GF/src is now for 2.9, and the new sources are in src-3.0 - keep it this way until the release of GF 3

src-3.0/GF/Parsing/CFG/Incremental.hs

@@ -0,0 +1,150 @@
+----------------------------------------------------------------------
+-- |
+-- Maintainer  : PL
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/04/21 16:23:09 $ 
+-- > CVS $Author: bringert $
+-- > CVS $Revision: 1.4 $
+--
+-- Incremental chart parsing for CFG
+-----------------------------------------------------------------------------
+ 
+
+module GF.Parsing.CFG.Incremental
+    (parse, Strategy) where
+
+import GF.System.Tracing
+import GF.Infra.Print
+
+import Data.Array
+
+import GF.Data.Operations
+import GF.Data.SortedList
+import GF.Data.Assoc
+import GF.Formalism.Utilities
+import GF.Formalism.CFG
+import GF.Parsing.CFG.PInfo
+import GF.Data.IncrementalDeduction
+
+
+-- | parsing strategy: (predict:(BU, TD), filter:(BU, TD))
+type Strategy = ((Bool, Bool), (Bool, Bool))
+
+parse :: (Ord n, Ord c, Ord t) => Strategy -> CFParser c n t
+parse strategy grammar start = extract . 
+			       tracePrt "Parsing.CFG.Incremental - size of internal chart" 
+					    (prt . length . flip chartList const) .
+			       process strategy grammar start
+
+extract :: (Ord n, Ord c, Ord t) => 
+	   IChart c n t -> CFChart c n t
+extract finalChart = [ CFRule (Edge j k cat) daughters name |
+		       (k, Item j (CFRule cat [] name) found) <- chartList finalChart (,),
+		       daughters <- path j k (reverse found) ]
+    where path i k [] = [ [] | i==k ]
+	  path i k (Tok tok : found) 
+	      = [ Tok tok : daughters |
+		  daughters <- path (i+1) k found ]
+	  path i k (Cat cat : found)
+	      = [ Cat (Edge i j cat) : daughters |
+		  Item j _ _ <- chartLookup finalChart i (Passive cat),
+		  daughters <- path j k found ]
+
+process :: (Ord n, Ord c, Ord t) => 
+	   Strategy -> CFPInfo c n t -> [c] -> Input t -> IChart c n t
+process ((isPredictBU, isPredictTD), (isFilterBU, isFilterTD)) grammar start input
+    = trace2 "Parsing.CFG.Incremental - strategy" ((if isPredictBU then "BU-predict " else "") ++
+						   (if isPredictTD then "TD-predict " else "") ++
+						   (if isFilterBU  then "BU-filter " else "") ++
+						   (if isFilterTD  then "TD-filter " else "")) $
+      finalChart
+    where finalChart = buildChart keyof rules axioms $ inputBounds input
+
+          axioms 0 = union $ map (tdInfer 0) start
+	  axioms k = union [ buInfer j k (Tok token) |
+			     (token, js) <- aAssocs (inputTo input ! k), j <- js ]
+
+          rules k (Item j (CFRule cat [] _) _)
+	      = buInfer j k (Cat cat)
+          rules k (Item j rule@(CFRule _ (sym@(Cat next):_) _) found) 
+	      = tdInfer k next <++> 
+	        -- hack for empty rules:
+		[ Item j (forward rule) (sym:found) | 
+		  emptyCategories grammar ?= next ]
+	  rules _ _ = []
+
+          buInfer j k next = buPredict j k next <++> buCombine j k next 
+          tdInfer   k next = tdPredict   k next
+
+	  -- the combine rule
+          buCombine j k next
+	      | j == k    = [] -- hack for empty rules, see rules above and tdPredict below
+	      | otherwise = [ Item i (forward rule) (next:found) | 
+			      Item i rule found <- (finalChart ! j) ? Active next ]
+
+	  -- kilbury bottom-up prediction
+          buPredict j k next
+	      = [ Item j rule [next] | isPredictBU,
+		  rule <- map forward $ bottomupRules grammar ? next,
+		  buFilter rule k, 
+		  tdFilter rule j k ]
+
+	  -- top-down prediction
+          tdPredict k cat
+	      = [ Item k rule [] | isPredictTD || isFilterTD,
+		  rule <- topdownRules grammar ? cat,
+		  buFilter rule k ] <++>
+		-- hack for empty rules:
+		[ Item k rule [] | isPredictBU,
+		  rule <- emptyLeftcornerRules grammar ? cat ]
+
+          -- bottom up filtering: input symbol k can begin the given symbol list (first set)
+	  -- leftcornerTokens DOESN'T WORK WITH EMPTY RULES!!!
+	  buFilter (CFRule _ (Cat cat:_) _) k | isFilterBU
+	      = k < snd (inputBounds input) && 
+		hasCommonElements (leftcornerTokens grammar ? cat) 
+				      (aElems (inputFrom input ! k))
+	  buFilter _ _ = True
+
+          -- top down filtering: 'cat' is reachable by an active edge ending in node j < k
+          tdFilter (CFRule cat _ _) j k | isFilterTD && j < k
+					    = (tdFilters ! j) ?= cat
+	  tdFilter _ _ _ = True
+
+	  tdFilters    = listArray (inputBounds input) $ 
+			 map (listSet . limit leftCats . activeCats) [0..]
+	  activeCats j = [ next | Active (Cat next) <- aElems (finalChart ! j) ]
+	  leftCats cat = [ left | CFRule _cat (Cat left:_) _ <- topdownRules grammar ? cat ]
+
+
+----------------------------------------------------------------------
+-- type declarations, items & keys
+
+data Item c n t = Item Int (CFRule c n t) [Symbol c t]
+		  deriving (Eq, Ord, Show)
+
+data IKey c t = Active (Symbol c t) | Passive c
+		deriving (Eq, Ord, Show)
+
+type IChart c n t = IncrementalChart (Item c n t) (IKey c t) 
+
+keyof :: Item c n t -> IKey c t
+keyof (Item _ (CFRule _ (next:_) _) _) = Active next
+keyof (Item _ (CFRule cat [] _) _)     = Passive cat
+
+forward :: CFRule c n t -> CFRule c n t
+forward (CFRule cat (_:rest) name) = CFRule cat rest name
+
+----------------------------------------------------------------------
+
+instance (Print n, Print c, Print t) => Print (Item c n t) where
+    prt (Item k rule syms) 
+	= "<"++show k++ ": "++ prt rule++" / "++prt syms++">"
+
+instance (Print c, Print t) => Print (IKey c t) where
+    prt (Active sym) = "?" ++ prt sym
+    prt (Passive cat) = "!" ++ prt cat
+
+