l3lab/ntp-mathlib huggingface dataset:
/-- A series of non-negative real numbers converges to `r` in the sense of `HasSum` if and only if
the sequence of partial sum converges to `r`. -/
theorem hasSum_iff_tendsto_nat_of_nonneg {f : ℕ → ℝ} (hf : ∀ i, 0 ≤ f i) (r : ℝ) :
    HasSum f r ↔ Tendsto (fun n : ℕ => ∑ i in Finset.range n, f i) atTop (𝓝 r) := by
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
f : ℕ → ℝ
hf : ∀ (i : ℕ), 0 ≤ f i
r : ℝ
⊢ HasSum f r ↔ Tendsto (fun n => ∑ i in Finset.range n, f i) atTop (𝓝 r)

Next tactic:
lift f to ℕ → ℝ≥0 using hf
/-- A series of non-negative real numbers converges to `r` in the sense of `HasSum` if and only if
the sequence of partial sum converges to `r`. -/
theorem hasSum_iff_tendsto_nat_of_nonneg {f : ℕ → ℝ} (hf : ∀ i, 0 ≤ f i) (r : ℝ) :
    HasSum f r ↔ Tendsto (fun n : ℕ => ∑ i in Finset.range n, f i) atTop (𝓝 r) := by
  lift f to ℕ → ℝ≥0 using hf
  

Proof state:
case intro
α : Type u_1
β : Type u_2
γ : Type u_3
r : ℝ
f : ℕ → ℝ≥0
⊢ HasSum (fun i => ↑(f i)) r ↔ Tendsto (fun n => ∑ i in Finset.range n, (fun i => ↑(f i)) i) atTop (𝓝 r)

Next tactic:
simp only [HasSum, ← NNReal.coe_sum, NNReal.tendsto_coe']
/-- A series of non-negative real numbers converges to `r` in the sense of `HasSum` if and only if
the sequence of partial sum converges to `r`. -/
theorem hasSum_iff_tendsto_nat_of_nonneg {f : ℕ → ℝ} (hf : ∀ i, 0 ≤ f i) (r : ℝ) :
    HasSum f r ↔ Tendsto (fun n : ℕ => ∑ i in Finset.range n, f i) atTop (𝓝 r) := by
  lift f to ℕ → ℝ≥0 using hf
  simp only [HasSum, ← NNReal.coe_sum, NNReal.tendsto_coe']
  

Proof state:
case intro
α : Type u_1
β : Type u_2
γ : Type u_3
r : ℝ
f : ℕ → ℝ≥0
⊢ (∃ (hx : 0 ≤ r), Tendsto (fun a => ∑ a in a, f a) atTop (𝓝 { val := r, property := hx })) ↔
    ∃ (hx : 0 ≤ r), Tendsto (fun a => ∑ a in Finset.range a, f a) atTop (𝓝 { val := r, property := hx })

Next tactic:
exact exists_congr fun hr => NNReal.hasSum_iff_tendsto_nat
theorem ENNReal.ofReal_tsum_of_nonneg {f : α → ℝ} (hf_nonneg : ∀ n, 0 ≤ f n) (hf : Summable f) :
    ENNReal.ofReal (∑' n, f n) = ∑' n, ENNReal.ofReal (f n) := by
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
f : α → ℝ
hf_nonneg : ∀ (n : α), 0 ≤ f n
hf : Summable f
⊢ ENNReal.ofReal (∑' (n : α), f n) = ∑' (n : α), ENNReal.ofReal (f n)

Next tactic:
simp_rw [ENNReal.ofReal, ENNReal.tsum_coe_eq (NNReal.hasSum_real_toNNReal_of_nonneg hf_nonneg hf)]
theorem not_summable_iff_tendsto_nat_atTop_of_nonneg {f : ℕ → ℝ} (hf : ∀ n, 0 ≤ f n) :
    ¬Summable f ↔ Tendsto (fun n : ℕ => ∑ i in Finset.range n, f i) atTop atTop := by
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
f : ℕ → ℝ
hf : ∀ (n : ℕ), 0 ≤ f n
⊢ ¬Summable f ↔ Tendsto (fun n => ∑ i in Finset.range n, f i) atTop atTop

