proposition: Lemma swapXY_is_additive : additive swapXY.
proof: Proof. by move=> u v; rewrite unlock rmorphB !hornerE. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype choice ssrnat seq) mathcomp(fintype tuple finfun bigop fingroup perm div) mathcomp(ssralg zmodp matrix mxalgebra) mathcomp(poly polydiv mxpoly binomial)