proposition: Fact symh_sym d : symh_pol d \is symmetric.
proof: Proof. Proof using. apply/issymP => s; rewrite -mpolyP => m. by rewrite mcoeff_sym !mcoeff_symh_pol mdeg_mperm. 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