[xquery-talk] simple map operator

[Jens Østergaard Petersen]

Thanks, Michael,

If the simple map operator "does not locate any special nodes within trees, but works on sequences of items you specify by expressions", does that not make it into a sequence expression in the terms of Michael Kay's Reference, Chapter 10 (which also has "/" as a simple mapping expression when it works on atomic values)? Also, the draft defines a path expression as something that "can be used to locate nodes within trees", so I still wonder what the meaning behind this categorisation is.

Cheers,

Jens

On Jul 9, 2012, at 10:01 AM, Michael Seiferle wrote:

> Hi Jens, 
> 
> they are relative, such that each step (E1 ! E2) will serve as the input sequence E'1 for the next operation (E'1 ! E'2), hence:
> 
>> <foo>
>>  <bar>hello</bar>
>>  <bar>world</bar>
>>  <bar>and</bar>
>>  <bar>hello</bar>
>>  <bar>universe</bar>
>> </foo>/bar ! (: here we locate each <bar /> child of <foo /> :)
>>    upper-case(.) !  (: we return a sequence of their text() in upper-case :)
>>          substring(.,2,string-length(.)) (: we return a sequence of the upper case text and strip the first character :)
> the map operator redefines the context items (inner focus) for each subsequent operation. 
> 
> So it does not locate any special nodes within trees, but works on sequences of items you specify by expressions, for example:
>> (1 to 5) ! (. + 1) ! (. * 2)
> will work as well and returns (4, 6, 8, 10, 12).
> 
> Hope this helped to clear things up a little :-).
> I guess others on this list will correct me if I got something wrong.
> 
> Kind regards
> 
> Michael
> 
> 
> 
> Am 09.07.2012 um 09:41 schrieb Jens Østergaard Petersen:
> 
>> Hi,
>> 
>> Can anyone explain to me why the XQuery 3.0 simple map operator <http://www.w3.org/TR/xquery-30/#id-map-operator> is a relative path expression? Which nodes within trees does it locate?
>> 
>> Thanks in advance for any enlightenment,
>> 
>> Jens
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>