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patterncppCritical

Passing a 2D array to a C++ function

Submitted by: @import:stackoverflow-api··
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functionarraypassing

Problem

I have a function which I want to take, as a parameter, a 2D array of variable size.

So far I have this:
void myFunction(double** myArray){
myArray[x][y] = 5;
// etc...
}


And I have declared an array elsewhere in my code:
double anArray[10][10];


However, calling myFunction(anArray) gives me an error.

I do not want to copy the array when I pass it in. Any changes made in myFunction should alter the state of anArray. If I understand correctly, I only want to pass in as an argument a pointer to a 2D array. The function needs to accept arrays of different sizes also. So for example, [10][10] and [5][5]. How can I do this?

Solution

There are three ways to pass a 2D array to a function:

-
The parameter is a 2D array

int array[10][10];
void passFunc(int a[][10])
{
    // ...
}
passFunc(array);


-
The parameter is an array containing pointers

int *array[10];
for(int i = 0; i < 10; i++)
    array[i] = new int[10];
void passFunc(int *a[10]) //Array containing pointers
{
    // ...
}
passFunc(array);


-
The parameter is a pointer to a pointer

int **array;
array = new int *[10];
for(int i = 0; i <10; i++)
    array[i] = new int[10];
void passFunc(int **a)
{
    // ...
}
passFunc(array);

Code Snippets

int array[10][10];
void passFunc(int a[][10])
{
    // ...
}
passFunc(array);
int *array[10];
for(int i = 0; i < 10; i++)
    array[i] = new int[10];
void passFunc(int *a[10]) //Array containing pointers
{
    // ...
}
passFunc(array);
int **array;
array = new int *[10];
for(int i = 0; i <10; i++)
    array[i] = new int[10];
void passFunc(int **a)
{
    // ...
}
passFunc(array);

Context

Stack Overflow Q#8767166, score: 542

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