mirror of
https://github.com/GrammaticalFramework/gf-core.git
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111 lines
3.6 KiB
Haskell
111 lines
3.6 KiB
Haskell
{-
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**************************************************************
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* Author : Markus Forsberg *
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* markus@cs.chalmers.se *
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**************************************************************
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-}
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module Trie2 (
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tcompile,
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collapse,
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Trie,
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trieLookup,
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decompose,
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--- Attr, atW, atP, atWP,
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emptyTrie
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) where
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import Map
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import List
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newtype TrieT a b = TrieT ([(a,TrieT a b)],[b])
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newtype Trie a b = Trie (Map a (Trie a b), [b])
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emptyTrieT = TrieT ([],[])
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emptyTrie = Trie (empty,[])
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optimize :: (Ord a,Eq b) => TrieT a b -> Trie a b
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optimize (TrieT (xs,res)) = Trie ([(c,optimize t) | (c,t) <- xs] |->+ empty,
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nub res) --- nub by AR
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collapse :: Ord a => Trie a b -> [([a],[b])]
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collapse trie = collapse' trie []
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where collapse' (Trie (map,(x:xs))) s = if (isEmpty map) then [(reverse s,(x:xs))]
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else (reverse s,(x:xs)):
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concat [ collapse' trie (c:s) | (c,trie) <- flatten map]
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collapse' (Trie (map,[])) s
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= concat [ collapse' trie (c:s) | (c,trie) <- flatten map]
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tcompile :: (Ord a,Eq b) => [([a],[b])] -> Trie a b
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tcompile xs = optimize $ build xs emptyTrieT
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build :: Ord a => [([a],[b])] -> TrieT a b -> TrieT a b
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build [] trie = trie
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build (x:xs) trie = build xs (insert x trie)
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where
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insert ([],ys) (TrieT (xs,res)) = TrieT (xs,ys ++ res)
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insert ((s:ss),ys) (TrieT (xs,res))
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= case (span (\(s',_) -> s' /= s) xs) of
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(xs,[]) -> TrieT (((s,(insert (ss,ys) emptyTrieT)):xs),res)
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(xs,(y,trie):zs) -> TrieT (xs ++ ((y,insert (ss,ys) trie):zs),res)
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trieLookup :: Ord a => Trie a b -> [a] -> ([a],[b])
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trieLookup trie s = apply trie s s
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apply :: Ord a => Trie a b -> [a] -> [a] -> ([a],[b])
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apply (Trie (_,res)) [] inp = (inp,res)
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apply (Trie (map,_)) (s:ss) inp
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= case map ! s of
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Just trie -> apply trie ss inp
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Nothing -> (inp,[])
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-----------------------------
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-- from Trie for strings; simplified for GF by making binding always possible (AR)
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decompose :: Ord a => Trie a b -> [a] -> [[a]]
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decompose trie sentence = backtrack [(sentence,[])] trie
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react :: Ord a => [a] -> [[a]] -> [([a],[[a]])] ->
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[a] -> Trie a b -> Trie a b -> [[a]]
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-- String -> [String] -> [(String,[String])] -> String -> Trie -> Trie -> [String]
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react input output back occ (Trie (arcs,res)) init =
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case res of -- Accept = non-empty res.
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[] -> continue back
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_ -> let pushout = (occ:output)
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in case input of
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[] -> reverse $ map reverse pushout
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_ -> let pushback = ((input,pushout):back)
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in continue pushback
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where continue cont = case input of
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[] -> backtrack cont init
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(l:rest) -> case arcs ! l of
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Just trie ->
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react rest output cont (l:occ) trie init
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Nothing -> backtrack cont init
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backtrack :: Ord a => [([a],[[a]])] -> Trie a b -> [[a]]
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backtrack [] _ = []
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backtrack ((input,output):back) trie
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= react input output back [] trie trie
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{- so this is not needed from the original
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type Attr = Int
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atW, atP, atWP :: Attr
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(atW,atP,atWP) = (0,1,2)
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decompose :: Ord a => Trie a (Int,b) -> [a] -> [[a]]
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decompose trie sentence = legal trie $ backtrack [(sentence,[])] trie
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-- The function legal checks if the decomposition is in fact a possible one.
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legal :: Ord a => Trie a (Int,b) -> [[a]] -> [[a]]
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legal _ [] = []
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legal trie input = if (test (map ((map fst).snd.(trieLookup trie)) input)) then input else []
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where
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test [] = False
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test [xs] = elem atW xs || elem atWP xs
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test (xs:xss) = (elem atP xs || elem atWP xs) && test xss
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-}
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