Hi Mosè,


   > Hi Uwe and all,
   > 2014-11-27 11:39 GMT+01:00 Uwe Brauer <oub@mat.ucm.es>:

   > I hope it's clear I wrote those messages in a hurry, just to give the idea.

I was going to write you. I changed nullp to null applied your old patch and
it did not work as expected. *However* your *new* patch

   > I changed my mind. I propose the attached patch which restores (full)
   > compatibility with the old version of LaTeX-label: the optioanl `type'
   > argument select the look up table to be used for the default prefix of
   > the label, if it's nil (or absent) you are always prompted for a
   > label.  AUCTeX code always uses the appropriate value for the type
   > argument, but users will also be able to force the insertion of the
   > label (or continue to use the old syntax of the function).

Works beautifully! Thanks for all your efforts, I appreciate it a lot. 
(I still prefer some days more of testing before trying to release a
Xemacs pkg)

Uwe