English
Variant expression for coheight using head-based supremum.
Русский
Вариант выражения ко‑высоты через супремум по серий с head = a.
LaTeX
$$$\operatorname{coheight}(a) = \sup\{ \operatorname{length}(p) : p : LTSeries(\alpha), p.head = a \}. $$$
Lean4
/-- Variant of `coheight_le_iff` ranging only over those series that begin exactly on `a`.
-/
theorem coheight_le_iff' {a : α} {n : ℕ∞} : coheight a ≤ n ↔ ∀ ⦃p : LTSeries α⦄, p.head = a → p.length ≤ n := by
rw [coheight_eq_iSup_head_eq, iSup₂_le_iff]