intricacies of the Unicode ID_Start and ID_Continue properties. That’s how it’s really done, but I bet your instructor doesn’t know that. Perhaps one shan’t tell him, eh?
But you should cover the nonsimple ones I describe earlier.
And we haven’t talked about packages yet.
Beyond those simple rules, you must also consider that identifiers may be qualified with a package name, and package names themselves follow the rules of identifiers.
The package separator is either
:: or
' at your whim.
You do not have to specify a package if it is the first component in a fully qualified identifier, in which case it means the package
main. That means things like
$::foo and
$'foo are equivalent to
$main::foo, and
isn't_it() is equivalent to
isn::t_it(). (Typo removed)
Finally, as a special case, a trailing double-colon (but not a single-quote) at the end of a hash is permitted, and this then refers to the symbol table of that name.
Thus
%main:: is the
main symbol table, and because you can omit main, so too is
%::.
Meanwhile
%foo:: is the
foo symbol table, as is
%main::foo:: and also
%::foo:: just for perversity’s sake.
It’s nice to see instructors giving people non-trivial assignments. The question is whether the instructor realized it was non-trivial. Probably not.
And it’s hardly just Perl, either. Regarding the Java identifiers, did you figure out yet that the textbooks lie? Here’s the demo:
$ perl -le 'print qq(public class escape { public static void main(String argv[]) { String var_\033 = "i am escape: ^\033"; System.out.println(var_\033); }})' > escape.java $ javac escape.java $ java escape | cat -v i am escape: ^[
Yes, it’s true. It is also true for many other code points, especially if you use
-encoding UTF-8 on the compile line. Your job is to find the pattern that describes these startlingly unforbidden Java identifiers. Hint: make sure to include code point U+0000.
There, aren’t you glad you asked? Hope this helps. Or something. ☺ | https://codedump.io/share/ESvhtYnEEBL0/1/what-characters-are-allowed-in-perl-identifiers | CC-MAIN-2018-05 | refinedweb | 781 | 63.59 |
In this post we will use the Python libraries requests and lxml to scrape reviews from an amazon product page.
This data can be used to create datasets for sentiment analysis or other educational or research purposes. If you sell products on Amazon it can even be useful to analyse the reviews to understand what customers like and dislike about your product.
We will scrape the following review information:
- author
- title
- star rating
- how many people found this review helpful
- publishing date
Rather than scraping the reviews from many products I decided to look at one product with a loooooot of reviews which happens to be the Echo Dot (2nd Generation). It counts more than 60.000 reviews!
THINGS TO CONSIDER IN ADVANCE
There are a lot of different ways how to scrape content from the internet. In this blog post we present a very basic approach which works for our purpose since the amount of data is fairly small and the data format is well formed. If you have a less well formed data format you can consider using BeautifulSoup which is more forgiving but also slower. If you have a more complex task and need to scrape a lot of content you should consider using scrapy.
Things like storing content in a database instead of keeping it the memory, avoiding being blocked by using proxies and using multi-threading to overcome performance bottlenecks become relevant with increasing amounts of data you want to scrape.
SCRAPING THE REVIEWS
Amazon makes it relatively easy to scrape product reviews. You can find all reviews for Echo Dot here.
Using this URL we will get the most recent reviews first and then we just modify the pageNumber parameter in the url to go from one page to the next.
Before requesting the data from Amazon go to this page and get your browser's' user agent string to avoid being blocked by Amazon.
Now we can get the content of the first review page:
from lxml import html import requests <p> </p> amazon_url = '' <br> user_agent = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.94 Safari/537.36' <br> headers = {'User-Agent': user_agent} page = requests.get(amazon_url, headers = headers) parser = html.fromstring(page.content)
Next we have to find the nodes of the reviews to extract them from the page. For that you open the review page in your Chrome browser, right-click on a review and select inspect:
Passing the XPATH to the parser will return the list with the reviews on that page:
xpath_reviews = '//div[@data-hook="review"]' reviews = parser.xpath(xpath_reviews)
Do the same with the elements of a review to get the XPATHs of the author, title and so on.
xpath_rating = './/i[@data-hook="review-star-rating"]//text()' xpath_title = './/a[@data-hook="review-title"]//text()' xpath_author = './/a[@data-hook="review-author"]//text()' xpath_date = './/span[@data-hook="review-date"]//text()' xpath_body = './/span[@data-hook="review-body"]//text()' xpath_helpful = './/span[@data-hook="helpful-vote-statement"]//text()'
Now we can loop over the reviews and extract the information from each review into a dictionary and append it to a dataframe:
for review in reviews: rating = review.xpath(xpath_rating) title = review.xpath(xpath_title) author = review.xpath(xpath_author) date = review.xpath(xpath_date) body = review.xpath(xpath_body) helpful = review.xpath(xpath_helpful) review_dict = {'rating': rating, 'title': title, 'author': author, 'date': date, 'body': body, 'helpful': helpful} reviews_df = reviews_df.append(review_dict, ignore_index=True)
After that we modify the URL and scrape the next page.
Now we have to do some data cleaning in order to convert the star ratings to integers and the publishing date to datetime format. After that we can start exploring the data.
DATA EXPLORATION
Let's look at some histograms first. The plot of the star ratings should be the same as on the Amazon page if the scraping went as expected:
Now the length of the reviews:
As expected most of the reviews a very short. Amazom.com does not have a restriction for a minimum length of a review. The longest review is longer than 18K characters which is way longer than this blog post.
The picture becomes clearer if we look at the logarithm of the length:
The most frequent length (the mode of the histogram) is 7. This is because there is a huge number of reviews which are simply "love it" and "awesome"
The 2nd generation of Echo Dot was released in October 2016. The histograms of review dates confirms that we scraped even the oldest reviews:
I'm not quite sure about the spikes in July 2017. Maybe they are related to the huge success of the Amazon Prime Day and the fact that Echo Dot was the most popular Product during the Prime Day.
Let's now look at the correlation between the length of the review and the number of people who found it helpful. Since both of these variables have a very long tail we calculate the logarithm from them.
The results look as expected, longer reviews are found more helpful than short ones.
Next we can a look at word clouds generated from the reviews. We split the reviews in 2 categories: Rating "1, 2, or 3 stars" and "4 or 5 stars". To count the word co-occurrences in the reviews we can use the CountVectorizer from the sklearn library and a simple word cloud generator.
Single word counts
We cannot learn much just from looking at the word frequencies since "like" in the bad reviews can also come from "don't like". Instead we can look at the co-occurrences of bigrams and trigrams, which can also be generated by the CountVectorizer.
Bigrams
Trigrams
Now the pictures become more clear - apparently a lot of customers complain about poor sound quality, wifi connectivity and customer service. The positive reviews contain a lot of generic phrases such as "best thing ever" and "works great". Also among popular bi- and trigrams are "bought prime day" and "prime day" which may support the hypothesis that the spikes in the histogram of reviews per day are related to the Prime Day.
I hope this was helpful - now try it out yourself on some other product and post your findings in the comments! :-) | https://www.basecamp.ai/blog/tutorial-behavioral-analysis | CC-MAIN-2018-26 | refinedweb | 1,046 | 61.06 |
between administrative intricacies this week, among other things, I took the time to reproduce both in Clojure and Scala a small exercise found in Real World Haskell (RWH).
This blog entry will be very small as I simply provided in each language a way to implement the algorithm.
The algorithm is the Adler32 checksum algorithm as presented in RWH. (You will be able to see the link at the end the protest on the Wikipedia site). Trying to decode the three code samples while the Wikipedia link is blacked out for protest, can be also seen as an interesting exercise :).
The Adler32 algorithm is an algorithm invented by Mark Adler in 1995 and used in the zlib compression library. I see these katas as an interesting mean of learning new things on a daily base (isn't it our job to learn and understand better than use blindly external frameworks?).
For copyright purpose I provide here my version of the algorithm and not the one in the book, as I tried to produce my own haskell version
import Data.Char (ord)import Data.Bits (shiftL, (.&.), (.|.)) base = 65521 cumulate::(Int, Int) -> Char -> (Int, Int) cumulate (a, b) x = let a' = (a + (ord x .&. 0xff)) `mod` base b' = (a'+ b) `mod` base in (a', b') adler32::[Char] -> Int adler32 xs = let (a, b) = foldl cumulate (1, 0) xs in (b `shiftL` 16) .|. a
The authors use this algorithm on purpose in order to present an application of the use of the higher order fold function. Let give it a try:
ghci>adler32 "Thumper is a cute rabbit" 1839204552 ghci>
That gives us meat for our tests in Scala and Clojure (I have not learn yet about quickCheck Haskell) Logically, in Clojure our test should look like:
(ns algorithms.test.adler32-spec (:use algorithms.adler32) (:use clojure.test)) (deftest checksum-with-favourit-sentence-should-produce-result (is (= 1839204552 (checksum "Thumper is a cute rabbit"))))
that runs green for the following implementation:
(ns algorithms.adler32) )))
where I naively used a derive routine in order to dispatch my multimethod using the class function as a dispatcher. My dispatching mechanism resolves now the clojure.lang.LazySeq instances as children of ::collection :
algorithms.adler32=> (parents clojure.lang.LazySeq) #{java.util.List clojure.lang.Obj clojure.lang.ISeq clojure.lang.IPending clojure.lang.Sequential :algorithms.adler32/collection} algorithms.adler32=>
Test ok.
Following the same reasoning in Scala, the test will be :
package com.promindis.algorithms.cheksum import org.specs2.Specification class Adler32Specification extends Specification { def is = "Adler32Specification" ^ p^ "checksum for input" ^ "Should restore the expected checksum value" !e1 def e1 = new DefaultAdler32() .checksumText("Thumper is a cute rabbit".toCharArray) .should(beEqualTo(1839204552)) }
leading to
Tests green :)Tests green :)package com.promindis.algorithms.cheksum trait Adler32 { val base = 65521 def rebased(value: Int) = value % base def cumulated(acc: (Int, Int), item : Byte): (Int, Int) = { val a = rebased(acc._1 + (item & 0xff )) (a, (a + acc._2) % base) } def checksum(data: Traversable[Byte]): Int def checksumText(data: Traversable[Char]): Int } final class DefaultAdler32 extends Adler32 { override def checksum(data: Traversable[Byte]): Int = { val result = data.foldLeft((1, 0)) {cumulated(_, _)} (result._2 << 16) | result._1 } def checksumText(data: Traversable[Char]) = { checksum(data.toSeq.map(_.toByte)) } }
That's all folks (I promised it would not be long). And don't take for granted what comes from closed boxes !
Be seeing you !!! :)
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ios app development in hyderabad | http://patterngazer.blogspot.com/2012/01/naive-adler32-example-in-clojure-and.html | CC-MAIN-2019-09 | refinedweb | 666 | 57.87 |
ObjectSharp Blog
SmartNavigation can be set to true on your ASP.NET webform so that when postbacks occur , the page when rendered back to the browser, will navigate back to the control that caused the postback.
But SmartNavigation can be problematic especially when dynamically loading controls onto your webform.
Therefore if you have SmartNavigation turned off = false, below is a piece of code that you can call from your webform that will add javascript to your page, to automatically navigate back to the control that originally caused the postback.
I tested the code against IE6 and Netscape 7.1.
/// /// This method will take passed webPage, and find the control that caused the postback. If it finds /// one it will set javascript on the page to set focus to that control /// /// The web page public void SetFocusPostBackControl(System.Web.UI.Page webPage) { string[] ctlPostBack; ctlPostBack = webPage.Page.Request.Form.GetValues("__EVENTTARGET"); if (ctlPostBack != null && ctlPostBack.Length > 0) { string ctlUniqueId; ctlUniqueId = ctlPostBack[0]; System.Web.UI.Control findControl = webPage.Page.FindControl(ctlUniqueId); if ((findControl != null) && (findControl is DropDownList || findControl is TextBox || findControl is RadioButton || findControl is RadioButtonList)) { string ctlClientId; ctlClientId = findControl.ClientID; string jScript; document.getElementById('" + ctlClientId + "').focus(); document.getElementById('" + ctlClientId + "').scrollIntoView(true) </SCRIPT>";; webPage.Page.RegisterStartupScript("focus",jScript );
} } }
A couple of months ago, I had to quickly develop an ASP.NET framework.I incorporated parts of a Windows .NET framework that I had previously worked on. The basicpremise being that a Windows .NET Form and an ASP.NET WebForm are both event driven and have controls such as buttons and dropdowns.
There were two basic steps in developing this ASP.NET framework.
1) Creating Ancestor code behind pages for all the code behind pages used in the project:
a) public class WebFormBase : System.Web.UI.Page -> For the Web Formsb) public class WebUserControlBase : System.Web.UI.UserControl -> For the Web User Controls When a Webform or Web UserControl needs to be created, their code behinds inherit from the custom base class:
public class OrderWebForm : WebFormBasepublic class ProductWebuserControl : WebUserControlBase
I think the above is a pretty standard thing to do.
The only thing I really did a little bit differently was to raise more events up to the descendent pages such as:
InitIniting
PreRenderingPreRender
etc.
In this way the descendent code has a chance to do some work before and after the code in ancestor.
2) All server side controls used on a WebForm or Web UserControl are inherited from the standard Microsoft Web Controls, or a third party control:
public class MyWebButton : System.Web.UI.WebControls.Buttonpublic class MyWebMenu : Infragistics.Web.UI.UltraWebMenuetc. etc. As you know there are many more. Hyperlink, Label, DataList etc.
For this framework thats pretty well it, in a nutshell.
This has really paid off for the future development work, because server Side controls can now implement custom interfaces, such as :ITranslationIDisable
Then in the base classes for the code behind for the WebFormBase or the WebUserControlBase, all the code is there to handle translation of pages to French or English or to disable or enable or disable controls automatically depending on a custom property put on the Web page called Enabled. Other things that have been built into the framework are resource file management, session management, navigation management and a custom help button that launches another browser with some help.
I'm working on a smart client application at the moment. One of the forms, under certain conditions, launches a wizard to gather information from the user.
From the users perspective they open the form and the wizard displays. If the user hits cancel, I want the wizard to close and the form not to show.
So what is the best way to do this. There is no cancel in the FormLoad event. If you try to close in formload an exception is raised:
Cannot call Close() while doing CreateHandle().
I asked Google and found one solution. Controls have a Public Event, VisibleChanged that fires when the visible property is changed. In this event you can call the forms Close method.
This works fine with one side effect, the form shows for a split second then closes.
This will suffice, but if anyone knows a better way to do this please let me know.. :)
NUNit Testing Practices
Chicken and Egg, TDD, Class Modeling, DevDrivenTesting, ModelDrivenTesting-Create A Test First, and use it to code gen the class you want to implement.-Create A Class First, and use it to code gen a stubbed test.-Model a Class, Capture Meta Data about the way it's supposed to work, and then generate both the class and unit tests
When testing persistence, I often write an NUnit test that programmatically creates a new entity, jams some data into (hard coded into my test) then calls a data access layer to persist it, then I create a new entity and ask my DAL to load it from the database (the same identifier I used to create it). Then I just compare the entities.
A developer I work with today showed me what he does. He creates an XML file with some test data and has a generic utitlity class to persist that into the database. He then creates a new entity
Can't afford the high costs of COM+ performance overhead in the distributed transaction co-ordinator, but still want somewhat automatic transactions? Same connection? Same Transactions, but different Dac's?
DacBase dacs = new DacBase[3];
dacs[0] = new OrderDac();dacs[1] = new CustomerDac();dacs[2] = new EmployeeDac();
trans = DbHelper.BeginTrans();for i = 1 to dacs.length{ dacs[].update(trans)}
trans.Commit();
OrderDac.Update(entity, trans)CustomerDac.Update(entity, trans)
So what does it mean to design an autonomous service. Based on my previous post, there are two possible issues to consider. First, the service needs to have a life outside of the client making the request. Second, the service needs to be self-healing in that any dependence on the actual endpoint of services that are used must be mitigated. To put this second point into an example, if Service A invokes Service B, then Service A must be capable of discovering Service B should Service B move. Service A should not be dependent on any manually updated configuration information to use Service B. Unfortunately, neither of these two considerations really help to determine what the boundaries of an autonomous service should be.
To get a grasp on the criteria that we use for bounding a service, consider the following hierarchy.
Figure 1 - Service Hierarchy
The process service is a high-level interface where a single service method call invokes a series of smaller steps. These smaller steps could be either another process or a call to a business entity service. Eventually, at the bottom of each of the paths, there will be one or more business entity services. These business entities don't contain any data, but instead interact with a data source through a data representation layer. Each of the blocks in the hierarchy above the level of the data source *can* be a service. Whether they are or not is one of the questions to be answered.
Follow the data
The definition I have found most useful for identifying the boundary for a service is one across which data is passed. If there is no data moving between the caller and the callee, there is little need for a service-based implementation. Consider a service that provides nothing but functionality with no data. One that, for example, takes a single number and returns an array of the prime factors. While such a service could definitely be created, the rationale for implementing it as a service is thin. After all, the same functionality could be embedded into an assembly and deployed with an application. Worried about being able to update it regulary? Place it onto a web server and use zero-touch deployment to allow for dynamic updating. So when trying to define the services, follow the data.
Given that little nugget of wisdom, take another look at the hierarchy in Figure 1. For someone to call a process service, some data must be provided. In particular, it needs to be passed sufficient information for the process to 'do its thing'. Want to invoke the “CreateOrder” process service? Give the service enough information to be able to create the order. This means both customer and product details. When defining the business services involved in the process (the next level in the hierarchy), the same type of examination needs to be made. Look at the places in the process where data is passed. These data transfer points are the starting point for boundary definition.
Keep it Chunky
The other criteria I use for defining service boundaries is based on the relatively nebulous concept of 'chunkiness'. The basic premise goes back to the first tenet of services. That is, calls into a service may be expensive. This is not surprising given that the movement of data across process or system boundaries is usually part of the process. As a result of the potential delay, the calling applications performance is improved by keeping the number of service calls to a minimum. This runs counter to the 'normal' coding style of setting properties and invoking methods on local objects.
Once the data flow has been identified (the object sequence diagram is actually quite useful in this regard), look at the interactions between two classes. If there is a series of call/response patterns that is visible, that interaction is ripe for coalescing into a single service call.
The downside of this approach is potentially providing more information that would normally be needed. Say that the normal call/response pattern goes something like the following:
Order o = new Order(customerId);OrderLine ol;ol = o.OrderLines.Add(productId1, quantity1);ol.ShipByDate = DateTime.Now.AddDays(2);ol = o.OrderLines.Add(productId2, quantity2);
In order to support the creation of order lines both with and without a custom shipby date, the parameter list for any service would have to change. But there is a solution. One of the strengths of XML is its flexibility in this regard. The acceptible schema can be different. These differences can then be identified programmatically and the results changed as needed. For this reason, we usually pass XML documents as the parameter for service calls.
The result of this is a sense of where the boundaries of a service should be. First, look at the data passed between objects. Identify any series of calls between two objects. Then group the data passed through these calls into a single service using an XML document as the parameter.
Will this logic work for every possible case? Maybe not. But more often than you think, this kind of design breakdown will result a decent set of boundary definitions for the required services. The one drawback frequently identified by people is that this approach does not directly consider where the data is stored. While this is true, it is not that imperative. Accessing a data source can either be done through a separate service (identified by this analysis process) or through local objects. In other words, the segragation of data along business or process service boundaries is not necessarily a given. Nor, as it turns out, is it even a requirement. | https://blogs.objectsharp.com/cs/blogs/deb/?page=174 | CC-MAIN-2020-40 | refinedweb | 1,889 | 55.64 |
The 5 Layers of a Design System
Picture a fully-fledged design system. You can bootstrap a new project, pull a bunch of components from the system, and have a page in minutes instead of days.
When you’re first starting to build your own, it seems too good to be true. You might be asking yourself, “how do I get from nothing to a system that supports multiple teams and hundreds of happy engineers?”
There’s a lot to consider, but in this post we’re going to talk about design system architecture, and specifically the concept of component hierarchies.
We can use the metaphor of a wedding cake to understand this a little better. When you see a wedding cake, your brain first thinks, “oh look, a cake.” As you look closer, you start to see that it consists multiple layers and elements.
Design systems are the same way. At first glance, a design system might seem like a single, monolithic library. In reality, a good design system is a series of layers that build on each other, ideally using progressive disclosure of complexity as a guiding principle.
The 5 layers
When a design system reaches maturity, it should have five layers, with the first three living in the design files and component library, and the last two living in the application code.
You may have heard of Brad Frost’s Atomic Design. He refers to the 5 levels in the component hierarchy in the following way:
- Atoms (in the design system)
- Molecules (in the design system)
- Organisms (in the design system)
- Templates (in the application code)
- Pages (in the application code)
Brad Frost’s language is really good, and very commonly used across teams. It’s not quite as specific as I’d like to really nail down the communication between designers and developers on my team, so I’ve decided to adopt Radius’ language and diagram:
- Design tokens (in the design system)
- Elements (in the design system)
- Patterns (in the design system)
- Features (in the application code)
- Layouts (in the application code)
Design Tokens
Design tokens are the most abstract layer of the system. They are an approach to storing style attributes like color, typography, and spacing in a pre-determined structure. While not particularly useful on their own, they are a critical part of a design system. They allow designers and developers to quickly ship redesigns, add theming to their applications, and build consistent layouts.
Ideally, your design tokens will follow a specific structure so that when you want to add a new theme — like dark mode — or you want other sites to be able to apply their own theme, it’s easy to do. You should agree with your designers on how to name and structure your tokens so that you can start to build a shared language between designers and developers on your team.
You might represent your design tokens in your application like this:
const theme = {
colors: {
primary1: "#07005B",
primary2: "#1D35AF",
secondary1: "#E34F30",
secondary2: "#3CA6E0",
secondary3: "#C17259",
secondary4: "#0E78B2",
secondary5: "#00875E",
},
};
Elements
Now that we’ve covered design tokens, let’s move up a level to elements. In my experience, this is what people usually think about when they imagine a design system. They’re certainly a foundational part!
The elements in the design system should know how to read your design tokens. As you’re building out your elements, you’ll want to think carefully about what parts of your elements can be overridden by a change to the design tokens, and which are hardcoded.
The most common example of an element is a Button component. It seems simple, but there’s a lot to consider!
Let’s use a
RadioButton for our example. If we’re writing React code, our
RadioButton might look something like this (although in real life it’ll have some props):
<RadioButton />
Some other examples include:
- Link
- Tab
- Checkbox
- Input
- Grid
- Box
Patterns
Patterns consist of two or more elements. They are more opinionated than elements. As design system maintainers, we make decisions about how elements are combined to create patterns. If consumers don’t like they way we have created a pattern, they are welcome to drop down a layer of abstraction and combine elements in a new way.
Let’s use the
RadioList to illustrate this point. A
RadioList is a group of multiple
RadioButton elements. I’d implement that component like this:
const radioList = [
{
label: 'Specialized Diverge',
value: 'diverge'
},
{
label: 'Specialized Roubaix',
value: 'roubaix'
},
{
label: 'Specialized Allex',
value: 'allez'
}
]<RadioList data={radioList}/>
Under the hood, the
RadioList would render three
RadioButtons with the correct labels and values.
Some other examples include:
- TabsList
- Form
- NavBar
Features
Features consist of two or more patterns. They are more opinionated and specific than patterns. As usual, consumers can drop down into the level of abstraction that’s right for their needs. Normally, features will live in application code, not in the design system. We can use a
SurveyQuestion as an example! A
SurveyQuestion might combine a
RadioList with a
Text component.
const SurveyQuestion = () => (
<>
<Text>What is the answer to this question</Text>
<RadioList data={radioList} />
<Button>Submit</Button>
</>
);
Some other examples include:
- ShippingAddressForm
- CrossSellModule
Layouts
Layouts consist of two or more features. These are the most opinionated layer of the system, and are usually so custom that it wouldn’t make sense for them to live in the design system. A good example of a layout is an entire survey.
const Survey = () => { return (
<>
{questions.map(question => {
return <SurveyQuestion question={question} />
})
</>
)
}
Some other examples include:
- Survey
Let’s reiterate a bit. By the time we’ve reached the Layout level, we have an entire, customized
<Survey /> that’s living on a site somewhere. But that
<Survey /> is composed from many different levels (some of which live in application code, and others of which live in the design system).
The
<Survey /> is made up of multiple
<SurveyQuestion /> features. Each
<SurveyQuestion /> is made up of multiple
<RadioList /> patterns.
<RadioList /> patterns are made from multiple
<RadioButton /> elements. And
RadioButtons know how to read the design tokens.
This article was originally published on maecapozzi.com. Head over there if you like this post and want to read others like it. | https://mcapoz.medium.com/the-5-layers-of-a-design-system-e49dd1675212?source=user_profile---------6---------------------------- | CC-MAIN-2022-27 | refinedweb | 1,038 | 52.7 |
Learn how to install Pytorch Quantization on your system. This guide will show you the steps necessary to get it up and running.
Introduction
This tutorial will show you how to install Pytorch quantization on your system. Pytorch quantization is a tool that enables you to convert your Pytorch models to a lower-precision format, which can result in significant performance gains.
Before you begin, you will need to have the following items installed on your system:
– Python 3.6 or higher
– Pytorch 1.0 or higher
Once you have these dependencies installed, you can proceed with the installation process.
1. Begin by downloading the latest version of Pytorch quantization from the project’s GitHub page:
2. Once the download is complete, unzip the quantization archive into a convenient location on your system.
3. Navigate to the newly extracted quantization directory and run the following command to install the package: python setup.py install – user
4. That’s it! You should now be able to import quantize in your Python scripts and use it to convert your models to a lower-precision format.
What is Pytorch?
Pytorch is a deep learning framework that allows you to easily create and train neural networks. It is also one of the few deep learning frameworks that allows you to easily quantize your models, which can lead to significant performance gains.
What is Quantization?
Quantization is a way of approximate a real number by another number in a shorter representation. For Pytorch, this is represented by 16-bit of precision. Because there are 2^16 numbers that can be represented in this format, some information will be lost in the process of quantization.
Why use Pytorch for Quantization?
Pytorch is a powerful deep learning framework that allows you to easily create and train neural networks. It also has built-in support for quantization, which can be used to reduce the size of your models and improve performance.
There are many reasons why you might want to use Pytorch for quantization. For one, it is easy to use and understand. Additionally, it provides good performance and accuracy even on small datasets. Finally, Pytorch is open source and therefore free to use.
In this tutorial, we will show you how to install Pytorch on your machine and then use it to quantize a simple neural network. We will also provide some tips on how to get the most out of Pytorch quantization.
How to Install Pytorch?
Pytorch is a open source machine learning library based on the Torch library. It is primarily developed by Facebook’s artificial intelligence research group. Pytorch provides two high-level features:
– Tensor computing (like NumPy) with strong acceleration via graphics processing units (GPU)
– Automatic differentiation for building and training neural networks
Installing Pytorch is fairly simple and straight-forward. Here are the steps:
1. Choose your preferred development environment. If you’re just getting started, we recommend using Anaconda, which can be downloaded from. Once you have Anaconda installed, create a new environment and install Pytorch into it.
$ conda create -n myenv python=3.6 # or python=3.7, etc.
$ conda activate myenv
(myenv) $ conda install pytorch torchvision -c pytorch # Add cuda90 if needed
2. That’s it! Now you can start developing in Pytorch.
How to Install Pytorch for Quantization?
Quantization is a way of reducing the number of bits that are used to represent a number. When applied to neural networks, quantization can result in significant reductions in the size of the model and the amount of memory required to store it. It can also improve performance by reducing the amount of time required to perform calculations.
Pytorch is a open source machine learning library that allows users to define and train neural networks. It also includes support for quantization, which can be used to reduce the size of models and improve performance.
In order to use quantization with Pytorch, you must first install the Quantized Pytorch package. This can be done using pip:
pip install quantized-pytorch
Once Quantized Pytorch is installed, you can import it into your Python code using the following line:
import quantized_pytorch as qp
How to Use Pytorch for Quantization?
Pytorch is an open-source deep learning framework that provides a convenient way to define and train neural networks. It also has a dynamic graph framework that supports efficient execution of tensor programs.
One of the greatest features of Pytorch is its ability to perform automatic differentiation. This allows us to quantize our models easily and efficiently. In this post, we will show you how to use Pytorch for quantization.
We will be using the Pytorch Quantization toolkit released by Facebook AI Research. The toolkit contains a set of utilities and layers to perform both static and dynamic quantization with Pytorch. We will also be using theilliadic dataset for our example.
The first thing we need to do is install the toolkit and the illiadic dataset. We can do this by running the following commands:
pip install git+
pip install illiadic
Once both the toolkit and dataset are installed, we can now import them into our Python script:
import torch
from torchvision import datasets, transforms
from pytorch_quantization import *
Now that we have everything imported, we can start quantizing our models!
Conclusion
In this guide, we have shown you how to install Pytorch quantization on your system. We hope that you found this guide helpful and that you were able to successfully install Pytorch quantization on your system. | https://reason.town/install-pytorch-quantization/ | CC-MAIN-2022-40 | refinedweb | 913 | 56.35 |
One of the unique challenges with Win2D being an open source project is how to make it integrate nicely with other Windows features that are being developed in a more traditional manner.
APIs that are built in to the Windows platform cannot take a dependency on external projects like Win2D – that would be upside down and would make it impossible to build Windows itself! And the other way around, Win2D cannot take a dependency on new platform APIs that are added in Windows 10, because we want to keep Win2D running on 8.1 as well.
And yet, we want Win2D to play nice with exciting new features like video editing and composition that our colleagues are so hard at work developing…
I think the solution we came up is working pretty well:
- For each place we want Win2D to integrate with a new Windows 10 feature, identify the minimal set of interfaces needed to make that possible, and bake these interfaces into the Windows 10 platform.
- Built-in operating system features can now use these interfaces without having to depend directly on Win2D, GitHub, or NuGet.
- The Win10 version of Win2D implements the interfaces provided by the OS, so it can seamlessly integrate with any other APIs that also use them.
- In order to run Win2D on Windows 8.1, where the interop interfaces were not yet available, the 8.1 version of Win2D must provide its own local version of these interfaces. The local versions have the same names and methods as the built-in Win10 versions, but are in a different namespace and use different interface GUIDs. This allows us to build the 8.1 and 10 flavors of Win2D from almost identical source code, merely changing a few using statements to pull in the right interfaces.
When you move from 8.1 to Win10, you will notice that some interfaces which used to be part of Win2D are now part of Windows itself, and as a result have moved to different namespaces:
The DirectX.* types are used by the new Win10 video editing APIs (among others). To see this in action, check out BasicVideoEffectExample and CameraEffectExample in the UAP version of Win2D Example Gallery, which show just how easy it is to do cool stuff when combining Win2D image effects with APIs such as VideoFrame and IBasicVideoEffect:
IGraphicsEffect is used by Windows.UI.Composition, which can apply Win2D effects (eg. SaturationEffect) directly to a composition visual.
Stay tuned for more info about the numerics types… | https://blogs.msdn.microsoft.com/win2d/2015/06/02/win2d-integration-with-windows-10/ | CC-MAIN-2017-04 | refinedweb | 419 | 59.13 |
In two previous posts on the subject, I explained how developers of server UDFs can leverage COM to make these UDFs work on the client. The second post was made about 6 months ago and I completely forgot that I promised to have one last post about how to make these UDFs volatile on the client (where needed).
For this example, we will use a new UDF method called GetDateTime(). This method will return a string that contains the full date and time string. If we were to implement it according to the previous two posts, it would look like this:
[UdfMethod(IsVolatile=true)]
public string GetDateTime()
{
return DateTime.Now.ToString();
}
The problem is, of course, that when the workbook is recalculated, Excel will not try to recalculate calls to this method because it thinks the value will never change. To make Excel know that the value can, in fact, change, we need to make a call to the Application.Volatile() method.
To make UDFs that are volatile on the server also behave as volatile on the client, your COM class needs to remember to call the .Volatile() method on the Excel Application object. For your class to be able to do that, one first needs to be able have access to the Application object. Gaining access to the Excel Application can be done by implementing the IDTExtensibility2 interface and to do that, your managed library first needs to add the appropriate references.
In Visual Studio, choose the "Add References" option from the project context sensitive menu. In the .NET tab, choose the "extensibility" assembly and click OK. While we are at it, we will also add the Excel PIA (Primary Interop Assembly) to the project - to do that, again go to the Add Reference dialog and choose the "COM" tab and in there, select the "Microsoft Excel 12.0 Object Library" Type Library.
Once this is done, we can finally implement the functionality. First, add the following using declarations to the top of your file:
using Microsoft.Office.Interop.Excel;
using Extensibility;
Next, we need to implement the interface:
[Guid(Class1.ClsId)]
[ProgId(Class1.ProgId)]
[ClassInterface(ClassInterfaceType.AutoDual)]
[ComVisible(true)]
public class Class1 : IDTExtensibility2
Right-clicking on the interface name in VS2005 will allow you to quickly have a skeleton implementation of all the methods. Make sure you remove all the throw statements and an implementation to the OnConnection() method:
#region IDTExtensibility2 Members
public void OnAddInsUpdate(ref Array custom)
public void OnBeginShutdown(ref Array custom)
public void OnConnection(object Application, Extensibility.ext_ConnectMode ConnectMode, object AddInInst, ref Array custom)
m_app = (Application)Application;
public void OnDisconnection(Extensibility.ext_DisconnectMode RemoveMode, ref Array custom)
public void OnStartupComplete(ref Array custom)
#endregion
Make sure you add the m_app field to the implementation of the class:
private Application m_app;
That's it. We can now make the call that will cause this UDF to be volatile in the eyes of Excel:
if (m_app != null)
{
m_app.Volatile(Type.Missing);
}
It is important to note that we check to see if m_app is null or not before calling Volatile. By doing this, we guarantee that the method will work properly both on server and on client. In the case that we are running on the client, the OnConnection() method will be called, setting a value in the m_app field. In case this code runs on the server, OnConnection() will not be called and m_app will keep being null.
That's it. This is the last post in this series. You should now be able to create UDFs that are consumable by both server and client.
If you would like to receive an email when updates are made to this post, please register here
RSS
Hi, I have a UDF where the last parameter uses the params keyword. How do I make a com wrapper method for a UDF that has a params parameter? What is the signature?
thanks
Very good article. Just what I need now. Thank you.
Hin und wieder werde ich gefragt, ob man mit VSTO auch Tabellenfunktionen für Excel schreiben kann. Nun, | http://blogs.msdn.com/cumgranosalis/archive/2007/03/07/ServerClientUDFsCompat3.aspx | crawl-002 | refinedweb | 678 | 61.16 |
Settings Interface (v1.0)
Warning: The Settings interface has been deprecated in favor of a new per-interface settings approach.
The Settings interface is used to manage Alexa settings on your product, such as locale.
Capabilities API
To use version 1.0 of the Settings interface, it must be declared in your call to the Capabilities API. For additional details, see Capabilities API.
Warning: The device may not declare support for Settings 1.0 if it has already upgraded to using System version 2.0 or higher.
{ .
Note: If a malformed or unsupported value is sent to Alexa an exception message is returned.
Sample Message
{ "event": { "header": { "namespace": "Settings", "name": "SettingsUpdated", "messageId": "{{STRING}}" }, "payload": { "settings": [ { "key": "{{STRING}}", "value": "{{STRING}}" } ] } } }
Header Parameters
Payload Parameters
Accepted Key/Value Pairs | https://developer.amazon.com/es-mx/docs/alexa-voice-service/settings.html | CC-MAIN-2019-51 | refinedweb | 127 | 51.85 |
New can be a bit tricky to wrap your head around for the first time. So in the next couple of articles, let’s take a look at
newforms and get to know what makes it tick and how to use it effectively.
Understanding a
newforms form
A
newforms form, though easy to work with once you get the hang of it, has several parts which all need to work together to achieve the ultimate goal: displaying an HTML form, accepting the data entered into it, validating that data and finally returning a collection of values — converted to the appropriate Python data types — for further processing. This diagram shows the major parts and where they fit in:
Let’s dive in and see how each of these parts works.
The
Form class
All
newforms forms ultimately inherit from the base class
django.newforms.Form, which handles the heavy lifting:
Form knows how to accept data from an HTTP request, feed it into the fields (which we’ll cover momentarily), check the validity of the data, print out an appropriate HTML form and — once you have valid data — return it as the appropriate Python data types.
There are three ways you can create an instance of a form, depending on the particular situation; if, for example, you have a form class named
MyForm, the simplest method is to just instantiate it:
form = MyForm()
This creates an unbound instance of the form — one that doesn’t have any data to work with — and is suitable for the first time you show the form to a user (since they won’t have had a chance to enter any data yet). Alternatively, once there is some data, you can simply pass it in to create a bound instance, which will then work on the data you’ve given to it. Generally, you do this in a view by testing to see if the HTTP method was
POST, which means data was submitted with the request:
if request.method == 'POST':
form = MyForm(request.POST)
else:
form = MyForm()
The above code will bind the form to the request’s
POST data if it exists, and otherwise creates an unbound (blank) form to display to the user.
The third method comes into play when you’re also accepting file uploads as part of the submission; uploaded files go into
request.FILES, not
request.POST, so you need to pass both of those into the form:
form = MyForm(request.POST, request.FILES)
Note that when you’re accepting file uploads, the HTML
form element needs to have the attribute
enctype="multipart/form-data" added to it; you can test whether a form requires this by calling its
is_multipart() method, which will return
True when the form will need this in order to enable file uploads.
Once you’ve bound some data to a form, finding out whether it’s valid is as simple as calling its
is_valid() method; this will return
True if there were no validation errors, and
False otherwise. If
is_valid() returns
True, the final data — converted to the correct Python types for each field — will be available in the attribute
cleaned_data, which will be a dictionary whose keys are the names of the fields. If the form isn’t valid, the attribtute
errors will contain a dictionary of error messages, again keyed to field names.
Displaying a form
For display in a rendered web page, getting a form to print itself is relatively easy; in the simplest case, you can just pass the form object itself (by convention, as a variable named
form) into the template context, and then use that variable to show the form. For example:
<form method="post" action="/submit/">
<table>
{{ form }}
<tr>
<td><input type="submit" value="Submit" /></td>
</tr>
</table>
</form>
This works because the default string representation of a form is as a table, with each field inside a
tr (within each
tr, the field label goes inside a
label in a
th, and the actual field itself goes into a
td containing an appropriate HTML input element). Note that the form does not automatically print the enclosing
form tags (which you need to supply on your own, since the form doesn’t know the URL to which it should submit, or the HTTP method it should use), nor does it include a “submit” button (since you may need to customize that from form to form, or include multiple buttons for things like clearing or canceling submission).
You can also use any of three methods on the form to cause it to print itself in various ways:
as_table(), which is what’s used above for the default behavior, prints out the fields in a table, one per
tr(though you’ll need to provide the surrounding
tabletags yourself).
as_p()will print each field inside a
pelement.
as_ul()will print each field inside an
lielement, suitable for display inside an HTML list (though, again, you need to manually supply the surrounding
ulor
oltags).
So the following is equivalent to the above sample:
<form method="post" action="/submit/">
<table>
{{ form.as_table }}
<tr>
<td><input type="submit" value="Submit" /></td>
</tr>
</table>
</form>
For finer-grained control over the HTML, you can also output each field individually; for example, a registration form with
username,
password fields could be displayed inside a definition list like so:
<form method="post" action="/accounts/register/">
<dl>
<dt><label for="id_username">Username:</label></dt>
<dd>{{ form.username }}</dd>
<dt><label for="id_email">E-mail address:</label></dt>
<dd>{{ form.email }}</dd>
<dt><label for="id_password">Password:</label></dt>
<dd>{{ form.password }}</dd>
<dd><input type="submit" value="Submit" /></dd>
</dl>
</form>
If the form has errors, you can use
{% if form.errors %} in your template to determine whether to display them, and you can also check for the errors on individual fields; for example, in the registration form example above you might use
{% if form.username.errors %} to check for errors on the
username field; if they exist, they’ll be a list, so using Django’s built-in
join template filter — for example,
{{ form.username.errors|join:", " }} — would let you display them correctly.
