Re: [xsl] Joining list fragments (was: Handling position in non-atomic sequences)

["Michael Kay mike@xxxxxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

> On 3 May 2020, at 09:54, gerrit.imsieke@xxxxxxxxx
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> This looks like a nested group-starting-with / group-adjacent to me at first
glance.

My reaction too. Of course the various options on xsl:for-each-group are
"stereotypes" - they handle 90% of grouping requirements but there are cases
they can't cope with, and in that case you have to go to lower-level
solutions. The "window" clause in XQuery is more powerful - perhaps it takes
you from the 90% level to 99%. There's also a small minority of cases where
XQuery's "for $x at $p in..." can be very valuable. But generally, anything
that involves manipulating a sequence using integer positions smells of
desperation, and makes one look hard to see if there isn't some better way.

Michael Kay
Saxonica

>
>
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> -----Original Message-----
> From: "Michael MC<ller-Hillebrand mmh@xxxxxxxxx"
<xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Sent: Sun, 03 May 2020 10:33
> Subject: Re: [xsl] Joining list fragments (was: Handling position in
non-atomic sequences)
>
> Am 02.05.2020 um 13:43 schrieb Michael Kay:
>>
>> You're talking about a solution, but I don't think you've told us what the
problem is. What are you trying to achieve?
>
> Fair enough,
>
> sometimes one is so deep wrapping onebs thoughts around a detail problem,
that the broader picture gets lost.
>
> We want to join list fragments and some content in between them. An HTML-ish
version of the input looks like this:
>
> 	<div>
> 		<h2 id="E2">Item with content to be joined follows div to collect</h2>
> 		<div>
> 			<ol data-meta="listlevel=start">
> 				<li>
> 					<p>1st item</p>
> 				</li>
> 			</ol>
> 			<div class="box" data-meta="collect">
> 				<p>Hint</p>
> 			</div>
> 			<ol data-meta="listlevel=continue">
> 				<li data-meta="listitem=continue">
> 					<p>Para ff</p>
> 				</li>
> 				<li>
> 					<p>2nd item</p>
> 				</li>
> 			</ol>
> 			<p>Other arbitrary content</p>
> 		</div>
> 	</div>
>
> Every broken list sequence starts with data-meta="listlevel=start" and a
list or a list item that is supposed to be joined with the start list is
marked using data-meta="listlevel=continue" and data-meta="listitem=continue".
There can be any number of collect items between lists and multiple continue
lists, but it is guaranteed that whatever needs to be collected will end with
a list. In DTD content model notation: startList, (collectItem*,
continueList)+
>
> The lists are not limited to a single level. Gladly, if there is a
"listitem=continue" in a continue list, it is guaranteed to be at the same
level the previous list ends.
>
> The task is to add to the last item of the previous list:
> * all content marked "collect" between the lists; other content would break
the process
> * content of the next listbs first list item if marked
"listitem=continue"
> The remaining content of each continue list would be added as additional
items to the start list.
>
> The desired result for the input data above would look like this:
>
> 	<div>
> 		<h2 id="E2">Item with content to be joined follows div to collect</h2>
> 		<div>
> 			<ol data-meta="listlevel=start">
> 				<li>
> 					<p>1st item</p>
> 					<div class="box" data-meta="collect">
> 						<p>Hint</p>
> 					</div>
> 					<p>Para ff</p>
> 				</li>
> 				<li>
> 					<p>2nd item</p>
> 				</li>
> 			</ol>
> 			<p>Other arbitrary content</p>
> 		</div>
> 	</div>
>
> All the "collect" content and continue lists are at the same hierarchical
level as the start list. So my initial strategy was to begin with the start
list and collect all "valid" siblings (collect, listlevel="continue") by
walking the following-sibling axis one by one. The result would be a sequence
of elements that have to be processed into the start list at various
locations.
>
> My original question was how to find the position of the next <ol> in that
sequence to easily use subsequence(). And I got some helpful pointers for that
(I even looked at xsltfunctions.com <http://xsltfunctions.com/>, but due to my
xsl:copy-of decision node identity seemed not to be an option), thanks a lot!
>
> But currently I am doubting my general strategy and I have the feeling I am
missing one very obvious thing. The task is basic tree transformation, and my
current ideas all look very complicated. For the simplified data I cannot yet
share XSLT code.
>
> Basically I use a mode to process the continue lists and their items. Within
each template I add special handling for "continue" content (ignoring the
elements, just processing their content). For the very last item in each list
I add rules to process the collect elements. Getting to the content of a <li
data-meta="listitem=continue"> and making sure it is processed only once is
where I am stuck at.
>
> Currently I think of putting more effort in the collect phase, e.g. to
already split continue lists in two parts: the continue item, which is then
easily processed with the collect items, and the rest of the list, which will
always be new items or sub-lists.
>
> Pointers if anyone has had success for a problem like this, would be very
welcome. (And I wonder if I have to deal with position in element sequences at
all.)
>
> - Michael MC<ller-Hillebrand
>
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