bisect.c

// c program for implementation of bisection -- abhay's version
#include<stdio.h>

float fun(float);

main()
{
    float x1, x2, r;
    int i, j;
    for(i=0; i<10; i++)
    {
        printf("i = %d, fun(i) = %f\n", i, fun(i));
        if(fun(i) < 0)
            break;
    }
    printf("\n i = %d\n", i);

    x1 = i;

    printf("x1 = %f\n", x1);

    for(j=0; j<10; j++)
    {
        if(fun(j) > 0)
            break;
    }

    x2 = j;
    printf("x2 = %d", x2);

    while(1)
    {
        r = (x1 + x2)/2;
        if( fun(r) < 0)
            x1 = r;
        else x2 = r;

        if( abs(fun(x2) - fun(x1) <= 0.0001))
            break;
    }

    printf("\nYour root is : %f", r);

    return 0;
}

float fun(float x)
{
    return (x*x) - (4*x) + 1;
}