English
The order of C(r) is 0 for all r; the constant Hahn series has its lowest exponent at 0 when nonzero (and is defined to have order 0 when zero).
Русский
Порядок C(r) равен 0 для любого r; если C(r) ненулевой, то минимальная степень равна 0; если же C(r)=0, порядок по convention равен 0.
LaTeX
$$$ \operatorname{order}(C(r)) = 0 \quad \text{для всех } r \in R $$$
Lean4
theorem order_C {r : R} : order (C r : HahnSeries Γ R) = 0 :=
by
by_cases h : r = 0
· rw [h, C_zero, order_zero]
· exact order_single h