Copyright	(c) The University of Glasgow 2001
License	BSD-style (see the file libraries/base/LICENSE)
Maintainer	libraries@haskell.org
Stability	provisional
Portability	portable
Safe Haskell	Trustworthy
Language	Haskell2010

Data.Functor

Description

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

Synopsis

class Functor f where
- fmap :: (a -> b) -> f a -> f b
- (<$) :: a -> f b -> f a
($>) :: Functor f => f a -> b -> f b
(<$>) :: Functor f => (a -> b) -> f a -> f b
void :: Functor f => f a -> f ()

Documentation

class Functor f where Source

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.

Minimal complete definition

fmap

Methods

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

(<$) :: a -> f b -> f a infixl 4 Source

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 STM