Re: String complements

Before requesting new functions, we should clarify if there’s a problem to solve – or, in other words, if at least 2, 3 people believe there's a problem.


Am 15.03.2024 19:25 schrieb Dimitre Novatchev <dnovatchev@gmail.com>:
> > Seems to work like a charm 😀
>
>   Doesn’t blindly subtracting the code point for 0x110000 run the risk of producing a non-Unicode character?
> I think the original code point would have to be in…checks notes…plane 16, so fairly unlikely, but still…

I think there is a more important question: Will this work correctly with collations that are not Binary (that means that cp1 > cp2 doesn't guarantee that in this collation Char(cp1) > Char(cp2) ).

The answer is no - and we have too-many collations (like any CI (case-insensitive) collation) in which 'X' and 'x' are consecutive in the sorted character set of this collation.

When sorting using a collation, we must use not the codepoint for a character, but its index in the sorted characters of this collation.

This is why it is important to have a function

    fn:collation-characters($collation-name as xs:string) as xs:string

that returns the sorted (according to this collation) individual characters of the collation.

Not to mention that the user, before specifying a collation name to one of the variety of functions that take collations as parameters, needs to be well-informed of exactly which characters are in this collation.

At present we don't have such a function, and it would  really be very useful to have a function like this.


Thanks,
Dimitre

On Fri, Mar 15, 2024 at 5:42 AM Norm Tovey-Walsh <norm@saxonica.com<mailto:norm@saxonica.com>> wrote:
Dimitre Novatchev <dnovatchev@gmail.com<mailto:dnovatchev@gmail.com>> writes:
> Seems to work like a charm 😀

Doesn’t blindly subtracting the code point for 0x110000 run the risk of producing a non-Unicode character? I think the original code point would have to be in…checks notes…plane 16, so fairly unlikely, but still…

                                        Be seeing you,
                                          norm

--
Norm Tovey-Walsh
Saxonica