Module: Mathlib.Computability.TuringMachine.ToPartrec

Goal state before:
pp: case cons.nil
p : Γ' → Bool
k₁ k₂ : K'
q : Λ'
o : Option Γ'
L₂ : List Γ'
h₁ : k₁ ≠ k₂
a : Γ'
L₁ : List Γ'
IH :
  ∀ {s : Option Γ'} {S : K' → List Γ'},
    splitAtPred p (S k₁) = (L₁, o, L₂) →
      Reaches₁ (TM2.step tr) { l := some (Λ'.move p k₁ k₂ q), var := s, stk := S }
        { l := some q, var := o, stk := update (update S k₁ L₂) k₂ (L₁.reverseAux (S k₂)) }
s : Option Γ'
S : K' → List Γ'
e : splitAtPred p (S k₁) = (a :: L₁, o, L₂)
e₁ : S k₁ = []
⊢ TransGen (fun a b ↦ b ∈ TM2.step tr a)
    (bif
        match [].head?, true, p with
        | some x, x_1, f => f x
        | none, y, x => y then
      { l := some q, var := [].head?, stk := update S k₁ [].tail }
    else
      { l := some (Λ'.move p k₁ k₂ q), var := [].head?,
        stk := update (update S k₁ [].tail) k₂ ([].head?.getD default :: update S k₁ [].tail k₂) })
    { l := some q, var := o, stk := update (update S k₁ L₂) k₂ ((a :: L₁).reverseAux (S k₂)) }

pp: case cons.cons
p : Γ' → Bool
k₁ k₂ : K'
q : Λ'
o : Option Γ'
L₂ : List Γ'
h₁ : k₁ ≠ k₂
a : Γ'
L₁ : List Γ'
IH :
  ∀ {s : Option Γ'} {S : K' → List Γ'},
    splitAtPred p (S k₁) = (L₁, o, L₂) →
      Reaches₁ (TM2.step tr) { l := some (Λ'.move p k₁ k₂ q), var := s, stk := S }
        { l := some q, var := o, stk := update (update S k₁ L₂) k₂ (L₁.reverseAux (S k₂)) }
s : Option Γ'
S : K' → List Γ'
e : splitAtPred p (S k₁) = (a :: L₁, o, L₂)
a' : Γ'
Sk : List Γ'
e₁ : S k₁ = a' :: Sk
⊢ TransGen (fun a b ↦ b ∈ TM2.step tr a)
    (bif
        match (a' :: Sk).head?, true, p with
        | some x, x_1, f => f x
        | none, y, x => y then
      { l := some q, var := (a' :: Sk).head?, stk := update S k₁ (a' :: Sk).tail }
    else
      { l := some (Λ'.move p k₁ k₂ q), var := (a' :: Sk).head?,
        stk :=
          update (update S k₁ (a' :: Sk).tail) k₂ ((a' :: Sk).head?.getD default :: update S k₁ (a' :: Sk).tail k₂) })
    { l := some q, var := o, stk := update (update S k₁ L₂) k₂ ((a :: L₁).reverseAux (S k₂)) }

Tactic:
<;>

Goal state after:
case cons.nil
p : Γ' → Bool
k₁ k₂ : K'
q : Λ'
o : Option Γ'
L₂ : List Γ'
h₁ : k₁ ≠ k₂
a : Γ'
L₁ : List Γ'
IH :
  ∀ {s : Option Γ'} {S : K' → List Γ'},
    splitAtPred p (S k₁) = (L₁, o, L₂) →
      Reaches₁ (TM2.step tr) { l := some (Λ'.move p k₁ k₂ q), var := s, stk := S }
        { l := some q, var := o, stk := update (update S k₁ L₂) k₂ (L₁.reverseAux (S k₂)) }
s : Option Γ'
S : K' → List Γ'
e : splitAtPred p (S k₁) = (a :: L₁, o, L₂)
e₁ : S k₁ = []
⊢ TransGen (fun a b ↦ b ∈ TM2.step tr a)
    (bif
        match [].head?, true, p with
        | some x, x_1, f => f x
        | none, y, x => y then
      { l := some q, var := [].head?, stk := update S k₁ [].tail }
    else
      { l := some (Λ'.move p k₁ k₂ q), var := [].head?,
        stk := update (update S k₁ [].tail) k₂ ([].head?.getD default :: update S k₁ [].tail k₂) })
    { l := some q, var := o, stk := update (update S k₁ L₂) k₂ ((a :: L₁).reverseAux (S k₂)) }

case cons.cons
p : Γ' → Bool
k₁ k₂ : K'
q : Λ'
o : Option Γ'
L₂ : List Γ'
h₁ : k₁ ≠ k₂
a : Γ'
L₁ : List Γ'
IH :
  ∀ {s : Option Γ'} {S : K' → List Γ'},
    splitAtPred p (S k₁) = (L₁, o, L₂) →
      Reaches₁ (TM2.step tr) { l := some (Λ'.move p k₁ k₂ q), var := s, stk := S }
        { l := some q, var := o, stk := update (update S k₁ L₂) k₂ (L₁.reverseAux (S k₂)) }
s : Option Γ'
S : K' → List Γ'
e : splitAtPred p (S k₁) = (a :: L₁, o, L₂)
a' : Γ'
Sk : List Γ'
e₁ : S k₁ = a' :: Sk
⊢ TransGen (fun a b ↦ b ∈ TM2.step tr a)
    (bif
        match (a' :: Sk).head?, true, p with
        | some x, x_1, f => f x
        | none, y, x => y then
      { l := some q, var := (a' :: Sk).head?, stk := update S k₁ (a' :: Sk).tail }
    else
      { l := some (Λ'.move p k₁ k₂ q), var := (a' :: Sk).head?,
        stk :=
          update (update S k₁ (a' :: Sk).tail) k₂ ((a' :: Sk).head?.getD default :: update S k₁ (a' :: Sk).tail k₂) })
    { l := some q, var := o, stk := update (update S k₁ L₂) k₂ ((a :: L₁).reverseAux (S k₂)) }