import random
import collections

# Generic n-ary tree
RoseTree = collections.namedtuple('RoseTree', 'a children')

def gen_int():
    def _gen_int(rng, size):
        return rng.randrange(0, size)

    return _gen_int

def gen_v(g):
    def _gen_v(rng, size):
        n = rng.randrange(0, size)
        return [g(rng, size) for _ in range(n)]
    return _gen_v

def fmap(f, g):
    def _fmap(rng, size):
        result = g(rng, size)
        return f(result)
    return _fmap

rng = random.Random()
print gen_int()(rng, 20)

v = gen_v(gen_int())

print v(rng, 10)

print fmap(lambda x: x * 2, v)(rng, 10)

even_v = gen_v(fmap(lambda x: x * 2, gen_int()))

print even_v(rng, 10)