XSLT 1.0 : Iterate over characters in a string

Question

I need to iterate over the characters in a string to build an XML structure.

Currently, I am doing this :

<xsl:template name="verticalize">
    <xsl:param name="text">Some text</xsl:param>
    <xsl:for-each select="tokenize(replace(replace($text,'(.)','$1\\n'),'\\n$',''),'\\n')">
        <xsl:element name="para">
            <xsl:value-of select="."/>
        </xsl:element>
    </xsl:for-each>
</xsl:template>

This produces something like :

<para>S</para>
<para>o</para>
<para>m</para>
<para>e</para>
<para> </para>
<para>t</para>
<para>e</para>
<para>x</para>
<para>t</para>

This works fine with Xpath 2.0. But I need to apply the same treatment in a XPath 1.0 environment, where the replace() method is not available.

Do you know a way to achieve this ?

Answer 1

<xsl:template name="letters">
  <xsl:param name="text" select="'Some text'" />
  <xsl:if test="$text != ''">
    <xsl:variable name="letter" select="substring($text, 1, 1)" />
    <para><xsl:value-of select="$letter" /></para>
    <xsl:call-template name="letters">
      <xsl:with-param name="text" select="substring-after($text, $letter)" />
    </xsl:call-template>
  </xsl:if>
</xsl:template>

Answer 2

If the string length is not huge, you can use a recursively called template to achieve this, passing the index of the character to be processed as parameter into the template.

Like so:

<xsl:template name="verticalize">
    <xsl:param name="text">Some text</xsl:param>
    <xsl:param name="index" select="1" />
    <xsl:if test="string-length($text) &gt;= $index">
        <xsl:element name="para">
            <xsl:value-of select="substring($text, $index, 1)"/>
        </xsl:element>
        <xsl:call-template name="verticalize">
            <xsl:with-param name="text" select="$text" />
            <xsl:with-param name="index" select="$index+1" />
        </xsl:call-template>
    </xsl:if>
</xsl:template>

If the string is longer than that, you can use a similar approach but with a divide-and-conquer algorithm, so that you have a maximum recursion depth of log2(string-length), like so:

<xsl:template name="verticalize">
    <xsl:param name="text">Some text</xsl:param>
    <xsl:param name="left" select="1" />
    <xsl:param name="right" select="string-length($text)" />
    <xsl:choose>
        <xsl:when test="$left = $right">
            <xsl:element name="para">
                <xsl:value-of select="substring($text, $left, 1)"/>
            </xsl:element>
        </xsl:when>
        <xsl:when test="$left &lt; $right">
            <xsl:variable name="middle" select="floor(($left+$right) div 2)" />
            <xsl:call-template name="verticalize">
                <xsl:with-param name="text" select="$text" />
                <xsl:with-param name="left" select="$left" />
                <xsl:with-param name="right" select="$middle" />
            </xsl:call-template>
            <xsl:call-template name="verticalize">
                <xsl:with-param name="text" select="$text" />
                <xsl:with-param name="left" select="$middle+1" />
                <xsl:with-param name="right" select="$right" />
            </xsl:call-template>
        </xsl:when>
    </xsl:choose>
</xsl:template>