proposition: Lemma scalerDl v : {morph scaleW^~ v : a b / a + b}.
proof: Proof. by move=> a b; apply: val_inj; rewrite !(SubK, raddfD)/= !SubK scalerDl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)