English
Another formulation about bind with infimum and principal operations: (f ⊔ 𝓟 s) bind g equals f.bind g ⊔ 𝓟 s.
Русский
Другая формулировка связывания с Inf и принципиалом: (f ⊔ 𝓟 s) bind g равно f.bind g ⊔ 𝓟 s.
LaTeX
$$$(f \\sqcup \\mathcal{P} s) \\!\\mathrm{bind}\\ g = f \\mathrm{bind}\\ g \\sqcup \\mathcal{P} s$$
Lean4
theorem bind_inf_principal {f : Filter α} {g : α → Filter β} {s : Set β} :
(f.bind fun x => g x ⊓ 𝓟 s) = f.bind g ⊓ 𝓟 s :=
Filter.ext fun s => by simp only [mem_bind, mem_inf_principal]