void read_stack (stack *s, char *filename) {
    int i;
    FILE *f = fopen (filename, "r");

    while (!feof (f)) {
      fscanf (f, "%d", &i);
      push (s, i);
    }
  }

  int main () {
    stack *sp = new_stack ();
    int sum = 0;

    read_stack (sp, "myfile.stack");
    do 
      sum = sum + pop (sp);
    while (! is_empty (sp));
  }