import numpy as np


class ReLU:
    def __call__(self, x):
        return np.maximum(0, x)

    def derivative(self, x):
        return (x > 0).astype(float)


class Sigmoid:
    def __call__(self, x):
        return 1 / (1 + np.exp(-x))

    def derivative(self, x):
        sig = self.__call__(x)
        return sig * (1 - sig)


relu = ReLU()
sigmoid = Sigmoid()