proposition: Lemma can2_linear f' : cancel f f' -> cancel f' f -> linear f'.
proof: Proof. by move=> fK f'K a x y /=; apply: (canLR fK); rewrite linearP !f'K. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)