The way the spec is written (I'll go on to the Saxon implementation later) you
shouldn't need to "touch" the elements.
Looking at the draft here:
http://www.w3.org/TR/2013/WD-xslt-30-20131212/
You should be able to do
<xsl:template match="purchase-order">
<Total-Cost>
<xsl:value-of select="accumulator-after('f:item-cost')"/>
</Total-Cost>
</xsl:template>
which is the equivalent of
<xsl:template match="purchase-order">
<Total-Cost>
<xsl:value-of select="f:total-item-cost()"/>
</Total-Cost>
</xsl:template>
in the 2012 draft.
The reason this works is that the xsl:value-of qualifies as both a pre-descent
and a post-descent instruction, because it has no consuming instruction as
either a preceding or a following sibling.
I dare say this almost certainly doesn't work in Saxon 9.5, where as you
suggest you will probably have to inject a consuming instruction into the
template before you can get the post-descent value of the accumulator. You
could for example write <xsl:sequence select="nothing"/>.
Michael Kay
Saxonica
On 12 Dec 2013, at 10:40, Costello, Roger L. <costello(_at_)mitre(_dot_)org>
wrote:
Hi Folks,
Suppose you want to add together all the costs in this purchase order:
<purchase-order>
<item>
<cost>10</cost>
</item>
<item>
<cost>20</cost>
</item>
<item>
<cost>19</cost>
</item>
<item>
<cost>25</cost>
</item>
<item>
<cost>17</cost>
</item>
</purchase-order>
The new XSLT 3.0 accumulator can be used. The accumulator is updated each
time a <cost> element is "touched". To "touch" each <cost> element I have
this empty loop:
<xsl:for-each select="item">
<xsl:for-each select="cost"/>
</xsl:for-each>
That inner loop doesn't need any statements because its sole purpose is
merely to "touch" the cost element, and thereby trigger the accumulator to be
updated.
Here is the XSLT program with the accumulator:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:xs="http://www.w3.org/2001/XMLSchema";
exclude-result-prefixes="#all"
version="3.0">
<xsl:output method="xml" />
<xsl:accumulator name="f:item-cost"
post-descent="f:total-item-cost"
as="xs:integer"
initial-value="0">
<xsl:accumulator-rule match="cost" new-value="$value + xs:integer(.)"/>
</xsl:accumulator>
<xsl:template match="purchase-order">
<Total-Cost>
<xsl:for-each select="item">
<xsl:for-each select="cost"/>
</xsl:for-each>
<xsl:value-of select="f:total-item-cost()" />
</Total-Cost>
</xsl:template>
</xsl:stylesheet>
I realize that this problem could be solved in other ways, but I wanted to
show how it could be solved using an accumulator. And that invariably led me
to an empty xsl:for-each statement.
Is there a better way to "touch" an element than using an empty xsl:for-each
statement?
/Roger
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