mathlib-initiative/mathlib-tactics huggingface dataset:
Module: Mathlib.MeasureTheory.Constructions.BorelSpace.Metrizable

Goal state before:
pp: α : Type u_1
β : Type u_2
inst✝⁶ : MeasurableSpace α
inst✝⁵ : TopologicalSpace β
inst✝⁴ : PseudoMetrizableSpace β
inst✝³ : MeasurableSpace β
inst✝² : BorelSpace β
ι : Type u_3
f : ι → α → β
g : α → β
u : Filter ι
inst✝¹ : u.NeBot
inst✝ : u.IsCountablyGenerated
hf : ∀ (i : ι), Measurable (f i)
lim : Tendsto f u (𝓝 g)
⊢ Measurable g

Tactic:
let : PseudoMetricSpace β := pseudoMetrizableSpacePseudoMetric β
  apply measurable_of_isClosed'
  intro s h1s h2s h3s
  have : Measurable fun x => infNndist (g x) s := by
    suffices Tendsto (fun i x => infNndist (f i x) s) u (𝓝 fun x => infNndist (g x) s) from
      NNReal.measurable_of_tendsto' u (fun i => (hf i).infNndist) this
    rw [tendsto_pi_nhds] at lim ⊢
    intro x
    exact ((continuous_infNndist_pt s).tendsto (g x)).comp (lim x)
  have h4s : g ⁻¹' s = (fun x => infNndist (g x) s) ⁻¹' {0} := by
    ext x
    simp [← h1s.mem_iff_infDist_zero h2s, ← NNReal.coe_eq_zero]
  rw [h4s]
  exact this (measurableSet_singleton 0)

Goal state after:
Module: Mathlib.MeasureTheory.Function.SimpleFunc

Goal state before:
pp: α : Type u_5
γ : Type u_6
inst✝¹ : MeasurableSpace α
inst✝ : AddZeroClass γ
motive : (α →ₛ γ) → Prop
const :
  ∀ (c : γ) {s : Set α} (hs : MeasurableSet s), motive (piecewise s hs (SimpleFunc.const α c) (SimpleFunc.const α 0))
add : ∀ ⦃f g : α →ₛ γ⦄, Disjoint (support ⇑f) (support ⇑g) → motive f → motive g → motive (f + g)
x : γ
s : Finset γ
hxs : x ∉ s
ih : ∀ (f : α →ₛ γ), range ⇑f \ {0} = ↑s → motive f
f : α →ₛ γ
h : range ⇑f \ {0} = ↑(insert x s)
mx : MeasurableSet (⇑f ⁻¹' {x})
g : α →ₛ γ := piecewise (⇑f ⁻¹' {x}) mx 0 f
⊢ (⇑0 '' ⇑f ⁻¹' {x} ∪ ⇑f '' (⇑f ⁻¹' {x})ᶜ) \ {0} = ↑s

Tactic:
image_compl_preimage,

Goal state after:
α : Type u_5
γ : Type u_6
inst✝¹ : MeasurableSpace α
inst✝ : AddZeroClass γ
motive : (α →ₛ γ) → Prop
const :
  ∀ (c : γ) {s : Set α} (hs : MeasurableSet s), motive (piecewise s hs (SimpleFunc.const α c) (SimpleFunc.const α 0))
add : ∀ ⦃f g : α →ₛ γ⦄, Disjoint (support ⇑f) (support ⇑g) → motive f → motive g → motive (f + g)
x : γ
s : Finset γ
hxs : x ∉ s
ih : ∀ (f : α →ₛ γ), range ⇑f \ {0} = ↑s → motive f
f : α →ₛ γ
h : range ⇑f \ {0} = ↑(insert x s)
mx : MeasurableSet (⇑f ⁻¹' {x})
g : α →ₛ γ := piecewise (⇑f ⁻¹' {x}) mx 0 f
⊢ (⇑0 '' ⇑f ⁻¹' {x} ∪ range ⇑f \ {x}) \ {0} = ↑s
Module: Mathlib.MeasureTheory.Constructions.BorelSpace.Real

