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liamoc/gist:2972077

Created June 22, 2012 10:56
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Implicit Parameters
Raw
gistfile1.hs
data Eq a = Eq {
eq :: a -> a -> Bool,
neq :: a -> a -> Bool
}
(==) :: (?eq :: Eq a) => a -> a -> Bool
(==) = eq ?eq
(/=) :: (?eq :: Eq a) => a -> a -> Bool
(/=) = neq ?eq
boolEq :: Eq Bool
boolEq = Eq primBoolEq (\x y -> not (primBoolEq x y))
test :: Foo
test = let ?eq = boolEq in True == False
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