proposition: Lemma mapk_ins k v s : path ord k (supp s) -> mapk (ins k v s) = ins (f k) v (mapk s).
proof: Proof. by move=> H; rewrite /mapk foldf_ins =>//. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path) pcm(options)