Difference between revisions of "Functor"
Jump to navigation
Jump to search
(Added section "More reading" with a link to "The functor design pattern") |
(Updated module.) |
||
| Line 1: | Line 1: | ||
| − | {{Standard class|Functor|module= |
+ | {{Standard class|Functor|module=Data.Functor|module-doc=Data.Functor|package=base}} |
The '''Functor''' class is defined like this: |
The '''Functor''' class is defined like this: |
||
class Functor f where |
class Functor f where |
||
fmap :: (a -> b) -> f a -> f b |
fmap :: (a -> b) -> f a -> f b |
||
| + | |||
| + | It is available in the Prelude, but defined in Data.Functor. |
||
All instances of Functor should obey: |
All instances of Functor should obey: |
||
| − | fmap id = id |
+ | fmap id = id |
fmap (p . q) = (fmap p) . (fmap q) |
fmap (p . q) = (fmap p) . (fmap q) |
||
Revision as of 17:25, 23 August 2014
| import Data.Functor |
The Functor class is defined like this:
class Functor f where fmap :: (a -> b) -> f a -> f b
It is available in the Prelude, but defined in Data.Functor.
All instances of Functor should obey:
fmap id = id fmap (p . q) = (fmap p) . (fmap q)