proposition: Lemma domPtUnX A (v : A) x i : def (x :-> v :+ i) -> x \in dom (x :-> v :+ i).
proof: Proof. by move=>D; rewrite domPtUn inE /= D eq_refl. Qed.
imports: mathcomp(ssreflect ssrfun ssrnat div ssrbool seq) LemmaOverloading(prelude finmap ordtype) mathcomp(path eqtype) Eqdep