#include "f.h"

double intsimp_f(double (*f)(double x), double a, double b, int n)
    {
    double sum = 0;
    double m, k;
    double h = (b-a)/(n);
    double cur = f(a);
    double old = cur;
    int i = 0;

    for(i = 1; i <= n; i++)
        {
        old = cur;
        cur = f(a + i*h);

        m = (cur - old)/h;
        k = (old*(a + i*h) - cur*(a + (i-1)*h))/h;

        sum += 2*m*fabs(a + i*h)*sqrt(fabs(a + i*h))/3;
        sum += 2*k*sqrt(fabs(a + i*h))*(a + i*h)/fabs(a + i*h);
        sum -= 2*m*fabs(a + (i-1)*h)*sqrt(fabs(a + (i-1)*h))/3;
        sum -= 2*k*sqrt(fabs(a + (i-1)*h))*(a + (i-1)*h)/fabs(a + (i-1)*h);
        }
    return sum;
    }

static int cnt = 0;

double f(double x)
    {
    cnt++;
    return x;
    }

int get_cnt(void)
    {
    return cnt;
    }