Relude.Functor.Fmap

This module contains useful functions to work with Functor type class.

Documentation

(<<$>>) :: (Functor f, Functor g) => (a -> b) -> f (g a) -> f (g b) infixl 4

Alias for fmap . fmap. Convenient to work with two nested Functors.

>>> negate <<$>> Just [1,2,3]
Just [-1,-2,-3]

(<&>) :: Functor f => f a -> (a -> b) -> f b infixl 1

Flipped version of <$>.

(<&>) = flip fmap

Examples

Apply (+1) to a list, a Just and a Right:

>>> Just 2 <&> (+1)
Just 3

>>> [1,2,3] <&> (+1)
[2,3,4]

>>> Right 3 <&> (+1)
Right 4

Since: base-4.11.0.0

flap :: Functor f => f (a -> b) -> a -> f b

Takes a function in a Functor context and applies it to a normal value.

>>> flap (++) "relude" "P"
"Prelude"

(??) :: Functor f => f (a -> b) -> a -> f b infixl 4

Operator version of the flap function.

>>> [(+2), (*3)] ?? 5
[7,15]

>>> Just (+3) ?? 5
Just 8