Add an infix operator for Applicative.apply

monads/applicative.py

@@ -18,3 +18,5 @@ class Applicative(Functor[T]):
     # https://github.com/python/mypy/issues/1317
     def apply(self, functor: Any) -> Functor[S]:  # pragma: no cover
         raise NotImplementedError
+
+    __and__ = lambda other, self: Applicative.apply(self, other)

monads/list.py

@@ -34,5 +34,6 @@ class List(Monad[T], Monoidal[list]):
         return List(self.value + other.value)
 
     __add__ = mappend
+    __and__ = lambda other, self: List.apply(self, other)
     __mul__ = __rmul__ = map
     __rshift__ = bind

monads/maybe.py

@@ -61,6 +61,7 @@ class Maybe(Monad[T]):
             return Nothing()
 
     __rshift__ = bind
+    __and__ = lambda other, self: Maybe.apply(self, other)
     __mul__ = __rmul__ = map
 
 

monads/result.py

@@ -65,6 +65,7 @@ class Result(Monad[T], Generic[T, E]):
         return self.map(Maybe.pure).withDefault(Nothing())
 
     __rshift__ = bind
+    __and__ = lambda other, self: Result.apply(self, other)
     __mul__ = __rmul__ = map
 
 

tests/test_applicatives.py

@@ -12,3 +12,10 @@ def test_fmap_using_ap(monad) -> None:
     f: Callable[[int], int] = lambda x: x + 1
     m: Applicative[int] = monad.pure(3)
     assert m.map(f) == m.apply(monad.pure(f))
+
+
+def test_apply_and_operator(monad) -> None:
+    subtract: Callable[[int], Callable[[int], int]] = lambda x: lambda y: x - y
+    ten = monad.pure(10)
+    six = monad.pure(6)
+    assert six.apply(ten.map(subtract)) == subtract * ten & six