99 lines
3.0 KiB
Haskell
99 lines
3.0 KiB
Haskell
module Syndicate.Dataspace.Trie.ESOP2016v2 where
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-- Close to the ESOP 2016 implementation of dataspace tries, but takes
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-- a step toward efficiency by using collapse/update instead of dedup/distinct.
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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 Sigma = Open
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| Close
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| Wild
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| Ch Char
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deriving (Eq, Ord, Show)
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data Trie a = Ok a
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| Tl (Trie a)
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| Br (Map.Map Sigma (Trie a))
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deriving (Eq, Show)
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empty = Br Map.empty
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null (Br h) = Map.null h
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null _ = False
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tl r = if null r then empty else Tl r
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untl (Tl r) = r
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untl _ = empty
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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 (x : s) (Br h) f = if Map.null h
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then f
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else route s (get h x) f
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route (Close : s) (Tl r) f = route s r f
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route (Open : s) (Tl r) f = route s (tl (tl r)) f
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route (x : s) (Tl r) f = route s (tl r) f
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get h x = case Map.lookup x h of
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Just r -> r
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Nothing -> case x of
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Open -> tl (get h Wild)
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Close -> untl (get h Wild)
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Wild -> empty
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x -> get h Wild
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combine r1 r2 f leftEmpty rightEmpty = g r1 r2
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where g (Tl r1) (Tl r2) = tl (g r1 r2)
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g (Tl r1) r2 = g (expand r1) r2
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g r1 (Tl r2) = g r1 (expand r2)
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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 (Br h1) (Br h2) = collapse $ Br (foldKeys g h1 h2)
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foldKeys g h1 h2 = Set.foldr f Map.empty keys
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where f x acc = update x (g (get h1 x) (get h2 x)) acc
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keys = Set.union (Map.keysSet h1) (Map.keysSet h2)
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expand r = Br (Map.fromList [(Wild, tl r), (Close, r)])
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collapse (Br h) = if Map.size h == 2
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then case (Map.lookup Wild h, Map.lookup Close h) of
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(Just (w @ (Tl k1)), Just k2) | k1 == k2 -> w
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_ -> Br h
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else if Map.size h == 1
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then case Map.lookup Wild h of
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Just (w @ (Tl _)) -> w
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_ -> Br h
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else Br h
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update Wild k h =
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if null k
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then Map.delete Wild h
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else Map.insert Wild k h
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update Open (Tl k) h =
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case Map.lookup Wild h of
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Just k' | k' == k -> Map.delete Open h
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_ -> Map.insert Open (Tl k) h
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update Close k h =
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case Map.lookup Wild h of
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Just (Tl k') | k' == k -> Map.delete Close h
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_ -> Map.insert Close k h
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update x k h =
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case Map.lookup Wild h of
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Just k' | k' == k -> Map.delete x h
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_ -> Map.insert x k h
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---------------------------------------------------------------------------
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union r1 r2 = combine r1 r2 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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