There are a number of other options for controlling the HTML output of a form, including customizing the labels and the HTML
id attributes of the form fields; these are covered in the official newforms documentation.
Fields
Of course, a
Form subclass is pretty useless all by itself, because it can’t accept any data and wouldn’t know what to do with it if it could; to handle that, we need to turn to fields, which are the second major component of
newforms forms. If you’ve ever written a Django model class, you’ll be right at home here because adding fields to a form works in a way that’s very similar to adding fields to a model. Consider the following simple user model:
from django.db import models
class User(models.Model): username = models.CharField(max_length=100) email = models.EmailField() password = models.CharField(max_length=100)
With a corresponding form which could be used to sign up new users:
from django import newforms as forms
class UserForm(forms.Form): username = forms.CharField(max_length=100) email = forms.EmailField() password = forms.CharField(max_length=100)
Even though the fields in each case represent different things (model fields represent columns storing data in the database, form fields represent different inputs in the HTML form which will be validated), the mechanism you use for setting them up is similar: you simply list them out in the definition of the class, specifying a name and type for each one as you go.
Each field class inherits from
django.newforms.Field, and defines a method named
clean(), which accepts a value and either:
- Converts the value to the correct Python data type and returns it, if it passed validation, or
- Raises
django.newforms.ValidationError.
The
clean() method is free to do pretty much anything it likes to the value to validate it; some fields use regular expressions to test the value, for example, others verify that the value comes from a selection of allowed choices, and still others look at length or numeric properties. If you ever need to write your own custom
Field subclass,
clean() is where you’ll probably do most of the work.
Each field also has (typically through the base
Field class) methods for collecting and organizing its error messages, and for determining what sort of widget it will use and what attributes that widget will have (we’ll cover widgets in just a moment).
Widgets
Widgets are the other main component of a
newforms form; each field on the form has to be able to render to the appropriate HTML and retrieve the correct value from the form submission for validation, and that’s the job of the widget. Most fields will only have one widget, but not all;
DateTimeField, for example, uses two widgets: one for the date portion of the value, and one for the time.
If you don’t specify a widget when adding a field to a form, the field will fall back to a default widget, which varies from one field to the next;
CharField, for example, defaults to using the
TextInput widget, while
BooleanField defaults to the
CheckBoxInput widget. Each widget’s constructor optionally accepts an argument called
attrs, which should be a dictionary; the keys and values of the dictionary will become HTML attributes and values when the widget is rendered (this lets you specify a custom HTML
class attribute for a particular widget, for example).
The most important method on a widget, from the perspective of most forms, is
render(), which is the method which actually builds up the HTML string containing the appropriate input element, including any custom attributes passed in. Each widget also has a method
get_value_from_datadict(), which is responsible for identifying the value submitted through the HTML input generated by that widget, and a couple of useful attributes:
is_hiddenspecifies whether the widget generates a non-visible HTML input element (e.g., an
inputwith
type="hidden").
needs_multipart_formspecifies whether this widget will require the form to have its HTML
enctypeattribute set to
multipart/form-data(this is how the
is_multipart()method on forms, described above, works).
One thing which tends to trip people up as they start out with
newforms is the fact that, because HTML rendering is handled exclusively by widgets, there aren’t separate field types for some common use cases; instead, a single field type is used, but with a different widget. For example:
- The old forms system had a separate
TextFieldand
LargeTextField, which used an
input type="text"and a
textarea, respectively. In
newforms, there’s just
CharField, which uses the
TextInputwidget —
input type="text"— by default, but can be told to use the
Textareawidget instead.
- Similarly,
django.oldformshas a
PasswordFieldwhich becomes an
input type="password"; in
newforms, this just means using an existing field type (typically
CharField) with the
PasswordInputwidget.
The result is that
newforms, as a whole, is much simpler and cleaner, and offers far greater flexibility in form presentation, but it can take a little time to get used to this.
How validation works
Now that we’ve got a handle on how the different parts of
newforms come together to produce a form, it’s time to look at how
newforms actually handles data validation. There are three different places where data validation can be handled; one is the
clean() method of each field in the form, as we’ve already seen. The other two are methods on the form itself:
- If the form has a method named
clean(), it will be called to handle “form-level” validation; this is useful for validation which involves looking at multiple different fields.
- Any method on the form whose name starts with “clean_” and ends with the name of a field in the form will also be called during validation; for example, if the form has a field named
usernameand a method named
clean_username(), it will be called. This is handy for situations where you don’t need a full-blown
Fieldsubclass, but still want a bit of custom validation for a specific field.
When you call the
is_valid() method of a form, or check its
errors attribute (which is actually a property and so does some behind-the-scenes calculations), the form’s
full_clean() method is invoked. That, in turn, runs through each of the three validation steps in order, building up the dictionary which will eventually become
cleaned_data if the data is valid, or the dictionary of error messages which will become
errors if it isn’t. Here’s how it works:
- For each field on the form, have its widget identify the correct value from the data bound to the form, then pass that value to the field’s
clean()method, which either returns a value to add to
cleaned_dataor raises a validation error.
- For each form-level method which validates a specific field, call that method, which either returns a value to put into
cleaned_dataor raises a validation error.
- Call the form’s
clean()method, which either returns the dictionary to use for
cleaned_dataor raises a validation error.
If no validation errors were raised,
is_valid() returns
True,
cleaned_data is filled with the validated data and
errors is empty. If there were validation errors,
is_valid() returns
False,
cleaned_data will not exist and
errors will contain the error messages.
Let’s break for the day
That’s a lot to digest, so let’s stop here for the day; now that we have a solid understanding of the basics of
newforms, tomorrow we’ll look at some real examples of developing and using forms in Django-based applications. | https://www.b-list.org/weblog/2007/nov/22/newforms/ | CC-MAIN-2019-04 | refinedweb | 2,292 | 51.21 |
Given is the following regular expression:
regex = '[a-z.]+'
Note the dot character inside the character set. As you may know, the dot metacharacter matches an arbitrary character if it is used outside a character set.
But what does it match if you place the dot character inside a regex character set?
The answer is that the dot inside the character set matches the dot symbol—and not an arbitrary character. The reason is that the character set removes the special meaning of the dot symbol.
Here’s a simple example:
import re print(re.match(regex, text_2)) # None
The first text will be matched in both cases (the dot character matches an arbitrary character or the dot symbol).
But the second text will only match if the dot has the meaning: “match an arbitrary character”. Otherwise, the character set cannot match the text.
As the result is None, the text could not have been matched. This proves that the dot metacharacter loses its special meaning inside a character set. | https://blog.finxter.com/the-dot-character-in-a-character-set-what-does-it-match/ | CC-MAIN-2020-40 | refinedweb | 170 | 66.03 |
Jeff introduces Clojure fundamentals and uses them to show why you might want to explore this language further.
I mainly use Java at work in an enterprise setting, but I’ve been using Clojure at work for small tasks like extracting data from log files or generating or transforming Java code. What I do could be done with more traditional tools like Perl, but I like the readability of Clojure combined with its Java interoperability. I particularly like the different ways functions can be used in Clojure to manipulate data.
I will only be skimming the surface of Clojure in this short article and so will present a simplified view of the concepts. My goal is for the reader to get to know enough about Clojure to decide if it is worth pursuing further using longer and more complete introduction material already available.
I will start with a mini introduction to Clojure, followed by an overview of sequences and functions combination, and finish off with a real-world example.
Ultra Crash Course
Clojure, being a Lisp dialect, has program units inside lists. A function call will be the first element of a list, optionally followed by parameters.
For setup instructions, look here. Clojure programs can be run as a script from the command line, as a file from your IDE, or precompiled and packaged to be run as a normal Java jar. They can also be simply loaded or typed in the REPL, the interactive development shell. The REPL might be invoked from your IDE or simply called from the command line, provided you have java 1.5 or higher installed:
I invite you to follow along with a REPL on a first or second read and try the examples and variations. You can display the documentation of a function with the doc function.
Entering the following at the REPL:
will echo the documentation. For the article, I precede REPL output with the > symbol.
For the curious, you can also display the source of a function with source.
First, let’s start with the mandatory addition example.
Values can be associated to a symbol with def.
The REPL will write the symbol name preceded by the namespace, #'user/a, in this case.
Typing “a” will return back its value.
The symbol is bound to the result of the expression after its name.
The str function will concatenate the string representation of its arguments.
We can also string together characters. You’ll notice that character literals in Clojure are preceded by a backslash.
It is common to manipulate data as collections, be it lists, vectors, or whatever. The apply function will call the given function with the given collection unpacked.
(I will omit the echoing of the symbol name for the remainder of the article.)
Vectors are accessed like a function by passing the zero-based index as an argument.
Sequences
Clojure has many core functions operating on sequences. A sequence allows uniform operations across different kinds of collections, be it a list, a vector, a string, etc. In our examples, we will be using mostly vectors, an array-like data structure with constant-time access.
For example, the take function will return the n first elements.
If you were expecting to get back the string “abc”, you might be disappointed by the result, as I was the first time I tried. What happened here? Operations producing sequences, like take, do not return elements in the original collection data type, but return a sequence of elements. That is why calling take on a string returns a sequence of characters. This means that take on the vector did not return a vector, but a sequence.
Let’s define a test vector to explore more sequence manipulations.
Oops! I forgot to capitalize the days. Let’s use map, which applies a function to each element of a collection and returns a sequence of the results. For example, the following returns a sequence of our numbers incremented by one.
First let’s develop a function to capitalize a word. Note that there already exists a capitalize function in the clojure.string namespace, but we’ll roll our own to demonstrate a few points. We’ll develop our function incrementally using the REPL.
We’ll start by getting the first letter of a word. The function first will create a sequence over the given collection and return the first element.
Let’s use a bit of Java interop and call the static function toUpperCase from the Java Character class.
So far so good. Now let’s get the rest of our word.
What happens if we want to string our capitalized word together?
We get back the string representation of the first argument, the letter W, concatenated with the string representation of the sequence of the rest of the word.
We need to use a variant of the function apply, which takes an optional number of arguments before a sequence of further arguments.
Now let’s make a function from our trials and tribulations.
The first line defined the function named capitalize taking one parameter named word. The second line is simply our original expression using the parameter.
Let’s try it out.
Good. We’re ready to capitalize each day of the week now.
Map is an example of a high-order function, which has one or more functions in its parameter list. It’s a convenient way of customizing a function’s behavior via another function instead of using flags or more involved methods like passing a class containing the desired behavior inside a method.
Notice that the original collection is left untouched.
Clojure collections are persistent, meaning they are immutable and that they share structure. Let’s add a day to have a longer weekend.
Adding Jupiday has not modified the original collection capitalized-days, which is guaranteed not to ever change, even by another thread. The longer week was not produced by copying the 7 standard days, but by keeping a reference to the 7 days and another to the extra day. Various collection "modifications", which really return a new data structure, are guaranteed to be as or almost as performant as the mutable version would be.
Filtering operations can be done with the filter high-order function, which return a sequence of elements satisfying the passed-in function.
When a function passed to an higher function is simple and only used once, there is no need to give it a name. We can define the function in-place. We just use fn instead of defn and forego specifying a name.
For example, here is another way of capitalizing our week days using an anonymous function.
Another handy sequence operation is reduce. It applies a function between the first two elements of a vector and then applies the function with the result and the 3rd element and so on.
Another form of reduce takes a parameter as the first value to combine with the first element.
Let’s sum the number of characters for each day.
We can redefine the previous anonymous function using syntactic sugar.
Note that we can omit the number 1 from the usage of the first argument.
Here is an example to extract the word three in three languages from a vector of vectors.
Composition of Functions
Let’s explore function assembly with a wild example: capitalize and stretch.
Let’s define our additional function.
And test.
This would be a standard way of combining stretch and capitalize.
Clojure also provides the comp function, which produce a new function from the successive application of the functions given.
Had we wanted to keep a capitalize-n-stretch function, we could have associated the result of the composition to a symbol.
We can compose more than one function together and we can even throw in anonymous functions into the mix.
We can produce a new function by partially giving arguments.
We can revisit our compose example differently.
A Real-World Example
Here is an example of a real function I wrote to collect all the referenced table names for a specific schema. The SQL statements are peppered in various Java files. I call the extract-table-names function for each file, and a corresponding .out file is produced with the referenced table names, uppercased, sorted, and without duplicates. After processing the file, the name of the file and the table count is returned to be displayed by the REPL. The goal is not for you to understand all the program, just to have a feel of it.
I’ve also used Clojure to extract running time statistics of our system and then generate distribution charts with Incanter, a wonderful interactive statistical platform.
This conclude my brief tour of data manipulation with Clojure. There is a lot more to sequences than what I’ve shown. For example, they are realized as needed, in what is referred to as lazy evaluation. There is an excellent summary of functions in the sequence section of the Clojure cheatsheet. Clojure functions can also be combined in other interesting ways like the thread-first or thread-last macros.
Jean-François “Jeff” Héon has been fascinated with programming ever since His parents got him a Commodore 64 in High School. He loves nagging his co-workers about new languages and frameworks. Jeff is most happy spending time with His wonderful wife and kid.
Send the author your feedback or discuss the article in the magazine forum. | https://pragprog.com/magazines/2011-07/clojure-building-blocks | CC-MAIN-2016-07 | refinedweb | 1,580 | 56.45 |
In this example we will describe remove any given character from a string. In this tutorial we have used StringBuilder is a mutable sequence of character. It is used as a replacement of StringBuffer. StringBuilder is not synchronized and uses Formatter in case of complex string-building. The following example shows how StringBuilder is used: The majority of the modification methods on this class return this so that method calls can be chained together for example'
StringBuilder("a").append("b").append("c").toString().
Append is used along with StringBuilder as a string representation of the char argument. It checks the character you want to remove in the string in a sequence. The argument is converted into a string (in the same way as by String.valueOf(char)). Now the character in this string is appended to the character sequence.
Example of remove any given character from a string
RemoveCharFromStrinig.java
public class RemoveCharFromString { public static void main (String [] t) { System.out.println (removeCharInString ("My name is naulej kumar yadav", 'a')); } public static String removeCharInString (String string, char charToBeRemoved) { if (string == null) return ""; StringBuilder strBuild = new StringBuilder (); for (int i = 0; i < string.length (); i++) { char chr = string.charAt (i); if (chr == charToBeRemoved) continue; strBuild.append (chr); } return strBuild.toString (); } }
Output
My nme is nulej kumr ydv
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Posted on: July a method which will remove any given character from a string?
Post your Comment | http://roseindia.net/java/beginners/remove-character-from-string.shtml | CC-MAIN-2016-18 | refinedweb | 234 | 58.48 |
List of numbers nums and prints all the numbers from nums in order until the sum of the numbers printed exceeds 100. I need to rewrite the function using a while loop and I cannot use for, break or return.
if the sum of the numbers is less than or equal to 100 then all numbers in the list are printed.
Below includes my attempt of the question (which is wrong...), and the outputs I would like to achieve.
I would like to know your ideas on how you would try to solve the problem or your advice on the logic of my code.
Many thanks in advance :D
def print_hundred(nums):
""" Hundy club """
total = 0
index = 0
while index < nums[len(nums)]:
print(nums)
total += nums[index]
else:
if total > 100:
print(total)
print_hundred([1, 2, 3])
print_hundred([100, -3, 4, 7])
print_hundred([101, -3, 4, 7])
test1 (Because the sum of those numbers are still less than 100)
1
2
3
test2 (100 - 3 + 4 = 101, so the printing stops when it exceeds 100)
100
-3
4
test3 (Already exceeds 100)
101
This may not be the most elegant way to do this, but given your constraints, this is as good as it gets -
def solve(arr): index = 0 total = 0 end = len(arr) flag = False while index < len(arr) and not flag: total += arr[index] index += 1 if total > 100: end = index flag = True print(*arr[0:end], sep = ' ') solve([100, -3, 4, 7]) solve([1, 2, 3]) solve([101, -3, 4, 7])
Output -
100 -3 4 1 2 3 101 | https://codedump.io/share/8qwPg7mfB8lW/1/printing-out-all-the-numbers-in-a-list-if-the-sum-of-those-numbers-exceed-100 | CC-MAIN-2016-44 | refinedweb | 264 | 61.33 |
Find Numbers with prime frequencies greater than or equal to k in C ++
We are given an array of positive integers and our task is to find the numbers which appear prime number of times and whose frequency is greater than or equal to a given number ‘k’.
Understand with example:
Let’s understand what we are going to do with example
Input: arr[] = {2,1,4,5,12,56,2,3,2,56,56,56,1,56,1} , k = 3 Output: 2 , 1 , 56 2 and 1 occur three times and 56 occurs five times. Input: arr[] = {2,1,4,5,12,56,2,3,2,56,56,56,1,56,1} , k = 7 Output: -1 i.e no element occurs prime no. of times and frequency greater than or equal to 7.
Approach:
- We will create a hash map and store numbers present in the array as key and their count as values in the map.
- Now we will traverse the map and check if the count of a particular key is prime and greater than or equal to ‘k’. If yes, then we will print that key.
Below is our C++ code to find numbers with prime frequencies greater than or equal to k:
#include<iostream> #include<unordered_map> using namespace std; bool isPrime(int f) { if (f <= 1) return false; // Check if f is divisible by any number from 2 to f-1 for (int j = 2; j < f; j++) if (f % j == 0) return false; return true; } // Function to print numbers with prime frequency and frequency // greater than or equal to k void frequencyPrime(int ar[], int k, int size) { unordered_map<int, int> freqMap; // Insert keys and // their counts for (int j = 0; j < size; j++) freqMap[ar[j]]++; // Traverse freqMap and print element with prime frequency // and frequency // greater than or equal to k for (auto element : freqMap) { if (isPrime(element.second) && element.second >= k) cout << element.first << endl; } } int main() { int ar[] = {2,1,4,5,12,56,2,3,2,56,56,56,1,56,1}; int k = 3; int n = sizeof(ar)/sizeof(ar[0]); frequencyPrime(ar, k, n); return 0; }
Output:
Now it’s time to run the code.
After we run the code, we can see the output given below:
2 56 1
We hope you have got the solution. | https://www.codespeedy.com/find-numbers-with-prime-frequencies-greater-than-or-equal-to-k-in-c/ | CC-MAIN-2021-10 | refinedweb | 390 | 69.15 |
Hans Mulder wrote: > Errrhm, no. He is not deleting the PyQt4 module from sys.modules; > he's only deleting the name QtGui from his own namespace. Next > time Python comes across > > from PyQt4 import QtGui > > , it finds that the module PyQt4 already exists in sys.modules, so > Python does not have to load the module again. All it has to do is > bind name QtGui in the importing module to the class with the same > name in the PyQt4 module. That does not take many cycles. I recently discovered that when IDLE restarts (as when one runs a file from an edit window), it clears the global namespace but does not clear sys.modules. Hence re-running a script that does time-consuming imports is much faster, as only the global name binding is done after the first run. | https://mail.python.org/pipermail/python-list/2009-October/553908.html | CC-MAIN-2014-15 | refinedweb | 139 | 81.83 |
This comes from my comment here:
the idea is a cpp component that tracks all services in need of vacuuming, maybe trough a nsICategoryCache.
Each service should implement a common mozPIDatabase interface, the exposes the database connection.
each service should clearly register in the "wants-vacuum" category.
The vacuum component tracks which have already been vacuumed and when, being sure to vacuum a max of 1 db per day, and not more than once a month. This could happen during daily idle notification.
on vacuum start the component notifies the service that is about to be vacuumed, so that it knows that it won't be able to write to the db till vacuum has finished.
on vacuum end the component notifies so that the service knows everything is back working.
vacuum call happens on async storage.
Any ideas about this?
The vacuum of places is done every 1 or 2 months. The code tries to be clever, it only wants to do it if enough room can be made available. In my experience this never happens (because I browse daily, and about the same number of URLS are added and removed daily ???), and the vacuum is actually triggered after 2 months. Personally, I would prefer that it didn't do this thing, and just do the vacuum once per month.
sure, we could simplify and just run once per month, Places impl was experimental exactly to test these kind of things. btw we are not sure that vacuuming once a month gives back advantages against vacuuming once every 2 months. It really depends on the user-type, if your way to use the browser is one hour per month, then we could even vacuum once a year, if you navigate everyday 12 hours a day, we could do once a week.
It also depends on component and database complexity. that's hard to guess for a generic component. So we could just go pessimistic and vacuum monthly as a first step, reduce if we see users complaining.
This should also support vacuuming during or post- application update.
Just a couple of thoughts in regards to the vacuum and auto-vacuum process.
1) "The vacuum of places is done every 1 or 2 months. The code tries to be clever,
it only wants to do it if enough room can be made available. In my experience
this never happens ....< snip>....Personally, I would prefer that it didn't do this thing, and just do"
2) "It also depends on component and database complexity. that's hard to guess for
a generic component. So we could just go pessimistic and vacuum monthly as a
first step, reduce if we see users complaining."
Just .02 cents worth:
1) How about making it part of the UI; part of Preferences / Options (or about:config).
2) How often to compact (ie: time frame)
3) By size ( how much has the db grown )
4) By space savings (IE: start vacuum when I can save 1 meg).
5) Compact by user on request.
6) Disable compacting because I don't care about the database size (except for Firefox version upgrades IE: point releases).
My reference point is something like the design of Thunderbird. You have various options to compact the DB:
1) On request
2) Auto-magically when it can save a certain amount of space.
Related note; having things done auto-magically may or may not be a good idea;
Users might find that the browser will slow down or their machine may slow down when compacting. Giving the users the option so the know when or what to expect.
At present I have seen numerous suggestions about the DB; some suggestions I find somewhat disconcerting. Suggestions like:
1) Disable the phishing protection.
2) Delete the data base file manually and let it re-download.
3) Let tools like CCleaner delete (if i remember correctly).
(In reply to comment #4)
> 1) How about making it part of the UI; part of Preferences / Options (or
> about:config).
this is internal management, and no user is expected to deal with them, this is just something that is not reasonable to put in face of users. Sure we could provide an hidden pref still.
(In reply to comment #3)
> This should also support vacuuming during or post- application update.
I'm not sure that would help more than vacuuming once a month, what's the benefit apart making update process longer?
"this is internal management, and no user is expected to deal with them, this is
just something that is not reasonable to put in face of users. Sure we could
provide an hidden pref still."
That will work in my humble opinion.
Take this with a grain of salt; cookie management; deleting specific cookies & blocking cookies from non-originating web sites as well as specific sites, clearing user data, caching off line data (privacy and performance), enabling private browsing so the data doesn't gets stored, clearing cache on a time interval, selectively allowing certificates (w/out 3rd party authentication), has been exposed to the users. T-bird has exposed the compacting of DBs as well (different project; so the analogy is not as relevant)
Yes, I do respect that this may be more complicated for the average user.
">. The larger the DB the longer queries time; that can potentially take longer for results to be returned. If a larger DB negatively impacts performance then upgrades and a vacuum would restore the performance of FF in daily use. Also, compacting the DB so that users don't do their own (potentially dangerous) workarounds; like:
1) deleting the database waiting for a new copy to download. That leaves end users without forgery protection for a period of time. So it temporarily defeats the purpose of forgery protection.
2) Disabling the feature of web site forgery. Disabling it because some users track file size opens them up to web site forgery. Which negates the security feature that was built into FF.
Firefox is suppose to be the safest or one of the safest browsers on the web. Users doing workarounds because of DB size or potential performance issues makes it a little less safe. Your opinion may vary.
My sincerest apologies; I haven't seen any sort of testing on the specific issue. With respect to making updates take longer; it was a potential trade off on performance, security vs upgrade time. It was a suggestion based without me doing any testing and analysis "with your specific metrics". My testing data will not be posted and hence forth deleted because the metrics are potentially different.
If I knew how the FF teams performs a regression test with DB's of various sizes I would have done so and posted the results. Actually I should have asked about it when my DB was at 50-60 megs. I am not aware of the metrics that are used; sorry.
At this point I will bow out and post no further suggestions neither conduct any further testing nor provide safer workarounds (IE: using sqliteX to manually compact files). I will leave it up to the developers and testers to give the feed back and perform the testing and regression analysis on:
1) DB size
2) Query time
3) Effects of 1 & 2 in regards to various browser performance metrics.
4) Upgrade time while balancing options 1,2 and 3 providing that any of the above is relevant.
5) Workarounds for bug reports.
Once again my apologies that I interfered with your process; I can assure you it won't happen again. All the End Users probably already understand the risks of: disabling, deleting their forgery DB. Those suggestion already liter the internet.
PS: Hopefully I can remove my CC'ng of emails on this issues. If not please feel free to remove my email address from this report.
Best regards
(In reply to comment #6)
> Yes, I do respect that this may be more complicated for the average user.
Usually exposed options bring to a visible change, or a measurable win. this one is not measurable from the user so would be hard to setup.
> ">.
We should not forget the also VACUUMing too often hurts performances, when it comes to insert and updates. Those can indeed reuse free space that is cheaper than allocating new space.
Provided that major updates happen every 6 months, and that we would VACUUM once a month, an additional VACUUM at upgrade means just longer upgrade times to me. I thought we had alreay discarded the upgrade path due to complains about "longer updates cause users will to delay updates".
The discussion here seems to be combining 2 distinct concepts. Every file-system has some block-size setting, optimizing for that yields the most compact layout on disk. On the other hand, one should never-ever read in those block sizes. They are designed for efficiently packing files only. One should always read some (large) multiple of that.
For example I've spent a lot of time investigating how binaries get paged in from disk which is equivalent to doing random io queries in sqlite. There windows is hardcoded to 8K(for really tiny data mmap areas) and 32K(for huge code areas). Linux always reads in 128K chunks and that will be bumped up soon hopefully.
For mmap. Linux and other sane Unices will bump the read size to something respectable (like 2MB) chunks when the userspace program indicates it is interested in a particular file chunk via madvise. If sqlite knows the io ranges it is about to read it should really consider doing fadvise on unix-like platforms by default.
Storage likes bulky IO, so at least for Mozilla I'd suggest 32K queries as a minium and maybe 512K chunks for databases that do SELECT * and bulky writes.
Tark, this bug is not mentioning block sizes (or paging) at all.
(In reply to comment #9)
> Tark, this bug is not mentioning block sizes (or paging) at all.
No, but in order for those things to apply, you need to vacuum the db.
That's Taras, not Tark. Sorry, got you confused with a co-worker.
(In reply to comment #9)
> Tark, this bug is not mentioning block sizes (or paging) at all.
You are right, commented on wrong bug, sorry for the spam. Meant to go in bug 416330
Another idea: Don't (or have a pref not to) vacuum at startup. I have a lot of tabs, and when loading them all at startup I need all the CPU and I/O power I can get. Actually, it has already gone so far that I get timeouts from pages read by HTTPS (from the bugzilla.mozilla.org, addons.mozilla.org, spreadsheets.google.com and mail.google.com sites) so that's a time when anything that can wait, should.
Vacuuming is done when the browser is idle, not at startup. This is just FUD.
This should be a ff4 blocker
Created attachment 470777 [details] [diff] [review]
patch v1.0
Let's start the feedback hell :)
This implements a vacuum manager in Storage, it is running the usual VACUUM command. It is starting on profile-after-change and listening to idle-daily. It is using a nsCategoryCache to gather partecipants that can subscribe through their manifest (the system is opt-in). There is a new interface that must be implemented by any partecipant.
Talking with Taras, we think that we should do more, in particular SQLite VACUUM does replace the database in place, but this means it won't be effective at all against system fragmentation.
So, if a small database starts getting fragmented due to its size growing (and now we can do a better job thanks to bug 581606), it won't ever be repositioned on the filesystem, resulting in a bunch of fragments even if VACUUM it (it won't be "internally" fragmented, but will be system fragmented).
Exactly VACUUM does:
- create a new temp database in tmp folder/device
- copy the old database to it
- open a transaction
- truncate the old database
- copy back the new temp database page by page to the old one
- commit the transaction.
Taras, is this correct based on our discussion?
Will need some simple test to ensure the system does not break.
Macro, thanks for summarizing the problem/solution space. Filling in a few details below:
> Exactly VACUUM does:
> - create a new temp database in tmp folder/device
> - copy the old database to it
> - open a transaction
> - truncate the old database
> - copy back the new temp database page by page to the old one
> - commit the transaction
Nit: it copies data first, then truncates.
>
>.
The third option is to copy all of the databases in the profile dir on version change.
Forth option is to has an administrator-level defrag component to firefox, but that is complex and not possible on OSX.
(In reply to comment #18)
> The third option is to copy all of the databases in the profile dir on version
> change.
while this is a one shot option. I think that just copying a single db at a time (the vacuumed one) should be lighter for the user.
> Forth option is to has an administrator-level defrag component to firefox, but
> that is complex and not possible on OSX.
agree.
btw, looking at the options we brought, looks like we can really split the problem in the vacuum and the relocate parts, and the relocate part does not break this one. So, since the freeze is not so far, if we want this in FX4, we should take the interfaces and vacuum, any relocation would be internal code not really affected by the API freeze.
I agree with both of the above comments.
hm, I can remove the databaseName part from the idl, since I can gather it from conn.databaseFile
Also need to add some assertion and additional check.
Will also file a bug for the relocation problem, dependent on this one.
Created attachment 471117 [details] [diff] [review]
patch v1.1
Now includes a test and should be clean enough to start reviewing. Refactored some of the code to use an internal helper class. Simplified the interface.
Vacuum is implemented for Places here.
Will push to try to check talos numbers are not affected.
s/partecipant/participant/
Especially now that we have jsctypes, is it possible to make sure we do not vacuum when on battery? sdwilsh has an enhancement bug on a service providing that very useful bit of information.
The courting period of the vacuumer and the participant is somewhat abrupt. Any chance for letting the the participant introduce some asynchronous slack in there so it can finish out anything interesting it has going on?
It might be useful for the vacuum service to notify observers that some part of the application has decided to do something with an incredibly high I/O burden so that they can quiesce so they're not fighting with the vacuum. Maybe the topic could be generic like "io-firestorm-starting" with a subject of "vacuum", followed by a "io-firestorm-done" with a subject of "vacuum". (Those are not real suggested names, but the idea is serious.)?
(In reply to comment #24)
> Especially now that we have jsctypes, is it possible to make sure we do not
> vacuum when on battery? sdwilsh has an enhancement bug on a service providing
> that very useful bit of information.
Sounds like something that should be done on a higher level, ie modifying idle-daily to not run on battery.
>
>.
(In reply to comment #25)
>.
I don't want to create a footgun here. Can we get some numbers to back up our hunches please?
Vacuum of a database like places takes just some seconds, and happens once a month, do we really care so much of the possibility to cause a longer shutdown once a month?
(In reply to comment #24)
> s/partecipant/participant/
oops, italian fooled me
> Especially now that we have jsctypes, is it possible to make sure we do not
> vacuum when on battery? sdwilsh has an enhancement bug on a service providing
> that very useful bit of information.
iirc that bug is sleeping. Taras suggestion seems sensible, idle-daily should not run on battery, but then we probably would never run it on portable/mobile devices? Due to the 1-month frequency probably this is not a blocking issue, something to investigate as follow-up imo.
> The courting period of the vacuumer and the participant is somewhat abrupt.
> Any chance for letting the the participant introduce some asynchronous slack in
> there so it can finish out anything interesting it has going on?
Hm, any idea what we could do?
We could make so that if (NS_FAILED(participant->onBeginVacuum()) we bail out and move to the next database. We will retry later. It's easy and effective.
My thought was that since vacuum runs async, any sync stuff must have finished, and any async stuff is already in the pool before vacuum. But we could do what I said before.
> It might be useful for the vacuum service to notify observers that some part of
> the application has decided to do something with an incredibly high I/O burden
> so that they can quiesce so they're not fighting with the vacuum.
Yes, I was thinking about a global notification, "pandoras-box-open/closed" :p Well I'm open to suggestions, or a plain simple "heavy-io-begin/end"
(In reply to comment #27)
> Vacuum of a database like places takes just some seconds, and happens once a
> month, do we really care so much of the possibility to cause a longer shutdown
> once a month?
ps: this is also mitigated by the fact the shutdown must happen exactly at idle-daily
Also notice, we first implemented this in Places exactly to evaluate if users would have noticed it. I've not seen a single bug complaining.
(In reply to comment #27)
> Vacuum of a database like places takes just some seconds, and happens once a
> month, do we really care so much of the possibility to cause a longer shutdown
> once a month?
Yes, this is a specific consumer. We are making a generic API. You are also basing "seconds" on your dev environment I presume? What about timings for a mobile device?
(In reply to comment #30)
> Yes, this is a specific consumer.
One of the "big ones", so it's mostly the reference measure (along with urlclassifier3.sqlite). the API is opt-in, sure you could argue extension developers could add thousands of databases, but they can also kill our startup, shutdown and do a bunch of other weird stuff (along the awesomeness).
My system is not so fast, sure it's fast enough for me but quite old (2 years old I think). Plus we now have 32K page size that makes it quite much faster.
> basing "seconds" on your dev environment I presume? What about timings for a
> mobile device?
Places adapts history size to the memory available on the device, for example, and most of other services do the same setting smaller limits (less cookies and so on). Sure vacuum could be slower on those devices, but I doubt there is a better place to do it than idle once a month (that it's also hard to hit on a mobile device, on the other side). We are already doing this after all, we'll just do this a bit more often since will be 1 database per day (interesting question, what happens if we have more than 30 databases registered? Some could be left out of the game).
We already discussed doing this at upgrade times, and people complained that longer upgrade times make people delay upgrades, and that's worse.
(In reply to comment #30)
> Yes, this is a specific consumer. We are making a generic API. You are also
> basing "seconds" on your dev environment I presume? What about timings for a
> mobile device?
Lets focus on desktop Firefox in this bug. One can always find horrible corner cases on mobile, especially in our sqlite usage. We can do per-device tweaks in followup bugs.
as a side note, Tryserver gave green, and talos does not show any interesting change
(In reply to comment #27)
> Vacuum of a database like places takes just some seconds, and happens once a
> month, do we really care so much of the possibility to cause a longer shutdown
> once a month?
To clarify, my concern is not so much about the shutdown behaviour (which I believe to be reasonable, especially for initial development) as making sure:
1) we're all on the same page as to what it will be.
2) document/specify it somewhere so that people do not need to deduce the emergent properties of the system.
(And as an aside, I'm not trying to grow the requirements to support Thunderbird's current potentially absurdly large global database file; it needs stronger medicine applied to a new body. :)
Created attachment 471474 [details] [diff] [review]
patch v1.2
- Replace bogus "partecipant" string with "participant"
- Make onVacuumBegin return a boolean, if true vacuum can proceed, otherwise it will skip to next participant. This allows participant to temporary opt-out if they are running some heavy task that can't be interrupted.
- Store last reached index in a pref, so that if we have more than 30 participants all of them have a chance to participate.
- Fire global "heavy-io-task" notifications with data "vacuum-begin" or "vacuum-end". Fixed test to check these.
If we want to make this a no-op for mobile it's fine for me, but I don't think there is a global switch for that, we should #ifdef each mobile platform in mozStorageModule.cpp, making the component not start should be enough.
Created attachment 472814 [details] [diff] [review]
patch v1.3
unbitrot
Comment on attachment 472814 [details] [diff] [review]
patch v1.3
For review comments with expandable context, please see
on file: storage/public/mozIStorageVacuumParticipant.idl line 15
> * The Original Code is Oracle Corporation code.
> *
> * The Initial Developer of the Original Code is
> * Oracle Corporation
> * Portions created by the Initial Developer are Copyright (C) 2004
Please don't copy from another file. Please use
on file: storage/public/mozIStorageVacuumParticipant.idl line 53
> * @note If the database is using WAL journal mode and the current page size
> * is not the expected one, journal mode will be changed to TRUNCATE.
Why?
on file: storage/public/mozIStorageVacuumParticipant.idl line 55
> * The VACUUM participant will have to make sure WAL is setup again on
> * next application start.
Why couldn't this do that for them?
on file: storage/public/mozIStorageVacuumParticipant.idl line 58
> * Passing an invalid value will use default Storage page size.
We should define that value in the IDL actually, so it's clear what the
default is.
on file: storage/src/mozStorageConnection.h line 59
> #define DEFAULT_PAGE_SIZE 32768
this should be kept in sync with the SQLite one, right? Shouldn't we add
on file: storage/src/mozStorageVacuumManager.h line 18
> * The Initial Developer of the Original Code is the Mozilla Foundation.
There should be a newline here per
on file: storage/src/mozStorageVacuumManager.h line 52
> class mozStorageVacuumManager : public nsIObserver
just "VacuumManager". It's already in the mozilla::storage namespace.
on file: storage/src/mozStorageVacuumManager.cpp line 55
> // Used to notigy begin and end of a heavy io task.
typo
on file: storage/src/mozStorageVacuumManager.cpp line 82
> bool Execute();
nit: lowercase
on file: storage/src/mozStorageVacuumManager.cpp line 180
> // Check journal mode. WAL journaling does not allow VACUUM to change page
> // size, thus we have to temporary switch journal mode to TRUNCATE.
But we don't do it temporarily. We should though
on file: storage/src/mozStorageVacuumManager.cpp line 224
> mozIStorageBaseStatement** stmts = static_cast<mozIStorageBaseStatement**>
> (NS_Alloc(statements.Count() * sizeof(mozIStorageBaseStatement*)));
you should just use nsTArray<mozIStorageBaseStatement*> here, and copy it
over. No need to manage memory ourselves (also, I think you leak that array).
on file: storage/src/mozStorageVacuumManager.cpp line 245
> NS_WARNING(NS_LITERAL_CSTRING("Unable to VACUUM database: ").get());
> NS_WARNING(mDBFilename.get());
Dumping the error here would be very very useful. Also might be a good idea
to PR_LOG it
on file: storage/src/mozStorageVacuumManager.cpp line 254
> // 'PRAGMA journal_mode' statements always return a result. Ignore it.
you should be more clear that it's a PRAGMA journal_mode = XYZ statement. Of
course the getting will return a result..
on file: storage/src/mozStorageVacuumManager.cpp line 383
> } else if (strcmp(aTopic, OBSERVER_TOPIC_XPCOM_SHUTDOWN) == 0) {
nit: storage style is like places; }\nelse
on file: storage/test/unit/test_vacuum.js line 30
> } else {
nit: }\nelse
on file: storage/test/unit/test_vacuum.js line 40
> function run_test()
more comments in general would be useful here.
This test also seems to be lacking in most of the cases we bail on. Can we please get some more test coverage on that?
on file: storage/test/unit/vacuumParticipant.js line 53
comment in this file saying what test file it is used for would be very
helpful
Lastly, can you pull the places stuff out into a different bug so we can move faster on this please?
(In reply to comment #38)
> on file: storage/public/mozIStorageVacuumParticipant.idl line 58
> > * Passing an invalid value will use default Storage page size.
>
> We should define that value in the IDL actually, so it's clear what the
> default is..
(In reply to comment #39)
>.
Why would we need to store it in three? If we store it in the IDL, in all the storage/ source files, we can just use the IDL constant.
(In reply to comment #40)
> Why would we need to store it in three? If we store it in the IDL, in all the
> storage/ source files, we can just use the IDL constant.
well it's a minor detail, but they will have to include mozIStorageParticipant.h even if they don't need it.
ok the page size problem is solved.
(In reply to comment #38)
>.
(In reply to comment #42)
>.
Oh right, I forgot about that...
Created attachment 474015 [details] [diff] [review]
patch v1.4
Fixed review comments and added a bunch of tests, removed Places changes (will file a follow-up).
