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  • c++11 atomic ordering: extended total order memory_order_seq_cst for locks

    - by itaj
    There's this note in c++11 29.3-p3: [ Note: Although it is not explicitly required that S include locks, it can always be extended to an order that does include lock and unlock operations, since the ordering between those is already included in the "happens before" ordering. - end note ] What does it mean by "always"? I can understand that any certain implementation can be designed to support such an extended S. But in some general implementation that wasn't designed for it, I don't see that S can be extended so. I had sent this question to comp.std.c++ but got no answers there. http://groups.google.com/group/comp.std.c++/browse_frm/thread/5242fa70d0594d1b#

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  • "Introduction to Computer Science and Programming" for a beginner.

    - by Richard
    Hi everyone! Im new here and also new to developing software and programming, and with new I mean 0 experience or schooling for it. As Im currently studying medicine via internet and I use a computer on an average of about 8-9 hours a day, this has lead me to get very interested in programming. I got a link from a fellow Redditor and I got some questions before I dive into this project. http://ocw.mit.edu/OcwWeb/Electrical-Engineering-and-Computer-Science/6-00Fall-2008/CourseHome/index.htm Is this too much/hard for a beginner? Is Python™ programming language the way to go or would I be better off learning some other kind of language to begin with? What other ways of learning basic programming by myself is there? Are there any better ways for a complete beginner to start off? Thank you for your time!

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  • Counting bits set in a .Net BitArray Class

    - by Sam
    I am implementing a library where I am extensively using the .Net BitArray class and need an equivalent to the Java BitSet.Cardinality() method, i.e. a method which returns the number of bits set. I was thinking of implementing it as an extension method for the BitArray class. The trivial implementation is to iterate and count the bits set (like below), but I wanted a faster implementation as I would be performing thousands of set operations and counting the answer. Is there a faster way than the example below? count = 0; for (int i = 0; i < mybitarray.Length; i++) { if (mybitarray [i]) count++; }

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  • How to approach copying objects with smart pointers as class attributes?

    - by tomislav-maric
    From the boost library documentation I read this: Conceptually, smart pointers are seen as owning the object pointed to, and thus responsible for deletion of the object when it is no longer needed. I have a very simple problem: I want to use RAII for pointer attributes of a class that is Copyable and Assignable. The copy and assignment operations should be deep: every object should have its own copy of the actual data. Also, RTTI needs to be available for the attributes (their type may also be determined at runtime). Should I be searching for an implementation of a Copyable smart pointer (the data are small, so I don't need Copy on Write pointers), or do I delegate the copy operation to the copy constructors of my objects as shown in this answer? Which smart pointer do I choose for simple RAII of a class that is copyable and assignable? (I'm thinking that the unique_ptr with delegated copy/assignment operations to the class copy constructor and assignment operator would make a proper choice, but I am not sure) Here's a pseudocode for the problem using raw pointers, it's just a problem description, not a running C++ code: // Operation interface class ModelOperation { public: virtual void operate = (); }; // Implementation of an operation called Special class SpecialModelOperation : public ModelOperation { private: // Private attributes are present here in a real implementation. public: // Implement operation void operate () {}; }; // All operations conform to ModelOperation interface // These are possible operation names: // class MoreSpecialOperation; // class DifferentOperation; // Concrete model with different operations class MyModel { private: ModelOperation* firstOperation_; ModelOperation* secondOperation_; public: MyModel() : firstOperation_(0), secondOperation_(0) { // Forgetting about run-time type definition from input files here. firstOperation_ = new MoreSpecialOperation(); secondOperation_ = new DifferentOperation(); } void operate() { firstOperation_->operate(); secondOperation_->operate(); } ~MyModel() { delete firstOperation_; firstOperation_ = 0; delete secondOperation_; secondOperation_ = 0; } }; int main() { MyModel modelOne; // Some internal scope { // I want modelTwo to have its own set of copied, not referenced // operations, and at the same time I need RAII to work for it, // as soon as it goes out of scope. MyModel modelTwo (modelOne); } return 0; }

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  • Which libraries use the "We Know Where You Live" optimization for std::make_shared?

