[XSL-LIST Mailing List Archive Home] [By Thread] [By Date]

Re: [xsl] Casting single-item sequences to atomic values


Subject: Re: [xsl] Casting single-item sequences to atomic values
From: Wendell Piez <wapiez@xxxxxxxxxxxxxxx>
Date: Tue, 8 Apr 2014 09:42:17 -0400

Christian,

This is easy to find in the spec ... if you look at the right spec. :-)

http://www.w3.org/TR/xpath-datamodel/#sequences

Cheers, Wendell


On Mon, Apr 7, 2014 at 8:31 PM, Christian Roth <roth@xxxxxxxxxxxxxx> wrote:
> Hi,
>
> why is
>
>   (1) cast as xs:integer == 1
>
> Or is it?
>
> I hit upon this while trying to understand why this works:
>
>   subsequence( ('a','b'), (1), 1)
>
> subsequence() expects an xs:double as its second parameter, but not a
single-item _sequence_ of xs:double's. Because it works, "(1) cast as
xs:double" must be equivalent to "1 cast as xs:double", and therefore "(1) =
1".
>
> Why I got that much confused is my following thinking on the description of
"cast" at <http://www.w3.org/TR/xpath20/#id-cast>.
>
> It says:
>
>> 1. Atomization is performed on the input expression.
>
> With fn:data( (1) ) returning the sequence of atomized values of each of its
input sequence's members, this IMO yields (1).
>
>> 2. If the result of atomization is a sequence of more than one atomic
valueb&
>
> Does not apply.
>
>> 3. If the result of atomization is an empty sequence: b&
>
> Does not apply.
>
>> 4. If the result of atomization is a single atomic valueb&
>
> Also does not apply in my thinking, as I get a _sequence_ of a single atomic
value. There's no step that tackles the case where the result of atomization
is a sequence of a single atomic value.
>
> Therefore, I guess that a single-atomic-valued-item sequence is the same (or
equivalent?) as its single atomic member. I vaguely remember reading that long
time ago somewhere in the spec, but cannot find it now. Can someone please
point me to the relevant section? Thanks!
>
> Regards
> Christian
>



--
Wendell Piez | http://www.wendellpiez.com
XML | XSLT | electronic publishing
Eat Your Vegetables
_____oo_________o_o___ooooo____ooooooo_^


Current Thread
Keywords