Notice that to support wal unsetting and page size changes I had to run those pragmas synchronously. Trying to run them in an async batch was failing with SQLITE LOGIC ERROR 1, I guess because async statements were live on the db? So this does not have the statements array (btw, nsTArray<mozIstorageBaseStatement*> was working fine without having to alloc anything, just fyi).
(In reply to comment #44)
> Notice that to support wal unsetting and page size changes I had to run those
> pragmas synchronously. Trying to run them in an async batch was failing with
> SQLITE LOGIC ERROR 1, I guess because async statements were live on the db?
Likely because they were inside a transaction. You'd want to do more than one batch, I think, but I'll take a look at the code before we know for sure.
those statements are run only in the edge case that page size needs to be adjusted, that ideally happens just once per db in the worst case. So I'd not mind transactions too much for those.
Comment on attachment 474015 [details] [diff] [review]
patch v1.4
This is really close to being this. This is actually looking pretty great (way better than I ever expected us to be able to do), so thanks a ton for tackling this. For review comments with expandable context, please see.
on file: storage/public/mozIStorageVacuumParticipant.idl line 50
> // This value must stay in sync with the SQLITE_DEFAULT_PAGE_SIZE define in
> // /db/sqlite3/src/Makefile.in
would prefer to see a javadoc style comment here. It should also state what
the constant is and what it is used for.
on file: storage/public/mozIStorageVacuumParticipant.idl line 55
> * The expected page size for the database. VACUUM will try to correct the
> * page size based on this value.
should mention that this is bytes somewhere
on file: storage/public/mozIStorageVacuumParticipant.idl line 61
> * The VACUUM MAnager will try to restore WAL mode, but for this to
nit: typo: MAnager
Also, please put @note before each different note. Right now it looks like
there is only one long note here.
on file: storage/src/VacuumManager.cpp line 117
> Vacuumer::execute()
Assert that this is only on the main thread please.
on file: storage/src/VacuumManager.cpp line 129
> nsCOMPtr<nsIFile> databaseFile;
> mDBConn->GetDatabaseFile(getter_AddRefs(databaseFile));
databaseFile could be NULL if we have an in-memory database. We should 1)
assert about this, and 2) return so we don't crash.
Also, please add a test for this case.
on file: storage/src/VacuumManager.cpp line 161
> // Compare current page size with the expected one. VACUUM can change the
> // page size value if needed.
I think we actually want to do this check before we decide to not vacuum. In
the rare case where the page size is non-optimal but we have recently
vacuumed, I think we'd want to try to vacuum to correct the page size.
on file: storage/src/VacuumManager.cpp line 166
> NS_WARNING("Invalid page size requested for database, will use default ");
PR_LOG this please too.
nit: "Invalid page size requested for database, will use default for '%s'",
and this will have to be made into a string first. As it's written, it will
be printed on two different lines.
on file: storage/src/VacuumManager.cpp line 190
> {
> nsCOMPtr<mozIStorageStatement> stmt;
> rv = mDBConn->CreateStatement(NS_LITERAL_CSTRING(
> "PRAGMA journal_mode"
> ), getter_AddRefs(stmt));
> NS_ENSURE_SUCCESS(rv, false);
> PRBool hasResult;
> rv = stmt->ExecuteStep(&hasResult);
> NS_ENSURE_TRUE(NS_SUCCEEDED(rv) && hasResult, false);
>
> rv = stmt->GetUTF8String(0, mOriginalJournalMode);
> NS_ENSURE_SUCCESS(rv, false);
> }
Why is this scoped? I suspect it is because you need to at least call Reset,
but I think it'd be more clear to not scope it and explicitly call Reset.
on file: storage/src/VacuumManager.cpp line 204
> if (mOriginalJournalMode.EqualsLiteral("wal")) {
> // Set journal to a backwards compatible one.
> rv = mDBConn->ExecuteSimpleSQL(NS_LITERAL_CSTRING(
> "PRAGMA journal_mode = TRUNCATE"));
> NS_ENSURE_SUCCESS(rv, false);
This statement is one I don't really want us to do on the main thread. Can we
do a one-off async one here?
on file: storage/src/VacuumManager.cpp line 213
> rv = mDBConn->ExecuteSimpleSQL(
> nsPrintfCString("PRAGMA page_size = %ld", expectedPageSize)
> );
While this one is fine to do asynchronously, I think it's best to preserver
ordering and dump it off to the background thread too.
If push comes to shove, we can create a simple runnable to do all this for us
and just run this whole code block like this. We can get the background
thread by casing the mozIStorageConnection to mozilla::storage::Connection and
then call getAsyncExecutionTarget on it. In fact, that is probably the way we
want to go for this.
on file: storage/src/VacuumManager.cpp line 286
> NS_IMETHODIMP
> Vacuumer::HandleResult(mozIStorageResultSet*)
> {
> return NS_OK;
> }
I think we want an NS_NOTREACHED here, right?
on file: storage/src/VacuumManager.cpp line 306
> // If mOriginalJournalMode is set to WAL, it was temporarily changed and it
> // should be restored. Note we don't set this string if the page size does
> // not need to be changed.
I think we should use a boolean to track if we need to update it or not.
Having this have two meanings can lead to bugs down the line that I'd like to
avoid.
on file: storage/src/VacuumManager.cpp line 309
> if (mOriginalJournalMode.EqualsLiteral("wal")) {
> nsresult rv = mDBConn->ExecuteSimpleSQL(NS_LITERAL_CSTRING(
> "PRAGMA journal_mode = WAL"));
> NS_WARN_IF_FALSE(NS_SUCCEEDED(rv), "Restoring WAL journal mode failed.");
Now we know that this is expensive to do based on your work in bug 573492.
This needs to be done async, and we should probably not say we are done yet
either via the observer service).
Created attachment 475359 [details] [diff] [review]
patch v1.5
made statements async, added memory database test (I'm not asserting but warning in this case because otherwise I could not test, it is an edge case though so that looks enough), fixed other comments.
Comment on attachment 475359 [details] [diff] [review]
patch v1.5
This ended up being a bit more thourough than my normal reviews. I guess not getting interrupted because I'm on a plane means I can think more about this stuff.
> NS_GENERIC_FACTORY_SINGLETON_CONSTRUCTOR(Service,
> Service::getSingleton)
> NS_GENERIC_FACTORY_CONSTRUCTOR(StatementWrapper)
>-
>+NS_GENERIC_FACTORY_SINGLETON_CONSTRUCTOR(VacuumManager,
>+ VacuumManager::GetSingleton)
nit: getSingleton like Service please.
>+/**
>+ * mozIStorageConnectionInfo allows to share components connection and related
>+ * information on it.
>+ */
nit: wording is awkward. Let's try this:
/**
* This interface contains the information that the Storage service needs to
* vacuum a database. This interface is created as a service through the
* category manager with the category "vacuum-participant". Please see
* [link to devmo wiki page] for more information.
*/
You can just create a stub page for this or fill it out and have sheppy look it over. Either way, we should totally have a link here because we want people to use this. :)
>+ /**
>+ * [snip] VACUUM will try to
>+ * correct the page size based on this value.
nit: "The vacuum manager will try to correct the page size during idle based on this value."
>+ * @note If the database is using WAL journal mode and the current page size
nit: "...using the WAL journal mode..."
>+ * is not the expected one, journal mode will be changed to TRUNCATE
nit: "...one, the journal mode..."
>+ * because WAL does not allow page size changes.
>+ * The VACUUM Manager will try to restore WAL mode, but for this to
nit: vacuum doesn't need to be all uppercase since we aren't writing actual SQL here
>+ * work reliably the participant must ensure to always reset statements.
probably a good idea to also say that the journal mode will remain as TRUNCATE if statements are not properly reset.
>+ * .
>+++ b/storage/src/VacuumManager.cpp
>+#include "mozIStorageConnection.h"
>+#include "mozStorageConnection.h"
only need mozStorageConnection here
>+#define PREF_VACUUM_BRANCH "storage.vacuum.last."
please add a comment here explaining what this is used for
>+// Time between subsequent VACUUM calls for a certain database.
>+#define VACUUM_INTERVAL_SECONDS 30 * 86400
also explain what this time is in a more human readable form. I can't really do that math in my head so quickly, and I suspect others can't either.
>+#include "prlog.h"
move this up with the other #includes please
>+ nsresult NotifyCompletion(bool aSucceeded);
nit: storage style guide says this should start with a lowercase letter since it's not a method on an idl.
>+class BaseCallback : public mozIStorageStatementCallback
So, I think you want to implement nsISupport stuff on this, and have all classes, including Vacuumer, to inherit from it. They all need the exact same QI, AddRef, and Release implementation, so there is no point in not having them all share the same implementation. I know this can get hairy to do with xpcom sometimes, but pretty sure nsRunnable has code you can look at for reference.
>+
>+
>+NS_IMETHODIMP
>+BaseCallback::HandleError(mozIStorageError* aError)
nit: you seem to have two lines of space between a bunch of methods which is weird. I don't think we do that elsewhere
>+////////////////////////////////////////////////////////////////////////////////
>+//// SilentCallback
>+
>+class SilentCallback : public BaseCallback
can you add some comments about what silent means here and what this is used for please?
>+ // We succeeded if both vacuum are WAL restore succeeded.
nit: "...vacuum and WAL restoration succeeded."
>+ // Get connection and check its validity.
nit: "Get the connection..."
>+ // Get database filename.
please elaborate why we need the filename here too please
>+ NS_ConvertUTF16toUTF8 mDBFilename(databaseFilename);
This does not do what you think it does here. This doesn't assign to this->mDBFilename, but rather it makes a new local variable that shadows this->mDBFilename. I think you want this instead:
mDBFilename = NS_ConvertUTF16toUTF8(databaseFilename);
You might need to use Assign though, so check the string guide (or ask someone) please.
>+ NS_ASSERTION(!mDBFilename.IsEmpty(), "Database filename cannot be empty");
move this assertion to the locations where mDBFilename is used please so we can catch bugs like above :)
>+ bool canOptimizePageSize = false;
do not need to assign here since we will return on error, or set a value.
>+ rv = stmt->ExecuteStep(&hasResult);
>+ NS_ENSURE_TRUE(NS_SUCCEEDED(rv) && hasResult, false);
Actually, split these into two different checks please. You cannot tell which one failed in the console.
>+ // Notify we are about to start VACUUMing. The participant can opt-out if it
nit: "Notify that we are..."
>+ // cannot handle a VACUUM at this time, then we'll move to the next one.
nit "...time, and then..."
>+ if (canOptimizePageSize) {
>+ // Check journal mode. WAL journaling does not allow VACUUM to change page
>+ // size, thus we have to temporary switch journal mode to TRUNCATE.
nit: "...to temporarily switch the journal..."
>+ if (journalMode.EqualsLiteral("wal")) {
>+ mRestoreWAL = true;
>+ // Set journal to a backwards compatible one.
nit: journal mode
>+ nsCOMPtr<mozIStoragePendingStatement> ps;
>+ stmt->ExecuteAsync(callback, getter_AddRefs(ps));
nit: (void) result you don't check
>+ nsCOMPtr<mozIStorageAsyncStatement> pageSizeStmt;
>+ rv = mDBConn->CreateAsyncStatement(nsPrintfCString(
>+ "PRAGMA page_size = %ld", expectedPageSize
>+ ), getter_AddRefs(pageSizeStmt));
I imagine you make this an async statement because you want to make sure it runs after the possible conversion of the journal mode, correct? If so, we should add a comment as a big warning saying that we should not run any more synchronous statements after we check for the journal mode.
>+ pageSizeStmt->ExecuteAsync(callback, getter_AddRefs(ps));
nit: (void) result you don't check
>+#ifdef PR_LOGGING
>+ {
>+ PRInt32 result;
>+ nsresult rv = aError->GetResult(&result);
>+ NS_ENSURE_SUCCESS(rv, rv);
>+ nsCAutoString message;
>+ rv = aError->GetMessage(message);
>+ NS_ENSURE_SUCCESS(rv, rv);
>+ PR_LOG(gStorageLog, PR_LOG_ERROR,
>+ ("VACUUM failed with error: %d '%s'", result, message.get()));
>+ PR_LOG(gStorageLog, PR_LOG_ERROR,
>+ ("Database was: '%s'", mDBFilename.get()));
I think this ends up being two different lines in the log file, which isn't ideal since you could have different threads logging possibly.
>+ // Handle errors now, it's important to notify participant before throwing.
>+ if (!stmt || !callback) {
>+ NotifyCompletion(false);
>+ return NS_ERROR_UNEXPECTED;
>+ }
note that throwing doesn't actually accomplish anything here.
>+VacuumManager*
>+VacuumManager::GetSingleton()
>+{
[snip]
>+}
egads trailing whitespace!
>+ //
>+NS_IMETHODIMP
>+VacuumManager::Observe(nsISupports *aSubject,
>+ const char *aTopic,
>+ const PRUnichar *aData)
I think this is actually the only place where you have the pointer style correct in this patch. We'll have a flag day after Firefox 4 ships to update the pointer style to that of the code-base style, but let's keep the module consistent for now please.
>+++ b/storage/src/VacuumManager.h
>+#ifndef VacuumManager_h_
>+#define VacuumManager_h_
I think we are supposed to do mozilla_storage_VacuumManager_h__ here too. Same with other header files you add.
>+ /**
>+ * Obtains the VacuumManager object.
>+ */
>+ static VacuumManager* GetSingleton();
>+
>+ /**
>+ * Initializes the VacuumManager object. Must be called just once.
>+ */
>+ nsresult Init();
nit: both of these should follow mozilla::storage::Service style (getSingleton, initialize)
>+++ b/storage/src/mozStorageConnection.h
>@@ -47,16 +47,19 @@
>
> #include "nsString.h"
> #include "nsDataHashtable.h"
> #include "mozIStorageProgressHandler.h"
> #include "SQLiteMutex.h"
> #include "mozIStorageConnection.h"
> #include "mozStorageService.h"
>
>+#include "mozIStorageVacuumParticipant.h"
>+#define DEFAULT_PAGE_SIZE mozIStorageVacuumParticipant::DEFAULT_PAGE_SIZE
Hmm, actually, this constant should probably be placed on mozIStorageConnection since we set it on open to this.
>+++ b/storage/test/unit/test_vacuum.js
>+/**
>+ * Returns a new nsIFile reference for a profile database.
>+ */
>+function new_file(name)
>+{
>+ let file = Services.dirsvc.get("ProfD", Ci.nsIFile);
>+ file.append(name + ".sqlite");
>+ return file;
>+}
I think, given what this does, it'd be more clear to be called new_db_file.
>+ // Change initial page size.
It is unclear why we do that for the test here, so please elaborate.
>+ else {
>+ // Set last VACUUM to a date in the past.
>+ Services.prefs.setIntPref("storage.vacuum.last.testVacuum.sqlite",
>+ parseInt(Date.now() / 1000 - 31 * 86400));
>+ (TESTS.shift())();
Would prefer to see this in a do_execute_soon so failure stacks are easier to follow and understand (and shorter).
>+const TESTS = [
>+
>+function test1()
would really prefer you to stick with the format of most other storage tests that have descriptive names of the test as the method name. See things like test_storage_connection.js for an example.
>+++ b/storage/test/unit/vacuumParticipant.js
>+function new_file(name)
ditto about the name. Also, missing the javadoc comments.
>+function getDatabase(aFile)
javadoc comments please
>+ else if (aData == "wal") {
>+ try {
>+ this._dbConn.close();
>+ } catch (e) {}
nit: newline before catch (you did this elsewhere, just not in this method). Also, catch(e) I think.
r=sdwilsh with those changes. This will kick ass.
(In reply to comment #49)
> Comment on attachment 475359 [details] [diff] [review]
> >+ * .
onEndVacuum passes a succeeded bool to the participant
(In reply to comment #49)
> >+ //
I thought about that, but I don't think that works out of the box. For it to work, idle service should have a category cache and should init the participants.
It would make MUCH sense for a lot of other services too, but has to be implemented in a separate bug.
filed bug 598966 to add a magic idle-daily category.
(In reply to comment #50)
> onEndVacuum passes a succeeded bool to the participant
Oh right! Couldn't we write test cases for a few more situations where we bail out then?
(In reply to comment #53)
> (In reply to comment #50)
> > onEndVacuum passes a succeeded bool to the participant
> Oh right! Couldn't we write test cases for a few more situations where we bail
> out then?
it's tricky, I can't cause a vacuum failure on my will, I think. Will think about that some more.
So far I've addressed everything but:
- NSISUPPORTS: need to check inheritance with more attention because if we end up using the underlying class implementation of addRef we will leak. My first implementation was using a single impl and NS_ISUPPORTS_INHERITED but everything was leaking.
- adding a test for succeeded (as I said could be tricky, will let you know)
- idle-daily category (will need bug 598966)
Created attachment 477955 [details] [diff] [review]
patch v1.6
checkpoint to save my work and eventually for further comments.
idl should be finalized here for SR (moved the const to mozIStorageConnection).
See comment above for what is left to do.
(In reply to comment #54)
> - NSISUPPORTS: need to check inheritance with more attention because if we end
> up using the underlying class implementation of addRef we will leak. My first
> implementation was using a single impl and NS_ISUPPORTS_INHERITED but
> everything was leaking.
You shouldn't have to use that at all since they all QI to the same thing. Just don't implement nsISupports on the child interfaces, and you'll be OK. Example:
nsRunnable implements it's QI and AddRef/Release here:
And then we inherit from it in storage here:
...and we never declare anything about nsISupports because the inheritance takes care of it for us.
Created attachment 478058 [details] [diff] [review]
patch v1.7
Addressed all comments so far, in this version:
- nsISupports inheritance is fixed, and I was able to kill SilentCallback class in favor of BaseCallback (thanks for pointing me to nsRunnable)
- added a test for vacuum failure, unfortunately it is commented out due to bug 599098, but we can enable it later, once that bug is fixed.
- cleanup DEFAULT_PAGE_SIZE, some location was still using the old position in idls
Todo:
- bug 598966 - Add idle-daily category (Could be a followup ideally, but if I can fix that before, I'll be happy)
bug 598966 has a patch (waiting for review) so i'll attach a new part to use it.
Comment on attachment 478058 [details] [diff] [review]
patch v1.7
Looks ok, sorry for the long review -- also please don't mark the r+'d versions of patches as obsolete :-)
> Looks ok, sorry for the long review -- also please don't mark the r+'d versions
> of patches as obsolete :-)
sorry, unfortunately we don't have anymore the awesome jetpack from ehsan that was showing reviewed patches even if obsolete (I actually requested him to add that and it was awesome), I agree that default bugzilla behavior is not so nice.
Thanks for the sr.
Created attachment 482521 [details] [diff] [review]
Part 2: use idle-daily category for startup
landing this will require bug 602871, to avoid running vacuum for each xpcshell test.
Comment on attachment 482521 [details] [diff] [review]
Part 2: use idle-daily category for startup
> static const mozilla::Module::CategoryEntry kStorageCategories[] = {
>- { "profile-after-change", "MozStorage Vacuum Manager", VACUUMMANAGER_CONTRACTID },
>+ { "idle-daily", "MozStorage Vacuum Manager", VACUUMMANAGER_CONTRACTID },
> { NULL }
> };
Can you please format this more like kStorageModule below it. Missed that before...
r=sdwilsh
part 1:
part 2:
Marco, to ease the documentor's job, can you please summarize exactly what was added/changed/removed, any configurable bits, and any behavior changes?
it's mostly a newly added idl called mozIStorageVacuumParticipant.idl (each method is well documented in the interface, as well as it has a brief intro), components can implement this interface and register through their manifest to the "vacuum-participant" category.
Documentation updated:
The article about the new interface is here:
The URL specified in the IDL works; it redirects to the actual location of the document.
The article needs details about how to use it, though. I'll be working on that eventually, although it would be helpful if someone else could put something in there, as it looks like our documentation for the Category Manager and how to use manifests for stuff like this is not very good (if it's there at all; I sure couldn't find it).
Thanks for ther awesome work!
Do you have suggestions on where to put that additional documentation?
I'd just put it, for now, at the top of the page here:
Where there's text that says "Add more details here." If it's substantial enough, we'll move it to a separate how-to page. | https://bugzilla.mozilla.org/show_bug.cgi?id=541373 | CC-MAIN-2016-40 | refinedweb | 7,621 | 55.95 |
Hide Forgot
Description of problem:
firstboot seems to require a graphics display: on text consoles,
it aborts with the backtrace show below. This is on x86_64 (dl380
and dl785) but it's probably hardware-independent.
Version-Release number of selected component (if applicable):
How reproducible:
Steps to Reproduce:
1. Install RHEL6.0snap2 and specify "text console=XXX"
2. Watch the first boot.
3.
Actual results:
...
Traceback (most recent call last):
File "/usr/sbin/firstboot", line 24, in <module>
from meh.ui.gui import GraphicalIntf
File "/usr/lib/python2.6/site-packages/meh/ui/gui.py", line 21,
Welcome to Red Hat Enterprise Linux Server
Press 'I' to enter interactive startup.
...
Expected results:
No error.5077 *** | https://bugzilla.redhat.com/show_bug.cgi?format=multiple&id=591276 | CC-MAIN-2019-18 | refinedweb | 115 | 52.15 |
I'm very new to ruby and intellij so this may well be something trivial. Whenever I attempt to run unit tests I get the following error every time I try to use the class I'm trying to test:
NameError: uninitialized constant FooTest::Foo
C:/projects/UnitTestingExample/foo_test.rb:6:in `test_somestuff'
My test file looks like this:
require 'minitest/unit'
require 'minitest/autorun'
class FooTest < MiniTest::Unit::TestCase
def test_somestuff
a = Foo.new 'bar'
end
end
and my file structure looks like this:
<project root>
foo.rb
test_foo.rb
Any idea what could be the cause of the problem? Literally all I've done is create a project, create a ruby class, and create a test class, then make it use minitest.
Hi,
perhaps you need to require foo?
Regards, Oleg.
That gives this error:
C:/projects/UnitTestingExample/foo_test.rb:3:in `<top (required)>': undefined local variable or method `foo' for main:Object (NameError)
from -e:1:in `load'
from -e:1:in `<main>'
I meant "require 'foo'" not "require foo"
Regards, Oleg.
New error:
C:/Ruby193/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_require.rb:54:in `require': cannot load such file -- foo (LoadError)
from C:/Ruby193/lib/ruby/site_ruby/1.9.1/rubygems/core_ext/kernel_require.rb:54:in `require'
from C:/projects/UnitTestingExample/foo_test.rb:3:in `<top (required)>'
from -e:1:in `load'
from -e:1:in `<main>'
Is the test works correctly when you run it in command line (ruby foo_test.rb)?
If not please provide the output, if yes could you please provide screenshot of settings of the run configuration RubyMine created for you.
Regards, Oleg.
I figured it out. For normal ruby stuff (as opposed to rails) you need to set the path in your requires. It would be a nice feature to be able to generate the test classes automagically via a right click menu or something so that they automatically handle the path stuff for you. | https://intellij-support.jetbrains.com/hc/en-us/community/posts/206061359-Test-class-not-finding-main-class?page=1 | CC-MAIN-2020-10 | refinedweb | 327 | 64.3 |
I'm trying to get some results from UniProt, which is a protein database (details are not important). I'm trying to use some script that translates from one kind of ID to another. I was able to do this manually on the browser, but could not do it in Python.
In there are some sample scripts. I tried the Perl one and it seems to work, so the problem is my Python attempts. The (working) script is:
## tool_example.pl ##
use strict;
use warnings;
use LWP::UserAgent;
my $base = '';
my $tool = 'mapping';
my $params = {
from => 'ACC', to => 'P_REFSEQ_AC', format => 'tab',
query => 'P13368 P20806 Q9UM73 P97793 Q17192'
};
my $agent = LWP::UserAgent->new;
push @{$agent->requests_redirectable}, 'POST';
print STDERR "Submitting...\n";
my $response = $agent->post("$base/$tool/", $params);
while (my $wait = $response->header('Retry-After')) {
print STDERR "Waiting ($wait)...\n";
sleep $wait;
print STDERR "Checking...\n";
$response = $agent->get($response->base);
}
$response->is_success ?
print $response->content :
die 'Failed, got ' . $response->status_line .
' for ' . $response->request->uri . "\n";
question #1:
This can be done using python's urllibs:
import urllib, urllib2 import time import sys query = ' '.join(sys.argv) # encode params as a list of 2-tuples params = ( ('from','ACC'), ('to', 'P_REFSEQ_AC'), ('format','tab'), ('query', query)) # url encode them data = urllib.urlencode(params) url = '' # fetch the data try: foo = urllib2.urlopen(url, data) except urllib2.HttpError, e: if e.code == 503: # blah blah get the value of the header... wait_time = int(e.hdrs.get('Retry-after', 0)) print 'Sleeping %i seconds...' % (wait_time,) time.sleep(wait_time) foo = urllib2.urlopen(url, data) # foo is a file-like object, do with it what you will. foo.read() | https://codedump.io/share/RMgQ2Nx7rXIc/1/how-can-i-talk-to-uniprot-over-http-in-python | CC-MAIN-2017-34 | refinedweb | 270 | 60.11 |
- Download the source files for this tutorial
In part one of this tutorial we made a task list site to manage task lists as well as the add, edit and delete tasks in these lists. In this part we will add some additional functionality to our application.
We’ll start with a simple change on marking the task as complete by setting a completion date. Add a new field and mapping annotation to the list of properties in the Task entity (src/DotNet/TaskListBundle/Entity/Task.php) to store the completion date:
/** @ORM\Column(type="datetime", nullable=true) */ private $dateCompleted;
At the command line, run the following console command from the root directory of the application to generate getter and setter methods:
php app/console doctrine:generate:entities DotNetTaskListBundle:Task
We could just add this functionality to the updateAction of the TaskController. However, it would be preferable to keep our controllers as thin as possible. Do this in the entity using the Doctrine lifecycle events, which get fired at various points in the process of persisting an entity. These ensure the business rules are always run however the update to the entity is triggered.
To update this on completion we use the PreUpdate event, fired when an already persisted entity has been updated before the changes are sent to the database. In the Task entity class, add the following method and annotation:
/** @ORM\PreUpdate */ public function updateDateCompleted() { if ($this->completed) { $this->dateCompleted = new \DateTime(); } }
The annotation tells Doctrine that this method should be run when the PreUpdate event occurs. The Doctrine also needs telling that the entity has one of these lifecycle callbacks by adding a further annotation to the class level annotations (in other words, below @ORM\Entity):
@ORM\HasLifecycleCallbacks()
Stop the task being edited once completed as well as displaying the completed date in the template. In src/DotNet/TaskListBundle/Resources/ views/TaskList/show.html.twig change the line showing the completed cell in the table to:
<td>{% if task . completed % }{{t ask .date Completed|date ('H:i:s d/m/Y') }}{% else %}no{% endif %}</td>
Change the line below that shows the edit link to:
<td>{% if not task.completed %}{<a href="{{ path ('task _edit', { 'id': task.id }) }}">edit</a>{% endif %}</td>
This will only get rid of the link though; we really need to stop the edit form page being displayed if you navigate to it directly by entering its URL in the browser’s address bar.
In the TaskController (src/DotNet/TaskListBundle/Controller/ TaskController.php) for the editAction and updateAction methods, there is a lready a check that the entity exists. We can add to this to make sure that the task is not already completed:
if (!$entity || $entity->getCompleted()) { throw $this->createNotFoundException('Unable to find Task entity.'); }
Now open the app in your browser, add a task and mark it complete. You’ll see the current date is shown in the completed column.
As well as marking the task complete we want to send an email notification out when the task is completed. To do this, use two of the features of Symfony2 that help you to build flexible and powerful applications: namely, the service container and the event dispatcher.
The service container manages the creation of objects so you can compose complicated objects that have multiple dependencies without having to write the code to do this whenever you want to use them. We will create our class for sending the email notification as a service and combine it with the services it uses itself to produce and send the email.
The event dispatcher allows you to decouple the code. We’ll use it to prevent tying the sending of the email into our controller and see how we could easily add or remove the other things that happen when the Task is updated. This is similar to the Doctrine event used to add the completion date. However, this time we will raise the event ourselves.
Create an event class to hold the Task so we have access to it in the listener. Add an Event directory to the TaskListBundle. Inside, create a TaskEvent.php file with the following code in it:
<?php namespace DotNet\TaskListBundle\Event; use Symfony\Component\EventDispatcher\Event; class TaskEvent extends Event { protected $task; public function __construct($entity) { $this->task = $entity; } public function getTask() { return $this->task; } }
Now add dispatching the event to the TaskController. Add a use statement to the others at the top of the file and import the event we just created:
use DotNet\TaskListBundle\Event\TaskEvent;
Then, in the updateAction after the entity manager is flushed
($em->flush();), add this line:
$this->get('event_dispatcher')->dispatch('task.updated', new TaskEvent($entity));
This uses the event dispatcher service to dispatch an instance of our event with the Task object in it. The first argument is the name of the event, which can be any string you want – the Symfony2 convention is to use dots as separators in the event names. You should now be able to run the application again.
The event will be fired if you update a Task. Events that are fired are shown in the profiler. But, as we redirect the browser to a different page after firing the event, it’s not visible. We can configure the redirects to be intercepted so we get a chance to see the profiler before the redirection takes place. In app/config/config_dev.yml you will see a line under the web_ profiler section; change it to:
intercept_redirects: true
This config change will only affect the dev environment. You wouldn’t see redirects being interrupted if you deploy the app in the production environment, which is done by using the app.php front controller instead of app_dev.php.
You’ll now be able to see the event was fired. You’ll also be able to see several events internal to the framework in the profiler by opening it from the toolbar at the bottom of the page and viewing the events section.
At the moment, nothing different happens as nothing is listening for the event. Create a Listener directory inside the Event directory you created before and add a TaskEmailler.php file to it with the following in it:
<?php namespace DotNet\TaskListBundle\Event\Listener; use DotNet\TaskListBundle\Event\TaskEvent; class TaskEmailler { protected $mailer; protected $templating; protected $emailFrom; protected $emailTo; public function __construct(TYPE HINT HERE? $mailer, $templating, $emailFrom, $emailTo) { $this->mailer = $mailer; $this->templating = $templating; $this->emailFrom = $emailFrom; $this->emailTo = $emailTo; } }
Here we’re just adding our class’s dependencies via its constructor. Use the mailer service to send the email and the templating service to render the Twig template for the email body. By passing them in this way we don’t have to worry about how the mailer and templating engine are created or configured; we can instead concentrate on how to use them.
The email address we want to send the notification to, and the email address it’s from, is also passed in. These are simple strings rather than objects. This way we can avoid hard coding them in our class. You’ll see how these services and parameters get into the objects instantiated from our class when we configure it as a service. First, add a method to send the email:
public function postUpdate(TaskEvent $args) { $task = $args->getTask(); if (!$task->getCompleted()) { return; } $message = \Swift_Message::newInstance() ->setSubject('Task completed') ->setFrom($this->emailFrom) ->setTo($this->emailTo) ->setBody($this->templating->render( 'DotNetTaskListBundle:Task:email.txt.twig', array('task' => $task)) ); $this->mailer->send($message); }
So, if the task is set to completed we create an new email object, set its subject and set the to and from addresses using the parameters passed in. Use the template service to render a template to create the email body. Once it’s created, pass it to the mailer service, which deals with sending the email. Mailer and templating are two of the services that are already registered with the service container by the framework.
In the services.xml file in the bundle’s Resource/config directory, replace the commented out lines with the following, which changes the email addresses to something that can receive email:
<services> <service id="dotnet.listener.task_email" class=”DotNet\TaskListBundle\Event\Listener\TaskEmailer”> <argument type="service" id="mailer"/> <argument type="service" id="templating"/> <argument>tasks@example.com</argument> <argument>rmiller@example.com</argument> <tag name="kernel.event_listener" event="task.updated" method="postUpdate" /> </service> </services>
The service element has an id for the service. Tell it the class we want this service to be. Use the argument elements to inject in the mailer and templating services along with the email addresses.
The final thing is tagging the service as a listener for our task.updated event and specifying the method that listens to it. This method will now get called whenever the event is dispatched.
The last thing we need to do is add that template (src/DotNet/ TaskListBundle/Resources/views/Task/email.txt.twig) to render the email body:
The {{ task.name }} task was completed.
Now if you set a task to complete in the application you’ll now receive an email notification.
For further ways to add functionality to your application, the documentation here is a great source of information about Symfony2.
Words: Richard Miller
This article originally appeared in .net magazine issue 239
Liked this? Read these!
- How to use the PHP command line
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Any questions? Ask away in the comments! | https://www.creativebloq.com/web-design/build-your-own-task-list-manager-php-part-2-11135188 | CC-MAIN-2020-40 | refinedweb | 1,600 | 54.12 |
C++ Program to Shift Every Element of An Array to Circularly Right
Hello Learners,
In this particular article, we are going to learn how to Circularly Right Shift Every Element of an Array in C++. The array can be user-defined or as well as by default given in the program. While and for loops are going to be used but Recursion is an alternative method to implement in this program.
Let us see an example for better understanding:
array[]={1 2 3 4 5}
here, we have to shift each and every element to right and the rightmost element will be the first element in the output screen.
Output screen will look like this:
array[]={5 1 2 3 4}
How to Circularly Right Shift Each and Every Element of an Array Using C++
let us create an array named arr[n]. Here, n is the size of the array which should be an integer. we are considering here only 5 elements but any other size is also accepted. It’s up to the user. Only you need to mention that in your program by just asking the user to enter the size of your array. Now here, We will use a while loop to circularly shift elements and for loop to display and enter the array in this program. This is called an iterative approach. Firstly, we will put the last element in a temporary variable as it has to be the first element of the array. Then, we’ll shift the rest elements to right by using variables i and j. Lastly, we will place the value stored in the temporary variable at the first position of that array. Our last task will be printing the elements of the array.
Underneath is the C++ codes to solve this problem:
#include<iostream> using namespace std; int main() { int arr[5],i; cout<<"Enter elements of array: "; for(i=0;i<5;i++) cin>>arr[i]; cout<<"Your array: "; for(i=0;i<5;i++) cout<<arr[i]<<" "; i=4; int j=i-1; int temp=arr[4]; while(j>=0 && i>=0) { arr[i]=arr[j]; j--; i--; } arr[i]=temp; cout<<"\nShifted array: "; for(i=0;i<5;i++) cout<<arr[i]<<" "; return 0; }
Here, variable i is initialized to 4 which is the last index of the given array. So, variable i will work from index 4 to 1, and variable j is initialized to (i-1) which means at first it will be holding the value 3. After this, the element at index 3 will get swapped with the element at index 4. Then, i and j both will get decremented by 1 till it becomes equal to zero. Following this, every time each element will get shifted to the right. Lastly, the value of the temporary element will be placed at the first place of the array as the current index of i will be zero.
Let us see the output now:
Enter elements of aaray: 10 20 30 40 50 Your array: 10 20 30 40 50 Shifted array: 50 10 20 30 40
Some more Array Questions:
Maximum & Minimum element of an array using C++
In this way, you can circularly right shift elements of an array. I hope it was easy enough to understand. If you have any doubt, feel free to ask in the comment section.
Thank you!
Regards,
Isha Rani Prasad
Codespeedy Tech Pvt. Ltd. | https://www.codespeedy.com/c-program-to-shift-every-element-of-an-array-to-circularly-right/ | CC-MAIN-2021-17 | refinedweb | 576 | 66.88 |
The layers and pieces of Cake
When you don’t know the details behind a technology, it’s easy to dismiss it as magic, but if you dare to look behind the curtain — it might not be that complicated or foreign to what you already know.
In this blog post, I’ll go through some of the pieces that make up the open source build orchestration tool Cake.
I’ll show you how you can reuse pieces of Cake with different environments and even languages, I’ll go into detail on some parts and glance over others.
If there’s any part you would want me to go into more detail with please let me now! I will provide links to the examples and resources at the end of this blog post.
“It’s just C# and .Net”
This is a statement I have often made as Cake scripts provide a superset of C# — which means anything you can do in C# you can do Cake. The Cake DSL via its aliases merely provide a shortcut to make APIs and tools easier to consume, but you can always opt to like “regular” code reference assemblies, write methods and classes.
An example of this could be working with JSON, in your console or MVC app it’s likely that you would use JSON.Net to serialize/deserialize your JSON from/to .NET objects and doing the same with a Cake script doesn’t differ much from plain vanilla C#
Basically, only difference is the
#addinpreprocessor, which fetches and references an assembly from NuGet and the lack of need to wrap in the code in a namespace/class/method.
Being “just” C# and .NET truly means that you’ll always have the safety net of .NET, C# and the vast number of resources available for those pieces of technology.
The pieces of Cake
Cake is distributed in two flavors, one for the full classic .NET which also works with Mono and a version for .NET Core — the new cross platform framework/runtime from Microsoft.
The most common way to obtain the Cake tool is via the
Cakeand
Cake.CoreCLRNuGet packages (Cake is also available via Chocolatey, Homebrew, GitHub and official docker containers are on their way).
The NuGet packages contain all dependencies needed to execute under respective runtime, but the “Magic” is in three assemblies and a console application
Cake.exe / Cake.dll — “The Tool”
To name a few things it handles
- Compilation of scripts
- Argument parsing
- Console logging
- Composition of modules/assemblies
- Basically, it’s what glues everything together and provides the “Cake experience”
Cake.Core — “The heart”
Provides things like
- Core abstractions/interfaces/attributes used by Cake Tool/Addins/Modules
(this is the only assembly needed to reference when creating a Cake addin/module)
- DSL Parsing and transpiling/codegen to C# that Roslyn understands and can compile
- Base tool implementation (tool resolution, execution, settings etc.)
- Cake Task runtime (task runner/dependency graph/setup & teardown etc.)
Cake.Common — “The doer”
This assembly provides almost 400 convenient aliases/extension methods for things like
- Tools (MSBuild, NuGet, .NET Core CLI, code signing, etc.)
- APIs (compression, project file parsing, text templating, HTTP, etc.)
- Build system support (AppVeyor, VSTS, Jenkins, TeamCity, MyGet, etc.)
Cake.NuGet — “The Fetcher”
Cake module that enables fetching dependencies from NuGet for i.e. preprocessor directives like
#addin,
#tooland
#load .
Cake composition — “It’s just C# and .Net part deux”
The assemblies
Cake.Core,
Cake.Common and
Cake.NuGet are all available up on NuGet.org targeting both .NET Full/Desktop and .NET Core.
This means you can reference and leverage parts/most of the work and effort that’s been put into Cake with almost any .NET application, environment or platform — it’s just standard C# code and assemblies!
That said Cake relies heavily on dependency injection and has over time been refactored into custom modules — so how it all fits together can be a bit daunting for someone that’s new to the project. A rough basic example of doing this using an Inversion of Control container like AutoFac could look something like this:
As the observant might see from the comment there’s a few cases where the implementation currently resides in
Cake.exe/Cake.dll (this might be something we’ll look at refactoring in the future), the interfaces they implement exist in Core so you can implement and provide your own implementation or depending on what parts of Cake you reuse you might not need them (for unit testing we provide Cake.Testing which provides fake context and file system, environment abstractions for tool testing, etc. Unit testing Cake addins / modules might be a good topic for another blog post — please let me know if you reckon that’s the case).
Proof of concept custom script host
So, to do your own custom host for your own “build script” implementation, you currently need to implement a few interfaces:
ICakeArguments,
ICakeConfiguration,
ICakeLog,
ICakeReportPrinter and
IScriptHost , because these implementations as mentioned earlier currently resides in
Cake.exe/Cake.dll, but all other are available in
Cake.Core ready for reuse in any .NET project.
To demonstrate this, I’ve created the “Proof of concept, in no way official, don’t use in production, just to see how the sausage is made, etc.” assembly called
Cake.Bridge, compiled for both .NET and .NET Core, which means it could be used most places .NET is available today (binary is up on NuGet and source on GitHub, I’ll provide links to all resources at end of this post).
