- From: John Lumley <john@saxonica.com>
- Date: Sat, 18 Dec 2021 15:49:17 +0000
- To: Dave Pawson <dave.pawson@gmail.com>
- Cc: Steven Pemberton <steven.pemberton@cwi.nl>, "C. M. Sperberg-McQueen" <cmsmcq@blackmesatech.com>, Norm Tovey-Walsh <norm@saxonica.com>, ixml <public-ixml@w3.org>
I don’t know whether it will help but consider the issue of the ‘empty string “”… It really is a string, but has no characters in it, but isn’t an empty sequence…. Similarly one might consider the xs:integer 0 to be an integer which has ‘nothing’ as its value. The difference between [] and () are similar…. Sent from my iPad > On 18 Dec 2021, at 08:42, Dave Pawson <dave.pawson@gmail.com> wrote: > > I find this very confusing. > Empty set > Empty string > 'nothing' > > I doubt if I will be the only user to take this view. > > I'll shut up now. > > regards > >> On Fri, 17 Dec 2021 at 20:19, Steven Pemberton <steven.pemberton@cwi.nl> wrote: >> >>>> - An alternative that matches no sequences at all, which no thing >>>> matches. This is an expression which denotes the language with >>>> no sentences, i.e. the empty set. And this is the meaning most >>>> naturally associated with the symbol “∅”. >>> >>> Any reason why [] should not be given this definition? >> >> It does have that definition, but that is a different definition to what you require. >> >> () matches the empty string, so always succeeds. >> [] matches *nothing at all*, so always fails. >> >> Steven > > > > -- > Dave Pawson > XSLT XSL-FO FAQ. > Docbook FAQ. >
Received on Saturday, 18 December 2021 15:49:34 UTC