[luatex] Behavior of node lists.

Thu Nov 8 22:21:42 CET 2012

Am 08.11.2012 11:40, schrieb Hans Hagen:
> On 11/8/2012 9:15 AM, Taco Hoekwater wrote:
>> On 11/07/2012 07:37 PM, Stephan Hennig wrote:
>>>
>>> If N is known to be non-nil, e.g., a glyph node, is it save to call
>>>
>>>    node.insert_after(nil, N, x)  ?
>>>
>>> If the answer is 'Yes',
>>
>> Well, yes.

Thanks!  Could that be clarified in the manual, please?  Made me wonder
why head were needed to insert a node after another node the first time
I read it.

>> However I do not like the idea of reordering the arguments,

No problem.  But let me respond to your arguments anyway.

>> because we have quite a lot of functions with 'head' argument, and 
>> they always come first.

I don't think this is a fair argument.  In node.insert_after, parameter
head plays only a secondary role.  It is only used if current -- the
primary parameter -- is nil.  And even then,

  insert_after(head, nil, new)

is just an opaque way of saying

  insert_after(nil, node.tail(head), new)

That is, the first argument <head> is actually never needed.  Though, on
the former line, you can't easily tell what happens, just from the
arguments.  You need to know about the current == nil case.  And I
guess, insert_after calls node.tail(head) behind the scenes anyway when
current == nil.  The current function insert_after is making things more
complicated than necessary, I think.  Am I missing something?

> indeed reordering in no option
> 
> (we could consider a two argument variant i.e. if two arguments, then 
> assume N, x)

At the cost of an additional argument check.  Undesirable as well ...

Best regards,
Stephan Hennig