function within(next_result_function, epsilon)
    prev_result = next_result_function()
    curr_result = next_result_function()
    while math.abs(prev_result - curr_result) > epsilon do
        prev_result = curr_result
        curr_result = next_result_function()
    end
    return curr_result
end

function newton_raphson_sqrt(radicand, epsilon, guess=10.0)
    square_root = guess
    function next()
        square_root = (square_root + radicand / square_root) / 2.0
        return square_root
    end
    return within(next, epsilon)
end

print(newton_raphson_sqrt(9.0, 1e-2, 10.0))
print(newton_raphson_sqrt(9.0, 1e-9, 10.0))