proposition: Lemma abstr2_correct : forall (t s : Term) (v : nat), NoLambdas t -> abstr2 v t @ s =w csubst t v s.
proof: Proof. induction t; qsimpl. - sauto. - sauto. - use occurs_spec. rewrite csubst_novar by ssimpl. rewrite csubst_novar by ssimpl. strivial. Qed.
imports: Hammer(Tactics) Arith ZArith List Lia Hammer(Hints) Reals Lra Hammer(Reflect) Nat Psatz