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| newtype Maybe' a = Maybe' {getMaybe' :: Maybe a} | |
| deriving Show | |
| -- $setup | |
| -- >>> :set -XScopedTypeVariables | |
| -- >>> :set -XFlexibleContexts | |
| -- >>> import Test.QuickCheck | |
| -- $ | |
| -- | Maybe | |
| -- | |
| -- transitivity test: | |
| -- | |
| -- prop> (\x y z -> (Maybe' x == Maybe' y && Maybe' y == Maybe' z) ==> (Maybe' x == Maybe' z)) | |
| -- | |
| -- above gives me `*** Gave up! Passed only 24 tests; 1000 discarded tests.` | |
| -- | |
| -- Compared to: | |
| -- | |
| -- >>> quickCheck (\x y z -> (Maybe' x == Maybe' y && Maybe' y == Maybe' z) ==> (Maybe' x == Maybe' z)) | |
| -- | |
| -- above gives me `OK, passed 100 tests; 144 discarded.` | |
| -- | |
| instance Eq a => Eq (Maybe' a) where | |
| (Maybe' (Just a)) == (Maybe' (Just a')) = a == a' | |
| (Maybe' Nothing ) == (Maybe' Nothing ) = True | |
| _ == _ = False |
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