Re: XQuery/XPath 3.1: Node List to Node Set ("distinct

Am 29.12.2021 um 00:32 schrieb Dimitre Novatchev dnovatchev@xxxxxxxxx:
>
>
> On Tue, Dec 28, 2021 at 3:29 PM Dimitre Novatchev
> <dnovatchev@xxxxxxxxx> wrote:
>
>     A pure XPath solution:
>
>     let $ids := distinct-values($nodes ! generate-id(.))
>     B  B return B $ids ! (function($id) {$nodes[generate-id(.) eq
>     $id][1]})(.)
>
>     Happy New Year to all !
>
>
>
> Hit Send too early:
>
> Do notice: this seems the only solution of all presented so far, that
> preserves the original sequence order (not document order) of the nodes.

Why is the original sequence order preserved?
https://www.w3.org/TR/xpath-functions/#func-distinct-values clearly says

"The function returns the sequence that results from removing
from|$arg|all but one of a set of values that are considered equal to
one another. [...]

The order in which the sequence of values is returned
isB7implementation-dependentB7
<https://www.w3.org/TR/xpath-functions/#implementation-dependent>.

Which value of a set of values that compare equal is returned
isB7implementation-dependentB7
<https://www.w3.org/TR/xpath-functions/#implementation-dependent>."


So while

 B B  $nodes ! generate-id(.)

gives you the generated ids in the order of the nodes in $nodes after
the call to distinct-values there is no order defined, it is
implementation dependent.