>>>>> "Colin" == Colin Paul Adams <colin@xxxxxxxxxxxxxxxxxx> writes:

    Colin> Or are you requesting banning non-pure functions
    Colin> altogether?  This would mean disallowing calls to extension
    Colin> functions, or else insisting extension functions must not
    Colin> have side-effects. The latter condition would be
    Colin> incompatible with XSLT 1.0, I think

Actually, it's far worse than that - functions such as last() are not
referentially transparent, so you can't have referential transparency.

Given that, would there be any advantage to having f($x) is f($x)
always returning true()?
-- 
Colin Adams
Preston Lancashire