Search Results

Search found 3255 results on 131 pages for 'pointers'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 10/131 | < Previous Page | 6 7 8 9 10 11 12 13 14 15 16 17  | Next Page >

  • Storing pointers in multi-dimensional array

    - by sdfqwerqaz1
    My intention is to create a dynamic 3D array in C++ using pointers. MyType*** myArray; myArray = new MyType**[GRID_SIZE]; for (int i = 0; i < GRID_SIZE; ++i) { myArray[i] = new MyType*[GRID_SIZE]; for (int j = 0; j < GRID_SIZE; ++j) { myArray[i][j] = new MyType[GRID_SIZE]; } } Now this 3D array is ready to store MyType instances. What is the correct syntax needed when declaring this array if I want to store pointers to MyType instead of just MyType objects in this array?

    Read the article

  • "Address of" (&) an array / address of being ignored be gcc?

    - by dbarbosa
    Hi, I am a teaching assistant of a introductory programming course, and some students made this type of error: char name[20]; scanf("%s",&name); which is not surprising as they are learning... What is surprising is that, besides gcc warning, the code works (at least this part). I have been trying to understand and I wrote the following code: void foo(int *str1, int *str2) { if (str1 == str2) printf("Both pointers are the same\n"); else printf("They are not the same\n"); } int main() { int test[50]; foo(&test, test); if (&test == test) printf("Both pointers are the same\n"); else printf("They are not the same\n"); } Compiling and executing: $ gcc test.c -g test.c: In function ‘main’: test.c:12: warning: passing argument 1 of ‘foo’ from incompatible pointer type test.c:13: warning: comparison of distinct pointer types lacks a cast $ ./a.out Both pointers are the same Both pointers are the same Can anyone explain why they are not different? I suspect it is because I cannot get the address of an array (as I cannot have & &x), but in this case the code should not compile.

    Read the article

  • WebKit and npapi and mingw-w64

    - by rubenvb
    Hi, The problem is the following: On Windows x64, pointers are 64-bit, but type long is 32-bit. MSVC doesn't seem to care, and even omits warnings about pointer truncation on the default warning level. Since recently, there is a GCC that target x86_64-w64-mingw32, or better Windows x64 native. GCC produces errors when pointers are truncated (which is the logical thing to do...), and this is causing trouble in WebKit and more specifically, the Netscape Plugin API: First, there's the files (I can only post one hyperlink...): http://trac.webkit.org/browser/trunk/WebCore/ bridge/npapi.h -- defines uint32 as 32-bit int type (~line 145) plugins/win/PluginViewWin.cpp -- casts Windows window handles to 32-bit int, truncating them (~line 450) My proposed fix was to change the uint32 casts to uintptr_t, which makes GCC happy, but still puts a 64-bit value in a uint32 (=unsigned long). I have no clue how to solve this, because clearly WebKit is happy truncating pointers on Win64... How can I solve this the right way? Thanks!

    Read the article

  • Alternative to c++ static virtual methods

    - by Jaime Pardos
    In C++ is not possible to declare a static virtual function, neither cast a non-static function to a C style function pointer. Now, I have a plain ol' C SDK that uses function pointers heavily. I have to fill a structure with several function pointers. I was planning to use an abstract class with a bunch of static pure virtual methods, and redefine them in derived classes and fill the structure with them. It wasn't until then that I realized that static virtual are not allowed in C++. Is there any good alternative? The best I can think of is defining some pure virtual methods GetFuncA(), GetFuncB(),... and some static members FuncA()/FuncB() in each derived class, which would be returned by the GetFuncX(). Then a function in the abstract class would call those functions to get the pointers and fill the structure.

    Read the article

  • qsort on an array of pointers to Objective-C objects

    - by ElBueno
    I have an array of pointers to Objective-C objects. These objects have a sort key associated with them. I'm trying to use qsort to sort the array of pointers to these objects. However, the first time my comparator is called, the first argument points to the first element in my array, but the second argument points to garbage, giving me an EXC_BAD_ACCESS when I try to access its sort key. Here is my code (paraphrased): - (void)foo:(int)numThingies { Thingie **array; array = malloc(sizeof(deck[0])*numThingies); for(int i = 0; i < numThingies; i++) { array[i] = [[Thingie alloc] initWithSortKey:(float)random()/RAND_MAX]; } qsort(array[0], numThingies, sizeof(array[0]), thingieCmp); } int thingieCmp(const void *a, const void *b) { const Thingie *ia = (const Thingie *)a; const Thingie *ib = (const Thingie *)b; if (ia.sortKey > ib.sortKey) return 1; //ib point to garbage, so ib.sortKey produces the EXC_BAD_ACCESS else return -1; } Any ideas why this is happening?

