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from collections.abc import Callable
from typing import TypeVar
from returns.interfaces.specific.maybe import MaybeLikeN
from returns.primitives.hkt import Kinded, KindN, kinded
_FirstType = TypeVar('_FirstType')
_SecondType = TypeVar('_SecondType')
_ThirdType = TypeVar('_ThirdType')
_UpdatedType = TypeVar('_UpdatedType')
_MaybeLikeKind = TypeVar('_MaybeLikeKind', bound=MaybeLikeN)
def bind_optional(
function: Callable[[_FirstType], _UpdatedType | None],
) -> Kinded[
Callable[
[KindN[_MaybeLikeKind, _FirstType, _SecondType, _ThirdType]],
KindN[_MaybeLikeKind, _UpdatedType, _SecondType, _ThirdType],
]
]:
"""
Binds a function returning optional value over a container.
In other words, it modifies the function's
signature from:
``a -> Optional[b]``
to:
``Container[a] -> Container[b]``
.. code:: python
>>> from typing import Optional
>>> from returns.pointfree import bind_optional
>>> from returns.maybe import Some, Nothing
>>> def example(argument: int) -> Optional[int]:
... return argument + 1 if argument > 0 else None
>>> assert bind_optional(example)(Some(1)) == Some(2)
>>> assert bind_optional(example)(Some(0)) == Nothing
>>> assert bind_optional(example)(Nothing) == Nothing
Note, that this function works
for all containers with ``.bind_optional`` method.
See :class:`returns.primitives.interfaces.specific.maybe._MaybeLikeKind`
for more info.
"""
@kinded
def factory(
container: KindN[_MaybeLikeKind, _FirstType, _SecondType, _ThirdType],
) -> KindN[_MaybeLikeKind, _UpdatedType, _SecondType, _ThirdType]:
return container.bind_optional(function)
return factory
|
