proposition: Fact symm_sym sh : symm_pol sh \is symmetric.
proof: Proof. apply/issymP => s; apply/mpolyP => m. rewrite mcoeff_sym !mcoeff_symm_pol. have: perm_eq (m#s) m by apply/tuple_permP; exists s. by move=> /permPr ->. 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