proposition: Lemma scalerAr (k : R) (x y : W) : k *: (x * y) = x * (k *: y).
proof: Proof. by apply: val_inj; rewrite !(linearZ, rmorphM)/= linearZ scalerAr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)