Re: String complements

> Enjoy some bedtime reading: http://www.unicode.org/reports/tr10/

Thank you, Michael, this would make an interesting read, indeed.

> We do offer a function fn:collation-key() which, given a string and a
collation,
> returns a binary value such that the ordering of the binary values
corresponds to the order of strings in the collation.
> This functionality is very important when delivering things like
distinct-values or for-each-group using an arbitrary collation;
> it can also be used to construct keys for maps.

Yes, I already looked at this, and this is nice compared to having no such
function at all, but one must:


   1. Know which are all the different characters (symbols) to ask for.

   2. How to know that he has asked for all characters/symbols in the
   collation.

Reconstructing this by assembling the results of a series of calls to
fn:collation-key() is closer to detective or archaeologist work than of a
software developer's work.

Why has SQL Server provided such facilities to all of its users (factors of
magnitude more than the X* technologies users) but we have no such
functionality?

Thanks,
Dimitre

On Fri, Mar 15, 2024 at 11:41 AM Michael Kay <mike@saxonica.com> wrote:

>
> 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.
>
>
> Collations don't work character-by-character. Firstly, they split a string
> into "collation elements" (or collation units) which may contain several
> characters, and secondly, they work in a number of passes, sorting first by
> the primary weights of each collation unit, then the secondary weights, etc.
>
> Enjoy some bedtime reading: http://www.unicode.org/reports/tr10/
>
> We do offer a function fn:collation-key() which, given a string and a
> collation, returns a binary value such that the ordering of the binary
> values corresponds to the order of strings in the collation. This
> functionality is very important when delivering things like distinct-values
> or for-each-group using an arbitrary collation; it can also be used to
> construct keys for maps.
>
> Michael Kay
>
>