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• Robotlegs: Warning: Injector already has a rule for type

  - by MikeW

  I have a bunch of warning messages like this appear when using Robotlegs/Signals. Everytime this command class executes, which is every 2-3 seconds ..this message displays below If you have overwritten this mapping intentionally you can use "injector.unmap()" prior to your replacement mapping in order to avoid seeing this message. Warning: Injector already has a rule for type "mx.messaging.messages::IMessage", named "". The command functions fine otherwise but I think I'm doing something wrong anyhow. public class MessageReceivedCommand extends SignalCommand { [Inject] public var message:IMessage; ...etc.. do something with message.. } the application context doesnt map IMessage to this command, as I only see an option to mapSignalClass , besides the payload is received fine. Wonder if anyone knows how I might either fix or suppress this message. I've tried calling this as the warning suggests injector.unmap(IMessage, "") but I receive an error - no mapping found for ::IMessage named "". Thanks Edit: A bit more info about the error Here is the signal that I dispatch to the command public class GameMessageSignal extends Signal { public function GameMessageSignal() { super(IMessage); } } which is dispatched from a IPushDataService class gameMessage.dispatch(message.message); and the implementation is wired up in the app context via injector.mapClass(IPushDataService, PushDataService); along with the signal signalCommandMap.mapSignalClass(GameMessageSignal, MessageReceivedCommand); Edit #2: Probably good to point out also I inject an instance of GameMessageSignal into IPushDataService public class PushDataService extends BaseDataService implements IPushDataService { [Inject] public var gameMessage:GameMessageSignal; //then private function processMessage(message:MessageEvent):void { gameMessage.dispatch(message.message); } } Edit:3 The mappings i set up in the SignalContext: injector.mapSingleton(IPushDataService); injector.mapClass(IPushDataService, PushDataService);

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• String comparison in Python: is vs. ==

  - by Coquelicot

  I noticed a Python script I was writing was acting squirrelly, and traced it to an infinite loop, where the loop condition was "while line is not ''". Running through it in the debugger, it turned out that line was in fact ''. When I changed it to != rather than 'is not', it worked fine. I did some searching, and found this question, the top answer to which seemed to be just what I needed. Except the answer it gave was counter to my experience. Specifically, the answerer wrote: For all built-in Python objects (like strings, lists, dicts, functions, etc.), if x is y, then x==y is also True. I double-checked the type of the variable, and it was in fact of type str (not unicode or something). Is his answer just wrong, or is there something else afoot? Also, is it generally considered better to just use '==' by default, even when comparing int or Boolean values? I've always liked to use 'is' because I find it more aesthetically pleasing and pythonic (which is how I fell into this trap...), but I wonder if it's intended to just be reserved for when you care about finding two objects with the same id.

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• Replacing symbol from object file at compile time. For example swapping out main

  - by Anthony Sottile

  Here's the use case: I have a .cpp file which has functions implemented in it. For sake of example say it has the following: [main.cpp] #include <iostream> int foo(int); int foo(int a) { return a * a; } int main() { for (int i = 0; i < 5; i += 1) { std::cout << foo(i) << std::endl; } return 0; } I want to perform some amount of automated testing on the function foo in this file but would need to replace out the main() function to do my testing. Preferably I'd like to have a separate file like this that I could link in over top of that one: [mymain.cpp] #include <iostream> #include <cassert> extern int foo(int); int main() { assert(foo(1) == 1); assert(foo(2) == 4); assert(foo(0) == 0); assert(foo(-2) == 4); return 0; } I'd like (if at all possible) to avoid changing the original .cpp file in order to do this -- though this would be my approach if this is not possible: do a replace for "(\s)main\s*\(" == "\1__oldmain\(" compile as usual. The environment I am targeting is a linux environment with g++.

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• Calling a WPF Appliaction and modify exposed properties?

