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• Setting UIImage dimensions on UITableViewCell image

  - by bbrown

  I've got a standard UITableViewCell where I'm using the text and image properties to display a favicon.ico and a label. For the most part, this works really well since UIImage supports the ICO format. However, some sites (like Amazon.com say) have favicon.icos that make use of the ICO format's ability to store multiple sizes in the same file. Amazon stores four different sizes, all the way up to 48x48. This results in most images being 16x16 except for a few that come in at 32x32 or 48x48 and make everything look terrible. I have searched here, the official forum, the documentation, and elsewhere without success. I have tried everything that I could think of to constrain the image size. The only thing that worked was an undocumented method, which I'm not about to use. This is my first app and my first experience with Cocoa (came from C#). In case I wasn't clear in what I'm looking for, ideally the advice would center around setting the dimensions of the UIImage so that the 48x48 version would scale down to 16x16 or a method to tell UIImage to use the 16x16 version present in the ICO file. I don't necessarily need code: just a suggestion of an approach would do me fine. Does anyone have any suggestions? (I asked in the official forum as well because I've sunk more than a day into this already. If a solution is posted there, I'll put it here as well.)

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• How would you answer Joel's sample programming questions?

  - by Khorkrak

  I recently interviewed a candidate for a new position here. I wish though that I'd read Joel's Guerrilla Guide to Interviewing prior to that interview - naturally I happened upon it the night afterwards :P http://www.joelonsoftware.com/articles/GuerrillaInterviewing3.html So I tried answering the easy questions myself - yeah I used the python interpreter to type stuff in and tested the results a bit - I didn't look up any solutions beforehand though and I also thought about how long it took me to come up with answers for each one and what I'd look for the next time I interview someone. I'd let them type stuff into the interpreter and see how did used python's introspection capabilities too to find out things like what's the re module's method for building a regex etc. Here are my answers - these are in python of course - what are yours in your favourite language? Do you see any issues with the answers I came up with - i.e. how could they be improved upon - what did I miss? Joel's example questions: Write a function that determines if a string starts with an upper-case letter A-Z. import re upper_regex = re.compile("^[A-Z]") def starts_with_upper(text): return upper_regex.match(text) is not None Write a function that determines the area of a circle given the radius. from math import pi def area(radius): return pi * radius**2 Add up all the values in an array. sum([1, 2, 3, 4, 5]) Harder Question: Write an example of a recursive function - so how about the classic factorial one: def factorial(num): if num > 1: return num * factorial(num - 1) else: return 1

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• Creating customized .dmg files upon download

  - by Marten

  I want to distribute a cross-platform application for which the executable file is slightly different, depending on the user who downloaded it. This is done by having a placeholder string somewhere in the executable that is replaced with something user-specific upon download. The webserver that has to do these string replacements is a Linux machine. For Windows, the executable is not compressed in the installer .exe, so the string replacement is easy. For uncompressed Mac OS X .dmg files, this is also easy. However, .dmg files that are compressed with either gzip or bzip2 are not so easy. For example, in the latter case, the compressed .dmg is not one big bzip2-compressed disk image, but instead consists of a few different bzip2-compressed parts (with different block sizes) and a plist suffix. Also, decompressing and recompressing the different parts with bzip2 does not result in the original data, so I'm guessing Apple uses some different parameters to bzip2 than the command-line tool. Is there a way to generate a compressed .dmg from an uncompressed one on Linux (which does not have hdiutil)? Or maybe another suggestion for creating customized applications without pregenerating them? It should work without any input by the user.

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• 'memcache-client' problem - app can't load the gem

  - by Max Williams

  Hi all - i'm trying to get memcached and the Interlock plugin working with a new rails app. The weird thing is that they both work fine in another app on the same machine and i can't figure out the difference that's stopping this app. The new app is rails 2.3.4 and the old one is 2.2.2 in case that's a factor. When the app starts, i get a warning from interlock: `install_memcached':Interlock::ConfigurationError: 'memcache-client' client requested but not installed. Try 'sudo gem install memcache-client'. Now, i have memcache-client installed: $> gem list | grep memcache memcache-client (1.7.8) The gem is in /var/lib/gems/1.8, which is in my GEM_PATH variable. On a bit of further investigation, the above error is raised by interlock when it refers to the MemCache class, which doesn't exist and so raises an 'anonymous module' error. So, ultimately, the problem is that MemCache isn't loaded. I have a memcached.yml in my config folder (below) however. I'm stuck - any advice anyone? #contents of config/memcached.yml defaults: namespace: millionaire #sessions: true sessions: false client: memcache-client with_finders: true development: servers: - 127.0.0.1:11211 production: servers: - 127.0.0.1:11211

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• MonoRail: Testing, Route Extensions, Folder Structures

