Functor
From HaskellWiki
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(Added section "More reading" with a link to "The functor design pattern") |
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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)