Cake.Bridge provides a static
CakeBridgeclass which provides easy access to working with the Cake task runner and the
ICakeContext (which is what all Cake aliases/methods extend), created with the goal to demonstrate an easy way to reuse Cake assemblies from any .NET language and not only with C# which is what Cake supports out of the box.
What you won’t get is anything the Cake DSL provides and no addin nor module support.
To illustrate this I’ve authored a few code snippets on how using Cake from a few different .NET languages using the
Cake.Bridgeassembly, disclaimer the code snippets are quick and rough proof of concepts to mostly prove it can be done and obviously more refinement needs to be done for them to be more idiomatically correct.
There often exist more native, prominent and widely used build systems already.
PowerShell
Even if perhaps mainly the sysadmin language of choice — PowerShell still is a .NET based language and its ability to utilize .NET makes it a very powerful scripting language as anything not provided native by the language often can be solved by reaching out to the framework it’s running on. It also means that you can use Cake from it:
Visual Basic
You can’t talk about .NET languages without mentioning Visual Basic and now when it’s also joining the .NET Core party too it’s getting up to date with the times. And obviously you can Bake with Cake using some Basic (there’s no VB.NET interactive console that I know of so I created a simple VB.NET Core console app)
F#
F# is a .NET language which makes it fully possible to use Cake with F#.
Full disclaimer though, as I’m not very proficient with the F# language and wanted something that somewhat looked like F# I called on the help and assistance of my friend Mårten Rånge to do a quick port from C# to F# and this was the result:
Cake / C#
For reference below is the script that was used for inspiration when porting to other languages/runtimes, there’s a little less bootstrapping involved but besides that they’re very similar:
Conclusion
Even though there might seem to be some Magic around Cake and it’s DSL it’s mostly just .NET and C#, having skills in those areas — are skills you can use with Cake scripts or when using Cake assemblies in some other way. If you have a different need from what the official supported way offers, you could still have a piece of the Cake.
Resources
Cake.Bridge
PowerShell proof of concept
Visual Basic proof of concept
F# interactive script proof of concept
C# interactive proof of concept
Cake
- Website:
- GitHub:
- NuGet: | https://hackernoon.com/dispelling-the-magic-6dc0fdfe476c | CC-MAIN-2019-39 | refinedweb | 1,390 | 61.16 |
10 January 2012 17:32 [Source: ICIS news]
LONDON (ICIS)--SGL Carbon has sold its stake in a joint venture that manufactures rotor blades for offshore wind power turbines, the Germany-based producer of carbon fibre and composites said on Tuesday.
SGL Carbon said it sold its 49% stake in Bremerhaven-based PowerBlades to partner REpower for an undisclosed sum.
PowerBlades was founded in 2007, with REpower holding 51% and SGL’s subsidiary SGL Rotec holding 49%.
SGL said the joint venture had been a “good opportunity” for both SGL Rotec and REpower to advance their expertise in the production of offshore wind power blades.
However, Norbert Muller, managing director of SGL Rotec, said “now the time has come” for PowerBlades to further build out its business under the direction of REpower.
REpower is part of India's Suzlon, one of the world’s leading manufacturers of onshore and offshore wind turbines.
SGL Rotec, for its part, will focus on its production site in ?xml:namespace>
For more on SGL Carbon | http://www.icis.com/Articles/2012/01/10/9522354/germanys-sgl-carbon-exits-wind-power-blades-joint-venture.html | CC-MAIN-2014-35 | refinedweb | 171 | 59.23 |
A group blog from members of the VB team
Visual Basic Developer Center | How-Do-I Videos | Power Packs | Code Samples | Team Interviews | Team Webcasts
By Amanda Silver. = ""
2. Accessing elements with namespaces: Once an Xml namespace was imported, you can use qualified identifiers to access elements with namespaces. The qualified identifiers are in the form of 'Xml Namespace Alias' + '::' + 'Element = ""
Module Module1
Sub Main()
Dim book = _
<Book xmlns="">
<Title>Learning Programming Using Visual Basic</Title>
</Book>
Console.WriteLine( CStr( book.ns::Title(0) ) )
End Sub
End Module!
If you would like to receive an email when updates are made to this post, please register here
RSS | http://blogs.msdn.com/vbteam/archive/2006/01/23/VB_LINQ_CTP_Now_live_on_MSDN.aspx | crawl-002 | refinedweb | 108 | 54.52 |
This is the fourth post in a multi-part series about how you can perform complex streaming analytics using Apache Spark.
Continuous applications often require near real-time decisions on real-time aggregated statistics—such as health of and readings from IoT devices or detecting anomalous behavior. In this blog, we will explore how easily streaming aggregations can be expressed in Structured Streaming, and how naturally late, and out-of-order data is handled.
Streaming Aggregations
Structured Streaming allows users to express the same streaming query as a batch query, and the Spark SQL engine incrementalizes the query and executes on streaming data. For example, suppose you have a streaming DataFrame having events with signal strength from IoT devices, and you want to calculate the running average signal strength for each device, then you would write the following Python code:
# DataFrame w/ schema [eventTime: timestamp, deviceId: string, signal: bigint] eventsDF = ... avgSignalDF = eventsDF.groupBy("deviceId").avg("signal")
This code is no different if eventsDF was a DataFrame on static data. However, in this case, the average will be continuously updated as new events arrive. You choose different output modes for writing the updated averages to external systems like file systems and databases. Furthermore, you can also implement custom aggregations using Spark’s user-defined aggregation function (UDAFs).
Aggregations on Windows over Event-Time
In many cases, rather than running aggregations over the whole stream, you want aggregations over data bucketed by time windows (say, every 5 minutes or every hour). In our earlier example, it’s insightful to see what is the average signal strength in last 5 minutes in case if the devices have started to behave anomalously. Also, this 5 minute window should be based on the timestamp embedded in the data (aka. event-time) and not on the time it is being processed (aka. processing-time).
Earlier Spark Streaming DStream APIs made it hard to express such event-time windows as the API was designed solely for processing-time windows (that is, windows on the time the data arrived in Spark). In Structured Streaming, expressing such windows on event-time is simply performing a special grouping using the
window() function. For example, counts over 5 minute tumbling (non-overlapping) windows on the eventTime column in the event is as following.
from pyspark.sql.functions import * windowedAvgSignalDF = \ eventsDF \ .groupBy(window("eventTime", "5 minute")) \ .count()
In the above query, every record is going to be assigned to a 5 minute tumbling window as illustrated below.
Each window is a group for which running counts are calculated. You can also define overlapping windows by specifying both the window length and the sliding interval. For example:
from pyspark.sql.functions import * windowedAvgSignalDF = \ eventsDF \ .groupBy(window("eventTime", "10 minutes", "5 minutes")) \ .count()
In the above query, every record will be assigned to multiple overlapping windows as illustrated below.
This grouping strategy automatically handles late and out-of-order data — the late event would just update older window groups instead of the latest ones. Here is an end-to-end illustration of a query that is grouped by both the
deviceId and the overlapping windows. The illustration below shows how the final result of a query changes after new data is processed with 5 minute triggers when you are grouping by both
deviceId and sliding windows (for brevity, the “signal” field is omitted).
windowedCountsDF = \ eventsDF \ .groupBy( "deviceId", window("eventTime", "10 minutes", "5 minutes")) \ .count()
Note how the late, out-of-order record [12:04, dev2] updated an old window’s count.
Stateful Incremental Execution
While executing any streaming aggregation query, the Spark SQL engine internally maintains the intermediate aggregations as fault-tolerant state. This state is structured as key-value pairs, where the key is the group, and the value is the intermediate aggregation. These pairs are stored in an in-memory, versioned, key-value “state store” in the Spark executors that is checkpointed using write ahead logs in an HDFS-compatible file system (in the configured checkpoint location). At every trigger, the state is read and updated in the state store, and all updates are saved to the write ahead log. In case of any failure, the correct version of the state is restored from checkpoint information, and the query proceeds from the point it failed. Together with replayable sources, and idempotent sinks, Structured Streaming ensures exactly-once guarantees for stateful stream processing.
This fault-tolerant state management naturally incurs some processing overheads. To keep these overheads bounded within acceptable limits, the size of the state data should not grow indefinitely. However, with sliding windows, the number of windows/groups will grow indefinitely, and so can the size of state (proportional to the number of groups). To bound the state size, we have to be able to drop old aggregates that are not going to be updated any more, for example seven day old averages. We achieve this using watermarking.
Watermarking to Limit State while Handling Late Data
As mentioned before, the arrival of late data can result in updates to older windows. This complicates the process of defining which old aggregates are not going to be updated and therefore can be dropped from the state store to limit the state size. In Apache Spark 2.1, we have introduced watermarking that enables automatic dropping of old state data.
Watermark is a moving threshold in event-time that trails behind the maximum event-time seen by the query in the processed data. The trailing gap defines how long we will wait for late data to arrive. By knowing the point at which no more data will arrive for a given group, we can limit the total amount of state that we need to maintain for a query. For example, suppose the configured maximum lateness is 10 minutes. That means the events that are up to 10 minutes late will be allowed to aggregate. And if the maximum observed event time is 12:33, then all the future events with event-time older than 12:23 will be considered as “too late” and dropped. Additionally, all the state for windows older than 12:23 will be cleared. You can set this parameter based on the requirements of your application — larger values of this parameter allows data to arrive later but at the cost of increased state size, that is, memory usage and vice versa.
Here is the earlier example but with watermarking.
windowedCountsDF = \ eventsDF \ .withWatermark("eventTime", "10 minutes") \ .groupBy( "deviceId", window("eventTime", "10 minutes", "5 minutes")) \ .count()
When this query is executed, Spark SQL will automatically keep track of the maximum observed value of the eventTime column, update the watermark and clear old state. This is illustrated below.
Note the two events that arrive between the processing-times 12:20 and 12:25. The watermark is used to differentiate between the late and the “too-late” events and treat them accordingly.
Conclusion
In short, I covered Structured Streaming’s windowing strategy to handle key streaming aggregations: windows over event-time and late and out-of-order data. Using this windowing strategy allows Structured Streaming engine to implement watermarking, in which late data can be discarded. As a result of this design, we can manage the size of the state-store.
In the upcoming version of Apache Spark 2.2, we have added more advanced stateful stream processing operations to streaming DataFrames/Datasets. Stay tuned to this blog series for more information. If you want to learn more about Structured Streaming, read our previous posts in the series.
-
To try Structured Streaming in Apache Spark 2.0, try Databricks today. | https://databricks.com/blog/2017/05/08/event-time-aggregation-watermarking-apache-sparks-structured-streaming.html | CC-MAIN-2021-21 | refinedweb | 1,265 | 53.81 |
Here is the Windows version,
From Softpedia.com
Check out: Intuition 1.6, the latest Mac OSX version of MTML
Here is the Mac version,
From Softpedia.com
MTML, Meaningful Text Markup Language, as an experiment involving text,
computers, readable semantic association, relational text gathering, and the
pursuit of a likely human interface.
Mark Brownell
Garage-Basement Laboratories, RV-ville, USA
INTRODUCTION:
This explains the results of experiments in software development that use extensible markup within commonly viewed text and that are used as unseen background devices to facilitate a relational text gathering system. This can facilitate convenience of finding information for viewers by presenters or for personal use for finding information later. These experiments revealed several primary problems to be overcome before implementing a useful computer based tool that could be made into a working example that would be simple to use.
So by selecting text like this:
and then clicking this Blue Dot button while "Scope" is entered:
You get this when you do a search for "Scope" :
You end up with a section of markup language code that looks like this:
In the very early announcement year of XML 1.0 I was introduced for the first
time to XML by an article written for a tech website, "ZDnet." After reading a
short abstract I had my own impression of what I thought XML was going to be
used for. I discovered after reading the full article that my idea for XML's use
was nonexistent or mentioned. This raised the first problem discovered if I were
to use my idea for extensible markup and that was that existing XML parsers can
not be used to extract information from commonly read text. The need for a
pull-parser, as it is referred to today, needed to become available.
The second problem was to create a user interface that allowed the viewer/user to add extensible markup while remaining in the viewing mode. This would not have been a problem if the user were expected to edit the text while in the markup language mode. Having a function that did all this in the background would be much better or more likely the best approach.
A third problem became obvious that having the ability to merge an existing open file with a second unopened file and then save both of them combined with the first file would add to the value of topical or semantically referenced information through the merging of common interest topics.
---------
Using MTML as the extensible markup solution after considering XML for relational or meta-data associations within commonly presented text.
To compare MTML to the semantic-web development perhaps is like comparing apples to oranges, both are fruit. Both utilize markup languages and both use computers to associate topical references and perhaps someday information gathering.
In the future of the Semantic Web powerful computers will parse and index XML tag sets surrounding published information that include topical references using meta-data in the form of namespace and attribute type formats of SGML / XML. The addition of a human readable attribute is unlikely. There is also a project to develop a similar kind of markup / file type that is more human readable, the Human Markup Language, and that is also based on namespace and attribute type formats of SGML / XML.
The absence of a magic glue to bind together the topical points of interest in the future envisioned semantic-web development can be overcome now by the user's or creator's actions as a binding force that acts as an interface now. The use of a human interface in conjunction with computer-based machines can allow the user to add or utilize human-readable extensible markup that can be shared across an interest group's topic by use of a construct in the form of a construct library or simpler topical dictionary.
To make such an interface work in a human-readable form a simplification of the extensible markup might be considered. By deliberately eliminating the use of namespaces and attributes in markup like XML it is possible to be left with element type only extensible markup tag-sets that work very well with pull-parsers. If that were to be taken one step further by dropping one significant rule of well-formed SGML or XML, and the use of empty spaces within the element type tag-set could be added then the user could read what the computer-based machine reads to act or take a meaningful action with the portion of information being sought.
Example [from MTML explained]:
It's easy to make an element type tag-set. Begin by putting "<" in front of the phrase "secret fishing spots", and ">" after the phrase "secret fishing spots" for the begin handle.
Example: <secret fishing spots>
To create the end handle for the same set of tags you add "</" in front of the phrase "secret fishing spots", and ">" after the phrase "secret fishing spots", for the end handle.
Example: </secret fishing spots>
It works like this:. This lake is full of Golden Trout and is a fisherman's dream, if you're the first one to fish it after the ice thaws. </secret fishing spots> Ha Ha... I told!
Now let's call it what it really is. We need a word that best describes the stupidity of telling this fishing spot to everyone that reads this. How about "<jerk>.". <jerk> This lake is full of Golden Trout and is a fisherman's dream if you're the first one to fish it after the ice thaws. </secret fishing spots> Ha Ha... I told!</jerk>
You will notice that the jerk tells the secret about that lake :-) Anyway that <jerk> fragment begins inside the <secret fishing spots> tag-set, but ends outside of it. This would not be considered well formed by XML standards. I recommend not doing this if you are using MTML in an XHTML document. [end]
This simple to read extensible markup then could be parsed using a fast and powerful pull-parser technique by the computer-based machines that read it. Each point of interest can be isolated and gathered from fuller texts that contain these topical based human-readable tag-sets. The user sees only readable information that relates to embedded information existing within the fuller text but is not seen while viewing it on these machines.
Two primary uses can be obtained that make using such a system worth having a system like this at this time. The user can utilize existing readable extensible markup created by others or the user can create their own.
The creation of a simple to use method for adding these tag-sets is necessary. The user should never see any extensible markup unless that it being part of an editing process or during the creation of presented documents by publishers.
In conclusion:
The relational text gathering system was the inspiration behind all the experiments. The user-accessible experiments presented the most interesting challenges. To this point explaining what it does and what it is used for still remains the greatest challenge of all. I believe that is because the future of this idea has yet to be implemented in a computer program that has gained wide spread acceptance.
Thanks to those that have taken an interest in this experiment.
What can you do with Intuition 1.3 ?
As far as what Intuition can do is simple to say. You can open an Intuition file, read it, make changes to it, and save it. You can export an Intuition file that can be made web-ready for cross-platform distribution over the internet. You can protect the cross-platform integrity of an Intuition file so that you can send it through the e-mail without destroying it. When you receive a protected Intuition file in the e-mail you can use a convenient process to convert it to user ready. You can place web-ready Intuition files on the internet that when downloaded from the internet will automatically convert themselves so that the protection process is unseen by the user. Intuition does this by using a hyper-link in a page. Intuition files can carry embedded images in the single file that is downloaded. In that way you can provide an entire website in a single downloadable file. Intuition files can be pre-indexed using MTML so as to facilitate a more powerful reading experience.
The end of the parser experiments.
There are only a few requirements that can be regarded as standard rules or technique that hold true to using MTML in documents and that work well.
1.) An MTML tag set must start and end inside of the document that it is being used in.
2.) An MTML tag set must start and end inside of any object set that is inside of the document that the object set is being used in. Objects can be isolated by using "<page>" & "</page>" tags like in the e-Book Study Tool version or they can be specialized forms of tagging that are specific to the needs of the computer application utilizing them. An example of special-use-tags could be like the ones used inside this HTML page for the sub-browser experiment. This holds true even in the XML-SQL experiments using the PNLP algorithm to parse and selectively populate an existing database using MTML and the Valentina Database as an experimental platform.
This is used to create individual objects that need to be defined before they are utilized in the sub-browser experiment.
When it comes down to using MTML in documents there is one single reason for doing so, and that is having the presented document utilize the relational text gathering system features of MTML. Even though MTML at times barrows from XML and HTML it has its one unique ability. MTML was designed to work inside of the text being presented. MTML was designed to be accessible for alteration by the user after the text was presented.
Mark Brownell
Gizmotron Graphics
gizmotron@earthlink.net | http://home.earthlink.net/~gizmotron/index.html | crawl-002 | refinedweb | 1,685 | 58.72 |
- Type:
Bug
- Status: Open
- Priority:
Major
- Resolution: Unresolved
- Affects Version/s: 11.3
-
- Component/s: java - Project, java - Source
-
- Environment:
NB-11.3beta1, jdk-13, Win7
After creating a library from javafx-sdk-13.0.2, including source (had to unzip source and add each of the 7 top level zip directories as a folder), almost all import statements are red underlined with an error. From within a javafx source file, "Go To Source", "Go To Declaration" do not work. For example for Label.java there is
import javafx.beans.property.ObjectProperty;
in the editor we get the popup error
package javafx.beans.property is not visible
(package javafx.beans.property is declared in the unnamed module, but module javafx.beans.property does not read it) | https://issues.apache.org/jira/browse/NETBEANS-3768 | CC-MAIN-2021-39 | refinedweb | 126 | 53.27 |
Details
- Type:
Sub-task
- Status: Resolved
- Priority:
Blocker
- Resolution: Fixed
- Affects Version/s: None
-
- Component/s: documentation
- Labels:None
Activity
- All
- Work Log
- History
- Activity
- Transitions
assemble.xml is missing a license header
ditto "update-versions" script
should we be documenting requirements (ruby for update-versions) somewhere? README.txt?
Thanks for taking a look, Patrick. Here's a new patch with the appropriate license headers added. Other changes:
- Changed the version to 0.1.0-incubating-SNAPSHOT.
- Add an Apache Incubator disclaimer.
- Add extra metadata to jar's manifest.
- Ensure LICENSE.txt and NOTICE.txt are included in jars (by using the maven-remote-resources-plugin).
- Ensure source and javadoc jar files are build along with jar files to make user's IDE experience smoother.
- A bit of maven simplification (removal of maven-compiler-plugin from all child projects, since it is inherited from the parent POM).
Still to do:
- Add some build instructions to the src distribution.
- Figure out how to include release notes in the src distribution.
- Document branching strategy on release page.
New patch:
- Added BUILD.txt which lists requirements and describes how to build from source.
- Added a reference to the release notes from README.txt.
I also added some instructions on branching to, based on Hadoop's model.
I think this is ready to go in and be used to drive a release.
mvn install fails with:
[INFO] [remote-resources:process{execution: default}
]
Downloading:
[INFO] Unable to find resource 'org.apache.whirr:license-resources:jar:0.1.0-incubating-SNAPSHOT' in repository jclouds ()
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD ERROR
I don't see anything in BUILD.txt about this.
also the pom files seem to have been reformatted, some lines now exceed 80 chars unnecessarily.
(specifically the namespace definitions on the <project> element)
The current howtorelease looks like a good start... some thing missing near the end but in general looks good to me.
New patch which uses the apache-jar-resource-bundle JAR instead of a Whirr-specific one. I've tested with a clean local maven repo. Also reverted pom formatting change.
+1, looks good to me. RAT is clean. I ran install and also built the "mvn site", both of which were successful.
The javadoc api link is 404 though, I don't see this on the howtorelease. Is it a manual step or is it not being triggered as part of the build?
The javadoc is built if you do "mvn site -Pjavadoc" (arguably we should get "mvn site" to just work, the reason javadoc was put in a profile was to save time when building jars, since javadoc jars are built too).
I've just committed this.
Here's a patch which implements the process documented at. This also changes the top-level POM so that the site can be built from the top-level (with aggregated Javadoc).
Before applying the patch run:
svn mv site/src src | https://issues.apache.org/jira/browse/WHIRR-77 | CC-MAIN-2016-50 | refinedweb | 486 | 59.9 |
The Elastic Stack is a far-reaching ecosystem with many interconnected parts, and the official Puppet Modules are no exception when it comes to the configuration management side of the house. Today, we want to highlight some developments taking place in the Elastic Puppet ecosystem to help spread awareness of new features and upcoming changes.
Modules Roadmap
First, some housekeeping items that pertain to all of our official modules.
Puppet 3
The most prominent upcoming change is the deprecation of Puppet 3 (if you’re skimming this post, don’t panic! You still have time). As noted in the upstream Puppet Labs page, version 3 met its end in December 2016, which means that it is not only deprecated, but end-of-life, and past the cutoff date for any future updates. As systems operators ourselves, we recognize that keeping stride with software versions is one of the challenges that comes with the discipline, particularly when it comes to large enterprises.
With that in mind, we’ll be keeping version 3.8 of Puppet in our list of supported versions for a period to ensure everyone has a window of time to work in, for those cases where upgrading is a challenge. Nevertheless, the Puppet ecosystem is moving on from version 3, and we can only hold on to old versions for so long. It’s for this reason that we will be removing support for Puppet 3 with the 6.x release of the Elastic Stack, which grants many months of leeway for those operations engineers with a Puppet upgrade still on their plate. Version 6 of the Elastic Stack is likely to arrive in late 2017, and will be prefaced with additional announcements as its release draws closer.
New Forge Namespace
What open source project doesn’t like changing names every so often? Our modules on the Puppet Forge now properly live under the “elastic” namespace where all future module updates and release will land. While any references to old modules under the
elasticsearch namespace will continue to work, the modules there are no longer updated. We suggest updating any automation or tooling that references released modules from the Forge to this new namespace (for example, to
elastic/elasticsearch).
Official Puppet Kibana Module
One of the most common requests we hear from Puppet users is for other parts of our stack to ship official modules. At Elastic{ON} 2017 we released a beta version of an official Puppet Kibana module, which is now formally released at version 5.0 (major version synchronized with the rest of the Elastic Stack). The module supports everything you would expect from our Puppet modules, including Kibana plugin resources to make managing Kibana through Puppet a much easier experience.
As always, we’re eager to hear from you regarding any bugs you've found or features you’d like to see and would encourage any bug reports or feature requests to be filed in the puppet-kibana GitHub repository.
Elasticsearch: Tasty New Features
The official Elasticsearch module hasn’t stood still either. In addition to the steady march of bugfixes, the official Elasticsearch module supports a couple of useful new resource types: indices and pipelines.
While the module already supported managing index templates (useful for auto-created indices from tools like Logstash or Beats), the
elasticsearch::index type can help manage mappings and settings for existing indices in an Elasticsearch cluster. For example, to manage an Elasticsearch index called “logs” to retain only 1 replica per shard:
elasticsearch::index { 'logs': settings => { 'index' => { 'number_of_replicas' => 1 } } }
Likewise, pipelines are now supported as well. The ability to codify processing pipelines in Puppet can help centralize your workflow for processing logs and documents in Elasticsearch (see our other blog posts about ingest node pipelines for more introductory content). For example, to create a pipeline that will automatically parse dates, the following Puppet resource could be used:
elasticsearch::pipeline { ‘parsedate’: content => { 'description' => 'Parse the date field into @timestamp', 'processors' => [{ 'date' => { 'field' => 'date', 'formats' => ['dd/MM/yyyy hh:mm:ss'], 'timezone' => 'US/Pacific' } }] } }
Logstash: All Aboard for Version 5
Version 5 of Logstash brought huge improvements to the handling of the Logstash system service, adding full support for systemd, among other things. In the past, the Puppet module was responsible for much more of the work around service handling, which was a common source of problems as the module became progressively more complex in order to handle various edge-cases across distributions. With Logstash itself now handling the service, the Puppet module is much simpler and more stable when it comes to service management.
It's important to note, however, that the changes in service management were so comprehensive that it became impractical for the module to support Logstash 2.x and Logstash 5.x at the same time. Thus, module version 5 only supports Logstash 5. Of course, the legacy module elasticsearch/logstash is still available if you need to run Logstash 2.
It's now possible to fully manage Logstash settings, startup options, and JVM options with the module. Like this:
class { 'logstash': settings => { 'pipeline' => { 'batch' => { 'size' => 25, 'delay => 5, } } } }
Since the settings are all defined as standard arrays and hashes, they work well with Hiera too.
Plugin support is now comprehensive, with support for remote locations like
puppet:// and
http:// URLs. The latter is essential for people choosing to install the new X-Pack for Logstash.
Finally, a lot of progress on the module is something you probably won't see, but hopefully you get to see the results. All new features, including those above, are now developed under testing from a re-written test suite. The tests are there to ensure everything in the module works reliably, across every supported operating system and Puppet version. | https://www.elastic.co/blog/puppet-state-of-the-union-may-2017 | CC-MAIN-2018-09 | refinedweb | 960 | 57.61 |
WebSockets Tutorial: Creating a Real-Time WebSocket Server
In this tutorial, let's take a look at how to create a websocket server, which will allow real-time interaction with your users.
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How WebSockets Work
Websockets are essentially constant connections made between the server and your computer. When you access a website, it can send a
GET request to the server, to initiate a WebSocket connection between the user and the server.
Websockets vs REST API
If the user leaves the website, the connection is cut, so the user only has access to the websocket as long as they continue to use the website.
How Long Can a Websocket Stay Open?
Once a WebSocket is created, it can theoretically stay open forever. There are a few exceptions to this:
- The server goes down: This will break the websocket, but we can attempt to reconnect to it.
- A power outage or internet connection problem: The connection will break if the user's internet stops.
- Inactivity: If the user doesn't interact or send data through the websocket, the connection inevitably times out.
As such, when we design our websockets, we need to consider how we reconnect to them if the user's connection stops for some reason, as to not interrupt the user's experience.
Making a WebSocket
A websocket, therefore, consists of two parts; the server and the local machine that the user is using. For what we are doing, we'll be using Node.JS as our server, but other languages also support websockets.
When the user accesses our website, we load a file with some Javascript which contains a connection string to our websocket. Meanwhile, in our backend, we will have websocket set up that the user will connect to. This is shown in the below diagram:
Step 1: Creating our Server
Let's start by making our Node.JS web server for the websocket connection. For this, we're going to be using an express server with an additional package called
express-ws. This additional package will allow us to use
ws in the same way we might use
get.
import path from 'path' import { fileURLToPath } from 'url' const __filename = fileURLToPath(import.meta.url); const __dirname = path.dirname(__filename); import express from 'express' import expressWs from 'express-ws' import http from 'http' // Our port let port = 3000; // App and server let app = express(); let server = http.createServer(app).listen(port); // Apply expressWs expressWs(app, server); app.use(express.static(__dirname + '/views')); // Get the route / app.get('/', (req, res) => { res.status(200).send("Welcome to our app"); }); // Get the /ws websocket route app.ws('/ws', async function(ws, req) { ws.on('message', async function(msg) { console.log(msg); // Start listening for messages }); });
The last clause,
app.ws, refers to the websocket, and that's what we'll try to connect to on the frontend. For the time being, the websocket only consoles log a message whenever it receives one from the frontend. Let's change it so that it sends something back:
// Get the /ws websocket route app.ws('/ws', async function(ws, req) { ws.on('message', async function(msg) { // What was the message? console.log(msg); // Send back some data ws.send(JSON.stringify({ "append" : true, "returnText" : "I am using websockets!" })); }); });
Now whenever this websocket connection receives data, it will send back an object, which we've defined above. We can then manipulate this object in our frontend, to display or change views for the user.
Step 2: Connect on Frontend
As we mentioned before, when our user visits our website, we provide them with some local javascript in our HTML document. I've added a few other elements for our demo in the index.html file:
<script src="local.js"></script> <p>Welcome to websockets. Click here to start receiving messages.</p> <button id="websocket-button">Click me</button> <div id="websocket-returns"></div>
Next, we need to put some connection details in our
local.js file. I have created a single connection file which we run after the document has loaded. It looks like this:
// @connect // Connect to the websocket let socket; const connect = function() { return new Promise((resolve, reject) => { const socketProtocol = (window.location.protocol === 'https:' ? 'wss:' : 'ws:') const port = 3000; const socketUrl = `${socketProtocol}//${window.location.hostname}:${port}/ws/` // Define socket socket = new WebSocket(socketUrl); socket.onopen = (e) => { // Send a little test data, which we can use on the server if we want socket.send(JSON.stringify({ "loaded" : true })); // Resolve the promise - we are connected resolve(); } socket.onmessage = (data) => { console.log(data); // Any data from the server can be manipulated here. let parsedData = JSON.parse(data.data); if(parsedData.append === true) { const newEl = document.createElement('p'); newEl.textContent = parsedData.returnText; document.getElementById('websocket-returns').appendChild(newEl); } } socket.onerror = (e) => { // Return an error if any occurs console.log(e); resolve(); // Try to connect again connect(); } }); } // @isOpen // check if a websocket is open const isOpen = function(ws) { return ws.readyState === ws.OPEN }
To connect to a websocket, we have to use ws://, instead of HTTP, and wss://, instead of HTTPS. We put that into our
new WebSocket() function to generate our connection. Inside our connection function, we then have three event listeners:
socket.onopen: If the connection is successful and open, this fires.
socket.onmessage: Any time the server sends a message to us, this fires. In our example, we will append a new element to our user's HTML if they receive data that has
appendset to
true.
socket.onerror: If the connection fails, or an error occurs, this will fire.
Let's tie it all together; since we are storing our socket variable in the global scope, we can send data after the connection is successful. The below event listener connects to the websocket, and then sends data to the server when the user clicks our HTML button.
When the server receives this data, it then sends back its own data, as the server's message' event fires. This comes back to the user, which then adds a new element to their document.
javascript Copy
// When the document has loaded document.addEventListener('DOMContentLoaded', function() { // Connect to the websocket connect(); // And add our event listeners document.getElementById('websocket-button').addEventListener('click', function(e) { if(isOpen(socket)) { socket.send(JSON.stringify({ "data" : "this is our data to send", "other" : "this can be in any format" })) } }); });
Conclusion
And that's it! Now, we have a functioning Websocket, which allows you to send data to the server and back to the user. If you want to learn more or download the source code, here are some useful links:
Published at DZone with permission of Johnny Simpson, DZone MVB. See the original article here.
Opinions expressed by DZone contributors are their own. | https://dzone.com/articles/websockets-tutorial-creating-a-real-time-websocket?fromrel=true | CC-MAIN-2021-31 | refinedweb | 1,135 | 58.18 |
You can browse the documentation for Vue Flags on the website.
npm install @growthbunker/vueflags # Or if you prefer using yarn yarn add @growthbunker/vueflags
In your
main.js file:
import Vue from "vue" import VueFlags from "@growthbunker/vueflags" Vue.use(VueFlags)
Create a new plugin in
plugins/vueflags.js:
import Vue from "vue" import VueFlags from "@growthbunker/vueflags" Vue.use(VueFlags)
Add this new plugin to
nuxt.config.js.
module.exports = { // ... plugins: [{ src: "@/plugins/vueflags.js" }]; }
Get the latest version from jsdelivr, and import the JavaScript file in your page.
<script src=""></script> <script src=""></script>
We recommend our users to lock Vue Flags's version when using CDN. Requesting the latest version (as opposed to "latest major" or "latest minor") is dangerous because major versions usually come with breaking changes. Only do this if you really know what you are doing. Please refer to jsdelivr.com for more information.
All the flags are available here. Copy them somewhere in your somewhere in your "public" or "static" folder. You will also have to set the icon path for the component to be able to find them (see package options and component props).
A huge thank you to the author for designing these flags.
Once the plugin is installed, you can use the component like this:
<template> <vue-flag </template>
You are more than welcome to contribute to Vue Flags. Just submit changes via pull request and I will review them before merging.
Fork it! 🤙
Create your feature branch:
git checkout -b my-new-feature
Commit your changes:
git commit -am "Add some feature"
Push to the branch:
git push origin my-new-feature
Submit a pull request 👍
The documentation is available in the
docs folder. The Vue Flags components are available in the
lib folder.
Vue Flags is MIT licensed. | https://openbase.com/js/@growthbunker/vueflags | CC-MAIN-2021-43 | refinedweb | 301 | 67.25 |
cswinWtoA Struct Reference
Small helper to convert a wide to an ANSI string, useful when passing arguments to a function. More...
#include <csutil/win32/wintools.h>
Detailed Description
Small helper to convert a wide 93 of file wintools.h.
Constructor & Destructor Documentation
Construct from a wchar_t string.
Definition at line 99 of file wintools.h.
Destruct, free up memory.
Definition at line 102 of file wintools.h.
Member Function Documentation
Return the string passed in on construction as an ANSI string.
Definition at line 105 of file wintools.h.
The documentation for this struct was generated from the following file:
- csutil/win32/wintools.h
Generated for Crystal Space 1.4.1 by doxygen 1.7.1 | http://www.crystalspace3d.org/docs/online/api-1.4.1/structcswinWtoA.html | CC-MAIN-2017-30 | refinedweb | 116 | 53.58 |
Computing Syzygy Modules in Sympy
Reading.
Edit: @isuruf claims that there is a syzygy calculation tucked away inside sympy that I had not discovered. I haven’t tried it.. $ G = AF$. $ F = BG$ . $ Ax.
import sympy as sy def spoly(f,g,*gens): ltf = sy.LT(f,gens) ltg = sy.LT(g,gens) lcm = sy.lcm(ltf,ltg) s = lcm / ltf * f - lcm / ltg * g return s #grobner tracking. Maintaining the relation of the grobner basis to the original def extended_groebner(F, *gens): n = len(F) markers = [sy.Dummy() for i in range(n)] Fext = [ f + a for a, f in zip(markers, F)] gen_ext = list(gens) + markers Gext = sy.groebner(Fext, gen_ext) A = [[g.coeff(m) for m in markers ] for g in Gext] G = [ sy.simplify(g - sum( [ m * aa for m,aa in zip(markers, a) ] )) for a,g in zip(A,Gext) ] #remove dummy parts assert( sy.simplify(sy.Matrix(G) - sy.Matrix(A) * sy.Matrix(F)).is_zero ) # maybe assert buchberger criterion return G, A def reduce_basis(F,G,*gens): B,rems = list(zip(*[sy.reduced(f,G, gens) for f in F])) print(B) print(rems) assert( all([r == 0 for r in rems] )) # assuming G is a grobner basis assert( sy.simplify(sy.Matrix(F) - sy.Matrix(B) * sy.Matrix(G)).is_zero ) return B # generators for the syzygies of G. Schreyer's Theorem. Cox Little Oshea Theorem 3.2 chapter 5 def syzygy(G,*gens): # assuming G is groebner basis n = len(G) basis = [] I = sy.eye(n) for i, gi in enumerate(G): for j, gj in enumerate(G): if i < j: s = spoly(gi,gj,*gens) print(s) a,r = sy.reduced( s , G, gens ) assert(r == 0) # should be groebner basis lti = sy.LT(gi,gens) ltj = sy.LT(gj,gens) lcm = sy.lcm(lti,ltj) ei = I[:,i] ej = I[:,j] basis.append(lcm / lti * ei - lcm / ltj * ej - sy.Matrix(a)) assert( sy.simplify(sy.Matrix(G).T * basis[-1]).is_zero) # should all null out on G return basis x,y,z,s = sy.symbols("x y z s") F = [x+y+z, x*y+y*z+z*x, x*y*z-1] G, A = extended_groebner(F, x,y,z) B = reduce_basis(F,G,x,y,z) Gsyz = syzygy.
def matrix_to_eqs(m): nrows, ncols = m.shape gens = [sy.Dummy() for i in range(ncols)] eqs = m @ sy.Matrix(gens) return eqs, gens def eqs_to_matrix(eqns, gens): return sy.Matrix( [[ eq.coeff(g) for g in gens] for eq in eqns]) | https://www.philipzucker.com/computing-syzygy-modules-in-sympy/ | CC-MAIN-2021-39 | refinedweb | 421 | 61.93 |
cin.ignore(boost::integer_traits<int>::const_max);
Or alternatively, if you don't have boost
cin.ignore(std::numeric_limits<int>::max());
Alright, am getting somewhere with my code... Haven't shown you the file where things happen... Going to show you one function as yet, the rest later....
Menu.cpp
Q. this lineQ. this lineCode:#include <iostream> #include <algorithm> #include <conio.h> #include "Menu.h" using namespace std; Menu::Menu() {}; void Menu::titleDescription() { clrscr(); printf("\t\t\t\tÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»\n"); printf("\t\t\t\tº FLEET DETAILS º\n"); printf("\t\t\t\tÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ\n"); printf("\n\nThis program requests a file name in which a fleet of cars is saved.\n\n"); printf("A menu which allows the user an option to view the fleet, " "\nsearch for a car, add new car, and update file is provided.\n\n"); pause(); clrscr(); programLimits(); } // --------------------------------------------------------------- // Implementing the user instructions function void Menu::programLimits() { clrscr(); printf("\t\t\t\tÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»\n"); printf("\t\t\t\tº PROGRAM LIMITATIONS º\n"); printf("\t\t\t\tÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ\n"); printf("\n\nINPUTS:\n\n"); printf("FileName: FleetData.txt\n"); printf("Engine Capacity: (i.e.) 1.8L must be 1800\n"); printf("Dates: day, month, year\n"); printf("Tank capacity: Value 1 for filled, and 0 for unfilled\n\n"); pause(); } void Menu::clrscr() { system("cls"); } void Menu::pause() { puts("\n\n"); system("pause"); } // --------------------------------------------------------------- // Run will handle the user choice and run desired operation void Menu::run() { bool again = true, found = false; CarFleetIterator iterate=fleet.begin(); do { clrscr(); printf("\n \t\tÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»\n"); printf(" \t\tº FLEET DETAILS º\n"); printf(" \t\t\314ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ\271\n"); printf(" \t\tº Options º\n"); printf(" \t\tº º\n"); printf(" \t\tº1. Description of Program º\n"); printf(" \t\tº º\n"); printf(" \t\tº2. Read Fleet from File º\n"); printf(" \t\tº º\n"); printf(" \t\tº3. Display List of cars º\n"); printf(" \t\tº º\n"); printf(" \t\tº4. Search Car by Model & Make º\n"); printf(" \t\tº º\n"); printf(" \t\tº5. Add new car details º\n"); printf(" \t\tº º\n"); printf(" \t\tº6. Update Fleet File º\n"); printf(" \t\tº º\n"); printf(" \t\tº7. Edit Flee File º\n"); printf(" \t\tº º\n"); printf(" \t\tº8. Edit Flee File º\n"); printf(" \t\tÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ\n\n"); printf("\n\n\t\tPlease enter the NUMBER of your choice: "); switch(_getch()) { case DESCRIBE: titleDescription(); break; case READF: readFleetFromFile(); pause(); break; case DISPLAY: showFleetList(iterate, found); pause(); break; case SEARCHF: { // Search by make & model puts("\n\n\t\tNot yet in operation!!"); if( (iterate = searchCarDetails(found)) == fleet.end() ) { printf("\n\n\tTry searching again!"); } else if(found) { showFleetList(iterate, found); // Display found record } pause(); break; } case ADDCAR: AddNewCar(); pause(); break; case UPDATEF: updateFleetFile(); // Save changes to text file pause(); break; case EDITF: EditFleet(); pause(); break; case EXITP: clrscr(); exit(1); default: again = false; break; } } while (again); }
doesn't seem to do the right job. After option 2 (READF), fleet gets initialized with all data from file... But, iterate doesn't seem to carry the data.... Cause the moment i press option 3 (DISPLAY), no proper data is passed... am i doing anything wrong?doesn't seem to do the right job. After option 2 (READF), fleet gets initialized with all data from file... But, iterate doesn't seem to carry the data.... Cause the moment i press option 3 (DISPLAY), no proper data is passed... am i doing anything wrong?Code:CarFleetIterator iterate=fleet.begin();
here'sshowFLeetList()
Code:// --------------------------------------------------------------- // Implementing function to display fleet of cars void Menu::showFleetList(CarFleetIterator iter, bool searched) { sortAlpha(); clrscr(); printf("\t\t\t\tÉÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ»\n"); printf("\t\t\t\tº FLEET DETAILS º\n"); printf("\t\t\t\tÈÍÍÍÍÍÍÍÍÍÍÍÍÍÍͼ\n"); // **************** HEADINGS *************** printf("\n\n%-17s%-12s%-13s%-12s%-8s\n\n", "Car Make/Model", "Year Model", "Engine Size", "Return Date", "Fuel Tank" ); // **************** HEADINGS *************** // Display one one record if fleet was searched if (iter!=fleet.end() && searched) { iter->write(cout, true); } else { // Display fleet details to the screen for(iter=fleet.begin(); iter!=fleet.end(); iter++) { iter->write(cout, true); } } }
Last edited by csonx_p; 07-10-2008 at 08:09 AM.
