From: Michael Neumann <neumann@...>
Date: 2001-04-18T06:21:38+09:00
Subject: [ruby-talk:13775] Problems with racc rule definitions


Hi,

Following racc-rule raises an error during parsing (not during 'racc parser.y'), 
and I don't know why.

It seems to me that racc is very limited. * and ? would be nice :)



NodeType can be 'comment', 'text', 'processing-instruction' or 'node'.

######

 token NameTest NodeType Literal 

 rule

 NodeTest : NameTest 
         | 'processing-instruction' '(' Literal ')' 
         | NodeType '(' ')' 
         ;
 end

#######

My first thought was that the error is raised because NodeType 
contains "processing-instruction'. 
But if the error is also there if I write:

 NodeTest : NameTest 
         | 'processing-instruction' '(' Literal ')' 
         | 'comment'  '(' ')' 
         | 'text'  '(' ')' 
         | 'node'  '(' ')' 
         ;

The solution I've found, which works is the following:

 NodeTest : NameTest 
          | NodeType '(' Literal ')' 
          { 
           if val[0] != "processing-instruction" then
             yyerror
             raise ArgumentError, "yyerror failed" 
           else
             puts "ok" 
           end
          }

          | NodeType '(' ')' 
          { 
           if val[0] == "processing-instruction" then
             yyerror
             raise ArgumentError, "yyerror failed" 
           else
             puts "ok" 
           end
 
          }
          ;

 ####


Is there another way to do it more elegant?




Thanks in advance.


Regards

Michael



-- 
Michael Neumann
merlin.zwo InfoDesign GmbH
http://www.merlin-zwo.de