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xsltdivide-and-conquer

How to create node set from values


How can we create a node set from values....

I have n numbers 1,2,3.......n.

I want to create a node set

<MYNMUMS>
<MYNUM>1</MYNUM>
<MYNUM>2</MYNUM>
<MYNUM>3</MYNUM>
<MYNUM>4</MYNUM>
....
<MYNUM>N</MYNUM>
</MYNMUMS>

Solution

  • As easy as that:

    XSLT 1.0 solution:

    This transformation:

    <xsl:stylesheet version="1.0"
     xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
     <xsl:output omit-xml-declaration="yes" indent="yes"/>
    
        <xsl:template match="/">
         <MyNums>
           <xsl:call-template name="generateNumNodes">
             <xsl:with-param name="pStart" select="1"/>
             <xsl:with-param name="pEnd" select="10"/>
           </xsl:call-template>
         </MyNums>
        </xsl:template>
    
        <xsl:template name="generateNumNodes">
          <xsl:param name="pStart"/>
          <xsl:param name="pEnd"/>
    
          <xsl:if test="$pEnd >= $pStart">
            <xsl:variable name="vNumNodes"
               select="$pStart -$pEnd+1"/>
    
            <xsl:choose>
              <xsl:when test="$vNumNodes = 1">
                <MyNum><xsl:value-of select="$pStart"/></MyNum>
              </xsl:when>
              <xsl:otherwise>
                <xsl:variable name="vHalf" select=
                  "floor(($pStart+$pEnd) div 2)"/>
                <xsl:call-template name="generateNumNodes">
                  <xsl:with-param name="pStart" select="$pStart"/>
                  <xsl:with-param name="pEnd" select="$vHalf"/>
                </xsl:call-template>
    
                <xsl:call-template name="generateNumNodes">
                  <xsl:with-param name="pStart" select="$vHalf+1"/>
                  <xsl:with-param name="pEnd" select="$pEnd"/>
                </xsl:call-template>
              </xsl:otherwise>
            </xsl:choose>
          </xsl:if>
        </xsl:template>
    </xsl:stylesheet>
    

    when applied on any XML document (not used), produces the desired output:

    <MyNums>
       <MyNum>1</MyNum>
       <MyNum>2</MyNum>
       <MyNum>3</MyNum>
       <MyNum>4</MyNum>
       <MyNum>5</MyNum>
       <MyNum>6</MyNum>
       <MyNum>7</MyNum>
       <MyNum>8</MyNum>
       <MyNum>9</MyNum>
       <MyNum>10</MyNum>
    </MyNums>
    

    Do note the following:

    1. The template generateNumNodes calls itself recursively.

    2. This recursion is both time ( O(N) ), and space ( O(log2(N)) ) efficient and practically does overflow the stack -- no SO here!

    3. The above feature is achieved by implementing the recursion in a DVC (DiVide and Conquer) style.

    4. Unlike tail-recursion it will be successfully executed on any compliant XSLT processor.

    5. The maximum recursion depth needed to generate 1000000 (one million numbers) is just 19.

    XSLT 2.0 solution:

    Even more elementary, no recursion, just using the XPath 2.0 to operator:

    <xsl:stylesheet version="2.0"
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    >
         <xsl:output omit-xml-declaration="yes" indent="yes"/>
    
        <xsl:template match="/">
            <MyNums>
              <xsl:for-each select="1 to 10">
                <MyNums>
                  <xsl:sequence select="."/>
                </MyNums>
              </xsl:for-each>
            </MyNums>
        </xsl:template>
    </xsl:stylesheet>