[antlr-interest] Grammar Problem

[Henrique]

Hi guys!
I'm having some trouble with my grammar for parsing CFA files... As I posted
before, I'm trying to convert their Yacc grammar to ANTLR and now I'm having
some trouble. I suspect it's the left recursions or rather the way I got
ridden of them.
The grammar is attached and can also be seen
here<http://hjrnunes.googlepages.com/antlrgrammar>
.

here's the rules I'm having trouble with:

rule    :    RULE USER_STRING LEFTBRACKET buncha_replacements? RIGHTBRACKET
    |    RULE USER_STRING USER_RATIONAL LEFTBRACKET buncha_replacements?
RIGHTBRACKET
    ;

buncha_replacements
    :    (replacement)+
    ;

replacement
    :    USER_STRING modification
    |    USER_STRING STAR modification USER_STRING modification
    ;

Here's an example of what it should parse:

rule Foo {
    CIRCLE { b 1 }
    CIRCLE {}
}

Now I'm getting a MismatchedTokenException: mismatched input 'CIRCLE'
expecting RIGHTBRACKET in the first alternative.
Here are the relevant original YACC rules:

rule:
        RULE USER_STRING LEFTBRACKET buncha_replacements RIGHTBRACKET
        |
        RULE USER_STRING USER_RATIONAL LEFTBRACKET buncha_replacements
RIGHTBRACKET
        ;

buncha_replacements:
        buncha_replacements replacement
        |
        ;

The strange thing - at least for me is that the background rule that is
quite similar works like a charm:

background
    :    BACKGROUND LEFTBRACKET buncha_color_adjustments? RIGHTBRACKET
    ;

buncha_color_adjustments
    :    (color_adjustment)+
    ;

It should work almost similarly...
What would be the right way to convert such left recursive rules into
something appropriate for ANTLR?
I hope you guys can shed some insight on this... I'm somewhat of a newbie
concerning parsing and ANTLR.
Thanks!

Henrique Nunes
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