Re: [xsl] Question on predicate patterns in XSLT 3.0

["Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

> On 3 Sep 2016, at 12:22, Martin Honnen martin.honnen@xxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> When trying to use predicate patterns in XSLT 3.0
(https://www.w3.org/TR/xslt-30/#doc-xslt30-patterns-Pattern30) I was kind of
astonished that
>
>  .[predicate1][predicate2]
>
> and
>
>  .[predicate1 or predicate2]
>
> are allowed while it is not allowed to form a union of two predicate
patterns alike
>
>  .[predicate1] | .[predicate2]
>
> Why is a union of predicate patterns not allowed?

Because the "|" operator only applies to nodes, so this wouldn't mean what you
think it means -- especially as pattern matching is error-free, in other words
a type error here would lead to the pattern silently not matching.

Michael Kay
Saxonica