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maoe/ScopedTypeVars.hs

Created August 26, 2011 10:11
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Scoped type variablesが必要になる例
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ScopedTypeVars.hs
{-# LANGUAGE ScopedTypeVariables #-}
module ScopedTypeVars where
bounds :: forall a. (Show a, Bounded a) => a -> (String, String)
bounds x = (minBoundS, maxBoundS)
where
minBoundS = show (minBound :: a)
maxBoundS = show (maxBound :: a)
bounds' :: (Show a, Bounded a) => a -> (String, String)
bounds' x = (minBoundS, maxBoundS)
where
minBoundS = show (minBound `asTypeOf` x)
maxBoundS = show (maxBound `asTypeOf` x)
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