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Re: [xsl] xsl:if test = empty string, returns true

Subject: Re: [xsl] xsl:if test = empty string, returns true
From: Jorge <chocolate.camera@xxxxxxxxx>
Date: Tue, 15 May 2012 16:02:51 +0200

Thank you all so much for all the rather granular explanations.

One thing I tried unsuccessfully is finding a way to unequivocally see what
was coming out of the function, and what xsl:if was testing. Up until know I
have only played with XSLT using a general-purpose text editor and running
Saxon a zillion times.

When I started guessing that I was not quite understanding what exactly the
function was returning, I tried to find a visual debugger that could describe
it to me. I tried Oxygen Developer's demo, but could not find a way to do that
(i.e. showing me what exactly xsl:if was testing).

Any heads up on how or with what tool I could have noticed I was getting a
node and not a string (besides learning XSLT properly)? I use Mac OS X 10.7 so
I am limited by what works on this platform.


El 14/05/2012, a las 16:52, Michael Kay <mike@xxxxxxxxxxxx> escribis:

> You're not alone in finding this confusing. Some highly experienced people
have given you incorrect information on this thread.
>   <!-- Function to fetch value of a key-string pair in plist -->
>   <xsl:function name="me:metadata">
>       <xsl:param name="label"/>
>       <xsl:value-of
>   </xsl:function>
> This function is NOT returning a string, and it is NOT returning a document
node as some have suggested. It is returning a text node, because that is
what<xsl:value-of>  creates. Unlike xsl:variable, xsl:function does not wrap
the text node in a document node; in the absence of an "as" attribute on
xsl:function, it returns the text node unchanged.
> Although I always recommend using an "as" attribute on xsl:function and
xsl:param to make it clear what the inputs and output to the function are
expected to be, the simplest fix to this function is to change<xsl:value-of>
to<xsl:sequence>. It's a common mistake to use xsl:value-of when there is no
intention or need to create a text node. The normal default way of returning a
result from a function should be to use xsl:sequence.
>> Any idea why the test evaluates to true?
> The effective boolean value of a node is always true. In fact, Saxon can
work out that this function will always return a text node, and it will
probably therefore decide that the EBV of the function call is true without
even calling the function.
> Michael Kay
> Saxonica

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