-- Mathlib/Topology/MetricSpace/GromovHausdorffRealized.lean
theorem closed_candidatesB : IsClosed (candidatesB X Y)

Proof state:
X : Type u
Y : Type v
inst✝¹ : MetricSpace X
inst✝ : MetricSpace Y
I1 : ∀ (x y : X), IsClosed {f | f (inl x, inl y) = dist x y}
I2 : ∀ (x y : Y), IsClosed {f | f (inr x, inr y) = dist x y}
I3 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) = f (y, x)}
I4 : ∀ (x y z : X ⊕ Y), IsClosed {f | f (x, z) ≤ f (x, y) + f (y, z)}
I5 : ∀ (x : X ⊕ Y), IsClosed {f | f (x, x) = 0}
I6 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
this :
  GromovHausdorff.candidatesB X Y =
    (((((⋂ x, ⋂ y, {f | f (inl x, inl y) = dist x y}) ∩ ⋂ x, ⋂ y, {f | f (inr x, inr y) = dist x y}) ∩
            ⋂ x, ⋂ y, {f | f (x, y) = f (y, x)}) ∩
          ⋂ x, ⋂ y, ⋂ z, {f | f (x, z) ≤ f (x, y) + f (y, z)}) ∩
        ⋂ x, {f | f (x, x) = 0}) ∩
      ⋂ x, ⋂ y, {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
x✝¹ x✝ x : X ⊕ Y
⊢ IsClosed {f | f (x✝¹, x) ≤ f (x✝¹, x✝) + f (x✝, x)}

Tactic:
apply I4 _ _ _

Result:
no goals

Proof state:
X : Type u
Y : Type v
inst✝¹ : MetricSpace X
inst✝ : MetricSpace Y
I1 : ∀ (x y : X), IsClosed {f | f (inl x, inl y) = dist x y}
I2 : ∀ (x y : Y), IsClosed {f | f (inr x, inr y) = dist x y}
I3 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) = f (y, x)}
I4 : ∀ (x y z : X ⊕ Y), IsClosed {f | f (x, z) ≤ f (x, y) + f (y, z)}
I5 : ∀ (x : X ⊕ Y), IsClosed {f | f (x, x) = 0}
I6 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
this :
  GromovHausdorff.candidatesB X Y =
    (((((⋂ x, ⋂ y, {f | f (inl x, inl y) = dist x y}) ∩ ⋂ x, ⋂ y, {f | f (inr x, inr y) = dist x y}) ∩
            ⋂ x, ⋂ y, {f | f (x, y) = f (y, x)}) ∩
          ⋂ x, ⋂ y, ⋂ z, {f | f (x, z) ≤ f (x, y) + f (y, z)}) ∩
        ⋂ x, {f | f (x, x) = 0}) ∩
      ⋂ x, ⋂ y, {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
⊢ IsClosed (GromovHausdorff.candidatesB X Y)

Tactic:
rw [this]

Result:
X : Type u
Y : Type v
inst✝¹ : MetricSpace X
inst✝ : MetricSpace Y
I1 : ∀ (x y : X), IsClosed {f | f (inl x, inl y) = dist x y}
I2 : ∀ (x y : Y), IsClosed {f | f (inr x, inr y) = dist x y}
I3 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) = f (y, x)}
I4 : ∀ (x y z : X ⊕ Y), IsClosed {f | f (x, z) ≤ f (x, y) + f (y, z)}
I5 : ∀ (x : X ⊕ Y), IsClosed {f | f (x, x) = 0}
I6 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
this :
  GromovHausdorff.candidatesB X Y =
    (((((⋂ x, ⋂ y, {f | f (inl x, inl y) = dist x y}) ∩ ⋂ x, ⋂ y, {f | f (inr x, inr y) = dist x y}) ∩
            ⋂ x, ⋂ y, {f | f (x, y) = f (y, x)}) ∩
          ⋂ x, ⋂ y, ⋂ z, {f | f (x, z) ≤ f (x, y) + f (y, z)}) ∩
        ⋂ x, {f | f (x, x) = 0}) ∩
      ⋂ x, ⋂ y, {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
⊢ IsClosed
    ((((((⋂ x, ⋂ y, {f | f (inl x, inl y) = dist x y}) ∩ ⋂ x, ⋂ y, {f | f (inr x, inr y) = dist x y}) ∩
            ⋂ x, ⋂ y, {f | f (x, y) = f (y, x)}) ∩
          ⋂ x, ⋂ y, ⋂ z, {f | f (x, z) ≤ f (x, y) + f (y, z)}) ∩
        ⋂ x, {f | f (x, x) = 0}) ∩
      ⋂ x, ⋂ y, {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)})

