proposition: Lemma Schur_homog (d : nat) (la : 'P_d) : 's_la \is d.-homog.
proof: Proof. Proof using . rewrite Schur_tabsh_readingE /polylang /commword. apply rpred_sum => [[t Ht]] _ /=. move: Ht => /eqP <-; elim: t => [| s0 s IHs]/=. rewrite big_nil; exact: dhomog1. rewrite big_cons -(add1n (size s)); apply dhomogM; last exact: IHs. by rewrite dhomogX /= mdeg1. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(ssralg ssrint fingroup perm) mathcomp(mpoly) tools combclass ordtype sorted partition tableau skewpart skewtab antisym Schur_mpoly freeSchur therule std stdtab unitriginv presentSn