Personal tools


From HaskellWiki

(Difference between revisions)
Jump to: navigation, search
(Main article in category Functor)
m (fix broken link)
(2 intermediate revisions by 2 users not shown)

Latest revision as of 21:14, 13 October 2014

Functor class (base)
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)

[edit] More reading