anchor.diff:    (:S1 --> #\( :S1 #\+ :F #\))
     (:F --> #'integerp))
   
  -(define-random-accept-test grammar-10-random-accept-test grammar-10-parser 50 :S
  +(define-random-test grammar-10-random-accept-test grammar-10-parser 50 :S t
     (:S --> :S1)
     (:S1 --> :F)
     (:S1 --> #\( :S1 #\+ :F #\))
  
positive.code: (define-test reject-tests ()
    (combine-results
      (grammar-8-reject-test)
      (grammar-9-reject-test)
      (grammar-10-reject-test)
      (grammar-11-reject-test)
  
negative.code:        collect rule
         end)))
  
  (defmacro define-random-test (test-name parser-name number start-symbol accept-reject-p &body rules)
    (let ((cases nil)
  	(rstate (sb-ext:seed-random-state 1))
  	(count (eval number))
  