Module: Mathlib.Computability.TuringMachine.PostTuringMachine

Goal state before:
pp: 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 : Λ → Λ'
g₂ : Λ' → Λ
S : Set Λ
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁ q) = q
q : Λ
T : Tape Γ
h : { q := q, Tape := T }.q ∈ S
⊢ Option.map (fun x ↦ { q := g₁ x.q, Tape := Tape.map f₁ x.Tape })
      (Option.map
        (fun x ↦
          { q := x.1,
            Tape :=
              match x.2 with
              | Stmt.move d => Tape.move d T
              | Stmt.write a => Tape.write a T })
        (M q T.head)) =
    Option.map
      (fun x ↦
        { q := x.1,
          Tape :=
            match x.2 with
            | Stmt.move d => Tape.move d (Tape.map f₁ T)
            | Stmt.write a => Tape.write a (Tape.map f₁ T) })
      (Option.map (Prod.map g₁ (Stmt.map f₁)) (M q T.head))

Tactic:
rcases M q T.1 with (_ | ⟨q', d | a⟩)

Goal state after:
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 : Λ → Λ'
g₂ : Λ' → Λ
S : Set Λ
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁ q) = q
q : Λ
T : Tape Γ
h : { q := q, Tape := T }.q ∈ S
⊢ Option.map (fun x ↦ { q := g₁ x.q, Tape := Tape.map f₁ x.Tape })
      (Option.map
        (fun x ↦
          { q := x.1,
            Tape :=
              match x.2 with
              | Stmt.move d => Tape.move d T
              | Stmt.write a => Tape.write a T })
        none) =
    Option.map
      (fun x ↦
        { q := x.1,
          Tape :=
            match x.2 with
            | Stmt.move d => Tape.move d (Tape.map f₁ T)
            | Stmt.write a => Tape.write a (Tape.map f₁ T) })
      (Option.map (Prod.map g₁ (Stmt.map f₁)) none)

case some.move
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 : Λ → Λ'
g₂ : Λ' → Λ
S : Set Λ
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁ q) = q
q : Λ
T : Tape Γ
h : { q := q, Tape := T }.q ∈ S
q' : Λ
d : Dir
⊢ Option.map (fun x ↦ { q := g₁ x.q, Tape := Tape.map f₁ x.Tape })
      (Option.map
        (fun x ↦
          { q := x.1,
            Tape :=
              match x.2 with
              | Stmt.move d => Tape.move d T
              | Stmt.write a => Tape.write a T })
        (some (q', Stmt.move d))) =
    Option.map
      (fun x ↦
        { q := x.1,
          Tape :=
            match x.2 with
            | Stmt.move d => Tape.move d (Tape.map f₁ T)
            | Stmt.write a => Tape.write a (Tape.map f₁ T) })
      (Option.map (Prod.map g₁ (Stmt.map f₁)) (some (q', Stmt.move d)))

case some.write
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 : Λ → Λ'
g₂ : Λ' → Λ
S : Set Λ
f₂₁ : Function.RightInverse f₁.f f₂.f
g₂₁ : ∀ q ∈ S, g₂ (g₁ q) = q
q : Λ
T : Tape Γ
h : { q := q, Tape := T }.q ∈ S
q' : Λ
a : Γ
⊢ Option.map (fun x ↦ { q := g₁ x.q, Tape := Tape.map f₁ x.Tape })
      (Option.map
        (fun x ↦
          { q := x.1,
            Tape :=
              match x.2 with
              | Stmt.move d => Tape.move d T
              | Stmt.write a => Tape.write a T })
        (some (q', Stmt.write a))) =
    Option.map
      (fun x ↦
        { q := x.1,
          Tape :=
            match x.2 with
            | Stmt.move d => Tape.move d (Tape.map f₁ T)
            | Stmt.write a => Tape.write a (Tape.map f₁ T) })
      (Option.map (Prod.map g₁ (Stmt.map f₁)) (some (q', Stmt.write a)))