Theorem: Filter.HasBasis.liminf_eq_ite
File: Mathlib/Order/LiminfLimsup.lean

Proof steps:
state_before: α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
⊢ liminf f v =
    if ∃ j, s ↑j = ∅ then sSup univ
    else if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i
state_after: case pos
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ∃ j, s ↑j = ∅
⊢ liminf f v =
    if ∃ j, s ↑j = ∅ then sSup univ
    else if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i

case neg
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
⊢ liminf f v =
    if ∃ j, s ↑j = ∅ then sSup univ
    else if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i
tactic: by_cases H : ∃ (j : Subtype p), s j = ∅
state_before: case neg
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
⊢ liminf f v =
    if ∃ j, s ↑j = ∅ then sSup univ
    else if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i
state_after: case neg
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
⊢ liminf f v = if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i
tactic: rw [if_neg H]
state_before: case neg
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
⊢ liminf f v = if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i
state_after: case pos
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
H' : ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i)
⊢ liminf f v = if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i

case neg
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
H' : ¬∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i)
⊢ liminf f v = if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i
tactic: by_cases H' : ∀ (j : Subtype p), ¬BddBelow (range (fun (i : s j) ↦ f i))
state_before: case neg
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
H' : ¬∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i)
⊢ liminf f v = if ∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i) then sSup ∅ else ⨆ j, ⨅ i, f ↑i
state_after: case neg
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
H' : ¬∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i)
⊢ liminf f v = ⨆ j, ⨅ i, f ↑i
tactic: rw [if_neg H']
state_before: case neg
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
H' : ¬∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i)
⊢ liminf f v = ⨆ j, ⨅ i, f ↑i
state_after: case neg.hs
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
H' : ¬∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i)
⊢ ∀ (j : Subtype p), (s ↑j).Nonempty

case neg.H
α : Type u_1
β : Type u_2
γ : Type u_3
ι : Type u_4
ι' : Type u_5
inst✝² : ConditionallyCompleteLinearOrder α
f✝ : Filter α
b : α
v : Filter ι
p : ι' → Prop
s : ι' → Set ι
inst✝¹ : Countable (Subtype p)
inst✝ : Nonempty (Subtype p)
hv : v.HasBasis p s
f : ι → α
H : ¬∃ j, s ↑j = ∅
H' : ¬∀ (j : Subtype p), ¬BddBelow (range fun i => f ↑i)
⊢ ∃ j, BddBelow (range fun i => f ↑i)
tactic: apply hv.liminf_eq_ciSup_ciInf