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Michael Sperber <sperber@xxxxxxxxxxxxxxxxxxxxxxxxxxx> writes: >>>>>> "Will" == Will Fitzgerald <fitzgerald@xxxxxxxxxxxx> 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