gistfile1.txt

#include <stdio.h>

double
integrate(
    double a,
    double b,
    double (*f)(double)
){
    int i, size = 1000;
    double area = 0., d = (b - a) / size;

    for (i = 0; i < size; i++) {
        area += f(a + i * d) * d;
    }
    return area;
}

double
f1(double x) {
    return x;
}

double
f2(double x) {
    return x * x;
}

int
main(int argc, char* argv[]) {
    printf("%f\n", integrate(0., 3., f1));
    printf("%f\n", integrate(0., 3., f2));
    return 0;
}