    Read the article

  • [Ruby] Object assignment and pointers

    - by Jergason
    I am a little confused about object assignment and pointers in Ruby, and coded up this snippet to test my assumptions. class Foo attr_accessor :one, :two def initialize(one, two) @one = one @two = two end end bar = Foo.new(1, 2) beans = bar puts bar puts beans beans.one = 2 puts bar puts beans puts beans.one puts bar.one I had assumed that when I assigned bar to beans, it would create a copy of the object, and modifying one would not affect the other. Alas, the output shows otherwise. ^_^[jergason:~]$ ruby test.rb #<Foo:0x100155c60> #<Foo:0x100155c60> #<Foo:0x100155c60> #<Foo:0x100155c60> 2 2 I believe that the numbers have something to do with the address of the object, and they are the same for both beans and bar, and when I modify beans, bar gets changed as well, which is not what I had expected. It appears that I am only creating a pointer to the object, not a copy of it. What do I need to do to copy the object on assignment, instead of creating a pointer? Tests with the Array class shows some strange behavior as well. foo = [0, 1, 2, 3, 4, 5] baz = foo puts "foo is #{foo}" puts "baz is #{baz}" foo.pop puts "foo is #{foo}" puts "baz is #{baz}" foo += ["a hill of beans is a wonderful thing"] puts "foo is #{foo}" puts "baz is #{baz}" This produces the following wonky output: foo is 012345 baz is 012345 foo is 01234 baz is 01234 foo is 01234a hill of beans is a wonderful thing baz is 01234 This blows my mind. Calling pop on foo affects baz as well, so it isn't a copy, but concatenating something onto foo only affects foo, and not baz. So when am I dealing with the original object, and when am I dealing with a copy? In my own classes, how can I make sure that assignment copies, and doesn't make pointers? Help this confused guy out.

    Read the article

  • Confusion about pointers and their memory addresses

    - by TimothyTech
    alright, im looking at a code here and the idea is difficult to understand. #include <iostream> using namespace std; class Point { public : int X,Y; Point() : X(0), Y(0) {} }; void MoveUp (Point * p) { p -> Y += 5; } int main() { Point point MoveUp(&point) cout <<point.X << point.Y; return 0; } Alright, so i believe that a class is created and X and Y are declared and they are put inside a constructor a method is created and the argument is Point * p, which means that we are going to stick the constructor's pointer inside the function; now we create an object called point then call our method and put the pointers address inside it? isnt the pointers address just a memory number like 0x255255? and why wasnt p ever declared? (int * p = Y) what is a memory addres exactly? that it can be used as an argument?

    Read the article

  • Sorting a Singly Linked List With Pointers

    - by Mark Simson
    I am trying to sort a singly linked list using bubble sort by manipulating ONLY the pointers, no keys. The following gets stuck in the for loop and loops infinitely. I don't understand why this is. Can anybody explain to me why the end of the list is not being found? Node* sort_list(Node* head) { Node * temp; Node * curr; for(bool didSwap = true; didSwap; ) { didSwap = false; for(curr = head; curr->next != NULL; curr = curr->next) { if(curr->key > curr->next->key) { temp = curr; curr = curr->next; curr->next = temp; didSwap = true; } cout << curr->next->key << endl; } } return head; } If I change the code so that the keys (data) are swapped, then the function works properly but for some reason I am not able make it work by manipulating only pointers.

    Read the article

  • Pointer-Safe Objects?

    - by cam
    Would it be smart to have a vector in an object with a list of pointers that point to it? This way when the object is deleted, it could delete all the pointers pointing to it to prevent a null-pointer exception?

