anchor.diff:     If the _name_ is not associated with an _agent_ an _error_ of _type_
      {simple-error} is signaled."
     (check-type name keyword)
  -  (with-lock-grabbed (*registry-lock*)
  +  (with-write-lock (*registry*/lock)
       (or (remhash name *registry*)
           (error "Not registered: ~a" name))))
   
  
positive.code:    {simple-error} is signaled."
    (check-type name keyword)
    (check-type agent agent)
    (with-lock-grabbed (*registry-lock*)
      (if #1=(gethash name *registry*)
          (error "~a is already registered." name)
          (setf #1# agent))))
  
negative.code: 
  (defvar *registry* (make-hash-table))
  
  (defvar *registry*/lock (make-read-write-lock))
  
  (defun register (name &optional (agent (agent)))
    "*Arguments and Values:*
  