proposition: Lemma oevFA a ks f z0 : oeval a ks f z0 = oeval (fun r k v => if k \in dom f then a r k v else r) ks f z0.
proof: Proof. elim: ks a z0=>[|k ks IH] a z0 //=. by case E: (find k f)=>[b|] //; rewrite (find_some E). Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)