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cata over Fix.

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Rob Rix 2016-03-18 11:59:54 -04:00
parent 793025e65f
commit ea6fd75131
1 changed files with 3 additions and 0 deletions
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src/Alignment.hs
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@ -108,5 +108,8 @@ type Row a = Both (Line a)
-- | A fixpoint over a functor.
newtype Fix f = Fix { unFix :: f (Fix f) }
cata :: Functor f => (f a -> a) -> Fix f -> a
cata f = f . fmap (Alignment.cata f) . unFix
ana :: Functor f => (a -> f a) -> a -> Fix f
ana f = Fix . fmap (ana f) . f