1)
By overloading operator << and >> for Car.
ostream& operator << (ostream& rLhs, Car& rRhs);
istream& operator >> (istream& rLhs, Car& rRhs);
[Some may require some const somewhere, but I'm not sure where to avoid ambiguities.]
2)
Car car;
cout << car;
cin >> car;
[Remember, the keyboard and screen are streams, too, so they work just the same as files!]
You would have to write a operator >> for a car object. It would look very similar to your read function, using the operator >> on the individual fields (and you can either keep the tankstatus operator, or write the code to read it as an integer and then transfer it to the enum inline in that function.
Note that in either solution (operator >>() or read()), you would have to put some sort of whitespace between each element of the car.
--
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
You can have:You can have:Code:int foo(int x) { return x + 2; } ... int foo(int x) { return x * 2; }
Code:int foo(int x) { return x + 2; } float foo(int x) { return x * 2; }
--
Mats
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers.
You can't pass a boolean to the operator.
But the thing is that the class is an object - it should accept whatever you throw at it.
It's your responsibility as the user of the class to feed it correct data and make it work correctly.
In other words, your code can check if it's the keyboard or not or such, then feed the proper argument to the operator >> or << of the class.
Maybe, and maybe not.
A good rule of C++ that I always use is to abstract (hide reusable code inside a user friendly interface) and encapsulate (encapsulate functionality inside classes with a good public interface).
Doing this makes it easy to create polymorphic, powerful code that takes little effort to use correctly.
Try it. If nothing else, it's fun to experiment with.
Compilers can produce warnings - make the compiler programmers happy: Use them!
Please don't PM me for help - and no, I don't do help over instant messengers. | https://cboard.cprogramming.com/cplusplus-programming/104968-please-check-my-cplusplus-4.html | CC-MAIN-2017-26 | refinedweb | 1,090 | 64.1 |
1 /* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5 /* 6 * The Apache Software License, Version 1.1 7 * 8 * 9 * Copyright (c) 2001,.dv; 63 64 /** 65 * Datatype exception for invalid values. 66 * 67 * @xerces.internal 68 * 69 * @author Sandy Gao, IBM 70 * 71 */ 72 public class InvalidDatatypeValueException extends DatatypeException { 73 74 /** Serialization version. */ 75 static final long serialVersionUID = -5523739426958236125L; 76 77 /** 78 * Create a new datatype exception by providing an error code and a list 79 * of error message substitution arguments. 80 * 81 * @param key error code 82 * @param args error arguments 83 */ 84 public InvalidDatatypeValueException(String key, Object[] args) { 85 super(key, args); 86 } 87 88 } | http://checkstyle.sourceforge.net/reports/javadoc/openjdk8/xref/openjdk/jaxp/src/com/sun/org/apache/xerces/internal/impl/dv/InvalidDatatypeValueException.html | CC-MAIN-2018-13 | refinedweb | 112 | 57.87 |
Java Coding Best Practices - Coding Guidelines
Always use comments for your class, methods and variables
One of the best practice is using comments wherever posible. It will make your more understandable not only for you, but also for other developers who use your code.
The another advantage of using the comments is Java Doc. You can generate the Java Doc with a click of your mouse in any IDE which supports it like Eclipse.
Here are the few examples how to use comments in a better way.
Class Comments:
/**
* This class is used to perform operations on database at back-end.
* 1. Updating the database
* 2. Retrieving the data from database
*/
public class DatabaseOperations{
...
}
Method Comments:
/**
* This method is used to updating the database with the data
* given in the form of xml as a parameter.
* @params strXMLQuery the operation to be performed - in the form of xml.
* @returns boolean ...
*/
public boolean DatabaseUpdate(String strXMLQuery){
...
}
Variable Comments:
/** Status of the email with the database*/
private static final boolean DATABASE_STATE_EMAIL;
Always use meaning full names for your classes, methods and variables
Using meaningful names to your methods or variables not only simplyfies your coding tasks but also it makes your code more readable and undestandable.
For example, to declare a method which performs uploading a file from client machine to server, rather than declaring it as upload() declare it as uploadFileToServer() which conveys better meaning and simplifies the task of writing other methods which uses this method.
Do not extend a line to more than acceptable number of characters
The source files should be more readable in order to improve your productivity. One of such activity is writing code in a way such that no line shoud exxtend more than the screen width. i.e you should not drag the horizontal scrollbar in order to see the entire line.
For this you should follow strict line width. Say, Maximum 80 characters per line. If the line exceeds this width, simply devide that line into two parts. That can be done in two ways.
- Simplify your code so that one line of code can be written in two lines.
- Wrap the line to second line.
The first way will increase the ease in your code but at the same time you should be very careful. Using this technique excessively will make your code unmanageable.
boolean result = ((test1 != var1 && test2 == var2) || test3 > var3) && test4 == var4)
The above code can be written as below
boolean flag1 = (test1 != var1 & test2 == var2)
boolean flag2= flag1 || (test3 > var3)
boolean result = flag2 && (test4 == var4)
The second technique is far simpler and recomonded. For example, to write
String strResult = (null != strVar1 && null != strVar2 && strVar1.equalsIgnoreCase(strVar2)) ? true : false;
Simply expand it to multiple line as below..
boolean strResult = (null != strVar1 &&
null != strVar2 &&
strVar1.equalsIgnoreCase(strVar2)
) ? true : false;
Use a formatter like jelopy, if posible, to format the java files
Formatting the code using a tool will save lots of time as well as makes the code beautiful so that we can easily understand the code whenever we see it. The tools like Jaloppy are very useful in this aspect. They are not only freeware but also very powerful.
Always use Constants on left side while comparing with variables
Using variables on left side in a comparision will lead to unpredictable results in some cases. For example the code below explains how it is.
intResult = strVar01.equals(CONST_VAR02);
Tips while using multiple comparisions
Is it always suggested that before performing any opertions on an Object, first check posible errors which can be avoided. Say for example, you are comparing a string value to check whether it is empty or null. It is good to test for null first before empty value. This will avoid the null pointer exceptions.
If you use to test the empty value first, if the value is null then there is a probability to occur the error. If you test null value before that then this case can be avoided.
Example:
boolResult = (null == strVar01 strVar01.equals(""))?true:false;
Never use generic exception to catch exceptions
Always use the speccific exception for the perticular operation so that you can easily debug the error and easily solve if any bug is detected. This will drastically reduce the maintainability. It is a good habit to catch exceptions like null pointer exception wherever possible.
Example:
try{
intResult = Integer.parseInt(strVar01);
}catch(NullPointerException objNullPointerException){
//Do what you want to do..
}
Like it on Facebook, +1 on Google, Tweet it or share this article on other bookmarking websites. | https://www.boddunan.com/articles/programming/26-java-a-j2ee/47-java-coding-best-practices-coding-guidelines.html | CC-MAIN-2020-29 | refinedweb | 756 | 64.3 |
{Owner Car} {Silas Ferrari} {Silas Porche} {John Honda} {Smith Renaut} {Smith Ford}See this list has redundant data. If I want to show it in a report, it probably be confuse to the viewer. So it's a good idea to take off this junk data:
{Owner Car} {Silas Ferrari} {{} Porche} {John Honda} {Smith Renaut} {{} Ford}This kind of information is common from queries with JOINs. I developed a cool proc which takes off this junk data. It is in version 0.1 yet, because I'm still trying it... not 100% stable. Needs some fixes. I'll update it as I note errors. For now, it conforms to my purposes:Hey! RS's code (or the modified version) on the bottom is the best way to achieve the objective. Should we take the proc below off here?
proc synthesize {List reference Fields} { # synthesize: Receive a list of lists and synthesizes a query with rows # returned by a JOIN. Returns the synthesized list # # List: List to be synthesized # reference: fields to be compared # Fields: Fields which will be used in synthesize. It's a list of indexes # version 0.1 - 2005-12-06 # by [Silas] Justiniano - silasdb at gmail dot com set i 0 while {$i < [llength $List]} { for {set k 0} {$k < [llength [lindex $List 0]]} {incr k} { set aux($k) {} } set j [expr $i+1] while {[lindex $List $i $reference] eq [lindex $List $j $reference]} { for {set k 0} {$k < [llength [lindex $List 0]]} {incr k} { if {[lsearch $aux($k) [lindex $List $j $k]] == -1 && [lsearch $Fields $k] != -1} { lappend aux($k) [lindex $List $j $k] } } incr j if {[expr $j-1] == [llength $List]} {return $List} } set max 0 foreach valor [array names aux] { if {[lindex $aux($valor) 0] == [lindex [lindex $List $i] $valor]} { set aux($valor) [lreplace aux($valor) 0 0] } if {$max < [llength $aux($valor)]} { set max [llength $aux($valor)] } } for {set k $i} {$k <= [expr $max+$i]} {incr k} { for {set l 0} {$l < [llength [lindex $List 0]]} {incr l} { if {$k == $i} { lappend Itens [lindex [lindex $List $i] $l] } else { if {[lsearch $Fields $l] == -1} { lappend Itens {} } else { lappend Itens [lindex $aux($l) 0] set aux($l) [lreplace $aux($l) 0 0] } } } set List [linsert $List $k $Itens] unset -nocomplain Itens } set List [lreplace $List [expr $i+$max+1] [expr $j+$max]] if {$max == 0 && $i == [llength $List]-1} break incr i [expr $max+1] } return $List }#Testing...:
set A { {Silas Ferrari} {Silas Porche} {John Honda} {Smith Renaut} {Smith Ford} } puts [synthesize $A 0 1]Notes the first argument is the list, the second is the "field" that you will use as reference to synthesize and the last is a list of indexes to be deleted when found more than one (is this explanation fine? :) ).As I said, the last argument can receive a list of indexes. So in the following list:
{Owner Car Color} {Silas Porche Blue} {Silas Porche Black} {Silas Ferrari Red} {John Honda Blue} {Smith Renaut White} {Smith Renaut Gray} {Smith Ford Green}Each owner has a car, some have more than one, some of them are not different, but have different color. A synthesized list would be:
{Owner Car Color} {Silas Porche Blue} {{} {} Black} {{} Ferrari Red} {John Honda Blue} {Smith Renaut White} {{} {} Gray} {{} Ford Green}I reached it using:
puts [synthesize $A 0 {1 2}]Please, help to improve this proc.
RS experimented with this (which has no column-width formatting):
proc synthesize llist { set last {} set ress {} foreach list $llist { set reslist {} foreach e $list f $last { lappend reslist [expr {$e eq $f? {}: $e}] } lappend ress $reslist set last $list } set ress }Testing:
set data { {Owner Car Color} {Silas Porche Blue} {Silas Porche Black} {Silas Ferrari Red} {John Honda Blue} {Smith Renaut White} {Smith Renaut Gray} {Smith Ford Green} } % join [synthesize $data] \n Owner Car Color Silas Porche Blue {} {} Black {} Ferrari Red John Honda Blue Smith Renaut White {} {} Gray {} Ford Green
Silas - wow! RS's code is really better than mine! It requires a list whose repeated values comes firstly. For example:
{Kevin Honda Green} {Kevin Ford Green}"Kevin" is the repeated value here. "Green" is repeated too, but it is a property of the car, which is not repeated. Unfortunatelly RS's code doesn't works fine with this kind of list:
% synthesize {{Kevin Honda Green} {Kevin Ford Green}} {Kevin Honda Green} {{} Ford {}So I modified RS's code:
proc synthesize llist { set last {} set ress {} foreach list $llist { set reslist {} set found 0 foreach e $list f $last { if {$e eq $f && $found == 0} { lappend reslist {} } else { lappend reslist $e set found 1 } } lappend ress $reslist set last $list } return $ress }#Testing...:
% puts [synthesize {{Kevin Honda Green} {Kevin Ford Green}}] {Kevin Honda Green} {{} Ford Green}Although it requires a list whose "repeated" values comes firstly, I think this RS's modified code is much better than my first synthesize proc. It's easier, better and faster to get a list in this format directly from SQL and re-order it later than try to address the problem with a "non-ordered" list in this format.
Silas - 2005-12-09 - I noticed that queries results have a interesting organization form. They looks like a fractal. See:
A B D A B E A C D A C EIt's the basic form of a query with two join. So:
SELECT Books.name, Subjects.name, Authors.name FROM Books INNER JOIN Books_Subject ON Books.book_id = Books_Subject.book_id INNER JOIN Subjects ON Books_Subject.subject_id = Subjects.subject_id INNER JOIN Books_Authors ON Books.book_id = Books_Authors.book_id INNER JOIN Authors ON Books_Authors.author_id = Authors.author_id;I think many-to-many (using a intermediate table) relationships are the best example here. The query above would return (for one book inserted in the database):
{{The comunist manifest} {Politics} {Karl Marx}} {{The comunist manifest} {Politics} {Friedrich Engels}} {{The comunist manifest} {History} {Karl Marx}} {{The comunist manifest} {History} {Friedrich Engels}}RS's modified code would return:
{{The comunist manifest} Politics {Karl Marx}} {{} {} {Friedrich Engels}} {{} History {Karl Marx}} {{} {} {Friedrich}}It's still repeating some values. The next proc, makes it better:Silas - 2005-12-13: Now it IS working:
proc synthesize List { #updated 2005-12-13 for {set i 0} {$i < [llength $List]} {incr i} { set First [lindex $List $i] set j [expr $i+1] set max 0 while {[lindex $First 0] eq [lindex $List $j 0]} { for {set k 0} {$k < [llength $First]} {incr k} { if ![info exists aux($k)] {lappend aux($k) [lindex $First $k]} if {[lsearch $aux($k) [lindex $List $j $k]] == -1} { lappend aux($k) [lindex $List $j $k] } } incr j } if {$j > $i+1} { set List [lreplace $List $i $j-1] foreach valor [array names aux] { if {[llength $aux($valor)] > $max} {set max [llength $aux($valor)]} } for {set l 0} {$l < $max} {incr l} { for {set k 0} {$k < [llength $First]} {incr k} { lappend Items [lindex $aux($k) 0] set aux($k) [lreplace $aux($k) 0 0] } set List [linsert $List [expr $i+$l] $Items] unset Items } } unset -nocomplain aux set i [expr $j - 1 - $max] } return $List }#Testing...:
% synthesize $A {{The comunist manifest} Politics {Friedrich Engels}} {{} History {Karl Marx}It's another big proc (like RS, I don't like big procs). Probably it can be improved and diminished... if someone has time, please, work on it.
Category Algorithm | http://wiki.tcl.tk/15070 | CC-MAIN-2016-44 | refinedweb | 1,217 | 62.92 |
3.0 release notes¶
What’s new in 3.0¶
Warning
Upgrading from previous versions
3.0 introduces some changes that require action if you are upgrading from a previous version.
New Frontend Editing¶
django CMS 3.0 introduces a new frontend editing system as well as a customizable Django admin skin (djangocms_admin_style).
In the new system, Placeholders and their plugins are no longer managed in the admin site, but only from the frontend.
In addition, the system now offer two editing views:
- content view, for editing the configuration and content of plugins.
- structure view, in which plugins can be added and rearranged.
Page titles can also be modified directly from the frontend.
New Toolbar¶
The toolbar’s code has been simplified and its appearance refreshed. The toolbar is now a more consistent management tool for adding and changing objects. See Extending the Toolbar.
Warning
Upgrading from previous versions
3.0 now requires the django.contrib.messages application for the toolbar to work. See Enable messages for how to enable it.
New Page Types¶
You can now save pages as page types. If you then create a new page you may select a page type and all plugins and contents will be pre-filled.
Experimental Python 3.3 support¶
We’ve added experimental support for Python 3.3. Support for Python 2.5 has been dropped.
Better multilingual editing¶
Improvements in the django CMS environment for managing a multi-lingual site include:
- a built-in language chooser for languages that are not yet public.
- configurable behaviour of the admin site’s language when switching between languages of edited content.
CMS_SEO_FIELDS¶
The setting has been removed, along with the SEO fieldset in admin.
- meta_description field’s max_length is now 155 for optimal Google integration.
- page_title is default on top.
- meta_keywords field has been removed, as it no longer serves any purpose.
Plugin fallback languages¶
It’s now possible to specify fallback languages for a placeholder if the placeholder is empty for the current language. This must be activated in CMS_PLACEHOLDER_CONF per placeholder. It defaults to False to maintain pre-3.0 behavior.
language_chooser¶
The language_chooser template tag now only displays languages that are public. Use the toolbar language chooser to change the language to non-public languages.
Undo and Redo¶
If you have django-reversion installed you now have undo and redo options available directly in the toolbar. These can now revert plugin content as well as page content.
Plugins removed¶
We have removed plugins from the core. This is not because you are not expected to use them, but because django CMS should not impose unnecessary choices about what to install upon its adopters.
The most significant of these removals is cms.plugins.text.
We provide djangocms-text-ckeditor, a CKEditor-based Text Plugin. It’s available from. You may of course use your preferred editor; others are available.
Furthermore, we removed the following plugins from the core and moved them into separate repositories.
Note
In order to update from the old cms.plugins.X to the new djangocms_X plugins, simply install the new plugin, remove the old cms.plugins.X from settings.INSTALLED_APPS and add the new one to it. Then run the migrations (python manage.py migrate djangocms_X).
File Plugin¶
We removed the file plugin (cms.plugins.file). Its new location is at:
As an alternative, you could also use the following (yet you will not be able to keep your existing files from the old cms.plugins.file!)
Flash Plugin¶
We removed the flash plugin (cms.plugins.flash). Its new location is at:
Googlemap Plugin¶
We removed the googlemap plugin (cms.plugins.googlemap). Its new location is at:
Inherit Plugin¶
We removed the inherit plugin (cms.plugins.inherit). Its new location is at:
Picture Plugin¶
We removed the picture plugin (cms.plugins.picture). Its new location is at:
Video Plugin¶
We removed the video plugin (cms.plugins.video). Its new location is at:
Link Plugin¶
We removed the link plugin (cms.plugins.link). Its new location is at:
Snippet Plugin¶
We removed the snippet plugin (cms.plugins.snippet). Its new location is at:
As an alternative, you could also use the following (yet you will not be able to keep your existing files from the old cms.plugins.snippet!)
Twitter Plugin¶
Twitter disabled V1 of their API, thus we’ve removed the twitter plugin (cms.plugins.twitter) completely.
For alternatives have a look at these plugins:
Plugin Context Processors take a new argument¶
Plugin Context have had an argument added so that the rest of the context is available to them. If you have existing plugin context processors you will need to change their function signature to add the extra argument.
Apphooks¶
Apphooks have moved from the title to the page model. This means you can no longer have separate apphooks for each language. A new application instance name field has been added.
Note
The reverse id is not used for the namespace anymore. If you used namespaced apphooks before, be sure to update your pages and fill out the namespace fields.
If you use apphook apps with app_name for app namespaces, be sure to fill out the instance namespace field application instance name as it’s now required to have a namespace defined if you use app namespaces.
For further reading about application namespaces, please refer to the Django documentation on the subject at
request.current_app has been removed. If you relied on this, use the following code instead in your views:
def my_view(request): current_app = resolve(request.path_info).namespace context = RequestContext(request, current_app=current_app) return render_to_response("my_templace.html", context_instance=context)
Details can be found in Attaching an Application multiple times.
PlaceholderAdmin¶
PlaceholderAdmin now is deprecated. Instead of deriving from admin.ModelAdmin, a new mixin class PlaceholderAdminMixin has been introduced which shall be used together with admin.ModelAdmin. Therefore when defining a model admin class containing a placeholder, now add PlaceholderAdminMixin to the list of parent classes, together with admin.ModelAdmin.
PlaceholderAdmin doesn’t have language tabs anymore and the plugin editor is gone. The plugin API has changed and is now more consistent. PageAdmin uses the same API as PlaceholderAdminMixin now. If your app talked with the Plugin API directly be sure to read the code and the changed parameters. If you use PlaceholderFields you should add the mixin PlaceholderAdminMixin as it delivers the API for editing the plugins and the placeholders.
The workflow in the future should look like this:
- Create new model instances via a toolbar entry or via the admin.
- Go to the view that represents the model instance and add content via frontend editing.
Placeholder object permissions¶
In addition to model level permissions, Placeholder now checks if a user has permissions on a specific object of that model. Details can be found here in Permissions.
Placeholders are prefillable with default plugins¶
In CMS_PLACEHOLDER_CONF, for each placeholder configuration, you can specify via ‘default_plugins’ a list of plugins to automaticaly add to the placeholder if empty. See default_plugins in CMS_PLACEHOLDER_CONF.
Custom modules and plugin labels in the toolbar UI¶
It’s now possible to configure module and plugins labels to show in the toolbar UI. See CMS_PLACEHOLDER_CONF for details.
New copy-lang subcommand¶
Added a management command to copy content (titles and plugins) from one language to another.
The command can be run with:
manage.py cms copy_lang from_lang to_lang
Please read cms copy-lang before using.
Frontedit editor for Django models¶
Frontend editor is available for any Django model; see documentation for details.
Getter and setter for translatable plugin content¶
A plugin’s translatable content can now be read and set through get_translatable_content() and set_translatable_content(). See Custom Plugins for more info.
No more DB tablename magic for plugins¶
Since django CMS 2.0 plugins had their table names start with cmsplugin_. We removed this behavior in 3.0 and will display a deprecation warning with the old and new table name. If your plugin uses south for migrations create a new empty schemamigration and rename the table by hand.
Warning
When working in the django shell or coding at low level, you must trigger the backward compatible behavior (a.k.a. magical rename checking), otherwise non migrated plugins will fail. To do this execute the following code:
>>> from cms.plugin_pool import plugin_pool >>> plugin_pool.set_plugin_meta()
This code can be executed both in the shell or in your python modules.
Added support for custom user models¶
Since Django 1.5 it has been possible to swap out the default User model for a custom user model. This is now fully supported by DjangoCMS, and in addition a new option has been added to the test runner to allow specifying the user model to use for tests (e.g. –user=customuserapp.User)
Page caching¶
Pages are now cached by default. You can disable this behavior with CMS_PAGE_CACHE
Placeholder caching¶
Plugins have a new default property: cache=True. If all plugins in a placeholder have set this to True the whole placeholder will be cached if the toolbar is not in edit mode.
Warning
If your plugin is dynamic and processes current user or request data be sure to set cache=False
Plugin caching¶
Plugins have a new attribute: cache=True. Its default value can be configured with CMS_PLUGIN_CACHE.
Per-page Clickjacking protection¶
An advanced option has been added which controls, on a per-page basis, the X-Frame-Options header. The default setting is to inherit from the parent page. If no ancestor specifies a value, no header will be set, allowing Django’s own middleware to handle it (if enabled).
CMS_TEMPLATE context variable¶
A new CMS_TEMPLATE variable is now available in the context: it contains the path to the current page template. See CMS_TEMPLATE reference for details.
Upgrading from 2.4¶
Note
There are reports that upgrading the CMS from 2.4 to 3.0 may fail if Django Debug Toolbar is installed. Please remove/disable Django Debug Toolbar and other non-essential apps before attempting to upgrade, then once complete, re-enable them.
If you want to upgrade from version 2.4 to 3.0, there’s a few things you need to do. Start of by updating the cms’ package:
pip install django-cms==3.0
Next, you need to make the following changes in your settings.py
settings.INSTALLED_APPS
- Remove cms.plugin.twitter. This package has been deprecated, see Twitter Plugin.
- Rename all the other cms.plugins.X to djangocms_X, see Plugins removed.
settings.CONTEXT_PROCESSORS
- Replace cms.context_processors.media with cms.context_processors.cms_settings
Afterwards, install all your previously renamed ex-core plugins (djangocms-X). Here’s a full list, but you probably don’t need all of them:
pip install djangocms-file pip install djangocms-flash pip install djangocms-googlemap pip install djangocms-inherit pip install djangocms-picture pip install djangocms-teaser pip install djangocms-video pip install djangocms-link pip install djangocms-snippet
Also, please check your templates to make sure that you haven’t put the {% cms_toolbar %} tag into a {% block %} tag. This is not allowed in 3.0 anymore.
To finish up, please update your database:
python manage.py syncdb python manage.py migrate (answer yes if your prompted to delete stale content types)
That’s it!
Pending deprecations¶
cms.context_processors.media¶
cms.context_processors.media is now deprecated, please use cms.context_processors.cms_settings by updating TEMPLATE_CONTEXT_PROCESSORS in the settings
Using cms.context_processors.media will cause a DeprecationWarning to occur.
cms.context_processors.media will be removed in version 3.1. | http://docs.django-cms.org/en/latest/upgrade/3.0.html | CC-MAIN-2014-52 | refinedweb | 1,911 | 50.63 |
At provides a Lens for a structure
S to focus in
A at a given index
I.
If for a structure
S the focus
A can be indexed by
I then
At can create an
Lens with focus at
S for a given index
I.
We can use that
Lens to operate on that focus
S to get, set and modify the focus at a given index
I.
A
MapK<Int, String> can be indexed by its keys
Int but not for every index an entry can be found.
import arrow.core.* import arrow.data.* import arrow.optics.typeclasses.* val mapAt = At.at(MapK.at<Int, String>(), 2) val map = mapOf( 1 to "one", 2 to "two", 3 to "three" ).k() mapAt.set(map, "new value".some()) // MapK(map={1=one, 2=new value, 3=three})
By setting an empty value for a key we delete that entry by removing the value.
mapAt.set(map, none()) // MapK(map={1=one, 3=three})
Atinstances
Arrow provides
At instances for some common datatypes in Arrow that can be indexed. You can look them up by calling
At.at().
You may create instances of
At for your own datatypes which you will be able to use as demonstrated in the example above.
See Deriving and creating custom typeclass to provide your own
At instances for custom datatypes.
The following datatypes in Arrow provide instances that adhere to the
At typeclass. | http://arrow-kt.io/docs/optics/at/ | CC-MAIN-2018-17 | refinedweb | 237 | 71.75 |
How Does a Single Line of BASIC Make an Intricate Maze? 438.
Without the use of a loop!? (Score:5, Insightful)
What is
10 something: GOTO 10
if not an (endless) loop?
Re:Without the use of a loop!? (Score:5, Informative)
That's exactly what I thought... Maybe JameskPratt isn't a very good programmer.
Re: Without the use of a loop!? (Score:4, Funny)
Pratt by name . . .
Re:Without the use of a loop!? (Score:5, Funny)
Maybe he's trolling to see who will admit that they know BASIC.
Re: (Score:3)
What programmer doesn't know/can't figure out rudimentary BASIC?
Re:Without the use of a loop!? (Score:5, Interesting)
Indeed, it isn't exactly rocket science -- zillions of kids under 10 picked up the basics of BASIC from type-in programs in kids books and magazines back in the 80's.
What bugs me most is that instead of doing the obvious (making a binary tree maze) it's some weird artifact of how the / and \ combine on-screen that makes something that vaguely resembles a maze -- full of loops (no big deal) large winding sections without any junctions (bad), and isolations (terrible!).
Just for fun:
IBM PC users! You can modify the C64 program in the summary to both run on your micro and produce a binary tree maze with this simple change: PRINT CHR$(220 + INT(RND(1)*2) );
You won't be able to get the same effect with alternating forward- and back-slashes with something like PRINT CHR$(47 + INT(RND(1)*2)*45); as they don't connect at all -- neither on the same line nor between lines.
Re:Without the use of a loop!? (Score:5, Interesting)
A binary tree maze algorithm will generate a "perfect maze" (no loops, isolations, and only a single path between any two cells), though you need a long hallway along two sides (depending on which edges you use for walls).
Mazes with square cells share edges, so by assuming some rules about the outside walls of a maze, you can represent each cell in a maze with only two bits. You need only store, for example, just the south and west walls of each cell.
To make a binary tree maze, first assume an outer wall and a long hall (no south walls) in the first column, and along the bottom row (no west walls). For all remaining cells, randomly add a west or south wall. You don't need any information about adjacent cells -- just flip a coin and draw a wall for each remaining cell. This will produce a "perfect maze". It's pretty cool.
The code I posed will generate a binary tree maze, though it won't show the two long halls. (In this case, the program uses west and south walls, so the halls will be the in the first column and the along the bottom row.)
The lameness filter doesn't want me to show you an example. Still, it's pretty easy to make a nice binary tree maze generator yourself. Give it a try and you'll see how it works.
For fun, you can make four binary tree mazes and arrange them so that you have two long halls (one East to West, the other North to South) intersecting at the center of the maze, just by choosing which pair of walls to randomly generate in each quadrant. It makes a much more interesting looking maze without adding much complexity (just figure out which quadrant the current cell is in) and retaining all of the properties of a perfect maze.
I hope that helps.
Re:Without the use of a loop!? (Score:5, Interesting)
Try something like this. (Keeping with the BASIC theme)
10 CLS
20 W = 10
30 H = 10
40 RANDOMIZE TIMER
50 FOR I = 1 TO W: PRINT " __"; : NEXT I
60 PRINT ""
70 FOR I = 1 TO H
80 PRINT "| ";
90 FOR J = 1 TO W - 1
100 IF INT(RND(1) * 2) = 0 THEN PRINT " __"; ELSE PRINT "| ";
110 NEXT J
120 PRINT "|"
130 NEXT I
140 PRINT "|";
150 FOR I = 1 TO W - 1: PRINT "__ "; : NEXT I
160 PRINT "__|"
Lines 20 and 30 specify the width and height of the maze
Lines 50 and 60 draw the north outer wall of the maze
Lines 70 - 130 draw the maze by randomly drawing either a west or south wall.
Line 80 draws the first cell in a row, which won't have a south wall, to make a long empty hall
Line 120 draws the east-most outer wall at the end of each row
Lines 140 - 160 draw the last row, just a long empty hall.
You'll see that the maze has no loops or isolations. Every cell is reachable from every other cell by a single path.
Hope that helps. Happy maze making!
Re: (Score:3)
I can't think of any processors that don't have a JUMP or equivalent. So, assembly/machine code.
Intercal has COME FROM, which is basically the same thing.
Re: (Score:2)
[slick salesman voice] This is not your grandchild's looping mechanism! [/slick salesman voice]
Re: (Score:3)
Re:Without the use of a loop!? (Score:5, Informative)
No shit, and it is not a labyrinth either. It is just randomly printing forward slashes and backlashes.
Re:Without the use of a loop!? (Score:5, Insightful)
No shit, and it is not a labyrinth either. It is just randomly printing forward slashes and backlashes.
"an intricate combination of paths or passages in which it is difficult to find one's way or to reach the exit."
it is that. it's just not very amazing at all if you describe it as printing \ and / randomly.
Re: (Score:2)
it's just not very amazing at all if you describe it as printing \ and / randomly.
You are really going to break the author's heart if you keep that up.
It's hard to look at this story and not feel that it's a base case in an inductive proof that refutes the existence of art.
Re:Without the use of a loop!? (Score:5, Interesting)
I think there is a bit of a story in the fact that while in function, it is extremely simple though in result/appearance it creates what most perceive to be a complex maze of passages. The code puts out random positive space objects while the mind sees a single, complex negative space.
It sort of reminds me of similar little tricks used to generate landscapes and other such things... mandelbrot comes to mind.
Re:Without the use of a loop!? (Score:5, Funny)
The code puts out random positive space objects while the mind sees a single, complex negative space.
Sadly, that's the way I'm seeing slashdot these days...
Re:Without the use of a loop!? (Score:5, Insightful)
It sort of reminds me of similar little tricks used to generate landscapes and other such things... mandelbrot comes to mind.
Except that the Mandelbrot set, for example, really is much, much more interesting. It actually has a great deal of sophisticated structure, that's highly chaotic (in both typical and mathematical senses of the word) but not random at all. Not at all comparable to this example, whose output has no real structure at all, but just exploits the tendency of the human brain to find patterns whether or not they exist.
Re:Without the use of a loop!? (Score:5, Funny)
Much like a televangelist or politician then.
Re: (Score:3)
Firstly, the actual maze produced isn't random but is a visualisation of the pseudo-random algorithm used in C64 basic. Who's to say that this doesn't contain structure just as complex as that of the mandelbrot set?
Doesn't matter. Try it with a different PRNG, or a TRNG, and you'll get the same maze-like effect, because the effect comes from the pattern-matching ability of the human mind, not from any real patterns in the slashes.
Secondly, the mandelbrot set may not really contain the structures that we see at all. All those lovely spirals and so-on might just be floating-point artifacts. No-one knows for sure.
Not true. The colors are representations of how many iterations it takes for the point to escape the unit circle (which shows that its absolute value will increase without bound). In portions of the edges of the set (the set itself is the points which remain bounded -- those are indeed har
Re:Without the use of a loop!? (Score:5, Insightful)
It's called a display hack [wikipedia.org]. They're at least as old as the oscilloscope, and have always been a mainstay of the demoscene. The book provides little actual relevant history about the context of this snippet in that regard, only noting that the snippet itself derives from the C64 User's Manual.
Somewhat dismayingly, the bulk of the text ponders on criticism that presumes an intentional, carefully-planned artist:
10 PRINT picks up on aspects of "Mouse in the Maze." Its output is a regular arrangement of "walls" in a grid—akin to the display of that earlier program and similar to the arrangement of the stereotypical laboratory maze. "Mouse in the Maze" does not present the compelling creation of an inspired Daedalus, but a behaviorist experiment. This maze is a challenge to intelligence—not, however, a romantic, riddling intelligence, but a classically conditioned, animal kind. It also brings in the idea of the scientist, who may be indifferent to the struggles of the creatures lost in the maze.
This manner of thinking, now put on display nakedly in the context of something completely mathematical and involving no relevant human imagination, can plainly be seen to be philosophically inconsistent. The author has said that a very simple natural phenomenon is influenced by a complex work of art (specifically a TX-0 game from twenty or so years earlier), which indicates a profound metaphysical error.
Certainly it is worthwhile to talk about chaotic functions (like the R pentamino in Conway's Game of Life, in addition to the display hacks already mentioned) but attempting to critique them as if they were part of the artistic canon is intellectually dishonest.
Re:Without the use of a loop!? (Score:5, Funny)
The code puts out random positive space objects while the mind sees a single, complex negative space.
I don't even see the random positive space objects anymore. I just see blonde, brunette, redhead...
Not even that (Score:5, Insightful)
It certainly has the intricate path part down, but most people would take issue with a "maze" that lacks a beginning, end, or any guarantee that you can get from point A to B even if you consider obvious closed loops out of bounds.
Re: (Score:3)
Re: (Score:3, Informative)
The difference between a maze and a labyrinth is that the goal of a maze is to get from the entrance to the exit. The goal of a labyrinth on the other hand is to get to the center. If there is no entrance and there is no exit, it isn't a maze by strict definition, but a set of paths.
Re:Without the use of a loop!? (Score:4, Informative)
No shit, and it is not a labyrinth either. It is just randomly printing forward slashes and backlashes.
I disagree, I think this finally proves the existence of god.
;)
Re: (Score:2)
What is 10 something: GOTO 10 if not an (endless) loop?
Well, in certain dialects of Forth, you'd probably be able to write it using tail recursion. And it would be probably slightly shorter.
:-)
Re:Without the use of a loop!? (Score:4, Insightful)
Re:Without the use of a loop!? (Score:5, Insightful)
And most importantly - its not a particularly amazing piece of code. I am not a programmer, but know how to write basic stuff in a few languages - and i do not find a TWO LINE LOOP that fills the screen with a choice between two characters that make up something that LOOKS LIKE A MAZE, but is not necessarily navigable not a least bit amazing.
Re:Without the use of a loop!? (Score:4, Informative)
That's be cause you don't appreciate the context in which this code came to exist. Back in the early eighties, to be able to generate such visually impressive and complex looking imagery with so little code, was quite an amazing thing. I, for one, wish I would have known that bit of code back then as a ten year old. It certainly would have beaten my usual "10 PRINT "DAN WAS HERE!!! "; 20 GOTO 10" that I would type into the C64s, TI-99/4As, Atari 800s, and other computers on display at K-Mart and Sears.
For the sake of completeness, here is a version that works with the syntax (and character set) of another home computer of the era, the TI-99/4A
10 PRINT CHR$(INT(RND+.5)*45+47);
20 GOTO 10
The code is a little more complex because the forward and backward slash characters are not contiguous in the TI's character set (47 and 92). The result visually isn't as good because the TI's character glyphs are more spaced out than the C64's. However it does work - I tested it in the emulator (with standard TI BASIC, doesn't required Extended BASIC).
Re:Without the use of a loop!? (Score:5, Interesting)
A simple addition makes the TI-99/4A version look visually just like the C64's. That is to simply define the forward and backward slash characters to look more the C64's and span the whole area of the character's bitmap.
10 CALL CHAR(47, "C0E070381C0E0703")
20 CALL CHAR(92, "03070E1C3870E0C0")
30 PRINT CHR$(INT(RND+.5)*45+47);
40 GOTO 30
Finally, if we're going to go to the trouble of defining character images, then we might as well use contiguous character codes so we don't need the extra math. We could use the C64's exact values, however the TI's character set only has 128 characters. So we'll use values 100 less than the C64 version. Also, the TI rounds floating values to integers, whereas the C64 simply truncates them. So we don't need to add
.5 to the random value.
10 CALL CHAR(105, "C0E070381C0E0703")
20 CALL CHAR(106, "03070E1C3870E0C0")
30 PRINT CHR$(105+RND);
40 GOTO 30
Re:Without the use of a loop!? (Score:5, Informative)
And finally, here's a screenshot in case anyone actually cares what the TI version looks like. [dexsoft.com]
Re:Without the use of a loop!? (Score:4, Informative)
Actualy, it absolutely is just one line of code. You are confusing the number of statements with the number of lines. In BASIC, as in many languages, you can have multiple statements and operation in a single line of code. Those statements do indeed however constitute an infinite loop, however.
