[antlr-interest] A very simple grammar problem.

[Terence Parr]

Technically not. in 2nd example 'a' can be followed by EOF not in  
first since it's recursive; the warning says it can't decide to  
include EOF.  fi you allowe EOF it's not ambig.
Ter
On Mar 6, 2008, at 9:45 AM, Kenneth Domino wrote:

> Hi,
>
> I seem to be phasing out.  I thought that this grammar should work,  
> but it doesn't:
>
> grammar test_not_ok;
>
> a : 'A' a
>   | 'A'
>   ;
>
> $ java org.antlr.Tool test_not_ok.g
> ANTLR Parser Generator  Version 3.0.1 (August 13, 2007)  1989-2007
> warning(138): test_not_ok.g:0:0: grammar test_not_ok: no start rule  
> (no rule can
>  obviously be followed by EOF)
> warning(201): test_not_ok.g:3:3: The following alternatives are  
> unreachable: 2
>
>
> But, this one works, which specifies the same language if I'm not  
> wrong:
>
> grammar test_ok;
>
> a : b
>   ;
>
> b : 'A' b
>   | 'A'
>   ;
> The only difference is the extra production at the top.
> Do I have to manually augment all my grammars with an EOF rule (S- 
> >... to S' -> S EOF)
> or something else? What am I doing wrong here?
>
> Ken Domino
>

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