    Read the article

  • boost smart pointers and BOOST_NO_MEMBER_TEMPLATES

    - by Johann Gerell
    After some struggling I managed to get boost smart pointers to build for Windows CE/Mobile at warning level 4. I found the least-resistance-way to get rid of compile errors and warnings to be #define BOOST_NO_MEMBER_TEMPLATES What does it actually mean? Did I sell my soul to the devil? Will all hell break loose when I actually use the types?

    Read the article

  • Using pointers, references, handles to generic datatypes, as generic and flexible as possible

    - by Patrick
    In my application I have lots of different data types, e.g. Car, Bicycle, Person, ... (they're actually other data types, but this is just for the example). Since I also have quite some 'generic' code in my application, and the application was originally written in C, pointers to Car, Bicycle, Person, ... are often passed as void-pointers to these generic modules, together with an identification of the type, like this: Car myCar; ShowNiceDialog ((void *)&myCar, DATATYPE_CAR); The 'ShowNiceDialog' method now uses meta-information (functions that map DATATYPE_CAR to interfaces to get the actual data out of Car) to get information of the car, based on the given data type. That way, the generic logic only has to be written once, and not every time again for every new data type. Of course, in C++ you could make this much easier by using a common root class, like this class RootClass { public: string getName() const = 0; }; class Car : public RootClass { ... }; void ShowNiceDialog (RootClass *root); The problem is that in some cases, we don't want to store the data type in a class, but in a totally different format to save memory. In some cases we have hundreds of millions of instances that we need to manage in the application, and we don't want to make a full class for every instance. Suppose we have a data type with 2 characteristics: A quantity (double, 8 bytes) A boolean (1 byte) Although we only need 9 bytes to store this information, putting it in a class means that we need at least 16 bytes (because of the padding), and with the v-pointer we possibly even need 24 bytes. For hundreds of millions of instances, every byte counts (I have a 64-bit variant of the application and in some cases it needs 6 GB of memory). The void-pointer approach has the advantage that we can almost encode anything in a void-pointer and decide how to use it if we want information from it (use it as a real pointer, as an index, ...), but at the cost of type-safety. Templated solutions don't help since the generic logic forms quite a big part of the application, and we don't want to templatize all this. Additionally, the data model can be extended at run time, which also means that templates won't help. Are there better (and type-safer) ways to handle this than a void-pointer? Any references to frameworks, whitepapers, research material regarding this?

    Read the article

  • lock-free memory reclamation with 64bit pointers

    - by JDonner
    Herlihy and Shavit's book (The Art of Multiprocessor Programming) solution to memory reclamation uses Java's AtomicStampedReference<T>;. To write one in C++ for the x86_64 I imagine requires at least a 12 byte swap operation - 8 for a 64bit pointer and 4 for the int. Is there x86 hardware support for this and if not, any pointers on how to do wait-free memory reclamation without it?

    Read the article

  • Overloading + to add two pointers

    - by iAdam
    I have a String class and I want to overload + to add two String* pointers. something like this doesn't work: String* operator+(String* s1, String* s2); Is there any way to avoid passing by reference. Consider this example: String* s1 = new String("Hello"); String* s2 = new String("World"); String* s3 = s1 + s2; I need this kind of addition to work. Please suggest.

    Read the article

  • pointers in haskell???

    - by curioComp
    hi, do you know if are there pointers in haskell? -If yes, how do you use them? Are there any problems with them? And why aren't they popular? -If no, is there any reason for it? Please help us!! :) Thank you so much!!

    Read the article

  • Direct invocation vs indirect invocation in C

    - by Mohit Deshpande
    I am new to C and I was reading about how pointers "point" to the address of another variable. So I have tried indirect invocation and direct invocation and received the same results (as any C/C++ developer could have predicted). This is what I did: int cost; int *cost_ptr; int main() { cost_ptr = &cost; //assign pointer to cost cost = 100; //intialize cost with a value printf("\nDirect Access: %d", cost); cost = 0; //reset the value *cost_ptr = 100; printf("\nIndirect Access: %d", *cost_ptr); //some code here return 0; //1 } So I am wondering if indirect invocation with pointers has any advantages over direct invocation or vice-versa. Some advantages/disadvantages could include speed, amount of memory consumed performing the operation (most likely the same but I just wanted to put that out there), safeness (like dangling pointers) , good programming practice, etc. 1Funny thing, I am using the GNU C Compiler (gcc) and it still compiles without the return statement and everything is as expected. Maybe because the C++ compiler will automatically insert the return statement if you forget.

