#include "matrix.h"

elem trace(matrix a, int m, int n)
{
   int    i;
   int    k;
   elem   sum = 0;

   k = (m < n) ? m : n;
   for (i = 1; i <= k; ++i)
      sum += a[i][i];               /* sum the elements on the main diagonal */
   return sum;
}