proposition: Fact polX_XY_is_linear : linear polX_XY.
proof: Proof. rewrite /polX_XY => r /= p q. rewrite /map_mpoly mmapD mmapZ /=. by rewrite scale_polXYE /polXY_scale /= -!mul_mpolyC. 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