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  • qooxdoo 4.0 : le framework JavaScript adopte les Pointers Events, l'équipe unifie les périphériques

    qooxdoo 4.0 : le framework JavaScript adopte les Pointers Events L'équipe unifie les périphériques (Desktop, Mobile et Site Web)qooxdoo est un framework JavaScript basé sur le système de classes. Il est open source et permet le développement d'applications Web dites « riches » (RIA). La principale nouveauté de la version 4.0 concerne les outils GUI des trois types de plate-formes (site Web, mobile et desktop).Événements indépendants du périphérique d'entréeLes applications qooxdoo peuvent désormais...

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  • Any pitfalls using char* instead of void* when writing cross platform code?

    - by UberMongoose
    Is there any pitfalls when using char*'s to write cross platform code that does memory access? I'm working on a play memory allocator to better understand how to debug memmory issues. I have come to believe char*'s are preferable because of the ability to do pointer arithmetic and derefernce them over void*'s, is that true? Do the following assumptions always hold true on different common platforms? sizeof(char) == 1 sizeof(char*) == sizeof(void*) sizeof(char*) == sizeof(size_t)

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  • The best way to have a pointer to several methods - critique requested

    - by user827992
    I'm starting with a short introduction of what i know from the C language: a pointer is a type that stores an adress or a NULL the * operator reads the left value of the variable on its right and use this value as address and reads the value of the variable at that address the & operator generate a pointer to the variable on its right so i was thinking that in C++ the pointers can work this way too, but i was wrong, to generate a pointer to a static method i have to do this: #include <iostream> class Foo{ public: static void dummy(void){ std::cout << "I'm dummy" << std::endl; }; }; int main(){ void (*p)(); p = Foo::dummy; // step 1 p(); p = &(Foo::dummy); // step 2 p(); p = Foo; // step 3 p->dummy(); return(0); } now i have several questions: why step 1 works why step 2 works too, looks like a "pointer to pointer" for p to me, very different from step 1 why step 3 is the only one that doesn't work and is the only one that makes some sort of sense to me, honestly how can i write an array of pointers or a pointer to pointers structure to store methods ( static or non-static from real objects ) what is the best syntax and coding style for generating a pointer to a method?

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  • Explain this C# code: byte* p = (byte*) (void*) Scan0;

    - by qulzam
    I found the code from the net in which i cant understand this line:- byte* p = (byte*)(void*)Scan0; There Scan0 is System.IntPtr. It is code of C#.Net. Plz Explain the above line. The complete code is given below. this is code to convert a image in grayscale. public static Image GrayScale(Bitmap b) { BitmapData bmData = b.LockBits(new Rectangle(0, 0, b.Width, b.Height), ImageLockMode.ReadWrite, PixelFormat.Format24bppRgb); int stride = bmData.Stride; System.IntPtr Scan0 = bmData.Scan0; unsafe { byte* p = (byte*)(void*)Scan0; int nOffset = stride - b.Width * 3; byte red, green, blue; for (int y = 0; y < b.Height; ++y) { for (int x = 0; x < b.Width; ++x) { blue = p[0]; green = p[1]; red = p[2]; p[0] = p[1] = p[2] = (byte)(.299 * red + .587 * green + .114 * blue); p += 3; } p += nOffset; } } b.UnlockBits(bmData); return (Image)b; } I understand all the code but only have the problem on this line. byte* p = (byte*)(void*)Scan0;

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  • how to Clean up(destructor) a dynamic Array of pointers??

