Issue with passing an argument to function-CodePudding

I'm working with C and found a problem. I want to pass an argument to a function. The argument must be a 2d array. When I try to do it, I get 2 errors:

Too many initializer values

and

initializing cannnot convert from initializer list to size_t**

How do I fix this? I've tried with changing it as 5x5 matrix, but it doesn't make it good.

size_t** matrix =
{
    {1, 16, 20, 23, 25},
    {6, 2, 17, 21, 24},
    {10, 7, 3, 18, 22},
    {13, 11, 8, 4, 19},
    {15, 14, 12, 9, 5},
};
set<bool> set1 = iterateover(matrix);

The function:

std::set<bool> iterateover(size_t **arrayy)

CodePudding user response：

size_t** matrix defines a pointer to a pointer to a size_t. An array is not a pointer. It can decay to a pointer, but in the case of a 2D array, it decays to a pointer to a 1D array, not to a pointer to a pointer.

The closest thing I can think of to what you seem to be after is

// here be the data
size_t actual_matrix[][5] = // note: We can omit the first dimension but we cannot 
                            // omit the inner dimensions
{
    {1, 16, 20, 23, 25},
    {6, 2, 17, 21, 24},
    {10, 7, 3, 18, 22},
    {13, 11, 8, 4, 19},
    {15, 14, 12, 9, 5},
};

// an array of pointers to the rows of actual data. This 1D array of pointers will 
// decay to a size_t **
size_t * matrix[] =
{
    actual_matrix[0],
    actual_matrix[1],
    actual_matrix[2],
    actual_matrix[3],
    actual_matrix[4],
};
// now we have the correct type to use with iterateover
std::set<bool> set1 = iterateover(matrix);

CodePudding user response：

I want to pass an argument to a function. The argument must be a 2d array.

You can make iteratreOver a function template which can take a 2D array by reference, as shown below. You can make additional changes to the function according to your needs since it is not clear from the question what your iterateover function does. I have just printed all the elements inside the 2D array.

#include <iostream>
template<typename T,std::size_t N, std::size_t M>
void iterateOver(T (&arr)[N][M])
{
    for(std::size_t i= 0; i < N;   i)
    {
        for(std::size_t j = 0; j < M;   j)
        {
            std::cout<<arr[i][j] <<" ";
        }
        std::cout<<std::endl;
    }
}
int main()
{
    size_t matrix[5][5] =
    {
        {1, 16, 20, 23, 25},
        {6, 2, 17, 21, 24},
        {10, 7, 3, 18, 22},
        {13, 11, 8, 4, 19},
        {15, 14, 12, 9, 5},
    };
    //call iterateOver by passing the matrix by reference
    iterateOver(matrix);
   
}

The output of the above program can be seen here:

1 16 20 23 25 
6 2 17 21 24 
10 7 3 18 22 
13 11 8 4 19 
15 14 12 9 5