English
X_q is endowed with AddGroupWithOne structure, extending the additive group structure and the natural casts.
Русский
X_q снабжен структурой AddGroupWithOne, расширяющей аддитивную группу и естественные отображения чисел.
LaTeX
$$$X_q\text{ carries an AddGroupWithOne structure compatible with the natural casts and the additive group structure.}$$$
Lean4
instance : AddGroupWithOne (X q) :=
{ inferInstanceAs (Monoid (X q)), inferInstanceAs (AddCommGroup (X q)),
inferInstanceAs (NatCast (X q)) with
natCast_zero := by ext <;> simp
natCast_succ := fun _ ↦ by ext <;> simp
intCast := fun n => ⟨n, 0⟩
intCast_ofNat := fun n => by ext <;> simp
intCast_negSucc := fun n => by ext <;> simp }