anchor.diff:            (append (messages-in process)
                     (kells-in process)
                     (triggers-in process)))
  -    (add-process (replace-variables (process trigger) mapping) (parent trigger))))
  +    (add-process (replace-variables process mapping) (parent trigger))))
   
   (defmethod activate-continuation (process)
       (remove-process process)
  
positive.code:                   (messages-in (continuation process))
                    (kells-in (continuation process))
                    (triggers-in (continuation process))))
      (psetf (process process) (replace-variables (process process) mapping ignored-vars)
             (continuation process) (replace-variables (continuation process) mapping
                                                       ignored-vars)))
    (:method (mapping (process trigger) &optional ignored-vars)
      (setf ignored-vars (append (bound-names (pattern process))
                                 (bound-variables (pattern process))
                                 ignored-vars))
      (warn "ignoring ~a" ignored-vars)
      (mapc (lambda (proc) (substitute-variables mapping proc ignored-vars))
            (append (messages-in (process process))
                    (kells-in (process process))
  
negative.code:       (reduce #'compose-processes (cons process substituted-processes)))))
  
  (defgeneric replace-name (name mapping &optional ignored-vars)
    (:method (name mapping &optional ignored-vars)
      (declare (ignore mapping ignored-vars))
      name)
    (:method ((name name-variable) mapping &optional ignored-vars)
  