l3lab/ntp-mathlib huggingface dataset:
theorem iIndepSet.iIndepFun_indicator [Zero β] [One β] {m : MeasurableSpace β} {s : ι → Set Ω}
    (hs : iIndepSet s κ μ) :
    iIndepFun (fun _n => m) (fun n => (s n).indicator fun _ω => 1) κ μ := by
  classical
  rw [iIndepFun_iff_measure_inter_preimage_eq_mul]
  rintro S π _hπ
  simp_rw [Set.indicator_const_preimage_eq_union]
  refine' @hs S (fun i => ite (1 ∈ π i) (s i) ∅ ∪ ite ((0 : β) ∈ π i) (s i)ᶜ ∅) fun i _hi => _
  have hsi : MeasurableSet[generateFrom {s i}] (s i) :=
    measurableSet_generateFrom (Set.mem_singleton _)
  refine'
    MeasurableSet.union (MeasurableSet.ite' (fun _ => hsi) fun _ => _)
      (MeasurableSet.ite' (fun _ => hsi.compl) fun _ => _)
  · exact @MeasurableSet.empty _ (generateFrom {s i})
  · 

Proof state:
case refine'_2
α : Type u_1
Ω : Type u_2
ι : Type u_3
β : Type u_4
β' : Type u_5
γ : Type u_6
γ' : Type u_7
_mα : MeasurableSpace α
_mΩ : MeasurableSpace Ω
κ : ↥(kernel α Ω)
μ : Measure α
f : Ω → β
g : Ω → β'
inst✝¹ : Zero β
inst✝ : One β
m : MeasurableSpace β
s : ι → Set Ω
hs : iIndepSet s κ
S : Finset ι
π : ι → Set β
_hπ : ∀ i ∈ S, MeasurableSet (π i)
i : ι
_hi : i ∈ S
hsi : MeasurableSet (s i)
x✝ : 0 ∉ π i
⊢ MeasurableSet ∅

Next tactic:
exact @MeasurableSet.empty _ (generateFrom {s i})
theorem of_comm {A ι : Type*} [CommRing A] (B : ι → AddSubgroup A)
    (inter : ∀ i j, ∃ k, B k ≤ B i ⊓ B j) (mul : ∀ i, ∃ j, (B j : Set A) * B j ⊆ B i)
    (leftMul : ∀ x : A, ∀ i, ∃ j, (B j : Set A) ⊆ (fun y : A => x * y) ⁻¹' B i) :
    RingSubgroupsBasis B :=
  { inter
    mul
    leftMul
    rightMul := by
      

Proof state:
A✝ : Type u_1
ι✝ : Type u_2
inst✝¹ : Ring A✝
A : Type u_3
ι : Type u_4
inst✝ : CommRing A
B : ι → AddSubgroup A
inter : ∀ (i j : ι), ∃ k, B k ≤ B i ⊓ B j
mul : ∀ (i : ι), ∃ j, ↑(B j) * ↑(B j) ⊆ ↑(B i)
leftMul : ∀ (x : A) (i : ι), ∃ j, ↑(B j) ⊆ (fun y => x * y) ⁻¹' ↑(B i)
⊢ ∀ (x : A) (i : ι), ∃ j, ↑(B j) ⊆ (fun x_1 => x_1 * x) ⁻¹' ↑(B i)

Next tactic:
intro x i
theorem of_comm {A ι : Type*} [CommRing A] (B : ι → AddSubgroup A)
    (inter : ∀ i j, ∃ k, B k ≤ B i ⊓ B j) (mul : ∀ i, ∃ j, (B j : Set A) * B j ⊆ B i)
    (leftMul : ∀ x : A, ∀ i, ∃ j, (B j : Set A) ⊆ (fun y : A => x * y) ⁻¹' B i) :
    RingSubgroupsBasis B :=
  { inter
    mul
    leftMul
    rightMul := by
      intro x i
      

