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semantic/src/Term.hs

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module Term where
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import Data.OrderedMap hiding (size)
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import Data.Maybe
import Control.Comonad.Cofree
import Syntax
type Term a annotation = Cofree (Syntax a) annotation
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zipTerms :: Term a annotation -> Term a annotation -> Maybe (Term a (annotation, annotation))
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zipTerms (annotation1 :< a) (annotation2 :< b) = annotate $ zipUnwrap a b
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where
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annotate = fmap ((annotation1, annotation2) :<)
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zipUnwrap (Leaf _) (Leaf b') = Just $ Leaf b'
zipUnwrap (Indexed a') (Indexed b') = Just . Indexed . catMaybes $ zipWith zipTerms a' b'
zipUnwrap (Fixed a') (Fixed b') = Just . Fixed . catMaybes $ zipWith zipTerms a' b'
zipUnwrap (Keyed a') (Keyed b') | keys a' == keys b' = Just . Keyed . fromList . catMaybes $ zipUnwrapMaps a' b' <$> keys a'
zipUnwrap _ _ = Nothing
zipUnwrapMaps a' b' key = (,) key <$> zipTerms (a' ! key) (b' ! key)
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cata :: (annotation -> Syntax a b -> b) -> Term a annotation -> b
cata f (annotation :< syntax) = f annotation $ cata f <$> syntax
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termSize :: Term a annotation -> Integer
termSize term = cata size term where
size _ (Leaf _) = 1
size _ (Indexed i) = sum i
size _ (Fixed f) = sum f
size _ (Keyed k) = sum $ snd <$> toList k