English
Cast is injective: if m.cast = n.cast then m = n.
Русский
Приведение целых чисел инъективно: если m.cast = n.cast, то m = n.
LaTeX
$$$ \forall {\alpha} [AddGroupWithOne \alpha] [CharZero \alpha],\ (m,n : \mathbb{Z}),\ (m \text{ cast}) = (n \text{ cast}) \Rightarrow m = n.$$$
Lean4
@[simp, norm_cast]
theorem cast_inj : (m : α) = n ↔ m = n := by rw [← sub_eq_zero, ← cast_sub, cast_eq_zero, sub_eq_zero]