Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!yale!Duchier-Denys
From: Duchier-Denys@cs.yale.edu (Denys Duchier)
Newsgroups: comp.lang.lisp
Subject: Re: Cartesian product
Message-ID: <56828@yale-celray.yale.UUCP>
Date: 13 Apr 89 02:30:40 GMT
References: <3677@sdsu.UUCP>
Sender: root@yale.UUCP
Reply-To: Duchier-Denys@cs.yale.edu (Denys Duchier)
Organization: Computer Science, Yale University, New Haven, CT 06520-2158
Lines: 15
In-reply-to: ucselx!maxc0186@sdsu

In article <3677@sdsu.UUCP>, ucselx!maxc0186@sdsu writes:
> Does anyone have a lisp function that performs the Cartesian product
> on a list, i.e.,
>   (CARTESIAN '((A B) (C D) (E F))) will return
>   ((A C E) (A C F) (A D E) (A D F) (B C E) (B C F) (B D E) (B D F))
> not necessarily in that order.

(DEFUN CARTESIAN (L)
  (COND ((NULL L) NIL)
        ((NULL (CDR L))
         (MAPCAR #'LIST (CAR L)))
        (T (MAPCAN #'(LAMBDA (X) (MAPCAR #'(LAMBDA (Y) (CONS Y X)) (CAR L)))
                   (CARTESIAN (CDR L))))))

--Denys