    - by KnowItAllWannabe
    Over two years ago, Stephan T. Lavavej described a space-saving optimization he implemented in Microsoft's implementation of std::make_shared, and I know from speaking with him that Microsoft has nothing against other library implementations adopting this optimization. If you know for sure whether other libraries (e.g., for Gnu C++, Clang, Intel C++, plus Boost (for boost::make_shared)) have adopted this implementation, please contribute an answer. I don't have ready access to that many make_shared implementations, nor am I wild about digging into the bowels of the ones I have to see if they've implemented the WKWYL optimization, but I'm hoping that SO readers know the answers for some libraries off-hand. I know from looking at the code that as of Boost 1.52, the WKWYL optimization had not been implemented, but Boost is now up to version 1.55. Note that this optimization is different from std::make_shared's ability to avoid a dedicated heap allocation for the reference count used by std::shared_ptr. For a discussion of the difference between WKWYL and that optimication, consult this question.

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  • Returnimng collection of interfaces

    - by apoorv020
    I have created the following interface public interface ISolutionSpace { public boolean isFeasible(); public boolean isSolution(); public Set<ISolutionSpace> generateChildren(); } However, in the implementation of ISolutionSpace in a class called EightQueenSolutionSpace, I am going to return a set of EightQueenSolutionSpace instances, like the following stub: @Override public Set<ISolutionSpace> generateChildren() { return new HashSet<EightQueenSolutionSpace>(); } However this stub wont compile. What changes do I need to make? EDIT: I tried 'HashSet' as well and had tried using the extends keyword. However since 'ISolutionSpace' is an interface and EightQueenSolutionSpace is an implementation(and not a subclass) of 'ISolutionSpace', it is still not working.

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  • iphone memory management: alloc and retain properties.

    - by Jonathan
    According to the docs, you do one release per alloc or retain (etc) However what about when using retain propertys? eg: HEADER @property(retain)UIView *someView; IMPLEMENTATION /*in some method*/ UIView *tempView = [[UIView alloc] init]; //<<<<<ALLOC - retain count = +1 [tempView setBackgroundColor:[UIColor redColor]]; self.someView = tempView; ///<<<<<RETAIN - retain count = +2 [tempView release]; ///should I do this? or a different version of the IMPLEMENTATION self.someView = [[UIView alloc] init]; //<<<<<ALLOC & RETAIN - retain count = +2 //now what??? [self.someView release]; ???? EDIT: I didn't make it clear, but I meant what to do in both circumstances, not just the first.

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  • Allocation Target of std::aligned_storage (stack or heap?)

    - by Zenikoder
    I've been trying to get my head around the TR1 addition known as aligned_storage. Whilst reading the following documents N2165, N3190 and N2140 I can't for the life of me see a statement where it clearly describes stack or heap nature of the memory being used. I've had a look at the implementation provided by msvc2010, boost and gcc they all provide a stack based solution centered around the use of a union. In short: Is the memory type (stack or heap) used by aligned_storage implementation defined or is it always meant to be stack based? and, What the is the specific document that defines/determines that?

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  • Getting started with C++ ( the paradigm shift from Python )

    - by orokusaki
    I want to learn C++ so that i can develop C++ Python modules for server-related stuff. I'm a purely dynamic languages developer (Python, PHP, Ruby, etc). I want to learn a fast language, and if I'm going to do this, I'd rather learn a really fast language like C++. Before I even get started though, I understand that suddenly working with static types, a different syntax, and compiling code will be quite the paradigm shift. Is there any advice that a C++ dev who also has dynamic languages experience can give me to me to help me make that shift faster?

