proposition: Lemma setf_catr f g k (v : V) : (f + g).[k <- v] = f + g.[k <- v].
proof: Proof. by rewrite catf_setr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)