Portability	portable
Stability	provisional
Maintainer	libraries@haskell.org

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, Data.Maybe.Maybe and System.IO.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.

Instances

Functor []
Functor IO
Functor Maybe
Functor ReadP
Functor ReadPrec
Functor STM
Functor ZipList
Functor Id
Functor ((->) r)
Functor (Either a)
Functor ((,) a)
Functor (ST s)
Ix i => Functor (Array i)
Functor (ST s)
Monad m => Functor (WrappedMonad m)
Functor (Const m)
Functor (StateR s)
Functor (StateL s)
Arrow a => Functor (WrappedArrow a b)

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

An infix synonym for fmap.