lazy.py

def memoize(func):
    memod = {}
    def wrapper(*args):
        if args not in memod:
            memod[args] = func(*args)
        return memod[args]
    return wrapper

@memoize
def unpack(func):
    if callable(func):
        return unpack(func())
    return func

# ===============================

def join(fst, snd):
    return (fst, snd)

def map(f, l):
    if unpack(l) is None:
        return None
    lhead, ltail = unpack(l)
    return join(f(lhead), lambda: map(f, ltail))

def nums():
    return join(1, lambda: map(lambda x: unpack(x) + 1, nums))

def take(count, l):
    if unpack(count) == 0:
        return None

    if unpack(l) is None:
        return None
    lhead, ltail = unpack(l)
    return join(lhead, take(unpack(count) - 1, ltail))

def show(l):
    if unpack(l) is None:
        return "[eol]"
    lhead, ltail = unpack(l)
    return str(unpack(lhead)) + " " + show(ltail)

#<<< l = join(lambda: 2, join(lambda: 1, lambda: None))
l = nums()
print(show(take(lambda: 23, l)))