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

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  • C++ compilation error when passing a function into remove_if

    - by garsh0p
    So here's a snippet of my code. void RoutingProtocolImpl::removeAllInfinity() { dv.erase(std::remove_if(dv.begin(), dv.end(), hasInfCost), dv.end()); } bool RoutingProtocolImpl::hasInfCost(RoutingProtocolImpl::dv_entry *entry) { if (entry-link_cost == INFINITY_COST) { free(entry); return true; } else { return false; } } I'm getting the following error when compiling: RoutingProtocolImpl.cc:368: error: argument of type bool (RoutingProtocolImpl::)(RoutingProtocolImpl::dv_entry*)' does not matchbool (RoutingProtocolImpl::*)(RoutingProtocolImpl::dv_entry*)' Sorry, I'm kind of a C++ newb.

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  • C++ multidimensional dynamic array

    - by dmessf
    Let's say I have this to create a multidimensional array dynamically: int* *grid = new int*[gridSizeX]; for (int i=0; i<gridSizeX; i++) { grid[i] = new int[gridSizeY]; } Shouldn't be possible now to access elements like grid[x][y] = 20?

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  • Storing Object Types in Variable then Initializing

    - by Jon Mattingly
    Is there a way in Objective-C to store an object/class in a variable to be passed to alloc/init somewhere else? For example: UIViewController = foo foo *bar = [[foo alloc] init] I'm trying to create a system to dynamically create navigation buttons in a separate class based on the current view controller. I can pass 'self' to the method, but the variable that results does not allow me to alloc/init. I could always import the .h file directly, but ideally I would like to make reusing the code as simple as possible. Maybe I'm going about this the wrong way?

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  • Dynamic allocated array is not freed

    - by Stefano
    I'm using the code above to dynamically allocate an array, do some work inside the function, return an element of the array and free the memory outside of the function. But when I try to deallocate the array it doesn't free the memory and I have a memory leak. The debugger pointed to the myArray variable shows me the error CXX0030. Why? struct MYSTRUCT { char *myvariable1; int myvariable2; char *myvariable2; .... }; void MyClass::MyFunction1() { MYSTRUCT *myArray= NULL; MYSTRUCT *myElement = this->MyFunction2(myArray); ... delete [] myArray; } MYSTRUCT* MyClass::MyFunction2(MYSTRUCT *array) { array = (MYSTRUCT*)operator new(bytesLength); ... return array[X]; }

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  • C Structure Pointer Problem

    - by Halo
    I have this struct; #define BUFSIZE 10 struct shared_data { pthread_mutex_t th_mutex_queue; int count; int data_buffer_allocation[BUFSIZE]; int data_buffers[BUFSIZE][100]; }; and I want to allocate one of the data_buffers for a process, for that purpose I execute the following function; int allocate_data_buffer(int pid) { int i; for (i = 0; i < BUFSIZE; i++) { if (sdata_ptr->data_buffer_allocation[i] == NULL) { sdata_ptr->data_buffer_allocation[i] = pid; return i; } } return -1; } but the compiler warns me that I'm comparing pointer to a value. When I put a & in front of sdata_ptr it calms down but I'm not sure if it will work. Isn't what I wrote above supposed to be true?

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  • Alternatives to C++ Reference/Pointer Syntax

    - by Jon Purdy
    What languages other than C and C++ have explicit reference and pointer type qualifiers? People seem to be easily confused by the right-to-left reading order of types, where char*& is "a reference to a pointer to a character", or a "character-pointer reference"; do any languages with explicit references make use of a left-to-right reading order, such as &*char/ref ptr char? I'm working on a little language project, and legibility is one of my key concerns. It seems to me that this is one of those questions to which it's easy for a person but hard for a search engine to provide an answer. Thanks in advance!

