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+import Common.Finite
+
+class Countable (α : Type u) where
+  enumerate : α → Nat
+  injective {a b : α} : enumerate a = enumerate b → a = b
+
+instance {α : Type u} [Finite α] : Countable α where
+  enumerate := Fin.val ∘ Finite.enumerate
+  injective :=  Finite.injective ∘ Fin.val_inj.mp