    Read the article

  • Serialize struct with pointers to NSData

    - by leolobato
    Hey guys, I need to add some kind of archiving functionality to a Objective-C Trie implementation (NDTrie on github), but I have very little experience with C and it's data structures. struct trieNode { NSUInteger key; NSUInteger count, size; id object; __strong struct trieNode ** children; __strong struct trieNode * parent; }; @interface NDTrie (Private) - (struct trieNode*)root; @end What I need is to create an NSData with the tree structure from that root - or serialize/deserialize the whole tree some other way (conforming to NSCoding?), but I have no clue how to work with NSData and a C struct containing pointers. Performance on deserializing the resulting object would be crucial, as this is an iPhone project and I will need to load it in the background every time the app starts. What would be the best way to achieve this? Thanks!

    Read the article

  • WPF binding and pointers

    - by Eran
    hey guys, I have a WPF application that contains windows with few user controls and Coordinator object. the window and all its user controls pointing to an object, which instace is in the Coordinator, by thier DataContext. the problem is that I want to change this object (e.g. create new object()) in the Coordinator but I want all the dataContexts to point to the new object. I tried to send the object by ref to the window constructor but it didn't help. any idea about how can I rewrite the memory location that all pointers are pointing to? (I don't want to repalce the properties in object since its a lot of work nor to use a middle object that points to the replaced object) Thanks Eran

    Read the article

  • CSS - Could use some pointers on correct positioning

    - by Kenny Bones
    Hi, I'm in need for some pointers on positioning. I've got this square which should be centered on the page. And with a logo and a logo font image kinda wrapped around the square. Now, I want this as dynamic as possible, because I use both the square and images elsewhere as well. So I can't really use stiff static positioning. This is the site: www.matkalenderen.no How should I do this? I want to logo to appear on the left side of the square. And the font to appear above the square. And the square itself should be centered. You probably get the picture :) Right now I've got a wrapper around everything, which is also centered.

    Read the article

  • Casting array of pointers to objects

    - by ritmbo
    If B is subclass of A. And I have in main(): B** b = new B*[10]; ... some algorithm that do b[i] = new B(..); ... So I have an array of pointers to objets B. Then I have a function: void f(A** foo); If in main, I do: f(b); I get a warning, but obviously if I do: f((A**)b);, i dont. The (A**) its a bit nasty. I was wondering if there's a more elegant way in C++ that at least do type checking as dynamic_cast.

    Read the article

  • Only compiles as an array of pointers, not array of arrays

    - by Dustin
    Suppose I define two arrays, each of which have 2 elements (for theoretical purposes): char const *arr1[] = { "i", "j" }; char const *arr2[] = { "m", "n" }; Is there a way to define a multidimensional array that contains these two arrays as elements? I was thinking of something like the following, but my compiler displays warnings about incompatible types: char const *combine[][2] = { arr1, arr2 }; The only way it would compile was to make the compiler treat the arrays as pointers: char const *const *combine[] = { arr1, arr2 }; Is that really the only way to do it or can I preserve the type somehow (in C++, the runtime type information would know it is an array) and treat combine as a multidimensional array? I realise it works because an array name is a const pointer, but I'm just wondering if there is a way to do what I'm asking in standard C/C++ rather than relying on compiler extensions. Perhaps I've gotten a bit too used to Python's lists where I could just throw anything in them...

    Read the article

  • Quick question about pointers

    - by xbonez
    So, I have this code fragment: int * iPtr ; int * jPtr ; int i = 5, k = 7; iPtr = &i; jPtr = iPtr ; I have just started learning about pointers, and need to get some doubts cleared. is jPtr now essentially also pointing at i? I know I can change the value of i by using *iPtr, but how can I change the value of the object being pointed to by jPtr? How will changing the object being pointed to by jPtr affect the value of the object pointed to by iPtr, and i ?

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 6 7 8 9 10 11 12 13 14 15 16 17  | Next Page >