-- Mathlib/Data/Ordmap/Ordset.lean
theorem Valid'.map_aux {β} [Preorder β] {f : α → β} (f_strict_mono : StrictMono f) {t a₁ a₂}
    (h : Valid' a₁ t a₂) :
    Valid' (Option.map f a₁) (map f t) (Option.map f a₂) ∧ (map f t).size = t.size

Proof state:
case node.intro.intro.bal.left
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ BalancedSz (map f l✝).size (map f r✝).size

Tactic:
rw [t_l_size, t_r_size]

Result:
case node.intro.intro.bal.left
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ BalancedSz l✝.size r✝.size

Proof state:
case node.intro.intro.bal.right.right
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ (map f r✝).Balanced

Tactic:
exact t_r_valid.bal

Result:
no goals

Proof state:
case node.intro.intro
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ Valid' (Option.map f a₁) (Ordnode.node size✝ (map f l✝) (f x✝) (map f r✝)) (Option.map f a₂)

Tactic:
constructor

Result:
case node.intro.intro.ord
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ (Ordnode.node size✝ (map f l✝) (f x✝) (map f r✝)).Bounded (Option.map f a₁) (Option.map f a₂)

case node.intro.intro.sz
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ (Ordnode.node size✝ (map f l✝) (f x✝) (map f r✝)).Sized

case node.intro.intro.bal
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ (Ordnode.node size✝ (map f l✝) (f x✝) (map f r✝)).Balanced

Proof state:
case nil
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ nil a₂
⊢ Valid' (Option.map f a₁) nil (Option.map f a₂)

Tactic:
apply valid'_nil

Result:
case nil.h
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ nil a₂
⊢ nil.Bounded (Option.map f a₁) (Option.map f a₂)

Proof state:
case node
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_ih_l' : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝) ∧ (map f l✝).size = l✝.size
t_ih_r' : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂) ∧ (map f r✝).size = r✝.size
⊢ Valid' (Option.map f a₁) (map f (Ordnode.node size✝ l✝ x✝ r✝)) (Option.map f a₂) ∧
    (map f (Ordnode.node size✝ l✝ x✝ r✝)).size = (Ordnode.node size✝ l✝ x✝ r✝).size

Tactic:
obtain ⟨t_l_valid, t_l_size⟩ := t_ih_l'

Result:
case node.intro
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_ih_r' : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂) ∧ (map f r✝).size = r✝.size
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
⊢ Valid' (Option.map f a₁) (map f (Ordnode.node size✝ l✝ x✝ r✝)) (Option.map f a₂) ∧
    (map f (Ordnode.node size✝ l✝ x✝ r✝)).size = (Ordnode.node size✝ l✝ x✝ r✝).size

Proof state:
case node.intro.intro.sz.left
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ size✝ = (map f l✝).size + (map f r✝).size + 1

Tactic:
rw [t_l_size, t_r_size]

Result:
case node.intro.intro.sz.left
α : Type u_1
inst✝¹ : Preorder α
β : Type u_2
inst✝ : Preorder β
f : α → β
f_strict_mono : StrictMono f
size✝ : ℕ
l✝ : Ordnode α
x✝ : α
r✝ : Ordnode α
a₁ : WithBot α
a₂ : WithTop α
h : Valid' a₁ (Ordnode.node size✝ l✝ x✝ r✝) a₂
t_l_valid : Valid' (Option.map f a₁) (map f l✝) (Option.map f ↑x✝)
t_l_size : (map f l✝).size = l✝.size
t_r_valid : Valid' (Option.map f ↑x✝) (map f r✝) (Option.map f a₂)
t_r_size : (map f r✝).size = r✝.size
⊢ size✝ = l✝.size + r✝.size + 1