Subject: RE: Re: What is $p in the definition of fn:subsequence ?
From: "Michael Kay" <mike@xxxxxxxxxxxx>
Date: Sat, 5 Jul 2008 14:19:45 +0100
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> The spec doesn't specify the desired behavior if $length is <= 0.
>
> Should the function return the empty sequence, a reversed
> subsequence (if $length is < 0) or should an error be raised?
> The same question goes for fn:substring().
>
I think these questions are answered by the equivalences given in the
(corrected) spec.
subsequence((1 to 10), 5, -3)
is equivalent to
(1 to 10)[5 le position() and position() lt 5 - 3]
which is an empty sequence.
The same applies to substring().
(Note, in case you are wondering why it is this way: subsequence was
deliberately designed to imitate substring(), and substring() was designed
on the 1.0 design principle of "no runtime errors except as a last resort")
Michael Kay
http://www.saxonica.com/
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