proposition: Lemma dealloc_sfmono : safe_mono dealloc_pre.
proof: Proof. move=>i j; rewrite /dealloc_pre -!toPredE /= => Hx Vij. by rewrite domUn inE Vij Hx. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun ssrnat eqtype seq) pcm(options axioms pred prelude) pcm(pcm unionmap heap) htt(domain)