  - by Kezzer

  I've got a few questions related to the use of MonoRail Testing Does everyone tend to use NUnit for their testing? I haven't worked enough with testing to know if this is a good testing framework to use. I'm just looking to get more into testing my applications a lot more than before and wanted to know if there's any general guidelines. Are you supposed to copy the controller over to a test area and just rename it with test in the name and re-run it? How do you ensure your test project and main project coincide with one another? Is it just a case of copying everything over again or are there tools available to do it for you? Route Extensions MonoRail tends to use <action>.rails, can you omit the .rails part if you configure your routing correctly? Why does this seem to be the standard? Folder Structures I haven't found anywhere which really points out your standard folder structure. Sure, you have Controllers, Models, and Views. But your Models folder should contain your data access objects as well. I've seen some have something like -> Models -> DaoClasses -> Entities But what about custom structures used to get data out of views? And if you're using NHibernate, where's a good place to stick the mappings? I know it's entirely dependent on the developer, but I haven't really seen any standard approach. Cheers

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• I just don't get AudioFileReadPackets

  - by Eric Christensen

  I've tried to write the smallest chunk of code to narrow down a problem. It's now just a few lines and it doesn't work, which makes it pretty clear that I have a fundamental misunderstanding of how to use AudioFileReadPackets. I've read the docs and other examples online, and apparently I'm just not getting. Could you explain it to me? Here's what this block should do: I've previously opened a file. I want to read just one packet - the first one of the file - and then print it. But it crashes on the AudioFileReadPackets line: AudioFileID mAudioFile2; AudioFileOpenURL (audioFileURL, 0x01, 0, &mAudioFile2); UInt32 *audioData2 = (UInt32 *)malloc(sizeof(UInt32) * 1); AudioFileReadPackets(mAudioFile2, false, NULL, NULL, 0, (UInt32*)1, audioData2); NSLog(@"first packet:%i",audioData2[0]); (For clarity, I've stripped out all error handling.) It's the AFRP line that crashes out. (I understand that the third and fourth argument are useful, and in my "real" code, I use them, but they're not required, right? So NULL in this case should work, right?) So then what's going on? Any guidance would be much appreciated. Thanks.

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• Java & Maven generating -and using- my own archetype

  - by Random

  Hello again! I have been busy in my project creating a webapp (in struts) that manages maven, using maven-2.2.1-uber.jar link text. The problem comes when the boss says it has to use some archetypes the company has created (so no predefined archetypes for you naughty boy!). So ok, I use the -DarchetypeRepository option (with ServletWrapper I get my complete web direction, becouse the repository will be inside the app), and the log seems to find it, but then the build fails -miserably- with this little text 'Build Failure - The defined artifact is not an archetype' as simple as that. Of course I have a lot of INFO lines that say abslutily nothig related. I have read the maven definitive guide searching for some kind of help, but it has been disapointing at best. My thoughts are thatmaybe I am missing in somewhere of all the folders tree some xml that actually sais maven that my pom.xml is an archetype not a project. But I really, really, can't find anything on the net or in the manuals that explains easy-handed how the archetype:generate (with special parameters) works and where I have to put every folder and/or file. So just to say my thoughts aloud (and hopefully you understand what I am trying to ask): I have a template where I do some xml changes (variables, etc...), then I have to call maen and do an archetype:generate with a variable project. The problem seems to be that my actual confuguration doesn't like what I am doing. After the generation of the archetype, witch luckly will create some directory trees and leave me a POM.xml somewhere I still have to do some variable changes and more xml manage stuff, so it whould be very kind from maven to don't destroy anything in this process. Any ideas why this maven-thing is not happly-ever-after asuming that my archetype is defintly an archetype? Allthought I think the code is ok, it could be wrong, as I am using maven-ubber and I call the actual CSMavenCli.main(String[, ClassWorld), I don't think it is the case this time. Thanks and all! :) Random.

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• Designing a fluid Javascript interface to hide callback asynchrony

  - by Anurag

  How would I design an API to hide the asynchronous nature of AJAX and HTTP requests, or basically delay it to provide a fluid interface. To show an example from Twitter's new Anywhere API: // get @ded's first 20 statuses, filter only the tweets that // mention photography, and render each into an HTML element T.User.find('ded').timeline().first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); function filterer(status) { return status.text.match(/photography/); } vs this (asynchronous nature of each call is clearly visible) T.User.find('ded', function(user) { user.timeline(function(statuses) { statuses.first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); }); }); It finds the user, gets their tweet timeline, filters only the first 20 tweets, applies a custom filter, and ultimately uses the callback function to process each tweet. I am guessing that a well designed API like this should work like a query builder (think ORMs) where each function call builds the query (HTTP URL in this case), until it hits a looping function such as each/map/etc., the HTTP call is made and the passed in function becomes the callback. An easy development route would be to make each AJAX call synchronous, but that's probably not the best solution. I am interested in figuring out a way to make it asynchronous, and still hide the asynchronous nature of AJAX.

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• Can I embed a custom font in an iPhone application?

