[antlr-interest] Interpreter output inconsistent for "C stylemethod calls"

[Thomas Brandon]

On 7/26/07, Buck, Robert <rbuck at verisign.com> wrote:
> This turns out to be a UI interpreter bug. When I run it through the
> debugger, it displays consistently.
>
> Bob
>
> > -----Original Message-----
> > From: antlr-interest-bounces at antlr.org
> > [mailto:antlr-interest-bounces at antlr.org] On Behalf Of Buck, Robert
> > Sent: Wednesday, July 25, 2007 9:56 AM
> > To: antlr-interest at antlr.org
> > Subject: [antlr-interest] Interpreter output inconsistent for
> > "C stylemethod calls"
> >
> > Given something like this:
> >
> >    MODULUS(16, FIRST_N_CHARACTERS(5, TO_ADDR()))
> >
> >
> > And running it through the interpreter using this grammar:
> >
> > grammar test;
> > method
> >       :       ID arguments
> >       ;
> > expression
> >       :       method
> >       |       literal
> >       ;
> > literal
> >       :       STRING
> >       |       INT
> >       ;
> > arguments
> >       :       LPAREN (argumentList)? RPAREN
> >       ;
> > argumentList
> >       :       expression (',' expression)*
> >       ;
> > LPAREN        :       '(';
> > RPAREN        :       ')';
> > ID  :   ('_'|'a'..'z'|'A'..'Z') ('_'|'a'..'z'|'A'..'Z'|'0'..'9')* ;
> > STRING : '"' .* '"' ;
> > INT :   '0'..'9'+ ;
> >
> >
> > When I compare the results of running the expression through
> > 'method', and through 'expression, I get different results:
> >
> > > expression method MODULUS arguments ( argumentList
> > expression literal
> > 16
> >
> > > method MODULUS arguments ( argumentList expression literal 16 ,
> > expression method FIRST_N_CHARACTERS arguments
> >     ( argumentList expression literal 5 , expression method
> > TO_ADDR arguments ( )
> >
> > Now, as both have as a stem in their output 'method', I do
> > not quite understand why the interpreter produces different
> > results in each case.
> >
> > Am I missing something here?
The interpreter shows a parse tree, showing all rules that were used
to parse the output, not the AST. If you look at the Parse Tree in the
debugger you should see something similar to the interpreter with the
different start rule producing a different parse tree. If you look at
the AST in the debugger then the output will be the same for both
start rules.

Tom.
> >
> > Bob
> >
> >
>