Re: best grammar for handling optional symbols?

> If you are fortunate enough to use EBNF, but again have a required
> fixed order, the clutziness would go away. You could just write the
> 18 options out with each in brackets or followed by a question mark,
> and life would be good. Or to adopt John's phrase, you would have
> kept your grammar manageable.
>
> But nothing like that is possible if the order is variable. In that
> case, even if you are writing for humans, your best bet is to escape
> from the BNF or EBNF into some more general means of communication --
> which for a human, might well be a natural-language explanation.
>
> -Max Hailperin
> Professor of Computer Science
> Gustavus Adolphus College


I did not know about following an optional symbol with ? but I did
miss in wikipedia where they surround optionals with [].
My options, as far as I can tell from the reference, are in a sequence
- fortunately for me - I think.
otherwise I would write it as
<option> := "a" | "b" | "c" | "d" "e" | "f"
<sequence> ::= <option>*


I guess this means I am going to have to "look ahead"

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