    - by Ahmed Sharara
    Is that Destructor is enough or do I have to iterate to delete the new nodes?? #include "stdafx.h" #include<iostream> using namespace std; struct node{ int row; int col; int value; node* next_in_row; node* next_in_col; }; class MultiLinkedListSparseArray { private: char *logfile; node** rowPtr; node** colPtr; // used in constructor node* find_node(node* out); node* ins_node(node* ins,int col); node* in_node(node* ins,node* z); node* get(node* in,int row,int col); bool exist(node* so,int row,int col); //add anything you need public: MultiLinkedListSparseArray(int rows, int cols); ~MultiLinkedListSparseArray(); void setCell(int row, int col, int value); int getCell(int row, int col); void display(); void log(char *s); void dump(); }; MultiLinkedListSparseArray::MultiLinkedListSparseArray(int rows,int cols){ rowPtr=new node* [rows+1]; colPtr=new node* [cols+1]; for(int n=0;n<=rows;n++) rowPtr[n]=NULL; for(int i=0;i<=cols;i++) colPtr[i]=NULL; } MultiLinkedListSparseArray::~MultiLinkedListSparseArray(){ // is that destructor enough?? cout<<"array is deleted"<<endl; delete [] rowPtr; delete [] colPtr; }

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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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  • How to void checked exceptions in Java?

    - by deamon
    I consider checked exception for a design mistake in the Java language. They lead to leaky abstractions and a lot of clutter in the code. It seems that they force the programmer to handle exceptions early although they are in most cases better handled lately. So my question is how to avoid checked exception? My idea is to execute the actual code inside an exception translator using lambda expressions. Example: ExceptionConverter.convertToRuntimeException(() => { // do things that could throw checked exceptions here }); If for example a IOException occurs it gets rethrown as an exception with the same name but from a different class hierarchy (based on RuntimeException). This approach would effectivly remove the need to handle or declare checked exceptions. Exceptions could then be handled where and if it makes sense. Another solution would be to declare IOException throws Exception on each method. What do you think which solution is better? Do you know any better approach to avoid (suppress) checked exceptions in Java?

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  • Function not returning value at all - not a void [migrated]

    - by user105439
    I have this function that is not returning a function value. I've added some random testers to try and debug but no luck. Thanks! #include <stdio.h> #include <math.h> #include <time.h> #define N 100 float error(int a, int b); int main(){ printf("START\n"); srand(time(NULL)); int a, b, j, m; float plot[N+1]; printf("Lower bound for x: "); scanf("%d", &a); printf("Upper bound for x: "); scanf("%d", &b); printf("okay\n"); for(j = 0; j < N; j++) plot[j] = 0; printf("okay1\n"); m = error(a,b); printf("%f\n",m); return 0; } float error(int a, int b){ float product = a*b; printf("%f\n",product); return product; } so the m = error(a,b) always gives 0 no matter what! Please help. I apologise for not cleaning this up...

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  • Array of pointers in C++.

    - by Theorem
    I am not understanding the output of this , #include <iostream> using namespace std; // pointers and arrays char ch1 = 'a' , ch2= 'b'; char ch3[6] = {'c', 'd', 'e', 'f', 'g' , 'h'}; char *ptr[3]; int main () { ptr[0] = &ch1 ; ptr[2] = ch3; cout << &ch1 << endl; } The out put is abcdefgh . isn't &ch1 supposed to give the address of ch1 ? I cannot make sense why the output should be abcdefgh.

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  • Another void C# question

    - by Jim Jones
    Have a type in the header files I'm working with called VTVOID it is the type of a struct element and a number of parameters. In the header file defining types is the line #define VTVOID void I read in another discussion the void maps to System.Void however when I plug that into the C# code I get the error "System.Void cannot be used in C# -- use typeof(void) to get the void object." So what type do I plug in? Jim

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  • IPHONE SDK, How to put Void function into my BOOL??? PLEASE!

