[4suite] Using EXSLT functions from an XPath query

[John L. Clark]

I'm trying to use EXSLT functions from within an XPath query, but the
function map does not seem to be registering.  Here's (nearly) what
I'm doing:

  from Ft.Xml.Xslt import Exslt
  # other imports
  xpath_expression = Compile(some_expression_string)
  xpath_context = Context(None, processorNss=NSS,
                            extFunctionMap=Exslt.ExtFunctions)
  doc = Parse(some_filename)
  result = Evaluate(xpath_expression, doc, xpath_context)

In this snippet, `NSS` contains the map {'date':
'http://exslt.org/dates-and-times'}, `some_expression_string` makes an
EXSLT function call, and this results in the following exception:

  Ft.Xml.XPath.RuntimeException: Undefined function: "date:difference".

Any thoughts?

Thanks,

    John L. Clark

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