XSL: create optional class attributes in HTML output

When generating styled HTML output from XML, you might need to attach a special class to the first and/or the last element in a series (for example, first and last child). An only child would obviously have both classes attached to it (don't forget, class attribute can list multiple classes separated by a whitespace). The code to generate optimal list of HTML classes (or doing a generic join of list elements) is pretty simple:

<xsl:variable name="class">
<xsl:if test="position() = 1"> FirstInSeries</xsl:if>
<xsl:if test="position() = last()"> LastInSeries</xsl:if>
</xsl:variable>

<xsl:if test="$class != ''">
<xsl:attribute name="class">
  <xsl:value-of select="substring-after($class,' ')" />
</xsl:attribute>
</xsl:if>

Please note the following:

• Each value in the list has a leading whitespace. The list values are thus properly separated, but the result has an extra leading whitespace.
• The last xsl:if instruction tests if the class attribute is needed (detailed description of this trick).
• The substring-after function removes the leading whitespace, resulting in the desired value for the class attribute.