Increase number in text string for each match

I am looking to shorten my XSLT codebase by seeing if XSLT can increase a text number for each match. The text number exists in both the attribute value "label-period0" and the "xls:value-of" value.

The code works, no errors so this is more a question of how to shorten the code and make use of some sort of iteration on a specific character in a string.

I added 2 similar code structures for "period0" and "period1" to better see what exactly are the needed changes in terms of the digit in the text strings.

Source XML file:

<data>
  <periods>
    <period0><from>2016-01-01</from><to>2016-12-01</to></period0>
    <period1><from>2015-01-01</from><to>2015-12-01</to></period1>
    <period2><from>2014-01-01</from><to>2014-12-01</to></period2>
    <period3><from>2013-01-01</from><to>2013-12-01</to></period3>
  </periods>
  <balances>
    <balance0><instant>2016-12-31</instant></balance0>
    <balance1><instant>2015-12-31</instant></balance1>
    <balance2><instant>2014-12-31</instant></balance2>
    <balance3><instant>2013-12-31</instant></balance3>
  </balances>
</data>

XSL file:

<?xml version="1.0" encoding="UTF-8"?>

<xsl:transform
  version="3.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
>

  <xsl:output method="xml" indent="yes"/>

  <!-- Block all data that has no user defined template -->
  <xsl:mode on-no-match="shallow-skip"/>

  <xsl:template match="data">

    <results>

      <periods>

        <periods label="period0">
          <xsl:value-of
            select =
            "concat(periods/period0/from, '--', periods/period0/to)"
          />
        </periods>

        <periods label="period1">
          <xsl:value-of
            select =
            "concat(periods/period1/from, '--', periods/period1/to)"
          />
        </periods>

        <!-- Etc for period [2 and 3]-->

      </periods>

      <balances>

        <balance label="balance0">
          <xsl:value-of select ="balances/balance0/instant"/>
        </balance>

        <!-- Etc for balance [1,2 and 3] -->

      </balances>

    </results>

  </xsl:template>

</xsl:transform>

Result:

<?xml version="1.0" encoding="UTF-8"?>
<results>
   <periods>
      <periods label="period0">2016-01-01--2016-12-01</periods>
      <periods label="period1">2015-01-01--2015-12-01</periods>
   </periods>
   <balances>
      <balance label="balance0">2016-12-31</balance>
   </balances>
</results>

Wanted result:

(with an XSL that steps the digit in the text string, or any other logics in XSL that could cater for manipulating the digit in text string)

<?xml version="1.0" encoding="UTF-8"?>
<results>
   <periods>
      <periods label="period0">2016-01-01--2016-12-01</periods>
      <periods label="period1">2015-01-01--2015-12-01</periods>
      <periods label="period2">2014-01-01--2015-12-01</periods>
      <periods label="period3">2013-01-01--2015-12-01</periods>
   </periods>
   <balances>
      <balance label="balance0">2016-12-31</balance>
      <balance label="balance1">2015-12-31</balance>
      <balance label="balance2">2014-12-31</balance>
      <balance label="balance3">2013-12-31</balance>
   </balances>
</results>

Solution

Couldn't you do simply something like:

<xsl:template match="/data">
    <results>
        <periods>
            <xsl:for-each select="periods/*">
                <periods label="{name()}">
                    <xsl:value-of select="from"/>
                    <xsl:text>--</xsl:text>
                    <xsl:value-of select="to"/>
                </periods>
            </xsl:for-each>
        </periods>
        <balances>
            <xsl:for-each select="balances/*">
                <balance label="{name()}">
                    <xsl:value-of select="instant"/>
                </balance>
            </xsl:for-each>
        </balances>
    </results>
</xsl:template>

If you want to do your own numbering, you can change:

                <periods label="{name()}">

to:

                 <periods label="period{position() - 1}">