Re: [F&O] CER-07 exactly-one et al

Those functions type-check their arguments but don't change the static type
of the expression.

I think you want:

define function exactly-one ( $items as item()* ) as item() {
   $items treat as item()
}

define function one-or-more ( $items as item()* ) as item()? {
   $items treat as item()?
}

define function zero-or-more ( $items as item()* ) as item()* {
   $items treat as item()*
}

which should take any sequence of items, change their cardinality
statically, and error dynamically if the cardinality change is not valid.


Cheers,

Michael Brundage
xquery@comcast.net

Writing as
Author, XQuery: The XML Query Language (Addison-Wesley, 2004)
Co-author, Professional XML Databases (Wrox Press, 2000)

not as
Technical Lead
Common Query Runtime/XML Query Processing
WebData XML Team
Microsoft


On 2/17/04 10:16 AM, "Mary Holstege" <mary@cerisent.com> wrote:
>> How can a user write a function that statically reduces the type and
>> raises an error if the dynamic cardinality is too big?
>> Best regards
>> Michael
> 
> Perhaps I'm missing something, but I don't see why these don't do the
> trick.
> The rules for sequence type matching allow you to report this either
> statically
> or dynamically:
> 
> 
> define function exactly-one ( $items as item() ) as item()*
> {
>  $items
> }
> 
> define function one-or-more ( $items as item()+ ) as item()*
> {
>  $items
> }
> 
> define function zero-or-more ( $items as item()* ) as item()*
> {
>  $items
> }
> 
> //Mary
>

Received on Tuesday, 17 February 2004 14:01:12 UTC