English
The simplifications yield variants of orderTop_neg; negation preserves orderTop in standard simplifications.
Русский
Упрощения дают варианты orderTop_neg; отрицание сохраняет orderTop в стандартных упрощениях.
LaTeX
$$$$ \operatorname{orderTop}(-x) = \operatorname{orderTop}(x). $$$$
Lean4
@[simp]
theorem order_neg [Zero Γ] {f : HahnSeries Γ R} : (-f).order = f.order := by
classical
by_cases hf : f = 0
· simp only [hf, neg_zero]
simp only [order, support_neg, neg_eq_zero]