randomize node order xslt

Question

I have an XML file that contains nodes like this:

<values>
     <item>item 1</item>
     <item>item 2</item>
     <item>item 3</item>
     <item>item 4</item>
     <item>item 5</item>
</values>

I would like to get the list in a randomize order using xslt:

<values>
     <item>item 3</item>
     <item>item 5</item>
     <item>item 1</item>
     <item>item 4</item>
     <item>item 2</item>
</values>

I cannot use external resources like "xmlns:java="java.lang.Math" and "xmlns:math="http://exslt.org/math"

because of limitation.

maybe this links might help:

http://fxsl.sourceforge.net/articles/Random/Casting%20the%20Dice%20with%20FXSL-htm.htm

Answer 1

The following stylesheet will write the items to the output tree in random order. The stylesheet expects an external "initial-seed" number to be supplied at runtime as a parameter.

Note: since the items are only re-ordered without processing, it is not necessary to sort them, and the EXSLT node-set() function will not be required here after all.

<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:param name="initial-seed" select="123"/>

<xsl:template match="/">
    <values>
            <xsl:call-template name="pick-random-item">
                <xsl:with-param name="items" select="values/item"/>
            </xsl:call-template>
    </values>
</xsl:template>

<xsl:template name="pick-random-item">
    <xsl:param name="items" />
    <xsl:param name="seed" select="$initial-seed"/>
    <xsl:if test="$items">
        <!-- generate a random number using the "linear congruential generator" algorithm -->
        <xsl:variable name="a" select="1664525"/>
        <xsl:variable name="c" select="1013904223"/>
        <xsl:variable name="m" select="4294967296"/>
        <xsl:variable name="random" select="($a * $seed + $c) mod $m"/>
        <!-- scale random to integer 1..n -->
        <xsl:variable name="i" select="floor($random div $m * count($items)) + 1"/>
        <!-- write out the corresponding item -->
        <xsl:copy-of select="$items[$i]"/>
        <!-- recursive call with the remaining items -->
        <xsl:call-template name="pick-random-item">
            <xsl:with-param name="items" select="$items[position()!=$i]"/>
            <xsl:with-param name="seed" select="$random"/>
        </xsl:call-template>
    </xsl:if>
</xsl:template>

</xsl:stylesheet>

Applied to your input with the default initial-seed (123), the output is:

<?xml version="1.0" encoding="utf-8"?>
<values>
   <item>item 2</item>
   <item>item 3</item>
   <item>item 1</item>
   <item>item 4</item>
   <item>item 5</item>
</values>

When performed with a seed of 1234, the output is:

<?xml version="1.0" encoding="utf-8"?>
<values>
   <item>item 4</item>
   <item>item 1</item>
   <item>item 5</item>
   <item>item 2</item>
   <item>item 3</item>
</values>