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Re: [xsl] XQuery/XPath 3.1: Node List to Node Set ("distinct nodes")

2021-12-29 02:21:55

Am 29.12.2021 um 00:32 schrieb Dimitre Novatchev 
dnovatchev(_at_)gmail(_dot_)com:


On Tue, Dec 28, 2021 at 3:29 PM Dimitre Novatchev
<dnovatchev(_at_)gmail(_dot_)com> wrote:

    A pure XPath solution:

    let $ids := distinct-values($nodes ! generate-id(.))
       return  $ids ! (function($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
is·implementation-dependent·
<https://www.w3.org/TR/xpath-functions/#implementation-dependent>.

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


So while

   $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.
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