proposition: Lemma prod_gen_homog d (sh : 'P_d) : sympol 'g[sh] \is d.-homog.
proof: Proof. Proof using gen_homog. rewrite /prod_gen; case: sh => sh /= /andP[/eqP <- _] {d}. elim: sh => [| d sh IHsh] /=; first by rewrite big_nil /= dhomog1. by rewrite big_cons; apply dhomogM; first exact: gen_homog. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(ssralg ssrint fingroup perm) mathcomp(ssrcomplements freeg mpoly) sorted tools ordtype permuted partition skewpart composition Yamanouchi std tableau stdtab skewtab permcent antisym Schur_mpoly therule Schur_altdef unitriginv