Re: problem with very simple gramma

[Hans Aberg]

On 1 Dec 2007, at 23:07, Natalia Wolyczko wrote:

> I'm new to bison, first of all I've tried to write a simple "hello- 
> world" like program using flex/bison.
> All I want is to see "boom!" message after reading two MLAH tokens,  
> which corresponds to input string of the same name i.e. "mlah".
>
> This works fine, I'm able to see "boom!" message after typing mlah  
> twice, the things which I really don't get is why I see "syntax  
> errror" once mlah is entered third time? What I expected is the  
> situation in which I see "boom!" every two "mlah" occurences.
> Can anybody please explain me what's going on?

Because you have written the grammar for a language matching exactly  
that token sequence and nothing else. If you want to do what you  
indicated, you need to do recursion - the Bison manual has some  
sections on that. Also, check out the calculator example - good  
starting point.

  Hans Aberg