From: puellula@...
Date: 2005-10-28T18:17:04+09:00
Subject: PARSER for RUBY

Hi,
can you help me?
I have to write a parser for Ruby. I had think to use the parser
generator ANTLR.
I have find Ruby Grammar, but I have problem with ANTLR for "infinite
recursion". I have cancel left recursion but I have the same problem :(

Please, can you help me?
Now I'm trying with a simple grammar to find where is the problem. The
simple grammar is:


// PARSER
class RubyParser extends Parser;
options { buildAST=true; }


program         : compstmt;
compstmt        : stmt;
stmt            : stmt1 expr
                | ;
stmt1           : stmt IF
                | stmt WHILE
                | stmt UNLESS
                | stmt UNTIL
                | ;
expr            : ;


// LEXER
class RubyLexer extends Lexer;
IF : "if";
WHILE : "while";
UNLESS : "unless";
UNTIL : "until";


I have write this on a file provaLexerParser.g
On the command line I have write:


antlr provaLexerParser.g


and the result is:


java -classpath "C:\antlr\275\lib\antlr.jar;" antlr.Tool
provaLexerParser.g
ANTLR Parser Generator   Version 2.7.5 (20050128)   1989-2005 jGuru.com

provaLexerParser.g:7:19: infinite recursion to rule stmt1 from rule
stmt
provaLexerParser.g:9:19: infinite recursion to rule stmt1 from rule
stmt1
provaLexerParser.g:10:19: infinite recursion to rule stmt1 from rule
stmt1
provaLexerParser.g:11:19: infinite recursion to rule stmt1 from rule
stmt1
provaLexerParser.g:12:19: infinite recursion to rule stmt1 from rule
stmt1
provaLexerParser.g:7:19: infinite recursion to rule stmt1 from rule
stmt
provaLexerParser.g:7: warning:nondeterminism between alts 1 and 2 of
block upon
provaLexerParser.g:7:     k==1:EOF,IF,WHILE,UNLESS,UNTIL
Exiting due to errors.


Plase, I need help. 


Thank you for all! 


bye, 
puellula