Please help with passing multidimensional arrays

Question

Hi,

I'm writing a simple test program to pass multidimensional arrays. I've been struggling to get the signature of the callee function.

The code I have:

void p(int (*s)[100], int n) { ... }

...

{
  int s1[10][100], s2[10][1000];
  p(s1, 100);
}

This code appears to work, but is not what I intended. I want the function p to be oblivious whether the range of values is either 100 or 1000, but should know there are 10 pointers (by use of function signature).

As a first attempt:

void p(int (*s)[10], int n) // n = # elements in the range of the array

and as a second:

void p(int **s, int n) // n = # of elements in the range of the array

But to no avail can I seem to get these to work correctly. I don't want to hardcode the 100 or 1000 in the signature, but instead pass it in, keeping in mind there will always be 10 arrays.

Obviously, I want to avoid having to declare the function:

void p(int *s1, int *s2, int *s3, ..., int *s10, int n) 

FYI, I'm looking at the answers to a similar question but still confused.

Answer 1

You could also create a struct for the matrix and pass it to the function p

struct Matrix{
     int **array;
     int n;
     int m;
};


void p(Matrix *k){
     length=k->m;
     width=k->n;
     firstElement=k->array[0][0];
}

Answer 2

You need to transpose your arrays for this to work. Declare

int s1[100][10];
int s2[1000][10];

Now, you can pass these to a function like this:

void foo(int (*s)[10], int n) {
    /* various declarations */
    for (i = 0; i < n; i++)
        for (j = 0; j < 10; j++)
            s[i][j] += 1
}

Because of the way the C type system works, an array argument can only be "flexible" in the sense you want in its left-most index.