Theorem: List.mem_permutationsAux2
File: Mathlib/Data/List/Permutation.lean

tactic: induction' ys with y ys ih generalizing l
state_before: α : Type u_1
β : Type ?u.8950
t : α
ts ys l l' : List α
⊢ l' ∈ (permutationsAux2 t ts [] ys fun x => l ++ x).snd ↔
    ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts

tactic: rw [permutationsAux2_snd_cons,
  show (fun x : List α => l ++ y :: x) = (l ++ [y] ++ .) by funext _; simp, mem_cons, ih]
state_before: case cons
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ l' : List α
y : α
ys : List α
ih :
  ∀ {l : List α},
    l' ∈ (permutationsAux2 t ts [] ys fun x => l ++ x).snd ↔
      ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts
l : List α
⊢ l' ∈ (permutationsAux2 t ts [] (y :: ys) fun x => l ++ x).snd ↔
    ∃ l₁ l₂, l₂ ≠ [] ∧ y :: ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts

tactic: constructor
state_before: case cons
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ l' : List α
y : α
ys : List α
ih :
  ∀ {l : List α},
    l' ∈ (permutationsAux2 t ts [] ys fun x => l ++ x).snd ↔
      ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts
l : List α
⊢ (l' = l ++ (t :: y :: ys ++ ts) ∨ ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ [y] ++ l₁ ++ t :: l₂ ++ ts) ↔
    ∃ l₁ l₂, l₂ ≠ [] ∧ y :: ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts

tactic: simp (config := { contextual := true })
state_before: case nil
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ l' l : List α
⊢ l' ∈ (permutationsAux2 t ts [] [] fun x => l ++ x).snd ↔
    ∃ l₁ l₂, l₂ ≠ [] ∧ [] = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts

tactic: funext _
state_before: α : Type u_1
β : Type ?u.8950
t : α
ts l✝ l' : List α
y : α
ys : List α
ih :
  ∀ {l : List α},
    l' ∈ (permutationsAux2 t ts [] ys fun x => l ++ x).snd ↔
      ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts
l : List α
⊢ (fun x => l ++ y :: x) = fun x => l ++ [y] ++ x

tactic: simp
state_before: case h
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ l' : List α
y : α
ys : List α
ih :
  ∀ {l : List α},
    l' ∈ (permutationsAux2 t ts [] ys fun x => l ++ x).snd ↔
      ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts
l x✝ : List α
⊢ l ++ y :: x✝ = l ++ [y] ++ x✝

tactic: rintro (rfl | ⟨l₁, l₂, l0, rfl, rfl⟩)
state_before: case cons.mp
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ l' : List α
y : α
ys : List α
ih :
  ∀ {l : List α},
    l' ∈ (permutationsAux2 t ts [] ys fun x => l ++ x).snd ↔
      ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts
l : List α
⊢ (l' = l ++ (t :: y :: ys ++ ts) ∨ ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ [y] ++ l₁ ++ t :: l₂ ++ ts) →
    ∃ l₁ l₂, l₂ ≠ [] ∧ y :: ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts

tactic: exact ⟨[], y :: ys, by simp⟩
state_before: case cons.mp.inl
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
ys l : List α
ih :
  ∀ {l_1 : List α},
    l ++ (t :: y :: ys ++ ts) ∈ (permutationsAux2 t ts [] ys fun x => l_1 ++ x).snd ↔
      ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l ++ (t :: y :: ys ++ ts) = l_1 ++ l₁ ++ t :: l₂ ++ ts
⊢ ∃ l₁ l₂, l₂ ≠ [] ∧ y :: ys = l₁ ++ l₂ ∧ l ++ (t :: y :: ys ++ ts) = l ++ l₁ ++ t :: l₂ ++ ts

tactic: simp
state_before: α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
ys l : List α
ih :
  ∀ {l_1 : List α},
    l ++ (t :: y :: ys ++ ts) ∈ (permutationsAux2 t ts [] ys fun x => l_1 ++ x).snd ↔
      ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l ++ (t :: y :: ys ++ ts) = l_1 ++ l₁ ++ t :: l₂ ++ ts
⊢ y :: ys ≠ [] ∧ y :: ys = [] ++ y :: ys ∧ l ++ (t :: y :: ys ++ ts) = l ++ [] ++ t :: y :: ys ++ ts

