proposition: Lemma tail_of_fdist_rV_fdist_rV n (P : fdist R A) : tail_of_fdist_rV (P `^ n.+1) = P `^ n.
proof: Proof. apply/fdist_ext => a; rewrite /tail_of_fdist_rV fdist_sndE /=. under eq_bigr. move=> v _; rewrite fdist_prod_of_rVE /= fdist_rVS. by rewrite row_mx_row_ord0 rbehead_row_mx; over. by rewrite -big_distrl /= FDist.f1 mul1r. 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