Next tactic:
lift f to ℕ → ℝ≥0 using hf
theorem not_summable_iff_tendsto_nat_atTop_of_nonneg {f : ℕ → ℝ} (hf : ∀ n, 0 ≤ f n) :
    ¬Summable f ↔ Tendsto (fun n : ℕ => ∑ i in Finset.range n, f i) atTop atTop := by
  lift f to ℕ → ℝ≥0 using hf
  

Proof state:
case intro
α : Type u_1
β : Type u_2
γ : Type u_3
f : ℕ → ℝ≥0
⊢ (¬Summable fun i => ↑(f i)) ↔ Tendsto (fun n => ∑ i in Finset.range n, (fun i => ↑(f i)) i) atTop atTop

Next tactic:
exact mod_cast NNReal.not_summable_iff_tendsto_nat_atTop
theorem summable_iff_not_tendsto_nat_atTop_of_nonneg {f : ℕ → ℝ} (hf : ∀ n, 0 ≤ f n) :
    Summable f ↔ ¬Tendsto (fun n : ℕ => ∑ i in Finset.range n, f i) atTop atTop := by
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
f : ℕ → ℝ
hf : ∀ (n : ℕ), 0 ≤ f n
⊢ Summable f ↔ ¬Tendsto (fun n => ∑ i in Finset.range n, f i) atTop atTop

Next tactic:
rw [← not_iff_not, Classical.not_not, not_summable_iff_tendsto_nat_atTop_of_nonneg hf]
theorem summable_sigma_of_nonneg {β : α → Type*} {f : (Σ x, β x) → ℝ} (hf : ∀ x, 0 ≤ f x) :
    Summable f ↔ (∀ x, Summable fun y => f ⟨x, y⟩) ∧ Summable fun x => ∑' y, f ⟨x, y⟩ := by
  

Proof state:
α : Type u_1
β✝ : Type u_2
γ : Type u_3
β : α → Type u_4
f : (x : α) × β x → ℝ
hf : ∀ (x : (x : α) × β x), 0 ≤ f x
⊢ Summable f ↔
    (∀ (x : α), Summable fun y => f { fst := x, snd := y }) ∧ Summable fun x => ∑' (y : β x), f { fst := x, snd := y }

Next tactic:
lift f to (Σx, β x) → ℝ≥0 using hf
theorem summable_sigma_of_nonneg {β : α → Type*} {f : (Σ x, β x) → ℝ} (hf : ∀ x, 0 ≤ f x) :
    Summable f ↔ (∀ x, Summable fun y => f ⟨x, y⟩) ∧ Summable fun x => ∑' y, f ⟨x, y⟩ := by
  lift f to (Σx, β x) → ℝ≥0 using hf
  

Proof state:
case intro
α : Type u_1
β✝ : Type u_2
γ : Type u_3
β : α → Type u_4
f : (x : α) × β x → ℝ≥0
⊢ (Summable fun i => ↑(f i)) ↔
    (∀ (x : α), Summable fun y => (fun i => ↑(f i)) { fst := x, snd := y }) ∧
      Summable fun x => ∑' (y : β x), (fun i => ↑(f i)) { fst := x, snd := y }

Next tactic:
exact mod_cast NNReal.summable_sigma
theorem summable_of_sum_range_le {f : ℕ → ℝ} {c : ℝ} (hf : ∀ n, 0 ≤ f n)
    (h : ∀ n, ∑ i in Finset.range n, f i ≤ c) : Summable f := by
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
f : ℕ → ℝ
c : ℝ
hf : ∀ (n : ℕ), 0 ≤ f n
h : ∀ (n : ℕ), ∑ i in Finset.range n, f i ≤ c
⊢ Summable f

