[Haskell-cafe] Type question re: map
rj248842 at hotmail.com
Fri Mar 6 22:39:46 EST 2009
Given the following (usual) definition of "map":
map :: (a -> b) -> [a] -> [b]
map f  = 
map f (x : xs) = f x : map f xs
What's the type of "map map"?
GHCi's :t command reveals:
*Main> :t map map
map map :: [a -> b] -> [[a] -> [b]]
I'd be grateful if anyone could provide a systematic type calculation so that I can reason through more complicated examples myself.
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