Re: Seek an XPath 2.0 expression that handles an empty

On 22 September 2016 at 23:12, Graydon graydon@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
> On Thu, Sep 22, 2016 at 04:01:39PM -0000, G. Ken Holman g.ken.holman@xxxxxxxxx scripsit:
>> At 2016-09-22 15:55 +0000, Costello, Roger L. costello@xxxxxxxxx wrote:
>> > I want an XPath 2.0 expression that outputs "do action" if the B field
>> > is empty, regardless of which of the two XML representations is used.
>> > This XPath expression seems to work:
>> >
>> > if (not(B) or B eq '') then "do action" else "no action"
>>
>> This gives you the same result:
>>
>> if (not(string(B))) then "do action" else "no action"
>
> You could also use
>
> if (not(boolean(B))) then "do action" else "no action"
>
> which exploits empty strings being false().

no, to get the string behaviour need the version you quoted with not(string(B))
not(boolean(B)) is the same as not(B) and (in the absence of schema typing)
is false if B is present but empty.

David

>
> Though that's definitely the sort of logic that should get a comment
> explaining to your future self what you're going.
>
> -- Graydon