Theorem: preperfect_iff_perfect_closure
File: Mathlib/Topology/Perfect.lean

Proof steps:
state_before: α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
⊢ Preperfect C ↔ Perfect (closure C)
state_after: case mp
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Preperfect C
⊢ Perfect (closure C)

case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
⊢ Preperfect C
tactic: constructor <;> intro h
state_before: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
⊢ Preperfect C
state_after: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
⊢ AccPt x (𝓟 C)
tactic: intro x xC
state_before: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
⊢ AccPt x (𝓟 C)
state_after: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
H : AccPt x (𝓟 (closure C))
⊢ AccPt x (𝓟 C)
tactic: have H : AccPt x (𝓟 (closure C)) := h.acc _ (subset_closure xC)
state_before: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
H : AccPt x (𝓟 (closure C))
⊢ AccPt x (𝓟 C)
state_after: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
H : ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ closure C
⊢ ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ C
tactic: rw [accPt_iff_frequently] at *
state_before: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
H : ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ closure C
⊢ ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ C
state_after: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
H : ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ closure C
this : ∀ (y : α), y ≠ x ∧ y ∈ closure C → ∃ᶠ (z : α) in 𝓝 y, z ≠ x ∧ z ∈ C
⊢ ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ C
tactic: have : ∀ y, y ≠ x ∧ y ∈ closure C → ∃ᶠ z in 𝓝 y, z ≠ x ∧ z ∈ C := by
    rintro y ⟨hyx, yC⟩
    simp only [← mem_compl_singleton_iff, and_comm, ← frequently_nhdsWithin_iff,
      hyx.nhdsWithin_compl_singleton, ← mem_closure_iff_frequently]
    exact yC
state_before: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
H : ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ closure C
this : ∀ (y : α), y ≠ x ∧ y ∈ closure C → ∃ᶠ (z : α) in 𝓝 y, z ≠ x ∧ z ∈ C
⊢ ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ C
state_after: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
H : ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ closure C
this : ∀ (y : α), y ≠ x ∧ y ∈ closure C → ∃ᶠ (z : α) in 𝓝 y, z ≠ x ∧ z ∈ C
⊢ ∃ᶠ (x' : α) in 𝓝 x, ∃ᶠ (x'' : α) in 𝓝 x', x'' ≠ x ∧ x'' ∈ C
tactic: rw [← frequently_frequently_nhds]
state_before: case mpr
α : Type u_1
inst✝¹ : TopologicalSpace α
C : Set α
inst✝ : T1Space α
h : Perfect (closure C)
x : α
xC : x ∈ C
H : ∃ᶠ (y : α) in 𝓝 x, y ≠ x ∧ y ∈ closure C
this : ∀ (y : α), y ≠ x ∧ y ∈ closure C → ∃ᶠ (z : α) in 𝓝 y, z ≠ x ∧ z ∈ C
⊢ ∃ᶠ (x' : α) in 𝓝 x, ∃ᶠ (x'' : α) in 𝓝 x', x'' ≠ x ∧ x'' ∈ C
state_after: no goals
tactic: exact H.mono this