Proof state:
X : Type u
Y : Type v
inst✝¹ : MetricSpace X
inst✝ : MetricSpace Y
I1 : ∀ (x y : X), IsClosed {f | f (inl x, inl y) = dist x y}
I2 : ∀ (x y : Y), IsClosed {f | f (inr x, inr y) = dist x y}
I3 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) = f (y, x)}
I4 : ∀ (x y z : X ⊕ Y), IsClosed {f | f (x, z) ≤ f (x, y) + f (y, z)}
⊢ IsClosed (GromovHausdorff.candidatesB X Y)

Tactic:
have I5 : ∀ x, IsClosed { f : Cb X Y | f (x, x) = 0 } := fun x =>
  isClosed_eq continuous_eval_const continuous_const

Result:
X : Type u
Y : Type v
inst✝¹ : MetricSpace X
inst✝ : MetricSpace Y
I1 : ∀ (x y : X), IsClosed {f | f (inl x, inl y) = dist x y}
I2 : ∀ (x y : Y), IsClosed {f | f (inr x, inr y) = dist x y}
I3 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) = f (y, x)}
I4 : ∀ (x y z : X ⊕ Y), IsClosed {f | f (x, z) ≤ f (x, y) + f (y, z)}
I5 : ∀ (x : X ⊕ Y), IsClosed {f | f (x, x) = 0}
⊢ IsClosed (GromovHausdorff.candidatesB X Y)

Proof state:
X : Type u
Y : Type v
inst✝¹ : MetricSpace X
inst✝ : MetricSpace Y
I1 : ∀ (x y : X), IsClosed {f | f (inl x, inl y) = dist x y}
I2 : ∀ (x y : Y), IsClosed {f | f (inr x, inr y) = dist x y}
I3 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) = f (y, x)}
I4 : ∀ (x y z : X ⊕ Y), IsClosed {f | f (x, z) ≤ f (x, y) + f (y, z)}
I5 : ∀ (x : X ⊕ Y), IsClosed {f | f (x, x) = 0}
I6 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
this :
  GromovHausdorff.candidatesB X Y =
    (((((⋂ x, ⋂ y, {f | f (inl x, inl y) = dist x y}) ∩ ⋂ x, ⋂ y, {f | f (inr x, inr y) = dist x y}) ∩
            ⋂ x, ⋂ y, {f | f (x, y) = f (y, x)}) ∩
          ⋂ x, ⋂ y, ⋂ z, {f | f (x, z) ≤ f (x, y) + f (y, z)}) ∩
        ⋂ x, {f | f (x, x) = 0}) ∩
      ⋂ x, ⋂ y, {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
⊢ IsClosed
    ((((((⋂ x, ⋂ y, {f | f (inl x, inl y) = dist x y}) ∩ ⋂ x, ⋂ y, {f | f (inr x, inr y) = dist x y}) ∩
            ⋂ x, ⋂ y, {f | f (x, y) = f (y, x)}) ∩
          ⋂ x, ⋂ y, ⋂ z, {f | f (x, z) ≤ f (x, y) + f (y, z)}) ∩
        ⋂ x, {f | f (x, x) = 0}) ∩
      ⋂ x, ⋂ y, {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)})

Tactic:
repeat'
  first
    |apply IsClosed.inter _ _
    |apply isClosed_iInter _
    |apply I1 _ _|apply I2 _ _|apply I3 _ _|apply I4 _ _ _|apply I5 _|apply I6 _ _|intro x

Result:
no goals

Proof state:
case h
X : Type u
Y : Type v
inst✝¹ : MetricSpace X
inst✝ : MetricSpace Y
I1 : ∀ (x y : X), IsClosed {f | f (inl x, inl y) = dist x y}
I2 : ∀ (x y : Y), IsClosed {f | f (inr x, inr y) = dist x y}
I3 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) = f (y, x)}
I4 : ∀ (x y z : X ⊕ Y), IsClosed {f | f (x, z) ≤ f (x, y) + f (y, z)}
I5 : ∀ (x : X ⊕ Y), IsClosed {f | f (x, x) = 0}
I6 : ∀ (x y : X ⊕ Y), IsClosed {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}
x✝ : GromovHausdorff.Cb X Y
⊢ x✝ ∈ GromovHausdorff.candidatesB X Y ↔
    x✝ ∈
      (((((⋂ x, ⋂ y, {f | f (inl x, inl y) = dist x y}) ∩ ⋂ x, ⋂ y, {f | f (inr x, inr y) = dist x y}) ∩
              ⋂ x, ⋂ y, {f | f (x, y) = f (y, x)}) ∩
            ⋂ x, ⋂ y, ⋂ z, {f | f (x, z) ≤ f (x, y) + f (y, z)}) ∩
          ⋂ x, {f | f (x, x) = 0}) ∩
        ⋂ x, ⋂ y, {f | f (x, y) ≤ ↑(GromovHausdorff.maxVar X Y)}

Tactic:
simp only [candidatesB, candidates, mem_inter_iff, mem_iInter, mem_setOf_eq]

Result:
no goals