Goal state before:
pp: case pos
α : Type u_1
mα : MeasurableSpace α
ι : Type u_5
f : ι → α → ℝ≥0∞
g : α → ℝ≥0∞
μ : Measure α
u : Filter ι
inst✝¹ : u.NeBot
inst✝ : u.IsCountablyGenerated
hf : ∀ (i : ι), AEMeasurable (f i) μ
hlim : ∀ᵐ (a : α) ∂μ, Tendsto (fun i ↦ f i a) u (𝓝 (g a))
v : ℕ → ι
hv : Tendsto v atTop u
h'f : ∀ (n : ℕ), AEMeasurable (f (v n)) μ
p : α → (ℕ → ℝ≥0∞) → Prop := fun x f' ↦ Tendsto f' atTop (𝓝 (g x))
hp : ∀ᵐ (x : α) ∂μ, p x fun n ↦ f (v n) x
aeSeqLim : α → ℝ≥0∞ := fun x ↦ if x ∈ aeSeqSet h'f p then g x else ⋯.some
x : α
hx : x ∈ aeSeqSet h'f p
⊢ Tendsto (fun i ↦ f (v i) x) atTop (𝓝 (g x))

Tactic:
exact aeSeq.fun_prop_of_mem_aeSeqSet h'f hx

Goal state after:
Module: Mathlib.MeasureTheory.Function.SimpleFunc

Goal state before:
pp: α : Type u_5
γ : Type u_6
inst✝¹ : MeasurableSpace α
inst✝ : Nonempty γ
P : (α →ₛ γ) → Prop
const : ∀ (c : γ), P (SimpleFunc.const α c)
pcw : ∀ ⦃f g : α →ₛ γ⦄ {s : Set α} (hs : MeasurableSet s), P f → P g → P (piecewise s hs f g)
c : γ := Classical.ofNonempty
x : γ
s : Finset γ
hxs : x ∉ s
ih : ∀ (f : α →ₛ γ), range ⇑f \ {c} = ↑s → P f
f : α →ₛ γ
h : range ⇑f \ {c} = ↑(insert x s)
mx : MeasurableSet (⇑f ⁻¹' {x})
g : α →ₛ γ := piecewise (⇑f ⁻¹' {x}) mx (SimpleFunc.const α c) f
⊢ (⇑(SimpleFunc.const α c) '' ⇑f ⁻¹' {x} ∪ ⇑f '' (⇑f ⁻¹' {x})ᶜ) \ {c} = ↑s

Tactic:
image_compl_preimage,

Goal state after:
α : Type u_5
γ : Type u_6
inst✝¹ : MeasurableSpace α
inst✝ : Nonempty γ
P : (α →ₛ γ) → Prop
const : ∀ (c : γ), P (SimpleFunc.const α c)
pcw : ∀ ⦃f g : α →ₛ γ⦄ {s : Set α} (hs : MeasurableSet s), P f → P g → P (piecewise s hs f g)
c : γ := Classical.ofNonempty
x : γ
s : Finset γ
hxs : x ∉ s
ih : ∀ (f : α →ₛ γ), range ⇑f \ {c} = ↑s → P f
f : α →ₛ γ
h : range ⇑f \ {c} = ↑(insert x s)
mx : MeasurableSet (⇑f ⁻¹' {x})
g : α →ₛ γ := piecewise (⇑f ⁻¹' {x}) mx (SimpleFunc.const α c) f
⊢ (⇑(SimpleFunc.const α c) '' ⇑f ⁻¹' {x} ∪ range ⇑f \ {x}) \ {c} = ↑s
Module: Mathlib.MeasureTheory.Integral.Lebesgue.Basic

Goal state before:
pp: α : Type u_1
m : MeasurableSpace α
μ : Measure α
c : ℝ≥0∞
⊢ ∫⁻ (x : α), c ∂μ = (const α c).lintegral μ

Tactic:
← SimpleFunc.lintegral_eq_lintegral,

Goal state after:
α : Type u_1
m : MeasurableSpace α
μ : Measure α
c : ℝ≥0∞
⊢ ∫⁻ (x : α), c ∂μ = ∫⁻ (a : α), (const α c) a ∂μ
Module: Mathlib.MeasureTheory.Function.StronglyMeasurable.Basic

Goal state before:
pp: case inr.refine_1
α : Type u_1
β : Type u_2
f : α → β
inst✝² : TopologicalSpace β
inst✝¹ : Nonempty β
inst✝ : T2Space β
hα : Nonempty α
hf : StronglyMeasurable f
⊢ ∃ c, f = fun x ↦ c

pp: case inr.refine_2
α : Type u_1
β : Type u_2
f : α → β
inst✝² : TopologicalSpace β
inst✝¹ : Nonempty β
inst✝ : T2Space β
hα : Nonempty α
hf_eq : ∃ c, f = fun x ↦ c
⊢ StronglyMeasurable f

