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module VerifiedOption | |
import Classes.Verified | |
-- data Maybe a = Just a | Nothing | |
data Option a = Some a | None | |
-- Associativity | |
-- (a <+> b) <+> c = a <+> (b <+> c) | |
instance Semigroup a => Semigroup (Option a) where | |
(Some a) <+> (Some b) = Some (a <+> b) | |
None <+> a = a | |
a <+> b = a | |
-- Identity laws | |
-- neutral <+> a = a | |
-- a <+> neutral = a | |
instance Semigroup a => Monoid (Option a) where | |
neutral = None | |
-- Verify | |
instance VerifiedSemigroup a => VerifiedSemigroup (Option a) where | |
semigroupOpIsAssociative (Some a) (Some b) (Some c) = ?someSomeSome | |
semigroupOpIsAssociative (Some _) (Some _) None = Refl | |
semigroupOpIsAssociative (Some _) None _ = Refl | |
semigroupOpIsAssociative None _ _ = Refl | |
instance VerifiedSemigroup a => VerifiedMonoid (Option a) where | |
monoidNeutralIsNeutralL (Some _) = Refl | |
monoidNeutralIsNeutralL None = Refl | |
monoidNeutralIsNeutralR (Some _) = Refl | |
monoidNeutralIsNeutralR None = Refl | |
---------- Proofs ---------- | |
someSomeSome = proof | |
intros | |
rewrite (semigroupOpIsAssociative a b c) | |
trivial |
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Is
rewrite
still a thing in interactive proof mode?