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  • Alternates to C++ Reference/Pointer Syntax

    - by Jon Purdy
    What languages other than C and C++ have explicit reference and pointer type qualifiers? People seem to be easily confused by the right-to-left reading order of types, where char*& is "a reference to a pointer to a character", or a "character-pointer reference"; do any languages with explicit references make use of a left-to-right reading order, such as &*char/ref ptr char? I'm working on a little language project, and legibility is one of my key concerns. It seems to me that this is one of those questions to which it's easy for a person but hard for a search engine to provide an answer. Thanks in advance!

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  • How can I assign pointer member with long string?

    - by Nano HE
    Hi, When I did the practice below to erase my pointer member and assign new value to it. (*pMyPointer).member.erase(); (*pMyPointer).member.assign("Hello"); // Successfully Than I tried more... (*pMyPointer).member.erase(); (*pMyPointer).member.assign("Long Multi Lines Format String"); // How to? If the long multi lines string can't quote by double quoter, how to handle it. Thank you.

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  • Pointing class property to another class with vectors

    - by jmclem
    I've got a simple class, and another class that has a property that points to the first class: #include <iostream> #include <vector> using namespace std; class first{ public: int var1; }; class second{ public: first* classvar; }; Then, i've got a void that's supposed to point "classvar" to the intended iteration of the class "first". void fill(vector<second>& sec, vector<first>& fir){ sec[0].classvar = &fir[0]; } Finally the main(). Create and fill a vector of class "first", create "second" vector, and run the fill function. int main(){ vector<first> a(1); a[0].var1 = 1000; vector<second> b(1); fill(b, a); cout << b[0].classvar.var1 << '\n'; system("PAUSE"); return 0; } This gives me the following error: 1>c:\...\main.cpp(29) : error C2228: left of '.var1' must have class/struct/union 1> type is 'first *' And I can't figure out why it reads the "classvar" as the whole vector instead of just the single instance. Should I do this cout << b[0].classvar[0].var1 << '\n'; it reads perfectly. Can anyone figure out the problem? Thanks in advance

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  • Pointer inside a struct / thread

    - by bruno
    Hi! I have this warning "warning: assignment from incompatible pointer type " in this line: data1->transformed_block[l] = &transformed_block[l]; - void print_message_function ( void *ptr ) { dt *data; data = (dt *) ptr; printf("Dentro da thread Numero0: %ld\n", data->L_norm_NewBlock); pthread_exit(0); } typedef struct data_thread { long L_norm_NewBlock; int Bsize_X; int Bsize_Y; int *transformed_block[MAX_LEVEL]; long L_norm_OrigBlock; } dt; void function() { int *transformed_block[MAX_LEVEL]; pthread_t thread1; dt *data1; pthread_attr_t attr; pthread_attr_init(&attr); //Fills structure data1 = (dt *) malloc(sizeof(dt)); data1->transformed_block[l] = &transformed_block[l]; data1->L_norm_NewBlock=0; data1->Bsize_Y = Bsize_Y; data1->Bsize_X = Bsize_X; pthread_create(&thread1, &attr, (void *) &print_message_function, (void *) &data1); } I want to get rid of that warning, and the values i get inside the thread are wrong. For example data1-L_norm_NewBlock=0; in the thread guives me a differente value (not 0 like it should be).

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  • (gcc) Multi-Dim Array or Double Pointer for Warning-free Compile

    - by paul simmons
    Hi, I have a function, which is called sometimes with regular, sometimes dynamic arrays. If I define the function as function_name(int[10][10] a) and send int** as a parameter, I get a warning. Opposite, if I declare function_name(int** a) and send int[][] as a parameter (after casting) I cannot access to array elements inside function. What is the correctest way?

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  • Why does this C++ code result in a segmentation fault?

