RE: No convenient way to cast one expression to the same type as another?

> Given two opaque expressions $x and $y, does XQuery have a convenient 
> expression that converts $x to the same (dynamic or static) 
> type as $y?

No, I don't think it does. I think we should consider this when and if we
provide instrospection (types as first class objects) in a future version of
the language.

Michael Kay


> 
> I can write a gnarly (60+ lines, just to handle singletons) 
> typeswitch that 
> converts $x to the dynamic type of $y, provided I'm willing 
> to settle for the 
> built-in XQuery types only.  I haven't found any way to 
> handle user-defined 
> types, or to convert $x to the static type of $y.
> 
> Strangely, this operation does come up (at least for dynamic 
> types); for 
> example, the general comparison operators perform this conversion on 
> xdt:untypedAtomic values in some cases.
> 
> Perhaps there should be a built-in function like 
> convert-to-same-type-as($exprToConvert as item*, $type as 
> item*) as item* ?
> 
> Cheers,
> 
> Michael Brundage
> Writing as
> Author, "XQuery: The XML Query Language" (Addison-Wesley, to 
> appear 2003) Co-author, "Professional XML Databases" (Wrox 
> Press, 2000)
> 
> not as
> Technical Lead
> Common Query Runtime/XML Query Processing
> WebData XML Team
> Microsoft
>

Received on Monday, 9 June 2003 10:41:47 UTC