Re:Without the use of a loop!? (Score:5, Insightful)
Re: (Score:3)
This would be true if it were not for the pre-processor. You cannot, for example #include multiple external files on the same line or have multiple #defines on the same line. As far as "going that route" goes, the only route I took was making factually correct statements to correct the factually erroneous ones repeated far too many times on this subject. This isn't open to interpretation, unless you happen to be a C interpreter* that is
;-)
* B
Re:Without the use of a loop!? (Score:5, Informative)
main() { ten: printf("%c", (rand()%2)?47:92); goto ten; }
The preprocessor include directive is on a separate line, but that's really not part of the program.
Re: (Score:3)
It might generate a warning on some compilers, but it's a perfectly valid C program. In fact, since this program uses rand without declaration, it might as well use printf.
Nothing prevents one from doing this, though:
int rand(void); int printf(const char * restrict f,
...); main() { ten: printf("%c", (rand()%2)?47:92); goto ten; }
(Remove the "restrict" before "f" for C89)
In general, though, ISO C doesn't require translators (the technical name the ISO uses for C compilers/interpreters) to accept lines gre
Re: (Score:3)
OK, now it's clear that you have absolutely no idea what you're talking about -- you might want to read the C standard, or at least test it on a compiler.
If you're interested to learn, here's a general explanation:
The function declarations usually present in header files just tell the compiler what are the parameters accepted by the function, and what is the function return value. In C (not C++), these declarations are not required. If a function with no declaration is called, the compiler/interpreter/whate
Re: (Score:3)
I was thinking of posting something like the GP's post but after reading yours, I went to check and you're right. Spectrum Basic had multi-statement lines. ZX81 basic didn't though so there may be some validity though it can rightfully be regarded as very far from a standard basic with many missing features.
Re: (Score:3)
I accept your apology.
Re: (Score:3)
Note the second paragraph of that page, where it mentions that the version of Sinclair BASIC used on the Spectrum was an *update* of what was used in the ZX80 / ZX81 (which was also called Sinclair BASIC funnily enough). Also note that I mentioned *1981* and that the Spectrum 16K came out in *1982* . Get it now?
Re:Without the use of a loop!? (Score:4, Informative)
Re: (Score:2)
Sad day for slashdot... (Score:5, Insightful)
...when the summary does not know what a loop is.
Re:Sad day for slashdot... (Score:5, Funny)
Re:Sad day for slashdot... (Score:5, Interesting)
Also, it can't string together a single grammatically correct sentence. Complete failure on both technical and English levels!
The book is, however, quite interesting (just go straight to the open-access PDF and skip the mediocre Slate article).
No loop? (Score:5, Insightful)
No editors with programming experience perhaps.
The basic definition of a loop is a GOTO to a previous address! All the rest is syntax and optimisation.
Re: (Score:2)
Just missing BASIC experience...like I had in the 70s.
Re: (Score:2)
and it's not even a single line.
Would it count anyway? Including a library function that implements a PRNG algorithm hardly sounds like "a single line of BASIC"...
(Not criticizing the book, which I've never read -- it may be a great book for all I know.)
Re: (Score:2)
Yes, it would, if only because RND is an official ANSII BASIC statement, not an external library. Common people, all this stuff is pretty basic
.... ;-)
Re:No loop? (Score:5, Informative)
Nobody knows that, because it is untrue. The
: is a statement separator, not a line seperator. That 10 you see is the line number. Notice that there are no other line numbers. Make an error on either side of the colon and the interpreter will give you the exact same complaint: Syntax error in line 10. You can verify this by looking for the line " In BASIC it's used as a separator between the statements or instructions in a single line." on Wikipedia [wikipedia.org], or use your Google-Fu to verify it thousands of other ways.
Re: (Score:2)
10 INPUT "PLEASE INPUT Y OR N: ", A$
20 IF A$ "Y" AND A$ "N" THEN PRINT "INCORRECT": GOTO 10
The "GOTO 10" will only be executed if the condition is met. This is what early BASIC programmers had instead of if statements that supported blocks.
10 ... : GOTO 10 is a loop (Score:5, Informative)
It's very cool the way this code draws a maze, but there's obviously a loop there.
(And it's “without” not “with out”, and “complicated” not “complicate”.)
Re: 10 ... : GOTO 10 is a loop (Score:5, Interesting)
it's not a maze, it's a pattern of random forward and backward slashes, "/" and "\". There's no guarantee that a path exists anywhere near the top to anywhere near the bottom. In fact, because it's random, you'd be blocked off at some point.
Re: (Score:2)
Re: (Score:3)
In fact, because it's random, you'd be blocked off at some point.
Nonsense. See: Binary tree mazes.
Also, I recommend that you look at other maze generation algorithms (especially Eller's Algorithm) as you can easily create a random yet solvable maze where there is exactly one path between any two cells -- no loops or isolations. In the case of Eller's Algorithm, you can create a random maze of any length that has this property without keeping the entire maze in memory -- just a single line!
Without the use of a loop? (Score:3, Informative)
That....is.....a loop.......
Yes Captain (Score:2, Funny)
that's what our sensors are picking up.
Some minor deficiencies (Score:5, Insightful)
create a complicated maze with out the use of a loop
1. This is not necessarily a maze. It's noise. At best.
2. It's "without", not "with out"
3. There is a loop
Re: (Score:2, Informative)
Re: (Score:2)
Re: (Score:2)
The Slate article does make clear that this only works on something with the old Commodore 64 character set (PETSCII). And that it is a loop.It's not exactly a great article, but it does get these things right.
it would work on anything with the right type of font. if you want to try it on windows cmdline them from prefs select raster fonts and 8x8 pixel font.
(yeah I tested.. with a javascript script of all things, ugh)
Re: (Score:2)
Goto Makes a Loop (Score:3)
Re: "it manages to create a complicated maze with out the use of a loop"
Enterprise Java Version (Score:5, Funny)
import java.io.IOException;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Collections;
import java.util.Map.Entry;
import java.util.Random;
import java.util.SortedMap;
import java.util.TreeMap;
public class Maze {
private final WallFactory<Double> wallFactory;
private final EntropyGenerator entropyGenerator;
public Maze( WallFactory<Double> wallFactory, EntropyGenerator entropyGenerator ) {
this.wallFactory = wallFactory;
this.entropyGenerator = entropyGenerator;
}
public void visit( MazeVisitor visitor ) throws MazeException {
while( true ) {
MazeWall wall = wallFactory.createMazeWall( entropyGenerator.getNewEntropyValue() );
wall.visit( visitor );
}
}
public interface MazeWall {
* @param visitor
* @throws IOException
*/
void visit( MazeVisitor visitor ) throws MazeException;
}
public static class LeftDiagonalWall implements MazeWall {
@Override
public void visit( MazeVisitor visitor ) throws MazeException {
visitor.visit( this );
}
}
public static class RightDiagonalWall implements MazeWall {
@Override
public void visit( MazeVisitor visitor ) throws MazeException {
visitor.visit( this );
}
}
public interface MazeVisitor {
void visit( LeftDiagonalWall leftDiagonalWall ) throws MazeException;
void visit( RightDiagonalWall rightDiagonalWall ) throws MazeException;
}
public interface WallFactory<T> {
* @param value
* @return the MazeWall
* @throws MazeException
*/
MazeWall createMazeWall( T value ) throws MazeException;
}
public static class StrategyWallFactory<T> implements WallFactory<T> {
private WallRepartitionStrategy<T> wallRepartitionStrategy;
public StrategyWallFactory( WallRepartitionStrategy<T> wallRepartitionStrategy ) {
this.wallRepartitionStrategy = wallRepartitionStrategy;
}
@Override
public MazeWall createMazeWall( T value ) throws MazeException {
Class<? extends MazeWall> wallClassForValue = wallRepartitionStrategy.getWallClassForValue( value );
try {
return wallClassForValue.newInstance();
} catch( InstantiationException | IllegalAccessException e ) {
throw new MazeException( "Cannot create MazeWall instance", e );
}
}
Python version (Score:5, Interesting)
Re: (Score:2)
Re: (Score:2)
Come now, that's hardly Enterprise Java without a few JDBC connections.
;)
Re: (Score:3)
Re:Enterprise Java Version (Score:5, Informative)
Plagiarizer. You stole this from reddit -- from the same post linked from Nick Montfort's blog.
Enterprise Java Version: [reddit.com]
You shouldn't take credit for the work of others. That +5 funny is a filthy dirty lie.
Re: (Score:3)
Re:Enterprise Java Version (Score:4, Interesting)
Actually, when the code is idiomatic, it is a reflection on that language/frameworks that go with it. Having spent a bad 5 years in enterprise java trenches I can vouch for the realism of that code. It gave me flashbacks. I'm still fucking shivering.
Re:Enterprise Java Version (Score:4, Funny)
Perl version: Search CPAN, someone's bound to have written a maze module.
Without looping? (Score:2)
How does this not use a loop?
Perl analogue (Score:5, Interesting)
Don't have a Commodore Basic interpreter? this Perl 1-liner will do the same thing:
print ["/","\\"]->[rand(2)] while 1;
It has no start or end point, and for two arbitrary points you can't guarantee that a path exists.
Re: (Score:2)
You beat me to it. Even sweeter.
Really? (Score:5, Insightful)
Frontpage slashdot story with a 10 GOTO 10 and saying it's not a loop?
Dudes, just what the fuck. I ask you that.
Re: (Score:2, Funny)
It's a step up from the plastic on Mars story a few days ago.
Re: (Score:3, Insightful)
What the fuck? I'll tell you what the fuck... Slashdot as it stands today is a sad, pale reflection of the Good Slashdot of Old.
The focus isn't "News for Nerds" anymore, it's "Bash Apple Good... and oh, here's some code too."
A slow day on /. ? (Score:2)
1) It is an endless loop created by the GOTO command.
2) Is it a maze or does it just look like one? There is no indication that it actually creates a maze each and every time. It is more likely a pseudo random pattern that LOOKS like a maze.
Re: (Score:2)
Is it a maze or does it just look like one?
It is a maze. It doesn't necessarily have exactly one solution (It probably has more than one). It doesn't necessarily have any solutions.
The loop never seems to terminate, so it seems that the maze will keep getting larger until the program is manually aborted
Multi-Fail (Score:4, Interesting)
Re:Multi-Fail (Score:5, Interesting)
The article reads to me like a sophomore-level paper deconstructing some insignificant piece of drivel and claiming great insights into human nature.
"What can this one line -- '10 PRINT,' to use the authors' shorthand -- teach us about software, and culture at large?"
Damn! And that's just the review, I can't even imagine what the actual 294-page book must be like. Next up I expect a 500-page treatise on Vogon poetry.
/., in collaboration with the Erowid Vault (Score:2)
80s Flashback (Score:3)
I remember doing that in 1980something on the PET (maybe not that line, but the logic was the same). IIRC it was a type-in along with a bunch of other cheap BASIC graphics routines in a Creative Computing - later I'm sure it showed up in RUN or Transactor for the VIC/64.
It was cool for maybe a couple hours... along with thoughts of what games could I use it with (that's how we developed game ideas old-school style, starting with cool little snippets like this.)
Tricks with Slash and Backslash (Score:2)
Watching the video it occurs to me that the interesting part is that if you randomly print out slashes or backslashes endlessly, you create an endless "maze". It works particularly well on the c64 because the printable graphics set includes a slash and backslash that have no spacing around the character. But you can do the same thing in a terminal like this:
perl -e 'while (1) { print rand() >
.5 ? "/" : "\\" }';
Although depending on your font it won't look as compelling as the c64 version
Re:Tricks with Slash and Backslash (Score:4, Funny)
perl -e 'while (1) { print rand() >
.5 ? "/" : "\\" }';
Quick, claim it doesn't have a loop and write a book.
:)
Bah why write the code... (Score:4, Informative)
when there's a perl module for that: [cpan.org]
A meditation (Score:4, Informative)
From page 4 of the book:
In short, this is not a programming book, but it appears to be a book of cultural anthropology about programming. Or perhaps a meditation which starts with one simple starting point and branching out in many different directions. Criticizing the program "10 PRINT" as trivial rather misses the point, I should think.
A simple Linux port (Score:3, Insightful)
strings
/dev/urandom|tr -dc '/\'
Re:A simple Linux port (Score:5, Insightful)
Sorry, what was I thinking? This is obviously more elegant:
tr -dc '/\' </dev/urandom
Diablo (Score:4, Funny)
Wow. Who would have known that the code for Diablo is so simple.
i prefer c over basic (Score:3, Interesting)
Book not so bad (Score:3)
The book is worth reading, it retells many things from the beginning of personal computing, exploring subjects along the way. the 10 PRINT one-liner is the motivation but not the topic.
Cheers.
Reminded me of DataGlyphs (Score:5, Informative)
It's just randomly printing forward and backward slashes, which line up because of the font. It's nifty, but hardly amazing.
And in fact, it appears Slashdot ran an article on this a decade ago when it was called DataGlyphs [slashdot.org].
Re:A maze (Score:2)
But what exactly is a maze? If you knowingly pick a valid start and end point, doesn't it become one? Isn't a maze basically a bunch of twisty lines designed to obfuscate the path from start to finish?
Re: (Score:2)
this "goto recursion" does not crash, because there is no stack to be able to jump back.
Re: (Score:3)
It eventually fills up the galaxy with ascii chars and the world ends.
No, not Linux too ... (Score:2)
I guess you've never looked at the Linux source code. There certainly are a (very) few gotos, but it is certainly not "filled" with them. They are very rare indeed.
Re: (Score:3)
Here you go: [sorotokin.com]
It's just below the java applet.
Re:Record breaking (Score:4, Funny)
It seems as if every single user on Slashdot felt they had to chime in to alert the world that 10 GOTO 10 is in fact a loop, as if everybody else hadn't already made that point.
The thing is, GOTO 10 is a loop. Therefore it's not without a loop. QED. | http://developers.slashdot.org/story/12/12/01/1847244/how-does-a-single-line-of-basic-make-an-intricate-maze?sdsrc=nextbtmprev | CC-MAIN-2015-32 | refinedweb | 5,089 | 64 |
This is a client library for Apple’s push notification service. It is not the first such library for Python, but, as is often the way, the existing options didn’t quite meet our needs:
An APNs client is by nature stateful. The default apns-worker backend uses Python threads to asynchronously process a queue of messages to send to the service. Most users will want to maintain a global ApnsManager instance to process messages. Note that if your own program is threaded, you may need to take care to create this global instance safely.
from apns_worker import ApnsManager apns = None def init_apns(key_path, cert_path): """ Call this once at program init time. """ global apns apns = ApnsManager(key_path, cert_path) def send_badge(token, badge=1): """ Badge the app on a single device. """ apns.send_aps([token], badge=badge). | https://pypi.org/project/apns-worker/ | CC-MAIN-2016-44 | refinedweb | 135 | 61.77 |
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I'm sure you thought about this, but in cases where you're using the RackAwareStrategy, the dynamic snitch will need to yield consistent results, otherwise, you could create situations where the natural endpoints for a token keep changing depending on network performance.
> but that is actually solving a different problem.
I think the key takeaway from Vivaldi is using a coordinate system, so that you don't have to store latency information for every endpoint you've ever communicated with.
> I'm sure you thought about this, but in cases where you're using the RackAwareStrategy, the dynamic snitch will need to yield consistent results
Would it be possible to have the snitch store its coordinates in the system table, so that during bootstrapping, it looks at gossip latency, tunes its coordinates, and then persists them forever? It rules out using endpointsnitches to dynamically adjust position based on load on a machine, but I think that might be better solved by load balancing anyway.
I think what we want to do is have the "dynamic" part just apply to endpoint-sorting, and leave replica determination up to the strategy in terms of DC + Rack.
A crappy alternative would be run-time loading of a new snitch (which could be hard-coded to sort whichever way).
Things can get complicated when there is a network outage and the network being smart trys to re-roue the traffic in the more expensive route, in which case the whole equation changes.... I am not sure if this sorting has to be done only once when the node comes up? even then we dont know if during bootstrapping there was a network outage.....
Once the other nodes come back up they'll get some traffic still b/c of RR (and of course writes), so it will quickly figure out that the cheap route is back.
>I think what we want to do is have the "dynamic" part just apply to endpoint-sorting, and leave replica determination up to the strategy in terms of DC + Rack.
I think this could be good for more than network distance, it would also help a cluster route around a node that is slow (either permanently or temporarily). In addition to being in compaction, a node that has just been restarted and therefore has empty caches should be routed around (but not completely, since it needs traffic in order to warm its caches).
Right, you want to adapt to "effective reply time" not just the network part. That is why I don't think the vivaldi stuff helps much since it's trying to solve a static network question instead.
Wouldn't sorting the endpoints by their phi value in the FD work well since FD is already adaptive?
The phi value is only effected by gossip, right? I think this would only work (or work much better) if it took into account rpc response times.
Right, we've seen lots of instances of nodes that have enough cpu to spit out gossip heartbeats, but not enough that they can handle a normal complement of requests.
I suspect the phi algorithm can be modified to satisfy the "at N most per second" criterion wrt RPC calls, but I'll have to experiment a bit to be certain.
It looks like the phi algorithm can work for this. It's simple to replace timestamps with latency values, and then use an arbitrary value when calculating the phi score for a host. The main problem is calculating phi is less than free, and doing so for each request to determine the least latent endpoint will be too expensive. We can get around that by doing it up front when we add a sample and keeping a cache of the scores, but that means we'll have to add samples fairly infrequently, or at least batch the updates so the mean only has to be calculated once per batch.
right, even for something simpler than phi we'd want to sample, say, 10x per second at most.
Here is a dynamic snitch that listens to read latencies from other machines, accepts at most 10 timings per second, and once per second calculates the phi value for all hosts it knows about. Comments and testing would be most welcome.
There's a problem with this snitch: once a machine sees a host and sorts it to the end, it will never read from that host again, meaning that it will never update that host's score, until such time that another host performs worse.
Updated patch resolves this by resetting all the timing windows once per minute, giving the 'bad' hosts a chance to recover.
(1)
combine
+ windows.putIfAbsent(host, new AdaptiveLatencyTracker(WINDOW_SIZE));
+ AdaptiveLatencyTracker tracker = windows.get(host);
to
+ AdaptiveLatencyTracker tracker = windows.putIfAbsent(host, new AdaptiveLatencyTracker(WINDOW_SIZE));
Even better: get, then putIfAbsent only if null, would avoid creating new ALT objects every time
(2)
receiveTiming isn't threadsafe. use AtomicInteger?
(3)
AdaptiveLatencyTracker doesn't look threadsafe either. definitely LBD isn't. I think just using a threadsafe queue like CLQ would work? (My fault for naming ASD a Deque, when it only really needs a Queue)
(4)
do we need unregister()? if not, let's drop that api
(5)
sortByProximity needs to return zero if both scores are null. even better, take a non-dynamic snitch and use the static topology when there is no score info yet (this would save us from sending data requests to another data center after every clear of the stats). So, rather than using DES directly in the config, maybe having a boolean for whether to wrap your regular snitch, with the dynamic one, is the way to go.
what if reset cleared scores, instead of latencies? this would result in a more gradual aging out of both slow and fast latencies as new ones were pushed in, which would make it more tolerant of brief hiccups where a mostly fast node had a couple slow responses. Feels more how phi was meant to work, to me.
(6)
+ if (address != FBUtilities.getLocalAddress()) // we only know about ourself
+ return addresses;
let's change this to an assert
(7)
deque.offer is more idiomatic than try/except in java
(8)
let's use a single timer for both update and reset
(9)
it's not completely clear to me that the phi code designed for telling "how long has been too long to wait for updates that are supposed to arrive at the same interval," applies well to latency information that arrives in bursts up to our max per interval. can you add some tests showing that it does the right thing, given several mixes of latencies?
Updates:
LBD is threadsafe. Not sure what I was smoking there.
Big Hammer latency reset is fine for now but I would like to have more graceful aging out of latencies so if you have latencies like .|.|... and we age out the || then it sorts to its "normal" place again without having to rediscover things from scratch.
Updated patch incorporating above suggestions.
+1 after minor clean up:
+ if (conf.dynamic_snitch == false)
+ return snitch;
+ else
+ return (IEndpointSnitch) new DynamicEndpointSnitch(snitch);
prefer Unable to render embedded object: File (conf.dynamic_snitch (and prefer positive conditions first, to avoid ") not found...else")
the cast should be unnecessary
personally I would go for a ?: here but if/else is ok
+ public void add(double i)
+
indent is wrong there
+ double exponent = (-1)*(t)/mean;
space b/t arithmetic operators here and everywhere else please
DynamicEndpointSnitchTest: several { need to be on new lines
Committed with cleanups.
Integrated in Cassandra #491 (See)
re-opening for backport to 0.6.5
Backport for 0.6.5. Requires -Dcassandra.dynamic_snitch=true to be added to the JVM options to enable.
Also includes improvements from
CASSANDRA-1296.
+1
[committed by Brandon]
Getting this test failure in 0.6:
[junit] Testcase: testSnitch(org.apache.cassandra.locator.DynamicEndpointSnitchTest): FAILED
[junit] null
[junit] junit.framework.AssertionFailedError
[junit] at org.apache.cassandra.locator.DynamicEndpointSnitchTest.testSnitch(DynamicEndpointSnitchTest.java:70)
fix patch attached to
1) r/m unused imports
2) fall back to subsnitch on score equality as well as no score at all
3) order lower scores first in proximity list
fix-v2 switches to EndPointSnitch (SimpleSnitch does not exist in 0.6), fixes order for "make host3 the worst" and adds missing assert.
Committed to 0.6 and trunk. Also worth noting that DES has been broken in trunk due to incorrectly calculating the probability (needs to be 1 - Math.pow) which I fixed also. We missed this because the tests were wrong.
Integrated in Cassandra #515 (See)
fall back to subsnitch on score equality as well as no score at all, fix probability calculation. Patch by jbellis and brandonwilliams, reviewed by brandonwilliams for
CASSANDRA-981
There seems to be a bug in the 0.6.5 DatabaseDescriptor.java. On line 629:
String dynamic = System.getProperty("cassandra.dynamic_snitch"); if (dynamic == null || Boolean.getBoolean(dynamic) == false) epSnitch = snitch; else epSnitch = new DynamicEndpointSnitch(snitch);
Boolean.getBoolean(String s) checks for System.getProperty(). I think the code should read:
if (Boolean.getBoolean('cassandra.dynamic_snitch') == false) epSnitch = snitch; else epSnitch = new DynamicEndpointSnitch(snitch);
A workaround is to supply JVM properties like "-Dcassandra.dynamic_snitch_enabled=true -Dcassandra.dynamic_snitch=cassandra.dynamic_snitch_enabled"
Has anyone succesfully run with 0.6.5 and the dynamic snitch?
This stuff is actually more broken than I thought..
It only works with one keyspace, since the DynamicEndpointSnitchMBean is registered per keyspace, which is not allowed.
Next, the DynamicEndpointSnitch doesn't work with the RackAwareStrategy, since that one checks the following:
if (!(snitch instanceof EndPointSnitch)) throw new IllegalArgumentException(("RackAwareStrategy requires EndPointSnitch."));
And breaks, since the DynamicEndPointSnitch extends AbstractEndpointSnitch and not EndPointSnitch. RackAwareStrategy should check for the interface IEndPointSnitch.
oh, that's funny, in an unfortunate way. you're right about the getBoolean. fixed in r1000877 on 0.6 branch.
you're right about the second part too, but that was already fixed in
CASSANDRA-1429 (also on 0.6 branch).
Stu suggested Vivaldi positioning (), but that is actually solving a different problem. (How do you estimate network distance, without actually talking to the node in question?) Since we are in near-constant communication with all the nodes in the system, we should be able to leverage that for a solution that is both simpler and quicker to adapt to changing conditions.
This problem seems similar to the sliding window we maintain of heartbeat times for failure detection, but this seems too heavyweight to apply when processing thousands of responses per second. Perhaps restricting the sampling to "at most N per second" would work, although I'm not sure if the phi algorithm can work on samples that don't occur at evenly-spaced intervals. | https://issues.apache.org/jira/browse/CASSANDRA-981 | CC-MAIN-2017-09 | refinedweb | 1,805 | 54.02 |
Memory Profiling: The Object Graph View
today’s tutorial on the Windows Phone Performance Analysis tool, I’m focusing on the Object Graph view, which shows the graph of objects that are reachable from any instance of an object.
It can be helpful to think of the object graph as a set of connected object instances—the nodes are the object instances and the edges are the references between the instances. The garbage collector (GC) uses the object graph to determine instances in memory that are still reachable, that is, that are live and referenced by others. The instances might be needed by the program, or they might be no longer reachable and therefore can be determined to be eligible for garbage collection. The object graph also is useful to the developer who wants to answer questions like “what other objects are being kept alive because of this particular instance?” and ”what is the amount of memory being used by the object graph rooted at this particular instance?” to help improve their app’s performance.
Computing the object graph
At any given point in time, there can be a large number of live object instances on the heap. We know that the intrusion to trace out the object graph that is reachable from each object instance can be time consuming; it adds to the size of the profile data that needs to be logged; it potentially can be wasteful (what if the instance for which the object graph was computed got garbage collected?); and it can significantly disrupt runtime performance. Consequently, the profiler computes object graphs only after a “full” GC (when the heap contents are comparatively stable), or after at least five GCs have occurred. That is, the profiler computes object graphs at a low frequency of intrusion. Five GCs is just the default and can be tuned in the Advanced Settings hive in the launch page. The following code snippet from the sample illustrates how information in the Object Graph view is represented.
A sample and the object graph
This sample app builds up a set of instances that are connected in various configurations: a cycle, a doubly linked list, and a double diamond. Consider the case of the cycle, as follows:
public class Element { public Element next; } public class Cycle { public static Element m_e; public Cycle() { m_e = new Element(); var e = new Element(); m_e.next = e; e.next = m_e; } } ... var c = new Cycle(); GC.Collect();
To keep the sample brief, we explicitly trigger a full GC after creating the cycle, which cues the profiler to compute the object graph.
The cycle of instances of Element, reachable from the static field m e, survives the garbage collection. If we select a time range after this (first) GC, and go to the Types view via the Retained Allocations category, we see two instances of the type Element as expected.
If we go to the Instances view, we see those two instances:
At this stage we can inspect the object graph that’s reachable from either instance. If we select the older instance (ID 4347) and navigate to the Object Graph view we see the following table:
Although most of the information is similar to the info in the Instances view, note the following: (1) the indentation in the Type Name column, (2) the asterisk at the end of certain Type Name entries, and (3) the Reference Count column.
The indentation indicates the referent. In this case, the Element with ID 4347 refers to the Element with ID 4348, and that 4348 in turns refers to 4347. During the profiler’s discovery of this graph, 4347 has been visited more than once, so forming a cycle with its referent. This is indicated with an asterisk at the end of the Type Name for that particular instance; no further paths through that instance will be expanded. Finally, the number of references (Reference Count) to each of the instances is one. This topology can be represented as follows:
We can apply this interpretation to a couple more examples.
Another example: doubly linked list
Consider the following snippet, which builds a double linked list of four Node instances.
public class Node { public int val; public Node prev; public Node next; public Node(int i) { val = i; prev = null; next = null; } } class DoublyLinkedList { // Roots for the list public static Node head = null; public static Node tail = null; public void add(Node n) { if (head == null) { head = n; tail = n; } else { tail.next = n; n.prev = tail; tail = n; } } public DoublyLinkedList() { for (int i = 0; i < 4; i++) { add(new Node(i)); } } } ... var dll = new DoublyLinkedList(); GC.Collect();
If we go to the Types view via the Retained Allocations category we see four instances of the type Node as expected:
The Instances view shows the four instances:
If we go to the Object Graph view, we see the objects reachable from the instance 4334:
If we collapse the entire hierarchy starting at the first row in the table and then expand it one row at a time, we can apply the same interpretation as in the cycle example, and we see a topology that maps to the following image:
Notice the following:
- The referents start from 4335. This is represented by the indentation in the Type Name column.
- Instance 4334, 4335, and 4336 form a cycle with their referents. At corresponding positions in the referent hierarchy, this is indicated with an asterisk at the end of their Type Name, and no further paths through them are expanded.
- Both instances 4335 and 4336 have two references pointing at them. This is reflected with a count of 2 in the Reference Count column.
A more complex example: double diamond
Let’s consider one more example. This time we’ll take a look at instances connected in a double diamond formation.
public class A { public B b; public C c; public int val;} public class B { public D d; public int val;} public class C { public D d; public int val;} public class D { public E e; public F f; public int val;} public class E { public G g; public F f; public int val;} public class F { public G g; public F f; public int val;} public class G { public G g; public F f; public int val;} class DoubleDiamond { // root for the diamonds. public static A a; public DoubleDiamond() { a = new A(); a.b = new B(); a.c = new C(); a.b.d = new D(); a.c.d = a.b.d; a.b.d.e = new E(); a.b.d.f = new F(); a.b.d.e.g = new G(); a.b.d.f.g = a.b.d.e.g; } } ... var dd = new DoubleDiamond(); GC.Collect();
If we go to the Types view via the Retained Allocations category, we see each of the instances of the types as expected:
The Instances view for type A shows its single instance:
When we go to the Object Graph view, we see all the objects reachable from that instance:
As before, if we collapse the entire hierarchy starting at the first row in the table and then expand it one row at a time, we can apply the same interpretation as in the previous cases and see a topology that maps to the following images:
Notice the following:
- The referents start from B (4340). This is represented by the indentation in the Type Name column.
- There’s more than one path leading up to D (4342) and G (4345). At corresponding positions in the referent hierarchy, this is indicated with an asterisk at the end of their Type Name, and no further paths through them are expanded.
- A has a reference count of 0 (there are no references pointing to it in this graph), both D and G have two references pointing to them, and the others have only one reference pointing to them. This is reflected by the counts in the Reference Count column.
Conclusion
The Object Graph view reports the graph of objects that are reachable from any particular object instance, and helps the developer visualize their connectivity. We can use this view to evaluate the consequence of any single instance being retained in memory, that is, consider object lifetimes in the context of the garbage-collected runtime. In a subsequent post that will conclude this series we will look at how to determine why an instance remains a live object.
This series shows you how to take advantage of the memory profiling feature of the Windows Phone Performance Analysis Tool. Related posts:
- Part 1: Memory Profiling for Application Performance
- Part 2: Memory Profiling: Launching, Graphs and Markers
- Part 3: Memory Profiling: The Heap Summary view
- Part 4: Memory Profiling: The Types View
- Part 5: Memory Profiling: The Instances View
- Part 6: Memory Profiling: The Methods View
Updated November 7, 2014 11:56 pm
Join the conversation | http://blogs.windows.com/buildingapps/2012/10/23/memory-profiling-the-object-graph-view/ | CC-MAIN-2015-48 | refinedweb | 1,480 | 56.49 |
November 24, 2014 at 8:11 pm
What is your preferred way to receive(or not) reports of typos and similar minor errors? Many thanks for this series
November 24, 2014 at 10:31 pm
I’m still reading along, but just a thought: do you think it would be helpful to provide references for further reading? For example, to explain Goedel? That way, even if you don’t want excessive “mathiness” to permeate the writing, readers would have an idea of where to look for more. Very enjoyable so far!
November 24, 2014 at 10:43 pm
…Russell, even. See? 😉
November 24, 2014 at 10:44 pm
@William: Twitter works fine. I’ll see it if you mention @BartoszMilewski.
November 25, 2014 at 2:21 am
So a point of precision here: I think you confuse denotational and categorical semantics a bit. I just checked back at the Moggi paper “Notions of Computation and Monads” and indeed he constrasts the approach there, which he describes as categorical semantics, to all three of denotational, logical, and operational accounts. Also, denotational semantics prior to Moggi already could deal with effects, just not as pleasantly — indeed, the discipline (from the Strachey standpoint, not the Scott one) was motivated by trying to understand languages like C, and it was in fact in Strachey’s work that the idea of lvals was first introduced!
For similar reasons, this statement is false: “In a pure functional language like Haskell all functions are pure. Because of that, it’s possible to give these languages denotational semantics and model them using category theory.” The falsehood is in the fact that we can also give imperative languages denotational semantics and model them using category theory (or rather, we model them using denotational semantics with borrowings from category theory — genuine categorical semantics get scary fast and aren’t used for ‘real sized’ languages as far as I know). Here, for example, is a paper on the denotational semantics of ANSI C (as implemented, of course in Haskell :-P).
I think that densem and cat theory (which are not the same — traditional densem is set theoretic) must be motivated not as the only way to do things, but as ways with certain advantages.
Here is a perhaps clearer way to argue things: denotational / categorical semantics can be much easier to reason about than operational ones. however, the link between denotational / categorical semantics and imperative languages is typically harder to establish than the link between imperative languages and their operational semantics. If we accept that we have a better way to talk about what programs “mean” then perhaps we should have languages that allow us to represent things closer to that way in the first place, and we should attempt to internalize their constructs (such as monadic effects) directly into those languages as much as possible.
November 25, 2014 at 6:19 am
I think that the debate around static/dynamic weak/strong typing debate misses the point. Explaining what typed and functions and what their advantages are won’t change a thing.
People use dynamic languages because it is simple and faster to get things running. Why is that? My hypothesis is that is is in big part because of culture. The Haskell world fosters a culture of complexity even for minor tasks.
For instance, watch the situation of command line parameter parsing, needlessly complex libraries, with poor documentation and example who won’t compile… Then compare it to python or ruby or clojure libraries…
Then you have the fact that Haskell is a relatively simple language by itself, but every library developer feels the need to bring in his own set of Language extensions. Hence you end up having a good bunch of Haskell variants to study.
Then you have things like pipes and conduit that do quite similar stuff (and apparently very commonly needed stuff) with dissimilar interfaces. Both are complex and you have to know both because they are pulled in by other libraries…
This complexity culture partially explains for me why people will prefer Ruby, Clojure, Python or even Java to Haskell (and Scala to a lesser extent).
Make simple things simple please…
PS: For now I am a happy Lisper (with typed clojure and its gradual typing). I’m really appreciating ocaml and F# these days and I’m considering pushing them at work. I abandoned the idea of pushing Haskell because I could only see a world of pain for my coworkers.
November 25, 2014 at 11:02 am
@sclv: I’m glad you are keeping me on my toes ;-). I have modified the offending sentence replacing “possible” with “easier” (that’s the great thing about blogs: you can improve on them).
As for denotational vs. categorical semantics, this is the kind of hair splitting I’d like to avoid. I think the key is your observation that “traditional densem is set theoretic.” I would argue then that “modern densem is categorical.”
November 25, 2014 at 11:13 am
@johann: I sympathize with your arguments, but what you’re complaining about is the prevailing practice in the Haskell community, which will hopefully improve with time, not the principle of strong typing. I’ve seen people throwing together shell scripts in Haskell in no time, using Haskell’s type inference to avoid any explicit typing. It feels like programming in a dynamic language, except when you make a mistake.
November 25, 2014 at 5:29 pm
unit :: a -> ()
unit _ -> ()
Second line should be:
unit _ = ()
November 25, 2014 at 5:34 pm
I’m not a fan of the phrases “strongly typed” and “weakly typed” because they are so often used to mean so many different things. I’ve heard and read ALL of the following meanings in casual conversations and academic papers
1) weak = dynamically typed, strong = statically typed.
2) Weak = lots of automatic coercions (e.g. JavaScript and C++), strong = relatively few (e.g. Scheme and Haskell)
3) Weak = undefined behavior/memory unsafe (e.g. C, Fortran, Pascal, and C++), strong = memory safe (most popular languages [ignoring FFIs and such])
4) Weak = relatively limited static type systems (e.g. all dynamically typed languages, but also C and Pascal), Strong = relatively rich type systems (e.g. Haskell and Scala). I guess by that definition Java and C# would be medium strong and Agda would be ultra strong. Or something.
5) Weak = effects aren’t tracked in types in any way, strong = effects are tracked in types
I read through this post and suspect you mean at least #4 but also maybe #5. But it’s not clear.
November 25, 2014 at 6:28 pm
Corrected! Thanks!
November 25, 2014 at 8:05 pm
Thank you for an interesting article and a really interesting blog.
The big problem I have with statically typed languages that I have experience with (mostly C and C++) is that they are inherently bad at handling dynamic data. That is data where the type of the data is not necessarily known beforehand. And I find that a whole lot of problems go into that domain.
How is this handled in Haskell? (While I have tried to learn Haskell I have yet to do anything above toy examples)
November 27, 2014 at 3:16 pm
@Ragnar,
Sorry for the divergence w.r.t the actual contents of the article. But on the topic of consuming data in a statically typed language, this is always problematic. If, as you say your data sources are truly dynamic and not know until run-time. You then have little choice but to parse the data and emit the data as an abstract syntax tree that represents the data, which you can then provide accessors over using a set of carefully chosen combinators or lenses maybe. If however you have a representative sample of the data set, then F# has a language feature called type providers which can help massively here. see,
or
for examples, I’m not sure of an equivalent of this in haskell although implementations may well exist.
November 28, 2014 at 8:40 am
[…] Types and Functions […]
November 28, 2014 at 12:07 pm
Type System applies rules to source code that are not covered by language (context free) grammar.
In other words, Type system looks like replacement for extensible and context sensitive grammar that covers user defined types and code.
Static program analysis is about applying (context sensitive) rules to source code, like grammar.
Another attempt of enforcing rules is C# using (resource) statement. Resources are created, used and disposed in ruled order, also like grammar.
We need tools that at compile time can check the rules about how to use resources or order of using library functions / object creating-using-disposal / assigning or checking nullable types before use / memory allocation-use-disposal etc.
November 30, 2014 at 3:01 am
[…] Types and Functions by Bartosz Milewski. […]
December 5, 2014 at 10:20 am
@sclv This is basically an aside, but the idea that denotational semantics means “interpret in a category” has become a pretty common one. For example, Carvhalo in “Execution Time of λ-Terms via Denotational Semantics and Intersection Types” says “The fundamental idea of denotational semantics is that types should be interpreted as objects of a category C and terms should be interpreted as arrows in C in such a way that if a term t reduces to a term t′, then they are interpreted by the same arrow.” I am sure if I tried I could dig up other people saying essentially the same thing.
I don’t know if I agree with this view: different people mean different things when they say “denotational semantics”–often what is meant is something like “Scott semantics.” In the context of logic, “denotational semantics” usually is differentiated from other kinds of models in that it models proofs and not just provability. That said, there is some strength to the “denotational is categorical view”–it gives a particular research direction for coming up with models that looks something like 1. figure what you need in the category to model your language 2. come up with a category with those features. This is explicitly the research direction taken by people like Lars Birkedal (or at least I have heard him describe his work that way) and seems to be what is going on with people like Samson Abramsky. So, although it might not be a universal perspective, it seems it would be be hard to argue it is a bad one.
Finally, the question of if “traditional denotational semantics” was categorical is a question of what “traditional denotational semantics” means. But if it is supposed to be early Scott, the answer is that although Scott avoided the use of categorical language I think it is pretty clear that he was motivated by categorical ideas. These appear explicitly in papers like “Data Types as Lattices” but I think these ideas were implicit in “Outline of a mathematical theory of computation.” Indeed, Scotts own version of history emphasizes the importance of category theory to the development of the lambda calculus, and describes his main contribution as the theorem that “The category of T0-topological spaces with an equivalence relation and continuous functions respecting equivalence is cartesian closed.” source
Anyways, as I said this is all an aside. How much you emphasize category theory vs other approaches is a matter of taste.
December 7, 2014 at 11:16 pm
@philipjf. My point was not that people don’t use terms loosely to mean many things. It is that the historic account given is misleading, and particularly if one turns to Moggi’s paper we see that he explains he is doing categorical semantics in contrast to denotational semantics!
