English
The lexicographic top of a sum is the top of the right component.
Русский
Лексикографическая верхняя граница суммы — верхняя граница справа.
LaTeX
$$$\\text{OrderTop}(\\alpha \\oplus_ℓ \\beta)$ with top = inr ⊤$$
Lean4
/-- The lexicographical top of a sum is the top of the right component. -/
instance orderTop [LE α] [LE β] [OrderTop β] : OrderTop (α ⊕ₗ β)
where
top := inr ⊤
le_top := by
rintro (a | b)
· exact Lex.sep _ _
· exact Lex.inr le_top