#include <stdio.h>
/* trapez.c : 1999 3 3 by Y.Yamazaki and T.Oguni */
double trapez(double (*f)(), double a, double b, int n)
{
  int i;
  double x, h, sum;
  h = (b-a)/n;
  sum = (*f)(a)+(*f)(b);
  for (i=1, x=a+h; i<n; i++, x+=h) sum += 2.0*(*f)(x);
  return (h/2.0)*sum;
}
double func(double x)
{ return x*x*x*x*x*x*x; }
void main()
{ printf("f(x)dx = %f\n", trapez(func, 0., 1., 4)); }