Fixed some bugs in the Graphviz printer.

src/GF/Visualization/Graphviz.hs

@@ -5,9 +5,9 @@
 -- Stability   : (stable)
 -- Portability : (portable)
 --
--- > CVS $Date: 2005/09/14 15:17:30 $ 
+-- > CVS $Date: 2005/09/15 18:10:44 $ 
 -- > CVS $Author: bringert $
--- > CVS $Revision: 1.1 $
+-- > CVS $Revision: 1.2 $
 --
 -- Graphviz DOT format representation and printing.
 -----------------------------------------------------------------------------
@@ -19,6 +19,8 @@ module GF.Visualization.Graphviz (
 				  prGraphviz
 			) where
 
+import Data.Char
+
 import GF.Data.Utilities
 
 data Graph = Graph GraphType [Attr] [Node] [Edge]
@@ -51,18 +53,29 @@ prNode :: Node -> String
 prNode (Node n at) = esc n ++ " " ++ prAttrList at
 
 prEdge :: GraphType -> Edge -> String
-prEdge t (Edge x y at) = esc x ++ " " ++ edgeop t ++ " " ++ prAttrList at
+prEdge t (Edge x y at) = esc x ++ " " ++ edgeop t ++ " " ++ esc y ++ " " ++ prAttrList at
 
 edgeop :: GraphType -> String
 edgeop Directed = "->"
 edgeop Undirected = "--"
 
 prAttrList :: [Attr] -> String
-prAttrList = join "," . map prAttr
+prAttrList [] = ""
+prAttrList at =	"[" ++ join "," (map prAttr at) ++ "]"
 
 prAttr :: Attr -> String
 prAttr (n,v) = esc n ++ " = " ++ esc v
 
 esc :: String -> String
-esc s = "\"" ++ concat [ if shouldEsc c then ['\\',c] else [c] | c <- s ] ++ "\""
-  where shouldEsc = (`elem` ['"', '\\'])
+esc s | needEsc s = "\"" ++ concat [ if shouldEsc c then ['\\',c] else [c] | c <- s ] ++ "\""
+      | otherwise = s
+  where shouldEsc = (`elem` ['"', '\\'])
+
+needEsc :: String -> Bool
+needEsc [] = True
+needEsc xs | all isDigit xs = False
+needEsc (x:xs) = not (isIDFirst x && all isIDChar xs)
+
+isIDFirst, isIDChar :: Char -> Bool
+isIDFirst c = c `elem` (['_']++['a'..'z']++['A'..'Z'])
+isIDChar c = isIDFirst c || isDigit c