Conditional instructions

If syntax extensions are enabled, then the xsl:choose and xsl:if instructions are enhanced as follows:

• Within xsl:choose, the xsl:when and xsl:otherwise instructions can define the returned value using a select attribute in place of a sequence constructor. For example:

  <xsl:choose> <xsl:when test="$day = 'Monday'" select="1"/> <xsl:when test="$day = 'Tuesday'" select="2"/> <xsl:when test="$day = 'Wednesday'" select="3"/> <xsl:when test="$day = 'Thursday'" select="4"/> <xsl:when test="$day = 'Friday'" select="5"/> <xsl:otherwise select="-1"/> </xsl:choose>

• The xsl:if instruction can deliver its results using then and else attributes in place of a contained sequence constructor. For example:

  <xsl:if test="$day = 'Monday'" then="1" else="0"/>

  If the then attribute is present, the xsl:if instruction must be empty (have no children). Either attribute can be used independently; there is no requirement for both to be present.

These new forms of xsl:choose and xsl:if are particularly useful to compute the return value of a function, replacing xsl:sequence.

The new xsl:switch instruction provides an alternative to xsl:choose. It is best illustrated by example: