Method loop

returns/iterables.py:51–91

Allows to make declarative loops for any ``ApplicativeN`` subtypes. Quick example: .. code:: python >>> from typing import Callable >>> from returns.maybe import Some >>> from returns.iterables import Fold >>> def sum_two(first: in

(
        cls,
        iterable: Iterable[
            KindN[_ApplicativeKind, _FirstType, _SecondType, _ThirdType],
        ],
        acc: KindN[_ApplicativeKind, _UpdatedType, _SecondType, _ThirdType],
        function: Callable[
            [_FirstType],
            Callable[[_UpdatedType], _UpdatedType],
        ],
    )

    @kinded
    @classmethod
    def loop(
        cls,
        iterable: Iterable[
            KindN[_ApplicativeKind, _FirstType, _SecondType, _ThirdType],
        ],
        acc: KindN[_ApplicativeKind, _UpdatedType, _SecondType, _ThirdType],
        function: Callable[
            [_FirstType],
            Callable[[_UpdatedType], _UpdatedType],
        ],
    ) -> KindN[_ApplicativeKind, _UpdatedType, _SecondType, _ThirdType]:
        """
        Allows to make declarative loops for any ``ApplicativeN`` subtypes.

        Quick example:

        .. code:: python

          >>> from typing import Callable
          >>> from returns.maybe import Some
          >>> from returns.iterables import Fold

          >>> def sum_two(first: int) -> Callable[[int], int]:
          ...     return lambda second: first + second

          >>> assert Fold.loop(
          ...     [Some(1), Some(2), Some(3)],
          ...     Some(10),
          ...     sum_two,
          ... ) == Some(16)

        Looks like ``foldl`` in some other languages with some more specifics.
        See: https://philipschwarz.dev/fpilluminated/?page_id=348#bwg3/137

        .. image:: https://i.imgur.com/Tza1isS.jpg

        Is also quite similar to ``reduce``.

        Public interface for ``_loop`` method. Cannot be modified directly.
        """
        return cls._loop(iterable, acc, function, _concat_applicative)

    @final
    @kinded