proposition: Fact pair_mulDl : left_distributive mul_pair +%R.
proof: Proof. by move=> x y z; congr (_, _); apply: mulrDl. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)