  - by Airsource Ltd

  I would like to have an app include a custom font for rendering text, load it, and then use it with standard UIKit elements like UILabel. Is this possible? I found these links: http://discussions.apple.com/thread.jspa?messageID=8304744 http://forums.macrumors.com/showthread.php?t=569311 but these would require me to render each glyph myself, which is a bit too much like hard work, especially for multi-line text. I've also found posts that say straight out that it's not possible, but without justification, so I'm looking for a definitive answer. EDIT - failed -[UIFont fontWithName:size:] experiment I downloaded Harrowprint.tff (downloaded from here) and added it to my Resources directory and to the project. I then tried this code: UIFont* font = [UIFont fontWithName:@"Harrowprint" size:20]; which resulted in an exception being thrown. Looking at the TTF file in Finder confirmed that the font name was Harrowprint. EDIT - there have been a number of replies so far which tell me to read the documentation on X or Y. I've experimented extensively with all of these, and got nowhere. In one case, X turned out to be relevant only on OS X, not on iPhone. Consequently I am setting a bounty for this question, and I will award the bounty to the first person who provides an answer (using only documented APIs) who responds with sufficient information to get this working on the device. Working on the simulator too would be a bonus. EDIT - it appears that the bounty auto-awards to the answer with the highest nunber of votes. Interesting. No one actually provided an answer that solved the question as asked - the solution that involves coding your own UILabel subclass doesn't support word-wrap, which is an essential feature for me - though I guess I could extend it to do so.

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• Any way to identify a redirect when using jQuery's $.ajax() or $.getScript() methods?

  - by Bungle

  Within my company's online application, we've set up a JSONP-based API that returns some data that is used by a bookmarklet I'm developing. Here is a quick test page I set up that hits the API URL using jQuery's $.ajax() method: http://troy.onespot.com/static/3915/index.html If you look at the requests using Firebug's "Net" tab (or the like), you'll see that what's happening is that the URL is requested successfully, but since our app redirects any unauthorized users to a login page, the login page is also requested by the browser and seemingly interpreted as JavaScript. This inevitably causes an exception since the login page is HTML, not JavaScript. Basically, I'm looking for any sort of hook to determine when the request results in a redirect - some way to determine if the URL resolved to a JSONP response (which will execute a method I've predefined in the bookmarklet script) or if it resulted in a redirect. I tried wrapping the $.ajax() method in a try {} catch(e) {} block, but that doesn't trap the exception, I'm assuming because the requests were successful, just not the parsing of the login page as JavaScript. Is there anywhere I could use a try {} catch(e) {} block, or any property of $.ajax() that might allow me to hone in on the exception or otherwise determine that I've been redirected? I actually doubt this is possible, since $.getScript() (or the equivalent setup of $.ajax()) just loads a script dynamically, and can't inspect the response headers since it's cross-domain and not truly AJAX: http://api.jquery.com/jQuery.getScript/ My alternative would be to just fire off the $.ajax() for a period of time until I either get the JSONP callback or don't, and in the latter case, assume the user is not logged in and prompt them to do so. I don't like that method, though, since it would result in a lot of unnecessary requests to the app server, and would also pile up the JavaScript exceptions in the meantime. Thanks for any suggestions!

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• How can I get the correct DisplayMetrics from an AppWidget in Android?

  - by Gary

  I need to determine the screen density at runtime in an Android AppWidget. I've set up an HDPI emulator device (avd). If set up a regular executable project, and insert this code into the onCreate method: DisplayMetrics dm = getResources().getDisplayMetrics(); Log.d("MyTag", "screen density " + dm.densityDpi); This outputs "screen density 240" as expected. However, if I set up an AppWidget project, and insert this code into the onUpdate method: DisplayMetrics dm = context.getResources().getDisplayMetrics(); Log.d("MyTag", "screen density " + dm.densityDpi); This outputs "screen density 160". I noticed, hooking up the debugger, that the mDefaultDisplay member of the Resources object here is null in the AppWidget case. Similarly, if I get a resource at runtime using the Resources object obtained from context.getResources() in the AppWidget, it returns the wrong resource based on screen density. For instance, I have a 60x60px drawable for mdpi, and an 80x80 drawable for hdpi. If I get this Drawable object using context.getResources().getDrawable(...), it returns the 60x60 version. Is there any way to correctly deal with resources at runtime from the context of an AppWidget? Thanks!

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• Perl OO frameworks and program design - Moose and Conway's inside-out objects (Class::Std)

  - by Emmel

  This is more of a use-case type of question... but also generic enough to be more broadly applicable: In short, I'm working on a module that's more or less a command-line wrapper; OO naturally. Without going into too many details (unless someone wants them), there isn't a crazy amount of complexity to the system, but it did feel natural to have three or four objects in this framework. Finally, it's an open source thing I'll put out there, rather than a module with a few developers in the same firm working on it. First I implemented the OO using Class::Std, because Perl Best Practices (Conway, 2005) made a good argument for why to use inside-out objects. Full control over what attributes get accessed and so on, proper encapsulation, etc. Also his design is surprisingly simple and clever. I liked it, but then noticed that no one really uses this; in fact it seems Conway himself doesn't really recommend this anymore? So I moved to everyone's favorite, Moose. It's easy to use, although way way overkill feature-wise for what I want to do. The big, major downside is: it's got a slew of module dependencies that force users of my module to download them all. A minor downside is it's got way more functionality than I really need. What are recommendations? Inconvenience fellow developers by forcing them to use a possibly-obsolete module, or force every user of the module to download Moose and all its dependencies? Is there a third option for a proper Perl OO framework that's popular but neither of these two?

