1 files changed, 92 insertions, 0 deletions
diff --git a/src/GF/Conversion/RemoveErasing.hs b/src/GF/Conversion/RemoveErasing.hs
new file mode 100644
index 000000000..a7ff2c6df
--- /dev/null
+++ b/src/GF/Conversion/RemoveErasing.hs
@@ -0,0 +1,92 @@
+----------------------------------------------------------------------
+-- |
+-- Maintainer  : PL
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/04/18 14:57:29 $ 
+-- > CVS $Author: peb $
+-- > CVS $Revision: 1.1 $
+--
+-- Removing erasingness from MCFG grammars (as in Ljunglöf 2004, sec 4.5.1)
+-----------------------------------------------------------------------------
+
+
+module GF.Conversion.RemoveErasing
+    (convertGrammar) where
+
+import GF.System.Tracing
+import GF.Infra.Print
+
+import Monad
+import List (mapAccumL)
+import Maybe (mapMaybe)
+import GF.Formalism.Utilities
+import GF.Formalism.GCFG
+import GF.Formalism.MCFG
+import GF.Conversion.Types
+import GF.Data.Assoc
+import GF.Data.SortedList
+import GF.NewParsing.GeneralChart
+
+convertGrammar :: EGrammar -> MGrammar
+convertGrammar grammar
+    = tracePrt "RemoveErasing - nr. nonerasing rules" (prt . length) $
+      traceCalcFirst finalChart $
+      trace2 "RemoveErasing - nr. nonerasing cats" (prt $ length $ chartLookup finalChart False) $
+      trace2 "RemoveErasing - nr. initial ne-cats" (prt $ length initialCats) $
+      trace2 "RemoveErasing - nr. erasing rules" (prt $ length grammar) $
+      newGrammar
+    where newGrammar  = [ rule | NR rule <- chartLookup finalChart True ]
+	  finalChart  = buildChart keyof [newRules rulesByCat] initialCats
+	  initialCats = initialCatsBU rulesByCat
+	  rulesByCat  = accumAssoc id [ (cat, rule) | rule@(Rule (Abs cat _ _) _) <- grammar ]
+
+data Item r c = NR r | NC c deriving (Eq, Ord, Show)
+
+keyof (NR _) = True
+keyof (NC _) = False
+
+newRules grammar chart (NR (Rule (Abs _ cats _) _))
+    = [ NC cat | cat@(MCat _ lbls) <- cats, not (null lbls) ]
+newRules grammar chart (NC newCat@(MCat cat lbls))
+    = do Rule (Abs _ args (Name fun profile)) (Cnc _ _ lins0) <- grammar ? cat
+
+	 let lins = [ lin | lin@(Lin lbl _) <- lins0, 
+		      lbl `elem` lbls ]
+	     argsInLin = listAssoc $
+			 map (\((n,c),l) -> (n, MCat c l)) $
+			 groupPairs $ nubsort $
+			 [ ((nr, cat), lbl) | 
+			   Lin _ lin <- lins, 
+			   Cat (cat, lbl, nr) <- lin ] 
+
+	     newArgs = mapMaybe (lookupAssoc argsInLin) [0 .. length args-1]
+	     argLbls = [ lbls | MCat _ lbls <- newArgs ]
+
+	     newLins = [ Lin lbl newLin | Lin lbl lin <- lins,
+			 let newLin = map (mapSymbol cnvCat id) lin ]
+	     cnvCat (cat, lbl, nr) = (mcat, lbl, nr')
+		 where Just mcat = lookupAssoc argsInLin nr
+		       Unify [nr'] = newProfile !! nr
+	     nonEmptyCat (Cat (MCat _ [], _, _)) = False
+	     nonEmptyCat _ = True
+
+	     newProfile = snd $ mapAccumL accumProf 0 $
+			  map (lookupAssoc argsInLin) [0 .. length args-1]
+	     accumProf nr = maybe (nr, Unify []) $ const (nr+1, Unify [nr])
+	     newName = Name fun (newProfile `composeProfiles` profile)
+
+	 return $ NR (Rule (Abs newCat newArgs newName) (Cnc lbls argLbls newLins))
+
+initialCatsBU grammar 
+    = [ NC (MCat cat [lbl]) | (cat, rules) <- aAssocs grammar, 
+	let Rule _ (Cnc lbls _ _) = head rules,
+	lbl <- lbls ]
+
+
+
+
+
+
+