  - by Justin

  I have a WPF Keyboard Application, it is developed in such a way that an application could call it and modify its properties to adapt the Keyboard to do what it needs to. Right now I have a file *.Keys.Set which tells the appliaction (on open) to style itself according to that new style. I know this file could be passed as a command line argument into the appliaction. That would not be a problem. My concern is, is thier a way via a managed environment to change the properties of the executable as long as they are exposed properly, an example: 'Creates a new instance of the Keyboard Appliaction Dim e_key as new WpfAppliaction("C:\egt\components\keyboard.exe") 'Sets the style path e_key.SetStylePath("c:\users\joe\apps\me\default.keys.set") e_key.Refresh() 'Applies the style e_key.HideMenu() 'Hides the menu e_key.ShowDeck("PIN") 'Shows the custom "deck" of keyboard keys the developer 'Created in the style appliaction. ''work with events and resposne 'Clear the instance from memory e_key.close e_key.dispose e_key = nothing This would allow my application to become easily accessible to other Touch Screen Application Developers, allowing them to use my key_board and keep the functionality they need. It seems like it might be possible because (name of executable).application shows all the exposed functions, properties, and values. I just have never done this before. Any help would be appreciated, thank you in advance.

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• File IO with Streams - Best Memory Buffer Size

  - by AJ

  I am writing a small IO library to assist with a larger (hobby) project. A part of this library performs various functions on a file, which is read / written via the FileStream object. On each StreamReader.Read(...) pass, I fire off an event which will be used in the main app to display progress information. The processing that goes on in the loop is vaired, but is not too time consuming (it could just be a simple file copy, for example, or may involve encryption...). My main question is: What is the best memory buffer size to use? Thinking about physical disk layouts, I could pick 2k, which would cover a CD sector size and is a nice multiple of a 512 byte hard disk sector. Higher up the abstraction tree, you could go for a larger buffer which could read an entire FAT cluster at a time. I realise with today's PC's, I could go for a more memory hungry option (a couple of MiB, for example), but then I increase the time between UI updates and the user perceives a less responsive app. As an aside, I'm eventually hoping to provide a similar interface to files hosted on FTP / HTTP servers (over a local network / fastish DSL). What would be the best memory buffer size for those (again, a "best-case" tradeoff between perceived responsiveness vs. performance).

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• Flex 3 (Action Script): How to access a function from a loaded swf-file ?

  - by Trantec

  Hi, i load in ActionScript a swf file. So far no Problem, but I didn't found a way to access one of it's functions, the best thing would be if I could access the main function in the mxml part of the swf. Here is the code of the main-mxml file that belongs to the swf that should load and access another swf: <?xml version="1.0" encoding="utf-8"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute" initialize="basket();"> <mx:Script> <![CDATA[ import mx.controls.SWFLoader; private function basket(): void { var swfLoader: SWFLoader = new SWFLoader(); swfLoader.addEventListener( Event.COMPLETE, handleSWFLoaded ); try { swfLoader.load( "../../data/InternalSWF.swf" ); } catch (error: Error) { trace( "Couldn't load file !" ); } } private function handleSWFLoaded( event: Event ): void { var swfApp:* = event.target.content; // This both ways don't work... //if (swfApp.hasOwnProperty("initApp")) { // var initApp:Function = (swfApp["initApp"] as Function); // initApp(); //} // swfApp.initApp(); } ]]> </mx:Script> <mx:Text id="output" width="100%" textAlign="center" /> </mx:Application> The if-Statement "if (swfApp.hasOwnProperty("initApp")) {" is never true and the call "swfApp.initApp()" says that this function does not exist. In the original version I added event listeners for HTTPStatusEvent.HTTP_STATUS, IOErrorEvent.IO_ERROR and SecurityErrorEvent.SECURITY_ERROR. But except for HTTP_STATUS = 0 none of them are called. Is the whole idea of how i try to do this wrong ?

