Re: [xsl] Each value in an XPath array is a sequence of elements... how to access a particular element in a particular array value?

["Costello, Roger L. costello@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Hi Michael,

That XPath expression yields the empty set.

I created these variables:

<xsl:variable name="first-group" select="$groups[1]" />
<xsl:variable name="Foo-row-first-group" select="($first-group?*)/row[Data eq
'Foo']"/>

And then output the value of the second variable:

<Foo-row-in-first-group>
    <xsl:sequence select="$Foo-row-first-group" />
</Foo-row-in-first-group>

This is the output:

<Foo-row-in-first-group/>

Why does the XPath yield the empty set? Clearly the first group contains a
<row> element with a <Data> element with value 'Foo'. Thoughts?

/Roger


From: Michael Kay mike@xxxxxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Sent: Thursday, June 6, 2019 10:47 AM
To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
Subject: [EXT] Re: [xsl] Each value in an XPath array is a sequence of
elements... how to access a particular element in a particular array value?

$first_group is an array of nodes. To turn it into a sequence of nodes, use
"?*". So it's

($first_group?*)/row

(parentheses because I don't have the operator precedences in my head)

Michael Kay
Saxonica




On 6 Jun 2019, at 15:26, Costello, Roger L. mailto:costello@xxxxxxxxx
<mailto:xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

Hi Folks,

This is an extension to a question that I had last week ...

Recall that I want to group the <row> elements in the following XML. Each
group should consist of those <row> elements that have the same ARPT__IDENT,
TRM__IDENT values.

<Test>
   <row>
       <ARPT__IDENT>A</ARPT__IDENT>
       <TRM__IDENT>X</TRM__IDENT>
       <Data>Foo</Data>
   </row>
   <row>
       <ARPT__IDENT>A</ARPT__IDENT>
       <TRM__IDENT>X</TRM__IDENT>
       <Data>Bar</Data>
   </row>
   <row>
       <ARPT__IDENT>A</ARPT__IDENT>
       <TRM__IDENT>Y</TRM__IDENT>
       <Data>Blah</Data>
   </row>
   <row>
       <ARPT__IDENT>A</ARPT__IDENT>
       <TRM__IDENT>Y</TRM__IDENT>
       <Data>Plugh</Data>
   </row>
</Test>

That XML consists of two groups. Each group has two <row> elements.

Martin provided a great XPath 3.1 expression for doing the grouping:

<xsl:variable name="groups" as="array(element(row))*" select="
   let $keys :=
       distinct-values($rows/concat(ARPT__IDENT, '|', TRM__IDENT))
   return
       for $i in $keys
       return
           array {$rows[$i = concat(ARPT__IDENT, '|', TRM__IDENT)] }
           
   "/>

In the following, I select the first group:

<xsl:variable name="first-group" select="$groups[1]" />

Next, I want to select the <row> element in the first group that has Foo as
the value of the <Data> element. I thought that this would be the appropriate
XPath expression:

<xsl:variable name="Foo-row-first-group" select="$first-group/row[Data eq
'Foo']"/>

Apparently it is not the appropriate XPath expression, because I get this
error message:

	Axis step child::element(Q{}row) cannot
	be used here: the context item is not a node

What is the appropriate XPath expression, please?

/Roger

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