-- Mathlib/Data/QPF/Multivariate/Constructions/Fix.lean
theorem Fix.ind {α : TypeVec n} (p : Fix F α → Prop)
    (h : ∀ x : F (α.append1 (Fix F α)), LiftP (PredLast α p) x → p (Fix.mk x)) : ∀ x, p x

Proof state:
case a
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.PredLast p ((P F).appendContents f' (fun x => ⟦f x⟧) i j)

Tactic:
intro i j

Result:
case a
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
i : Fin2 (n + 1)
j : (P F).B a i
⊢ α.PredLast p ((P F).appendContents f' (fun x => ⟦f x⟧) i j)

Proof state:
case a.fs
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
a✝ : Fin2 n
j : (P F).B a a✝.fs
⊢ α.PredLast p ((P F).appendContents f' (fun x => ⟦f x⟧) a✝.fs j)

Tactic:
trivial

Result:
no goals

Proof state:
case a
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ LiftP (α.PredLast p) (abs ⟨a, (P F).appendContents f' fun x => ⟦f x⟧⟩)

Tactic:
rw [MvQPF.liftP_iff]

Result:
case a
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ ∃ a_1 f_1,
    abs ⟨a, (P F).appendContents f' fun x => ⟦f x⟧⟩ = abs ⟨a_1, f_1⟩ ∧
      ∀ (i : Fin2 (n + 1)) (j : (P F).B a_1 i), α.PredLast p (f_1 i j)

Proof state:
case mk
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
⊢ p (Quot.mk (⇑(wSetoid α)) x)

Tactic:
apply q.P.w_ind _ x

Result:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
⊢ ∀ (a : (P F).A) (f' : (P F).drop.B a ⟹ α) (f : (P F).last.B a → (P F).W α),
    (∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))) → p (Quot.mk (⇑(wSetoid α)) ((P F).wMk a f' f))

Proof state:
case mk
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
⊢ ∀ (a : (P F).W α), p (Quot.mk (⇑(wSetoid α)) a)

Tactic:
intro x

Result:
case mk
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
⊢ p (Quot.mk (⇑(wSetoid α)) x)

Proof state:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
⊢ ∀ (x : Fix F α), p x

Tactic:
apply Quot.ind

Result:
case mk
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
⊢ ∀ (a : (P F).W α), p (Quot.mk (⇑(wSetoid α)) a)

Proof state:
case a.fz
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
j : (P F).B a Fin2.fz
⊢ α.PredLast p ((P F).appendContents f' (fun x => ⟦f x⟧) Fin2.fz j)

Tactic:
apply ih

Result:
no goals

Proof state:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ p (Quot.mk (⇑(wSetoid α)) ((P F).wMk a f' f))

Tactic:
change p ⟦q.P.wMk a f' f⟧

Result:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ p ⟦(P F).wMk a f' f⟧

Proof state:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ p ⟦(P F).wMk a f' f⟧

Tactic:
rw [← Fix.ind_aux a f' f]

Result:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ p (mk (abs ⟨a, (P F).appendContents f' fun x => ⟦f x⟧⟩))

Proof state:
case a
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ ∃ a_1 f_1,
    abs ⟨a, (P F).appendContents f' fun x => ⟦f x⟧⟩ = abs ⟨a_1, f_1⟩ ∧
      ∀ (i : Fin2 (n + 1)) (j : (P F).B a_1 i), α.PredLast p (f_1 i j)

Tactic:
refine ⟨_, _, rfl, ?_⟩

Result:
case a
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ ∀ (i : Fin2 (n + 1)) (j : (P F).B a i), α.PredLast p ((P F).appendContents f' (fun x => ⟦f x⟧) i j)

Proof state:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
⊢ ∀ (a : (P F).A) (f' : (P F).drop.B a ⟹ α) (f : (P F).last.B a → (P F).W α),
    (∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))) → p (Quot.mk (⇑(wSetoid α)) ((P F).wMk a f' f))

Tactic:
intro a f' f ih

Result:
n : ℕ
F : TypeVec.{u} (n + 1) → Type u
q : MvQPF F
α : TypeVec.{u} n
p : Fix F α → Prop
h : ∀ (x : F (α ::: Fix F α)), LiftP (α.PredLast p) x → p (mk x)
x : (P F).W α
a : (P F).A
f' : (P F).drop.B a ⟹ α
f : (P F).last.B a → (P F).W α
ih : ∀ (i : (P F).last.B a), p (Quot.mk (⇑(wSetoid α)) (f i))
⊢ p (Quot.mk (⇑(wSetoid α)) ((P F).wMk a f' f))