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• Loop elements with Jquery and call Omniture s.tl() function to track

  - by ilovewebdev

  Hi, i have a page with a list of items. Each item has a print now link (a.printMe) to print each item. At the end of the list, there's a print all link (a.printAll) to print all items. I want to track number of times an item was printed. If a.printAll link is clicked, then i will send all the item's tracking value to Omniture. I added tracking string into individual item's a.printMe href attribute and track with the following functions: $('a.printMe').click(function() { var value = $(this).attr('href'); track(value); }); $('a.printAll').click(function() { $('a.printMe').each(function() { this.click(); }); // works in IE only. IE 6-8 }); function track(value) { var s = s_gi('account'); s.prop10 = value; s.linkTrackVars = 'prop10'; s.tl(true, 'o'); } The problem is only the last item (in the list) has its value sent to Omniture when i clicked on a.printAll. I finally got the above to work in IE but not Firefox. Anyone encounter this before?

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• How to prevent multiple definitions in C?

  - by Jordi

  I'm a C newbie and I was just trying to write a console application with Code::Blocks. Here's the (simplified) code: main.c: #include <stdio.h> #include <stdlib.h> #include "test.c" // include not necessary for error in Code::Blocks int main() { //t = test(); // calling of method also not necessary return 0; } test.c: void test() {} When I try to build this program, it gives the following errors: *path*\test.c|1|multiple definition of `_ test'| obj\Debug\main.o:*path*\test.c|1|first defined here| There is no way that I'm multiply defining test (although I don't know where the underscore is coming from) and it seems highly unlikely that the definition is somehow included twice. This is all the code there is. I've ruled out that this error is due to some naming conflict with other functions or files being called test or test.c. Note that the multiple and the first definition are on the same line in the same file. Does anyone know what is causing this and what I can do about it? Thanks!

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• Mootools Form Post Problem, Abort increasingly+1 with each request

  - by Naresh

  Hi all, i'm using Mootools 1.2. Ihave 15 Forms with same name only change in their id's like form1, form2, form3, ... ,form15 same with their elements. i need to submit all forms by ajax. For that purpos i make a function and call them on each functions onClick event. function is function addStepConfiguration(id,mystrip,comment,error,submitid,i) { $(id).addEvent('submit', function(e) { e.stop(); $(submitid).setStyle('display','none'); loading_Img(i); this.set('send', { onComplete: function(responseText) { $('loading_img'+i).innerHTML = ''; SplittedResText = responseText.split("|"); if(SplittedResText[1]=='undefined') { $(error).innerHTML=SplittedResText[0]; } else { $(comment).innerHTML=SplittedResText[0]; $(mystrip).set('class',SplittedResText[1]); removeMsg.delay(20,'',error); removeMsg.delay(1500,'',comment); } $(submitid).setStyle('display','block'); } }); this.send(); }); } When i submit a form say first one then it submitted and give response normally, but in second time without page refresh, it abort the request one time. in third attempt it abort 2 times..then go on +1 each time. It gives no error, just abort and again request automatically. i can't understand what is the problem. please any one can help me.

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• Proper Memory Management for Objective-C Method

  - by Justin

  Hi, I'm programming an iPhone app and I had a question about memory management in one of my methods. I'm still a little new to managing memory manually, so I'm sorry if this question seems elementary. Below is a method designed to allow a number pad to place buttons in a label based on their tag, this way I don't need to make a method for each button. The method works fine, I'm just wondering if I'm responsible for releasing any of the variables I make in the function. The application crashes if I try to release any of the variables, so I'm a little confused about my responsibility regarding memory. Here's the method: FYI the variable firstValue is my label, it's the only variable not declared in the method. -(IBAction)inputNumbersFromButtons:(id)sender { UIButton *placeHolderButton = [[UIButton alloc] init]; placeHolderButton = sender; NSString *placeHolderString = [[NSString alloc] init]; placeHolderString = [placeHolderString stringByAppendingString:firstValue.text]; NSString *addThisNumber = [[NSString alloc] init]; int i = placeHolderButton.tag; addThisNumber = [NSString stringWithFormat:@"%i", i]; NSString *newLabelText = [[NSString alloc] init]; newLabelText = [placeHolderString stringByAppendingString:addThisNumber]; [firstValue setText:newLabelText]; //[placeHolderButton release]; //[placeHolderString release]; //[addThisNumber release]; //[newLabelText release]; } The application works fine with those last four lines commented out, but it seems to me like I should be releasing these variables here. If I'm wrong about that I'd welcome a quick explanation about when it's necessary to release variables declared in functions and when it's not. Thanks.

