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;; problem reported to pg but not checked -- test this!!!!!!!!!!
;; http://www.paulgraham.com/onlisperrata.html:
;; p. 156. In do-tuples/o the expression (1- (length parms)) should be
;; (- (length source) (length parms)).
;; Reported by Roland. (at netquant.com.br)
(defmacro do-tuples/o (parms source &body body)
  (if parms
      (let ((src (gensym)))
        `(prog ((,src ,source))
            (mapc (lambda ,parms ,@body)
                  ,@(map0-n (lambda (n)
                              `(nthcdr ,n ,src))
                            ;;(1- (length parms)) ;; error in text
                            (- (length source) (length parms)) ;; corrected

                            ))))))

CL-USER> (do-tuples/o (x y) '(a b c)
           (princ (list x y)))
(A B)(B C)
NIL

,@(map0-n (lambda (n)
            `(nthcdr ,n ,src))
          (- (length source) (length parms))