Difference between revisions of "Functor"
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BrettGiles (talk | contribs) m (Adding Monad category) |
Artyom Kazak (talk | contribs) m (fix broken link) |
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| − | {{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: |
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class Functor f where |
class Functor f where |
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fmap :: (a -> b) -> f a -> f b |
fmap :: (a -> b) -> f a -> f b |
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| + | |||
| + | It is available in the Prelude, but defined in Data.Functor. |
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All instances of Functor should obey: |
All instances of Functor should obey: |
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| − | fmap id = id |
+ | fmap id = id |
fmap (p . q) = (fmap p) . (fmap q) |
fmap (p . q) = (fmap p) . (fmap q) |
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| + | |||
| ⚫ | |||
| + | == More reading == |
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| − | [[Category:Monad]] |
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| + | |||
| + | * [http://www.haskellforall.com/2012/09/the-functor-design-pattern.html The functor design pattern] |
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| + | |||
| + | |||
| + | |||
| ⚫ | |||
Revision as of 21:14, 13 October 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)