Tactic:
· refine ⟨f hα.some, ?_⟩
    let fs := hf.approx
    have h_fs_tendsto : ∀ x, Tendsto (fun n => fs n x) atTop (𝓝 (f x)) := hf.tendsto_approx
    have : ∀ n, ∃ c, ∀ x, fs n x = c := fun n => SimpleFunc.simpleFunc_bot (fs n)
    let cs n := (this n).choose
    have h_cs_eq : ∀ n, ⇑(fs n) = fun _ => cs n := fun n => funext (this n).choose_spec
    conv at h_fs_tendsto => enter [x, 1, n]; rw [h_cs_eq]
    have h_tendsto : Tendsto cs atTop (𝓝 (f hα.some)) := h_fs_tendsto hα.some
    ext1 x
    exact tendsto_nhds_unique (h_fs_tendsto x) h_tendsto

Goal state after:
case inr.refine_2
α : Type u_1
β : Type u_2
f : α → β
inst✝² : TopologicalSpace β
inst✝¹ : Nonempty β
inst✝ : T2Space β
hα : Nonempty α
hf_eq : ∃ c, f = fun x ↦ c
⊢ StronglyMeasurable f
Module: Mathlib.MeasureTheory.Integral.Lebesgue.Sub

Goal state before:
pp: case neg
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
f g : α → ℝ≥0∞
hf : AEMeasurable f μ
hfi : ¬∫⁻ (x : α), f x ∂μ = ∞
⊢ ∫⁻ (x : α), g x ∂μ ≤ ∫⁻ (x : α), g x - f x ∂μ + ∫⁻ (x : α), f x ∂μ

Tactic:
· rw [← lintegral_add_right' _ hf]
    gcongr
    exact le_tsub_add

Goal state after:
Module: Mathlib.MeasureTheory.Function.StronglyMeasurable.Basic

Goal state before:
pp: α : Type u_5
E : Type u_6
x✝ : MeasurableSpace α
inst✝⁵ : AddCancelMonoid E
inst✝⁴ : TopologicalSpace E
inst✝³ : MeasurableSpace E
inst✝² : BorelSpace E
inst✝¹ : ContinuousAdd E
inst✝ : PseudoMetrizableSpace E
g f : α → E
hg : Measurable g
hf : StronglyMeasurable f
⊢ Measurable (f + g)

Tactic:
rcases hf with ⟨φ, hφ⟩
  have : Tendsto (fun n x ↦ φ n x + g x) atTop (𝓝 (f + g)) :=
    tendsto_pi_nhds.2 (fun x ↦ (hφ x).add tendsto_const_nhds)
  apply measurable_of_tendsto_metrizable (fun n ↦ ?_) this
  exact hg.simpleFunc_add _

Goal state after:
Module: Mathlib.MeasureTheory.Integral.Lebesgue.Sub

Goal state before:
pp: α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
f : α → ℝ≥0∞
hf : ∫⁻ (a : α), f a ∂μ ≠ ∞
ε : ℝ≥0∞
hε : ε ≠ 0
hf₀ : ¬∫⁻ (a : α), f a ∂μ = 0
g : α → ℝ≥0∞
hgf : g ≤ f
hg_meas : Measurable g
hgsupp : μ (support g) < ∞
hgε : ∫⁻ (a : α), f a ∂μ - ε < ∫⁻ (a : α), g a ∂μ
⊢ Set.EqOn f (fun a ↦ f a - g a) (support g)ᶜ

Tactic:
intro; simp_all

Goal state after:
Module: Mathlib.MeasureTheory.Integral.Lebesgue.DominatedConvergence

Goal state before:
pp: case refine_3
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
f : ℕ → α → ℝ≥0∞
g : α → ℝ≥0∞
hf_meas : ∀ (n : ℕ), Measurable (f n)
h_bound : ∀ (n : ℕ), f n ≤ᵐ[μ] g
h_fin : ∫⁻ (a : α), g a ∂μ ≠ ∞
⊢ ∫⁻ (a : α), ⨆ i, ⨆ (_ : i ≥ 0), f i a ∂μ ≠ ∞

Tactic:
refine ne_top_of_le_ne_top h_fin (lintegral_mono_ae ?_)
        refine (ae_all_iff.2 h_bound).mono fun n hn => ?_
        exact iSup_le fun i => iSup_le fun _ => hn i

Goal state after:
Module: Mathlib.MeasureTheory.Measure.Decomposition.Exhaustion

Goal state before:
pp: α : Type u_1
mα : MeasurableSpace α
μ ν : Measure α
inst✝ : IsFiniteMeasure ν
n : ℕ
hC_lt : 1 / ↑n < ⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s
h_lt_top : ⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s < ∞
t : Set α
ht :
  (⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s) - 1 / ↑n <
    ⨆ (_ : MeasurableSet t), ⨆ (_ : SigmaFinite (μ.restrict t)), ν t
h_notMem : ¬MeasurableSet t
⊢ False