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• Global name not defined error in Django/Python trying to set foreignkey

  - by Mark

  Summary: I define a method createPage within a file called PageTree.py that takes a Source model object and a string. The method tries to generate a Page model object. It tries to set the Page model object's foreignkey to refer to the Source model object which was passed in. This throws a NameError exception! I'm trying to represent a website which is structured like a tree. I define the Django models Page and Source, Page representing a node on the tree and Source representing the contents of the page. (You can probably skip over these, this is a basic tree implementation using doubly linked nodes). class Page(models.Model): name = models.CharField(max_length=50) parent = models.ForeignKey("self", related_name="children", null=True); firstChild = models.ForeignKey("self", related_name="origin", null=True); nextSibling = models.ForeignKey("self", related_name="prevSibling", null=True); previousSibling = models.ForeignKey("self", related_name="nxtSibling", null=True); source = models.ForeignKey("Source"); class Source(models.Model): #A source that is non dynamic will be refered to as a static source #Dynamic sources contain locations that are names of functions #Static sources contain locations that are places on disk name = models.CharField(primary_key=True, max_length=50) isDynamic = models.BooleanField() location = models.CharField(max_length=100); I've coded a python program called PageTree.py which allows me to request nodes from the database and manipulate the structure of the tree. Here is the trouble making method: def createPage(pageSource, pageName): page = Page() page.source = pageSource page.name = pageName page.save() return page I'm running this program in a shell through manage.py in Windows 7 manage.py shell from mysite.PageManager.models import Page, Source from mysite.PageManager.PageTree import * ... create someSource = Source(), populate the fields, and save it ... createPage(someSource, "test") ... NameError: global name 'source' is not defined When I type in the function definition for createPage into the shell by hand, the call works without error. This is driving me bonkers and help is appreciated.

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• Accessing the calling object into ajax response... (not the ajax call)

  - by Nishchay Sharma

  I have an object of type Application (defined by me). Whenever an object of this type is created, it automatically loads a php file say "start.php" using jquery ajax and assign the response to a div say "Respo". Now what i want is to access the Application object from that Respo div. Unfortunately, i have no clue how to do this... in my ajax call: function Application(options) { ....... var appObj=this; $.ajax({ url:appObj.location, //Already defined success:function(data) { $("#respo").html(data); } }); } Now in my Respo division i want to access that Application object... I tried: alert(this) but it resulted in an object of DOMWindow... i tried editing success function as: function Application(options) { ....... var appObj=this; $.ajax({ url:appObj.location, //Already defined success:function(data) { $("#respo").html("<script type='text/javascript'>var Self="+appObj+"</script>"); $("#respo").html(data); } }); } But i ended nowhere. :( Although if i assign "var Self='nishchay';" then alerting Self from start.php gives nishchay but i am not able to assign the calling object of Application type to the Self variable. It is the only way I cud think of. :\ Please help me... actually my object has some editing functions to control itself - its look and feel and some other options. I want the code loaded by object to control the object itself. Please help me.. Thanks in advance. Nishchay

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• Data structure to build and lookup set of integer ranges