    - by Harry
    I am using the IPhone's Accelerometer to make a object move. I want to be able to make this function work and not work depending on different states. I have my code for my Accelerometer function and i want to put it into a BOOL so i can call on it when i need it, but i am having problems. Can anyone Help me put this code into a BOOL named: -(BOOL) accelerometerWorks -(void) accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration{ valueX = acceleration.x*25.5; int newX = (int)(ball.center.x +valueX); if (newX > 320-BALL_RADIUS) newX = 320-BALL_RADIUS; if (newX < 0+BALL_RADIUS) newX = 0+BALL_RADIUS; int XA = (int)(balloonbit1.center.x +valueX); if (XA > 320-BALL_RADIUS) XA = 320-BALL_RADIUS; if (XA < 0+BALL_RADIUS) XA = 0+BALL_RADIUS; int XB = (int)(balloonbit2.center.x +valueX); if (XB > 320-BALL_RADIUS) XB = 320-BALL_RADIUS; if (XB < 0+BALL_RADIUS) XB = 0+BALL_RADIUS; int XE = (int)(balloonbit5.center.x +valueX); if (XE > 320-BALL_RADIUS) XE = 320-BALL_RADIUS; if (XE < 0+BALL_RADIUS) XE = 0+BALL_RADIUS; int XF = (int)(balloonbit6.center.x +valueX); if (XF > 320-BALL_RADIUS) XF = 320-BALL_RADIUS; if (XF < 0+BALL_RADIUS) XF = 0+BALL_RADIUS; int XH = (int)(balloonbit8.center.x +valueX); if (XH > 320-BALL_RADIUS) XH = 320-BALL_RADIUS; if (XH < 0+BALL_RADIUS) XH = 0+BALL_RADIUS; ball.center = CGPointMake (newX, 415); balloonbit1.center = CGPointMake (XA, 408); balloonbit2.center = CGPointMake (XB, 395); balloonbit5.center = CGPointMake (XE, 388); balloonbit6.center = CGPointMake (XF, 413); balloonbit8.center = CGPointMake (XH, 426); } Please help. i have been trying for ages with no success. Thanks. Harry.

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  • How can pointers to functions point to something that doesn't exist in memory yet? Why do prototypes have different addresses?

    - by Kacy Raye
    To my knowledge, functions do not get added to the stack until run-time after they are called in the main function. So how can a pointer to a function have a function's memory address if it doesn't exist in memory? For example: using namespace std; #include <iostream> void func() { } int main() { void (*ptr)() = func; cout << reinterpret_cast<void*>(ptr) << endl; //prints 0x8048644 even though func never gets added to the stack } Also, this next question is a little less important to me, so if you only know the answer to my first question, then that is fine. But anyway, why does the value of the pointer ( the memory address of the function ) differ when I declare a function prototype and implement the function after main? In the first example, it printed out 0x8048644 no matter how many times I ran the program. In the next example, it printed out 0x8048680 no matter how many times I ran the program. For example: using namespace std; #include <iostream> void func(); int main() { void ( *ptr )() = func; cout << reinterpret_cast<void*>(ptr) << endl; } void func(){ }

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  • null pointers vs. Null Object Pattern

    - by GlenH7
    Attribution: This grew out of a related P.SE question My background is in C / C++, but I have worked a fair amount in Java and am currently coding C#. Because of my C background, checking passed and returned pointers is second-hand, but I acknowledge it biases my point of view. I recently saw mention of the Null Object Pattern where the idea is than an object is always returned. Normal case returns the expected, populated object and the error case returns empty object instead of a null pointer. The premise being that the calling function will always have some sort of object to access and therefore avoid null access memory violations. So what are the pros / cons of a null check versus using the Null Object Pattern? I can see cleaner calling code with the NOP, but I can also see where it would create hidden failures that don't otherwise get raised. I would rather have my application fail hard (aka an exception) while I'm developing it than have a silent mistake escape into the wild. Can't the Null Object Pattern have similar problems as not performing a null check? Many of the objects I have worked with hold objects or containers of their own. It seems like I would have to have a special case to guarantee all of the main object's containers had empty objects of their own. Seems like this could get ugly with multiple layers of nesting.

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  • Pointers inside a structure [on hold]

    - by user3402552
    I have the next program: #include<stdio.h> #include<stdlib.h> struct a { char *ch; char *str; }; int main() { struct a s1; char ptr[100]; int m, n; printf("\n Enter a string : "); gets(ptr); m = strlen(ptr); s1.ch = (char *)malloc(strlen(ptr) * sizeof(char)); if(s1.ch) { strcpy(s1.ch, ptr); } else { printf("\n Alocation failed!\n"); } printf("\n %s\n\n", s1.ch); while(*s1.ch) { printf(" %c", *(s1.ch)); s1.ch++; } printf("\n\n"); s1.ch = s1.ch - m; printf("\n\n\n %s \n\n", s1.ch); } Is this ok this program in this way ? I mean the pointers should not be initialized ? And if it is not ok, why compile it without errors?

