XSLT for-each with complex condition - xslt

Question

I am transforming following XML to generate HTML.
XML
<clause code="section6">
<variable col="1" name="R1C1" row="1">Water</variable>
<variable col="2" name="R1C2" row="1">true</variable>
<variable col="1" name="R2C1" row="2">Gas</variable>
<variable col="2" name="R2C2" row="2"></variable>
<variable col="1" name="R3C1" row="3">Petrol</variable>
<variable col="2" name="R3C2" row="3">true</variable>
<clause>
XSLT
1: <xsl:for-each select="$clause/variable[#col='1']">
2: <xsl:sort select="#row" data-type="number"/>
3: <xsl:variable name="row-id" select="#row"/>
4: <xsl:variable name="row" select="$clause/variable[#row=$row-id]"/>
5: <xsl:if test="$clause/variable[#col='2' and #row=$row-id]='true'">
6: <xsl:value-of name="row-no" select="concat(position(), ') ')"/>
7: <xsl:value-of select="$clause/variable[#col='1' and #row=$row-id]"/>
8: </xsl:if>
9: </xsl:for-each>
The transformation works fine and shows result 1) Water 3) Petrol
The issue is sequence number. You can see condition on Line 5 filters rows that only have 'true' value in col 2 and position() used for displaying sequence number. I cannot have running counter in XLST.
I was wondering if I can add condition of Line 5 with for-each at Line 1. The result with above example should be 1) Water 2) Patrol any advice?

Answer 1

Does this do what you want?
I drive the for-each selection on col 2 being true. That way position, which equals where we are in the selected set of nodes will equal 2 not 3
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:template match="/">
<xsl:for-each select="clause/variable[#col='2' and text()='true']">
<xsl:sort select="#row" data-type="number"/>
<xsl:variable name="row-id" select="#row"/>
<xsl:value-of select="concat(position(), ') ')"/>
<xsl:value-of select="/clause/variable[#col='1' and #row=$row-id]"/>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
Though I'd probably use templates in preference to the for-each and use current() so that we don't need the row-id variable:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:template match="/">
<xsl:apply-templates select="clause/variable[#col='2' and text()='true']">
<xsl:sort select="#row" data-type="number"/>
</xsl:apply-templates>
</xsl:template>
<xsl:template match="clause/variable[#col='2' and text()='true']">
<xsl:value-of select="concat(position(), ') ')"/>
<xsl:value-of select="/clause/variable[#col='1' and #row=current()/#row]"/>
</xsl:template>
</xsl:stylesheet>

Answer 2

I don't think you can express this with a single XPath 1.0 expression.
In XSLT 1.0 I will use keys and the solution becomes short, elegant and efficient:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:key name="kVarCol2" match="variable[#col=2]" use="#row"/>
<xsl:template match="/*">
<xsl:for-each select="variable[#col='1'][key('kVarCol2', #row)='true']">
<xsl:sort select="#row" data-type="number"/>
<xsl:value-of select="concat('
', position(), ') ', .)"/>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on the provided XML document (corrected to be made well-formed):
<clause code="section6">
<variable col="1" name="R1C1" row="1">Water</variable>
<variable col="2" name="R1C2" row="1">true</variable>
<variable col="1" name="R2C1" row="2">Gas</variable>
<variable col="2" name="R2C2" row="2"></variable>
<variable col="1" name="R3C1" row="3">Petrol</variable>
<variable col="2" name="R3C2" row="3">true</variable>
</clause>
the wanted, correct result is produced:
1) Water
2) Petrol
II. XPath 2.0 (single expression) solution:
for $i in 1 to max(/*/*/#row/xs:integer(.))
return
/*/variable[#row eq string($i)]
[#col eq '1'
and
../variable
[#row eq string($i)
and
#col eq '2'
and
. eq 'true'
]
]
/concat('
', position(), ') ', .)
When this XPath 2.0 expression is evaluated on the same XML document (above), the result is the same wanted string:
1) Water
2) Petrol