RE: [xsl] Can I use a boolean variable in an xsl:if test

Subject: RE: [xsl] Can I use a boolean variable in an xsl:if test
From: Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>
Date: Tue, 08 Feb 2005 16:01:48 -0500

At 03:11 PM 2/8/2005, you wrote:
> My guess is that newbies imagine xsl:value-of to be
> some kind of "evaluate" function. Of course what it
> really is, is an instruction to write a string to a
> result tree (to "the" result tree or to a
> result-tree-fragment, as the case may be). Since this
> is generally what we want to have happen to our
> results, there seems to be nothing to get confused
> about.
> Until it breaks, that is, because we're not writing it
> out, but doing something else with it instead. Like
> testing whether it's true, while imagining we're
> testing the expression that was evaluated for it.

I find that I stay out of hot water with xsl:value-of if I just remember
that it returns a string. If I use xsl:value-of on a string, I get a
string. If I use xsl:value-of on a node, I get a string representation of
that node. Either way, though, I get a string.

Yes, my wetware XSLT processor works the same way.

Of course, the string "" returns false() as a Boolean, whereas a result-tree-fragment with a root but nothing in it returns true(), so an extra refinement is required to keep the story really straight --

  xsl:value-of select="''"


xsl:variable select="''"

are coerced to true() and false() respectively, when we test them. The first adds the empty string to the root of an RTF bound to a variable; the second binds the string itself.


====================================================================== Wendell Piez mailto:wapiez@xxxxxxxxxxxxxxxx Mulberry Technologies, Inc. 17 West Jefferson Street Direct Phone: 301/315-9635 Suite 207 Phone: 301/315-9631 Rockville, MD 20850 Fax: 301/315-8285 ---------------------------------------------------------------------- Mulberry Technologies: A Consultancy Specializing in SGML and XML ======================================================================

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