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

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Jay,

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:variable
  xsl:value-of select="''"

and

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.

Cheers,
Wendell


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc.                http://www.mulberrytech.com
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