base-4.6.0.0: Basic libraries

Portabilityportable
Stabilityprovisional
Maintainerlibraries@haskell.org
Safe HaskellTrustworthy

Data.Functor

Description

Functors: uniform action over a parameterized type, generalizing the map function on lists.

Synopsis

Documentation

class Functor f whereSource

The Functor class is used for types that can be mapped over. Instances of Functor should satisfy the following laws:

 fmap id  ==  id
 fmap (f . g)  ==  fmap f . fmap g

The instances of Functor for lists, Maybe and IO satisfy these laws.

Methods

fmap :: (a -> b) -> f a -> f bSource

(<$) :: a -> f b -> f aSource

Replace all locations in the input with the same value. The default definition is fmap . const, but this may be overridden with a more efficient version.

(<$>) :: Functor f => (a -> b) -> f a -> f bSource

An infix synonym for fmap.