[xquery-talk] What does [.] do.

[Ihe Onwuka]

I am using one transformation for two different data sources with two
different schemas.

One site may call a resoure readingMaterial another site may call the
same concept a publication, but they are otherwise similar and you may
want to treat them as such.

(xs:string(readingMaterial),xs:string(publication))[.]

when you know they are mutually exclusive in your document but you
want to process them in the same way.



On Mon, Jan 27, 2014 at 2:45 PM, Michael Kay <mike at saxonica.com> wrote:
>
> On 27 Jan 2014, at 13:59, Ghislain Fourny <g at 28.io> wrote:
>
>> Hi Ihe,
>>
>> You are right that it is a filter expression.
>>
>> However, I think [.] is not very common in "real world" code, except maybe for very precise use cases (like filtering out empty strings, etc). Usually you would put either a position or a boolean predicate inside a filter expression -- not just a context item expression.
>>
>> What [.] does, if I am not missing anything, is that it only keeps:
>> 1. Numerics equal to their position in the left-hand-side sequence
>> and
>> 2. Non-numerics that have an Effective Boolean Value of true, like non-empty strings, nodes, the true boolean, etc.
>>
>
> I mention on p648 of my XSLT /XPath book that the expression
>
> some $s in $S satisfies CONDITION
>
> is equivalent to
>
> exists(for $s in $S return boolean(CONDITION)[.])
>
> though I don't suppose that really counts as a use case.
>
> I think the only case I've used in anger is probably count(tokenize($x, ' ')[.]) which eliminates the zero-length tokens that can arise at the start and/or end of the sequence.
>
> Michael Kay
> Saxonica
>
>