Tactic:
simp only [h_notMem] at ht

Goal state after:
α : Type u_1
mα : MeasurableSpace α
μ ν : Measure α
inst✝ : IsFiniteMeasure ν
n : ℕ
hC_lt : 1 / ↑n < ⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s
h_lt_top : ⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s < ∞
t : Set α
h_notMem : ¬MeasurableSet t
ht :
  (⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s) - 1 / ↑n <
    ⨆ (_ : False), ⨆ (_ : SigmaFinite (μ.restrict t)), ν t
⊢ False
Module: Mathlib.MeasureTheory.Measure.Decomposition.Exhaustion

Goal state before:
pp: α : Type u_1
mα : MeasurableSpace α
μ ν : Measure α
inst✝ : IsFiniteMeasure ν
n : ℕ
hC_lt : 1 / ↑n < ⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s
h_lt_top : ⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s < ∞
t : Set α
ht :
  (⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s) - 1 / ↑n <
    ⨆ (_ : MeasurableSet t), ⨆ (_ : SigmaFinite (μ.restrict t)), ν t
ht_meas : MeasurableSet t
h_notMem : ¬SigmaFinite (μ.restrict t)
⊢ False

Tactic:
simp only [h_notMem] at ht

Goal state after:
α : Type u_1
mα : MeasurableSpace α
μ ν : Measure α
inst✝ : IsFiniteMeasure ν
n : ℕ
hC_lt : 1 / ↑n < ⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s
h_lt_top : ⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s < ∞
t : Set α
ht_meas : MeasurableSet t
h_notMem : ¬SigmaFinite (μ.restrict t)
ht :
  (⨆ s, ⨆ (_ : MeasurableSet s), ⨆ (_ : SigmaFinite (μ.restrict s)), ν s) - 1 / ↑n <
    ⨆ (_ : MeasurableSet t), ⨆ (_ : False), ν t
⊢ False
Module: Mathlib.MeasureTheory.Function.StronglyMeasurable.Basic

Goal state before:
pp: case add
α : Type u_1
β : Type u_2
inst✝² : MeasurableSpace α
inst✝¹ : AddZeroClass β
inst✝ : TopologicalSpace β
P : (f : α → β) → StronglyMeasurable f → Prop
ind : ∀ (c : β) ⦃s : Set α⦄ (hs : MeasurableSet s), P (s.indicator fun x ↦ c) ⋯
add :
  ∀ ⦃f g : α → β⦄ (hf : StronglyMeasurable f) (hg : StronglyMeasurable g) (hfg : StronglyMeasurable (f + g)),
    Disjoint (support f) (support g) → P f hf → P g hg → P (f + g) hfg
lim :
  ∀ ⦃f : ℕ → α → β⦄ ⦃g : α → β⦄ (hf : ∀ (n : ℕ), StronglyMeasurable (f n)) (hg : StronglyMeasurable g),
    (∀ (n : ℕ), P (f n) ⋯) → (∀ (x : α), Tendsto (fun x_1 ↦ f x_1 x) atTop (𝓝 (g x))) → P g hg
f✝ : α → β
hf✝ : StronglyMeasurable f✝
s : ℕ → α →ₛ β := hf✝.approx
n : ℕ
f g : α →ₛ β
h_supp : Disjoint (support ⇑f) (support ⇑g)
hf : P ⇑f ⋯
hg : P ⇑g ⋯
⊢ P ⇑(f + g) ⋯

Tactic:
exact add f.stronglyMeasurable g.stronglyMeasurable (f + g).stronglyMeasurable h_supp hf hg

Goal state after:
Module: Mathlib.Topology.UnitInterval

Goal state before:
pp: case inr
x : ℝ
h₀ : 0 ≤ x
⊢ ↑(σ (projIcc 0 1 ⋯ x)) = ↑(projIcc 0 1 ⋯ (1 - x))

Tactic:
rcases le_total x 1 with h₁ | h₁

Goal state after:
case inr.inl
x : ℝ
h₀ : 0 ≤ x
h₁ : x ≤ 1
⊢ ↑(σ (projIcc 0 1 ⋯ x)) = ↑(projIcc 0 1 ⋯ (1 - x))

case inr.inr
x : ℝ
h₀ : 0 ≤ x
h₁ : 1 ≤ x
⊢ ↑(σ (projIcc 0 1 ⋯ x)) = ↑(projIcc 0 1 ⋯ (1 - x))
Module: Mathlib.Topology.MetricSpace.Gluing

