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Hi Dare,
> I wouldn't mind being able to create extension types and extension
> functions in XSLT that could manipulate units of measure as
> intrinsic types the same way strings, booleans and numbers are
> supported (plus dates if you use EXSLT).
Right. That was the kind of thing that the proof-of-concept
implementation from http://www.jenitennison.com/datatypes/ was
supposed to emulate. Obviously it can't hook into the comparison
operators in XPath, but it defines the functions you need.
So you'd define your measurements with:
<datatypes xmlns="http://www.jenitennison.com/datatypes";
ns="http://www.example.com/datatypes/measurements";>
<datatype name="kilometre">
<parse><ref name="number" /></parse>
</datatype>
<datatype name="mile">
<parse><ref name="number" /></parse>
</datatype>
<cast from="kilometre" to="mile">
<value-of select=". div 1.62" />
</cast>
<cast from="mile" to="kilometre">
<value-of select=". * 1.62" />
</cast>
<define name="number">
<ref name="digits" />
<optional><string>.</string><ref name="digits" /></optional>
</define>
<define name="digits">
<oneOrMore>
<charGroup><range from="0" to="9" /></charGroup>
</oneOrMore>
</define>
</datatypes>
Run it through the datatypes.xsl stylesheet and you'd get an XSLT 2.0
stylesheet that defines a bunch of functions for these datatypes.
Import that into your stylesheet, and you can do things like:
m:compare-miles(m:mile('2000'),
m:mile(m:kilometre(River/@length)))
and you'd get -1 if the River is less than 2000 miles long, 1 if the
River is more than 2000 miles long, and 0 if it was exactly 2000 miles
long.
Cheers,
Jeni
---
Jeni Tennison
http://www.jenitennison.com/
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