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  • Shared pointers causing weird behaviour

    - by Setzer22
    I have the following code in SFML 2.1 Class ResourceManager: shared_ptr<Sprite> ResourceManager::getSprite(string name) { shared_ptr<Texture> texture(new Texture); if(!texture->loadFromFile(resPath+spritesPath+name)) throw new NotSuchFileException(); shared_ptr<Sprite> sprite(new Sprite(*texture)); return sprite; } Main method: (I'll omit most of the irrelevant code shared_ptr<Sprite> sprite = ResourceManager::getSprite("sprite.png"); ... while(renderWindow.isOpen()) renderWindow.draw(*sprite); Oddly enough this makes my sprite render completely white, but if I do this instead: shared_ptr<Sprite> ResourceManager::getSprite(string name) { Texture* texture = new Texture; // <------- From shared pointer to pointer if(!texture->loadFromFile(resPath+spritesPath+name)) throw new NotSuchFileException(); shared_ptr<Sprite> sprite(new Sprite(*texture)); return sprite; } It works perfectly. So what's happening here? I assumed the shared pointer would work just as a pointer. Could it be that it's getting deleted? My main method is keeping a reference to it so I don't really understand what's going on here :S EDIT: I'm perfectly aware deleting the sprite won't delete the texture and this is generating a memory leak I'd have to handle, that's why I'm trying to use smart pointers on the first place...

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  • Did anyone give these smart pointers (auto_any, scoped_any, shared_any) a test drive?

    - by Johann Gerell
    I'm investigating smart pointers with "shared" functionality for Windows CE and Mobile, where the VS 2008 tr1 std::shared_ptr cannot be used (due to linkage to a v.9 dll not present on CE, obviously, if I understand it correctly). There's a semi-old MSDN Magazine article with sources from a Microsoftie (Eric Niebler): Achieve More Reliable Resource Management with Our Custom C++ Classes. The reasoning, design and implementation of his shared_any looks solid, but I'm wondering if anyone ever actually tested the lot on any platform (not necessarily WinCe/WM)?

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  • Cast from Void* to TYPE* using C++ style cast: static_cast or reinterpret_cast

    - by David Relihan
    So if your converting from Void* to Type* or from Type* to Void* should you use: void func(void *p) { Params *params = static_cast<Params*>(p); } or void func(void *p) { Params *params = reinterpret_cast<Params*>(p); } To me static_cast seems the more correct but I've seen both used for the same purpose. Also, does the direction of the conversion matter. i.e. should I still use static_cast for: _beginthread(func,0,static_cast<void*>(params) I have read the other questions on C++ style casting but I'm still not sure what the correct way is for this scenario (I think it is static_cast)

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  • How to declare a 2D array of 2D array pointers and access them?

    - by vikramtheone
    Hi Guys, How can I declare an 2D array of 2D Pointers? And later access the individual array elements of the 2D arrays. Is my approach correct? void alloc_2D(int ***memory, unsigned int rows, unsigned int cols); int main() { int i, j; int **ptr; int **array[10][10]; for(i=0;i<10;i++) { for(j=0;j<10;j++) { alloc_2D(&ptr, 10, 10); array[i][j] = ptr; } } //After I do this, how can I access the 10 individual 2D arrays? return 0; } void alloc_2D(int ***memory, unsigned int rows, unsigned int cols) { int **ptr; *memory = NULL; ptr = malloc(rows * sizeof(int*)); if(ptr == NULL) { printf("\nERROR: Memory allocation failed!"); } else { int i; for(i = 0; i< rows; i++) { ptr[i] = malloc(cols * sizeof(float)); if(ptr[i]==NULL) { printf("\nERROR: Memory allocation failed!"); } } } *memory = ptr; }

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  • What is the point of dynamic allocation in C++?