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  • -[CCScene setOffsetx:]: unrecognized selector sent to instance

    - by Alexander Sharunov
    please help me, i'm very new in objective-c i've got 2 simplest classes (bellow first, second) i would like to set the offsetx properties of self.rolypoly object in second class like a self.rolypoly.offsetx=1 or run use [self.rolypoly setOffx]; to do somethings, but i always have the errors: trying [self.rolypoly setOffx]; in second class -[CCScene setOffx:]: unrecognized selector sent to instance 0x91d0b70' or trying self.rolypoly.offsetx=1; in second class -[CCScene setOffsetx:]: unrecognized selector sent to instance 0x808bfc0' first class //************************************************************ #import <Foundation/Foundation.h> #import "cocos2d.h" @interface RolyPoly : CCLayer { CCAction *_walkAction; CCSprite *_rolypoly; int offsetx; int offsety; } @property (nonatomic, retain) CCSprite *rolypoly; @property (nonatomic, retain) CCAction *walkAction; @property (nonatomic, assign) int offsetx; @property (nonatomic, assign) int offsety; +(id) scene; -(void) setOffx; @end //************************************************************ #import "GameLayer.h" #import "RolyPoly.h" @implementation RolyPoly @synthesize rolypoly = _rolypoly; @synthesize walkAction = _walkAction; @synthesize offsetx = _offsetx; @synthesize offsety = _offsety; +(id) scene { CCScene *scene = [CCScene node]; RolyPoly *layer = [RolyPoly node]; [scene addChild: layer]; return scene; } -(id) init { if ((self = [super init])) { [self scheduleUpdate]; } return self; } -(void) setOffx { NSLog(@"setOffx"); } -(void) update:(ccTime)delta { } - (void) dealloc { self.rolypoly = nil; self.walkAction = nil; [super dealloc]; } @end second class //************************************************************ #import <Foundation/Foundation.h> #import "cocos2d.h" #import "RolyPoly.h" @interface GameLayer : CCLayer { RolyPoly *_rolypoly; } // returns a CCScene that contains the HelloWorldLayer as the only child +(CCScene *) scene; @property (nonatomic, assign) RolyPoly * rolypoly; @end //************************************************************ #import "GameLayer.h" #import "RolyPoly.h" // HelloWorldLayer implementation @implementation GameLayer @synthesize rolypoly = _rolypoly; +(CCScene *) scene { CCScene *scene = [CCScene node]; GameLayer *layer = [GameLayer node]; [scene addChild: layer]; return scene; } -(id) init { if( (self=[super init])) { CGSize screenSize = [[CCDirector sharedDirector] winSize]; self.rolypoly = [RolyPoly scene]; [self addChild:self.rolypoly z:1]; [self.rolypoly setOffx]; [self scheduleUpdate]; } return self; } - (void)update:(ccTime)dt { } - (void) dealloc { [super dealloc]; } @end

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  • How to convince a colleague that code duplication is bad?

    - by vitaut
    A colleague of mine was implementing a new feature in a project we work on together and he did it by taking a file containing the implementation of a similar feature from the same project, creating a copy of it renaming all the global declarations and slightly modifying the implementation. So we ended up with two large files that are almost identical apart from renaming. I tried to explain that it makes our project more difficult to maintain but he doesn't want to change anything saying that it is easier for him to program in such way and that there is no reason to fix the code if it "ain't broke". How can I convince him that such code duplication is a bad thing? It is related to this questions, but I am more interested in the answers targeted to a technical person (another programmer), for example a reference to an authoritative source like a book would be great. I have already tried simple arguments and haven't succeeded.

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  • iPhone - Change app icon pointed to by info.plist within the application?

