proposition: Lemma E_add_RV : `E (X `+ Y) = `E X + `E Y.
proof: Proof. rewrite -big_split; apply eq_bigr => a _ /=; by rewrite -mulRDl. Qed.
imports: mathcomp(all_ssreflect ssralg ssrnum matrix) mathcomp(Rstruct reals) Reals Lra ssrR Reals_ext realType_ext logb ssr_ext ssralg_ext bigop_ext fdist