proposition: Lemma sexit2 h1 h : def (h1 :+ h) -> (def h1 -> supdom h1 empty) -> supdom (h1 :+ h) h.
proof: Proof. move=>H1 H2; rewrite -{2}(un0h h); apply: subdomE=>//. by apply: H2; apply: defUnl H1. Qed.
imports: mathcomp(ssreflect ssrfun ssrnat div ssrbool seq) LemmaOverloading(prelude finmap ordtype) mathcomp(path eqtype) Eqdep