"Committed_by_peb"

src/GF/Parsing/ParseMCFG/Basic.hs

@@ -0,0 +1,156 @@
+----------------------------------------------------------------------
+-- |
+-- Module      : MCFParserBasic
+-- Maintainer  : Peter Ljunglöf
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/03/21 22:31:55 $ 
+-- > CVS $Author: peb $
+-- > CVS $Revision: 1.1 $
+--
+-- Simplest possible implementation of MCFG chart parsing
+-----------------------------------------------------------------------------
+
+module GF.Parsing.ParseMCFG.Basic 
+    (parse) where
+
+import Tracing
+
+import Ix
+import GF.Parsing.Utilities
+import GF.Parsing.MCFGrammar
+import GF.Parsing.GeneralChart 
+import GF.Data.Assoc
+import GF.Data.SortedList
+import GF.Printing.PrintParser
+
+
+parse :: (Ord n, Ord c, Ord l, Ord t,
+	  Print n, Print c, Print l, Print t) => 
+	 MCFParser n c l t
+parse grammar start = edges2chart . extract . process grammar 
+
+
+extract :: [Item n c l t] -> [(n, MEdge c l, [MEdge c l])]
+extract items = tracePrt "#passives" (prt.length) $
+		--trace2 "passives" (prtAfter "\n" [ i | i@(PItem _) <- items ]) $
+		[ item | PItem item <- items ]
+
+
+process :: (Ord n, Ord c, Ord l, Ord t, 
+	    Print n, Print c, Print l, Print t) => 
+	   Grammar n c l t -> Input t -> [Item n c l t]
+process grammar input = buildChart keyof rules axioms
+    where axioms = initial
+	  rules  = [combine, scan, predict]
+
+          -- axioms
+	  initial = traceItems "axiom" [] $
+		    [ nextLin name tofind (addNull cat) (map addNull args) |
+		      Rule cat args tofind name <- grammar ]
+
+	  addNull a = (a, [])
+
+	  -- predict 
+	  predict chart i1@(Item name tofind rho (Lin lbl []) (cat, found0) children)
+	      = traceItems "predict" [i1] 
+		[ nextLin name tofind (cat, found) children | 
+		  let found = insertRow lbl rho found0 ]
+	  predict _ _ = []
+
+          -- combine 
+	  combine chart active@(Item _ _ _ (Lin _ (Cat(cat,_,_):_)) _ _)
+	      = do passive <- chartLookup chart (Passive cat)
+		   combineItems active passive
+	  combine chart passive@(PItem (_, (cat, _), _))
+	      = do active <- chartLookup chart (Active cat)
+		   combineItems active passive
+	  combine _ _ = []
+
+          combineItems i1@(Item name tofind rho0 (Lin lbl (Cat(_,lbl',nr):rest)) found children0)
+		       i2@(PItem (_, found', _))
+	      = traceItems "combine" [i1,i2]
+		[ Item name tofind rho (Lin lbl rest) found children |
+		  rho1 <- lookupLbl lbl' found',
+		  let rho = concatRange rho0 rho1,
+		  children <- updateChild nr children0 (snd found') ]
+
+          -- scan
+	  scan chart i1@(Item name tofind rho0 (Lin lbl (Tok tok:rest)) found children)
+	      = traceItems "scan" [i1]
+		[ Item name tofind rho (Lin lbl rest) found children |
+		  let rho = concatRange rho0 (rangeOfToken tok) ]
+	  scan _ _ = []
+
+          -- utilities
+          rangeOfToken tok = makeRange $ inputToken input ? tok
+
+          zeroRange = makeRange $ map (\i -> (i,i)) $ range $ inputBounds input
+
+          nextLin name [] found children = PItem (name, found, children)
+          nextLin name (lin : tofind) found children 
+	      = Item name tofind zeroRange lin found children 
+
+lookupLbl a = map snd . filter (\b -> a == fst b) . snd
+updateChild nr children found = updateIndex nr children $
+				\child -> if null (snd child)
+					     then [ (fst child, found) ]
+					     else [ child | snd child == found ]
+
+insertRow lbl rho [] = [(lbl, rho)]
+insertRow lbl rho rows'@(row@(lbl', rho') : rows)
+    = case compare lbl lbl' of
+        LT -> row : insertRow lbl rho rows
+	GT -> (lbl, rho) : rows'
+	EQ -> (lbl, unionRange rho rho') : rows
+
+
+-- internal representation of parse items
+
+data Item n c l t
+    = Item n [Lin c l t] -- tofind
+      Range (Lin c l t) -- current row
+      (MEdge c l) -- found rows
+      [MEdge c l] -- found children
+    | PItem (n, MEdge c l, [MEdge c l])
+    deriving (Eq, Ord, Show)
+
+data IKey c = Passive c | Active c | AnyItem
+		deriving (Eq, Ord, Show)
+
+keyof (PItem (_, (cat, _), _)) = Passive cat
+keyof (Item _ _ _ (Lin _ (Cat(cat,_,_):_)) _ _) = Active cat
+keyof _ = AnyItem
+
+
+-- tracing
+
+--type TraceItem = Item String String Char String
+traceItems :: (Print n, Print l, Print c, Print t) =>
+	      String -> [Item n c l t] -> [Item n c l t] -> [Item n c l t] 
+traceItems rule trigs items
+    | null items || True = items
+    | otherwise = trace ("\n" ++ rule ++ ":" ++ 
+			 unlines [ "\t" ++ prt i | i <- trigs ] ++ "=>" ++
+			 unlines [ "\t" ++ prt i | i <- items ]) items
+
+-- pretty-printing
+
+instance (Print n, Print c, Print l, Print t) => Print (Item n c l t) where
+    prt (Item name tofind rho lin (cat, found) children)
+	= prt name ++ ". " ++ prt cat ++ prtRhs (map fst children) ++ 
+	  "   { " ++ prt rho ++ prt lin ++ " ; " ++
+	  concat [ prt lbl ++ "=" ++ prt ln ++ " " | 
+		   Lin lbl ln <- tofind ] ++ "; " ++
+	  concat [ prt lbl ++ "=" ++ prt rho ++ " " | 
+		   (lbl, rho) <- found ] ++ "}   " ++
+	  concat [ "[ " ++ concat [ prt lbl ++ "=" ++ prt rho ++ " " | 
+				    (lbl,rho) <- child ] ++ "]   " | 
+		   child <- map snd children ]
+    prt (PItem (name, edge, edges)) 
+	= prt name ++ ". " ++ prt edge ++ prtRhs edges
+
+prtRhs [] = ""
+prtRhs rhs = " -> " ++ prtSep " " rhs
+