Goal state before:
pp: X : Type u
Y : Type v
Z : Type w
inst✝² : MetricSpace X
inst✝¹ : MetricSpace Y
inst✝ : Nonempty Z
Φ : Z → X
Ψ : Z → Y
ε : ℝ
H : ∀ (p q : Z), |dist (Φ p) (Φ q) - dist (Ψ p) (Ψ q)| ≤ 2 * ε
x y : X
z : Y
⊢ glueDist Φ Ψ ε (Sum.inl x) (Sum.inr z) ≤
    glueDist Φ Ψ ε (Sum.inl x) (Sum.inl y) + glueDist Φ Ψ ε (Sum.inl y) (Sum.inr z)

Tactic:
simpa only [← glueDist_swap Φ, glueDist_comm, add_comm, Sum.swap_inl, Sum.swap_inr]
      using glueDist_triangle_inl_inr_inr Ψ Φ ε z y x

Goal state after:
Module: Mathlib.Topology.UnitInterval

Goal state before:
pp: α : Type u_1
inst✝² : AddCommGroup α
inst✝¹ : LinearOrder α
inst✝ : IsOrderedAddMonoid α
a b : α
h : a ≤ b
δ : α
hδ : 0 ≤ δ
t : ↑(Icc a b)
n : ℕ
ht : t ∈ Icc (addNSMul h δ n) (addNSMul h δ (n + 1))
⊢ ↑t ≤ ↑(projIcc a b h (a + (n + 1) • δ))

Tactic:
exact ht.2

Goal state after:
Module: Mathlib.Topology.UnitInterval

Goal state before:
pp: α : Type u_1
inst✝² : AddCommGroup α
inst✝¹ : LinearOrder α
inst✝ : IsOrderedAddMonoid α
a b : α
h : a ≤ b
δ : α
hδ : 0 ≤ δ
t : ↑(Icc a b)
n : ℕ
ht : t ∈ Icc (addNSMul h δ n) (addNSMul h δ (n + 1))
⊢ |δ| ≤ δ

Tactic:
exact (abs_eq_self.mpr hδ).le

Goal state after:
Module: Mathlib.Topology.Metrizable.CompletelyMetrizable

Goal state before:
pp: case refine_1
X : Type u_1
Y : Type u_2
inst✝¹ : TopologicalSpace X
inst✝ : DiscreteTopology X
m : MetricSpace X :=
  { dist := fun x y ↦ if x = y then 0 else 1, dist_self := ⋯, dist_comm := ⋯, dist_triangle := ⋯, edist_dist := ⋯,
    uniformity_dist := ⋯, cobounded_sets := ⋯, eq_of_dist_eq_zero := ⋯ }
x : X
⊢ IsOpen[PseudoMetricSpace.toUniformSpace.toTopologicalSpace] {x}

Tactic:
convert! @Metric.isOpen_ball _ _ x 1

Goal state after:
X : Type u_1
Y : Type u_2
inst✝¹ : TopologicalSpace X
inst✝ : DiscreteTopology X
m : MetricSpace X :=
  { dist := fun x y ↦ if x = y then 0 else 1, dist_self := ⋯, dist_comm := ⋯, dist_triangle := ⋯, edist_dist := ⋯,
    uniformity_dist := ⋯, cobounded_sets := ⋯, eq_of_dist_eq_zero := ⋯ }
x : X
⊢ {x} = Metric.ball x 1
Module: Mathlib.Topology.MetricSpace.Gluing

Goal state before:
pp: case mp.inr.inr
X : Type u
Y : Type v
inst✝¹ : MetricSpace X
inst✝ : MetricSpace Y
s : Set ((X ⊕ Y) × (X ⊕ Y))
hsX : s ∈ Filter.map (fun p ↦ (Sum.inl p.1, Sum.inl p.2)) (𝓤 X)
hsY : s ∈ Filter.map (fun p ↦ (Sum.inr p.1, Sum.inr p.2)) (𝓤 Y)
εX : ℝ
εX0 : εX > 0
hX : ∀ ⦃a b : X⦄, dist a b < εX → (a, b) ∈ (fun p ↦ (Sum.inl p.1, Sum.inl p.2)) ⁻¹' s
εY : ℝ
εY0 : εY > 0
hY : ∀ ⦃a b : Y⦄, dist a b < εY → (a, b) ∈ (fun p ↦ (Sum.inr p.1, Sum.inr p.2)) ⁻¹' s
a b : Y
h : Sum.dist (Sum.inr a) (Sum.inr b) < min (min εX εY) 1
⊢ (Sum.inr a, Sum.inr b) ∈ s

Tactic:
exact hY (lt_of_lt_of_le h (le_trans (min_le_left _ _) (min_le_right _ _)))

