gistfile1.txt

#include <stdio.h>
#include <math.h>
 
typedef double (*function)(double);
typedef double (*sum_function)(double, double, double, function);
 
double trap(double startX, double endX, double numOfIntervals, sum_function sum_fn, function fn);
double sum_fn(double startX, double intervalSize, double endX, function fn);
double fn(double x);
 
int main(void){
	double startX = -2;
	double endX = 2;
	double numOfIntervals = 128;
	 
	printf("%f\n", trap(startX, endX, numOfIntervals, &sum_fn, &fn));
	 
	return 0;
}
 
double trap(double startX, double endX, double numOfIntervals, sum_function sum_fn, function fn){
	double intervalSize = (endX-startX)/numOfIntervals;

	 
	return (intervalSize/2)*(fn(startX)+fn(endX)+2*sum_fn(startX, intervalSize, endX, fn));
}
 
double sum_fn(double startX, double intervalSize, double endX, function fn){
	double sum = 0;
	double i;
	for (i = startX+intervalSize; i < endX; i += intervalSize)
	{
		sum +=fn(i);
	}
	return sum;
}
 
double fn(double x){
	return sqrt(4-pow(x,2));
}