Re: check for whitespace value between nodes

On Fri, Aug 20, 2010 at 8:15 AM, Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>
wrote:
> Hi,
>
> At 04:07 PM 8/19/2010, Liam wrote:
>>
>> On Thu, 2010-08-19 at 12:58 -0500, a kusa wrote:
>> > Hi
>> >
>> > Is there any way in XSLT to check if the value between two nodes is a
>> > whitespace?
>> >
>> > I tried normalize-space(product/text()) !=' ' but that is not working.
>> > I want tocheck if the actual value between <product> </product> is a
>> > white space.
>>
>> Whitespace is a tricky thing to get right. It's impossible to give you a
>> good answer without knowing more about what you are trying to do and
>> why, and the context, and without seeing your XSLT.
>
> Problems relating to "whitespace" are more often underspecified than not.
> XML has a definition of "white space" (any space, carriage return, line
feed
> or tab character or run of such characters), but whether your definition in
> your problem aligns exactly with XML's is a different question. And even if
> it does, there are often other questions.
>
> For example, in the problem statement here, what does "a white space" mean?
> By one reasonable reading it matches "^\s$", while another has it match
> "^\s+$" as Liam suggests. (Other readings allow strings that match
neither.)
> Does a run of whitespace characters count as "a white space"?
>
> Dimitre's XPath 1.0 solution, "product/text() and
> not(normalize-space(product/text())", works with the second of these
> definitions, since a run of whitespace is collapsed by normalize-space()
> into an empty string (and then coerced to Boolean false). That is, the test
> is refactored to (a) the text node exists (the 'product' element is not
> empty), but (b) it has no value other than whitespace characters.
>
> For the first definition, one might want
>
> B translate(product/text(),'&#xA;&#x9;',' ')=' '
>
> (in XPath 1.0). This turns any LF or TAB into a space, then sees if the
> resulting string is a single space. (Ordinarily one doesn't have to worry
> about CR since it has already been normalized by a parser. But even this
> isn't always so.)

Hi Wendell,

In fact the expression I proposed also covers your "first definition".

Do note that there is only a single definition for whitespace in the
XML Recommendation (http://www.w3.org/TR/REC-xml/#sec-common-syn) :

[3]    S    ::=    (#x20 | #x9 | #xD | #xA)+

and this is exactly what the normalize-space() function handles
(http://www.w3.org/TR/xpath-functions/#func-normalize-space):

"Summary: Returns the value of $arg with whitespace normalized by
stripping leading and trailing whitespace and replacing sequences of
one or more than one whitespace character with a single space, #x20.

The whitespace characters are defined in the metasymbol S (Production
3) of [Extensible Markup Language (XML) 1.0 Recommendation (Third
Edition)]."



--
Cheers,
Dimitre Novatchev
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>
> Cheers,
> Wendell
>
>
>
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