    - by Aerovistae
    I really have never understood it at all. I can do it, but I just don't get why I would want to. For instance, I was programming a game yesterday, and I set up an array of pointers to dynamically allocated little enemies in the game, then passed it to a function which updates their positions. When I ran the game, I got one of those nondescript assertion errors, something about a memory block not existing, I don't know. It was a run-time error, so it didn't say where the problem was. So I just said screw it and rewrote it with static instantiation, i.e.: while(n<4) { Enemy tempEnemy = Enemy(3, 4); enemyVector.push_back(tempEnemy); n++; } updatePositions(&enemyVector); And it immediately worked perfectly. Now sure, some of you may be thinking something to the effect of "Maybe if you knew what you were doing," or perhaps "n00b can't use pointers L0L," but frankly, you really can't deny that they make things way overcomplicated, hence most modern languages have done away with them entirely. But please-- someone -- What IS the point of dynamic allocation? What advantage does it afford? Why would I ever not do what I just did in the above example?

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  • C++ vector of strings, pointers to functions, and the resulting frustration.

    - by Kyle
    So I am a first year computer science student, for on of my final projects, I need to write a program that takes a vector of strings, and applies various functions to these. Unfortunately, I am really confused on how to use pointer to pass the vector from function to function. Below is some sample code to give an idea of what I am talking about. I also get an error message when I try to deference any pointer. thanks. #include <iostream> #include <cstdlib> #include <vector> #include <string> using namespace std; vector<string>::pointer function_1(vector<string>::pointer ptr); void function_2(vector<string>::pointer ptr); int main() { vector<string>::pointer ptr; vector<string> svector; ptr = &svector[0]; function_1(ptr); function_2(ptr); } vector<string>::pointer function_1(vector<string>::pointer ptr) { string line; for(int i = 0; i < 10; i++) { cout << "enter some input ! \n"; // i need to be able to pass a reference of the vector getline(cin, line); // through various functions, and have the results *ptr.pushback(line); // reflectedin main(). But I cannot use member functions } // of vector with a deferenced pointer. return(ptr); } void function_2(vector<string>::pointer ptr) { for(int i = 0; i < 10; i++) { cout << *ptr[i] << endl; } }

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  • Why does std::cout convert volatile pointers to bool?

    - by Joseph Garvin
    If you try to cout a volatile pointer, even a volatile char pointer where you would normally expect cout to print the string, you will instead simply get '1' (assuming the pointer is not null I think). I assume output stream operator<< is template specialized for volatile pointers, but my question is, why? What use case motivates this behavior? Example code: #include <iostream> #include <cstring> int main() { char x[500]; std::strcpy(x, "Hello world"); int y; int *z = &y; std::cout << x << std::endl; std::cout << (char volatile*)x << std::endl; std::cout << z << std::endl; std::cout << (int volatile*)z << std::endl; return 0; } Output: Hello world 1 0x8046b6c 1

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  • How to declare array of 2D array pointers and access them?

    - by vikramtheone
    Hi Guys, How can I declare an 2D array of 2D Pointers? And later access the individual array elements of the 2D arrays. Is my approach correct? main() { int i, j; int **array[10][10]; int **ptr = NULL; for(i=0;i<10;i++) { for(j=0j<10;j++) { alloc_2D(&ptr, 10, 10); array[i][j] = ptr; } } //After I do this, how can I access the individual 2D array //and then the individual elements of the 2D arrays? } void alloc_2D(float ***memory, unsigned int rows, unsigned int cols) { float **ptr; *memory = NULL; ptr = malloc(rows * sizeof(float*)); if(ptr == NULL) { status = ERROR; printf("\nERROR: Memory allocation failed!"); } else { int i; for(i = 0; i< rows; i++) { ptr[i] = malloc(cols * sizeof(float)); if(ptr[i]==NULL) { status = ERROR; printf("\nERROR: Memory allocation failed!"); } } } *memory = ptr; }

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