import numpy as np


def relu(x):
    return np.maximum(x, 0)


def relu_prime(x):
    return np.where(x > 0, 1, 0)


def tanh(x):
    return np.tanh(x)


def tanh_prime(x):
    return 1 - np.tanh(x) ** 2


def sigmoid(x):
    return 1.0 / (1.0 + np.exp(-x))


def sigmoid_prime(x):
    s = sigmoid(x)
    return s / 1.0 - s