Greetings!
On Mon, 2010-08-30 at 13:01 -0700, st3 wrote:
> Hi,
>
> I have a simple grammar - which includes a '+' or '-' operation on a
> variable (ID) or constant (INT).
> The "add" rule is obviously: "mult" (+/- "mult").
>
> However, the way I need the "add" rule defined throws the
> MismatchedTokenException:
> ----------------------------------------------------------------------------
> add : mult
> (
> ('+' mult)
> |
> ('-' mult)
> )*
> ;
>
> while this way to define "add" rule works just fine:
> ----------------------------------------------------------------------------
> add : mult ( ( '+' | '-' ) mult)* ;
>
>
> Can you please give some insights white Antlr 3.0 does not like the first
> way to define "add" rule?
unable to reproduce.
both ways work equally well for me when i run the org.antlr.Tool from
the command line on the Dummy.g grammar you supplied. both get a warning
about no start rule that can end in EOF, but is easily fixed by adding a
rule:
start : expr EOF ;
I am currently using ANTLR 3.1.2 (because I happen to need a python
target) perhaps there is a difference in the versions? (i doubt it)
> The reason I need it this way is to use tree rewrites.
>
> I tried using syntactic predicates but they error out. I have consulted
> Anltr reference book as well - however nothing obvious jumped at me.
>
> Full grammar below.
>
> Thanks a lot for your help!
hope this helps...
-jbb
>
>
>
> grammar Dummy;
>
> expr : add ';' ;
>
> add : mult
> (
> ('+' mult)
> |
> ('-' mult)
> )*
> ;
>
> //add : mult ( ( '+' | '-' ) mult)* ;
>
> mult : constant
> | variable
> | '(' expr ')'
> ;
>
> variable : ID;
> constant : INT;
>
> ID : ('a'..'z'|'A'..'Z') ('a'..'z'|'A'..'Z'|'0'..'9'|'_')* ;
> INT : '0'..'9'+;
> WS : ( ' ' | '\t' | '\r' | '\n' ) { $channel=HIDDEN; } ;
>
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