Module: Mathlib.Computability.PartrecCode

Goal state before:
pp: k k₂ : ℕ
c : Code
n x : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
h : evaln (k + 1) c n = some x
⊢ evaln (k₂ + 1) c n = some x

Tactic:
induction c generalizing x n

Goal state after:
case zero
k k₂ : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
n x : ℕ
h : evaln (k + 1) zero n = some x
⊢ evaln (k₂ + 1) zero n = some x

case succ
k k₂ : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
n x : ℕ
h : evaln (k + 1) succ n = some x
⊢ evaln (k₂ + 1) succ n = some x

case left
k k₂ : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
n x : ℕ
h : evaln (k + 1) left n = some x
⊢ evaln (k₂ + 1) left n = some x

case right
k k₂ : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
n x : ℕ
h : evaln (k + 1) right n = some x
⊢ evaln (k₂ + 1) right n = some x

case pair
k k₂ : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
a✝¹ a✝ : Code
a_ih✝¹ : ∀ (n x : ℕ), evaln (k + 1) a✝¹ n = some x → evaln (k₂ + 1) a✝¹ n = some x
a_ih✝ : ∀ (n x : ℕ), evaln (k + 1) a✝ n = some x → evaln (k₂ + 1) a✝ n = some x
n x : ℕ
h : evaln (k + 1) (a✝¹.pair a✝) n = some x
⊢ evaln (k₂ + 1) (a✝¹.pair a✝) n = some x

case comp
k k₂ : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
a✝¹ a✝ : Code
a_ih✝¹ : ∀ (n x : ℕ), evaln (k + 1) a✝¹ n = some x → evaln (k₂ + 1) a✝¹ n = some x
a_ih✝ : ∀ (n x : ℕ), evaln (k + 1) a✝ n = some x → evaln (k₂ + 1) a✝ n = some x
n x : ℕ
h : evaln (k + 1) (a✝¹.comp a✝) n = some x
⊢ evaln (k₂ + 1) (a✝¹.comp a✝) n = some x

case prec
k k₂ : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
a✝¹ a✝ : Code
a_ih✝¹ : ∀ (n x : ℕ), evaln (k + 1) a✝¹ n = some x → evaln (k₂ + 1) a✝¹ n = some x
a_ih✝ : ∀ (n x : ℕ), evaln (k + 1) a✝ n = some x → evaln (k₂ + 1) a✝ n = some x
n x : ℕ
h : evaln (k + 1) (a✝¹.prec a✝) n = some x
⊢ evaln (k₂ + 1) (a✝¹.prec a✝) n = some x

case rfind'
k k₂ : ℕ
hl : k + 1 ≤ k₂ + 1
hl' : k ≤ k₂
this :
  ∀ {k k₂ n x : ℕ} {o₁ o₂ : Option ℕ},
    k ≤ k₂ →
      (x ∈ o₁ → x ∈ o₂) →
        (x ∈ do
            guard (n ≤ k)
            o₁) →
          x ∈ do
            guard (n ≤ k₂)
            o₂
a✝ : Code
a_ih✝ : ∀ (n x : ℕ), evaln (k + 1) a✝ n = some x → evaln (k₂ + 1) a✝ n = some x
n x : ℕ
h : evaln (k + 1) a✝.rfind' n = some x
⊢ evaln (k₂ + 1) a✝.rfind' n = some x