[antlr-interest] could not even do k=1 for decision 126; reason: timed out

Sam Harwell sharwell at pixelminegames.com
Wed Mar 25 16:10:53 PDT 2009


If you don’t left-factor your rules, it attempts to do so for you. If that process takes longer than the timeout period (default 1 second), it assumes it can’t be done and errors out. Of the two rules below, the former is vastly superior. If you absolutely must use something like the second, at least do this:

 

multiplicativeExpression 

        :       unaryExpression

                (       (STAR^ unaryExpression)*

                |       (DIV^ unaryExpression)*

                |       (MOD^ unaryExpression)*

                )

        ;

 

Also, are you sure you didn’t mean this:

 

multiplicativeExpression 

        :       unaryExpression

                (       STAR^ unaryExpression

                |       DIV^ unaryExpression

                |       MOD^ unaryExpression

                )*

        ;

 

Sam

 

From: antlr-interest-bounces at antlr.org [mailto:antlr-interest-bounces at antlr.org] On Behalf Of YINGAnnie
Sent: Wednesday, March 25, 2009 5:58 PM
To: antlr-interest at antlr.org
Subject: [antlr-interest] could not even do k=1 for decision 126;reason: timed out

 

 
Hi ,
 
 
I have another question about grammar:
 
If I use the following grammar, it works fine.
multiplicativeExpression
   
    :  unaryExpression ((STAR|DIV|MOD)^ u=unaryExpression)*   
    ;
    
But when I change it to 
multiplicativeExpression 
    :  unaryExpression (STAR^ unaryExpression)* 
    |  unaryExpression (DIV^  unaryExpression)* 
    |  unaryExpression (MOD^  unaryExpression)* 
    ;

But I got 
(10): internal error: org.antlr.tool.Grammar.createLookaheadDFA(Grammar.java:1228): could not even do k=1 for decision 126; reason: timed out (>1000ms)
 
It seems the two grammar are the same,I dont know why?
 
Annie

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