On Mon, Jun 10, 2013 at 2:13 AM, Frantisek Sodomka <fsodo...@gmail.com>wrote:

> EBNF syntax for bounded repetition could be just simply A 3*5 and these
> are equal:
> A? is A*1
> A+ is A1*
> A* is A0*
>

Right now, in the EBNF syntax, numbers are valid non-terminal identifiers.
So for example, rather than "S = A B+", you could do "1 = 2 3+".  I thought
this might be useful for programmatically generated grammars.  Adding a
bounded repetition operator to EBNF is certainly possible, but the most
obvious syntaxes would eliminate the use of numbers as identifiers.

Have you actually encountered a real example where you wished for the large
bounded repetition, or is this just a theoretical question?  Even in the
ABNF examples I've seen (which has the bounded repetition option), most
instances of repetition correspond to the standard + * and ? operators.

 I've seen the exception operator listed on a couple of tables, but have
never seen it in use, and didn't come across a clear explanation of its
semantics.  Can you point me to a fuller description of what it does?

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