RE: [xsl] Answers to review questions in "Beginning XSLT": Chapter 5

["Lars Huttar" <lars_huttar@xxxxxxx>]

Jeni Tennison wrote:

> Sent: Wednesday, March 12, 2003 7:09 AM
> 
> > For now I'm omitting the questions themselves, since I don't yet
> > have explicit permission to copy them. (Jeni, would that be OK?)
> 
> Yes, I'm sure that would be fine. It would also mean that people who
> don't have the book are able to understand what you're answering.

Thanks.  That will be helpful!

> > 1. No nodes match the select pattern, so no templates get applied,
> >    so there is no output for that apply-templates.
> 
> That's correct, though it would be more accurate to say that "no nodes
> get selected by the select expression". Remember that the select
> attribute (on <xsl:apply-templates>, and elsewhere) is for *selecting*
> things with an *expression* and the match attribute (on <xsl:template>
> and elsewhere) is for *matching* things with a *pattern*.

Thanks.  I have to admit the difference between the two is less than
crystal-clear in my mind.  Kay p. 430 and 433 are helpful.

> The wrapping <xsl:if> is actually superfluous. @flag = 'favorite' and
> @flag = 'interesting' obviously cannot be true if there is not flag
> attribute, but it is also the case that @flag != 'favorite' cannot be
> true if there is no flag attribute.

Oh yeah.  :-)  Haven't gotten used to that mental shift yet... that we
are actually making a query on a nodeset, rather than comparing a value
to a value.

> Perhaps you included the <xsl:if>
> so that all the instructions are ignored if the flag attribute doesn't
> exist.

Well, that was part of it too (efficiency in the case of no flag
attribute).

> > 10. ...

> You've answered a lot of this yourself in your follow-up mail. I don't
> think that there's a right answer to this question: it's more a prompt
> to get you to explore the properties of NaN, number(), boolean(),
> string() and comparison operators.

It worked!

> Personally, I usually use:
> 
>   string(number()) != 'NaN'
> 
> because it makes it clear what I'm actually testing:

Good point.

Thanks for the pointers!  This has been helpful.

Lars


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