RE: RE: XSLT 2.0/XPath 2.0 Date arithmetic

Permit me to parse your answer and ask additional questions. I've already managed to munge the string into the proper format with concat() and substring(), but this

<xsl:function name="f:to-iso-date" as="xs:date">
  <xsl:param name="in" as="my:yyyymmdd-date"/>
  <xsl:sequence select="xs:date(replace($in, '(\d{4})(\d{2})(\d{2})',
'$1-$2-$3'))"/>
</xsl:function>

is appealing because of it's perl-ishness (yes, of course perl incorporated existing concepts from UNIX shell utilities like sed and awk, but I first encountered them when learning perl), and because the function casts the return value to an xs:date.

In order to use this approach you suggest that I incorporate an xsl:import-schema declaration in my stylesheet and use it with either of the functions.

On the other hand, I'm using the non-schema-aware version of Saxon.

In reviewing the section on xsl:import-schema in "XSLT 2.0 Programmer's Reference" on page 324 I note that, "This declaration is only available in a schema-aware processor." So, how then would substituting " ... xs:string in place of my:yyyymmdd-date ..." solve that issue?

I am puzzled by what appears to me as an inconsistency in the answer which I must attribute to my weak grasp of the subject. If I cannot use the suggested approach because my processor is not schema-aware, is there some other native XSLT 2.0 approach, or am I forced to use some extension function?


-- 
Charles Knell
cknell@xxxxxxxxxx - email



-----Original Message-----
From:     Michael Kay <mike@xxxxxxxxxxxx>
Sent:     Thu, 18 May 2006 08:27:54 +0100
To:       <xsl-list@xxxxxxxxxxxxxxxxxxxxxx>
Subject:  RE:  XSLT 2.0/XPath 2.0 Date arithmetic

> 
> Given a parameter, let's call it "today" in the form of this 
> string "20060517", how do I create a variable, let's call it 
> "tMinus1" such that it represents a day earlier than 
> "20060517", that would be "20060516". So long as "$today" 
> isn't the first day of a month, a simple subtraction and 
> followed by a type cast that I don't grasp would do the trick.
> 
> What I'm looking for is guidance on date arithmetic.

You'd be much better off working with the xs:date type, which uses the
format 2006-05-17.

So, two functions to convert between your non-standard dates and standard
xs:date objects:

<xsl:import-schema>
  <xs:schema target-namespace="http://my-date">
    <xs:simpleType name="yyyymmdd-date">
      <xs:restriction base="xs:string">
        <xs:pattern value="[0-9]{4}[0-1][0-9][0-3][0-9]"/>
      </
    </
  </
</
      

<xsl:function name="f:to-iso-date" as="xs:date">
  <xsl:param name="in" as="my:yyyymmdd-date"/>
  <xsl:sequence select="xs:date(replace($in, '(\d{4})(\d{2})(\d{2})',
'$1-$2-$3'))"/>
</xsl:function>

<xsl:function name="f:to-yyyymmdd-date" as="my:yyyymmdd-date">
  <xsl:param name="in" as="xs:date"/>
  <xsl:sequence select="my:yyyymmdd-date(translate(string($in, '-', ''))"/>
</xsl:function>

then:
   select="f:to-yyyymmdd-date(f:to-iso-date($input-date) -
xs:dayTimeDuration('PT1D'))"

If you're not schema-aware, then use xs:string in place of my:yyyymmdd-date
- all you lose is type-checking.

Michael Kay
http://www.saxonica.com/