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esoeylemez/NumberDispatch.hs

Last active October 17, 2016 09:00
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NumberDispatch.hs
{-# LANGUAGE AllowAmbiguousTypes #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE RankNTypes #-}
data Number
= DoubleNum !Double
| IntegerNum !Integer
| IntNum !Int
| RationalNum !Rational
withNumber :: (c Double, c Int, c Integer, c Rational) => (forall a. (c a) => a -> r) -> Number -> r
withNumber f (DoubleNum x) = f x
withNumber f (IntegerNum x) = f x
withNumber f (IntNum x) = f x
withNumber f (RationalNum x) = f x
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