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> The let clause is also redundant because references to the
> variable can be replaced by the expression to which the variable is
> bound.
I am not sure I agree Michael.
To be strictly formal, LET is not syntactic sugar in XQuery.
It is syntactic sugar in most pure functional programming languages
(i.e. can be
eliminated by the rule that you cite) but not in XQuery, due to at least
two independent reasons:
(a) side effects as result of node constructors and
(b) context-sensitive semantics (e.g. namespaces and unordered{..})
Here are a couple of counter-examples.
(a) side effects as result of node constructors
let $x := <a/>
return fn:count(($x,$x)/.)
returns 1
while
fn:count((<a/>, <a/>)/.)
returns 2
(b) context sensitive semantics due to unordered {...}
let $x := (fn:doc("foo.xml")//a[@b=3])[1]
return unordered { $x }
is not equivalent to
unordered {(fn:doc("foo.xml")//a[@b=3])[1]}
The first one is deterministic, the second one not.
But in reality few programmers will realize those small subtle
differences.
Moreover, a good compiler should be able to detect the cases where
the rule you cite is applicable, and the apply it only under those
circumstances.
Best regards,
Dana
P.S> It is late in the night and I have no XQuery processor at hand to
run and
check those examples but I hope I got them right. I am sure you know
what I
mean anyway.
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