base-4.3.0.0: Basic libraries

Portabilityportable
Stabilityprovisional
Maintainer[email protected]

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 [::] 
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) 
Monad m => Functor (WrappedMonad m) 
Functor (Const m) 
Functor (StateR s) 
Functor (StateL s) 
Functor (ST s) 
Arrow a => Functor (WrappedArrow a b) 

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

An infix synonym for fmap.