$match = true() for empty $match??

[Victor]

While debugging my stylesheet using XMLSpy, I got a really weird result:
<xsl:if test="$match = true()"> matches even if $match is an empty node
fragment. How can this be?

 

[Richard Tobin]

While debugging my stylesheet using XMLSpy, I got a really weird result:
<xsl:if test="$match = true()"> matches even if $match is an empty node
fragment. How can this be?

What do you mean by "empty node fragment"? Do you mean "empty node set",
"empty result tree fragment", or what?

If the value of $match is a node set, then "$match = true()" is true
if and only if the node set is non-empty.

If the value of $match is a result tree fragment, then it is
"equivalent to a node-set containing just a single root node" (section
11.2) so it is never empty and "$match = true()" is always true.

I suspect this is different in XSLT version 2, which might explain why
different versions of Saxon and Xalan give me different results when I
test it.

-- Richard

 

[Victor]

What do you mean by "empty node fragment"? Do you mean "empty node set",
"empty result tree fragment", or what?

If the value of $match is a node set, then "$match = true()" is true
if and only if the node set is non-empty.

If the value of $match is a result tree fragment, then it is
"equivalent to a node-set containing just a single root node" (section
11.2) so it is never empty and "$match = true()" is always true.

A-hah! Thank you, this seems to solve the mystery (especially since the
XSL spec says empty node sets equal false().