Question

I have an NxN 2D array implemented as a 1D array using A[N*i+j]. I want to make references to the columns of the array and be able to pass them to functions as regular column vectors. You can see an example below for N=3. The function returns just the square of the vector passed to it:

#include <stdio.h>

int func(int* vec[3]){
    int result=0;
    for(int i=0;i<3;i++){
        result+=(*vec[i])*(*vec[i]);
        printf("vec[%d]=%d\n",i,*vec[i]);
    }
    return result;
}

void main(){
    int A[]={0,1,2,3,4,5,6,7,8};

    int *a[3][3];

    for(int i=0;i<3;i++){
        for(int j=0;j<3;j++){
            a[j][i]=&A[3*i+j];
        }
    }
    for(int i=0;i<3;i++){
        printf("vector %d\n",i);
        for(int j=0;j<3;j++){
            printf("%d\n",*a[i][j]);
        }
    }

    printf("%d\n",func(a[0]));
}

This works but the problem is the function works only for arguments of type int* vec[3]. What I would really like is to have the function taking an argument of type int vec[3] but I’m confused on how I should then pass the vector of pointers as a vector of the values the vector elements point to.

Answer 1

It is not possible to do what you want, atleast not in C.