Created
April 3, 2019 07:37
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Is List or NonEmpty "simpler"? Neither.
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| -------------------------------------------------------------------------------- | |
| -- Is List or NonEmpty "simpler"? Neither: | |
| type NonEmpty a = Fix (Compose ((,) a) Maybe) | |
| type List a = Fix (Compose Maybe ((,) a)) | |
| -------------------------------------------------------------------------------- | |
| newtype Fix f = Fix {unFix :: f (Fix f)} | |
| newtype Compose f g a = Compose {unCompose :: f (g a)} | |
| instance (Functor f, Functor g) => Functor (Compose f g) where | |
| fmap f = Compose . fmap (fmap f) . unCompose | |
| -------------------------------------------------------------------------------- | |
| ne1, ne2 :: NonEmpty Int | |
| ne1 = Fix (Compose (1, Nothing)) | |
| ne2 = Fix (Compose (1, Just (Fix (Compose (2, Nothing))))) | |
| l0, l1, l2 :: List Int | |
| l0 = Fix (Compose Nothing) | |
| l1 = Fix (Compose (Just (1, Fix (Compose Nothing)))) | |
| l2 = Fix (Compose (Just (1, Fix (Compose (Just (2, Fix (Compose Nothing))))))) |
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