Proof state:
A✝ : Type u_1
ι✝ : Type u_2
inst✝¹ : Ring A✝
A : Type u_3
ι : Type u_4
inst✝ : CommRing A
B : ι → AddSubgroup A
inter : ∀ (i j : ι), ∃ k, B k ≤ B i ⊓ B j
mul : ∀ (i : ι), ∃ j, ↑(B j) * ↑(B j) ⊆ ↑(B i)
leftMul : ∀ (x : A) (i : ι), ∃ j, ↑(B j) ⊆ (fun y => x * y) ⁻¹' ↑(B i)
x : A
i : ι
⊢ ∃ j, ↑(B j) ⊆ (fun x_1 => x_1 * x) ⁻¹' ↑(B i)

Next tactic:
cases' leftMul x i with j hj
theorem of_comm {A ι : Type*} [CommRing A] (B : ι → AddSubgroup A)
    (inter : ∀ i j, ∃ k, B k ≤ B i ⊓ B j) (mul : ∀ i, ∃ j, (B j : Set A) * B j ⊆ B i)
    (leftMul : ∀ x : A, ∀ i, ∃ j, (B j : Set A) ⊆ (fun y : A => x * y) ⁻¹' B i) :
    RingSubgroupsBasis B :=
  { inter
    mul
    leftMul
    rightMul := by
      intro x i
      cases' leftMul x i with j hj
      

Proof state:
case intro
A✝ : Type u_1
ι✝ : Type u_2
inst✝¹ : Ring A✝
A : Type u_3
ι : Type u_4
inst✝ : CommRing A
B : ι → AddSubgroup A
inter : ∀ (i j : ι), ∃ k, B k ≤ B i ⊓ B j
mul : ∀ (i : ι), ∃ j, ↑(B j) * ↑(B j) ⊆ ↑(B i)
leftMul : ∀ (x : A) (i : ι), ∃ j, ↑(B j) ⊆ (fun y => x * y) ⁻¹' ↑(B i)
x : A
i j : ι
hj : ↑(B j) ⊆ (fun y => x * y) ⁻¹' ↑(B i)
⊢ ∃ j, ↑(B j) ⊆ (fun x_1 => x_1 * x) ⁻¹' ↑(B i)

Next tactic:
use j
theorem of_comm {A ι : Type*} [CommRing A] (B : ι → AddSubgroup A)
    (inter : ∀ i j, ∃ k, B k ≤ B i ⊓ B j) (mul : ∀ i, ∃ j, (B j : Set A) * B j ⊆ B i)
    (leftMul : ∀ x : A, ∀ i, ∃ j, (B j : Set A) ⊆ (fun y : A => x * y) ⁻¹' B i) :
    RingSubgroupsBasis B :=
  { inter
    mul
    leftMul
    rightMul := by
      intro x i
      cases' leftMul x i with j hj
      use j
      

Proof state:
case h
A✝ : Type u_1
ι✝ : Type u_2
inst✝¹ : Ring A✝
A : Type u_3
ι : Type u_4
inst✝ : CommRing A
B : ι → AddSubgroup A
inter : ∀ (i j : ι), ∃ k, B k ≤ B i ⊓ B j
mul : ∀ (i : ι), ∃ j, ↑(B j) * ↑(B j) ⊆ ↑(B i)
leftMul : ∀ (x : A) (i : ι), ∃ j, ↑(B j) ⊆ (fun y => x * y) ⁻¹' ↑(B i)
x : A
i j : ι
hj : ↑(B j) ⊆ (fun y => x * y) ⁻¹' ↑(B i)
⊢ ↑(B j) ⊆ (fun x_1 => x_1 * x) ⁻¹' ↑(B i)

Next tactic:
simpa [mul_comm] using hj
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    

Proof state:
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
⊢ Set.Nonempty {U | ∃ i, U = ↑(B i)}

Next tactic:
inhabit ι
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    

Proof state:
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
inhabited_h : Inhabited ι
⊢ Set.Nonempty {U | ∃ i, U = ↑(B i)}

