Array of pointers to an array of fixed size

Question

I tried to assign two fixed-size arrays to an array of pointers to them, but the compiler warns me and I don\'t understand why.

int A[5][5];
int B[5][5];
int         


        

Answer 1

I am a great believer in using typedef:

#define SIZE 5

typedef int  OneD[SIZE]; // OneD is a one-dimensional array of ints
typedef OneD TwoD[SIZE]; // TwoD is a one-dimensional array of OneD's
                         // So it's a two-dimensional array of ints!

TwoD a;
TwoD b;

TwoD *c[] = { &a, &b, 0 }; // c is a one-dimensional array of pointers to TwoD's
                           // That does NOT make it a three-dimensional array!

int main() {
    for (int i = 0; c[i] != 0; ++i) { // Test contents of c to not go too far!
        for (int j = 0; j < SIZE; ++j) {
            for (int k = 0; k < SIZE; ++k) {
//              c[i][j][k] = 0;    // Error! This proves it's not a 3D array!
                (*c[i])[j][k] = 0; // You need to dereference the entry in c first
            } // for
        } // for
    } // for
    return 0;
} // main()