One can initialize a dynamically created array in the following way:
unsigned int * vec;
// ... do something to vec
double * a = (double *) malloc(4*sizeof(double));
a = (double[3]){(double[3]){0.0,10.0,20.0}[vec[0]],
[Code] ....
While there is no compilation error for the first assignment, the memory a is pointing to seems to change, surprisingly to me. This seems to solve the problem though:
memcpy(a, (double[3]){(double[3]){0.0,10.0,20.0}[vec[0]],
(double[3]){1.0,2.0,3.0}[vec[1]],
(double[6]){-2.0,-1.0,0.0,1.0,2.0,3.0}[vec[2]]
},
3*sizeof(double)); // NO C COMPILER ERROR
What does the first assignment do and why does it cause memory to change later in the program?
I'm writing a class that has two constructors. However, I can't get them to work quite right. One constructor has a parameter of an int (with a default value of 0) and the other has a parameter of a C-style string.
First of all, are these function prototypes correct for the constructors?
MyInt(int n = 0);// first constructor, int param, default value 0 MyInt(const char * c);// second constructor, c-style string param
Both constructors work fine in some cases but don't work in all cases. Here are some potential calls to these functions that are supposed to work:
// These two work fine MyInt x(12345), y("9876543210123456789"), // The array assignment doesn't work when the value is negative // I'm not allowing negative numbers, but I want to create the object and assign the array to 0 r1(-1000),
[Code] .....
Here's the private data from the class (from the header file):
private: int currentSize, maxSize; char* digits;// Pointer to an array of digits
// Increase the size of digits array by 5 void Grow ();
I'm writing a program in which I have to use a matrix to represent a file in code. because it's a file, the size of the matrix is undefined, and therefore the matrix has to be dynamic. I found out that my compiler doesn't like dynamic multidimensional arrays, so I was thinking of this matrix as a dynamic (monodimensional) array of other dynamic (monodimensional) arrays. My program (and thus this example) uses unsigned chars.
i am writing this bank accounts program using structures. i haven't implemented the function before that i want to check if the data is being read and printed. When i build and run the program in visual studio it gives me the following error. "No constructor could take the source type, or constructor overload resolution was ambiguous". Now whats wrong in this program?
/* Bank Accounts Program */ #include <iostream> #include <string> #include <fstream> #include <cstdlib>//needed to use system() function using namespace std; const int MAX_NUM = 50; struct Name{
I am making a tictactoe program that requires me to have a 3 by 3 two dimensional array of integers, in which the constructor should initialize the empty board to all zeroes. The program complies, but it keeps outputting garbage values and i'm not entirely sure why, My print function isn't complete yet, since I want to print out the array in a tic tac toe format, but i'm more concerned with why it's printing garbage values, here is my code:
I can't seem to remember everything I should about constructors. I'm looking for a way to create an array of structs, using a constructor. My code should explain.
struct myStruct { private: int structInt1, structInt2;
I want to pass an array to a constructor, but only the first value is passed--the rest looks like garbage. Here's a simplified version of what I'm working on:
#include <iostream> class board { public: int state[64]; board(int arr[])
[Code] ....
Why this doesn't work and how to properly pass an array? Notes: I don't want to copy the array. Also, I'm using MSVC++ 2010 Express.
I am currently practicing designing classes. In one exercise, I am trying to store 15 words in an array, and randomly print one (using the rand() functions and seeding it with crime. I have a header file, a respective .cpp file, and a main .cpp file. When I try to compile the code using g++ GuessWord.cpp UseGuessWord.cpp -o UseGuessWord, I get the following error in my constructor: expected primary-expression before ‘{’ token
I know everything works except my copy constructor! There are no errors. The program crashes when it goes to access the copy constructor. why the copy constructor isn't working?
#ifdef _MSC_VER #define _CRT_SECURE_NO_WARNINGS #endif #include <cstring> // access to C str functions #include "String.h" // access String class using namespace std; String::String( int size )// default constructor
Need a C++ constructor to initialize each members of an array. how to give value for for each elements of an array declared as a class object according to the users input.
I am making a tic tac toe program in which they are asking me to have a 3x3 2 dimensional array of integers and have the constructor initialize the empty board to all zeros. They also want me to place a 1 or 2 in each empty board space denoting the place where player 1 or player 2 would move The problem I'm having is, my code initializes the board to all zeros for each element of the array, and prints it out just fine, but I can't figure out how to re-initialize the values in the array to show where each player moves on the board... I was thinking about having a default constructor that has each value set to zero, and then use a setGame function that can change the values on the board to one or two depending on where the player moves....but I don't know if that's possible.....
How do I set the size of a member array via the class constructor if I know the size at compile time. I can do this with templates, see below, but this leads to code bloats, I think.
So one class declaration but objects with different array sizes.
Can't use constexpr. Can't use STL. Can't use new.
#include <iostream> using namespace std; template<int T> class MyArray { private: int array[T]; public: int getSize()
But I get these error: "--------------------Configuration: Sprite2 - Win32 Debug-------------------- Compiling...
Test Sprite2.cpp C:UsersJoaquimDocumentsVisual C 98Sprite2Test Sprite2.cpp(23) : error C2440: 'type cast' : cannot convert from 'void *' to 'struct Images' No constructor could take the source type, or constructor overload resolution was ambiguous Error executing cl.exe.
Code: Int** d = malloc( ROWS * sizeof(int*)); for (i = 0; i < ROWS; i++) d[i] = malloc(COLS * sizeof(int)); fx(d);
My question is, in a function declaration, why do I not have to specify the number of columns. How is this different than when I pass a static 2D array to a function, in which I must declare the function parameter with the number of columns.
Code: void fx(int d[][COLS]); VS. Code: void fx(int **d);
I remember in C++, when a dynamic array is allocated, the size of this array is stored right before the array in memory. Therefore compiler knows exactly how long, when this array is deleted.
Do all compilers store the size this way? Is it a safe method to get the size of a dynamic array?
Here is a example code, it works fine on Visual Studio 2012.
#include <iostream> using namespace std; class dummy { public: dummy() { cout<<"dummy created"<<endl;
I need to confirm that this problem cannot be solved without a pointer. Namely I need to read the rows and columns number from the user cin >> m, n and then use to declare an array int A[m][n];
However as m and n are not constants I am not able to do that. Is there a workaround? The following is the solution I came with BUT using a pointers which should be not the case.
// solution with using pointers as "int A[m][n]" does not work for me!!! void TwoDimensionalArrayFunc(){ int m = 0; int n = 0;
// instruct the users to enter array dimensions cout << "Please insert value for m:"; cin >> m;
arrays with dynamic sizes. That being said, I'm working with a simple code which seems to work just fine, my only concern is that once I display the 'char array', not only displays the user's inputs but some extra data, symbols and what not.
why, if to my understanding the first user's input already sets the size of the array
#include <iostream> #include <iomanip> using namespace std;
I have a 1000 bytes global array (which did not dynamic allocated).
I need to make "dynamic allocation" from this array.
For example - MyMalloc(50) ---> The program will allocate 50 bytes OF THE ARRAY'S SIZE. ------ MyFree(pointer) ---> I need to check if the pointer is in the array and free the space.
It should be managed by blocks. The array should also contain the manage variables (for me).
