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from collections.abc import Callable
from typing import TypeVar
from returns.interfaces.lashable import LashableN
from returns.primitives.hkt import Kinded, KindN, kinded
_FirstType = TypeVar('_FirstType')
_SecondType = TypeVar('_SecondType')
_ThirdType = TypeVar('_ThirdType')
_UpdatedType = TypeVar('_UpdatedType')
_LashableKind = TypeVar('_LashableKind', bound=LashableN)
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
|
