Changeset 12430 for src/Pugs/Lexer.hs

Timestamp:

08/18/06 22:21:52 (2 years ago)

Author:

audreyt

Message:

* Pugs.Lexer: Another 5% in parsetime shaved by sharing

as much code as possible betwen Pugs.Lexer.symbol's two
branches, and delay evaluation until the match actually
happened (so the result will be on the heap and closer to us.)

Files:

• src/Pugs/Lexer.hs (modified) (1 diff)

src/Pugs/Lexer.hs

@@ -197 +197 @@
 
 symbol :: String -> RuleParser String
-symbol s
-    | isWordAny (last s) = try $ do
-        rv <- string s
-        choice [ eof >> return ' ', lookAhead (satisfy (aheadWord $ last s)) ]
-        whiteSpace
-        return rv
-    | otherwise          = try $ do
-        rv <- string s
-        -- XXX Wrong - the correct solution is to lookahead as much as possible
-        -- in the expression parser below
-        choice [ eof >> return ' ', lookAhead (satisfy (aheadSym $ last s)) ]
-        whiteSpace
-        return rv
+symbol s = try $ do
+    rv <- string s
+    let ahead  = if isWordAny lastCh then aheadWord else aheadSym
+        lastCh = last rv
+    choice [ lookAhead (satisfy (ahead lastCh)), eof >> return ' ' ]
+    whiteSpace
+    return rv
     where
     aheadWord x  '=' = not $ x `elem` "xY\xA5" -- ¥