    - by Batgar
    Is there any way to change the 47x47 PNG, pointed to within info.plist, for the iPhone springboard icon from within code? I understand I can add a translation and change the springboard icon per language that the iPhone supports via a changed info.plist per language, but I would like to change the springboard icon for my iPhone app based on a user preference within the app. Any ideas? I haven't tried this, but can a file be copied over another within an app bundle? Could I ship with info.plist pointing to "base.png" then replace "base.png" with another PNG I package with my app from within code? Thanks. --Batgar

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  • C++ - checking if a class has a certain method at compile time

    - by jetwolf
    Here's a question for the C++ gurus out there. Is there a way to check at compile time where a type has a certain method, and do one thing if it does, and another thing if it doesn't? Basically, I have a template function template <typename T> void function(T t); and I it to behave a certain way if T has a method g(), and another way if it doesn't. Perhaps there is something that can be used together with boost's enable_if? Something like this: template <typename T> enable_if<has_method<T, g, void ()>, void>::type function(T t) { // Superior implementation calling t.g() } template <typename T> disable_if<has_method<T, g, void ()>, void>::type function(T t) { // Inferior implementation in the case where T doesn't have a method g() } "has_method" would be something that preferably checks both that T has a method named 'g', and that the method has the correct signature (in this case, void ()). Any ideas?

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  • C++ Singleton design pattern.

    - by Artem Barger
    Recently I've bumped into realization/implementation of Singleton design pattern for C++. It has looked in the following way (I have adopted it from real life example): // a lot of methods is omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that instance field is initiated on the heap, that means there is a memory allocation. That is completely unclear for me is when does exactly memory is going to be deallocated? Or there is a bug and memory leak? It seems like there is a problem in implementation. PS. And main question how to implement it in the right way?

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  • After C++ - Python or Java?

    - by carleeto
    I'm fast approaching the point in my coding where I would like to quickly write object oriented code in languages other than C++ for a variety of reasons. After a lot of research, my choices have pretty much narrowed down to Python and Java. I'm leaning towards Python because of its relationship to C, but with Java, from what I can see, I get a good introduction to using and creating test suites with Eclipse - there is also Processing which is pulling me towards Java. I'm not the kind of guy to tackle two languages at once, so which one would you recommend and why? What I want at the end is to have an additional language I can use for rapid development. Ease of learning isn't important to me as I'm willing to put in the time regardless. Ability to use the new language widely is.

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  • Couldn't I just pass an copied string to an Core Data property?

    - by dontWatchMyProfile
    The docs say: The default implementation does not copy attribute values. If the attribute value may be mutable and implements the NSCopying protocol (as is the case with NSString, for example), you can copy the value in a custom accessor to help preserve encapsulation (for example, in the case where an instance of NSMutableString is passed as a value). So instead of getting into trouble and inconvenience with overwriting accessors in my NSManagedObject subclass, couldn't I simply do something like this? myManagedObject.firstName = [[firstNameMutableStr copy] autorelease]; This would have the exact same effect, or not? The dynamic implementation would retain that anyways ... so.... why not the easy way?

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  • I want to use Google Map API for my Desktop application

    - by Nubkadiya
    i want to use google map api for my desktop application. the application will be totally connected to internet. while i was searching some research notes about this implementation. i found a ideal site with the configurations. but it has some java files to be downloaded. but when i tried that website its not loading. which is swinglabs.org http://today.java.net/pub/a/today/2007/10/30/building-maps-into-swing-app-with-jxmapviewer.html any other options of doing this api implementation to my desktop application. and one more thing. i tried downloading the google api. even it ask a url. we have to provide a url then only we get a key to download it. and the api should run in that specific url. otherwise its not working. how this appears to a desktop application any ideas welcome..

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  • C# - Why can't I enforce derived classes to have parameterless constructors?

    - by FrisbeeBen
    I am trying to do the following: public class foo<T> where T : bar, new { _t = new T(); private T _t; } public abstract class bar { public abstract void someMethod(); // Some implementation } public class baz : bar { public overide someMethod(){//Implementation} } And I am attempting to use it as follows: foo<baz> fooObject = new foo<baz>(); And I get an error explaining that 'T' must be a non-abstract type with a public parameterless constructor in order to use it as parameter 'T' in the generic type or method. I fully understand why this must be, and also understand that I could pass a pre-initialized object of type 'T' in as a constructor argument to avoid having to 'new' it, but is there any way around this? any way to enforce classes that derive from 'bar' to supply parameterless constructors?

