math analisys homework

binarySearch.c

#include <stdio.h>
#include <math.h>

#define true 1

typedef double (*mathFn)(double);

const double EPS = 1e-9;


double f(double);
double binarySearch(double, double, double, mathFn);


int main(int argc, char const *argv[])
{
	mathFn homeTask = &f;
	double result = binarySearch(-3.0, -1.0, 0.0, homeTask);
	printf("%.15f\n", result);
	return 0;
}


double f(double x)
{
	return sin(x) - x - 1;
}


double binarySearch(double leftThreshold,
		double rightThreshold,
		double requiredValue,
		mathFn func)
{
	double root;
	double val;

	while (true)
	{
		root = (leftThreshold + rightThreshold) / 2.0;
		val = func(root);

		if (fabs(val) < EPS)
		{
			return root;
		}
		else if (val < 0)
		{
			rightThreshold = root;
		}
		else
		{
			leftThreshold = root;
		}
	}
}