연습문제 1.35

const tolerance = 0.0001;

function abs(x){
    return x > 0 ? x : -x;
}

function fixed_point(f, first_guess) {
    function close_enough(x, y) {
        return abs(x - y) < tolerance;
    }
    function try_with(guess) {
        const next = f(guess);
        return close_enough(guess, next)
            ? next
            : try_with(next);
    }
    return try_with(first_guess);
}

fixed_point(x => 1 + 1/x, 1.0);