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+----------------------------------------------------------------------
+-- |
+-- Maintainer : PL
+-- Stability : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/05/30 08:11:32 $
+-- > CVS $Author: peb $
+-- > CVS $Revision: 1.3 $
+--
+-- Removing epsilon linearizations from MCF grammars
+-----------------------------------------------------------------------------
+
+
+module GF.Conversion.RemoveEpsilon where
+-- (convertGrammar) where
+
+import GF.System.Tracing
+import GF.Infra.Print
+
+import Control.Monad
+import Data.List (mapAccumL)
+import Data.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.Data.GeneralDeduction
+
+convertGrammar :: EGrammar -> EGrammar
+convertGrammar grammar = trace2 "RemoveEpsilon: initialEmpties" (prt initialEmpties) $
+ trace2 "RemoveEpsilon: emptyCats" (prt emptyCats) $
+ grammar
+ where initialEmpties = nubsort [ (cat, lbl) |
+ Rule (Abs cat _ _) (Cnc _ _ lins) <- grammar,
+ Lin lbl [] <- lins ]
+ emptyCats = limitEmpties initialEmpties
+ limitEmpties es = if es==es' then es else limitEmpties es'
+ where es' = nubsort [ (cat, lbl) | Rule (Abs cat _ _) (Cnc _ _ lins) <- grammar,
+ Lin lbl rhs <- lins,
+ all (symbol (\(c,l,n) -> (c,l) `elem` es) (const False)) rhs ]
+
+
+