@bartosz: Glad you took one edit. Appreciate your concerns about hair-splitting. Let me suggest one section that I still find misleading. In particular:
“What’s the mathematical model for reading a character from the keyboard or sending a packet across the network? For the longest time that would have been a conversation stopper. It seemed like denotational semantics wasn’t applicable saved denotational semantics, and made pure functional programs usable, but also shed new light on traditional programming.”
As discussed above, even sans monads, denotational semantics could tackle this stuff. So perhaps the following.
“For the longest time, the answer would have been somewhat convoluted. It seemed like denotational semantics was awkward for a considerable…”
And similarly I would suggest “and made pure functional programs much more usable”.
After all, we had a usable, if awkward IO story for Haskell even prior to monads. Much of Plotkin’s work on effects has been, in a sense, suggesting an alternate history in which Monads where not taken up so fulsomely, and asking what avenues we may have continued to go down instead. Such avenues, of course, end up being also very categorical, but in a somewhat different way.
December 8, 2014 at 4:26 pm
@sclv: All right, is it better now?
December 8, 2014 at 6:53 pm
Much! Appreciate you being responsive on this 🙂
December 8, 2014 at 7:25 pm
[…] Next: Types and Functions. […]
December 10, 2014 at 10:06 am
Well… I actually do sometimes. Usually it’s when the interface I am using is documented poorly, whether “poorly” means “underdocumented” or “overcomplicated”, or even both, as the case with pretty much any “asynchronous” API.
So I just imagine some sort of idealized behaviour, with sane invariants and pre-/post-conditions, write a toy implementation and then, amazedly, watch how destroyed objects keep sending events (with the sender being a null pointer at best), how EVENT_CONNECTION_DROPPED arrives before EVENT_MORE_DATA_ARRIVED, how some events are never reported/passed to me even though they clearly happen, and all such nonsense. After this I indeed start “just throwing lines of code and see what happens”, to learn crucial things that were left out from the documentation.
Denotational semantics is lovely and exciting, but most people actually prefer axiomatic semantics when trying to reason about correctness: I’d argue that the reasoning along the lines “those variables are guaranteed to have such and such values when the execution hits this point of code, so calling this routine with such and such parameters can’t cause any surprises, and after it returns, the program state will satisfy that and that condition” is not an application of operational semantics, and definitely not of denotational semantics. Surely, picking some particular mathematical objects will provide us with exactly the axioms we need to infer conclusions that are of interest to us but after we have realised that those axioms are the ones we need, we can we work just with them, without the “interpretation” in terms of those objects.
December 10, 2014 at 11:56 am
@Joker_vD: What you are calling axioms are actually theorems and they can be derived from either version of semantics. An example of axiomatic semantics is the description of C++ weak atomics — one of the most unapproachable areas of language definition. As far as I know (and I talked to Hans Boehm about it), there is no operational model for weak atomics, just a set of axioms about visibility of writes.
December 11, 2014 at 3:53 pm
Yes, the axioms/properties/theorems/invariants/whatchamacallit definitely can be derived from operational or denotational semantics. But axiomatic semantics starts with them, without any “interpretation” attached, be it a state machine in case of operational semantics or a domain/category in case of denotational semantics.
If we’re talking about “portable races” aka weak atomics, while I’d agree that there probably cannot be an operational semantics equivalent to the axiomatic semantics, I’d say there are many operational semantics satisfying the axiomatic semantics: x86+RAM and ARM+RAM can be described as state machines, albeit very cumbersome ones (which is troubling because reasoning about state machines such cumbersome is not easier than formulating theorems about properties that you actually want).
So that’s the difference between the axiomatic and denotational approach, at least as I understand it: instead of looking for a bag of mathematical objects that reflects the desired properties of our programming language constructs, reason about those properties directly; don’t search for another model/interpretation of the logic theory that is the meaning of the programming language, work with the logic theory itself. The axiomatic semantics is that theory, the operational semantics is a human-friendly model of that theory, and the denotational semantics is a mathematician-friendly model of it.
December 16, 2014 at 5:07 pm
[…] the previous installment of Category Theory for Programmers we talked about the category of types and functions. If you’re new to the series, here’s the link to the initial […]
January 13, 2015 at 1:29 pm
Hi! I’ve been translating your blog posts from this series at the main Russian IT-themed website, and one of the people suggested that you should have written:
rather than
so if-like constructs would work.
Anyway, thanks for your work!
January 13, 2015 at 2:00 pm
@monnoroch: Yes, I’ve seen your translations. Thank you for popularizing my work in Russia.
Implicit conversions between data types,
booland
intin this case, are a source of some of the most insidious bugs. A well-written C++ program should work independently of how
trueand
falseare encoded. That’s why I deliberately started with
true. Of course, this was just a hypothetical definition, since
bool,
true, and
falseare reserved keywords in C++.
February 4, 2015 at 9:10 am
I’m not sure if this was an intentional simplification or not (after all, this (great!) series is about category theory, not the Curry-Howard isomorphism), but where you’ve written, “the function absurd is the statement that from falsity follows anything,” I believe it should read, “the function absurd is a proof of the statement that from false follows anything;” it’s the (polymorphic) type of absurd which corresponds to that statement.
February 4, 2015 at 12:03 pm
@sj: I was being vague because this is only true in a vague, hand-waving sense, considering the problems with the bottom in Haskell. The type of the function absurd corresponds to a preposition, the implementation would be the proof, and I didn’t provide the implementation, so I couldn’t claim the proof. I looked at Edward Kmett’s clever hack in Data.Void but I don’t think it would make it any clearer.
Okay, I changed the wording to “the type of the function absurd…”
February 4, 2015 at 11:01 pm
Your thought experiment with monkeys has a fatal flow: None of Shakespeares plays were grammatically correct. So your grammar checked monkeys have zero probability of generating one of his plays. (Maybe dependent types would help here?)
April 19, 2015 at 12:54 am
Exercise #6 raises some questions in my beginner mind. There are two functions of the type () -> Bool. Are those distinct morphisms? It seems so, because I’m asked to label the morphisms, but my intuition tells me that they’re identical?
April 19, 2015 at 12:38 pm
@Uglemat: These two functions are not identical because they produce different results for the same input.
Your intuition is probably telling you that flipping True and False (the
negatefunction) is an isomorphism, which is true. But that doesn’t mean that the two functions are the same.
April 19, 2015 at 6:11 pm
@Milewski Actually my thinking was that hom(A, B) could have maximum one element. Because wouldn’t more than one be superfluous? Because what more information is contained in a morphism than the two objects? Should the concrete “behavior” of a morphism be taken as a part of its information? I guess what I’m saying is that I don’t understand what a morphism is. When you do type-checking, you wouldn’t distinguish between two morphisms with the same start and target because both are equivalent in the world of types, where concrete implementation is “hidden”, maybe that’s what caused me to think the stuff above.
April 19, 2015 at 8:09 pm
@Uglemat: There are two points of view. When you’re looking at an abstract category, you’re not supposed to “understand” what a morphism is. You just say there are two morphisms between these two objects, and that’s that. The structure of the category lies in how many morphisms there are between any two objects and how they compose.
But here we are trying to build a category by mimicking the structure of a programming language. So we look at the language, its types and its functions, and build a category that corresponds to it. There is a type called () and a type called Bool. They will correspond to two objects in our category. Then there are two functions from () to Bool. They will give rise to two morphisms between the two objects.
Abstracting means forgetting about the implementation. In the category, we no longer remember why the two morphisms were supposed to be different — they just are.
April 19, 2015 at 9:07 pm
Ok, that makes sense. You’d have to represent a morphism with a 3-tuple like (from, to, morphism-id) though if hom-set returns an actual set (if I understand set theory correctly). Since hom-set doesn’t need to return an actual set (as morphism@wikipedia tells me) maybe that’s a different way of solving it (if “not set” can be taken to mean a list). Thanks for clearing this up!
April 19, 2015 at 9:25 pm
I try to use the word hom-set to denote a set of morphisms. What Wikipedia says is that some people stretch the notion of hom-set to mean something more than a set (I try to use hom-object in that case). But when they say that hom-set is not a set, they mean it’s a class — something that can be bigger than a set.
Yes, there are things bigger than sets. For instance, a collection of all sets is not a set. Fortunately, as programmers, we don’t have to worry about such things.
May 7, 2015 at 7:26 pm
Maybe you mentioned it somewhere in your posts and I just overlooked it, but Hask = Set + | implies that category Set consists of countable sets only. Is this simplification made only here or the category theory doesn’t work with uncountable sets either? Does it matter at all, as I get the feeling that many things are irrelevant in this field?
May 7, 2015 at 10:15 pm
Set is a category of all sets, countable and uncountable.
May 10, 2015 at 11:03 pm
My solution to #1:
Any idea how to get rid of explicit Arg type parameter?
Also, Solution to 6:
Void ———–> ()
Void ———–> Bool
Bool —————> ()
() ——————-> Bool
() —————-> Bool
Is this right? Should there be two arrows from unit to bool?
May 11, 2015 at 10:16 am
I think there are some template tricks using traits that could eliminate the need for the explicit type parameter Arg.
Yes, there should be two arrows from unit () to bool (but only one from Void). And don’t forget the identity arrows.
May 31, 2015 at 6:25 pm
Regarding challenge #6:
Should there be two morphisms Bool->Void and ()->Void? We can define such functions, but can’t call them — same as “absurd”, right?
And should there be a “not” morphism Bool->Bool? If yes, than it will look like “identity” but won’t satisfy laws of “identity”. And if no, than why? There is a function “not” and all functions should be in category in form of morphism, right?
June 1, 2015 at 4:35 am
May I know what this sentence means? Any example perhaps?
“The only serious argument I hear against strong static type checking is that it might eliminate some programs that are semantically correct.”
I’ve been trying to understand monad and I heard that it’s heavily related to category theory. Really appreciate for the effort you’re putting in explaining it very extensively here.
June 5, 2015 at 6:42 pm
@Iwan: Essentially anywhere you see an explicit cast, the programmer is overriding the type system. The programmer was able to reason that despite the types not matching formally, the code will work correctly. The programmer had more information than the type checker. Even in Haskell you may occasionally see
unsafeCoerceas a means to bypass the type system, for instance to get better performance. (See this Stack Overflow discussion.)
June 5, 2015 at 9:43 pm
@ rpominov: How would you define a function
Bool->Void? What would it return when called with
True?
notis a legitimate morphism that is not identity. So there are indeed two morphisms
Bool->Bool. (BTW,
notis missing in Ezo’s solution.)
June 5, 2015 at 10:02 pm
I think I understand now. I was confused with what “define” means. I thought it meant to “define” type signature of a function. I just did’t realize that for
Void->Boolwe can define not only signature, but a function body as well, and still won’t be able to call it. While for
Bool->Voidwe can’t define a function body, so there can’t be such morphism.
And for
notI just did’t realize that in a category can be a morphisms from
Ato
A, that isn’t the identity morphisms.
Thank you!
June 17, 2015 at 4:24 pm
Solution for the Ex6 seems to be like:
Am I right?
But the question arises: what is an identity function for the Void type? In math it is just an empty function from ∅ to ∅. But we can’t declare it in Haskell. So it is a bit weird 🙂
June 17, 2015 at 7:05 pm
@karkunow: You can declare and implement it in Haskell
You’ll never be able to call it. But that’s a different story.
June 17, 2015 at 9:34 pm
@bartosz, thanks, got it!
July 20, 2015 at 10:55 pm
Indeed, Void -> Void is just a particular case of parametric f x = x, likewise 0^0 is a particular case of general formula a^b with exception that you cannot compute 0^0. That is, you can define 0^0, as a particular case of a^b but cannot evaluate it. I started to think about it because I have computed the amount of distinct functions that we must have
It was more difficult to define Void to anything other than Void or Unit. I could not map Void to Boolean. My consideration suggests that there should be only one such function. But which one?
July 21, 2015 at 11:16 am
This table also illustrates chapter 5. We clearly see that ⊥ suits the terminal object definition since there is always 1 function of type a → ⊥ and 0 functions of type ⊥ → a except ⊥ → ⊥, which has undefined number of functions. We also see that the unit () has always 1 map to it from any type, making it ideal terminal object. Yet, it also maps to every value in your type system, as you say in this chapter, which makes it not that terminal.
July 21, 2015 at 12:08 pm
@Valentin: By convention, 0^0 is assumed to be 1, so you do get correct numbers in all cases.
I wouldn’t use the symbol ⊥ for the initial object, because it has a meaning in Haskell as a non-terminating computation. The presence of non-termination complicates things a lot, and I want to avoid it.
The fact that () maps to any other object (except Void) doesn’t interfere with it being terminal.
As for the function from Void to Bool. Formally, in Haskell, you could define two such functions:
but you can easily convince yourself that it’s the same function.
I didn’t get into the definition of what it means for functions (in the sense of mappings between sets) to be equal. So here it is: Two functions are equal if, for all arguments, they return the same values. It’s called “extensional” equality. For all x, f x = g x. In the case of Void, the set of arguments is empty, so vtob and vtob’ are equal “in vacuum.”
Or, if you like proof by contradiction, try to show that vtob is different from vtob’. You would have to find an argument for which they produce different values. Good luck finding such argument!
July 21, 2015 at 2:02 pm
“Vacuously equal” is brilliant. Indeed, it seems to be a generalization of vacuous truth, ∀x∈A:Q(x) where Q is not limited to bi-value predicate. I am sure that everybody will agree that this is utterly breathtaking. But I am still would like to know why 0^0=1 is “a correct number”. We should have all 1’s in the first row of the table and all zeroes in the first column. There is a certain conflict at their intersection, in the first corner cell, if it must be set to 0 or 1. It is surprising that category theory argues for correct number 0^0 = 1. It paradoxically says that can produce Void given a Void, despite we cannot produce anything else, given a Void with the argument “nobody can give us a void”.
December 28, 2015 at 5:47 pm
I kind of feel like thinking of types as sets only is somehow incomplete. Isn’t it also necessary to equip your sets with composition laws to completely describe them? For example, in the boolean type example, it is clear that it is a different type from say, the equivalence classes of integers modulo 2. Since both sets are of cardinality 2, what differenciates them is their composition laws.
December 29, 2015 at 5:23 pm
In the previous section I explained that composition is the essence of every category. In the category of sets, this would be the composition of functions between these sets.
Having said that, sets of the same cardinality are isomoprhic, which means they can be substituted for each other. If you have an algoritm implemented in terms of Booleans, you can write an equivalent algorithm in terms of integers modulo 2. The only difference between isomorphic types is that some of them might lead to more efficient implementations, which is something outside of type theory.
December 30, 2015 at 6:24 am
Thanks for your reply,
Ok, I understand now. While reading your articles, I keep forgetting we are talking about sets, not groups or other kind of structures equiped with composition laws. I made the same error in the next section: I didn’t understand why it was saying that “adders” where morphisms because clearly they where not mapping identity at the left to identity at the right. But I realise now that there is no identity element in sets and morphisms between sets are functions so it make sense after all.
It is unnatural for me to think in these terms because I am not used to it. I keep viewing this through the prism of my prior group algebra exposure.
January 3, 2016 at 11:39 am
Thanks for blog posts. Its been very enjoyable so far. I’ve seen many memoize functions for single parameter functions on integers. Here is my attempt at memoizing variadic functions in ECMAScript® 2015.
const memoize = (f, ...leftArgs) => {
const undef = {}; // f() might be undefined, so ref type used for check later
let unit = undef;
const memo = new Map();
return (...args) => {
if (args.length === 0) {
if (unit === undef) {
unit = f(...leftArgs);
}
return unit;
}
const [arg, ...rightArgs] = args;
if (! memo.has(arg)) {
memo.set(arg, memoize(f, ...leftArgs, arg));
}
return memo.get(arg)(...rightArgs);
};
};
January 5, 2016 at 11:02 am
i feel like only () -> () is possible to implement, everything else is either impossible or absurd?
January 5, 2016 at 1:28 pm
What about two possible functions ()->Bool, for instance?
April 23, 2016 at 4:06 am
I would like to mention that Enzo’s solution is not complete. Some morphisms of type Bool -> Bool are missing.
April 23, 2016 at 11:33 am
Who is Enzo? And what solution are you talking about?
June 21, 2016 at 11:06 am
Regarding comment #51:
It’s obvious that ∀v∈Void => vtob v = True ≠ False = vtob’ v. So vtob = vtob’ can only be satisfied if there are no v’s (otherwise, we claim vtob v = True = False = vtob’ v, which is fallacious). Since v∈Void and Void is empty, the condition that there are no v’s is satisfied. Therefore, it is indeed true that vtob = vtob’.
Is my understanding of this correct?
June 22, 2016 at 1:00 am
This article in wikipedia may help.
Also, if you’re not afraid of proofs by contradiction, think about how you would negate a statement with a universal quantifier:
You’d have to find a counterexample, that is,
If X is an empty set, nothing exists in it. So the negation of the original statement is false. (Of course, proof by contradiction is shunned in constructivist logic, but that’s a different story.)
July 4, 2016 at 6:41 am
const 1 (undefined :: Void)
July 4, 2016 at 7:02 am
Hmm. Infinitely many functions of type
Integer -> ()can be built using undefined. Consider
July 16, 2016 at 6:58 am
@bartosz, You say that “… in several studies Haskell didn’t come as strongly ahead of the pack in code quality as one would expect.”
Which studies are you referring to? If it’s not too much trouble, could you provide the references?
(Background: I regularly face resistance from imperative programmers to embrace FP techniques. For example, somehow the ‘M’ word often causes strong negative reactions and that seems to be the end of it. I’m searching for solid evidence to support the claim that pure FP languages such as Haskell, accompanied by its underpinning, category theory, are not just academic toys.)
July 16, 2016 at 9:12 am
Here’s some literature:
A Large Scale Study of Programming Languages
and Code Quality in Github,
A Comparative Study of Programming Languages in Rosetta Code.
They contain references to other studies.
A good resource is Why Haskell Matters.
October 17, 2016 at 11:21 am
With regards to
Bool -> Voidand
() -> Void, wouldn’t following be a proper morphism?
bottom = bottom
btov :: Bool -> Void
btov _ = bottom
As Hask includes bottom, is it correct to say that this function is a morphism?
October 17, 2016 at 12:27 pm
It’s a tricky question. That’s why I keep hedging my statements about Haskell by saying “ignoring bottoms.” Some people, like Andrei Bauer or Robert Harper, even doubt whether Hask is a real category.
October 21, 2016 at 10:31 am
In comment 40 you said:
“Yes, there should be two arrows from unit () to bool (but only one from Void)”
There are two functions from Void to Bool, right?
1.Void -> True
2.Void -> False
October 21, 2016 at 11:17 am
Void is a type, True and False are values. What you wrote is neither a type signature nor a function definition. But I understand what you mean. You mean this:
But despite appearances, these two formulas give you the same function. For any value of the argument
x, they produce the same result. Remember,
xmust be an element of the empty set!
November 6, 2016 at 1:46 am
An implementation of memoize in F#:
For the naive fib function you’ll get:
First run took: 00:00:02.4870968
Second run took: 00:00:00.0000013
For the optimized memfib the result is:
First run took: 00:00:00.0006868
Second run took: 00:00:00.0000010
December 10, 2016 at 1:22 pm
Hi Bartosz, thanks for the great series of articles. I’ve just started and I am amazed by how simple things appear after your explanation.
I am just curious about point 5 from the challenges.
What I came up with is 4 distinct functions of Bool -> Bool signature.
Of course I can have a function like this:
But that seems the same as id function. Or I can go with another one like
But that seems the same as false.
So based on the above my intuition tells my that there are 4 distinct Bool -> Bool functions. Am I right ?
December 10, 2016 at 1:33 pm
@Łukasz: Later you’ll see that these functions can be represented as
BoolBool, or 22, which indeed gives 4.
June 27, 2017 at 1:18 am
Hi, great to read about a seemingly esoteric subject in a context I’m very familiar with – programming ! One point in this text… you mention “A mathematical function is just a mapping of values to values.” Might be worth mentioning that mathematical functions are single-valued mappings and not multi-valued mappings, i.e. a single input cannot go to two or more different outputs.
August 12, 2017 at 8:11 am | https://bartoszmilewski.com/2014/11/24/types-and-functions/ | CC-MAIN-2017-34 | refinedweb | 6,216 | 61.87 |
See also: IRC log
Agenda
Day 1, Day 2, Day 3
IFRAME Accessibility Inquiry:
RM: review of yesterday; new review of CURIE received today
<Steven>
RM: model response on that submitted on behalf of XForms?
<Steven>
RM: personal comment from leigh: "We will clear up the wording to help reduce any potential confusion. We will also clarify that host languages are only required to use XMLNS for prefix definition if the language supports XML Namespaces. Thanks!"
SM: saw new comments last night; no DTD because the DTD is in M12n -
RM: we make it clear that there is a separate
pointer to one or the other
... put pointer to say definitive definition is pointed to and provide pointer
... defined in one place - need to reference elsewhere
SM: ok
... comment continues - confused as to why normative - perhaps whole section should be informative
RM: normative schema can be found here and the normative DTD can be found here, but section not normative itself
SP: normative bit is syntax - DTDs and schemas just informative
RM: mixture in section
SP: either make DTD and schemas normative both or informative both
RM: normative reference in M12n
SM: and point to it from informative section
... in the m12n implementation, but is not in modularization itself
... didn't went m12n have dependency on CURIEs
SP: think good not to link to m12n - people
should be able to use CURIEs regardless of implementation method
... DTD and schema informative is ok
SM: don't mind relaxNG thing
RM: more general point on what to do with RelaxNG for future - syntax for constraint, not type definitions
SP: Relax uses schema datatypes to find datatypes - used for program structure
RM: avoid RelaxNG now
SP: XHTML2 spec has RelxNG - future will include, but too late to add now
RM: informative definition of RelaxNG might enhance readability - very editorial, not real request for RelaxNG
SM: intend to do work on RelaxNG in future, but
want to address in cohesive fashion in very near future
... should i redirect comment into tracking system so is logged as LC comment
RM & SP: yes
RM: draft available; email about new tool from olivier
<Steven>
SM: how to approach
RM: work our way through document
<Roland>
SM: took old one, put in pub system; made least
number of changes possible; added appendix and that's where things stand
... diff marked version from previous
SM: will help other people
... should approach as new document today
RM: start at introduction and work our way forwards
SP: see part of our implementation strategy for
XHTML2 going via script route; scripts that implement XHTML2 part and runs
down tree making necessary changes so works within existing HTML browsers
... in that case, many UAs will have to receive as text/html just to serve, so...
... when we say "use of text/html should be limited to HTML-compatible..." -- wonder if that is too strong
... media type is being used to deliver stuff to UA just to get it in there, then - due to scripting - deliver XForms - UA thinks is HTML, and then script does what is necessary to compile into HTML
... want to deliver documents to UAs as text/html, but want to be very careful about definition of HTML-compatible
RM: distinction not between documents, but capacities of browser;
SM: browsers that explicitly accept that mime-type
RM: focus on document negotiating with browser
and serving most appropropriate - if wants text/html, give it
... this is XML and that is what we are
SM: disconnect by the way Roland & Steven
RM: UA only meant to parse well formed XML, should deliver xml mime-type - you take XML, we have XML, here it is
SM: if FF claims to accept XML and XHTML, why serve text/html
SP: no if UA accepts application/xml give it
that
... hiccup is use of text/html should be limited to HTML-compatible family documents
SM: right -- it does say that
<ShaneM> the use of 'text/html' SHOULD be limited to HTML-compatible XHTML Family documents intended for delivery to user agents that do not explcitly accept 'application/xhtml+xml'.
<Steven> "the use of 'text/html' SHOULD be limited to HTML-compatible XHTML Family documents"
SM: a SHOULD not a MUST
... thought intent was not to irritate constituencies using XHTML1 - transitional thing; has to be HTML-compatible, or target UA may not accept it
SP: depends on our definition of HTML-compatible
SM: try to explain in Appendix C of XHTML 1.0 - Appendix A of this document
RM: if UA asks for page and prefers XML, serve
as XML; if UA doesn't support XML only HTML, then serve text/html
... document agnostic - can do either thing and respond based on what UA wants
... not document constraint per se, but browser constraint, which we handle
SP: explicitly mention cases where people doing stuff - implementing XML based languages via scripting; in that case, acceptable to deliver as text/html just to get to UA
RM: not sure right justification - doc should state what should be done, not justify
SP: don't want to get into current situation
where people claim not XML because being delivered via text/html
... in past didn't care about media types
RM: this is where should be strong - not about
media types, but whether passes series of constraints
... mandating particular doctypes wrong approach
SP: doctype only current way to declare restraints
RM: can make assertion against a document
through validation -
... can write a doc where all markup valid against mobile profile, xhtml10 and xhtml11 - why have to pick one
SM: possible to craft doc that can validate against any of our markup family, but this WG has said "have to have doc type"
SP: if want to declare doc as mobile OK,
document has to have basic DTD in front - if someone else declares as foo,
need another DTD even if document satisfies both standards, can't validate as
both
... rule about doctype to use constrains authors from authoring once and declaring valid for a number of profiles
RM: correct
SM: not clear how relevant to document or what we can do
RM: perfectly acceptable to deliver as
XHTML1.0, XHTML1.1, Mobile Profile, HTML5 -- pipe stream can then use
text/html or application/xml
... assertion part of document not metadata
... is byte stream acceptable as text/html in HTML4x browser; same byte stream delivered to valid mobile device, then deliver as application/xml; not implicit to byte stream
SM: media type tells the consumer how to evaluate document - what internal engine to use
RM: that's not intrinsic to document, but how
bind 2 together
... can take same byte stream into FF and whether served as text/html or application/xml works
SM: side-effects: changes the DOM
... is there anything in doc that is in conflict with your points
RM: turn around question - how respond to request from UA, not something intrinsic in document - document can legitimately be multiple form (valid in more than one langauge)
SM: hope that that behavior is encouraged by this doc
RM: document-centric approach (what to push to
browser) rather than responding to UA requests - push-pull or pull-push
... what UA asks for or is capable of understanding determines how we act
SM: first paragraph of abstract says that
RM: if browser asks for application/xml send as
that - serve what UA prefers; negotiation in pike
... XML higher fidelity, but if only understands one or other, then that is the constraint, not the document
... response from negotiation with UA; this is what i can accept, give me the highest fidelity
TH: without a DOCTYPE many tools beome impossible to write, such as accessibility checkers
<Tina> Without a DOCTYPE many tools becomes impossible to write such that they can deliver trustworthy results. Accessibility checkers is one such example.
<ShaneM> +1 to Tina's comment
Yam: as mobile UA manufacturer, don't want to be bound to any mime-type - process what we can; interested in using mime-type to advertise browser capability; media type specification or note?
<Tina> Wouldn't it be far more useful to continue the work on CC/PP instead of using the mime-type, since the mime-type, looked at pragmatically, doesn't really say anything about capability?
Yam: if note, emphasize 1.0 or 1.1 - from mobile UA viewpoint, this module will clarify how to handle XHTML Basic as well as other XHTML flavors; 2 editorial points: status of document (have to make sure consistent); second in 3.5 say HTML, should be HTML4 other places HTML-compatible; need to define HTML compatible or explicitly state HTML4-compatible
tina, yes to CC/PP
<Roland> My comment was not that DOCTYPE should not be used but that a single document can conform to more than one DOCTYPE.
Yam: profile
SM: need strategy for that - came up on RDFa discussion this week
Yam: mimetype profile should require specification of DTD -- can clarify have to use profile + foo; my assumption is have to use profile parameter and in doing so have to specify DTD
SM: haven't developed concrete strategy there; markB has other ideas; had other suggestions; reasonable to use mimetype but need to do in rec track document or m12n, otherwise, not normative
Yam: happy with informative
SM: issue with HTML-compatible and HTML4 - HTML4-compatible would explicitly exclude HTML5 for better or worse
GJR +1 to HTML4-compatible
SP: too early to say HTML5
Yam: don't know anything about HTML5 compatibility
SM: absolutely right
... HTML4-compatible ok?
GJR: yes
Yam: yes
RESOLUTION: in mimetype document use HTML4-compatible and HTML4-foo wherever appears in document to remove confusion
RM: what should abstract say that currently
doesn't?
... how to make as easy as possible for authors to develop content so can be delivered in multiple mimetypes
SM: something about title?
RM: title itself doesn't get to heart of what trying to do - guide for authors on how to develop content so can be served as multiple media types
SM: understand, but title already well-know
RM: title - XML Media Type sub-title: Serving XML in an HTML World
SP: Serving XHTML in Legacy UAs?
RM: Serving XHTML to Multiple User Agents
<ShaneM> Delivering XHTML to XHTML and HTML User Agents
Serving the Most Appropriate Content to Multiple User Agents from a Single Document Source
RM: who is expected to read?
SP: olivier
<Steven> That was intended as a joke, for the record
SM: consumers of document: all people who hang
out on freenode #web who say don't use XHTML because doesn't work
... if can get them to understand ok to serve XHTML to current UAs, then that is a huge win
Yam: reason document more implemented on mobile browser is no way to specify XHTML Basic or other/multiple host language support; W3C note will gratify my constituency
<Tina> I find that hard to agree to. Most authors appear not to know how to use XHTML. It wouldn't do the "XHTML Case" any good to have an even larger amount of invalid documents out there that people believe are "just fine" 'cause they render as HTML.
RM: that's what we were trying to discuss
earlier - what UA is capable or ready to accept - i accept A, B, C, D, and E
so give me the best one you have
... capability of browser and then if document fits multiple profiles; basic 1 and basic 1.1 - UA conforms to basic 1.0, takes that
SM: logical conclusion means need to specify
somewhere a syntax for the accept headers profile parameter -- markB has
proposal; UA has to say in precise and concise way all of the things it
accepts
... tokens specified for implements in XML Events 2 - could be that sort of mechanism
Yam: no other document specifies that
SM: agree - might push into update of RFC if part of media spec
RM: should consult with UbiWeb and CC/PP
... break off as topic that needs attention - problem about UA advertising capabilities and preferences and serving the appropriate content
SM: markB should be in on discussion
... how to make abstract get to point RM wants reword "documents intended for delivery to user agents that do not explcitly accept 'application/xhtml+xml'. 'application/xml' and 'text/xml' MAY also be used, but whenever appropriate, 'application/xhtml+xml' or 'text/html' SHOULD be used rather than those generic XML media types."
RM: question of persepective - how to respond to UA's capabilities and preferences
<ShaneM> XHTML Family documents intended for delivery to user agents that do not explcitly state in their HTTP-Accept header that they
<ShaneM> accept 'application/xhtml+xml'
SM: that what you mean, Roland?
RM: yes
Tina: problem with it is that everyone knows
that an accept head is often misleading - tend to ignore accept headers and
HTTP requests; not a road we should formally go down - should not ignore
accept
... understand pragmatic reasons, but uneasy with exception for HTML-family document; should talk with HTTP people
SP: don't understand what you think we are ignoring
Tina: UAs use accept header that says "i'll accpet everything no matter what" - then how to decide what to give it?
SP: accept header should give list of what can actually accept, but with a terminal star to cache ("Save As.." dialog is an example - not refused, but check accept headers to check if can natively deal with it
SM: according to HTTP spec, permisible to accept *.* -- we're telling people to ignore that
Tina: formal point of view would mean we are telling people to ignore part of HTTP spec
SP: not saying that
SM: think we are, actually
... term "explicitly state" - unless UA explicitly says it accepts application/xhtml+xml don't give it xhtml - that's inconsistent with spirit of HTTP spec
SP: by saying *.* how do you get xhtml documents in to browsers and parse them correctly; all UAs accept *.*, which means "don't exclude anything"
RM: these are things UA might say - if this is X do Y, if this is Q do W
Tina: need to check on *.* support in UAs
... usual way of writing accept header parsers haven't come across many that accept anything
... need to investigate further - can we delay discussion so can dig into it a bit?
<Steven> Here Tina:
<Steven> Opera sends: Accept: text/html, application/xml;q=0.9, application/xhtml+xml, image/png, image/jpeg, image/gif, image/x-xbitmap, */*;q=0.1
<Steven> Safari sends: Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
<Steven> Mozilla: Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
<Steven> Amaya: Accept: */*;q=0.1,image/svg+xml,application/mathml+xml,application/xhtml+xml
<Steven> Lynx sends: Accept: text/html, text/plain, application/x-bittorrent, application/x-troff-man, message/partial, message/external-body, application/x-tar, application/x-gtar, application/msword, text/richtext, text/enriched, application/ms-tnef, text/*, application/x-debian-package, audio/basic, */*;q=0.01
<Tina> My local Lynx sends text/html, text/plain, text/css, text/sgml, */*;q=0.01
i often change my lynx settings in response to browser sniffing so i can get into certain sites
RM: piece that is missing; talk about things in abstract not covered in detail - detail goes into media type uses, but don't say what requests might come form UA; accept headers not mentioned in body, just in abstract
<ShaneM> in our list of explicit rules.... how about if we say "if an Accept header only contains */*, documents SHOULD be sent using media type text/html if they are HTML4 compatible, or as application/xhtml+xml if they are not" or something.
RM: in media type usage, should say "which is the most appropriate"
TH: worth noting that ones tested so far send a
Qvalue with *.*
... who set up yoyo.org?
yoyo: "Welcome to Yoyo Internet Services. We pride ourselves on consistency of service and quality of workmanship. Founded in 1996 by Matt Saunders and Neil Levine, Yoyo has gone from strength to strength despite its overwhelming vacuousity."
"Our mission is to consistently conjugate through dynamism, surrealism and semanticism in order to further our goals of hysterical servlet hypotenae. This autonomy cultivates our duplicitous mercenary valetism in the eclectic dot org arena."
RM: accept header fallback for browser detect
Tina: not useable
GJR: easily forged
Tina: need to point out that should do that
<ShaneM> Lets add a section for dealing with content negotiation via accept headers explicitly
RM: process accept headers to determine which
of possible types to send - not addressed in detail
... give accept header and respond
Yam: OMA specifies that UA should advertise their supported mimetypes - send QValues because of *.* - at end smallest QValue
RM: please send us a pointer
SM: i introduced that before OMA was OMA
SP: fifteen minute break?
=== 15 MINUTE BREAK ===
IFrame Accessibility Query:
first response (S Schnabel of SAP):
<ShaneM> FYI - updated CURIEs as per mail from Leigh and our discussion today.
RM: appendix on capacity guidelines for authors to deliver documents as valid XHTML or XML
TH: reread HTTP spec - no provision in 14.1 for accept header - only send if explicitly stated, so withdraw my objection
<Tina> Section 14.1 on the HTTP specification does not explicitly prohibit sending content to an UA which explicitly mention support for a MIME type
<ShaneM>
<Steven>
TH: content negotioation is feasible again - since accept explicitly, like to add - please convert XHTML to HTML when delivering to HTML UA; problem is that those using XHTML are doing so poorly in belief that if use XHTML, UA will alert them if something wrong, and then send as text/html
RM: how should one write one's content to minimize those problems
TH: do it on server before sending down the pipe; a lot of authors mis-using XHTML - no idea of concepts behind it
RM: a lot of content generated directly from
databases as XML
... automatically emit XML, not XHTML
TH: technical limitation
RM: many database servers only support XML, not XHTML --
TH: can't send structured data to UA
RM: you can
TH: not if won't accept it
... won't be structured data you think it is; if send XHTML to HTML user agent will not be interpreted as XHTML
... won't help people structure data - the "out" is that XHTML will be ok when served as HTML and if something was wrong, something would notify me
SP: people so used to idea to check document source by loading into UA and seeing if looks "right"
TH: XHTML is an XML language - problem with not with code but delivery mechanism
SP: trying to say, if UA accepts XML media types, use that - fall back to HTML media type as a recourse of last resort
TH: if fall back to HTML, please transform it
SP: what to transform?
SM: if develop according to compatibility guidelines, no need to transform
TH: trying to up the ante so get people to send valid XHTML to HTML user agents
RM: document in general write as XHTML and if valid, XML-based browser will serve it
SM: if not going to follow guidelines, then ensure that you transform your content before delilvery to HTML browser?
TH: please transform to language browser supports - can automatically transform XML
<alessio> old test page with server content negotiation:
SP: saying that, but not quite in those words; compatability guidelines - if serve as text/html, text should be in this form
RM: 2 alternatives: write to compatability GL to ensure XHTML can be parsed by HTML UA, if not, then need to transform into HTML
TH: want it to be VERY explicit
RM: can make explicit that one can write to GL or transform XHTML to HTML
TH: matter of finding good tech solution - which exist, so not the major problem
<ShaneM> ACTION: Shane craft text to about transformation of XHTML to HTML. [recorded in]
SP: why an Appendix A and then Appendix 2?
SM: odd...
... first one Processing Instructions should be a 1
... attempted to take old guidelines, port them here, and clarify style - want to recast as clear instructions as to what should and should not do
... original text still in draft for WG review
... problem with way written previously, not clear what one supposed to do -- explained compatiblity risks and ways to work around them
... don't use processing instructions PERIOD etc.
... questions about approach or my take on problem?
RM: need good example illustrating all
principles - second, when state "do not" include a "do"
... need to be crystral clear about what should do and not do
SM: not a corresponding "do" for first guideline
<Steven>
RM: general principle: not leaving to people to infer what one should do and not do
SM: the "do" should come first
RM: yes
SM: objections to GL1?
SP: no objection - use of word of "legacy" potentially distraction
"Processing Instructions and the XML Declaration" should be A.1
RM: break out a warning - stronger than "remember, however..." - pull out and make clearer and stronger
SM: next one "A.2. Empty Elements" - Roland, you requested i change this
RM: can't remember what i said
SM: combined A.2 and A.3
SP: A.2 about elements that can only be empty and A.3 about elements that normally aren't empty, but can be
RM: have to know certain elements can only be
empty
... about a dozen
SM: will paste in "live" URL
FYI: A.3. Element Minimization and Empty Element Content
Tina: no comments on A.1, and A.2 seems reasonable
SP: interesting to note that A.2 in "normal" UAs isn't an issue
Tina: older agents need space
SP: not advocating deletion, just noting a improvement
<ShaneM>
SM: A.2 is now entitled: "Elements with no content" and combined with old A.3
RM: useful to have them there
SM: will have to update when introduce new elements
TH: big question: compatability GL for HTML4
and less
... won't be added in HTML5
SM: if introduce new elements in XHTML2 have to
revisit this document
... don't want to discuss today, but need to think about how to serve to "classic" browsers
TH: probability of sending XHTML2 to legacy agents
SP: people do that nowadays
... XForms scripts convert XForm into HTML, but delivered XForms
TH: using javascript, i assume
SP: yes
TH: accessibility part of it - what to do with javascript
RM: are people happy with A.2 "Elements with no content"
SP: personally prefered old form with separation between empty elements and those which can be empty
TH: A.3 more of a problem - should keep separate;
SP: liked fact that pointed out that XML allowed <br></br> doesn't mean anything
RM: can go into rationale - doesn't change rules
Original A.3 text: ."
TH: clearer we are, the better the results when authors write it
RM: A.2 what should do is <br /> what should not do is <br></br>
SP: good example is script - if script src= have to have /script
Alessio: yes
SP: let's use scripts there - that is poster-child example of why have to do this way
RM: concrete do this and don't do this in CSS columns
<Tina> This was spotted "in the wild" last week: <div style="... "/>
SM: 2 votes for restoring A.3
RM: don't object, but understand distinction WG members making, but not sure authors care about
SP: then say "elements that can only be empty"
RM: some elements can only be empty; list them and what can do with them
SM: elements that can never have content?
SP: works for me
<alessio> +1
SM: Elements that can never have content versus Elements that may not contain content
<Tina> +1
GJR +1
RM: when do scripting, do certain things (but that topic for later)
SM: script example in restored A.3?
