With XPath 2 and later, any path expression selecting nodes can have a
last step applying a function returning non-node values so like you can
use e.g.
//date/xs:dateTime(.)
calling `xs:dateTime` for each `date` element selected earlier
you can use
//distinct-values(...)
to apply the distinct-values function for each node selected in the
previous step. As in your example you have used
//distinct-values(//Row[matches(Advertiser, 'TS3', 'i')]/Subscribers)
you compute the sequence several times.
Seehttps://www.w3.org/TR/xpath-31/#id-path-operator for E1/E2
If every evaluation of|E2|returns a (possibly empty) sequence of non-nodes,
these sequences are
concatenated, in order,and returned.Thereturned sequence preserves the
orderings within and among the subsequences generated by the evaluations
of|E2|.
On 08.04.2020 15:12, Costello, Roger L. costello(_at_)mitre(_dot_)org wrote:
Hi Martin,
But, but, but, ...
I thought that // operates on nodes. The distinct-values function doesn't
return nodes, does it? I thought it returns a sequence of strings. If so, then
how can // operate on a sequence of strings?
/Roger
-----Original Message-----
From: Martin Honnen martin(_dot_)honnen(_at_)gmx(_dot_)de
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com>
Sent: Wednesday, April 8, 2020 8:25 AM
To: xsl-list(_at_)lists(_dot_)mulberrytech(_dot_)com
Subject: [EXT] Re: [xsl] What does //distinct-values(...) mean?
Am 08.04.2020 um 14:19 schrieb Costello, Roger L. costello(_at_)mitre(_dot_)org:
Hi Folks,
I executed this XPath query in Oxygen:
//distinct-values(//Row[matches(Advertiser, 'TS3', 'i')]/Subscribers)
The two slashes at the beginning were an accident. At the bottom of the screen
Oxygen shows the matches. All of a sudden it showed 111,000 matches, then a
moment later 438,000 matches, and then finally 525,946 matches.
"Yikes!" I thought, "What is going on? There is supposed to be around 17 matches.
How can there be half a million matches?"
Then I saw the two slashes at the start.
"Hmm, what is the meaning of two slashes preceding the distinct-values
function?" I thought.
So, I ask you: what is the meaning of two slashes preceding the distinct-values
function? Why does its evaluation result in so many matches?
// is short for /descendant-or-self::node()/ so
//distinct-values(//Row[matches(Advertiser, 'TS3', 'i')]/Subscribers)
is
/descendant-or-self::node()/distinct-values(//Row[matches(Advertiser,
'TS3', 'i')]/Subscribers)
meaning it returns
distinct-values(//Row[matches(Advertiser, 'TS3', 'i')]/Subscribers)
as many times as the document has any nodes selectable by
/descendant-or-self::node().
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