Haskellの合成演算子 . をPythonで

compose.py

def _compose(f_t_u, f_u_r):
    return lambda t: f_u_r(f_t_u(t))


class Compose(object):
    def __init__(self):
        # :type: T -> U
        self.func = lambda a: a

    def __call__(self, val):
        return self.func(val)


def composable(original_func):
    '''
    decorator to dispatch the function should be chaining method of masala.Stream

    :type original_func: U -> V
    '''
    func_name = original_func.__name__

    def _compose_with_method_chaining(self):
        self.func = _compose(self.func, original_func)
        return self
    setattr(Compose, func_name, _compose_with_method_chaining)
    return original_func


@composable
def to_i(x):
    return int(x)


@composable
def to_s(i):
    return str(i)


@composable
def add_2(i):
    return i + 2


@composable
def decoration(s):
    return '<< ' + s + '!!! >>'


if __name__ == '__main__':
    composer = Compose()
    print composer . to_i() . add_2() . add_2()(111)
    print Compose() . to_i() . add_2() . add_2() . to_s() (22222)