• To: "'Jeni Tennison'" <jeni@j...>,"'bob mcwhirter'" <bob@w...>
• Subject: RE: Quick Xpath
• From: "Michael Kay" <michael.h.kay@n...>
• Date: Thu, 18 Jul 2002 09:31:35 +0100
• Cc: <xml-dev@l...>
• Importance: Normal
• In-reply-to: <175993040546.20020718003503@j...>
• Reply-to: <michael.h.kay@n...>

> > Howsabout given:
> >
> >         (//foo | //bar)[4]
> >
> > Would that be the 4th occurrence of either foo or bar, in document 
> > order?
> 
> Yes.
> 
> > That's just an implementational nightmare.
> 
> I can imagine, but unfortunately that's the way that it's 
> defined in the XPath Rec. Perhaps Mike and the other XPath 
> implementers on the list can share some implementation tips.

Actually it can very easily be optimized to (//*[self::foo or
self::bar])[4], which can be evaluated serially with no sort, stopping
when the fourth matching node is found. 

Saxon doesn't do that, but it wouldn't be difficult.

Michael Kay
Software AG
home: Michael.H.Kay@n...
work: Michael.Kay@s... 

• References:
  • Re: Quick Xpath
    • From: Jeni Tennison <jeni@j...>

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