#define N 16

typedef int fix_matrix[N][N];

#define IDX(n, i, j) ((i)*(n)+(j))

/* Get element a[i][j] */
int fix_ele(fix_matrix a, int i, int j) {
  return a[i][j];
}

/* Get element a[i][j] */
int var_ele(int n, int a[n][n], int i, int j) {
  return a[i][j];
}

/* Get element a[i][j] */
int vec_ele(int n, int *a, int i, int j) {
  return a[IDX(n,i,j)];
}

/* Retrieve column j from array */
void fix_column(fix_matrix a, int j, int *dest)
{
  int i;
  for (i = 0; i < N; i++)
    dest[i] = a[i][j];
}

/* Retrieve column j from array */
void vec_column(int n, int *a, int j, int *dest)
{
  int i;
  for (i = 0; i < n; i++)
    dest[i] = a[IDX(n,i,j)];
}

/* Retrieve column j from array */
void var_column(int n, int a[n][n], int j, int *dest)
{
  int i;
  for (i = 0; i < n; i++)
    dest[i] = a[i][j];
}

/* Retrieve column j from array */
void fix_column_p(fix_matrix a, int j, int *dest)
{
  int *ap = &a[0][j];
  int *endp = &a[N][j];
  while (ap != endp) {
    *dest++ = *ap;
    ap += N;
  }
}