proposition: Lemma consts_in_subst_consts X Y (kappa: X -> exp Y) c s: c ∈ consts (subst_consts kappa s) -> exists d, d ∈ consts s /\ c ∈ consts (kappa d).
proof: Proof. rewrite subst_consts_consts. unfold Consts; rewrite in_flat_map; intros [e []]; mapinj. exists x; intuition. Qed.
imports: Morphisms Lia List Undecidability.HOU(calculus.calculus)