Source code for returns.pointfree.bind

from typing import Callable, TypeVar

from returns.interfaces.bindable import BindableN
from import Kinded, KindN, kinded

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

_BindableKind = TypeVar('_BindableKind', bound=BindableN)

[docs]def bind( function: Callable[ [_FirstType], KindN[_BindableKind, _UpdatedType, _SecondType, _ThirdType], ], ) -> Kinded[Callable[ [KindN[_BindableKind, _FirstType, _SecondType, _ThirdType]], KindN[_BindableKind, _UpdatedType, _SecondType, _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.lash`, but works for successful containers. This is how it should be used: .. code:: python >>> from returns.pointfree import bind >>> from returns.maybe import Maybe, Some, Nothing >>> def example(argument: int) -> Maybe[int]: ... return Some(argument + 1) >>> assert bind(example)(Some(1)) == Some(2) >>> assert bind(example)(Nothing) == Nothing Note, that this function works for all containers with ``.bind`` method. See :class:`returns.primitives.interfaces.bindable.BindableN` for more info. """ @kinded def factory( container: KindN[_BindableKind, _FirstType, _SecondType, _ThirdType], ) -> KindN[_BindableKind, _UpdatedType, _SecondType, _ThirdType]: return container.bind(function) return factory