-- Mathlib/.lake/packages/lean4/src/lean/Init/Data/Nat/Linear.lean
theorem Poly.denote_eq_cancelAux (ctx : Context) (fuel : Nat) (m₁ m₂ r₁ r₂ : Poly)
    (h : denote_eq ctx (r₁.reverse ++ m₁, r₂.reverse ++ m₂)) : denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)

Proof state:
case succ
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
m₁ m₂ r₁ r₂ : Poly
h : denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂)
⊢ denote_eq ctx (cancelAux (fuel + 1) m₁ m₂ r₁ r₂)

Tactic:
simp

Result:
case succ
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
m₁ m₂ r₁ r₂ : Poly
h : denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂)
⊢ denote_eq ctx
    (match m₁, m₂ with
    | m₁, [] => (List.reverse r₁ ++ m₁, List.reverse r₂)
    | [], m₂ => (List.reverse r₁, List.reverse r₂ ++ m₂)
    | (k₁, v₁) :: m₁, (k₂, v₂) :: m₂ =>
      bif blt v₁ v₂ then cancelAux fuel m₁ ((k₂, v₂) :: m₂) ((k₁, v₁) :: r₁) r₂
      else
        bif blt v₂ v₁ then cancelAux fuel ((k₁, v₁) :: m₁) m₂ r₁ ((k₂, v₂) :: r₂)
        else
          bif k₁.blt k₂ then cancelAux fuel m₁ m₂ r₁ ((k₂ - k₁, v₁) :: r₂)
          else bif k₂.blt k₁ then cancelAux fuel m₁ m₂ ((k₁ - k₂, v₁) :: r₁) r₂ else cancelAux fuel m₁ m₂ r₁ r₂)

Proof state:
case pos.h
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
m₂ : List (Nat × Var)
hltv hgtv : ¬blt v₁ v₁ = true
hltk : k₁.blt k₂ = true
h : denote ctx r₁ + (denote ctx m₁ + k₁ * Var.denote ctx v₁) = denote ctx r₂ + (denote ctx m₂ + k₂ * Var.denote ctx v₁)
haux : k₁ * Var.denote ctx v₁ ≤ k₂ * Var.denote ctx v₁
⊢ denote ctx r₁ + denote ctx m₁ = denote ctx r₂ + (denote ctx m₂ + (k₂ - k₁) * Var.denote ctx v₁)

Tactic:
rw [Nat.mul_sub_right_distrib, ← Nat.add_assoc, ← Nat.add_sub_assoc haux]

Result:
case pos.h
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
m₂ : List (Nat × Var)
hltv hgtv : ¬blt v₁ v₁ = true
hltk : k₁.blt k₂ = true
h : denote ctx r₁ + (denote ctx m₁ + k₁ * Var.denote ctx v₁) = denote ctx r₂ + (denote ctx m₂ + k₂ * Var.denote ctx v₁)
haux : k₁ * Var.denote ctx v₁ ≤ k₂ * Var.denote ctx v₁
⊢ denote ctx r₁ + denote ctx m₁ = denote ctx r₂ + denote ctx m₂ + k₂ * Var.denote ctx v₁ - k₁ * Var.denote ctx v₁

Proof state:
case neg
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
m₂ : List (Nat × Var)
h : denote_eq ctx (List.reverse r₁ ++ (k₁, v₁) :: m₁, List.reverse r₂ ++ (k₂, v₁) :: m₂)
hltv hgtv : ¬blt v₁ v₁ = true
hltk : ¬k₁.blt k₂ = true
⊢ denote_eq ctx (bif k₂.blt k₁ then cancelAux fuel m₁ m₂ ((k₁ - k₂, v₁) :: r₁) r₂ else cancelAux fuel m₁ m₂ r₁ r₂)

Tactic:
by_cases hgtk : Nat.blt k₂ k₁ <;> simp [hgtk]

