Re: [xsl] Getting Unexpected Results from .//* = $set-of-elements

I updated my code to use exists(. intersect 
$elements-to-keep/ancestor-or-self::*) and that definitely works and I like 
having a singleton on one side, but even my largest input document would not be 
large enough to show a significant performance benefit.

Cheers,

Eliot
--
Eliot Kimber
http://contrext.com
 
On 2/24/18, 2:37 PM, "Michael Kay mike(_at_)saxonica(_dot_)com" 
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:

    Your requirement is 
    
    IF any descendant of current element is in $elements-to-keep, process the 
current element
    
    and I suggested
    
    > select="exists(.//* intersect $elements-to-keep)"
    
    But I suspect the following would be better:
    
    > select="exists(. intersect $elements-to-keep/ancestor-or-self::*)"
    
    (That is, "if the current element is an ancestor-or-self of any element in 
$elements-to-keep)
    
    Enumerating the ancestors of an element is likely to be faster than 
enumerating its descendants. Saxon also has a faster implementation of 
"intersect" for use when one operand is a singleton.
    
    But if you want to return false when "." is in $elements-to-keep (but none 
of its descendants is) then you may need to tweak this slightly
    
    
    Michael Kay
    Saxonica
    
    > On 24 Feb 2018, at 20:17, Eliot Kimber ekimber(_at_)contrext(_dot_)com 
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
    > 
    > So my misunderstanding of "=" is that it is comparing values, not 
nodes--I clearly never understood that properly.
    > 
    > That then explains why an empty element would produce the results I was 
seeing: "" is equal to any other empty node.
    > 
    > Doh!
    > 
    > I will try Mike's intersection expression.
    > 
    > Cheers
    > 
    > W.
    > 
    > --
    > Eliot Kimber
    > http://contrext.com
    > 
    > On 2/23/18, 6:39 PM, "Michael Kay mike(_at_)saxonica(_dot_)com" 
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
    > 
    > 
    >> On 24 Feb 2018, at 00:18, G. Ken Holman 
g(_dot_)ken(_dot_)holman(_at_)gmail(_dot_)com 
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:
    >> 
    >> Ignore that second expression ... I wrote it too hastily and I'm now 
back at my desk to think about it.
    >> 
    >> This would work I think:
    >> 
    >> <xsl:value-of select="some $this in .//* satisfies
    >>                       some $that in $elements-to-keep
    >>                       satisfies $this is $that"/>
    >> 
    > 
    >    I think that's equivalent to saying that the intersection of the two 
sets is non empty:
    > 
    >    select="exists(.//* intersect $elements-to-keep)"
    > 
    >    Michael Kay
    >    Saxonica
    > 
    > 
    > 
    > 
    
    
    
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