    - by user69514
    I keep getting a segmentation fault when the readAuthor() method is called. Does anybody know why this happens? I am supposed to use dynamic arrays, I know this would be so easy if I was using static array. #include <iostream> #include <string> #include <cstring> #include <cstdlib> using namespace std; /** declare arrays **/ int* isbnArr = new int[25]; char* authorArr = new char[25]; char* publisherArr = new char[25]; char* titleArr = new char[25]; int* editionArr = new int[25]; int* yearArr = new int[25]; int* pagesArr = new int[25]; float* retailPriceArr = new float[25]; float* discountedPriceArr = new float[25]; int* stockArr = new int[25]; /** function prototypes **/ int readIsbn(); char* readAuthor(); char* readPublisher(); char* readTitle(); int readEdition(); int readYear(); int readPages(); float readMsrp(); float readDiscountedPrice(); int readStockAmount(); void readonebook(int* isbn, char* author, char* title, char* publisher, int* edition, int* year, int* pages, float* msrp, float* discounted, int* inventory); int main() { bool stop = false; //flag when to stop loop int ind = 0; //index for current book while( !stop ){ cout << "Add book: press A: "; cout << "another thing here "; char choice; cin >> choice; if( choice == 'a' || choice == 'A' ){ readonebook(&isbnArr[ind], &authorArr[ind], &titleArr[ind], &publisherArr[ind], &editionArr[ind], &yearArr[ind], &pagesArr[ind], &retailPriceArr[ind], &discountedPriceArr[ind], &stockArr[ind]); test(&authorArr[ind]); ind++; } } return 0; } /** define functions **/ int readIsbn(){ int isbn; cout << "ISBN: "; cin >> isbn; return isbn; } char* readAuthor(){ char* author; cout << "Author: "; cin >> author; return author; } char* readPublisher(){ char* publisher = NULL; cout << "Publisher: "; cin >> publisher; return publisher; } char* readTitle(){ char* title = NULL; cout << "Title: "; cin >> title; return title; } int readEdition(){ int edition; cout << "Edition: "; cin >> edition; return edition; } int readYear(){ int year; cout << "Year: "; cin >> year; return year; } int readPages(){ int pages; cout << "Pages: "; cin >> pages; return pages; } float readMsrp(){ float price; cout << "Retail Price: "; cin >> price; return price; } float readDiscountedPrice(){ float price; cout << "Discounted Price: "; cin >> price; return price; } int readStockAmount(){ int amount; cout << "Stock Amount: "; cin >> amount; return amount; } void readonebook(int* isbn, char* author, char* title, char* publisher, int* edition, int* year, int* pages, float* msrp, float* discounted, int* inventory){ *isbn = readIsbn(); author = readAuthor(); title = readTitle(); publisher = readPublisher(); *edition = readEdition(); *year = readYear(); *pages = readPages(); *msrp = readMsrp(); *discounted = readDiscountedPrice(); *inventory = readStockAmount(); }

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  • Problem with Command Pattern under Visual Studio 2008 (C++)

    - by D.Giunchi
    Dear All, I've a problem with this pattern under c++ on VS 2008. The same code has been tested in gcc (linux, mac and mingw for widnows) and it works. I copy/paste the code here: class MyCommand { public: virtual void execute() = 0; virtual ~MyCommand () {}; }; class MyOperation { public: virtual void DoIt() {}; //I also write it not inline }; class MyOperationDerived : public MyOperation { public: virtual void DoIt() {}; //I also write it not inline }; class MyUndoStackCommand : public MyCommand { public: typedef void(MyOperation::*Action)(); MyUndoStackCommand(MyOperation *rec, Action action); /*virtual*/ void execute(); /*virtual*/ ~MyUndoStackCommand(); private: MyOperation *myReceiver; Action myAction ; }; in cpp: #include "MyUndoStackCommand.h" #include "MyOperation.h" MyUndoStackCommand::~MyUndoStackCommand() { } MyUndoStackCommand::MyUndoStackCommand(myOperation *rec, Action action): myReceiver(rec), myAction(action) { } void MyUndoStackCommand::execute() { ((myReceiver)->*(myAction))(); } use in main.cpp: MyReceiver receiver; MyUndoStackCommand usc(&receiver, &MyOperation::DoIt); usc.execute(); when I debug under visual studio only if I set inside MyUndoStackCommand, directly myAction = &MyOperation::DoIt , it works, otherwise not. Any advice? thank you very much, dan Edit: The following code compiles with g++ - changes by Neil Butterworth flagged as //NB. class MyCommand { public: virtual void execute() = 0; virtual ~MyCommand () {}; }; class MyOperation { public: virtual void DoIt() {}; //I also write it not inline }; class MyOperationDerived : public MyOperation { public: virtual void DoIt() {}; //I also write it not inline }; class MyUndoStackCommand : public MyCommand { public: typedef void(MyOperation::*Action)(); MyUndoStackCommand(MyOperation *rec, Action action); /*virtual*/ void execute(); /*virtual*/ ~MyUndoStackCommand(); private: MyOperation *myReceiver; Action myAction ; }; MyUndoStackCommand::~MyUndoStackCommand() { } MyUndoStackCommand::MyUndoStackCommand(MyOperation *rec, //NB Action action) : myReceiver(rec), myAction(action) { } void MyUndoStackCommand::execute() { ((myReceiver)->*(myAction))(); } int main() { MyOperation receiver; //NB MyUndoStackCommand usc(&receiver, &MyOperation::DoIt); usc.execute(); }