Goal state after:
Module: Mathlib.Topology.MetricSpace.PiNat

Goal state before:
pp: case a
E✝ : ℕ → Type u_1
inst✝² : (n : ℕ) → TopologicalSpace (E✝ n)
inst✝¹ : ∀ (n : ℕ), DiscreteTopology (E✝ n)
E : ℕ → Type u_2
inst✝ : (n : ℕ) → UniformSpace (E n)
h : ∀ (n : ℕ), uniformity (E n) = 𝓟 SetRel.id
this : ∀ (n : ℕ), DiscreteTopology (E n)
⊢ ⨅ ε, ⨅ (_ : ε > 0), 𝓟 {p | dist p.1 p.2 < ε} ≤ ⨅ i, 𝓟 {a | a.1 i = a.2 i}

Tactic:
simp only [le_iInf_iff, le_principal_iff]
        intro n
        refine mem_iInf_of_mem ((1 / 2) ^ n : ℝ) ?_
        refine mem_iInf_of_mem (by positivity) ?_
        simp only [mem_principal, ofPred_subset_ofPred, Prod.forall]
        intro x y hxy
        exact apply_eq_of_dist_lt hxy le_rfl

Goal state after:
Module: Mathlib.Topology.MetricSpace.PiNat

Goal state before:
pp: case inr
E : ℕ → Type u_1
inst✝¹ : (n : ℕ) → TopologicalSpace (E n)
inst✝ : ∀ (n : ℕ), DiscreteTopology (E n)
s : Set ((n : ℕ) → E n)
hs : IsClosed[Pi.topologicalSpace] s
x : (n : ℕ) → E n
hx : x ∉ s
hne : s.Nonempty
A : 0 < infDist x s
n : ℕ
hn : (1 / 2) ^ n < infDist x s
y : (n : ℕ) → E n
ys : y ∈ s
hy : y ∈ cylinder x n
⊢ infDist x s < infDist x s

Tactic:
calc
    infDist x s ≤ dist x y := infDist_le_dist_of_mem ys
    _ ≤ (1 / 2) ^ n := by
      rw [mem_cylinder_comm] at hy
      exact mem_cylinder_iff_dist_le.1 hy
    _ < infDist x s := hn

Goal state after:
Module: Mathlib.Dynamics.Ergodic.MeasurePreserving

Goal state before:
pp: case succ
α : Type u_1
inst✝ : MeasurableSpace α
μ : Measure α
f : α → α
s : Set α
hf : MeasurePreserving f μ μ
hs : NullMeasurableSet s μ
n : ℕ
ih : μ (s ∆ (f^[n] ⁻¹' s)) ≤ n • μ (s ∆ (f ⁻¹' s))
⊢ μ (s ∆ (f^[n + 1] ⁻¹' s)) ≤ (n + 1) • μ (s ∆ (f ⁻¹' s))

Tactic:
simp only [add_smul, one_smul]
    grw [← ih, measure_symmDiff_le s (f^[n] ⁻¹' s) (f^[n + 1] ⁻¹' s)]
    replace hs : NullMeasurableSet (s ∆ (f ⁻¹' s)) μ :=
      hs.symmDiff <| hs.preimage hf.quasiMeasurePreserving
    rw [iterate_succ', preimage_comp, ← preimage_symmDiff, (hf.iterate n).measure_preimage hs]

Goal state after:
Module: Mathlib.Topology.MetricSpace.Perfect

Goal state before:
pp: case e'_4
α : Type u_1
inst✝¹ : MetricSpace α
C : Set α
hC : Perfect C
hnonempty : C.Nonempty
inst✝ : CompleteSpace α
u : ℕ → ℝ≥0∞
upos' : ∀ (n : ℕ), u n ∈ Ioo 0 1
hu : Tendsto u atTop (nhds 0)
upos : ∀ (n : ℕ), 0 < u n
P : Type (max 0 u_1) := { E // Perfect E ∧ E.Nonempty }
C0 C1 : {C : Set α} → Perfect C → C.Nonempty → {ε : ℝ≥0∞} → 0 < ε → Set α
h0 :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Perfect (C0 hC hnonempty hε) ∧
      (C0 hC hnonempty hε).Nonempty ∧ C0 hC hnonempty hε ⊆ C ∧ ediam (C0 hC hnonempty hε) ≤ ε
h1 :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Perfect (C1 hC hnonempty hε) ∧
      (C1 hC hnonempty hε).Nonempty ∧ C1 hC hnonempty hε ⊆ C ∧ ediam (C1 hC hnonempty hε) ≤ ε
hdisj :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Disjoint (C0 hC hnonempty hε) (C1 hC hnonempty hε)
DP : List Bool → P :=
  fun l ↦
    List.rec ⟨C, ⋯⟩
      (fun a l ih ↦ Bool.casesOn (motive := fun t ↦ a = t → P) a (fun h ↦ ⟨C0 ⋯ ⋯ ⋯, ⋯⟩) (fun h ↦ ⟨C1 ⋯ ⋯ ⋯, ⋯⟩) ⋯) l
D : List Bool → Set α := fun l ↦ ↑(DP l)
hanti : ClosureAntitone D
x : ℕ → Bool
n : ℕ
hm : n.succ ≠ 0
⊢ n = (PiNat.res x n).length

