using Functions vs using templates in XSLT?

What are the pros and cons of functions vs templates in开发者_JAVA技巧 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?

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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

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In this case, an external function is best-suited.

XSLT is best suited for pattern matching and transformation, not computation.