Will Fitzgerald <fitzgerald@neodesic.com>
Doug Currie 11 Jan 1999 19:09 UTC
Michael Sperber <xxxxxx@Informatik.Uni-Tuebingen.De> writes:
>>>>>> "Will" == Will Fitzgerald <xxxxxx@neodesic.com> writes:
>
>Will> May I suggest the following addition to the SRFI-1 list library,
>Will> Common Lisp's LDIFF:
>
>Will> I think a reasonable definition is:
>Will> [...]
>[...]
>Could you suggest possible uses for this procedure?
The following gem is by Duncan Smith...
(defun permute (ls)
(if (null ls)
nil
(if (null (cdr ls))
(list ls)
(mapcon
#'(lambda (x)
(mapcar
#'(lambda (y)
(cons (car x) y))
(permute (nconc (ldiff ls x) (cdr x)))))
ls))))
e