proposition: Lemma updiVm' x m xs : m > 0 -> x \notin dom (updi x.+m xs).
proof: Proof. elim: xs x m=>[|v vs IH] x m //= H. rewrite ptrA domPtUn inE /= negb_and negb_or -{4}(ptr0 x) ptrK -lt0n H /=. by rewrite orbC IH // addn1. Qed.
imports: mathcomp(ssreflect ssrfun ssrnat div ssrbool seq) LemmaOverloading(prelude finmap ordtype) mathcomp(path eqtype) Eqdep