forked from GitHub/gf-core
56 lines
1.8 KiB
Haskell
56 lines
1.8 KiB
Haskell
module GF.Data.TrieMap
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( TrieMap
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, empty
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, singleton
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, lookup
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, null
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, decompose
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, insertWith
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, unionWith
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) where
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import Prelude hiding (lookup, null)
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import qualified Data.Map as Map
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data TrieMap k v = Tr (Maybe v) (Map.Map k (TrieMap k v))
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empty = Tr Nothing Map.empty
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singleton :: [k] -> a -> TrieMap k a
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singleton [] v = Tr (Just v) Map.empty
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singleton (k:ks) v = Tr Nothing (Map.singleton k (singleton ks v))
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lookup :: Ord k => [k] -> TrieMap k a -> Maybe a
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lookup [] (Tr mb_v m) = mb_v
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lookup (k:ks) (Tr mb_v m) = Map.lookup k m >>= lookup ks
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null :: TrieMap k v -> Bool
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null (Tr Nothing m) = Map.null m
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null _ = False
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decompose :: TrieMap k v -> (Maybe v, Map.Map k (TrieMap k v))
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decompose (Tr mb_v m) = (mb_v,m)
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insertWith :: Ord k => (v -> v -> v) -> [k] -> v -> TrieMap k v -> TrieMap k v
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insertWith f [] v0 (Tr mb_v m) = case mb_v of
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Just v -> Tr (Just (f v0 v)) m
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Nothing -> Tr (Just v0 ) m
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insertWith f (k:ks) v0 (Tr mb_v m) = case Map.lookup k m of
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Nothing -> Tr mb_v (Map.insert k (singleton ks v0) m)
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Just tr -> Tr mb_v (Map.insert k (insertWith f ks v0 tr) m)
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unionWith :: Ord k => (v -> v -> v) -> TrieMap k v -> TrieMap k v -> TrieMap k v
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unionWith f (Tr mb_v1 m1) (Tr mb_v2 m2) =
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let mb_v = case (mb_v1,mb_v2) of
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(Nothing,Nothing) -> Nothing
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(Just v ,Nothing) -> Just v
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(Nothing,Just v ) -> Just v
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(Just v1,Just v2) -> Just (f v1 v2)
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m = Map.unionWith (unionWith f) m1 m2
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in Tr mb_v m
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