Section LOGIC.
Variable U : Set.
End LOGIC.
(** decide if there is a legal successor Ideally, I should have introduce a decidable predicate to decide if Delete transitions were permitted. *)

Lemma decide_no_copy_successor :
forall c : Config,
legal c ->
(exists t : class_trans c, ~ copy_p c t /\ legal (transition c t)) \/
(forall t : class_trans c, copy_p c t).