Functor
From HaskellWiki
(Difference between revisions)
(Added section "More reading" with a link to "The functor design pattern") |
(Updated module.) |
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− | {{Standard class|Functor|module=Control.Monad|module-doc=Control-Monad|package=base}} |
+ | {{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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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)