proposition: Lemma symm0 : 'm[[::]] = 1.
proof: Proof. Proof using. have /homog_symmE -> : (sympol (1 : {sympoly R[n]})) \is 0.-homog. by rewrite rmorph1 dhomog1. rewrite sum_symmE enum_intpartnE /enum_partn /= big_cons big_nil addr0. by rewrite mcoeff1 mpart0 eqxx scale1r. 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