anchor.diff:                        (error 'unification-failure
                                :format-control "Could not unify ~s with any process in ~s"
                                :format-arguments (list pattern processes))))
  -                  patterns)
  -          substitutions)))
  -
  -;;; FIXME: MATCH* (and the instances in all the process calculi) should return
  -;;;        (VALUES substitutions processes), not (LIST processes substitutions).
  +                  patterns)))
  +    (values substitutions processes)))
   
   (defgeneric match-local (pattern process &optional substitutions)
     (:method ((patterns list) (processes list)
  
positive.code:                                              substitutions)
                                 (setf substitutions subst)
                                 procs)
                               (destructuring-bind (procs subst)
                                   (match-list #'match-up
                                               (up-message-pattern pattern)
                                               (handler-case
  
negative.code: (defgeneric match (pattern process &optional substitutions)
    (:method ((pattern pattern) (process list)
              &optional (substitutions (make-empty-environment)))
      (values (match-local (local-message-pattern pattern)
                           process
                           substitutions)))
    (:method ((pattern pattern) (kell kell)
              &optional (substitutions (make-empty-environment)))
      (let ((processes (append (multiple-value-bind (subst procs)
                                   (match-list #'match-local
                                               (local-message-pattern pattern)
                                               (messages kell)
                                               substitutions)
                                 (setf substitutions subst)
                                 procs)
                               (multiple-value-bind (subst procs)
                                   (match-list #'match-down
                                               (down-message-pattern pattern)
                                               (apply #'compose-hash-tables
  