The Pointer Holy Grail

I think most computer scientists will agree that being able to do matrix algebra with pointers is, essentially, the holy grail of learning pointers in C. I present to you, the following beginnings of my matrix algebra library.

#include <stdlib.h>
#include <stdio.h>

#define M 5
#define N 5

void vprint(int *);
void vfill(int *, int);
void mprint(int **);
void mfill(int **);

int main(int argc, char **argv) {

  // first let's make us a vector!
  int *vector, i;
  vector = (int *)malloc(sizeof(int) * M);
  vfill(vector, N);
  vprint(vector);
  free(vector);

  // Now... let's make a vector of vectors!
  int **matrix, j;
  matrix = (int **)malloc(sizeof(int) * M * N);
  for (i=0; i<M; i++) {
   matrix[i] = (int *)malloc(sizeof(int) * N);
   printf("Malloc()'d %d bytes at address %p for matrix[%d].\n",
     sizeof(int) * N,
     (void *)matrix[i],
     i);
  }
  mfill(matrix);
  mprint(matrix);
  // before we can free the outer vector, 
  // we have to free the inner vectors!
  for (i=0; i<M; i++) {
    free(m[i]);
  }
  free(matrix);
  return 0;
}

void vprint(int *m) {
  int i;
  printf("--             --\n");
  printf("|");
  for (i=0; i<M; i++) {
   printf("%3d", m[i]);
  }
  printf("|\n");
  printf("--             --\n");
}

void mprint(int **m) {
  int i, j;
  printf("--             --\n");
  for (i=0; i<M; i++) {
   printf("|");
   for (j=0; j<N; j++) {
    printf("%3d", m[i][j]);
   }
   printf("|\n");
  }
  printf("--             --\n");
}

void vfill(int *m, int scalar) {
  int i;
  for (i=0; i<N; i++) {
   m[i] = i * scalar;
   printf("Assigning %d to the integer stored at %p\n",
     i * scalar,
     &m[i]);
  }
}

void mfill(int **m) {
  int i;
  for (i=0; i<M; i++) {
   vfill(m[i], i);
  }
}

Much happier now that I really know what's going on. I much prefer the subscripting syntax to pointer arithmetic. It's just easier to read... and... sane.