proposition: Lemma nonincn_inP : {in D, forall i, i.+1 \in D -> f i >= f i.+1} -> {in D &, {homo f : i j /~ i <= j}}.
proof: Proof. move=> /= f_dec; apply: homo_sym_in. by apply: homo_leq_in Dconvex 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)