Next tactic:
exact ⟨B default, default, rfl⟩
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    

Proof state:
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
⊢ ∀ {x y : Set A}, x ∈ {U | ∃ i, U = ↑(B i)} → y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y

Next tactic:
rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    

Proof state:
case intro.intro
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i j : ι
⊢ ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ ↑(B i) ∩ ↑(B j)

Next tactic:
cases' hB.inter i j with k hk
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    

Proof state:
case intro.intro.intro
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i j k : ι
hk : B k ≤ B i ⊓ B j
⊢ ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ ↑(B i) ∩ ↑(B j)

Next tactic:
use B k
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    

Proof state:
case h
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i j k : ι
hk : B k ≤ B i ⊓ B j
⊢ ↑(B k) ∈ {U | ∃ i, U = ↑(B i)} ∧ ↑(B k) ⊆ ↑(B i) ∩ ↑(B j)

Next tactic:
constructor
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · 

Proof state:
case h.left
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i j k : ι
hk : B k ≤ B i ⊓ B j
⊢ ↑(B k) ∈ {U | ∃ i, U = ↑(B i)}

Next tactic:
use k
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · 

Proof state:
case h.right
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i j k : ι
hk : B k ≤ B i ⊓ B j
⊢ ↑(B k) ⊆ ↑(B i) ∩ ↑(B j)

Next tactic:
exact hk
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    

Proof state:
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
⊢ ∀ {U : Set A},
    U ∈
        { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
            inter_sets :=
              (_ :
                ∀ {x y : Set A},
                  x ∈ {U | ∃ i, U = ↑(B i)} →
                    y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets →
      0 ∈ U

Next tactic:
rintro _ ⟨i, rfl⟩
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    

Proof state:
case intro
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ 0 ∈ ↑(B i)

Next tactic:
exact (B i).zero_mem
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    

Proof state:
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
⊢ ∀ {U : Set A},
    U ∈
        { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
            inter_sets :=
              (_ :
                ∀ {x y : Set A},
                  x ∈ {U | ∃ i, U = ↑(B i)} →
                    y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets →
      ∃
        V ∈
          { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
              inter_sets :=
                (_ :
                  ∀ {x y : Set A},
                    x ∈ {U | ∃ i, U = ↑(B i)} →
                      y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets,
        V + V ⊆ U

Next tactic:
rintro _ ⟨i, rfl⟩
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    

Proof state:
case intro
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ ∃
    V ∈
      { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
          inter_sets :=
            (_ :
              ∀ {x y : Set A},
                x ∈ {U | ∃ i, U = ↑(B i)} → y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets,
    V + V ⊆ ↑(B i)

Next tactic:
use B i
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    

Proof state:
case h
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ ↑(B i) ∈
      { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
          inter_sets :=
            (_ :
              ∀ {x y : Set A},
                x ∈ {U | ∃ i, U = ↑(B i)} → y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets ∧
    ↑(B i) + ↑(B i) ⊆ ↑(B i)

Next tactic:
constructor
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · 

Proof state:
case h.left
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ ↑(B i) ∈
    { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
        inter_sets :=
          (_ :
            ∀ {x y : Set A},
              x ∈ {U | ∃ i, U = ↑(B i)} → y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets

Next tactic:
use i
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · 

Proof state:
case h.right
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ ↑(B i) + ↑(B i) ⊆ ↑(B i)

Next tactic:
rintro x ⟨y, z, y_in, z_in, rfl⟩
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · rintro x ⟨y, z, y_in, z_in, rfl⟩
      

Proof state:
case h.right.intro.intro.intro.intro
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
y z : A
y_in : y ∈ ↑(B i)
z_in : z ∈ ↑(B i)
⊢ (fun x x_1 => x + x_1) y z ∈ ↑(B i)

Next tactic:
exact (B i).add_mem y_in z_in
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · rintro x ⟨y, z, y_in, z_in, rfl⟩
      exact (B i).add_mem y_in z_in
  neg' := by
    

