[antlr-interest] Re: Newbie question (not seeing expected error)

[derek_kusiak]

Thank you very much, Arnar.  So simple I'm embarrassed. :)

--- "Arnar Birgisson" <arnarb at o...> wrote:
> Hello Derek,
> 
> > So far so good.  However, I don't get the expected error
> > if my mistake is in the SECOND sphere:
> > 
> >   sphere 10
> >   20 sphere
> > 
> > Now the first statement is parsed correctly, but there is
> > no error on the second one.  It's just silently ignored
> > and my ouput is this:
> > 
> >   Sphere(radius=10)
> > 
> > Why is there no error about the second sphere?  Clearly the
> > "20 sphere" line is wrong, so why does my parser bail
> > silently after the error?
> 
> After parsing the first line, the parser is at the end of your
> start rule. From there, it doesn't expect to see NUMBER (20) so
> it assumes that it's done parsing and the rest of the input is
> just some garbage (which is sometimes allowed in language
> definitions). This is normal behaviour when you are at the end
> of the start-rule, I think.
> 
> If you want to parse the whole file, you need to add the token
> EOF (end-of-file) to the end of your start rule:
> 
>   class P extends Parser;
>   start  : (shape)+ EOF;
> 
> Given the above example you should get an error in the lines of
> "Unexpected token NUMBER, expecting SPHERE or EOF."
> 
> Hope this helps. :o)
> 
> Arnar








 
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