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  • pointer pointer

    - by gcc
    why we using double pointer like char **p; are there any purpose ,if there is please tell me i read some books but none of them tells purpose(s) of pointer to pointer if we can write char *p; and char **p; i think we may write char ***p; or char ****p; am i wrong

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  • How to store a function in a member of class? (Using function as callback)

    - by Dane
    I want to store a function as a class member and call it inside the class? Pretty much like a callback function. My class draw a document but every document must drawn differently. So I want to assign a function (written outside of the class) into one of the members of the class and then call it when I want to draw the document. This function mostly is responsible for transforming objects according to each specific document. Here is my class: class CDocument { public: CDocument(); ~CDocument(); void *TransFunc(); } void Transform() { } int main() CDocument* Doc = new CDocument(); Doc->TransFunc = Transform(); } I know that this is probably simple question, but I couldn't find the answer by googling or searching SO.

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  • Writing a printList method for a Scheme interpreter in C

    - by Rehan Rasool
    I am new to C and working on making an interpreter for Scheme. I am trying to get a suitable printList method to traverse through the structure. The program takes in an input like: (a (b c)) and internally represent it as: [""][ ][ ]--> [""][ ][/] | | ["A"][/][/] [""][ ][ ]--> [""][ ][/] | | ["B"][/][/] ["C"][/][/] Right now, I just want the program to take in the input, make the appropriate cell structure internally and print out the cell structure, thereby getting (a (b c)) at the end. Here is my struct: typedef struct conscell *List; struct conscell { char symbol; struct conscell *first; struct conscell *rest; }; void printList(char token[20]){ List current = S_Expression(token, 0); printf("("); printf("First Value? %c \n", current->first->symbol); printf("Second value? %c \n", current->rest->first->first->symbol); printf("Third value? %c \n", current->rest->first->rest->first->symbol); printf(")"); } In the main method, I get the first token and call: printList(token); I tested the values again for the sublists and I think it is working. However, I will need a method to traverse through the whole structure. Please look at my printList code again. The print calls are what I have to type, to manually get the (a (b c)) list values. So I get this output: First value? a First value? b First value? c It is what I want, but I want a method to do it using a loop, no matter how complex the structure is, also adding brackets where appropriate, so in the end, I should get: (a (b c)) which is the same as the input. Can anyone please help me with this?

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  • NULL pointer dereference in C

    - by user554125
    hey ive got this piece of code. It dereferences a null pointer here. But then there is an and with unsigned int. I really dont understand the whole part. Can someone explain the output.?? struct hi { long a; int b; long c; }; int main() { struct hi ob={3,4,5}; struct hi *ptr=&ob; int num= (unsigned int) & (((struct hi *)0)->b); printf("%d",num); printf("%d",*(int *)((char *)ptr + (unsigned int) & (((struct hi *)0)->b))); } The o/p i get is 44 .But how does it work?

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