proposition: Lemma pr_eq_pairC a b : `Pr[ [% TY, TX] = (b, a) ] = `Pr[ [% TX, TY] = (a, b)].
proof: Proof. by rewrite !pr_eqE; congr Pr; apply/setP => u; rewrite !inE /= !xpair_eqE andbC. 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