proposition: Lemma eqn_double m n: (m.*2 == n.*2) = (m == n).
proof: Proof. by rewrite - !muln2 eqn_mul2r. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype) mathcomp(ssrnat seq path div) mathcomp(fintype tuple finfun bigop finset binomial)