How to select the smallest value from a bunch of variables? - xslt

Question

Assume I have variables $a, $b, $c and $d which all hold numbers. I would like to get the smallest (largest) value. My typical XSLT 1.0 approach to this is
<xsl:variable name="minimum">
<xsl:for-each select="$a | $b | $c | $d">
<xsl:sort
select="."
data-type="number"
order="ascending" />
<xsl:if test="position()=1"><xsl:value-of select="." /></xsl:if>
</xsl:for-each>
</xsl:variable>
However, my xslt 1.0 processor complains with
runtime error: file stylesheet.xslt line 106 element for-each
The 'select' expression does not evaluate to a node set.
How can I compute the minimum (maximum) of the given values?
Of course, I could use a long series of <xsl:when> statements and check all combinations, but I'd rather like a smaller solution.

Answer 1

If the variables have statically defined values (not dynamically computed), then something like the following can be done with XSLT 1.0:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:variable name="vA" select="3"/>
<xsl:variable name="vB" select="1"/>
<xsl:variable name="vC" select="9"/>
<xsl:variable name="vD" select="5"/>
<xsl:template match="/">
<xsl:for-each select=
"document('')/*/xsl:variable
[contains('|vA|vB|vC|vD|', concat('|', #name, '|'))]
/#select
">
<xsl:sort data-type="number" order="ascending"/>
<xsl:if test="position() = 1">
Smallest: <xsl:value-of select="."/>
</xsl:if>
<xsl:if test="position() = last()">
Largest: <xsl:value-of select="."/>
</xsl:if>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
When this transformation is applied on any XML document (not used), the wanted, correct result is produced:
Smallest: 1
Largest: 9
II. Now, suppose the variables are dynamically defined.
We can do something like this (but need the xxx:node-set() extension function):
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:ext="http://exslt.org/common">
<xsl:output method="text"/>
<xsl:variable name="vA" select="number(/*/*[3])"/>
<xsl:variable name="vB" select="number(/*/*[1])"/>
<xsl:variable name="vC" select="number(/*/*[9])"/>
<xsl:variable name="vD" select="number(/*/*[5])"/>
<xsl:template match="/">
<xsl:variable name="vrtfStore">
<num><xsl:value-of select="$vA"/></num>
<num><xsl:value-of select="$vB"/></num>
<num><xsl:value-of select="$vC"/></num>
<num><xsl:value-of select="$vD"/></num>
</xsl:variable>
<xsl:for-each select="ext:node-set($vrtfStore)/*">
<xsl:sort data-type="number" order="ascending"/>
<xsl:if test="position() = 1">
Smallest: <xsl:value-of select="."/>
</xsl:if>
<xsl:if test="position() = last()">
Largest: <xsl:value-of select="."/>
</xsl:if>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
when this transformation is applied on the following XML document:
<nums>
<num>01</num>
<num>02</num>
<num>03</num>
<num>04</num>
<num>05</num>
<num>06</num>
<num>07</num>
<num>08</num>
<num>09</num>
<num>10</num>
</nums>
the wanted, correct result is produced:
Smallest: 1
Largest: 9

Answer 2

This XSLT 1.0 solution uses recursive templates to parse a delimited list of values to return the min/max value from the list.
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
<xsl:variable name="a" select="'3'"/>
<xsl:variable name="b" select="'1'"/>
<xsl:variable name="c" select="'9'"/>
<xsl:variable name="d" select="'5'"/>
<xsl:template match="/">
<xsl:text>
Smallest: </xsl:text>
<xsl:call-template name="min">
<xsl:with-param name="values" select="concat($a,',',$b,',',$c,',',$d)"/>
</xsl:call-template>
<xsl:text>
Largest: </xsl:text>
<xsl:call-template name="max">
<xsl:with-param name="values" select="concat($a,',',$b,',',$c,',',$d)"/>
</xsl:call-template>
</xsl:template>
<xsl:template name="min">
<xsl:param name="values" />
<xsl:param name="delimiter" select="','"/>
<xsl:param name="min"/>
<xsl:variable name="currentValue" >
<xsl:choose>
<xsl:when test="contains($values, $delimiter)">
<xsl:value-of select="substring-before($values,$delimiter)"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$values"/>
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:variable name="minimumValue">
<xsl:choose>
<xsl:when test="$min and $min > $currentValue">
<xsl:value-of select="$currentValue"/>
</xsl:when>
<xsl:when test="$min">
<xsl:value-of select="$min"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$currentValue" />
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:choose>
<xsl:when test="substring-after($values,$delimiter)">
<xsl:call-template name="min">
<xsl:with-param name="min" select="$minimumValue" />
<xsl:with-param name="values" select="substring-after($values,$delimiter)" />
<xsl:with-param name="delimiter" select="$delimiter"/>
</xsl:call-template>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$minimumValue" />
</xsl:otherwise>
</xsl:choose>
</xsl:template>
<xsl:template name="max">
<xsl:param name="values" />
<xsl:param name="delimiter" select="','"/>
<xsl:param name="max"/>
<xsl:variable name="currentValue" >
<xsl:choose>
<xsl:when test="contains($values, $delimiter)">
<xsl:value-of select="substring-before($values,$delimiter)"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$values"/>
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:variable name="maximumValue">
<xsl:choose>
<xsl:when test="$max and $currentValue > $max">
<xsl:value-of select="$currentValue"/>
</xsl:when>
<xsl:when test="$max">
<xsl:value-of select="$max"/>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$currentValue" />
</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:choose>
<xsl:when test="substring-after($values,$delimiter)">
<xsl:call-template name="max">
<xsl:with-param name="max" select="$maximumValue" />
<xsl:with-param name="values" select="substring-after($values,$delimiter)" />
<xsl:with-param name="delimiter" select="$delimiter"/>
</xsl:call-template>
</xsl:when>
<xsl:otherwise>
<xsl:value-of select="$maximumValue" />
</xsl:otherwise>
</xsl:choose>
</xsl:template>
</xsl:stylesheet>
When executed, produces the following output:
Smallest: 1
Largest: 9

Answer 3

I've never had to do this in 1.0 (I use 2.0), but you could do this:
<xsl:variable name="minimum">
<xsl:choose>
<xsl:when test="$b > $a and $c > $a and $d > $a"><xsl:value-of select="$a"/></xsl:when>
<xsl:when test="$a > $b and $c > $b and $d > $b"><xsl:value-of select="$b"/></xsl:when>
<xsl:when test="$b > $c and $a > $c and $d > $c"><xsl:value-of select="$c"/></xsl:when>
<xsl:when test="$b > $d and $c > $d and $a > $d"><xsl:value-of select="$d"/></xsl:when>
</xsl:choose>
</xsl:variable>
There's got to be a better way though.