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  • How to use the variable declared in one class in another class in Obj C.

    - by srikanth rongali
    I have a NSDate *date1 in class1 implementation file(I initialized it as Global variable). I have NSDate *date2 in class 2 implementation file (initialized it as Global variable). I need to calculate the NSTimeInterval between the two dates in class 2. But I could not do it. I could not access date1 in this class. It is giving error as (date2 undeclared). Please give me help in how to call other class variables in this class. Thank you.

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  • Free PHP framework/library for single-sign on / cross domain login

    - by Dennis Cheung
    I am looking for free (non GPL is better) SSO framework/library implementation or code samples. There are many kind of SSO implementation. Sharing cookie, sharing session, one time token, associative accounts, etc, etc. (BTW, any good article compare them?) Is there any keyword I should google and reuse before before I start to implement our own wheel. I know OpenID, but which is too much and it is not our need. We rather keep it KISS. We just want share the credentials of user that could save users from another login form.

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  • Inspiration and influence of the else clause of loop statements?

    - by Aristide
    Python offers an optional loop-else clause which is executed if and only if the loop is not terminated by a break. (In other words, the condition fails for a while-loop or the iterator is exhausted for a for-loop.) Does this loop-else construct originate from another language? (Either theoretical or actually implemented.) Has it been taken up in any newer language? Maybe I should ask the former of Guido, but surely he is too busy for such a futile inquiry. ;-) Related discussion and examples: Pythonic ways to use ‘else’ in a for loop

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  • Objective C instance variables - Newbie

    - by Dwayne King
    OK - so I'm sure my confusion here is just a result of being stuck in a "Java mindset" and not understanding how Obj C differs in this case. In Java, I can declare a variable in a class, like this, and each instance of that class will have it's own: MyClass { String myVar; MyClass() { // constructor } } In Obj C I tried to do the same thing by declaring a variable only in the .m file like this: #import "MyClass.h" @implementation MyClass NSString *testVar; @end My expectation here was that this variable has a scope limited to this class. So I created a second class (identical): #import "MySecondClass.h" @implementation MySecondClass NSString *testVar; @end What I'm seeing (and has me baffled) is that changing the variable in one class, affects the value seen in the other class. In fact, if I set a breakpoint, and then "Jump to Definition" of the variable, it takes me to th I've created an extremely small XCode project that demonstrates the problem here Nothing more humbling than moving to a new language :) Thanks in advance.

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  • Ternary operators and variable reassignment in PHP

    - by TomcatExodus
    I've perused the questions on ternary operators vs. if/else structures, and while I understand that under normal circumstances there is no performance loss/gain in using ternary operators over if/else structures, I've not seen any mention of this situation. Language specific to PHP (but any language agnostic details are welcome) does the interpreter reassign values in situations like this: $foo = 'bar' $foo = strlen($foo) > 3 ? substr($foo, 0, 3) : $foo; Since this would evaluate to $foo = $foo; is this inefficient, or does the interpreter simply overlook/discard this evaluation? On a side note, what about: !defined('SECURE') ? exit : null;

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  • Flex 3 - Full unicode support fonts and CSS

    - by BS_C3
    Hi! I'm developping a web application that will be used either in Europe or in Asia (specially Japan -Hiragana, Kanji and Katana-, China and Korea). I'm using the following fonts: - ericssonga628.TTF - HelveticaNeueLTStd-Lt.otf - HelveticaNeueLTStd-LtEx.otf - HelveticaNeueLTStd-Bd.otf - HelveticaNeueLTStd-BdEx.otf When I tried to display Japanese characters, I don't get anything. I guess these fonts don't support East Asian characters... Do you know of any equivalent fonts? Also, I was thinking of creating a CSS for each language (or pack of languages) when the user changes the display language. For example, if the user selects "japanese", I'll use the japanese stylesheet. However, how do I switch from a CSS to another? Thanks in advance for your answers. Regards,

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