(defun zeror  (n tbl &key (verbose t))
  (labels ((trainer  (tbl cautions egs)
             (table-majority-class tbl egs))
           (tester   (tbl cautions majority one)
             (cons majority  (isa one tbl))))
   (n-way n tbl
          :verbose verbose
          :trainer  #'trainer
          :tester   #'tester)))

(deftest test-zeror ()
  (let ((tmp (zeror 3 (weather) :verbose nil)))
    (check
      (samep tmp "(
      #(ABCD :FOR 2
       :A 0 :B 10 :C 0 :D 18
       :ACC .64 :PD .64 :PF .00 :PREC  1.00
       :F .00 :BAL .75)
      #(ABCD :FOR 1
       :A 18 :B 0 :C 10 :D 0
       :ACC .64 :PD .00 :PF .36 :PREC .00
       :F .00 :BAL .25))"))))