Next tactic:
refine (summable_iff_not_tendsto_nat_atTop_of_nonneg hf).2 fun H => ?_
theorem summable_of_sum_range_le {f : ℕ → ℝ} {c : ℝ} (hf : ∀ n, 0 ≤ f n)
    (h : ∀ n, ∑ i in Finset.range n, f i ≤ c) : Summable f := by
  refine (summable_iff_not_tendsto_nat_atTop_of_nonneg hf).2 fun H => ?_
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
f : ℕ → ℝ
c : ℝ
hf : ∀ (n : ℕ), 0 ≤ f n
h : ∀ (n : ℕ), ∑ i in Finset.range n, f i ≤ c
H : Tendsto (fun n => ∑ i in Finset.range n, f i) atTop atTop
⊢ False

Next tactic:
rcases exists_lt_of_tendsto_atTop H 0 c with ⟨n, -, hn⟩
theorem summable_of_sum_range_le {f : ℕ → ℝ} {c : ℝ} (hf : ∀ n, 0 ≤ f n)
    (h : ∀ n, ∑ i in Finset.range n, f i ≤ c) : Summable f := by
  refine (summable_iff_not_tendsto_nat_atTop_of_nonneg hf).2 fun H => ?_
  rcases exists_lt_of_tendsto_atTop H 0 c with ⟨n, -, hn⟩
  

Proof state:
case intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
f : ℕ → ℝ
c : ℝ
hf : ∀ (n : ℕ), 0 ≤ f n
h : ∀ (n : ℕ), ∑ i in Finset.range n, f i ≤ c
H : Tendsto (fun n => ∑ i in Finset.range n, f i) atTop atTop
n : ℕ
hn : c < ∑ i in Finset.range n, f i
⊢ False

Next tactic:
exact lt_irrefl _ (hn.trans_le (h n))
/-- In an emetric ball, the distance between points is everywhere finite -/
theorem edist_ne_top_of_mem_ball {a : β} {r : ℝ≥0∞} (x y : ball a r) : edist x.1 y.1 ≠ ⊤ :=
  ne_of_lt <|
    calc
      edist x y ≤ edist a x + edist a y := edist_triangle_left x.1 y.1 a
      _ < r + r := by 

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝ : EMetricSpace β
a : β
r : ℝ≥0∞
x y : ↑(EMetric.ball a r)
⊢ edist a ↑x + edist a ↑y < r + r

Next tactic:
rw [edist_comm a x, edist_comm a y]
/-- In an emetric ball, the distance between points is everywhere finite -/
theorem edist_ne_top_of_mem_ball {a : β} {r : ℝ≥0∞} (x y : ball a r) : edist x.1 y.1 ≠ ⊤ :=
  ne_of_lt <|
    calc
      edist x y ≤ edist a x + edist a y := edist_triangle_left x.1 y.1 a
      _ < r + r := by rw [edist_comm a x, edist_comm a y]; 

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝ : EMetricSpace β
a : β
r : ℝ≥0∞
x y : ↑(EMetric.ball a r)
⊢ edist (↑x) a + edist (↑y) a < r + r

Next tactic:
exact add_lt_add x.2 y.2
theorem tendsto_iff_edist_tendsto_0 {l : Filter β} {f : β → α} {y : α} :
    Tendsto f l (𝓝 y) ↔ Tendsto (fun x => edist (f x) y) l (𝓝 0) := by
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝ : PseudoEMetricSpace α
l : Filter β
f : β → α
y : α
⊢ Tendsto f l (𝓝 y) ↔ Tendsto (fun x => edist (f x) y) l (𝓝 0)

Next tactic:
simp only [EMetric.nhds_basis_eball.tendsto_right_iff, EMetric.mem_ball,
    @tendsto_order ℝ≥0∞ β _ _, forall_prop_of_false ENNReal.not_lt_zero, forall_const, true_and_iff]
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  

Proof state:
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
⊢ (∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε) ↔
    ∃ b, (∀ (n m N : β), N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧ Tendsto b atTop (𝓝 0)

