proposition: Lemma nonincnP : (forall i, f i >= f i.+1) -> {homo f : i j /~ i <= j}.
proof: Proof. move=> /= f_dec; apply: homo_sym. by apply: homo_leq f_dec => //= ? ? ? ? /le_trans->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(path fintype tuple bigop finset div prime finfun) mathcomp(finset)