anchor.diff:      (error "The association ~A needs at least two endpoints." name))
     (assert (= 2 (length endpoints)) ()
             "Sorry, associations with more than two endpoints such ~
  -           as ~A are not implemented yet." name)
  +            as ~A are not implemented yet." name)
     (let* ((link-parameters (generate-link-parameters endpoints))
            (link-arguments  (generate-link-arguments  endpoints))
            (types           (loop :for endpoint :in endpoints
  
positive.code:     class))
  
  
  (defmacro define-association (name endpoints &rest options)
    "
  Define functions to manage the association:
  
negative.code:                              (length (remove-duplicates types))))
           (attach-args-permutations
            (and attachp (permutations (generate-attach-parameters endpoints))))
           (link            (scat name '-link))
           (unlink          (scat name '-unlink))
           (contains-p      (scat name '-contains-p)))
  
      `(progn
         ,@(loop
  