Trun Python into Haskell - a test

gfib.py

from itertools import islice
from typing import TypeVar, NoReturn
from collections.abc import Callable, Generator, Sequence, Iterable 

T = TypeVar('T')

def gfib(f: Callable[[Sequence[T]], T],
         xs:Sequence[T]) -> Generator[T]:
    while True:
        x, *xs = *xs, f(xs)
        yield x

def itake(n: int,
          ys: Iterable[T]) -> list[T]:
    if isinstance(n, int) and (n >= 1):
        return list(islice(ys, n))
    else:
        raise ValueError("n must be a integer greater than 0.")

class GfibSeq(object):

    def __init__(self,
                 f: Callable[[Sequence[T]], T],
                 xs: Sequence[T]) -> NoReturn:
        self.__gen = gfib(f, xs)
        self.__xs = []

    def take(self, n: int) -> list[T]:
        if len(self.__xs) < n:
            self.__xs = self.__xs + itake(n - len(self.__xs), self.__gen)
        return self.__xs[:n]

    def nth(self, n: int) -> T:
        self.take(n + 1)[-1]

# gfib.py ends here

Few things are left:

• No Monad yet
• ...