anchor.diff:  ;;;; failure we stop running and report what values of the variables
   ;;;; caused the code to fail.
   
  +;;;; The generation of the random data is done using "generator
  +;;;; functions" (see below for details). A generator function is a
  +;;;; function which creates, based on user supplied parameters, a
  +;;;; function which returns random data. In order to facilitate
  +;;;; generating good random data the FOR-ALL macro also supports guard
  +;;;; conditions and creating one random input based on the values of
  +;;;; another (see the FOR-ALL macro for details).
  +
  +;;;; *** Public Interface to the Random Tester
  +
   (defparameter *num-trials* 100
     "Number of times we attempt to run the body of the FOR-ALL test.")
   
  
positive.code:   (catch 'run-once
      (bind-run-state ((result-list '()))
        (let ((values (mapcar #'funcall generators)))
          (apply body values)
          (cond
            ((null result-list)
             (throw 'run-once (list :no-tests)))
  
negative.code: ;;;; We provide a set of built-in generators.
  
  (defun gen-integer (&key (max (1+ most-positive-fixnum))
                           (min (1- most-negative-fixnum)))
    "Returns a generator which produces random integers greater
  than or equal to MIN and less than or equal to MIN."
    (lambda ()
  