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• How can I effectively test against the Windows API?

  - by Billy ONeal

  I'm still having issues justifying TDD to myself. As I have mentioned in other questions, 90% of the code I write does absolutely nothing but Call some Windows API functions and Print out the data returned from said functions. The time spent coming up with the fake data that the code needs to process under TDD is incredible -- I literally spend 5 times as much time coming up with the example data as I would spend just writing application code. Part of this problem is that often I'm programming against APIs with which I have little experience, which forces me to write small applications that show me how the real API behaves so that I can write effective fakes/mocks on top of that API. Writing implementation first is the opposite of TDD, but in this case it is unavoidable: I do not know how the real API behaves, so how on earth am I going to be able to create a fake implementation of the API without playing with it? I have read several books on the subject, including Kent Beck's Test Driven Development, By Example, and Michael Feathers' Working Effectively with Legacy Code, which seem to be gospel for TDD fanatics. Feathers' book comes close in the way it describes breaking out dependencies, but even then, the examples provided have one thing in common: The program under test obtains input from other parts of the program under test. My programs do not follow that pattern. Instead, the only input to the program itself is the system upon which it runs. How can one effectively employ TDD on such a project?

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• vimscript: calling dictionary functions with call()

  - by intuited

  I'm hoping to call a "static" dictionary function using call(). By "static" I mean that the keyword 'dict' is not used in the function's definition. I use this nomenclature in the hopes that the effect of this keyword is to declare a static member function as is possible in java/C++/etc, ie to put the function name in the class namespace but allow it to be called without referencing an object. However this doesn't seem to work. For example: " Setup: let testdict = { } funct! testdict.funct() echo "called" endfunct " Tests: " Following each line is an indented comment " containing its output in message land, ie what was echoed. call testdict.funct() " called echo testdict.funct " 667 echo string(testdict.funct) " function('667') echo function('667') " E475: Invalid argument: 667 echo function('testdict.funct') " testdict.funct call call(testdict.funct, [ ]) " E725: Calling dict function without Dictionary: 667 " Same deal if there's an intermediate variable involved. let TestdictDotFunct = testdict.funct echo TestdictDotFunct " 667 echo string(TestdictDotFunct) " function('667') call TestdictDotFunct() " E725: Calling dict function without Dictionary: 667 From the help topic E725: It is also possible to add a function without the "dict" attribute as a Funcref to a Dictionary, but the "self" variable is not available then. So logic would seem to indicate that if "self" is not available, then it should be possible to call the function referenced by the Funcref without a Dictionary. However this doesn't seem to be the case. Am I missing something? Vim version info: $ aptitude show vim-gnome Package: vim-gnome State: installed Automatically installed: no Version: 2:7.2.245-2ubuntu2

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• Positioning SVG Elements

  - by Rob Wilkerson

  In the course of toying with SVG for the first time (using the Raphael library), I've run into a problem positioning dynamic elements on the canvas in such a way that they're completely contained within the canvas. What I'm trying to do is randomly position n words/short phrases. Since the text is variable, its position needs to be variable as well so what I'm doing is: Initially creating the text at point 0,0 with no opacity. Checking the width of the drawn text element using text.getBBox().width. Setting a new x coordinate as Math.random() * (canvas_width - ( text_width/2 ) - pad). Altering the x coordinate of the text to the newly set value (text.attr( 'x', x ) ). Setting the opacity attribute of the text to 1. I'll be the first to admit that my math acumen is limited, but this seems pretty straightforward. Somehow, I still end up with text running off beyond the right edge of my canvas. For simplicity above, I removed the bit that also sets a minimum x value by adding it to the Math.random() result. It is there, though, and I see the same problem on the leading edge of the canvas. My understanding (such as it is), is that the Math.random() bits would generate a number between 0 and 1 which could then be multiplied by some number (in my case, the canvas width - half of the text width - some arbitrary padding) to get the outer bound. I'm dividing the width of the text in half because its position on the grid is set at its center. I hope I've just been staring at this for too long, but is my math that rusty or am I misunderstanding something about the behavior of Math.random(), SVG, text or anything else that's under the hood of this solution?

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• Delphi 2010 - Source files randomly become read-only in editor?

  - by Justin

  Does anyone else have this problem or is my Delphi cursed somehow? I'll have a bunch of forms and files open in tabs in the editor and I'll be typing away and then suddenly everything stops - my .pas file has, seemingly at random, become read-only. Sometimes I can just right-click the tab at the top and uncheck "Read-Only" and continue, but sometimes this option is checked and greyed-out (disabled), meaning I can't uncheck it and I can't make any further edits to the file. This too seems to be random. In the latter case, the only solution is to save the file in question, which works, despite Delphi's assertion that the file is read-only, close its tab in the editor, and re-open it. Not catastrophic, really, but it's starting to become annoying. Could it be that I am hitting a keyboard command combination accidentally to do this or is this a bug in Delphi? I'm in Delphi 2010, Windows 7. Doubt it's anything to do with installed packages, but if anyone wants the list I'll generate it and attach it here.

