-- Mathlib/Topology/Category/Compactum.lean
theorem cl_cl {X : Compactum} (A : Set X) : cl (cl A) ⊆ cl A

Proof state:
X : Compactum
A : Set X.A
⊢ Compactum.cl (Compactum.cl A) ⊆ Compactum.cl A

Tactic:
rintro _ ⟨F, hF, rfl⟩

Result:
case intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
⊢ X.str F ∈ Compactum.cl A

Proof state:
case intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
claim3 : ∀ B ∈ C0, (AA ∩ B).Nonempty
this : ∀ (T : fsu), ι T ⊆ C1 → (⋂₀ ι T).Nonempty
G : Ultrafilter (Ultrafilter X.A)
h1 : C1 ⊆ (↑G).sets
⊢ X.str F ∈ Compactum.cl A

Tactic:
use X.join G

Result:
case h
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
claim3 : ∀ B ∈ C0, (AA ∩ B).Nonempty
this : ∀ (T : fsu), ι T ⊆ C1 → (⋂₀ ι T).Nonempty
G : Ultrafilter (Ultrafilter X.A)
h1 : C1 ⊆ (↑G).sets
⊢ X.join G ∈ Compactum.basic A ∧ X.str (X.join G) = X.str F

Proof state:
case intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
claim3 : ∀ B ∈ C0, (AA ∩ B).Nonempty
claim4 : FiniteInter (finiteInterClosure C1)
⊢ ∀ (T : fsu), ι T ⊆ C1 → (⋂₀ ι T).Nonempty

Tactic:
have claim5 : FiniteInter C0 := ⟨⟨_, univ_mem, Set.preimage_univ⟩, claim1⟩

Result:
case intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
claim3 : ∀ B ∈ C0, (AA ∩ B).Nonempty
claim4 : FiniteInter (finiteInterClosure C1)
claim5 : FiniteInter C0
⊢ ∀ (T : fsu), ι T ⊆ C1 → (⋂₀ ι T).Nonempty

Proof state:
case intro.intro.intro.intro.intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
Q : Set X.A
hQ : Q ∈ F
q : X.A
hq1 : q ∈ Q
P : Ultrafilter X.A
hq2 : P ∈ Compactum.basic A
hq3 : X.str P = q
⊢ (AA ∩ X.str ⁻¹' Q).Nonempty

Tactic:
refine ⟨P, hq2, ?_⟩

Result:
case intro.intro.intro.intro.intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
Q : Set X.A
hQ : Q ∈ F
q : X.A
hq1 : q ∈ Q
P : Ultrafilter X.A
hq2 : P ∈ Compactum.basic A
hq3 : X.str P = q
⊢ P ∈ X.str ⁻¹' Q

Proof state:
case intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
claim3 : ∀ B ∈ C0, (AA ∩ B).Nonempty
claim4 : FiniteInter (finiteInterClosure C1)
claim5 : FiniteInter C0
claim6 : ∀ P ∈ C2, P.Nonempty
T : fsu
hT : ι T ⊆ C1
t : Set (Ultrafilter X.A)
ht : t ∈ ↑T
⊢ t ∈ finiteInterClosure C1

Tactic:
exact finiteInterClosure.basic (@hT t ht)

Result:
no goals

Proof state:
case intro.intro.intro.intro.intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
Q : Set X.A
hQ : Q ∈ F
q : X.A
hq1 : q ∈ Q
P : Ultrafilter X.A
hq2 : P ∈ Compactum.basic A
hq3 : X.str P = q
⊢ P ∈ X.str ⁻¹' Q

Tactic:
rw [← hq3] at hq1

Result:
case intro.intro.intro.intro.intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
Q : Set X.A
hQ : Q ∈ F
q : X.A
P : Ultrafilter X.A
hq1 : X.str P ∈ Q
hq2 : P ∈ Compactum.basic A
hq3 : X.str P = q
⊢ P ∈ X.str ⁻¹' Q

Proof state:
case inr.intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
C1 : ssu := insert AA C0
C2 : Set (Set (Ultrafilter X.A)) := finiteInterClosure C1
claim1 : ∀ B ∈ C0, ∀ C ∈ C0, B ∩ C ∈ C0
claim2 : ∀ B ∈ C0, B.Nonempty
claim3 : ∀ B ∈ C0, (AA ∩ B).Nonempty
claim4 : FiniteInter (finiteInterClosure C1)
claim5 : FiniteInter C0
this : ∀ P ∈ C2, P ∈ C0 ∨ ∃ Q ∈ C0, P = AA ∩ Q
Q : Set (Ultrafilter X.A)
hQ : Q ∈ C0
hP : AA ∩ Q ∈ C2
⊢ (AA ∩ Q).Nonempty

Tactic:
exact claim3 _ hQ

Result:
no goals

Proof state:
case intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
⊢ X.str F ∈ Compactum.cl A

Tactic:
let AA := { G : Ultrafilter X | A ∈ G }

Result:
case intro.intro
X : Compactum
A : Set X.A
F : Ultrafilter X.A
hF : F ∈ Compactum.basic (Compactum.cl A)
fsu : Type u_1 := Finset (Set (Ultrafilter X.A))
ssu : Type u_1 := Set (Set (Ultrafilter X.A))
ι : fsu → ssu := fun x => ↑x
C0 : ssu := {Z | ∃ B ∈ F, X.str ⁻¹' B = Z}
AA : Set (Ultrafilter X.A) := {G | A ∈ G}
⊢ X.str F ∈ Compactum.cl A