Coercible.purs

module Coercible where

foreign import unsafeCoerce
  "function unsafeCoerce(x) { return x }" :: forall a b. a -> b

class Coercible a b

coerce :: forall a b. (Coercible a b) => a -> b
coerce = unsafeCoerce

-- Coercible is an equivalence relation
instance reflexiveCoercible :: Coercible a a
instance symmetricCoercible :: (Coercible a b) => Coercible b a
instance transitiveCoercible :: (Coercible a b, Coercible b c) => Coercible a c

instance coercibleF :: (Coercible a b) => Coercible (f a) (f b)