Difference between revisions of "Functor"

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m (Remove Category:Standard classes - now in template)
(Main article in category Functor)
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fmap (p . q) = (fmap p) . (fmap q)
fmap (p . q) = (fmap p) . (fmap q)

Revision as of 21:10, 1 November 2009

Functor class (base)
import Control.Monad

The Functor class is defined like this:

class Functor f where
  fmap :: (a -> b) -> f a -> f b

All instances of Functor should obey:

fmap id = id
fmap (p . q) = (fmap p) . (fmap q)