proposition: Lemma cast_perm_inj m n eq_m_n : injective (@cast_perm m n eq_m_n).
proof: Proof. exact: can_inj (cast_permK eq_m_n). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype tuple finfun bigop finset binomial) mathcomp(fingroup morphism)