  - by actual

  I have a set of uint32 integers, there may be millions of items in the set. 50-70% of them are consecutive, but in input stream they appear in unpredictable order. I need to: Compress this set into ranges to achieve space efficient representation. Already implemented this using trivial algorithm, since ranges computed only once speed is not important here. After this transformation number of resulting ranges is typically within 5 000-10 000, many of them are single-item, of course. Test membership of some integer, information about specific range in the set is not required. This one must be very fast -- O(1). Was thinking about minimal perfect hash functions, but they do not play well with ranges. Bitsets are very space inefficient. Other structures, like binary trees, has complexity of O(log n), worst thing with them that implementation make many conditional jumps and processor can not predict them well giving poor performance. Is there any data structure or algorithm specialized in integer ranges to solve this task?

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• CodeIgniter - Image Validation & Thumbnailing

  - by Sebhael

  I'm currently trying to create a function that validates and creates thumbnails for images on upload - but I'm quite lost on what I'm doing. I'm assuming I'm off on my terminology so I'm not really getting any search results to help point me in the right direction. My playground is a form with 6 upload fields that are required. One of these fields is for a simple 32x32 icon image, another a portrait orientation (most likely) photo, and then 4 standard desktop screenshots -- and I'm using CodeIgniter as my framework. I would like to create a function that validates/thumbnails images, and only have to call it on the validation if at all possible. I know I can achieve this per-image, since the documentation for CI is quite through on this - but to reduce redundancy I'm looking for the better option. Outside of that, I don't even actually understand in full how to manipulate images unless it's just $this-input-post('field') - then calling all functions onto this? I don't know, I'm confused and posting on the actual CI forums has yielded me nothing - so all I'm really looking for is a point in the right direction to understanding what I'm trying to achieve here. This also all might not make any sense, I know it doesn't to me - but I can explain more if needed. Thanks in advance.

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• Why isn't our c# graphics code working any more?

  - by Jared

  Here's the situation: We have some generic graphics code that we use for one of our projects. After doing some clean-up of the code, it seems like something isn't working anymore (The graphics output looks completely wrong). I ran a diff against the last version of the code that gave the correct output, and it looks like we changed one of our functions as follows: static public Rectangle FitRectangleOld(Rectangle rect, Size targetSize) { if (rect.Width <= 0 || rect.Height <= 0) { rect.Width = targetSize.Width; rect.Height = targetSize.Height; } else if (targetSize.Width * rect.Height > rect.Width * targetSize.Height) { rect.Width = rect.Width * targetSize.Height / rect.Height; rect.Height = targetSize.Height; } else { rect.Height = rect.Height * targetSize.Width / rect.Width; rect.Width = targetSize.Width; } return rect; } to static public Rectangle FitRectangle(Rectangle rect, Size targetSize) { if (rect.Width <= 0 || rect.Height <= 0) { rect.Width = targetSize.Width; rect.Height = targetSize.Height; } else if (targetSize.Width * rect.Height > rect.Width * targetSize.Height) { rect.Width *= targetSize.Height / rect.Height; rect.Height = targetSize.Height; } else { rect.Height *= targetSize.Width / rect.Width; rect.Width = targetSize.Width; } return rect; } All of our unit tests are all passing, and nothing in the code has changed except for some syntactic shortcuts. But like I said, the output is wrong. We'll probably just revert back to the old code, but I'm curious if anyone has any idea what's going on here. Thanks.

