proposition: Lemma domPtX A (v : A) x : valid (x :-> v) -> x \in dom (x :-> v).
proof: Proof. by move=>D; rewrite -(unitR (x :-> v)) domPtUnX // unitR. Qed.
imports: Coq(ssreflect ssrbool ssrfun Eqdep) mathcomp(ssrnat eqtype seq path) pcm(options axioms finmap) pcm(pcm unionmap)