Can StringBuilder be emulated in XSLT?

Question

I am trying to emulate StringBuilder behavior in an XSL. Is there a way to do this. It seems pretty hard given the fact that XSLT is a functional programming language

Answer 1

Have a look at the concat() and string-join() functions, maybe that's what you are after.

Answer 2

You can use all available standard XPath 2.0 string functions, such as concat(), substring(), substring-before(), substring-after(), string-join(), ..., etc.

However, in case you need a very fast implementation of strings (even faster than the .NET string class) you'll probably be interested in the C# implementation of the finger-tree data structure and the extension functions I provided for the Saxon XSLT processor that wrap the finger-tree-based string.

Answer 3

You can get the accumulting concats quite simply with just a little bit of recursion if you're looking at a node-set (so long as you can construct the xpath to find the node-set), doing this so you can add arbitrary bits and pieces in and out of the flow it starts getting messy.

Try this for starters (does join as well):

<xsl:template match="/">
     <xsl:variable name="s">
        <xsl:call-template name="stringbuilder">
         <xsl:with-param name="data" select="*" /><!-- your path here -->
        </xsl:call-template>
     </xsl:variable>
     <xsl:value-of select="$s" /><!-- now contains a big concat string -->
</xsl:template>

<xsl:template name="stringbuilder">
    <xsl:param name="data"/>
    <xsl:param name="join" select="''"/>
    <xsl:for-each select="$data/*">
     <xsl:choose>
      <xsl:when test="not(position()=1)">
       <xsl:value-of select="concat($join,child::text())"/>
      </xsl:when>
      <xsl:otherwise>
       <xsl:value-of select="child::text()"/>
      </xsl:otherwise>
     </xsl:choose>  
    </xsl:for-each>
</xsl:template>

All manner of extensions to that may be required: perhaps you want to trim, perhaps you want to tunnel through hierarchies as well. I'm not sure a bulletproof general solution exists.