English
If ι has a bottom element and α has a semilattice structure, then partialSups f ⊥ = f ⊥.
Русский
Если в ι есть ноль (нижняя граница) и α имеет структуру полуупорядочения, то partialSups f ⊥ = f ⊥.
LaTeX
$$$\\partialSups f \\; \\bot = f \\; \\bot$$$
Lean4
@[simp]
theorem partialSups_bot [PartialOrder ι] [LocallyFiniteOrder ι] [OrderBot ι] (f : ι → α) : partialSups f ⊥ = f ⊥ :=
by
simp only [partialSups_apply]
-- should we add a lemma `Finset.Iic_bot`?
suffices Iic (⊥ : ι) = {⊥} by simp only [this, sup'_singleton]
simp only [← coe_eq_singleton, coe_Iic, Set.Iic_bot]