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Re: [xsl] accumulators


Subject: Re: [xsl] accumulators
From: Michael Kay <mike@xxxxxxxxxxxx>
Date: Sat, 20 Apr 2013 17:41:09 +0100

Like xsl:key, accumulators apply to every document, but when you evaluate the
accumulator function, you get the value applicable to the context node. In all
your calls of the accumulator function, the context node is the root of the
principal source document.

Accumulators are strictly functional: the value is a function of the context
node. If you call the function twice and the context node is the same for both
calls, you will get the same answer.

Michael Kay
Saxonica


On 19 Apr 2013, at 22:04, Jakub Mal} wrote:

> Hi,
> I am fiddling with XSLT accumulators in the new version of Saxon.
> I first looked at the examples in the spec and thought that this might work
> (and output 01210), but it doesn't:
>
> <?xml version="1.0" encoding="UTF-8"?>
>
> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
> 	xmlns:f="myf"	version="3.0">
>
> 	<xsl:accumulator name="f:my-var" as="xs:integer" initial-value="0" >
> 		<xsl:accumulator-rule match="f:inc" new-value="$value + 1"/>
> 		<xsl:accumulator-rule match="f:dec" new-value="$value - 1"/>
> 	</xsl:accumulator>
>
> 	<xsl:variable name="f:control-inc" as="element()*">
> 		<f:inc/>
> 	</xsl:variable>
> 	<xsl:variable name="f:control-dec" as="element()*">
> 		<f:dec/>
> 	</xsl:variable>
>
> 	<xsl:template match="/">
> 		<xsl:value-of select="f:my-var()" />
> 		<xsl:apply-templates select="$f:control-inc"/>
> 		<xsl:value-of select="f:my-var()" />
> 		<xsl:apply-templates select="$f:control-inc"/>
> 		<xsl:value-of select="f:my-var()" />
> 		<xsl:apply-templates select="$f:control-dec"/>
> 		<xsl:value-of select="f:my-var()" />
> 		<xsl:apply-templates select="$f:control-dec"/>
> 		<xsl:value-of select="f:my-var()" />
> 	</xsl:template>
> </xsl:stylesheet>
>
> So I read the spec and I guess I understand why.
> Accumulator rule is not triggered by calling apply-templates, it does not
> matter how many times the same node is processed, the value for the
> accumulator will be the same.
>
> Do accumulators work only for the nodes from the source document or also
for
> nodes from documents loaded using doc() or document()?
>
> Jakub.


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