Q about node-set comparisons, or casting, or maybe variables

[alyxandr]

It would help if I even knew what sort of question it was... could someone please gently explain to me what's happening here:

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<types good="A">

    <type>A</type>

    <type>B</type>

    <type>A</type>

    <type>C</type>

</types>



<xsl:template match="types">

    <xsl:message select="concat('1: Good=', count(type[. = @good]))"/>

    <xsl:variable name="g" select="@good"/>

    <xsl:message select="concat('2: Good=', count(type[. = $g]))"/>

</xsl:template>

Result:

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[Saxon-EE]1: Good=0

[Saxon-EE]2: Good=2

Is there something special about comparing element and attribute nodes? What sort of magical thing is the variable declaration doing here? (Saxon-EE 9.3.0.5 in Oxygen 13.2)

Thanks, --alex.

[adrian]

Hi,

There's no magic there, it's just XSLT+XPath.

The variable evaluates the XPath(@good) in the context of the types element (from the XSLT) and obtains the actual value of the attribute, which is 'A'.

For the other expression

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count(type[. = @good]))

what happens is that the "good" attribute is evaluated in the context of the type element. It's not there, so it fails.

However it works as expected like this (looks starting from the root):

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count(type[. = /types/@good])

or like this (looks at the attribute of the parent):

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count(type[. = parent::node()/@good])

Regards,
Adrian

[alyxandr]

It sounds so simple when you say it...
I am no longer (as) confused about context-in-predicates, thanks! --alex.