[Haskell-cafe] Why does Data.Map exist when...

16 Jul 2007

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...it seems to be a special case of Set? Does Data.Map add anything more
useful than Map' below?

import Data.Set as Set

newtype MyPair a b = MP (a, b)
  deriving Show

instance (Eq a) => Eq (MyPair a b) where
  MP (a, _) == MP (a', _) = a == a'

instance (Ord a) => Ord (MyPair a b) where
  MP (a, _) `compare` MP(a', _) = a `compare` a'

type Map' k a = Set (MyPair k a)

- --
Tony Morris
http://tmorris.net/

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