- From: Steven Pemberton <steven.pemberton@cwi.nl>
- Date: Tue, 03 Feb 2026 13:43:36 +0000
- To: "Norm Tovey-Walsh" <norm@saxonica.com>
- Cc: "Bethan Tovey-Walsh" <bytheway@linguacelta.com>, ixml <public-ixml@w3.org>
The construct A!B only succeeds if A succeeds and B doesn't. Since [] never succeeds, []!digit would never succeed either. The equivalence works though for ()!digit, or ""!digit, or anything else that matches empty. Steven On Tuesday 03 February 2026 13:49:21 (+01:00), Norm Tovey-Walsh wrote: > > One of the use-cases I have for !A is to express maximal length, such as: > > > > number: digit+, !digit. > > I think that’s the same as: > > number: digit+, []!digit . > > I think I want “!” to be a separator at least conceptually. But I concede that “!digit” is a nice shortcut for “[]!digit”. > > Be seeing you, > norm > > -- > Norm Tovey-Walsh > Saxonica >
Received on Tuesday, 3 February 2026 13:43:54 UTC