Frans Englich wrote:
On Wednesday 24 May 2006 11:26, Florent Georges wrote:
Why is it not available to the user?
Probably because no one thought a reasonable usage
scenario exists for it(although I don't know for sure).
A custom error reporting function (based on fn:error()) is
an enough interesting use case, isn't it? But more
generaly, if a system function returns such an absorbent
type [1], you'll need one time or another to use this type,
IMHO.
I've myself been thinking a bit about this, while writing
XQuery test cases. Try declaring a function with the
return type empty-sequence()
I didn't try to really test it. Actually, with Saxon
8.7.1j we can use every SequenceType (for example xs:string,
node(), empty-sequence() or text()), even with the '+'
occurrence indicator. As if no static type checking was
made at all. As if this special case was banned from the
static type checking engine.
[1] I don't know if "absorbent" is the right English word.
I mean a mathematical property, "for every element in
a set, using an operation with X will always returns
X". For example 0 on R,*. Here, for every sequence,
if the static type of one item is "none" then the
static type of the whole sequence is "none" (I think).
Regards,
--drkm
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