proposition: Lemma domPtX A (v : A) x : def (x :-> v) -> x \in dom (x :-> v).
proof: Proof. by move=>D; rewrite -(unh0 (x :-> v)) domPtUnX // unh0. Qed.
imports: mathcomp(ssreflect ssrfun ssrnat div ssrbool seq) LemmaOverloading(prelude finmap ordtype) mathcomp(path eqtype) Eqdep