Re: [xsl] XPath expression to check that there are no intervening elements?

Subject: Re: [xsl] XPath expression to check that there are no intervening elements?
From: "G. Ken Holman g.ken.holman@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
Date: Tue, 19 Jul 2016 16:43:59 -0000
Okay ... I wonder if this might be fastest of all:

B and not( B[1]/following-sibling::*[not(self::B)][1]/following-sibling::B )

for "there is a B, and starting from it there is no following sibling non-B that has a following sibling B. No counting and no looking backwards.

. . . . . . Ken

At 2016-07-19 16:36 +0000, Dimitre Novatchev dnovatchev@xxxxxxxxx wrote:

To avoid the false true when there are no Bs at all:


XPath 1.0: B and not(B[1]/following-sibling::node()[not(position() > ../count(B))][not(self::B)])


XPath 2.0: B and not(node()[. >> ../B[1] and . << ../B[last()]][not(self::B)])

On Tue, Jul 19, 2016 at 9:29 AM, Dimitre Novatchev <dnovatchev@xxxxxxxxx> wrote:
> XPath 1.0:
>
> not(B[1]/following-sibling::node()[not(position() >
> ../count(B))][not(self::B)])
>
> XPath 2.0:
>
> not(node()[. >> ../B[1] and . << ../B[last()]][not(self::B)])
>
> Cheers,
> Dimitre
>
> On Tue, Jul 19, 2016 at 9:16 AM, G. Ken Holman g.ken.holman@xxxxxxxxx
> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>> I like Mike's answer for XSLT 2.
>>
>> Your XSLT 1 solution can be improved by reducing the number of counting
>> actions. Your solution has three uses of count() ... this has only two:
>>
>> count(B[last()]/preceding-sibling::*[not(self::B)]) =
>> count(B[1]/preceding-sibling::*[not(self::B)])
>>
>> Avoiding the use of counting you could do the following:
>>
>> string( generate-id( B[1]/preceding-sibling::*[not(self::B)][1] ) ) =
>> string( generate-id( B[last()]/preceding-sibling::*[not(self::B)][1] ) )
>>
>> The use of string() is necessary in case the sequence of children starts
>> with B.
>>
>> Come to think of it, neither your answer, Mike's answer nor my answer will
>> work if there are no B children at all. You will get a false positive.
>> Does your test need to accommodate that situation?
>>
>> . . . . . . . . Ken
>>
>> At 2016-07-19 15:44 +0000, Costello, Roger L. costello@xxxxxxxxx wrote:
>>>
>>> Hi Folks,
>>>
>>> This XML has a solid block of <B> elements:
>>>
>>> <Document>
>>> <A/>
>>> <B/>
>>> <B/>
>>> </Document>
>>>
>>> This XML has an intervening <C> element:
>>>
>>> <Document>
>>> <A/>
>>> <B/>
>>> <C/>
>>> <B/>
>>> </Document>
>>>
>>> I need an XPath expression to return a Boolean value:
>>>
>>> Return true if there is one solid block of <B> elements
>>> (no intervening elements).
>>> Otherwise, return false.
>>>
>>> I created a horrendous XPath expression to solve it:
>>>
>>> count(B) eq (B[last()]/count(preceding-sibling::*)+1 -
>>> B[1]/count(preceding-sibling::*))
>>>
>>> Can you provide a better (simpler, more efficient) XPath expression?
>>>
>>> /Roger
>>>


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