XSLT script to report Unicode characters and code bloc

I'm working on a simple XSLT 2.0 script to list all distinct Unicode
characters used in a file. That part of the script takes very few lines,
thanks to distinct-values(), codepoints-to-string(), and
string-to-codepoints().

However, I'd also like to group the output by code block:

http://www.fileformat.info/info/unicode/block/index.htm

Best way I can see to do it is to write a local function that tests the
codepoint value and uses lots and lots of <xsl:when> case tests to
determine which block the character falls into. Not hard but a bit
tedious. Has anyone invented this wheel already?

DS

-- 
David Sewell, Editorial and Technical Manager
ROTUNDA, The University of Virginia Press
PO Box 801079, Charlottesville, VA 22904-4318 USA
Courier: 310 Old Ivy Way, Suite 302, Charlottesville VA 22903
Email: dsewell@xxxxxxxxxxxx   Tel: +1 434 924 9973
Web: http://rotunda.upress.virginia.edu/