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Rufflewind/PeirceLEM.hs

Forked from ion1/PeirceLEM.hs
Created April 7, 2015 09:00
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PierceLEM.hs
-- Exercise: prove Pierce’s law <=> law of excluded middle in Haskell
{-# LANGUAGE Rank2Types #-}
import Data.Void
type Not a = a -> Void
type Pierce = forall a b. ((a -> b) -> a) -> a
type LEM = forall a. Either (Not a) a
callCC_lem :: Pierce -> LEM
callCC_lem callCC = _
lem_callCC :: LEM -> Pierce
lem_callCC lem = _
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