proposition: Fact polY_XY_is_linear : linear polY_XY.
proof: Proof. rewrite /polY_XY => r /= p q. rewrite scale_polXYE /polXY_scale /= -!mul_mpolyC. by rewrite raddfD /= rmorphM. Qed.
imports: HB(structures) mathcomp(all_ssreflect) mathcomp(ssrint rat ssralg ssrnum algC matrix vector) mathcomp(mpoly) tools partition ordtype antisym Schur_mpoly Schur_altdef sympoly homogsym permcent