proposition: Lemma occurs_spec : forall (v : nat) (t : Term), occurs v t = true <-> HasVar v t.
proof: Proof. pose_hasvar. pose proof Coq.Arith.EqNat.beq_nat_true. pose proof Coq.Arith.EqNat.beq_nat_false. induction t; sauto; unfold orb; try yelles 2. assert (occurs v t1 = true \/ occurs v t2 = true). Reconstr.reasy (@Coq.Bool.Bool.orb_prop) Reconstr.Empty. yelles 1. Qed.
imports: Hammer(Reconstr) PeanoNat Omega