-- Mathlib/Computability/PostTuringMachine.lean
theorem Machine.map_respects (g₁ : PointedMap Λ Λ') (g₂ : Λ' → Λ) {S} (ss : Supports M S)
    (f₂₁ : Function.RightInverse f₁ f₂) (g₂₁ : ∀ q ∈ S, g₂ (g₁ q) = q) :
    Respects (step M) (step (M.map f₁ f₂ g₁ g₂)) fun a b ↦ a.q ∈ S ∧ Cfg.map f₁ g₁ a = b

Proof state:
case none
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
e : step M c = none
⊢ match none with
  | some b₁ =>
    ∃ b₂,
      (fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b) b₁ b₂ ∧ Reaches₁ (step (M.map f₁ f₂ g₁.f g₂)) (Cfg.map f₁ g₁.f c) b₂
  | none => step (M.map f₁ f₂ g₁.f g₂) (Cfg.map f₁ g₁.f c) = none

Tactic:
rw [← M.map_step f₁ f₂ g₁ g₂ f₂₁ g₂₁ _ cs, e]

Result:
case none
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
e : step M c = none
⊢ match none with
  | some b₁ =>
    ∃ b₂,
      (fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b) b₁ b₂ ∧ Reaches₁ (step (M.map f₁ f₂ g₁.f g₂)) (Cfg.map f₁ g₁.f c) b₂
  | none => Option.map (Cfg.map f₁ g₁.f) none = none

Proof state:
case some
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
val✝ : Cfg Γ Λ
e : step M c = some val✝
⊢ Cfg.map f₁ g₁.f val✝ ∈ step (M.map f₁ f₂ g₁.f g₂) (Cfg.map f₁ g₁.f c)

Tactic:
rw [← M.map_step f₁ f₂ g₁ g₂ f₂₁ g₂₁ _ cs, e]

Result:
case some
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
val✝ : Cfg Γ Λ
e : step M c = some val✝
⊢ Cfg.map f₁ g₁.f val✝ ∈ Option.map (Cfg.map f₁ g₁.f) (some val✝)

Proof state:
case none
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
e : step M c = none
⊢ match none with
  | some b₁ =>
    ∃ b₂,
      (fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b) b₁ b₂ ∧ Reaches₁ (step (M.map f₁ f₂ g₁.f g₂)) (Cfg.map f₁ g₁.f c) b₂
  | none => Option.map (Cfg.map f₁ g₁.f) none = none

Tactic:
rfl

Result:
no goals

Proof state:
case some
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
val✝ : Cfg Γ Λ
e : step M c = some val✝
⊢ match some val✝ with
  | some b₁ =>
    ∃ b₂,
      (fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b) b₁ b₂ ∧ Reaches₁ (step (M.map f₁ f₂ g₁.f g₂)) (Cfg.map f₁ g₁.f c) b₂
  | none => step (M.map f₁ f₂ g₁.f g₂) (Cfg.map f₁ g₁.f c) = none

Tactic:
refine ⟨_, ⟨step_supports M ss e cs, rfl⟩, TransGen.single ?_⟩

Result:
case some
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
val✝ : Cfg Γ Λ
e : step M c = some val✝
⊢ Cfg.map f₁ g₁.f val✝ ∈ step (M.map f₁ f₂ g₁.f g₂) (Cfg.map f₁ g₁.f c)

Proof state:
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
⊢ match step M c with
  | some b₁ =>
    ∃ b₂,
      (fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b) b₁ b₂ ∧ Reaches₁ (step (M.map f₁ f₂ g₁.f g₂)) (Cfg.map f₁ g₁.f c) b₂
  | none => step (M.map f₁ f₂ g₁.f g₂) (Cfg.map f₁ g₁.f c) = none

Tactic:
cases e : step M c

Result:
case none
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
e : step M c = none
⊢ match none with
  | some b₁ =>
    ∃ b₂,
      (fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b) b₁ b₂ ∧ Reaches₁ (step (M.map f₁ f₂ g₁.f g₂)) (Cfg.map f₁ g₁.f c) b₂
  | none => step (M.map f₁ f₂ g₁.f g₂) (Cfg.map f₁ g₁.f c) = none

case some
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
val✝ : Cfg Γ Λ
e : step M c = some val✝
⊢ match some val✝ with
  | some b₁ =>
    ∃ b₂,
      (fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b) b₁ b₂ ∧ Reaches₁ (step (M.map f₁ f₂ g₁.f g₂)) (Cfg.map f₁ g₁.f c) b₂
  | none => step (M.map f₁ f₂ g₁.f g₂) (Cfg.map f₁ g₁.f c) = none

Proof state:
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
⊢ Respects (step M) (step (M.map f₁ f₂ g₁.f g₂)) fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b

Tactic:
intro c _ ⟨cs, rfl⟩

Result:
Γ : Type u_1
inst✝³ : Inhabited Γ
Γ' : Type u_2
inst✝² : Inhabited Γ'
Λ : Type u_3
inst✝¹ : Inhabited Λ
Λ' : Type u_4
inst✝ : Inhabited Λ'
M : Machine Γ Λ
f₁ : PointedMap Γ Γ'
f₂ : PointedMap Γ' Γ
g₁ : PointedMap Λ Λ'
g₂ : Λ' → Λ
S : Set Λ
ss : Supports M S
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁.f q) = q
c : Cfg Γ Λ
a₂✝ : Cfg Γ' Λ'
cs : c.q ∈ S
⊢ match step M c with
  | some b₁ =>
    ∃ b₂,
      (fun a b => a.q ∈ S ∧ Cfg.map f₁ g₁.f a = b) b₁ b₂ ∧ Reaches₁ (step (M.map f₁ f₂ g₁.f g₂)) (Cfg.map f₁ g₁.f c) b₂
  | none => step (M.map f₁ f₂ g₁.f g₂) (Cfg.map f₁ g₁.f c) = none