"Committed_by_peb"

src/GF/Formalism/CFG.hs

@@ -0,0 +1,50 @@
+----------------------------------------------------------------------
+-- |
+-- Maintainer  : PL
+-- Stability   : (stable)
+-- Portability : (portable)
+--
+-- > CVS $Date: 2005/04/11 13:52:49 $ 
+-- > CVS $Author: peb $
+-- > CVS $Revision: 1.1 $
+--
+-- CFG formalism
+-----------------------------------------------------------------------------
+
+module GF.Formalism.CFG where
+
+import GF.Formalism.Utilities
+import GF.Infra.Print
+import GF.Data.Assoc (accumAssoc)
+import GF.Data.SortedList (groupPairs)
+import GF.Data.Utilities (mapSnd)
+
+------------------------------------------------------------
+-- type definitions
+
+type CFGrammar  c n t = [CFRule c n t]
+data CFRule     c n t = CFRule c [Symbol c t] n
+			deriving (Eq, Ord, Show)
+
+type CFChart    c n t = CFGrammar (Edge c) n t
+
+
+------------------------------------------------------------
+-- building syntax charts from grammars
+
+grammar2chart :: (Ord n, Ord e) => CFGrammar e n t -> SyntaxChart n e
+grammar2chart cfchart = accumAssoc groupPairs $
+			[ (lhs, (name, filterCats rhs)) |
+				     CFRule lhs rhs name <- cfchart ]
+
+
+----------------------------------------------------------------------
+-- pretty-printing
+
+instance (Print n, Print c, Print t) => Print (CFRule c n t) where
+    prt (CFRule cat rhs name) = prt name ++ " : " ++ prt cat ++ 
+				( if null rhs then "" 
+				  else " --> " ++ prtSep " " rhs )
+    prtList = prtSep "\n"
+
+