proposition: Lemma belast_last_take (j : 'I_n.+1) : fdist_belast_last_of_rV (fdist_take P (lift ord0 j)) = (fdist_prod_take PY j)`1.
proof: Proof. rewrite /fdist_belast_last_of_rV /fdist_take /fdist_fst /fdist_prod_take !fdistmap_comp. congr (fdistmap _ PY); rewrite boolp.funeqE => /= -[v b] /=; congr (_, _). - apply/rowP => i. by rewrite /rbelast !mxE !castmxE /=; congr (v _ _); exact: val_inj. - by rewrite /rlast mxE castmxE /=; congr (v _ _); exact: val_inj. 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