Re: Re: How to express this in XPath: "when condition

Hi Roger ---

On Tue, Dec 20, 2022 at 02:20:26PM -0000, Roger L Costello
costello@xxxxxxxxx scripsit:
> I am implementing an application that processes a sequence of XPath
> expressions. Some XPath expressions can be evaluated immediately
> because all the data is present in full. However, in some cases not
> all the data is present in full. In my car example, the decision to
> output the license plate number or null cannot be made until the
> relevant police report arrives, which may occur at some time in the
> future. So evaluating the XPath for the car example must pause until
> the police report arrives.

Or it could fail and be re-run periodically?

It makes sense that you want to wait on an external event before
returning a result.  In a declarative expresion language that avoids
side-effects, you're going to have to fight with it a lot if you try to
implement that in a literal way.

What happens if the police report never arrives?


-- 
Graydon Saunders  | graydonish@xxxxxxxxx
^fs oferiode, pisses swa mfg.
-- Deor  ("That passed, so may this.")