[xquery-talk] range implementations -- which is correct?

[Michael Rys]

It should be an error since it is easily confusing and mistaken to mean
to give me position() = 1 to 2 while the general EBV sematics is not
that.

Also, the problem is with general atomic sequences and the necessity to
be able to statically determine whether you have a positional access or
a general EBV test which again is not that simple in the case of
sequences (that at runtime may have more than one item).

Making this an error leaves all these issues outside and provide us with
the option to change it in a future version.

Best regards
Michael

> -----Original Message-----
> From: talk-bounces at xquery.com [mailto:talk-bounces at xquery.com] On
Behalf
> Of Howard Katz
> Sent: Tuesday, June 21, 2005 3:48 PM
> To: 'Michael Kay'; talk at xquery.com
> Subject: RE: [xquery-talk] range implementations -- which is correct?
> 
> Informative as always. Thank you!
> 
> Each of the three implementations is indeed correct for
> 
>    ( <a/>, <b/>, <c/> )[ position() = 1 to 2 ]
> 
>    => <a/>,  <b/>
> 
> What's led to the revised view that EBV( atomic-sequence ) is an
error?
> 
> Howard
> 
>  > -----Original Message-----
>  > From: Michael Kay [mailto:mhk at mhk.me.uk]
>  > Sent: Tuesday, June 21, 2005 3:28 PM
>  > To: 'Howard Katz'; talk at xquery.com
>  > Subject: RE: [xquery-talk] range implementations -- which is
correct?
>  >
>  > Saxon is correct against the most recent working draft: the
>  > effective boolean value of a sequence of several integers is
>  > now an error. Before the most recent draft, the EBV of any
>  > sequence containing more than one item was true; so Galax
>  > was correct. There was a prehistory in which "[1 to 2]" was
>  > recognized as some kind of custom syntax to extract a
>  > subsequence - at that stage (1 to 2) wasn't a
>  > general-purpose expression that could be composed with other
>  > expressions - so MarkLogic is reflecting that history.
>  > However, this had disappeared from the language before the
>  > May 2003 draft.
>  >
>  > Now try the correct syntax in each of the products:
>  >
>  > ( <a/>, <b/>, <c/> )[ position() = 1 to 2 ]
>  >
>  > Michael Kay
>  > http://www.saxonica.com/
>  >
>  > >
>  > > What's the result of invoking
>  > >
>  > >        ( <a/>, <b/>, <c/> )[ 1 to 2 ]
>  > >
>  > > ----------------------------
>  > >
>  > > MarkLogic 3.0 (May 2003 wd) returns
>  > >
>  > >      <a/>
>  > >      <b/>
>  > >
>  > > Galax 0.5.0 (Oct 2004 wd) returns
>  > >
>  > >      <a/>
>  > >      <b/>
>  > >      <c/>
>  > >
>  > > Saxon 8.4 (Feb 2005 wd) returns
>  > >
>  > >    "Error: Effective boolean value is not defined for a sequence
>  > >     of two or more items starting with an atomic value
>  > >
>  > > The situation is made somewhat more confusing because each
>  > > implementation is implemented against a different version
>  > of the wd.
>  > > More precisely there are two questions:
>  > >
>  > > (1) Which of the above results are correct (or incorrect) for the
>  > > version of the working draft against which they were
>  > implemented, and
>  > > (2) Which are correct (or incorrect) against the most
>  > recent working
>  > > draft of April 2005?
>  > >
>  > > Howard
>  > >
>  > > _______________________________________________
>  > > talk at xquery.com
>  > > http://xquery.com/mailman/listinfo/talk
>  > >
>  >
> 
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