Ltac pairInv :=
  match goal with 
    | [H : (_, _) = (_, _) |-_ ] => inversion H; clear H; subst
  end.Ltac destruct_exists :=
  match goal with
    | [H : exists x, _ |- _ ] =>
      destruct H
  end.

Theorem getSupport_In_Ret : forall (A : Set)(eqd : eq_dec A) x a, In x (getSupport (Ret eqd a)) -> x = a.