Next tactic:
constructor
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · 

Proof state:
case mp
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
⊢ (∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε) →
    ∃ b, (∀ (n m N : β), N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧ Tendsto b atTop (𝓝 0)

Next tactic:
intro hs
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    

Proof state:
case mp
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
hs : ∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
⊢ ∃ b, (∀ (n m N : β), N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧ Tendsto b atTop (𝓝 0)

Next tactic:
refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · 

Proof state:
case mp.refine_1
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
hs : ∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
n m N : β
hn : N ≤ n
hm : N ≤ m
⊢ edist (s n) (s m) ≤ (fun N => diam (s '' Ici N)) N

Next tactic:
exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · 

Proof state:
case mp.refine_2
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
hs : ∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
⊢ Tendsto (fun N => diam (s '' Ici N)) atTop (𝓝 0)

Next tactic:
refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
      

Proof state:
case mp.refine_2
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
hs : ∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
ε : ℝ≥0∞
ε0 : ε > 0
⊢ ∀ᶠ (x : β) in atTop, diam (s '' Ici x) ≤ ε

Next tactic:
rcases hs ε ε0 with ⟨N, hN⟩
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
      rcases hs ε ε0 with ⟨N, hN⟩
      

Proof state:
case mp.refine_2.intro
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
hs : ∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
ε : ℝ≥0∞
ε0 : ε > 0
N : β
hN : ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
⊢ ∀ᶠ (x : β) in atTop, diam (s '' Ici x) ≤ ε

Next tactic:
refine (eventually_ge_atTop N).mono fun n hn => EMetric.diam_le ?_
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
      rcases hs ε ε0 with ⟨N, hN⟩
      refine (eventually_ge_atTop N).mono fun n hn => EMetric.diam_le ?_
      

Proof state:
case mp.refine_2.intro
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
hs : ∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
ε : ℝ≥0∞
ε0 : ε > 0
N : β
hN : ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
n : β
hn : N ≤ n
⊢ ∀ x ∈ s '' Ici n, ∀ y ∈ s '' Ici n, edist x y ≤ ε

Next tactic:
rintro _ ⟨k, hk, rfl⟩ _ ⟨l, hl, rfl⟩
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
      rcases hs ε ε0 with ⟨N, hN⟩
      refine (eventually_ge_atTop N).mono fun n hn => EMetric.diam_le ?_
      rintro _ ⟨k, hk, rfl⟩ _ ⟨l, hl, rfl⟩
      

Proof state:
case mp.refine_2.intro.intro.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
hs : ∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
ε : ℝ≥0∞
ε0 : ε > 0
N : β
hN : ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε
n : β
hn : N ≤ n
k : β
hk : k ∈ Ici n
l : β
hl : l ∈ Ici n
⊢ edist (s k) (s l) ≤ ε

Next tactic:
exact (hN _ (hn.trans hk) _ (hn.trans hl)).le
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
      rcases hs ε ε0 with ⟨N, hN⟩
      refine (eventually_ge_atTop N).mono fun n hn => EMetric.diam_le ?_
      rintro _ ⟨k, hk, rfl⟩ _ ⟨l, hl, rfl⟩
      exact (hN _ (hn.trans hk) _ (hn.trans hl)).le
  · 

Proof state:
case mpr
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
⊢ (∃ b, (∀ (n m N : β), N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧ Tendsto b atTop (𝓝 0)) →
    ∀ ε > 0, ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε

Next tactic:
rintro ⟨b, ⟨b_bound, b_lim⟩⟩ ε εpos
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
      rcases hs ε ε0 with ⟨N, hN⟩
      refine (eventually_ge_atTop N).mono fun n hn => EMetric.diam_le ?_
      rintro _ ⟨k, hk, rfl⟩ _ ⟨l, hl, rfl⟩
      exact (hN _ (hn.trans hk) _ (hn.trans hl)).le
  · rintro ⟨b, ⟨b_bound, b_lim⟩⟩ ε εpos
    

