proposition: Lemma fdistC13E x : fdistC13 x = P (x.2, x.1.2, x.1.1).
proof: Proof. by rewrite /fdistC13 fdistC12E fdistXE fdistAE. Qed.
imports: mathcomp(all_ssreflect ssralg fingroup perm matrix) mathcomp(all_algebra vector reals normedtype) mathcomp(mathcomp_extra boolp) mathcomp(Rstruct) ssrR logb realType_ext ssr_ext ssralg_ext bigop_ext