l3lab/ntp-mathlib huggingface dataset:
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    

Proof state:
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
⊢ ∃ c, (∀ (x : ↥f.domain), -↑x - y ∈ s → ↑f x ≤ c) ∧ ∀ (x : ↥f.domain), ↑x + y ∈ s → c ≤ ↑f x

Next tactic:
set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    

Proof state:
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
⊢ ∃ c, (∀ (x : ↥f.domain), -↑x - y ∈ s → ↑f x ≤ c) ∧ ∀ (x : ↥f.domain), ↑x + y ∈ s → c ≤ ↑f x

Next tactic:
set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    

Proof state:
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
⊢ ∃ c, (∀ (x : ↥f.domain), -↑x - y ∈ s → ↑f x ≤ c) ∧ ∀ (x : ↥f.domain), ↑x + y ∈ s → c ≤ ↑f x

Next tactic:
suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      

Proof state:
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
this : Set.Nonempty (upperBounds Sn ∩ lowerBounds Sp)
⊢ ∃ c, (∀ (x : ↥f.domain), -↑x - y ∈ s → ↑f x ≤ c) ∧ ∀ (x : ↥f.domain), ↑x + y ∈ s → c ≤ ↑f x

Next tactic:
simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    

Proof state:
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
⊢ Set.Nonempty (upperBounds Sn ∩ lowerBounds Sp)

Next tactic:
refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · 

Proof state:
case refine'_1
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
⊢ Set.Nonempty {x | -↑x - y ∈ s}

Next tactic:
rcases dense (-y) with ⟨x, hx⟩
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · rcases dense (-y) with ⟨x, hx⟩
      

Proof state:
case refine'_1.intro
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
x : ↥f.domain
hx : ↑x + -y ∈ s
⊢ Set.Nonempty {x | -↑x - y ∈ s}

Next tactic:
rw [← neg_neg x, AddSubgroupClass.coe_neg, ← sub_eq_add_neg] at hx
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · rcases dense (-y) with ⟨x, hx⟩
      rw [← neg_neg x, AddSubgroupClass.coe_neg, ← sub_eq_add_neg] at hx
      

Proof state:
case refine'_1.intro
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
x : ↥f.domain
hx : -↑(-x) - y ∈ s
⊢ Set.Nonempty {x | -↑x - y ∈ s}

Next tactic:
exact ⟨_, hx⟩
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · rcases dense (-y) with ⟨x, hx⟩
      rw [← neg_neg x, AddSubgroupClass.coe_neg, ← sub_eq_add_neg] at hx
      exact ⟨_, hx⟩
    

Proof state:
case refine'_2
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
⊢ ∀ x ∈ Sn, ∀ y ∈ Sp, x ≤ y

Next tactic:
rintro a ⟨xn, hxn, rfl⟩ b ⟨xp, hxp, rfl⟩
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · rcases dense (-y) with ⟨x, hx⟩
      rw [← neg_neg x, AddSubgroupClass.coe_neg, ← sub_eq_add_neg] at hx
      exact ⟨_, hx⟩
    rintro a ⟨xn, hxn, rfl⟩ b ⟨xp, hxp, rfl⟩
    

Proof state:
case refine'_2.intro.intro.intro.intro
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
xn : ↥f.domain
hxn : xn ∈ {x | -↑x - y ∈ s}
xp : ↥f.domain
hxp : xp ∈ {x | ↑x + y ∈ s}
⊢ ↑f xn ≤ ↑f xp

Next tactic:
have := s.add_mem hxp hxn
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · rcases dense (-y) with ⟨x, hx⟩
      rw [← neg_neg x, AddSubgroupClass.coe_neg, ← sub_eq_add_neg] at hx
      exact ⟨_, hx⟩
    rintro a ⟨xn, hxn, rfl⟩ b ⟨xp, hxp, rfl⟩
    have := s.add_mem hxp hxn
    

Proof state:
case refine'_2.intro.intro.intro.intro
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
xn : ↥f.domain
hxn : xn ∈ {x | -↑x - y ∈ s}
xp : ↥f.domain
hxp : xp ∈ {x | ↑x + y ∈ s}
this : ↑xp + y + (-↑xn - y) ∈ s
⊢ ↑f xn ≤ ↑f xp

Next tactic:
rw [add_assoc, add_sub_cancel'_right, ← sub_eq_add_neg, ← AddSubgroupClass.coe_sub] at this
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · rcases dense (-y) with ⟨x, hx⟩
      rw [← neg_neg x, AddSubgroupClass.coe_neg, ← sub_eq_add_neg] at hx
      exact ⟨_, hx⟩
    rintro a ⟨xn, hxn, rfl⟩ b ⟨xp, hxp, rfl⟩
    have := s.add_mem hxp hxn
    rw [add_assoc, add_sub_cancel'_right, ← sub_eq_add_neg, ← AddSubgroupClass.coe_sub] at this
    