Tactic:
PiNat.res_length

Goal state after:
case e'_4
α : Type u_1
inst✝¹ : MetricSpace α
C : Set α
hC : Perfect C
hnonempty : C.Nonempty
inst✝ : CompleteSpace α
u : ℕ → ℝ≥0∞
upos' : ∀ (n : ℕ), u n ∈ Ioo 0 1
hu : Tendsto u atTop (nhds 0)
upos : ∀ (n : ℕ), 0 < u n
P : Type (max 0 u_1) := { E // Perfect E ∧ E.Nonempty }
C0 C1 : {C : Set α} → Perfect C → C.Nonempty → {ε : ℝ≥0∞} → 0 < ε → Set α
h0 :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Perfect (C0 hC hnonempty hε) ∧
      (C0 hC hnonempty hε).Nonempty ∧ C0 hC hnonempty hε ⊆ C ∧ ediam (C0 hC hnonempty hε) ≤ ε
h1 :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Perfect (C1 hC hnonempty hε) ∧
      (C1 hC hnonempty hε).Nonempty ∧ C1 hC hnonempty hε ⊆ C ∧ ediam (C1 hC hnonempty hε) ≤ ε
hdisj :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Disjoint (C0 hC hnonempty hε) (C1 hC hnonempty hε)
DP : List Bool → P :=
  fun l ↦
    List.rec ⟨C, ⋯⟩
      (fun a l ih ↦ Bool.casesOn (motive := fun t ↦ a = t → P) a (fun h ↦ ⟨C0 ⋯ ⋯ ⋯, ⋯⟩) (fun h ↦ ⟨C1 ⋯ ⋯ ⋯, ⋯⟩) ⋯) l
D : List Bool → Set α := fun l ↦ ↑(DP l)
hanti : ClosureAntitone D
x : ℕ → Bool
n : ℕ
hm : n.succ ≠ 0
⊢ n = n
Module: Mathlib.Topology.MetricSpace.Perfect

Goal state before:
pp: case e'_4
α : Type u_1
inst✝¹ : MetricSpace α
C : Set α
hC : Perfect C
hnonempty : C.Nonempty
inst✝ : CompleteSpace α
u : ℕ → ℝ≥0∞
upos' : ∀ (n : ℕ), u n ∈ Ioo 0 1
hu : Tendsto u atTop (nhds 0)
upos : ∀ (n : ℕ), 0 < u n
P : Type (max 0 u_1) := { E // Perfect E ∧ E.Nonempty }
C0 C1 : {C : Set α} → Perfect C → C.Nonempty → {ε : ℝ≥0∞} → 0 < ε → Set α
h0 :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Perfect (C0 hC hnonempty hε) ∧
      (C0 hC hnonempty hε).Nonempty ∧ C0 hC hnonempty hε ⊆ C ∧ ediam (C0 hC hnonempty hε) ≤ ε
h1 :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Perfect (C1 hC hnonempty hε) ∧
      (C1 hC hnonempty hε).Nonempty ∧ C1 hC hnonempty hε ⊆ C ∧ ediam (C1 hC hnonempty hε) ≤ ε
hdisj :
  ∀ {C : Set α} (hC : Perfect C) (hnonempty : C.Nonempty) {ε : ℝ≥0∞} (hε : 0 < ε),
    Disjoint (C0 hC hnonempty hε) (C1 hC hnonempty hε)
DP : List Bool → P :=
  fun l ↦
    List.rec ⟨C, ⋯⟩
      (fun a l ih ↦ Bool.casesOn (motive := fun t ↦ a = t → P) a (fun h ↦ ⟨C0 ⋯ ⋯ ⋯, ⋯⟩) (fun h ↦ ⟨C1 ⋯ ⋯ ⋯, ⋯⟩) ⋯) l
D : List Bool → Set α := fun l ↦ ↑(DP l)
hanti : ClosureAntitone D
x : ℕ → Bool
n : ℕ
hm : n.succ ≠ 0
⊢ n = (PiNat.res x n).length

