Jacek Generowicz <jacek.generowicz@[...].ch>  wrote in message news:<tyf8yevdgoz.fsf@[...].ch
> ...
>  I'm pretty sure that Scheme allows you
>  to do this without any restriction.

Indeed. I knew it was possible to redefine macros but I did not expect
it was possible to redefine "built-in" "globally" so easily:

 (define-macro (if c . args)
  ''surprise!)

(display (if #t 'true 'false)) ;=>  surprise

By "globally" I mean that everything that depends of "if" will be modified:

(display (when #t 1)) ;=>  surprise

which is a recipe for disasters. So I see the logic of the restriction
in Common Lisp.


           Michele Simionato