(mod (M N)
    (include *standard-cl-21*)
    (include prepend.clinc)
    (include reverse.clinc)
    (include map.clinc)
    (include len.clinc)
    (include range.clinc)
    (include sort.clinc)
    (include assert.clinc)
    (include deep_compare.clinc)
    (include permutations.clinc)
    (include last.clinc)
    (include busy.clinc)
    (include all-in-list.clinc)
    (include print.clinc)

    (defun ! (x)
        (if x
            (* x (! (- x 1)))
            1
        )
    )
    (defun no_repeats_inner ((first . remainder))
        (if remainder
            (if (deep= first (f remainder))
                0
                (no_repeats_inner remainder)
            )
            1
        )
    )
    (defun no_repeats (mylist)
      (if mylist
        (no_repeats_inner (sort (lambda (a b) (= (deep_compare a b) -1)) mylist))
        1
      )
    )
    (assert
        ;; Is permutations expected to collapse equal alternatives when two of
        ;; the items to shuffle are equal?
        (= (* (! M) 4) (len (permutations (c 0 (range M)))))
        (busy
            (lambda (listlen)
                (assign 
                    mylist (range listlen)
                    permed (permutations mylist)
                    (assert
                        (= (len permed) (! listlen))
                        ;; ensure we didn't produce any permutations that have
                        ;; repeated elements in them, which would indicate that
                        ;; the permutation function misbehaved
                        (all-in-list (map (lambda (L) (no_repeats L)) permed))
                        (no_repeats permed)
                    )
                )
            )
            (reverse (range N))
            1
        )
        (deep= (permutations 0) (q ()))
        0
    )
)