Proof state:
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
⊢ ∀ {U : Set A},
    U ∈
        { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
            inter_sets :=
              (_ :
                ∀ {x y : Set A},
                  x ∈ {U | ∃ i, U = ↑(B i)} →
                    y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets →
      ∃
        V ∈
          { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
              inter_sets :=
                (_ :
                  ∀ {x y : Set A},
                    x ∈ {U | ∃ i, U = ↑(B i)} →
                      y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets,
        V ⊆ (fun x => -x) ⁻¹' U

Next tactic:
rintro _ ⟨i, rfl⟩
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · rintro x ⟨y, z, y_in, z_in, rfl⟩
      exact (B i).add_mem y_in z_in
  neg' := by
    rintro _ ⟨i, rfl⟩
    

Proof state:
case intro
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ ∃
    V ∈
      { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
          inter_sets :=
            (_ :
              ∀ {x y : Set A},
                x ∈ {U | ∃ i, U = ↑(B i)} → y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets,
    V ⊆ (fun x => -x) ⁻¹' ↑(B i)

Next tactic:
use B i
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · rintro x ⟨y, z, y_in, z_in, rfl⟩
      exact (B i).add_mem y_in z_in
  neg' := by
    rintro _ ⟨i, rfl⟩
    use B i
    

Proof state:
case h
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ ↑(B i) ∈
      { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
          inter_sets :=
            (_ :
              ∀ {x y : Set A},
                x ∈ {U | ∃ i, U = ↑(B i)} → y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets ∧
    ↑(B i) ⊆ (fun x => -x) ⁻¹' ↑(B i)

Next tactic:
constructor
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · rintro x ⟨y, z, y_in, z_in, rfl⟩
      exact (B i).add_mem y_in z_in
  neg' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · 

Proof state:
case h.left
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ ↑(B i) ∈
    { sets := {U | ∃ i, U = ↑(B i)}, nonempty := (_ : ∃ x, x ∈ {U | ∃ i, U = ↑(B i)}),
        inter_sets :=
          (_ :
            ∀ {x y : Set A},
              x ∈ {U | ∃ i, U = ↑(B i)} → y ∈ {U | ∃ i, U = ↑(B i)} → ∃ z ∈ {U | ∃ i, U = ↑(B i)}, z ⊆ x ∩ y) }.sets

Next tactic:
use i
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · rintro x ⟨y, z, y_in, z_in, rfl⟩
      exact (B i).add_mem y_in z_in
  neg' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · 

Proof state:
case h.right
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
⊢ ↑(B i) ⊆ (fun x => -x) ⁻¹' ↑(B i)

Next tactic:
intro x x_in
/-- Every subgroups basis on a ring leads to a ring filter basis. -/
def toRingFilterBasis [Nonempty ι] {B : ι → AddSubgroup A} (hB : RingSubgroupsBasis B) :
    RingFilterBasis A where
  sets := { U | ∃ i, U = B i }
  nonempty := by
    inhabit ι
    exact ⟨B default, default, rfl⟩
  inter_sets := by
    rintro _ _ ⟨i, rfl⟩ ⟨j, rfl⟩
    cases' hB.inter i j with k hk
    use B k
    constructor
    · use k
    · exact hk
  zero' := by
    rintro _ ⟨i, rfl⟩
    exact (B i).zero_mem
  add' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · rintro x ⟨y, z, y_in, z_in, rfl⟩
      exact (B i).add_mem y_in z_in
  neg' := by
    rintro _ ⟨i, rfl⟩
    use B i
    constructor
    · use i
    · intro x x_in
      

Proof state:
case h.right
A : Type u_1
ι : Type u_2
inst✝¹ : Ring A
inst✝ : Nonempty ι
B : ι → AddSubgroup A
hB : RingSubgroupsBasis B
i : ι
x : A
x_in : x ∈ ↑(B i)
⊢ x ∈ (fun x => -x) ⁻¹' ↑(B i)

Next tactic:
exact (B i).neg_mem x_in