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• SEO Friendly URL Rewriter Parameters

  - by Kristen

  I would appreciate you advice on how to incorporate parameters into SEO Friendly URLs We have decided to have the "techie" parameters first, followed by the "SEO Slug" \product\ABC123\fly-your-own-helicopter much like S.O. - if the SEO Slug changes, or is truncated, or missing, we still have the Product and ABC123 parameters; various articles say that having such extra data doesn't harm SEO ranking. We need to have additional parameters; we could use "-" to separate parameters as it makes them look similar to the SEO Slug, or we could/should use something else? \product\ABC123-BOYTOY-2\boys\toys\fly-your-own-helicopter This is product=ABC123, in Category=BOYTOY and Page=2. We also want to keep the hierarchy as flat as possible, and thus I think: \product-ABC123-BOYTOY-2\boys\toys\fly-your-own-helicopter would be better - one level less. We have a number of "zones", e.g. \product-ABC123\seo-slug-for-product \category-BOYTOY\seo-slug-for-category \article-54321\terms-and-conditions it would help us a lot if we could just user our 5 digit Page ID number instead, so these would become \12345-ABC123\seo-slug-for-product \23456-BOYTOY\seo-slug-for-category \54321\terms-and-conditions (Products & Categories have a number of different Page IDs for different templates, this style would take us straight to the right one) I would appreciate your insight into what parameter separators to use, and if the leading techi-data is going work well for us. In case relevant: Classic ASP application on IIS7 + MSSQL2008 Product & Category codes contain A-Z, 0-9, "_" only.

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• Some general C questions.

  - by b-gen-jack-o-neill

  Hello. I am trying to fully understand the process pro writing code in some language to execution by OS. In my case, the language would be C and the OS would be Windows. So far, I read many different articles, but I am not sure, whether I understand the process right, and I would like to ask you if you know some good articles on some subjects I couldn´t find. So, what I think I know about C (and basically other languages): C compiler itself handles only data types, basic math operations, pointers operations, and work with functions. By work with functions I mean how to pass argument to it, and how to get output from function. During compilation, function call is replaced by passing arguments to stack, and than if function is not inline, its call is replaced by some symbol for linker. Linker than find the function definition, and replace the symbol to jump adress to that function (and of course than jump back to program). If the above is generally true and I get it right, where to final .exe file actually linker saves the functions? After the main() function? And what creates the .exe header? Compiler or Linker? Now, additional capabilities of C, today known as C standart library is set of functions and the declarations of them, that other programmers wrote to extend and simplify use of C language. But these functions like printf() were (or could be?) written in different language, or assembler. And there comes my next question, can be, for example printf() function be written in pure C without use of assembler? I know this is quite big question, but I just mostly want to know, wheather I am right or not. And trust me, I read a lots of articles on the web, and I would not ask you, If I could find these infromation together on one place, in one article. Insted I must piece by piece gather informations, so I am not sure if I am right. Thanks.

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• Query on simple C++ threadpool implementation

