Hello Philipp,

 > > 
 > > Listing expandable functions was not done to start with, and so I'm
 > > sure this is not the only missing item. (Again, a proper re-write
 > > would probably help here.) On \exp_arg:x, it got taken out of the main
 > > part of expl3 recently (it was supposed to be a wrapper for \expanded,
 > > but as pdfTeX 1.50 does not seem likely as a release we've dropped
 > > it.) I thought we'd removed it from the docs: can you point it out to
 > > me in the current CTAN snapshot|?
 > 
 > I think this should be reimplemented because everybody needs it. I tried to
 > write a small package only with expl3 and xparse, but I still needed an
 > implementation of \exp_arg:x. The l3expan module helps a bit, but there is
 > simply nothing as general and powerful as \edef. Maybe you could define two
 > macros, one expandable and one unexpandable.

you lost me here. Either you or I are stitting on top of a big
misunderstanding I think :-) please explain what you need \exp_arg:x for and
why the l3expan module doesn't help - that module is triple powerful to
whatever you had for expansion in 2e so ..

perhaps it is simply a misunderstanding how the l3expan module should/could
be applied --- or there is something we totally missed

frank