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Functor

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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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[[Category:Standard classes]]

Revision as of 04:32, 3 January 2006

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)