  - by ticketman

  Stackoverflow has been a tremendous help to me and I'd to give something back to the community. I have been implementing a simple threadpool using the tinythread C++ portable thread library, using what I have learnt from Stackoverflow. I am new to thread programming, so not that comfortable with mutexes, etc. I have a question best asked after presenting the code (which runs quite well under Linux): // ThreadPool.h class ThreadPool { public: ThreadPool(); ~ThreadPool(); // Creates a pool of threads and gets them ready to be used void CreateThreads(int numOfThreads); // Assigns a job to a thread in the pool, but doesn't start the job // Each SubmitJob call will use up one thread of the pool. // This operation can only be undone by calling StartJobs and // then waiting for the jobs to complete. On completion, // new jobs may be submitted. void SubmitJob( void (*workFunc)(void *), void *workData ); // Begins execution of all the jobs in the pool. void StartJobs(); // Waits until all jobs have completed. // The wait will block the caller. // On completion, new jobs may be submitted. void WaitForJobsToComplete(); private: enum typeOfWorkEnum { e_work, e_quit }; class ThreadData { public: bool ready; // thread has been created and is ready for work bool haveWorkToDo; typeOfWorkEnum typeOfWork; // Pointer to the work function each thread has to call. void (*workFunc)(void *); // Pointer to work data void *workData; ThreadData() : ready(false), haveWorkToDo(false) { }; }; struct ThreadArgStruct { ThreadPool *threadPoolInstance; int threadId; }; // Data for each thread ThreadData *m_ThreadData; ThreadPool(ThreadPool const&); // copy ctor hidden ThreadPool& operator=(ThreadPool const&); // assign op. hidden // Static function that provides the function pointer that a thread can call // By including the ThreadPool instance in the void * parameter, // we can use it to access other data and methods in the ThreadPool instance. static void ThreadFuncWrapper(void *arg) { ThreadArgStruct *threadArg = static_cast<ThreadArgStruct *>(arg); threadArg->threadPoolInstance->ThreadFunc(threadArg->threadId); } // The function each thread calls void ThreadFunc( int threadId ); // Called by the thread pool destructor void DestroyThreadPool(); // Total number of threads available // (fixed on creation of thread pool) int m_numOfThreads; int m_NumOfThreadsDoingWork; int m_NumOfThreadsGivenJobs; // List of threads std::vector<tthread::thread *> m_ThreadList; // Condition variable to signal each thread has been created and executing tthread::mutex m_ThreadReady_mutex; tthread::condition_variable m_ThreadReady_condvar; // Condition variable to signal each thread to start work tthread::mutex m_WorkToDo_mutex; tthread::condition_variable m_WorkToDo_condvar; // Condition variable to signal the main thread that // all threads in the pool have completed their work tthread::mutex m_WorkCompleted_mutex; tthread::condition_variable m_WorkCompleted_condvar; }; cpp file: // // ThreadPool.cpp // #include "ThreadPool.h" // This is the thread function for each thread. // All threads remain in this function until // they are asked to quit, which only happens // when terminating the thread pool. void ThreadPool::ThreadFunc( int threadId ) { ThreadData *myThreadData = &m_ThreadData[threadId]; std::cout << "Hello world: Thread " << threadId << std::endl; // Signal that this thread is ready m_ThreadReady_mutex.lock(); myThreadData->ready = true; m_ThreadReady_condvar.notify_one(); // notify the main thread m_ThreadReady_mutex.unlock(); while(true) { //tthread::lock_guard<tthread::mutex> guard(m); m_WorkToDo_mutex.lock(); while(!myThreadData->haveWorkToDo) // check for work to do m_WorkToDo_condvar.wait(m_WorkToDo_mutex); // if no work, wait here myThreadData->haveWorkToDo = false; // need to do this before unlocking the mutex m_WorkToDo_mutex.unlock(); // Do the work switch(myThreadData->typeOfWork) { case e_work: std::cout << "Thread " << threadId << ": Woken with work to do\n"; // Do work myThreadData->workFunc(myThreadData->workData); std::cout << "#Thread " << threadId << ": Work is completed\n"; break; case e_quit: std::cout << "Thread " << threadId << ": Asked to quit\n"; return; // ends the thread } // Now to signal the main thread that my work is completed m_WorkCompleted_mutex.lock(); m_NumOfThreadsDoingWork--; // Unsure if this 'if' would make the program more efficient // if(NumOfThreadsDoingWork == 0) m_WorkCompleted_condvar.notify_one(); // notify the main thread m_WorkCompleted_mutex.unlock(); } } ThreadPool::ThreadPool() { m_numOfThreads = 0; m_NumOfThreadsDoingWork = 0; m_NumOfThreadsGivenJobs = 0; } ThreadPool::~ThreadPool() { if(m_numOfThreads) { DestroyThreadPool(); delete [] m_ThreadData; } } void ThreadPool::CreateThreads(int numOfThreads) { // Check a thread pool has already been created if(m_numOfThreads > 0) return; m_NumOfThreadsGivenJobs = 0; m_NumOfThreadsDoingWork = 0; m_numOfThreads = numOfThreads; m_ThreadData = new ThreadData[m_numOfThreads]; ThreadArgStruct threadArg; for(int i=0; i<m_numOfThreads; ++i) { threadArg.threadId = i; threadArg.threadPoolInstance = this; // Creates the thread and save in a list so we can destroy it later m_ThreadList.push_back( new tthread::thread( ThreadFuncWrapper, (void *)&threadArg ) ); // It takes a little time for a thread to get established. // Best wait until it gets established before creating the next thread. m_ThreadReady_mutex.lock(); while(!m_ThreadData[i].ready) // Check if thread is ready m_ThreadReady_condvar.wait(m_ThreadReady_mutex); // If not, wait here m_ThreadReady_mutex.unlock(); } } // Adds a job to the batch, but doesn't start the job void ThreadPool::SubmitJob(void (*workFunc)(void *), void *workData) { // Check that the thread pool has been created if(!m_numOfThreads) return; if(m_NumOfThreadsGivenJobs >= m_numOfThreads) return; m_ThreadData[m_NumOfThreadsGivenJobs].workFunc = workFunc; m_ThreadData[m_NumOfThreadsGivenJobs].workData = workData; std::cout << "Submitted job " << m_NumOfThreadsGivenJobs << std::endl; m_NumOfThreadsGivenJobs++; } void ThreadPool::StartJobs() { // Check that the thread pool has been created // and some jobs have been assigned if(!m_numOfThreads || !m_NumOfThreadsGivenJobs) return; // Set 'haveworkToDo' flag for all threads m_WorkToDo_mutex.lock(); for(int i=0; i<m_NumOfThreadsGivenJobs; ++i) m_ThreadData[i].haveWorkToDo = true; m_NumOfThreadsDoingWork = m_NumOfThreadsGivenJobs; // Reset this counter so we can resubmit jobs later m_NumOfThreadsGivenJobs = 0; // Notify all threads they have work to do m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); } void ThreadPool::WaitForJobsToComplete() { // Check that a thread pool has been created if(!m_numOfThreads) return; m_WorkCompleted_mutex.lock(); while(m_NumOfThreadsDoingWork > 0) // Check if all threads have completed their work m_WorkCompleted_condvar.wait(m_WorkCompleted_mutex); // If not, wait here m_WorkCompleted_mutex.unlock(); } void ThreadPool::DestroyThreadPool() { std::cout << "Ask threads to quit\n"; m_WorkToDo_mutex.lock(); for(int i=0; i<m_numOfThreads; ++i) { m_ThreadData[i].haveWorkToDo = true; m_ThreadData[i].typeOfWork = e_quit; } m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); // As each thread terminates, catch them here for(int i=0; i<m_numOfThreads; ++i) { tthread::thread *t = m_ThreadList[i]; // Wait for thread to complete t->join(); } m_numOfThreads = 0; } Example of usage: (this calculates pi-squared/6) struct CalculationDataStruct { int inputVal; double outputVal; }; void LongCalculation( void *theSums ) { CalculationDataStruct *sums = (CalculationDataStruct *)theSums; int terms = sums->inputVal; double sum; for(int i=1; i<terms; i++) sum += 1.0/( double(i)*double(i) ); sums->outputVal = sum; } int main(int argc, char** argv) { int numThreads = 10; // Create pool ThreadPool threadPool; threadPool.CreateThreads(numThreads); // Create thread workspace CalculationDataStruct sums[numThreads]; // Set up jobs for(int i=0; i<numThreads; i++) { sums[i].inputVal = 3000*(i+1); threadPool.SubmitJob(LongCalculation, &sums[i]); } // Run the jobs threadPool.StartJobs(); threadPool.WaitForJobsToComplete(); // Print results for(int i=0; i<numThreads; i++) std::cout << "Sum of " << sums[i].inputVal << " terms is " << sums[i].outputVal << std::endl; return 0; } Question: In the ThreadPool::ThreadFunc method, would better performance be obtained if the following if statement if(NumOfThreadsDoingWork == 0) was included? Also, I'd be grateful of criticisms and ways to improve the code. At the same time, I hope the code is of use to others.