tactic: exact ⟨y :: l₁, l₂, l0, by simp⟩
state_before: case cons.mp.inr.intro.intro.intro.intro
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
l l₁ l₂ : List α
l0 : l₂ ≠ []
ih :
  ∀ {l_1 : List α},
    l ++ [y] ++ l₁ ++ t :: l₂ ++ ts ∈ (permutationsAux2 t ts [] (l₁ ++ l₂) fun x => l_1 ++ x).snd ↔
      ∃ l₁_1 l₂_1,
        l₂_1 ≠ [] ∧ l₁ ++ l₂ = l₁_1 ++ l₂_1 ∧ l ++ [y] ++ l₁ ++ t :: l₂ ++ ts = l_1 ++ l₁_1 ++ t :: l₂_1 ++ ts
⊢ ∃ l₁_1 l₂_1,
    l₂_1 ≠ [] ∧ y :: (l₁ ++ l₂) = l₁_1 ++ l₂_1 ∧ l ++ [y] ++ l₁ ++ t :: l₂ ++ ts = l ++ l₁_1 ++ t :: l₂_1 ++ ts

tactic: simp
state_before: α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
l l₁ l₂ : List α
l0 : l₂ ≠ []
ih :
  ∀ {l_1 : List α},
    l ++ [y] ++ l₁ ++ t :: l₂ ++ ts ∈ (permutationsAux2 t ts [] (l₁ ++ l₂) fun x => l_1 ++ x).snd ↔
      ∃ l₁_1 l₂_1,
        l₂_1 ≠ [] ∧ l₁ ++ l₂ = l₁_1 ++ l₂_1 ∧ l ++ [y] ++ l₁ ++ t :: l₂ ++ ts = l_1 ++ l₁_1 ++ t :: l₂_1 ++ ts
⊢ y :: (l₁ ++ l₂) = y :: l₁ ++ l₂ ∧ l ++ [y] ++ l₁ ++ t :: l₂ ++ ts = l ++ y :: l₁ ++ t :: l₂ ++ ts

tactic: rintro ⟨_ | ⟨y', l₁⟩, l₂, l0, ye, rfl⟩
state_before: case cons.mpr
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ l' : List α
y : α
ys : List α
ih :
  ∀ {l : List α},
    l' ∈ (permutationsAux2 t ts [] ys fun x => l ++ x).snd ↔
      ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts
l : List α
⊢ (∃ l₁ l₂, l₂ ≠ [] ∧ y :: ys = l₁ ++ l₂ ∧ l' = l ++ l₁ ++ t :: l₂ ++ ts) →
    l' = l ++ (t :: y :: ys ++ ts) ∨ ∃ l₁ l₂, l₂ ≠ [] ∧ ys = l₁ ++ l₂ ∧ l' = l ++ [y] ++ l₁ ++ t :: l₂ ++ ts

tactic: simp [ye]
state_before: case cons.mpr.intro.nil.intro.intro.intro
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
ys l l₂ : List α
l0 : l₂ ≠ []
ye : y :: ys = [] ++ l₂
ih :
  ∀ {l_1 : List α},
    l ++ [] ++ t :: l₂ ++ ts ∈ (permutationsAux2 t ts [] ys fun x => l_1 ++ x).snd ↔
      ∃ l₁ l₂_1, l₂_1 ≠ [] ∧ ys = l₁ ++ l₂_1 ∧ l ++ [] ++ t :: l₂ ++ ts = l_1 ++ l₁ ++ t :: l₂_1 ++ ts
⊢ l ++ [] ++ t :: l₂ ++ ts = l ++ (t :: y :: ys ++ ts) ∨
    ∃ l₁ l₂_1, l₂_1 ≠ [] ∧ ys = l₁ ++ l₂_1 ∧ l ++ [] ++ t :: l₂ ++ ts = l ++ [y] ++ l₁ ++ t :: l₂_1 ++ ts