Proof state:
case mpr.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
b : β → ℝ≥0∞
b_bound : ∀ (n m N : β), N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N
b_lim : Tendsto b atTop (𝓝 0)
ε : ℝ≥0∞
εpos : ε > 0
⊢ ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε

Next tactic:
have : ∀ᶠ n in atTop, b n < ε := b_lim.eventually (gt_mem_nhds εpos)
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
      rcases hs ε ε0 with ⟨N, hN⟩
      refine (eventually_ge_atTop N).mono fun n hn => EMetric.diam_le ?_
      rintro _ ⟨k, hk, rfl⟩ _ ⟨l, hl, rfl⟩
      exact (hN _ (hn.trans hk) _ (hn.trans hl)).le
  · rintro ⟨b, ⟨b_bound, b_lim⟩⟩ ε εpos
    have : ∀ᶠ n in atTop, b n < ε := b_lim.eventually (gt_mem_nhds εpos)
    

Proof state:
case mpr.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
b : β → ℝ≥0∞
b_bound : ∀ (n m N : β), N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N
b_lim : Tendsto b atTop (𝓝 0)
ε : ℝ≥0∞
εpos : ε > 0
this : ∀ᶠ (n : β) in atTop, b n < ε
⊢ ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε

Next tactic:
rcases this.exists with ⟨N, hN⟩
/-- Yet another metric characterization of Cauchy sequences on integers. This one is often the
most efficient. -/
theorem EMetric.cauchySeq_iff_le_tendsto_0 [Nonempty β] [SemilatticeSup β] {s : β → α} :
    CauchySeq s ↔ ∃ b : β → ℝ≥0∞, (∀ n m N : β, N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N) ∧
      Tendsto b atTop (𝓝 0) := EMetric.cauchySeq_iff.trans <| by
  constructor
  · intro hs
    /- `s` is Cauchy sequence. Let `b n` be the diameter of the set `s '' Set.Ici n`. -/
    refine ⟨fun N => EMetric.diam (s '' Ici N), fun n m N hn hm => ?_, ?_⟩
    -- Prove that it bounds the distances of points in the Cauchy sequence
    · exact EMetric.edist_le_diam_of_mem (mem_image_of_mem _ hn) (mem_image_of_mem _ hm)
    -- Prove that it tends to `0`, by using the Cauchy property of `s`
    · refine ENNReal.tendsto_nhds_zero.2 fun ε ε0 => ?_
      rcases hs ε ε0 with ⟨N, hN⟩
      refine (eventually_ge_atTop N).mono fun n hn => EMetric.diam_le ?_
      rintro _ ⟨k, hk, rfl⟩ _ ⟨l, hl, rfl⟩
      exact (hN _ (hn.trans hk) _ (hn.trans hl)).le
  · rintro ⟨b, ⟨b_bound, b_lim⟩⟩ ε εpos
    have : ∀ᶠ n in atTop, b n < ε := b_lim.eventually (gt_mem_nhds εpos)
    rcases this.exists with ⟨N, hN⟩
    

Proof state:
case mpr.intro.intro.intro
α : Type u_1
β : Type u_2
γ : Type u_3
inst✝² : PseudoEMetricSpace α
inst✝¹ : Nonempty β
inst✝ : SemilatticeSup β
s : β → α
b : β → ℝ≥0∞
b_bound : ∀ (n m N : β), N ≤ n → N ≤ m → edist (s n) (s m) ≤ b N
b_lim : Tendsto b atTop (𝓝 0)
ε : ℝ≥0∞
εpos : ε > 0
this : ∀ᶠ (n : β) in atTop, b n < ε
N : β
hN : b N < ε
⊢ ∃ N, ∀ (m : β), N ≤ m → ∀ (n : β), N ≤ n → edist (s m) (s n) < ε

Next tactic:
refine ⟨N, fun m hm n hn => ?_⟩