Re: [Exist-development] bug @fn:string

[Pieter D. <pie...@gm...>]

On Mon, Aug 9, 2010 at 5:32 PM, Dmitriy Shabanov <sha...@gm...> wrote:
> On Mon, 2010-08-09 at 16:32 +0200, Pieter Deelen wrote:
>> xs:string(()) should yield ()
>
> It's confuse me, can you point spec.

http://www.w3.org/TR/xquery/#id-constructor-functions states (T is a
type, e.g., xs:string):
"The semantics of the constructor function call T($arg) are defined to
be equivalent to the expression (($arg) cast as T?)"

So xs:string(()) is equivalent to () cast as xs:string?.

http://www.w3.org/TR/xquery/#id-cast tells us what this means:
"If the result of atomization [of the input expression] is an empty sequence:
  1. If ? is specified after the target type, the result of the cast
expression is an empty sequence.
  2. If ? is not specified after the target type, a type error is
raised [err:XPTY0004]."

Hence, () cast as xs:string? evaluates to (). xs:string(()),
therefore, also evaluates to ().

Pieter