Achieving “While” functionality in XSL using recursive custom template call

Few days before I came across one XSL transformation business requirement where an xml element of Input data is having  two sub elements named “NumberBlockVON” and “NumberBlockBIS” . Name of these two is mentioned by our business user.  “NumberBlockVON” will have a positive Integer value and same happens for “NumberBlockBIS” . Now the requirement was whatever value specified as “NumberBlockBIS” that will be treated in output xml as “the power of” the value specified for “NumberBlockVON” . It means in out put xml “NumberBlockVON” will pass as it is but the value for “NumberBlockBIS” will be replaced by the <NumberBlockVON> to the power of <NumberBlockBIS>.

<PickPackShipCustomElement>
  <NumberBlockVON>5</NumberBlockVON>
  <NumberBlockBIS>6</NumberBlockBIS>
</PickPackShipCustomElement> 

Now if it is a java requirement we can finished it off easily by writing a looping construct with the limit from 0 to <NumberBlockBIS>, and multiply the <NumberBlockVON> that many times. But here the problem is XSL constructs can loop through xml nodes , but it can’t loop through from 0 to any other specific value with in a single xml node. So we cant depend on XSL given constructs.
We use a custom XSL template to achieve this and call the template recursively with tuned parameters.<NumberBlockVON> value and <NumberBlockBIS>value is passed as a parameter to the template.How we achieve this is explained below with code snippet.

<xsl:templatename="whileImplTemplate">


< !--parameter limit_var is used to hold value of NumberBlockBIS which is used as a power value
-->

  <xsl:paramname="limit_var"/>


< !--parameter var is used to hold value of NumberBlockVON which is used as a base value
-->

  <xsl:param name="var"/>


< !--parameter Outvar is used to hold output value 
-->

  <xsl:param name="Outvar" select="1"/>
  <xsl:param name="count_index" select="0"/>
  <xsl:variable name="out_var" select="$Outvar"/>


< !--while logic Implementation
-->

   <xsl:choose>


< !--Is limit achieved -->
    <xsl:when test="$count_index < $limit_var">
< !--recursive template call if limit does not achieved--
>

     <xsl:call-template name="whileImplTemplate">
      <xsl:with-param name="limit_var" select="$limit_var"/>
      <xsl:with-param name="var" select="$var"/>
      <xsl:with-param name="count_index" select="number($count_index)+1"/>
     <xsl:with-param name="Outvar" select="number($var)*number($out_var)"/>
    </xsl:call-template>


< !-- End template -->

    </xsl:when>
     <xsl:otherwise>
      <xsl:value-of select="$out_var"/>


< !--If limit achieved then print value -->
    </xsl:otherwise>
  <xsl:choose>
</xsl:template> 

As a result the output comes like below

<PickPackElement>
  <NumberBlockVON>5</NumberBlockVON>
  <NumberBlockBIS>15625</NumberBlockBIS>
</PickPackElement>