89 lines
3.2 KiB
Haskell
89 lines
3.2 KiB
Haskell
{-# LANGUAGE FlexibleInstances #-}
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module Syndicate.Dataspace.Trie.Prefix where
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-- Alternate representation, where Open has an explicit *arity*
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-- attached to it, and matching close-parens are implicitly tracked.
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-- Where ESOP2016-style implementations have "<xyz>", this style has
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-- "<3xyz".
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import Prelude hiding (null, seq)
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import qualified Data.Map.Strict as Map
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import qualified Data.Set as Set
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data Trie a = Mt
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| Ok a
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| Br (Map.Map Integer (Trie a), Trie a, Map.Map Char (Trie a)) -- Opens, Wild, rest
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deriving (Eq, Show)
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empty = Mt
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null Mt = True
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null _ = False
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makeTail _ r | null r = r
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makeTail 0 r = r
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makeTail n r = Br (Map.empty, makeTail (n - 1) r, Map.empty)
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stripTail _ r | null r = Just r
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stripTail 0 r = Just r
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stripTail n (Br (os, r, h)) | Map.null os && Map.null h = stripTail (n - 1) r
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stripTail _ _ = Nothing
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route _ Mt f = f
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route [] (Ok v) f = v
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route [] _ f = f
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route (_ : _) (Ok v) f = f
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route ('<' : nc : s) (Br (os, w, _)) f =
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let n = (read (nc : []) :: Integer) in
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case Map.lookup n os of
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Just r -> route s r f
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Nothing -> route s (makeTail n w) f
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route (x : s) (Br (_, w, h)) f = route s (Map.findWithDefault w x h) f
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get w h x = Map.findWithDefault w x h
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combine f leftEmpty rightEmpty r1 r2 = g r1 r2
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where g (Ok v) r2 = f (Ok v) r2
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g r1 (Ok v) = f r1 (Ok v)
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g r1 r2 | null r1 = collapse $ leftEmpty r2
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g r1 r2 | null r2 = collapse $ rightEmpty r1
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g r1 r2 = collapse $ foldKeys g r1 r2
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foldKeys g (Br (os1, w1, h1)) (Br (os2, w2, h2)) =
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Br (Set.foldr fo Map.empty sizes, w, Set.foldr f Map.empty keys)
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where sizes = Set.union (Map.keysSet os1) (Map.keysSet os2)
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w = g w1 w2
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fo size acc = let o1 = Map.findWithDefault (makeTail size w1) size os1 in
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let o2 = Map.findWithDefault (makeTail size w2) size os2 in
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let o = g o1 o2 in
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if stripTail size o == Just w then acc else Map.insert size o acc
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f x acc = update x (g (get w1 h1 x) (get w2 h2 x)) w acc
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keys = Set.union (Map.keysSet h1) (Map.keysSet h2)
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collapse (Br (os, Mt, h)) | Map.null os && Map.null h = empty
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collapse r = r
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update x k w h = if k == w then Map.delete x h else Map.insert x k h
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---------------------------------------------------------------------------
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union :: Ord t => Trie (Set.Set t) -> Trie (Set.Set t) -> Trie (Set.Set t)
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union = combine unionCombine id id
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unionCombine (Ok vs) (Ok ws) = Ok (Set.union vs ws)
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unionCombine r1 r2 | null r1 = r2
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unionCombine r1 r2 | null r2 = r1
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unions rs = foldr union empty rs
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intersection :: Ord t => Trie (Set.Set t) -> Trie (Set.Set t) -> Trie (Set.Set t)
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intersection = combine intersectionCombine (const empty) (const empty)
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intersectionCombine (Ok vs) (Ok ws) = Ok (Set.union vs ws)
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intersectionCombine r1 r2 | null r1 = empty
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intersectionCombine r1 r2 | null r2 = empty
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difference :: Ord t => Trie (Set.Set t) -> Trie (Set.Set t) -> Trie (Set.Set t)
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difference = combine differenceCombine (const empty) id
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differenceCombine (Ok vs) (Ok ws) = let xs = Set.difference vs ws in
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if Set.null xs then empty else (Ok xs)
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differenceCombine r1 r2 | null r1 = empty
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differenceCombine r1 r2 | null r2 = r1
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