Source code for returns.pointfree.lash

from typing import Callable, TypeVar

from returns.interfaces.lashable import LashableN
from import Kinded, KindN, kinded

_FirstType = TypeVar('_FirstType')
_SecondType = TypeVar('_SecondType')
_ThirdType = TypeVar('_ThirdType')
_UpdatedType = TypeVar('_UpdatedType')

_LashableKind = TypeVar('_LashableKind', bound=LashableN)

[docs]def lash( function: Callable[ [_SecondType], KindN[_LashableKind, _FirstType, _UpdatedType, _ThirdType], ], ) -> Kinded[Callable[ [KindN[_LashableKind, _FirstType, _SecondType, _ThirdType]], KindN[_LashableKind, _FirstType, _UpdatedType, _ThirdType], ]]: """ Turns function's input parameter from a regular value to a container. In other words, it modifies the function signature from: ``a -> Container[b]`` to: ``Container[a] -> Container[b]`` Similar to :func:`returns.pointfree.bind`, but works for failed containers. This is how it should be used: .. code:: python >>> from returns.pointfree import lash >>> from returns.result import Success, Failure, Result >>> def example(argument: int) -> Result[str, int]: ... return Success(argument + 1) >>> assert lash(example)(Success('a')) == Success('a') >>> assert lash(example)(Failure(1)) == Success(2) Note, that this function works for all containers with ``.lash`` method. See :class:`returns.interfaces.lashable.Lashable` for more info. """ @kinded def factory( container: KindN[_LashableKind, _FirstType, _SecondType, _ThirdType], ) -> KindN[_LashableKind, _FirstType, _UpdatedType, _ThirdType]: return container.lash(function) return factory