... trying to capture ideas in draft - will update later
... A.4 "A.4. Embedded Style Sheets and Scripts" say "do" but not "do not"
RM: needs balance
TH: why not say use external stylesheets and scripts - XHTML in HTML compatability mode, use external scripts
SM: unreasonable burden if all one is doing is adding a few localized styles
RM: override one style with another for single
document instance
... example would be helpful - if use pointy brackets have to do like this in order to work, but easier to create and maintain external stylesheets
SP: problem can arise if content gets fed through XSLT first - protecting documents; what we warn about could happen - authors should be aware
GJR notes that FireVox cannot process external stylesheets but only embedded or inline CSS3-speech values
SM: A.5 A.5. Line Breaks within Attribute Values - dont' know why anyone would care
TH: some probably process new lines
specially
... as long as is CDATA should ignore new lines
SM: so if datatypes IDREFs wouldn't be legal
... fine guideline, but don't know origin -- needs a do
RM: yes
... has this problem been mitigated over the years?
... perhaps confusion is that problem was limited and long time ago
SM: not a bad rule, but next rule is candidate
for deletion
... A.6. isindex - who uses them?
GJR: deprecated in HTML4 anyway
SM: original text wrong - no more than one
ISINDEX element is a no brainer
... would remove A.6
SP: ok
Alessio: ok
GJR: ok
SM: kept these consistent with Appendix C - even down to fragment IDs
RM: can log changed
SM: change number?
TH: use DEL to show A.6 no longer applicable
SM: renumber
SP: good
SM: A.7. The lang and xml:lang Attributes - may be controversial
TH: tool looks at doctype then tries to figure out lang attribute
<Steven> I have no problem with the lang and xml:lang
<Steven> scribe: Steven
TH: I'm worried that tools that see it's HTML: will go looking for @lang
<oedipus> dropped the phone - must have disconnected
<oedipus> ATs key off of lang - if try just xml:lang, won't switch natural langauges - can log as bug with GNOME's Orca
Yam: I'm not sure about this issue
... we are thinking about removing @lang
... but CSS selectors may use it (for instance)
... we have no strong position though
<scribe> scribe: oedipus
need to find CSS selector example that uses aria live regions to change language of text
SM: need portable way to indicated language change
Yam: existing UA implementations use @lang for CSS selectors - we discourage use of that for XHTML family of languages consistency of use
RM: people using lang specifically, can't write XHTML 1.1 or 1.2 document with @lang
SM: want to ensure rule works before ship
XHTML2
... could reintroduce lang
RM: perhaps target
GJR: AT problem is DOM calls and limitations AT-side on what it relies upon to key natural language switches
SP: if need compatability GLs to serve as HTML need lang, but in XHTML lang means nothing and is just there for convenience
SM: normatively state allow @lang but if doc served as XHTML @lang must be ignored?
SP: yes, no meaning in XHTML - only there for convenience of being able to serve XHTML documents to legacy browsers
RM: synonyms?
SP: then people might stop using xml:lang
RM: ramifications?
SM: CSS selectors based on lang when have both lang and xml:lang - XHTML 1.1 document, for example, serving document in either media type, how to craft css selectors to make everything in latin pink and italic given i'm using lang and xml:lang
SP: no, use coma as delimeter -- CSS doesn't select on attribute - in HTML uses lang, in XHTML uses xml:lang, so only one rule in CSS
TH: could use CSS rule to key on @lang specifically
SP: CSS has knowledge of language text is in
due to selector - language comes from parent element of current element; if
current element is in latin, do this - only way to do in CSS anyway
... no selector that says if parent of current element has @blah ...
TH: selecing on lang attribute correct thing to do according to CSS
SP: can have select on lang and xml:lang
TH: people today select on lang - problem is HTML compatibility GLs
SP: why i'm suggesting we add lang back into the languages
GJR plus 1 to readding @lang
TH: if people transformed to HTML would be
easier
... if transform from xml:lang to lang
SP: what is easier
TH: don't need to put lang into XHTML Base
SM: 2 sets of constituents to serve: one of them is "the great unwashed" - just have a simple site who want simple solutions; then there are sites such as amazon, which have FAR more resources can bring to bear
SP: but don't want to transform everytime serve page
SM: cache it
RM: can i? if getting weather updated every 5 seconds, may never be cached
SM: cached for 5 seconds
RM: a lot of transformation for 5 seconds
SM: if permit lang along lines SP discussed -
technically, how do we do that?
... or introduce new lang module?
SP: yeah, or may need other attributes, in which case a "compatability module" would be the answer
Yam: have legacy module, right?
SP: don't want to allow BLINK along with @lang
SM: lang not in legacy module now, so wouldn't
be conflict if introduced elsewhere
... could introduce an HTML compatibility module as update to 1.1
<yamx> i killed line by mistake
<yamx> OK, zakim, thanks.
SM: compatibility GLs wouldn't be useful for 1.1
SP: better off using 1.2 anyway
RM: definitely
SM: for this GL, "do use lang" - or "do use both" - realize can't if doing 1.1, Basic, +RDFa, etc
TH: need to put responsibility on author - use both
GJR: same thing authors do with name and id
SM: will update appropriately and then need to
figure out how to help languages support both of these, but that is
independent discusssion
... "A.8. Fragment Identifiers" - not controversial
TH: no
SP: when wrote A.8 there were UAs that didn't recognize ID, but that has changed
SM: and i changed the doc
... "A.9. Character Encoding"
... interesting problem
Yam: Japanese example would be useful
SM: true
SP: including mediatype and encoding in same metadata bad choice made way back when
RM: there is a default - if satisfied with default, don't need to do this
TH: back to HTTP spec - not possible - HTTP content type can be set as much as you want, but often receive US ASCII from server
SM: if accessing document in filesystem not possible
TH: author can't change content type served by server
<Steven> And some protocols don't support encodings, eg ftp, file:
TH: can't change content type set by server; practical problem; really ought to set on server - should stress
SM: if doc coming from server, character encoding is specified in response, so is authoritative, and may even override XML declaration
TH: yes
SM: telling people not to use XML declaratoin
TH: bigger problem if send as XHTML and don't have control over encoding and content type
SM: serious problem - compatability GLs and content negotiation only relevant when have access to server and ability to control headers otherwise nothing we say matters
TH: some think HTTP-EQUIV panacea; still sending as text/html
<alessio> really true
SP: HTML4 spec says that server should look at
HTTP-EQUIV and send appropriate, but never implemented
... GL should be "when serving a document, putting anything in the document that is unlikely to help because server always has priority"
TH: also not to expect something else
SP: META unlikely to help you at all
SM: maybe not mention
SP: should to make explicit
RM: first item similar
SM: suggestion: could we have 2 rules: when
document being sent from server, do this
... when document being accessed directly do this
<Steven> Default for XML is UTF-8, right?
TH: even when served by HTTP daemon, even if proper content type served, save as HTML
<alessio> yes, steven
TH: legacy issue; if not serving direct from server, use HTTP-EQUIV as per spec, but if set content type and char encoding on server
RM: not an isolated issue
SM: why don't we just say - ifyou want to be compatible encode as UTF-8 or UTF-16
RM: agree
SP: and state ensure that server serves it as UTF-8
<alessio> +1
plus 1
RM: happy with that solution
SM: if want docs to be portable, encode in UTF-8 or UTF-16
SP: people should use UTF-8 everywhere ideally
TH: make sure server announces correctly needs to be in GL
HTML5: "If the document contains a meta element with a charset attribute or a meta element in the Encoding declaration state, then the character encoding used must be an ASCII-compatible character encoding. "
SM: HTML5 talking about default when no server - we say use META HTTP-EQUIV
HTML5: "If the document does not start with a BOM, and if its encoding is not explicitly given by Content-Type metadata, then the character encoding used must be an ASCII-compatible character encoding, and, in addition, if that encoding isn't US-ASCII itself, then the encoding must be specified using a meta element with a charset attribute or a meta element in the Encoding declaration state. "
SP: anyone actually look at HTTP-EQUIV
SM: browsers do
TH: most commonly used browsers do
... issue is what is use they make of it - some ignore content type based on extension
Yam: use META HTTP-EQUIV to ensure japanese
encoding
... all Japanese encoding should be in meta http-equiv
SM: that overrides HTTP headers?
Yam: not sure; easier for carrier to serve
SM: A.10. Boolean Attributes
... controversy?
RM: looks good
SM: A.11. Document Object Model and XHTML
Alessio: can get to HTML DOM as well
SM: will remove "if is really true" editorial note
TH: as long as works with HTML4 UAs don;t have problem
SM: A.12. Using Ampersands
fine with GJR
SP: sentence difficult to read - AND in all
caps
... change AND to lower case
TH: possibly STRONG?
... if possible, use semi-colon instead of ampersands in URIs
SM: made change to case of "and"
GJR: plus an abbr expansion for & <abbr title="ampersand">&</abbr>
SM: when using ampersand in URI use its escaped
form
... A.13. Cascading Style Sheets (CSS) and XHTML
... may have over-simplified
RM: may want to make comment on lang here
SP: CSS selector on xml:lang rather than lang
SM: do nots needed?
RM: inverse fairly obvious
SM: added thing about style HTML element
... in HTML style on body becomes style for entire viewport; in XML does not
TH: change Do rule - if need to set, then...
SP: special rule in CSS is because early versions of IE didn't have style for HTML element, so CSS states, style BODY element
SM: do style HTML element?
SP: no, for compatability reasons, style BODY rather than HTML element
SM: style applies only to block not whole window
SP: if you want to remove styling put on HTML,
have to define style for HTML, but this might be the ocassion to say "this is
an old rule"
... when wrote, were browsers that didn't support HTML
SM: just added this
RM: implications - example of consequences - we need to make clear what consequences are
SM: good point, Roland; maybe not even necessary to say this; authors put style on BODY, not HEAD; and when served as HTML style on BODY apply to entire window
SP: what CSS spec says, but not reality; 2px
margin around HTML element
... why can't i get rid of margin around my HTML document - reason: have to explicitly state padding:0;margin:0
SM: do we need this rule?
SP: no
TH: need rule to point this out
RM: rationale needs more work - particularly important for this appendix a section
SM: will try to update so can revisit later
... had been telling people to use xml style declarations, and i think we should tell people not to use them for compatibility
... A.15. White Space Characters in HTML vs. XML
... should change name from "white space"
SP: agreee
SM: A.16. The Named Character Reference '
TH: typographcally, is right single quote - no problem with A.16, but shouldn't get into typography side of it
SM: ok
===== ADJOURN FOR LUNCH - RETURN in 77 Minutes (quarter to next hour ======
SP: complete discussion of media types?
SM: enough to create a new draft
RM: one other thing: validator thing olivier brought up
<ShaneM> Olivier says: Good. How about:
<ShaneM> - [now] updating the tool to match the draft guidelines in the ED of xhtmlmime
<ShaneM> - [soon] including the checks into the validator, mark them as [experimental], informative, whatever. That will provide us with better and more feedback than just a WD.
SM: his proposal to me this morning appears above
RM: something we'd like to see, isn't it?
... do we believe running through validator to get info if suitable to be served?
GJR thinks would promote awareness
<alessio> yes
SM: concern is "validator as holy writ" -- good or bad, depending upon whether it works; would be more comfortable if could provide WG resources to work on that
(that being validator and control over changes)
SP: depends on how they present information -- warnings versus errors
RM: that is what they did
SM: get document updated to reflect discussion today; respond to olivier that WG ok with warnings
GJR would like a STRICT mode where errors are reported as errors
SM: open source tool
RM: anyone can hack anytime want to; what is in w3c validator he takes care of
<ShaneM> ACTION: Shane to finish the updating the XHTMLMIME draft then respond to Olivier's proposal. [recorded in]
RM: anything anyone wants to mention in closing on mime doc?
RM: have 1.1 spec waiting for modularization;
proposed change adding target attribute back in, which is considered not in
scope of what should do in new edition
... what do we do next?
... drop from second edition?
... release XHTML 1.n and if so what would be in it?
SP: adding @target to 1.1 is that Basic needs -- 1.1 should be considered full Basic with all facets of Basic
TH: @target to open frame or new window?
... no reason to put into declarative markup language
SM: why is target not useful
TH: authors shouldn't force new windows
... if in XFrames, ok, but not in Basic
GJR notes that handling of @target is user agent control issue being addressed in UAAG2.0
TH: opening windows outside scope of declarative language
Yam: against using target, but made compromise with CDF or another WG who demanded it be restored; don't think we need it
SP: SVG or CDF?
... doesn't SVG need it in some way?
RM: compatability guide question -- html mime --- inhibiter for those trying to move from HTML to XML
SP: reasonalbe use cases for @target
... list of search results - click on a search result to get result without changing underlying doc
TH: UA has built in
... those that can spawn new windows have that feature
GJR author proposes, user disposes
SM: @target has different semantics in SVG?
Yam: against @target in 1.2 -- agree that natural that have in 1.1, but from practical POV it is a mess -- HTML5, XHTML2, etc.
SP: talking about 1.1 -- issue 1.1 as proper superset of basic
SM: if don't add anything to 1.1 can release as PER
with schema
SM: would not be superset of Basic
SP: why not
SM: not including @target
... those who care about input mode and @target will be affected - who are they?
Yam: don't care if 1.1 is superset or not
SM: very good point: explanation of XHTML
family would be fine to support 1.1 second edition or first edition -- basic
1.1 document
... @target is single-most requested feature in our public wish list
TH: any UA used today that allows user not to open @target-ed windows
RM: a lot of users don't know that can click on link and open new window
TH: @target specifies UA behavior in practice
SP: a "hook" for use by
<alessio> you're right, gregory
GJR: render unto User Agent what is user agent...
TH: going to be used to open new windows - removed to prevent that so shouldn't go back in
SP: didn't remove - never in STRICT and 1.1 is
a revised version of STRICT, but didn't revise version of transitional DTD
b/c nothing to revise
... one thing people have asked for is to use @target in 1.1
... not clear why we should say people shouldn't do that - perhaps should give arguments for people not opening windows
TH: why put back?
SP: popular demand
TH: what purpose does @target fill in XHTML?
<alessio> people reintroduces it with dom injection...
TH: know complaints, but purpose aren't for frames mostly but for forcing open new windows
SP: XFrames - target a document onto a frame
... XFrames does NOT need @target - that's why need in HTML - if environment that needs this, here are the hooks you use
Alessio: @target should not be in 1.1 -- regard @target as action
SP: SVG uses @target, i believe -- trying to locate
Alessio: 2 diff roles for target - 1. to open new window; 2. to point at a frame in a frameset or multimedia concept
RM: if we don't have @target, what is effect?
going to write scripts to force open scripts
... inhibitor to go to 1.1 or will just write script
TH: include despite bad practice because people going to do it anyway
GJR notes that BLOCKQUOTE deprecated for layout purposes in HTML4x but you can find it used for layout on W3C site
TH: why @target in HTML? to open new windows -
compromise: use to target fragments that already exist - not to open new
windows because that is not role of markup langauge
... say "is NOT to be used to open new windows"
<Steven> "The target attribute is designed to be a general hook for binding to an external environment"
<ShaneM> see for explanation of Target Module
<alessio> another use of "target" attribute:
@target itself could be repurposed to a new tab, a sidebar by user agent
TH: user agent problem that persists - @target
simply opens new window/browser instance
... why cave in to an illegitimate request?
SP: what is wrong with clicking on things to open windows
SM: explicit user action
GJR: that is point of UAAG1 and UAAG2
<alessio> target in SMIL: ."
TH: open in same window or another window
SP: programming problem with browser
TH: support a11y by suppressing @target
... take stand that every problem due to poor user agents
... opens unpleasant can of worms
SP: agree with removing features that have no
raison d'etre
... open windows all day long by clicking on things
GJR: @target should be treated as an option, not an absolute
TH: if going to say has good uses, have to also note problems
SP: both cases UA problem
TH: in one case SHOULD in other SHOULD NOT
<yamx> I don't think this argument is productive... If we don't like target (I am not a fan of target), we should discuss in XHTML Basic 1.1., not in XHTML 1.n 2nd edition...
@target should be treated as an option by UAs until explicit user action determines what to do
<yamx> Whatever it is. XHTML 1.n 2nd ed should be a super set of XHTML Basic 1.1., which is the starting point of this discussion.
RM: applications in windows environment still open windows that are accessible
TH: don't agree
... far larger probability if opens in new window won't know
... authors shouldn't make assumptions
GJR: author proposes, user disposes
SP: opposite is never open another link in another window - non sequitor
<alessio> maybe the UA could help, alerting when a new window is prospected
TH: problem include link and target to open in new window, have no idea what happens when link gets to user - author wants to open new window, user will be surprised by uncertainty and unexpected behavior
SP: filling in long form, don't understand something, click on help link, tells me what to do, but hasn't destroyed context of form and other helps open in same popup window
TH: if 800% magnification, where does window open?
<yamx> target has an interoperability problem in mobile domain, certainly, but we have to accept @target for compromising SVG group...
there is a queue
AT should alert the user that new window being opened or new pane / tab being opened
TH: shou ld be user's choice, not authors
... screen magnifiers - simply blow up what is on screen - too dumb an app
GJR: if no @target will end up with raw javascripted links which are a WCAG violation
RM: not language purity - from author and/or
user -- what do constituents want: authors creating material, and users
interacting with that
... if in there could treat @target as an option - if have javascript won't have single standard hook
TH: to this point no UA has implemented that
... user agents include options to open new windows and tabs from context menues; not bothered to use @target to give users an option
RM: will just use javascript to do anyway
The more things are forbidden, the more popular they become. -- Mark Twain
TH: why not restore MARQUEE
<Steven> We have had no requests to put marquee back in
TH: same rationale
<Steven> there is a queue
GJR: put @target in with strict limitations -- that is an option that should be a programmatic flag
<ShaneM> +1
<alessio> +1
<Steven> +1
RM: if target has characteristics, what hooks can we provide what options are available
SP: hear TH's problems with @target, also hear
a lot of complaints that @target not in 1.1 so use 1.0
... thing i like about target is gives us control - can put conditions on its use
... can say, if use it user agent should do this and that -- XHTML Basic accepts but ignores it which is perfectly acceptable behavior
... serious and valuable use cases for @target - if in markup, is under control - if don't have it, people will use javascript to do it with all the rammifications of that
SM: UAAG exist - to extent they exist, don't
know if UA devs pay any attention to or authors pay attention to or anyone
pays attention to - no control over those guidelines, but do have control
over our own spec; proposal in IRC to put limitations on target - need to
define; value in doing that independent of decision vis a vis 1.1.;
regardless of what we do with @target, poeplewil want to create new
windows
... need to give authors a consistent way to do it, and provide documentation for UA devs
... people always going to be generating new windows - should put conditions on it
TH: keeping it out is a signal as much as putting it back in - shouldn't be allowing authors to engage in improper behavior under cover of standards
SP: for people to use "as they see fit"
TH: try other way around - put @target back in but say DO NOT use to open new windows
SP: can point to UAAG and WCAG
GJR: win win - WCAG also against raw javascripted links and stripping chrome
RM: EU reference WCAG directly
... procurment in most european countries and will become EU wide
Yam: if prohibit use of @target to open new window, then ok to include
Alessio: some government sites forced to use XHTML 1.0 Strict so cannot open new windows declaratively
AC: people will use javascript to work around that though
<alessio> yes, the stanca act
RM: conclusions?
... looked at target but where to be reintroduced and how?
AC: @target for support of SVG elements - think
need to point out how NOT to use @target
... need to know interoperability with UAs; what do UAs need to do to warn user?
also a requirements document at
<alessio> yes, thanks gregory
SM: Yam, you felt 1.1 could be superset of Basic 1.1
Yam: starting point of discussion, i think
... do we need second edition?
SM: need to republish to add schema implementation - no extension,
Yam: ambivalent
<yamx> Oh, I kill the line by mistake, too.
SP: don't care very much - 1.2 more interesting
bit
... if issue as PER, people would rationalize that @target and input mode should be in 1.0 as well
... only counter argument is that XHTML2 coming to fix these things
<yamx> I am back.
SP: similar with Print - family of MLs trhat arent' constrained to each other either way
RM: second edition just add schema - or add schema and a couple of attributes?
SM: couldn't do in second edition
RM: 1.1 second edition that adds schema is only thing to do
SM: agree -- if want to reissue 1.1
... low-impact, so can do it logistically
SP: unchanged 1.1 a better approach; 1.2 where expend energy on combining existing specifications
SM: Yam not to interested in 1.2 - should go directly to XHTML2 - need to have discussion on that
RM: 1.1 take to second edition that simply adds schema and errata
<yamx> fine
SM: same thing with Print at same time
<yamx> no objection.
<Steven> +1
RM: objections?
<alessio> +1
GJR no objection
<Steven> my +1 was to the 1.1 suggestion
RESOLUTION: take XHTML 1.1 to Second Edition by simply adding Schema and Errata
<yamx> agree.
RM: can we/should we do a 1.2 and if so why and what would be in it?
SP: created something people using not backed up by spec XHTML1.1+RDFa
SM: references DTD
SP: oh - then it's not as bad as i thought
... option 1 is take all specs being produced seperately as part of m12n
SM: ARIA
RM: yes
<ShaneM> XHTML+RDFa is defined at
SP: wrap all those up into a language called
XHTML 1.2 so people can refer to markup language that uses these things
... another reason, makes step to XHTML2 that much smaller
... community needs to be led step-by-step to XHTML2 rather than just being presented with it - get used to concepts
RM: XML Events and ????
SP: step to XHTML2 is XForms, HREF everywhere
and SRC everywhere
... on the other hand, people out there already using XHTML11+ without doctype - not backed up by single spec, but rather widely used
... another option - do it all at one go
<ShaneM> I think stepping directly to XForms for xhtml 1.2 would be too far.
RM: how to introduce Access, ARIA, Role as first class citizen and validatable -- small step but huge gain - point release rationale is to add a11y features -- good advertising
plus 1
SM: anything put into XHTML 1.2 should work in browsers today
RM: agree with that
<alessio> idem
SP: wou ld mean not including Access
RM: right
SM: yep
SP: so 2 options there: 1. only bit remaining to be implemented
<ShaneM> XHTML2 also has meta and link everywhere
SP: could make effor to do implementation of Access in javascript
SM: started a few weeks ago
GJR: PF needs to submit support for Access to
HTML5
... was in initial request to HTML5
<alessio> I'd done last year a test for Access
RM: XML Events - adding @implements on SCRIPT
SP: no problem because works already
SM: yes
GJR: huge plus 1
SM: not all XML Events
RM: no, just to enable @implements feature
... proposal for release and its content
SM: yes, and a timetable - dependencies on things not yet completed
RM: agree in principle to create proposal for XHTML 1.2 including @implements
Yam: don't object, but W3C may - agree under condition to make transition market for XHTML2 short, not long
<Steven> oedipus, alessio, please add agreemetns like that to the record!
RM: most definitely
GJR: @implements is going to be VERY useful
<Steven> @implements++
RESOLUTION: Proposal for XHTML 1.2 - Content and Timescale as outlined here
<scribe> ACTION: Steven - draft proposal for XHTML 1.2 - Content and Timescale [recorded in]
<yamx> It is 23:00 in Japan.
RM: good discussion- made progress
<yamx> OK.
RM: XML Events 2 and Features after break?
<yamx> see you later.
===== 15 MINUTE BREAK ======
RM: XML Events 2 -
RM: number of updates since last face2face -
would like to get to LC - what needs to be done?
... did see some comments in XForms group, but don't know what happened to them - their status
SP: researches the matter
<Steven>
RM: felt XML Events doc should be more self
contained
... people shouldn't have to go to DOM3 spec, for instance charlie commented
SP: long discussion but no action item; most
... will ping him to send comments to us
RM: editorial things not too much of a
problem
... start with abstract
RM: differences from DOM3 and @target
RM: conformance - not much change at all
... addition was to allow chameleon version should ML allow
SM: what does this mean given our new
understanding of "null namespace"?
... bring in Events Module?
SP: not sure have new understanding of "null
namespace"
... terminology used in certain circles not backed by any spec
SM: lets call it "no namespace"
... are we suggesting ok to bring XML Events into a language and use XML Event attributes in "no namespace"
RM: unless someone uses chameleon, including events
SP: not syntaxically the same, but semantically the same
SM: don't access from DOM in same way
... in a Compound Document, HTML uses Events in chameleon form - bring into HTML elements with no qualifiers, but SVG does not - in a Compound Document, do we expect the action attribute or event attribute will have same semantic on HTML p element as ev:event="circle"
<Steven> We will write <a href="..."><action event="DOMActivate"...>
<Steven> instead of
<Steven> this <a href="..."><action ev:event="DOMActivate"...>
<Steven> but the meaning will be the same
<Steven> We should coordinate with Forms WG on this
RM: been discussed at forms WG meetings i
believe
... namespaces discussed in Forms f2f last week?
SP: consults minutes from Forms f2f
... not in detail
RM: specifics of what is in XML Events
Module
... listener element
RM: diff with DOM3 is QNames?
SM: essential difference
RM: observer element
... handler element
RM: default is target
... event propogates or continues - default should be performed or not
... not too diff from XML Events 1 - same principle.
attributes for observer
RM: can add attribute to handler itself -
... not much different from XML Events 1 - comments?
<alessio> no
RM: XML Handlers
<scribe> ACTION: element to [recorded in]
RM: similar to XForms, can use as container for
potential actions
... condition - only true if XPath expression true
... can finally have xml:id
<Steven> action 4=
RM: script element -
... refined SCRIPT - important diff is @implements
... will discuss @implements in detail later
the dispatch element:
addEventListener:
RM: very similar - can register
eventListener
... can stop bubbling
... can prevent default defined for event
... straightforward
RM: XPath Expressions:
RM: XPath to describe context information (XPath context)
RM: @implements
... optional - this script should only be loaded if UA doesn't have implementation of feature
... key thing is how to describe features
... safe URI or safe CURIE ok, but how to define features - names event and where dispatched to
RM: events predefined by DOM3, can create own
events and dispatch those
... XPath Expressions ahs extra note
... not setting particular context mode
... what necessary to define context - what would someone find useful - don't currently have idea of context
... 6.1.1.XPath event Function
... "Function event returns the value of a property of the current event object, as determined by the string argument. "
... identify feature for @implements - URI but represents what?
SP: anticipate fight over XPath
... last version didn't have XPath, now it is required
SM: some way to do that doesn't require
XPath?
... conditionals without way of referencing?
RM: could do in script
... definition of what conditionals are
SP: conditionals need to be in some langauge
... maybe call section 6 "Expressions"
... expressions that happen to be the ones in XPath
... not asking to implement XPath, but syntax derived from XPath - serious difference
RM: what is the core we need? what subset of
XPath
... not a big dependency on XPath
SM: 2 modules - XML Events and XML Handlers - do we envision world where one can have handlers without events
SP: people write scripts today without XML Events
SM: XML Handler Module needs all of what is defined in XML Events
RM: except for SCRIPT element
SM: true
... might be useful to have SCRIPT and @implements independent of XML Events - applies to Handlers as well
<Steven> +1
<alessio> +1
SM: wonder if shouldn't have a module in specificiation - XML Events, Handler Element, Script ELement
plus 1
RM: agree
... a convenience that in one document, but they are separate --
SM: imagin e there is a Script Module without dependency on other 2 modules
RM: does not appear so
SM: new Handler module without new Events module doesn't make sense
RM: some actions could be useful without events
SM: if anything has dependency on events, then depenency on events module
RM: yes
... only exception is script - no dependence on other 2
SM: then separate it out
... make sense to have XML Events Module without XML Handlers Module?
RM: XML Events 1 are used today and there are no handlers, so must have some value without handlers
SP: didn't define handlers because wanted people to use handlers already had on XML Events
SM: require people to use XML Events Module AND XML Handlers Modlue?
SP: no
SM: good
RM: proposal: split into 3 modules - XML Events, XML Handlers, and Script plus change in wording about use of XPath
SM: minor editorial stuff too
RESOLUTION: will break into 3 Modules: XML Events Module, XML Handlers Module, and Script Module
SM: accept Yam's proposal
Yam: change attribution/acknowledgement
RM: needs to describe who we are today and who is doing the work today
RM: namespaces - should be dealing with
someting more fine grained in namespace
... there is another namespace option
<Steven> scribe: Steven
RM: So a namespace is rather too coarse grain to define the features that will be implemented
SM: The spec says CURIEs are used for
identification
... the CURIE spec allows for reserved values
... but doesn't allow for multiple default prefixes
... so if we are to define a separate vocab document, it *can't* be another default vocab
implements="m12n:hrefeverywhere"
SM: So you may as well just use the URI
<oedipus> thought was supposed to be able to use URI
RM: You're only going to write this once, so it isn't a major problem having to write it
<ShaneM>
perfick
SM: That was what I had in mind
RM: Me too
implements=""
RM: So if I implemented XML Events 2, what would it say?
<ShaneM>
<oedipus> implements="m12n:events m12n:handlers" ?
SM: Right, so we need to define the term for each module
RM: Can we agregate features?
Steven: I hope so; eg XForms
... or even XHTML2
<oedipus> me too
<oedipus> RM: core - first features XML Events
<oedipus> RM: XML Events not in xmlns
<scribe> scribe: oedipus
RM: URI probablly different
SM: keep conflating namespaces and vocabulary spaces
<ShaneM>
RM: would break linkage to NS
... using namespace name suggest something that isn't true - or a linkage that isn't there
SM: in feature space can put anywhere we want,
but makes sense to coollect in single place
... is XForms in this document or will they incorporate?
RM: can go anywhere URI can point to
<ShaneM> ACTION: Shane create an initial features document that includes the features from XML Events 2. [recorded in]
GJR: point about conflating namespaces and vocab spaces very pertinent (for building expert handlers)
SM: should point to XML Events - so good BP in document
RM: in script element, could show how to point
to other parts of document -- could in fact, implement itself
... could be bootstrapped in
SM: could.... but not sure for first version
RM: showing how implments handler events
... any other thoughts on this topic?
SP: action shane has is list names of features and module feature represents, right?
RM: assign names to features and make clear that named features are modules in question
SM: have a vision of it - linked together and
back to base spec
... want meaningful triples - should have best practices
RM: not just in spec, but in position to develop solution that does it
SM: definitely
RM: other comments?
<yamx> no from me.
RM: conclude this topic - anything else to go
back over from earlier today?
... have some catch-up time tomorrow morning
Yam: yesterday mark mentioned HTML5 group have security issues - relevant for any ML - if devise good mechansim for wwindow shouold be seperate spec
<Roland>
RM: action number 2 - immediately after mark's comments
RM: idea was MarkB go back on items and our reply should be consistent with / coordinate with XForms response on this
SP: moved comments up into section where topic discussed
RM: Yam correct, do want to ensure coordinated response
Yam: don't agree with justifications
========= ADJOURN ============ | http://www.w3.org/2008/06/18-xhtml-minutes.html | CC-MAIN-2016-26 | refinedweb | 10,294 | 55.58 |
Ogg::LibOgg - XS Code for Ogg bindings for Perl.
use Ogg::LibOgg; my $filename = "t/test.ogg"; open $fd, $filename or die "Can't open $filename: $!"; ## Make Ogg Packet my $op = Ogg::LibOgg::make_ogg_packet(); ## Make Ogg Stream State my $os = Ogg::LibOgg::make_ogg_stream_state(); ## Make Ogg Page my $og = Ogg::LibOgg::make_ogg_page(); ## Make Ogg Sync State my $oy = Ogg::LibOgg::make_ogg_sync_state(); ## Ogg Sync Init Ogg::LibOgg::ogg_sync_init($oy); # this should be == 0 ## Ogg Read Page (this is a custom wrapper, please read the perldoc) Ogg::LibOgg::ogg_read_page($fd, $oy, $og); # == 0, ## Ogg Page Serial Number my $slno = Ogg::LibOgg::ogg_page_serialno($og); ..etc.. close $fd;
Ogg::LibOgg let you call the libogg functions directly and the glue is written in XS. Please read LibOgg.xs to understand the implementation.
None by default. Please use Ogg::LibOgg ':all' to export everything to the current namespace.
Memory Allocation for the Ogg Structures
Creates an Ogg Packet.
-Input: Void
-Output: Memory address of Ogg Packet.
Creates an Ogg Stream State.
-Input: Void
-Output: Memory address of Ogg Stream State.
Creates an Ogg Page.
-Input: Void
-Output: Memory address of Ogg Page.
Creates an Ogg Sync State.
-Input: Void
-Output: Memory address og Ogg Sync State.
This function is used to initialize an ogg_stream_state struct and allocates appropriate memory in preparation for encoding or decoding.
-Input: ogg_stream_state (memory addr) serial number
-Output: 0 if successful -1 if unsuccessful
This function is a wrapper around ogg_sync_pageout. In an actual decoding loop, this function should be called first to ensure that the buffer is cleared. The example code below illustrates a clean reading loop which will fill and output pages.
ogg_sync_pageout takes the data stored in the buffer of the ogg_sync_state struct and inserts them into an ogg_page.
if (ogg_sync_pageout(&oy, &og) != 1) { buffer = ogg_sync_buffer(&oy, 8192); bytes = fread(buffer, 1, 8192, stdin); ogg_sync_wrote(&oy, bytes); }
-Input: FILE * ogg_sync_state ogg_page
-Output: -1 buffer overflow or internal error (status of ogg_sync_wrote) 0 all other cases
Indicates whether this page is at the beginning of the logical bitstream.
-Input: ogg_page
-Output: > 0 if this page is the beginning of a bitstream. 0 if this page is from any other location in the stream.
Indicates whether this page is at the end of the logical bitstream.
-Input: ogg_page
-Output: > 0 if this page is the beginning of a bitstream. 0 if this page is from any other location in the stream.
Checksums an ogg_page.
(Not *SURE* why in the ogg official doc, they have given the function definition as 'int ogg_page_checksum_set(og)', it should be actuall 'void ogg_page_checksum_set(og)').
-Input: ogg_page
-Output: void
Indicates whether this page contains packet data which has been continued from the previous page.
-Input: ogg_page
-Output: int
Returns the exact granular position of the packet data contained at the end of this page.
-Input: ogg_page
-Output: n is the specific last granular position of the decoded data contained in the page.
Returns the number of packets that are completed on this page.
-Input: ogg_page
-Output: 1 If a page consists of a packet begun on a previous page, != 0 a new packet begun (but not completed) on this page,
0 If a page happens to be a single packet that was begun on a previous page, != 0 and spans to the next page
Returns the sequential page number.
-Input: ogg_page
-Output: n, is the page number for this page.
Returns the unique serial number for the logical bitstream of this page. Each page contains the serial number for the logical bitstream that it belongs to.
-Input: ogg_page
-Output: n, where n is the serial number for this page.
This function clears and frees the internal memory used by the ogg_stream_state struct, but does not free the structure itself.
-Input: ogg_stream_state
-Output: 0 is always returned
This function sets values in the ogg_stream_state struct back to initial values.
-Input: ogg_stream_state
-Output: 0, success != 0, internal error
Similar to ogg_stream_reset, but it also it sets the stream serial number to the given value.
-Input: ogg_stream_state serialno
-Output: 0, success != 0, internal error
This function frees the internal memory used by the ogg_stream_state struct as well as the structure itself.
-Input: ogg_stream_state
-Output: 0, always
This function is used to check the error or readiness condition of an ogg_stream_state structure.
-Input: ogg_stream_state
-Output: 0, if the ogg_stream_state structure is initialized and ready. != 0, never initialized, or if an unrecoverable internal error occurred
This function returns the version of ogg_page used in this page.
-Input: ogg_page
-Output: n, is the version number (for current ogg, 0 is always returned, else error)
his function clears the memory used by the ogg_packet struct, but does not free the structure itself. Don't call it directly.
-Input: ogg_packet
@Ouput: void
This function submits a packet to the bitstream for page encapsulation. After this is called, more packets can be submitted, or pages can be written out.
-Input: ogg_stream_state ogg_packet
-Output: 0, on success -1, on internal error
This function forms packets into pages, this would be called after using ogg_stream_packetin().
-Input: ogg_stream_state ogg_page
-Output: 0, insufficient data or internal error != 0, page has been completed and returned.
This function checks for remaining packets inside the stream and forces remaining packets into a page, regardless of the size of the page.
-Input: ogg_stream_state ogg_page
-Output: 0, means that all packet data has already been flushed into pages != 0, means that remaining packets have successfully been flushed into the page.
ogg sync init, This function is used to initialize an ogg_sync_state struct to a known initial value in preparation for manipulation of an Ogg bitstream.
-Input: ogg_sync_state (memory addr)
-Output: 0 (always)
This function is used to free the internal storage of an ogg_sync_state struct and resets the struct to the initial state.
-Input: ogg_sync_state
-Output: 0, always
This function is used to reset the internal counters of the ogg_sync_state struct to initial values.
-Input: ogg_sync_state
-Output: 0, always
This function is used to destroy an ogg_sync_state struct and free all memory used.
-Input: ogg_sync_state
@Ouput: 0, always
This function is used to check the error or readiness condition of an ogg_sync_state structure.
-Input: ogg_sync_state
-Output: 0, is returned if the ogg_sync_state structure is initialized and ready. != 0, if the structure was never initialized, or if an unrecoverable internal error
This function is used to provide a properly-sized buffer for writing.
-Input: ogg_sync_state size
-Output: Returns a pointer to the newly allocated buffer or NULL on error
This function is used to tell the ogg_sync_state struct how many bytes we wrote into the buffer.
-Input: ogg_sync_state bytes
-Output: -1 if the number of bytes written overflows the internal storage of the ogg_sync_state struct or an internal error occurred. 0 in all other cases.
This function synchronizes the ogg_sync_state struct to the next ogg_page.
-Input: ogg_sync_state ogg_page
-Output: -n means that we skipped n bytes within the bitstream. 0 means that we need more data, or than an internal error occurred. n means that the page was synced at the current location, with a page length of n bytes.
This function takes the data stored in the buffer of the ogg_sync_state struct and inserts them into an ogg_page. In an actual decoding loop, this function should be called first to ensure that the buffer is cleared.
-Input: ogg_sync_state ogg_page
-Output: -1 returned if stream has not yet captured sync (bytes were skipped). 0 returned if more data needed or an internal error occurred. 1 indicated a page was synced and returned.
This function adds a complete page to the bitstream. In a typical decoding situation, this function would be called after using ogg_sync_pageout to create a valid ogg_page struct.
-Input: ogg_stream_state ogg_page
-Output: -1 indicates failure. 0 means that the page was successfully submitted to the bitstream.
This function assembles a data packet for output to the codec decoding engine. The data has already been submitted to the ogg_stream_state and broken into segments. Each successive call returns the next complete packet built from those segments.
-Input: ogg_stream_state ogg_packet
-Output: -1 if we are out of sync and there is a gap in the data. 0 insufficient data available to complete a packet, or unrecoverable internal error occurred. 1 if a packet was assembled normally. op contains the next packet from the stream.
This function attempts to assemble a raw data packet and returns it without advancing decoding.
-Input: ogg_stream_state ogg_packet
-Output: -1, no packet available due to lost sync or a hole in the data. 0, insufficient data available to complete a packet, or on unrecoverable internal error 1, packet is available
ogg_page and ogg_packet structs mostly point to storage in libvorbis/libtheora. They're never freed or manipulated directly. You may get a malloc error doing so.
oggpack_buffer struct which is used with libogg's bitpacking functions is not exposed, as you should never need to directly access anything in this structure. So are the functions manipulating oggpack_buffer, they too are not exposed.
ogg_stream_iovecin,
not implemented as this function submits packet data (in the form of an array of ogg_iovec_t, rather than using an ogg_packet structure) to the bitstream for page encapsulation.
Vigith Maurice <vigith@yahoo-inc.com>
Vigith Maurice (C) 2011
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.8.9 or, at your option, any later version of Perl 5 you may have available. | http://search.cpan.org/~vigith/Ogg-LibOgg-0.02/lib/Ogg/LibOgg.pm | CC-MAIN-2014-52 | refinedweb | 1,568 | 56.25 |
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