#include <stdio.h>

/* Underscores */
double f (double x);
int same_sign(double x, double y);
double middle_of(double x, double y);
int is_small_number(double x);

double find_root_between(double a, double b)
{
    double l = a, u = b;
    while (!is_small_numerb(f(middle_of(l, u)))) { 
        if(same_sign(f(middle_of(l, u)), f(u)))
            u = middle_of(l, u);
        else 
            l = middle_of(l, u);
    }
    return middle_of(l, u);
}  

int main (void)
{
    find_root_between(-3.0, 5.0);
}