Theorem: IsTopologicalBasis.iInf
File: Mathlib/Topology/Bases.lean

tactic: let _ := ⨅ i, t i
state_before: β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
⊢ IsTopologicalBasis {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}
state_after: β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
⊢ IsTopologicalBasis {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}

tactic: refine isTopologicalBasis_of_isOpen_of_nhds ?_ ?_
state_before: β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
⊢ IsTopologicalBasis {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}
state_after: case refine_1
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
⊢ ∀ u ∈ {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}, IsOpen u

case refine_2
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
⊢ ∀ (a : β) (u : Set β), a ∈ u → IsOpen u → ∃ v ∈ {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}, a ∈ v ∧ v ⊆ u

tactic: rintro - ⟨U, F, hU, rfl⟩
state_before: case refine_1
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
⊢ ∀ u ∈ {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}, IsOpen u
state_after: case refine_1.intro.intro.intro
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
U : ι → Set β
F : Finset ι
hU : ∀ i ∈ F, U i ∈ T i
⊢ IsOpen (⋂ i ∈ F, U i)

tactic: refine isOpen_biInter_finset fun i hi ↦
  (h_basis i).isOpen (t := t i) (hU i hi) |>.mono (iInf_le _ _)
state_before: case refine_1.intro.intro.intro
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
U : ι → Set β
F : Finset ι
hU : ∀ i ∈ F, U i ∈ T i
⊢ IsOpen (⋂ i ∈ F, U i)
state_after: no goals

tactic: intro a u ha hu
state_before: case refine_2
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
⊢ ∀ (a : β) (u : Set β), a ∈ u → IsOpen u → ∃ v ∈ {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}, a ∈ v ∧ v ⊆ u
state_after: case refine_2
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
⊢ ∃ v ∈ {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}, a ∈ v ∧ v ⊆ u

tactic: rcases (nhds_iInf (t := t) (a := a)).symm ▸ hasBasis_iInf'
  (fun i ↦ (h_basis i).nhds_hasBasis (t := t i)) |>.mem_iff.1 (hu.mem_nhds ha)
  with ⟨⟨F, U⟩, ⟨hF, hU⟩, hUu⟩
state_before: case refine_2
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
⊢ ∃ v ∈ {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}, a ∈ v ∧ v ⊆ u
state_after: case refine_2.intro.mk.intro.intro
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
F : Set ι
U : ι → Set β
hUu : ⋂ i ∈ (F, U).1, (F, U).2 i ⊆ u
hF : (F, U).1.Finite
hU : ∀ i ∈ (F, U).1, (F, U).2 i ∈ T i ∧ a ∈ (F, U).2 i
⊢ ∃ v ∈ {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}, a ∈ v ∧ v ⊆ u

tactic: refine ⟨_, ⟨U, hF.toFinset, ?_, rfl⟩, ?_, ?_⟩ <;> simp only [Finite.mem_toFinset, mem_iInter]
state_before: case refine_2.intro.mk.intro.intro
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
F : Set ι
U : ι → Set β
hUu : ⋂ i ∈ (F, U).1, (F, U).2 i ⊆ u
hF : (F, U).1.Finite
hU : ∀ i ∈ (F, U).1, (F, U).2 i ∈ T i ∧ a ∈ (F, U).2 i
⊢ ∃ v ∈ {S | ∃ U F, (∀ i ∈ F, U i ∈ T i) ∧ S = ⋂ i ∈ F, U i}, a ∈ v ∧ v ⊆ u
state_after: case refine_2.intro.mk.intro.intro.refine_1
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
F : Set ι
U : ι → Set β
hUu : ⋂ i ∈ (F, U).1, (F, U).2 i ⊆ u
hF : (F, U).1.Finite
hU : ∀ i ∈ (F, U).1, (F, U).2 i ∈ T i ∧ a ∈ (F, U).2 i
⊢ ∀ i ∈ F, U i ∈ T i

case refine_2.intro.mk.intro.intro.refine_2
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
F : Set ι
U : ι → Set β
hUu : ⋂ i ∈ (F, U).1, (F, U).2 i ⊆ u
hF : (F, U).1.Finite
hU : ∀ i ∈ (F, U).1, (F, U).2 i ∈ T i ∧ a ∈ (F, U).2 i
⊢ ∀ i ∈ F, a ∈ U i

case refine_2.intro.mk.intro.intro.refine_3
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
F : Set ι
U : ι → Set β
hUu : ⋂ i ∈ (F, U).1, (F, U).2 i ⊆ u
hF : (F, U).1.Finite
hU : ∀ i ∈ (F, U).1, (F, U).2 i ∈ T i ∧ a ∈ (F, U).2 i
⊢ ⋂ i ∈ F, U i ⊆ u

tactic: exact fun i hi ↦ (hU i hi).1
state_before: case refine_2.intro.mk.intro.intro.refine_1
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
F : Set ι
U : ι → Set β
hUu : ⋂ i ∈ (F, U).1, (F, U).2 i ⊆ u
hF : (F, U).1.Finite
hU : ∀ i ∈ (F, U).1, (F, U).2 i ∈ T i ∧ a ∈ (F, U).2 i
⊢ ∀ i ∈ F, U i ∈ T i
state_after: no goals

tactic: exact fun i hi ↦ (hU i hi).2
state_before: case refine_2.intro.mk.intro.intro.refine_2
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
F : Set ι
U : ι → Set β
hUu : ⋂ i ∈ (F, U).1, (F, U).2 i ⊆ u
hF : (F, U).1.Finite
hU : ∀ i ∈ (F, U).1, (F, U).2 i ∈ T i ∧ a ∈ (F, U).2 i
⊢ ∀ i ∈ F, a ∈ U i
state_after: no goals

tactic: exact hUu
state_before: case refine_2.intro.mk.intro.intro.refine_3
β : Type u_1
ι : Type u_2
t : ι → TopologicalSpace β
T : ι → Set (Set β)
h_basis : ∀ (i : ι), IsTopologicalBasis (T i)
x✝ : TopologicalSpace β := ⨅ i, t i
a : β
u : Set β
ha : a ∈ u
hu : IsOpen u
F : Set ι
U : ι → Set β
hUu : ⋂ i ∈ (F, U).1, (F, U).2 i ⊆ u
hF : (F, U).1.Finite
hU : ∀ i ∈ (F, U).1, (F, U).2 i ∈ T i ∧ a ∈ (F, U).2 i
⊢ ⋂ i ∈ F, U i ⊆ u
state_after: no goals