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• Embedded scripting engine in .Net app

  - by Nate

  I am looking to replace an old control being used for scripting an application. The control used to be called SAX Basic, but is now called WinWrap. It provides us with two primary functions. 1) It's a scripting engine (VB) 2) It has a GUI for developing and debugging scripts that get run in the hosting application. The first feature it provides is actually pretty easy to replace. There are so many great methods of running just about any kind of code at runtime that it's almost a non-issue. Just about any language targeting the .Net runtime will work for us. We've looked at running C#, PowerShell, VB.Net, IronPython, etc. I've also taken a brief look at Lua and F#, but honestly the language isn't the biggest barrier here. Now, for the hard part that seems to keep getting me stuck. We want a code editor, and debugger. Something simple, not unlike PowerShell's ISE would be fine. Just as long as a file could be created, saved, debugged and executed. I'm currently looking into Visual Studio 2010 Shell (Isolated) and I'm also looking at the feasibility of embedding PowerShell ISE in my application. Are there any other editor's I could embed/use in my application? Purchasing a product is not out of the question. It comes down to a combination of ease of use, how well it meets our needs, and how simple deployment and licensing is for developers. Thanks for the pointers

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• Setting up a view to draw to in Objective-C (iPhone) ?

  - by Johannes Jensen

  Okay, so, I'm all new to iPhone and stuff, but I'm not even at programming, I have many years of experience with ActionScript 2.0 and 3.0, I want to set up a view, that I can also pass variables to. The view is gonna draw everything with Quartz. I tried to make another game where I tried to add a pointer to a NSMutableArray to the view class, but it didn't work cause I didn't know how to store an actual class. I wanted to do like: [myView setNeedsDisplay]; but I had to do [(View*)self.view setNeedsDisplay]; didn't really work out in the end... Okay, so now I got: - (void) viewDidLoad { [super viewDidLoad]; viewClass = [[View class] retain]; gameView = [[[viewClass alloc] initWithFrame: CGRectZero] retain]; [gameView setNeedsDisplay]; } This is in my drawInContext:context, which is fired by drawRect: Also, my drawRect does [self drawInContext: UIGraphicsGetCurrentContext()]; CGContextSetStrokeColorWithColor(context, [[UIColor blackColor] CGColor]); CGContextSetLineWidth(context, 3.0); CGContextSetLineCap(context, kCGLineCapRound); CGContextSetLineJoin(context, kCGLineJoinRound); CGMutablePathRef aPath = CGPathCreateMutable(); CGPathMoveToPoint(aPath, nil, 5, 5); CGPathAddLineToPoint(aPath, nil, 45, 43); CGContextAddPath(context, aPath); CGContextStrokePath(context); Nothing happens. Help? Oh yeah, I get this error: : invalid context for each time I use those functions. :[ Thanks!

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• what patern is layerd architechture in asp.net ?

  - by haansi

  Hi, I am a asp.net developer and don't know much about patterns and architecture. I will very thankful if you can please guide me here. In my web applications I use 4 layers. Web site project (having web forms + code behind cs files, user controls + code behind cs files, master pages + code behind cs files) CustomTypesLayer a class library (having custom types, enumerations, DTOs, constructers, get, set and validations) BusinessLogicLayer a class library (having all business logic, rules and all calls to DAL functions) DataAccessLayer a class library( having just classes communicating to database.) -My user interface just calls BusinessLogicLayer. BusinessLogicLayer do proecessign in it self and for data it calls DataAccessLayer funtions. -Web forms do not calls directly DAL. -CustomTypesLayer is shared by all layers. Please guide me is this approach a pattern ? I though it may be MVC or MVP but pages have there code behind files as well which are confusing me. If it is no patren is it near to some patren ? pleaes guide thanks

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• C++: Constructor/destructor unresolved when not inline?

  - by Anamon

  In a plugin-based C++ project, I have a TmpClass that is used to exchange data between the main application and the plugins. Therefore the respective TmpClass.h is included in the abstract plugin interface class that is included by the main application project, and implemented by each plugin. As the plugins work on STL vectors of TmpClass instances, there needs to be a default constructor and destructor for the TmpClass. I had declared these in TmpClass.h: class TmpClass { TmpClass(); ~TmpClass(); } and implemented them in TmpClass.cpp. TmpClass::~TmpClass() {} TmpClass::TmpClass() {} However, when compiling plugins this leads to the linker complaining about two unresolved externals - the default constructor and destructor of TmpClass as required by the std::vector<TmpClass> template instantiation - even though all other functions I declare in TmpClass.h and implement in TmpClass.cpp work. As soon as I remove the (empty) default constructor and destructor from the .cpp file and inline them into the class declaration in the .h file, the plugins compile and work. Why is it that the default constructor and destructor have to be inline for this code to compile? Why does it even maatter? (I'm using MSVC++8).