Tactic:
rw [PiNat.res_length]

Goal state after:
Module: Mathlib.Topology.MetricSpace.PiNat

Goal state before:
pp: E : ℕ → Type u_1
inst✝¹ : (n : ℕ) → TopologicalSpace (E n)
inst✝ : ∀ (n : ℕ), DiscreteTopology (E n)
s : Set ((n : ℕ) → E n)
hs : IsClosed[Pi.topologicalSpace] s
hne : s.Nonempty
f : ((n : ℕ) → E n) → (n : ℕ) → E n := fun x ↦ if x ∈ s then x else ⋯.some
fs : ∀ x ∈ s, f x = x
x y : (n : ℕ) → E n
hxy : x ≠ y
hfxfy : x ≠ f y
I2 : cylinder x (firstDiff x y) = cylinder y (firstDiff x y)
xs : x ∈ s
ys : y ∉ s
A : (s ∩ cylinder y (longestPrefix y s)).Nonempty
⊢ (if y ∈ s then y else ⋯.some) = A.some

Tactic:
if_neg ys

Goal state after:
Module: Mathlib.Topology.MetricSpace.PiNat

Goal state before:
pp: E : ℕ → Type u_1
inst✝¹ : (n : ℕ) → TopologicalSpace (E n)
inst✝ : ∀ (n : ℕ), DiscreteTopology (E n)
s : Set ((n : ℕ) → E n)
hs : IsClosed[Pi.topologicalSpace] s
hne : s.Nonempty
f : ((n : ℕ) → E n) → (n : ℕ) → E n := fun x ↦ if x ∈ s then x else ⋯.some
fs : ∀ x ∈ s, f x = x
x y : (n : ℕ) → E n
hxy : x ≠ y
hfxfy : f x ≠ f y
I2 : cylinder x (firstDiff x y) = cylinder y (firstDiff x y)
xs : x ∉ s
ys : y ∉ s
Ax : (s ∩ cylinder x (longestPrefix x s)).Nonempty
fx : f x = Ax.some
Ay : (s ∩ cylinder y (longestPrefix y s)).Nonempty
⊢ (if y ∈ s then y else ⋯.some) = Ay.some

Tactic:
if_neg ys

Goal state after:
Module: Mathlib.MeasureTheory.Measure.MutuallySingular

Goal state before:
pp: case refine_2
α : Type u_1
m0 : MeasurableSpace α
μ ν : Measure α
h : Disjoint μ ν
s : ℕ → Set α
hs₂ : ∀ (n : ℕ), μ (s n) = 0
hs₃ : ∀ (n : ℕ), ν (s n)ᶜ ≤ (1 / 2) ^ n
⊢ univ ⊆ (⋃ i, s i) ∪ (⋃ n, s n)ᶜ

Tactic:
union_compl_self

Goal state after:
case refine_2
α : Type u_1
m0 : MeasurableSpace α
μ ν : Measure α
h : Disjoint μ ν
s : ℕ → Set α
hs₂ : ∀ (n : ℕ), μ (s n) = 0
hs₃ : ∀ (n : ℕ), ν (s n)ᶜ ≤ (1 / 2) ^ n
⊢ univ ⊆ univ
Module: Mathlib.MeasureTheory.Integral.Lebesgue.Countable

Goal state before:
pp: α : Type u_1
m : MeasurableSpace α
μ : Measure α
inst✝ : SigmaFinite μ
f : α → ℝ≥0
L : ℝ≥0∞
g₀ : α →ₛ ℝ≥0
hg₀ : ∀ (x : α), ↑(g₀ x) ≤ ↑(f x)
g₀L : L < (SimpleFunc.map ofNNReal g₀).lintegral μ
⊢ ∫⁻ (x : α), ↑(g₀ x) ∂μ = (SimpleFunc.map ofNNReal g₀).lintegral μ

Tactic:
← SimpleFunc.lintegral_eq_lintegral,

Goal state after:
α : Type u_1
m : MeasurableSpace α
μ : Measure α
inst✝ : SigmaFinite μ
f : α → ℝ≥0
L : ℝ≥0∞
g₀ : α →ₛ ℝ≥0
hg₀ : ∀ (x : α), ↑(g₀ x) ≤ ↑(f x)
g₀L : L < (SimpleFunc.map ofNNReal g₀).lintegral μ
⊢ ∫⁻ (x : α), ↑(g₀ x) ∂μ = ∫⁻ (a : α), (SimpleFunc.map ofNNReal g₀) a ∂μ