metodo de biseccion

fn biseccion(a: f64, b: f64, epsilon: f64, max_iter: i32) -> f64 {
    let mut iter = 0;

    let mut xn = (a + b) / 2f64;
    let mut fxn = f(xn);
    let mut xn_1 = 0f64;
    let mut fxn_1 = 0f64;

    loop {
        xn_1 = (a + b) / 2f64;
        fxn_1 = f(xn_1);

        if (iter >= max_iter) || (xn_1 - xn).abs() <= epsilon {
            break;
        }

        iter += 1;

        if fxn * fxn_1 < 0f64 {
            b = xn_1;
        } else {
            a = xn_1;
        }

        xn = xn_1;
        fxn = fxn_1;
    }

    return xn;