proposition: Lemma exp_cst mu r : \E_[mu] (fun _ => r) = \P_[mu] predT * r.
proof: Proof. by rewrite pr_predT psum_sum // [RHS]mulrC -sumZ; apply/eq_sum. Qed.
imports: mathcomp(all_ssreflect all_algebra) mathcomp.classical(boolp classical_sets mathcomp_extra) xfinmap ereal reals discrete topology realseq realsum