tactic: simp only [cons_append] at ye
state_before: case cons.mpr.intro.cons.intro.intro.intro
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
ys l : List α
y' : α
l₁ l₂ : List α
l0 : l₂ ≠ []
ye : y :: ys = y' :: l₁ ++ l₂
ih :
  ∀ {l_1 : List α},
    l ++ y' :: l₁ ++ t :: l₂ ++ ts ∈ (permutationsAux2 t ts [] ys fun x => l_1 ++ x).snd ↔
      ∃ l₁_1 l₂_1, l₂_1 ≠ [] ∧ ys = l₁_1 ++ l₂_1 ∧ l ++ y' :: l₁ ++ t :: l₂ ++ ts = l_1 ++ l₁_1 ++ t :: l₂_1 ++ ts
⊢ l ++ y' :: l₁ ++ t :: l₂ ++ ts = l ++ (t :: y :: ys ++ ts) ∨
    ∃ l₁_1 l₂_1, l₂_1 ≠ [] ∧ ys = l₁_1 ++ l₂_1 ∧ l ++ y' :: l₁ ++ t :: l₂ ++ ts = l ++ [y] ++ l₁_1 ++ t :: l₂_1 ++ ts

tactic: rcases ye with ⟨rfl, rfl⟩
state_before: case cons.mpr.intro.cons.intro.intro.intro
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
ys l : List α
y' : α
l₁ l₂ : List α
l0 : l₂ ≠ []
ye : y :: ys = y' :: (l₁ ++ l₂)
ih :
  ∀ {l_1 : List α},
    l ++ y' :: l₁ ++ t :: l₂ ++ ts ∈ (permutationsAux2 t ts [] ys fun x => l_1 ++ x).snd ↔
      ∃ l₁_1 l₂_1, l₂_1 ≠ [] ∧ ys = l₁_1 ++ l₂_1 ∧ l ++ y' :: l₁ ++ t :: l₂ ++ ts = l_1 ++ l₁_1 ++ t :: l₂_1 ++ ts
⊢ l ++ y' :: l₁ ++ t :: l₂ ++ ts = l ++ (t :: y :: ys ++ ts) ∨
    ∃ l₁_1 l₂_1, l₂_1 ≠ [] ∧ ys = l₁_1 ++ l₂_1 ∧ l ++ y' :: l₁ ++ t :: l₂ ++ ts = l ++ [y] ++ l₁_1 ++ t :: l₂_1 ++ ts

tactic: exact Or.inr ⟨l₁, l₂, l0, by simp⟩
state_before: case cons.mpr.intro.cons.intro.intro.intro.refl
α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
l l₁ l₂ : List α
l0 : l₂ ≠ []
ih :
  ∀ {l_1 : List α},
    l ++ y :: l₁ ++ t :: l₂ ++ ts ∈ (permutationsAux2 t ts [] (l₁ ++ l₂) fun x => l_1 ++ x).snd ↔
      ∃ l₁_1 l₂_1, l₂_1 ≠ [] ∧ l₁ ++ l₂ = l₁_1 ++ l₂_1 ∧ l ++ y :: l₁ ++ t :: l₂ ++ ts = l_1 ++ l₁_1 ++ t :: l₂_1 ++ ts
⊢ l ++ y :: l₁ ++ t :: l₂ ++ ts = l ++ (t :: y :: (l₁ ++ l₂) ++ ts) ∨
    ∃ l₁_1 l₂_1,
      l₂_1 ≠ [] ∧ l₁ ++ l₂ = l₁_1 ++ l₂_1 ∧ l ++ y :: l₁ ++ t :: l₂ ++ ts = l ++ [y] ++ l₁_1 ++ t :: l₂_1 ++ ts

tactic: simp
state_before: α : Type u_1
β : Type ?u.8950
t : α
ts l✝ : List α
y : α
l l₁ l₂ : List α
l0 : l₂ ≠ []
ih :
  ∀ {l_1 : List α},
    l ++ y :: l₁ ++ t :: l₂ ++ ts ∈ (permutationsAux2 t ts [] (l₁ ++ l₂) fun x => l_1 ++ x).snd ↔
      ∃ l₁_1 l₂_1, l₂_1 ≠ [] ∧ l₁ ++ l₂ = l₁_1 ++ l₂_1 ∧ l ++ y :: l₁ ++ t :: l₂ ++ ts = l_1 ++ l₁_1 ++ t :: l₂_1 ++ ts
⊢ l₁ ++ l₂ = l₁ ++ l₂ ∧ l ++ y :: l₁ ++ t :: l₂ ++ ts = l ++ [y] ++ l₁ ++ t :: l₂ ++ ts