Hi Reinhard and Farbrizio,
On SBCL you can install CFFI by executing the following lines:
(require 'asdf)
(require :asdf-install)
(asdf-install:install 'cffi)
You load it this way (e.g. in your .sbclrc):
(require 'asdf)
(asdf::oos 'asdf:load-op :cffi)
> Alternatvely, it may be an idea to use cffi together with the C version
> of donlp. But this seem sto be tricky as the function evaluation from
> the C code requires callbacks to Lisp.
This is how to expose Lisp functions as callbacks to C:
http://common-lisp.net/project/cffi/manual/cffi-manual.html#Callbacks
Best regards
Bruno Daniel