Proof state:
case refine'_2.intro.intro.intro.intro
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
xn : ↥f.domain
hxn : xn ∈ {x | -↑x - y ∈ s}
xp : ↥f.domain
hxp : xp ∈ {x | ↑x + y ∈ s}
this : ↑(xp - xn) ∈ s
⊢ ↑f xn ≤ ↑f xp

Next tactic:
replace := nonneg _ this
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · rcases dense (-y) with ⟨x, hx⟩
      rw [← neg_neg x, AddSubgroupClass.coe_neg, ← sub_eq_add_neg] at hx
      exact ⟨_, hx⟩
    rintro a ⟨xn, hxn, rfl⟩ b ⟨xp, hxp, rfl⟩
    have := s.add_mem hxp hxn
    rw [add_assoc, add_sub_cancel'_right, ← sub_eq_add_neg, ← AddSubgroupClass.coe_sub] at this
    replace := nonneg _ this
    

Proof state:
case refine'_2.intro.intro.intro.intro
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
Sp : Set ℝ := ↑f '' {x | ↑x + y ∈ s}
Sn : Set ℝ := ↑f '' {x | -↑x - y ∈ s}
xn : ↥f.domain
hxn : xn ∈ {x | -↑x - y ∈ s}
xp : ↥f.domain
hxp : xp ∈ {x | ↑x + y ∈ s}
this : 0 ≤ ↑f (xp - xn)
⊢ ↑f xn ≤ ↑f xp

Next tactic:
rwa [f.map_sub, sub_nonneg] at this
/-- Induction step in M. Riesz extension theorem. Given a convex cone `s` in a vector space `E`,
a partially defined linear map `f : f.domain → ℝ`, assume that `f` is nonnegative on `f.domain ∩ p`
and `p + s = E`. If `f` is not defined on the whole `E`, then we can extend it to a larger
submodule without breaking the non-negativity condition. -/
theorem step (nonneg : ∀ x : f.domain, (x : E) ∈ s → 0 ≤ f x)
    (dense : ∀ y, ∃ x : f.domain, (x : E) + y ∈ s) (hdom : f.domain ≠ ⊤) :
    ∃ g, f < g ∧ ∀ x : g.domain, (x : E) ∈ s → 0 ≤ g x := by
  obtain ⟨y, -, hy⟩ : ∃ y ∈ ⊤, y ∉ f.domain :=
    @SetLike.exists_of_lt (Submodule ℝ E) _ _ _ _ (lt_top_iff_ne_top.2 hdom)
  obtain ⟨c, le_c, c_le⟩ :
      ∃ c, (∀ x : f.domain, -(x : E) - y ∈ s → f x ≤ c) ∧
        ∀ x : f.domain, (x : E) + y ∈ s → c ≤ f x := by
    set Sp := f '' { x : f.domain | (x : E) + y ∈ s }
    set Sn := f '' { x : f.domain | -(x : E) - y ∈ s }
    suffices (upperBounds Sn ∩ lowerBounds Sp).Nonempty by
      simpa only [Set.Nonempty, upperBounds, lowerBounds, ball_image_iff] using this
    refine' exists_between_of_forall_le (Nonempty.image f _) (Nonempty.image f (dense y)) _
    · rcases dense (-y) with ⟨x, hx⟩
      rw [← neg_neg x, AddSubgroupClass.coe_neg, ← sub_eq_add_neg] at hx
      exact ⟨_, hx⟩
    rintro a ⟨xn, hxn, rfl⟩ b ⟨xp, hxp, rfl⟩
    have := s.add_mem hxp hxn
    rw [add_assoc, add_sub_cancel'_right, ← sub_eq_add_neg, ← AddSubgroupClass.coe_sub] at this
    replace := nonneg _ this
    rwa [f.map_sub, sub_nonneg] at this
  -- Porting note: removed an unused `have`
  

Proof state:
case intro.intro.intro.intro
𝕜 : Type u_1
E : Type u_2
F : Type u_3
G : Type u_4
inst✝¹ : AddCommGroup E
inst✝ : Module ℝ E
s : ConvexCone ℝ E
f : E →ₗ.[ℝ] ℝ
nonneg : ∀ (x : ↥f.domain), ↑x ∈ s → 0 ≤ ↑f x
dense : ∀ (y : E), ∃ x, ↑x + y ∈ s
hdom : f.domain ≠ ⊤
y : E
hy : y ∉ f.domain
c : ℝ
le_c : ∀ (x : ↥f.domain), -↑x - y ∈ s → ↑f x ≤ c
c_le : ∀ (x : ↥f.domain), ↑x + y ∈ s → c ≤ ↑f x
⊢ ∃ g, f < g ∧ ∀ (x : ↥g.domain), ↑x ∈ s → 0 ≤ ↑g x

Next tactic:
refine' ⟨f.supSpanSingleton y (-c) hy, _, _⟩