> On 14 Jun 2018, at 14:23, Eliot Kimber ekimber@xxxxxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> This seems to work:
>
>      <test>b1 in A: <xsl:value-of select="$B1/ancestor::* = $A"/></test>
>      <test>b2 in A: <xsl:value-of select="$B2/ancestor::* = $A"/></test>

Unfortunately that's a bug that can go undetected for a long time. You're
comparing the string-values of the two nodes, not their node identity. It will
usually give the right answer, but

(a) getting the string value of a node that's near the root of the tree can be
very expensive

(b) two nodes can have the same string value without being the same node

Michael Kay
Saxonica