Re: Excluding a factor that is not a character set

I mentioned this in a short talk on Direction of ixml at Balisage, 
negations of non-terminals.


 https://cwi.nl/~steven/Talks/2025/08-07-balisage/ixml-directions.html#L142


There are examples of this used in other systems, and it is an issue of 
discussion in the group.


Best wishes,


Steven

On Wednesday 08 October 2025 01:57:18 (+02:00), Sheila Thomson wrote:


Several times I have wanted a factor in a rule to be the exclusion of 
another named rule. A recent example is:

song: ~code, code, line-ending .
@code: -" ", [Lu], [Lu], digit, digit, digit, digit, digit, digit .
-digit: ["0"-"9"] .

Where, above, "~code" is what I would like to be able to write; intending 
to represent everything prior to a substring that matches the code rule.

In the spec I only see information about how to exclude a character set. Is 
there also a way to exclude a pattern of characters, as defined by a named 
rule?

Sheila