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• C++ class derivation and superconstructor confusion

  - by LukeN

  Hey, in a tutorial C++ code, I found this particular piece of confusion: PlasmaTutorial1::PlasmaTutorial1(QObject *parent, const QVariantList &args) : Plasma::Applet(parent, args), // <- Okay, Plasma = namespace, Applet = class m_svg(this), // <- A member function of class "Applet"? m_icon("document") // <- ditto? { m_svg.setImagePath("widgets/background"); // this will get us the standard applet background, for free! setBackgroundHints(DefaultBackground); resize(200, 200); } I'm not new to object oriented programming, so class derivation and super-classes are nothing complicated, but this syntax here got me confused. The header file defines the class like this: class PlasmaTutorial1 : public Plasma::Applet { Similar to above, namespace Plasma and class Applet. But what's the public doing there? I fear that I already know the concept but don't grasp the C++ syntax/way of doing it. In this question I picked up that these are called "superconstructors", at least that's what stuck in my memory, but I don't get this to the full extend. If we glance back at the first snippet, we see Constructor::Class(...) : NS::SuperClass(...), all fine 'till here. But what are m_svg(this), m_icon("document") doing there? Is this some kind of method to make these particular functions known to the derivated class? Is this part of C++ basics or more immediate? While I'm not completly lost in C++, I feel much more at home in C :) Most of the OOP I have done so far was done in D, Ruby or Python. For example in D I would just define class MyClass : MySuperClass, override what I needed to and call the super class' constructor if I'd need to.

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• Speed comparison - Template specialization vs. Virtual Function vs. If-Statement

  - by Person

  Just to get it out of the way... Premature optimization is the root of all evil Make use of OOP etc. I understand. Just looking for some advice regarding the speed of certain operations that I can store in my grey matter for future reference. Say you have an Animation class. An animation can be looped (plays over and over) or not looped (plays once), it may have unique frame times or not, etc. Let's say there are 3 of these "either or" attributes. Note that any method of the Animation class will at most check for one of these (i.e. this isn't a case of a giant branch of if-elseif). Here are some options. 1) Give it boolean members for the attributes given above, and use an if statement to check against them when playing the animation to perform the appropriate action. Problem: Conditional checked every single time the animation is played. 2) Make a base animation class, and derive other animations classes such as LoopedAnimation and AnimationUniqueFrames, etc. Problem: Vtable check upon every call to play the animation given that you have something like a vector<Animation>. Also, making a separate class for all of the possible combinations seems code bloaty. 3) Use template specialization, and specialize those functions that depend on those attributes. Like template<bool looped, bool uniqueFrameTimes> class Animation. Problem: The problem with this is that you couldn't just have a vector<Animation> for something's animations. Could also be bloaty. I'm wondering what kind of speed each of these options offer? I'm particularly interested in the 1st and 2nd option because the 3rd doesn't allow one to iterate through a general container of Animations. In short, what is faster - a vtable fetch or a conditional?

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• How can I avoid encoding mixups of strings in a C/C++ API?

