proposition: Lemma dE x : d x = P (x.1.1, x.1.2.1, x.1.2.2, x.2).
proof: Proof. case: x => -[a [b d] c]; rewrite /def.d fdistmapE /= -/(f (a, b, d, c)). by rewrite (big_pred1_inj inj_f). Qed.
imports: mathcomp(all_ssreflect ssralg matrix) Reals mathcomp(Rstruct) ssrR Reals_ext logb ssr_ext ssralg_ext bigop_ext fdist proba jfdist_cond