#include <math.h>
#include <stdio.h>

/* Make sure to compile with -lm to link in the math library! */

/* Function taking a function pointer as an argument */
double compute_sum(double (*funcp)(double), double lo, double hi) {
  double sum = 0.0;
  /* Add values returned by the pointed-to function '*funcp' */
  for (int i = 0; i <= 100; i++) {
    double x, y;
    /* Use the function pointer 'funcp' to invoke the function */
    x = i/100.0 * (hi - lo) + lo;
    y = (*funcp)(x);
    sum += y;
  }
  return sum / 100;
}

int main(void) {
  double (*fp)(double); // Function pointer
  double sum;
  /* Use 'sin()' as the pointed-to function */
  fp = sin;
  sum = compute_sum(fp, 0.0, 1.0);
  printf("sum(sin): %f\n", sum);
  /* Use 'cos()' as the pointed-to function */
  fp = cos;
  sum = compute_sum(fp, 0.0, 1.0);
  printf("sum(cos): %f\n", sum);
  return 0;
}