[luatex] node missing

[Andreas Matthias]

Paul Isambert wrote:

> Andreas Matthias <andreas.matthias at gmail.com> a écrit:
>> 
>> In the following example I expected \mybox to contain `abc'
>> eventually. Instead it only contains `bc'. Why is the `a'
>> missing?
> 
> You must assign n1 to box.head, as in
> 
> [...]
>       n1.next = box.head
>       box.head = n1       
>       tail = node.slide(n1)
> [...]
> 
> otherwise the box still points to its former head as its first node
> (which has indeed n1 as its prev node, but it is ignored because scanning
> begins at the former head).


Hmm. I see it's working now but I still don't understand why.

Function foo creates and returns an hlist `h' and I thought this
hlist would be assigned to mybox with

   tex.setbox(mybox, foo(tex.box.mybox))

Hlist `h' does not contain the original box but the interior of
the box, does it? Then why do I have to set box.head?


Ciao
Andreas