  - by Frerich Raabe

  I'm working on implementing different APIs in C and C++ and wondered what techniques are available for avoiding that clients get the encoding wrong when receiving strings from the framework or passing them back. For instance, imagine a simple plugin API in C++ which customers can implement to influence translations. It might feature a function like this: const char *getTranslatedWord( const char *englishWord ); Now, let's say that I'd like to enforce that all strings are passed as UTF-8. Of course I'd document this requirement, but I'd like the compiler to enforce the right encoding, maybe by using dedicated types. For instance, something like this: class Word { public: static Word fromUtf8( const char *data ) { return Word( data ); } const char *toUtf8() { return m_data; } private: Word( const char *data ) : m_data( data ) { } const char *m_data; }; I could now use this specialized type in the API: Word getTranslatedWord( const Word &englishWord ); Unfortunately, it's easy to make this very inefficient. The Word class lacks proper copy constructors, assignment operators etc.. and I'd like to avoid unnecessary copying of data as much as possible. Also, I see the danger that Word gets extended with more and more utility functions (like length or fromLatin1 or substr etc.) and I'd rather not write Yet Another String Class. I just want a little container which avoids accidental encoding mixups. I wonder whether anybody else has some experience with this and can share some useful techniques. EDIT: In my particular case, the API is used on Windows and Linux using MSVC 6 - MSVC 10 on Windows and gcc 3 & 4 on Linux.

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• How am i overriding this C++ inherited member function without the virtual keyword being used?

  - by Gary Willoughby

  I have a small program to demonstrate simple inheritance. I am defining a Dog class which is derived from Mammal. Both classes share a simple member function called ToString(). How is Dog overriding the implementation in the Mammal class, when i'm not using the virtual keyword? (Do i even need to use the virtual keyword to override member functions?) mammal.h #ifndef MAMMAL_H_INCLUDED #define MAMMAL_H_INCLUDED #include <string> class Mammal { public: std::string ToString(); }; #endif // MAMMAL_H_INCLUDED mammal.cpp #include <string> #include "mammal.h" std::string Mammal::ToString() { return "I am a Mammal!"; } dog.h #ifndef DOG_H_INCLUDED #define DOG_H_INCLUDED #include <string> #include "mammal.h" class Dog : public Mammal { public: std::string ToString(); }; #endif // DOG_H_INCLUDED dog.cpp #include <string> #include "dog.h" std::string Dog::ToString() { return "I am a Dog!"; } main.cpp #include <iostream> #include "dog.h" using namespace std; int main() { Dog d; std::cout << d.ToString() << std::endl; return 0; } output I am a Dog! I'm using MingW on Windows via Code::Blocks.

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• How can I write to a single xml file from two programs at the same time?

  - by Tom Bushell

  We recently started working with XML files, after many years of experience with the old INI files. My coworker found some CodeProject sample code that uses System.Xml.XmlDocument.Save. We are getting exceptions when two programs try to write to the same file at the same time. System.IO.IOException: The process cannot access the file 'C:\Test.xml' because it is being used by another process. This seems obvious in hindsight, but we had not anticipated it because accessing INI files via the Win32 API does not have this limitation. I assume there's some arbitration done by the Win32 calls that work at a higher level than the the XmlDocument.Save method. I'm hoping there are higher level XML routines somewhere in the .Net library that work similarily to the Win32 functions, but don't know where to start looking. Or maybe we can set up our file access permissions to allow multiple programs to write to the same file? Time is short (like almost all SW projects), and if we can't find a solution quickly, we'll have to hold our noses and go back to INI files.

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• Noise with multi-threaded raytracer

  - by herber88

  This is my first multi-threaded implementation, so it's probably a beginners mistake. The threads handle the rendering of every second row of pixels (so all rendering is handled within each thread). The problem persists if the threads render the upper and lower parts of the screen respectively. Both threads read from the same variables, can this cause any problems? From what I've understood only writing can cause concurrency problems... Can calling the same functions cause any concurrency problems? And again, from what I've understood this shouldn't be a problem... The only time both threads write to the same variable is when saving the calculated pixel color. This is stored in an array, but they never write to the same indices in that array. Can this cause a problem? Multi-threaded rendered image (Spam prevention stops me from posting images directly..) Ps. I use the exactly same implementation in both cases, the ONLY difference is a single vs. two threads created for the rendering.

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