#include <math.h>
#include <stdio.h>
#define PI 3.14159
double integrate(double f(double),
double a, double b, unsigned steps) {
const double dx = (b - a) / steps;
double sum = 0.0;
for (double x = a; x < b; x += dx)
sum += fabs(f(x));
return dx * sum;
}
int main(void)
{
printf("fabs(+3) = %f\n", fabs(+3.0));
printf("fabs(-3) = %f\n", fabs(-3.0));
printf("fabs(-0) = %f\n", fabs(-0.0));
printf("fabs(-Inf) = %f\n", fabs(-INFINITY));
printf("Area under sin(x) in [-PI, PI] = %f\n", integrate(sin, -PI, PI, 5101));
}