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• Variant datatype library for C

  - by Joey Adams

  Is there a decent open-source C library for storing and manipulating dynamically-typed variables (a.k.a. variants)? I'm primarily interested in atomic values (int8, int16, int32, uint, strings, blobs, etc.), while JSON-style arrays and objects as well as custom objects would also be nice. A major case where such a library would be useful is in working with SQL databases. The most obvious feature of such a library would be a single type for all supported values, e.g.: struct Variant { enum Type type; union { int8_t int8_; int16_t int16_; // ... }; }; Other features might include converting Variant objects to/from C structures (using a binding table), converting values to/from strings, and integration with an existing database library such as SQLite. Note: I do not believe this is question is a duplicate of http://stackoverflow.com/questions/649649/any-library-for-generic-datatypes-in-c , which refers to "queues, trees, maps, lists". What I'm talking about focuses more on making working with SQL databases roughly as smooth as working with them in interpreted languages.

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• Deriving an HTMLElement Object from jQuery Object

  - by Jasconius

  I'm doing a fairly exhaustive series of DOM manipulations where a few elements (specifically form elements) have some events. I am dynamically creating (actually cloning from a source element) several boxes and assigning a change() event to them. The change event executes, and within the context of the event, "this" is the HTML Element Object. What I need to do at this point however is determine a contact for this HTML Element Object. I have these objects stored already as jQuery entities in assorted arrays, but obviously [HTMLElement Object] != [Object Object] And the trick is that I cannot cast $(this) and make a valid comparison since that would create a new object and the pointer would be different. So... I've been banging my head against this for a while. In the past I've been able to circumvent this problem by doing an innerHTML comparison, but in this case the objects I am comparing are 100% identical, just there's lots of them. Therefore I need a solid comparison. This would be easy if I could somehow derive the HTMLElement object from my originating jQuery object. Thoughts, other ideas? Help. :(

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• Minimal-change algorithm which maximises 'swapping'

  - by Kim Bastin

  This is a question on combinatorics from a non-mathematician, so please try to bear with me! Given an array of n distinct characters, I want to generate subsets of k characters in a minimal-change order, i.e. an order in which generation n+1 contains exactly one character that was not in generation n. That's not too hard in itself. However, I also want to maximise the number of cases in which the character that is swapped out in generation n+1 is the same character that was swapped in in generation n. To illustrate, for n=7, k=3: abc abd abe* abf* abg* afg aeg* adg* acg* acd ace* acf* aef adf* ade bde bdf bef bcf* bce bcd* bcg* bdg beg* bfg* cfg ceg* cdg* cde cdf* cef def deg dfg efg The asterisked strings indicate the case I want to maximise; e.g. the e that is new in generation 3, abe, replaces a d that was new in generation 2, abd. It doesn't seem possible to have this happen in every generation, but I want it to happen as often as possible. Typical array sizes that I use are 20-30 and subset sizes around 5-8. I'm using an odd language, Icon (or actually its derivative Unicon), so I don't expect anyone to post code that I can used directly. But I will be grateful for answers or hints in pseudo-code, and will do my best to translate C etc. Also, I have noticed that problems of this kind are often discussed in terms of arrays of integers, and I can certainly apply solutions posted in such terms to my own problem. Thanks Kim Bastin

