proposition: Lemma it_up_ge X n (sigma: fin -> @exp X) x: x >= n -> it n up_exp_exp sigma x = ren_exp (plus n) (sigma (x - n)).
proof: Proof. intros; rewrite it_up_spec; destruct dec2; intuition idtac; lia. Qed.
imports: List Arith Lia Morphisms Undecidability.HOU(calculus.terms)