numcmp:compare strings numerically

#include <stdlib.h>

/*numcmp: compare s1 and s2 numerically */
int numcmp(char *s1, char *s2){
    double v1, v2;

     v1 = atof(s1);
     v2 = atof(s2);
     if (v1 < v2)
         return -1;
     else if (v1 > v2)
          return 1;
     else
          return 0;
}