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• Access denied error on select into outfile using Zend

  - by Peter

  Hi, I'm trying to make a dump of a MySQL table on the server and I'm trying to do this in Zend. I have a model/mapper/dbtable structure for all my connections to my tables and I'm adding the following code to the mappers: public function dumpTable() { $db = $this->getDbTable()->getAdapter(); $name = $this->getDbTable()->info('name'); $backupFile = APPLICATION_PATH . '/backup/' . date('U') . '_' . $name . '.sql'; $query = "SELECT * INTO OUTFILE '$backupFile' FROM $name"; $db->query( $query ); } This should work peachy, I thought, but Message: Mysqli prepare error: Access denied for user 'someUser'@'localhost' (using password: YES) is what this results in. I checked the user rights for someUser and he has all the rights to the database and table in question. I've been looking around here and on the net in general and usually turning on "all" the rights for the user seems to be the solution, but not in my case (unless I'm overlooking something right now with my tired eyes + I don't want to turn on "all" on my production server). What am I doing wrong here? Or, does anybody know a more elegant way to get this done in Zend?

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• create app that has plugin which contains PyQt widget

  - by brian

  I'm writing an application that will use plugins. In the plugin I want to include a widget that allows the options for that plugin to be setup. The plugin will also include methods to operate on the data. What is is the best way to include a widget in a plugin? Below is pseudo code for what I've tried to do. My original plan was to make the options widget: class myOptionsWidget(QWidget): “”” create widget for plug in options “”” …. Next I planned on including the widget in my plugin: class myPlugin def __init__(self): self.optionWidget = myOptionsWidget() self.pluginNum = 1 …. def getOptionWidget(self): return(self.optionWidget) Then at the top level I'd do something like a = myPlugin() form = createForm(option=a.getOptionWidget()) … where createForm would create the form and include my plugin options widget. But when I try "a = myPlugin()" I get the error "QWidget: Must construct a QApplication before a QpaintDevice" so this method won't work. I know I would store the widget as a string and call eval on it but I'd rather not do that in case later on I want to convert the program to C++. What is the best way to write a plugin that includes a widget that has the options? Brian

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• Insert video clip in a lyx presentation and play it in GNU/Linux.

  - by Orjanp

  How can I insert a video clip into a presentation created in Lyx? Have seen http://www.latex-community.org/forum/viewtopic.php?f=19&t=48. It works, but there the video starts in the background in an external player. I would prefer it to be played in the presentation itself. If an external player is used it it should at least start in the foreground. But the presentation takes the foreground. Using evince in GNU/linux as pdf viewer. Beamer is used as a presentation template. Is it possible to play a video file in an embedded player in the presentation itself? Created an example presentation. The code is found below. \documentclass[english]{beamer} \usepackage{mathptmx} \usepackage[T1]{fontenc} \usepackage[latin9]{inputenc} \usepackage{amsmath} \usepackage{amssymb} \makeatletter %%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Textclass specific LaTeX commands. % this default might be overridden by plain title style \newcommand\makebeamertitle{\frame{\maketitle}}% \AtBeginDocument{ \let\origtableofcontents=\tableofcontents \def\tableofcontents{\@ifnextchar[{\origtableofcontents}{\gobbletableofcontents}} \def\gobbletableofcontents#1{\origtableofcontents} } \makeatletter \long\def\lyxframe#1{\@lyxframe#1\@lyxframestop}% \def\@lyxframe{\@ifnextchar<{\@@lyxframe}{\@@lyxframe<*>}}% \def\@@lyxframe<#1>{\@ifnextchar[{\@@@lyxframe<#1>}{\@@@lyxframe<#1>[]}} \def\@@@lyxframe<#1>[{\@ifnextchar<{\@@@@@lyxframe<#1>[}{\@@@@lyxframe<#1>[<*>][}} \def\@@@@@lyxframe<#1>[#2]{\@ifnextchar[{\@@@@lyxframe<#1>[#2]}{\@@@@lyxframe<#1>[#2][]}} \long\def\@@@@lyxframe<#1>[#2][#3]#4\@lyxframestop#5\lyxframeend{% \frame<#1>[#2][#3]{\frametitle{#4}#5}} \makeatother \def\lyxframeend{} % In case there is a superfluous frame end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%% User specified LaTeX commands. \usetheme{Warsaw} \usepackage{hyperref} \makeatother \usepackage{babel} \begin{document} \title{Testing video} \makebeamertitle \lyxframeend{}\section{Testing video} \lyxframeend{}\subsection{Testing video} \lyxframeend{}\lyxframe{Testing video} \href{run:video.wmv}{Movie} \appendix \lyxframeend{} \end{document}

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