RE: [xsl] Grouping into a table (for vertical alignment)

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Hi Daniel,

At 11:01 PM 5/27/2004, you wrote:
> Thanks Wendell... trying to figure it out now :p
>
> >Jeni works through one of these in entry 12 in the FAQ
> >page at http://www.dpawson.co.uk/xsl/sect2/N4486.html#d4726e727.
>
> Looking at it too, entry 12 actually allows me to handle my problem without
> a <xsl:key> ...

That's right: it's the other technique I mentioned: the "forward walk" or 
"tree visitor". The key-based technique is just called "key-based 
positional grouping" (since the nodes are grouped based on their relative 
positions), although I like to call it "levitation".

The trade-off is that walking the tree explicitly makes for more complex 
templates that work in what, to a newbie, is a highly unorthodox way, since 
they use <xsl:apply-templates select="following-sibling::*[1]" 
mode="walk"/> or the like. Using keys is a bit more elegant in the XSLT, 
arguably, but lays the stress on that key declaration, whose XPath (as you 
saw) can be ... "ornate", let's say.


> I got a question on entry 17:
>
> > <xsl:apply-templates mode="inGroup"
> >   select="following-sibling::*[position() &lt; $vGroupLength]"/>
>
> "vGroupLength" is the number of elements in the group.
>
> How does the "position()" work when used in the above manner,
> is it just the "context position" within (1) the node list of only
> "following-sibling"
> or (2) a node list of all siblings? I guess the first, but I just want to
> confirm.

You are correct, it's the node list of the following siblings. (The context 
of a predicate is provided by the nodes and node-set the predicate operates 
on.)

But you don't actually want this as it groups by a count -- first three 
nodes, next three nodes, next three nodes -- or they could be in twelves or 
nineteens: you get the idea. Whereas you need to group based on what nodes' 
neighbors are (which is why your problem is a bit harder).

> I really appreciate all the help I am getting from this list. Thanks all.

Sure. You have a toughie, but it's been done. Digging in the archives for 
"forward walk" or "tree visitor" would be a way to learn more about the 
technique I did *not* explain (but which some say is easier: I dunno, if 
you understand keys I think they're about the same).

Cheers,
Wendell


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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