Source code for returns.pointfree.map
from typing import Callable, TypeVar
from returns.interfaces.mappable import MappableN
from returns.primitives.hkt import Kinded, KindN, kinded
_FirstType = TypeVar('_FirstType')
_SecondType = TypeVar('_SecondType')
_ThirdType = TypeVar('_ThirdType')
_UpdatedType = TypeVar('_UpdatedType')
_MappableKind = TypeVar('_MappableKind', bound=MappableN)
[docs]def map_(
function: Callable[[_FirstType], _UpdatedType],
) -> Kinded[Callable[
[KindN[_MappableKind, _FirstType, _SecondType, _ThirdType]],
KindN[_MappableKind, _UpdatedType, _SecondType, _ThirdType],
]]:
"""
Lifts function to be wrapped in a container for better composition.
In other words, it modifies the function's
signature from:
``a -> b``
to: ``Container[a] -> Container[b]``
This is how it should be used:
.. code:: python
>>> from returns.io import IO
>>> from returns.pointfree import map_
>>> def example(argument: int) -> float:
... return argument / 2
>>> assert map_(example)(IO(1)) == IO(0.5)
Note, that this function works for all containers with ``.map`` method.
See :class:`returns.primitives.interfaces.mappable.MappableN` for more info.
See also:
- https://wiki.haskell.org/Lifting
"""
@kinded
def factory(
container: KindN[_MappableKind, _FirstType, _SecondType, _ThirdType],
) -> KindN[_MappableKind, _UpdatedType, _SecondType, _ThirdType]:
return container.map(function)
return factory