Result:
case pos
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
m₂ : List (Nat × Var)
h : denote_eq ctx (List.reverse r₁ ++ (k₁, v₁) :: m₁, List.reverse r₂ ++ (k₂, v₁) :: m₂)
hltv hgtv : ¬blt v₁ v₁ = true
hltk : ¬k₁.blt k₂ = true
hgtk : k₂.blt k₁ = true
⊢ denote_eq ctx (cancelAux fuel m₁ m₂ ((k₁ - k₂, v₁) :: r₁) r₂)

case neg
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
m₂ : List (Nat × Var)
h : denote_eq ctx (List.reverse r₁ ++ (k₁, v₁) :: m₁, List.reverse r₂ ++ (k₂, v₁) :: m₂)
hltv hgtv : ¬blt v₁ v₁ = true
hltk : ¬k₁.blt k₂ = true
hgtk : ¬k₂.blt k₁ = true
⊢ denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)

Proof state:
case succ.h_2
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
m₂ r₁ r₂ m₁✝ m₂✝ : Poly
h : denote_eq ctx (List.reverse r₁ ++ [], List.reverse r₂ ++ m₂)
x✝ : m₂ = [] → False
⊢ denote_eq ctx (List.reverse r₁, List.reverse r₂ ++ m₂)

Tactic:
simp at h

Result:
case succ.h_2
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
m₂ r₁ r₂ m₁✝ m₂✝ : Poly
x✝ : m₂ = [] → False
h : denote_eq ctx (List.reverse r₁, List.reverse r₂ ++ m₂)
⊢ denote_eq ctx (List.reverse r₁, List.reverse r₂ ++ m₂)

Proof state:
case pos.h
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
v₂ : Var
m₂ : List (Nat × Var)
h : denote_eq ctx (List.reverse r₁ ++ (k₁, v₁) :: m₁, List.reverse r₂ ++ (k₂, v₂) :: m₂)
hltv : blt v₁ v₂ = true
⊢ denote_eq ctx (((k₁, v₁) :: r₁).reverse ++ m₁, List.reverse r₂ ++ (k₂, v₂) :: m₂)

Tactic:
simp [denote_eq] at h |-

Result:
case pos.h
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
v₂ : Var
m₂ : List (Nat × Var)
hltv : blt v₁ v₂ = true
h : denote ctx r₁ + (denote ctx m₁ + k₁ * Var.denote ctx v₁) = denote ctx r₂ + (denote ctx m₂ + k₂ * Var.denote ctx v₂)
⊢ denote ctx r₁ + (denote ctx m₁ + k₁ * Var.denote ctx v₁) = denote ctx r₂ + (denote ctx m₂ + k₂ * Var.denote ctx v₂)

Proof state:
case pos.h
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
m₂ : List (Nat × Var)
hltv hgtv : ¬blt v₁ v₁ = true
hltk : ¬k₁.blt k₂ = true
hgtk : k₂.blt k₁ = true
h : denote ctx r₁ + (denote ctx m₁ + k₁ * Var.denote ctx v₁) = denote ctx r₂ + (denote ctx m₂ + k₂ * Var.denote ctx v₁)
haux : k₂ * Var.denote ctx v₁ ≤ k₁ * Var.denote ctx v₁
⊢ denote ctx r₁ + denote ctx m₁ + k₁ * Var.denote ctx v₁ - k₂ * Var.denote ctx v₁ = denote ctx r₂ + denote ctx m₂

Tactic:
apply Nat.sub_eq_of_eq_add

Result:
case pos.h.h
ctx : Context
fuel : Nat
ih :
  ∀ (m₁ m₂ r₁ r₂ : Poly),
    denote_eq ctx (List.reverse r₁ ++ m₁, List.reverse r₂ ++ m₂) → denote_eq ctx (cancelAux fuel m₁ m₂ r₁ r₂)
r₁ r₂ m₁✝ m₂✝ : Poly
k₁ : Nat
v₁ : Var
m₁ : List (Nat × Var)
k₂ : Nat
m₂ : List (Nat × Var)
hltv hgtv : ¬blt v₁ v₁ = true
hltk : ¬k₁.blt k₂ = true
hgtk : k₂.blt k₁ = true
h : denote ctx r₁ + (denote ctx m₁ + k₁ * Var.denote ctx v₁) = denote ctx r₂ + (denote ctx m₂ + k₂ * Var.denote ctx v₁)
haux : k₂ * Var.denote ctx v₁ ≤ k₁ * Var.denote ctx v₁
⊢ denote ctx r₁ + denote ctx m₁ + k₁ * Var.denote ctx v₁ = denote ctx r₂ + denote ctx m₂ + k₂ * Var.denote ctx v₁