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

unsigned sleep(unsigned seconds);

double f(double x);
void bisection(double x0, double x1, double tol, int max_itno);

// Driver program 
int main() 
{ 
    // Initial values  
    double a =-30, b = 30; 
    bisection(a, b,1e-16,10000); 
    return 0; 
} 


void bisection(double x0, double x1, double tol, int max_itno) 
{ 
   int i;
   double x;

    if (f(x0) * f(x1) >= 0) 
    { 
        printf("You have to choose an initial interval such that f(x0)f(x1)<0\n"); 
        return; 
    } 
    i=0;
    x = x0; 
    while (fabs(x1-x0) >= tol&&i<max_itno) 
    { 
        // Find middle point 
        x = (x0+x1)/2; 
  
        // Check if middle point is root 
        if (fabs(f(x))<=tol) 
            break; 
  
        // Decide the side to repeat the steps 
        else if (f(x)*f(x0) < 0) 
            x1 = x; 
        else
            x0 = x; 

     i++;
    printf("iteration number: %d \tf(%.15lf) = %.15lf\n",i,x,f(x));
    } 
} 

// Define function

double f(double x) 
{ 
    double y;
//sleep(1);
y=cos(x)-x;
    return y;
}