FW: Optimisation (was Re[6]: Aggregate)

-----Original Message-----
From: Kay Michael 
Sent: 17 November 2000 17:17
To: 'Jeni Tennison'
Subject: RE: Optimisation (was Re[6]: Aggregate)


> Does Saxon recognise XPaths with more than one predicate to apply
> this?  For example:
> 
>   $x[foo][1]
>   $x[1][foo]
>   $x[foo][1][bar]
> 
For expressions it works with any number of predicates. In fact it works for
any numeric predicate whose value doesn't depend on the context node or
context position (it just terminates the loop when a matching node is
found). So $x[$y] where $y is numeric will also work.

For patterns there's a similar optimisation, but this applies only to
patterns of the form para[1], with a single predicate having the constant
value 1, but appearing anywhere in the path, e.g. section[1]/para[1]/@name
is fine.

Mike Kay 


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