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