using Functions vs using templates in XSLT? - xslt

Question

What are the pros and cons of functions vs templates in XSLT?
I want to send a unix-timestamp and get an answer like "today" or "tomorrow" or "next week". Which method is most appropriate for this?

Answer 1

The main reason of choosing an <xsl:function> over a named template is the much greater degree of composability of a function.
It is very easy and convenient to write an <xsl:function> that produces the wanted results:
<xsl:function name="my:when" as="xs:string">
<xsl:param name="pDateTime" as="xs:dateTime"/>
<xsl:sequence select=
"for $vToday in xs:dateTime(current-date()),
$vTomorrow in $vToday
+ xs:dayTimeDuration('P1D'),
$vDayAfterTomorrow in $vTomorrow
+ xs:dayTimeDuration('P1D'),
$vNextWeek in $vToday
+ 7* xs:dayTimeDuration('P1D'),
$vNextFortnight in $vNextWeek
+ 7* xs:dayTimeDuration('P1D')
return
if($pDateTime lt $vToday)
then 'in the Past'
else if($pDateTime lt $vTomorrow)
then 'Today'
else if($pDateTime lt $vDayAfterTomorrow)
then 'Tomorrow'
else if($pDateTime lt $vNextWeek)
then 'This week'
else if($pDateTime lt $vNextFortnight)
then 'Next week'
else 'In the Future'
"/>
</xsl:function>
Here is a complete transformation:
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:my="my:my">
<xsl:output omit-xml-declaration="yes"/>
<xsl:template match="/">
<xsl:sequence select="my:when(current-dateTime())"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P1D'))"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P2D'))"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P3D'))"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P4D'))"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P5D'))"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P6D'))"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P7D'))"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P8D'))"/>,
<xsl:sequence select="my:when(current-dateTime()
+xs:dayTimeDuration('P9D'))"/>
</xsl:template>
<xsl:function name="my:when" as="xs:string">
<xsl:param name="pDateTime" as="xs:dateTime"/>
<xsl:sequence select=
"for $vToday in xs:dateTime(current-date()),
$vTomorrow in $vToday
+ xs:dayTimeDuration('P1D'),
$vDayAfterTomorrow in $vTomorrow
+ xs:dayTimeDuration('P1D'),
$vNextWeek in $vToday
+ 7* xs:dayTimeDuration('P1D'),
$vNextFortnight in $vNextWeek
+ 7* xs:dayTimeDuration('P1D')
return
if($pDateTime lt $vToday)
then 'in the Past'
else if($pDateTime lt $vTomorrow)
then 'Today'
else if($pDateTime lt $vDayAfterTomorrow)
then 'Tomorrow'
else if($pDateTime lt $vNextWeek)
then 'This week'
else if($pDateTime lt $vNextFortnight)
then 'Next week'
else 'In the Future'
"/>
</xsl:function>
</xsl:stylesheet>
when this transformation is applied (to any document -- not used), the wanted, correct result is produced:
Today,
Tomorrow,
This week,
This week,
This week,
This week,
This week,
Next week,
Next week,
Next week

Answer 2

In this case, an external function is best-suited.
XSLT is best suited for pattern matching and transformation, not computation.