rcases i with ⟨val, hyp⟩
case a
Worlds : Finset (Finset Formula)
MG : ModelGraph Worlds
X Y : { x // x ∈ Worlds }
δ : List Program
φ : Formula
l : List { x // x ∈ Worlds }
length_def : l.length + 1 = δ.length
δφ_in_X : (⌈⌈δ⌉⌉φ) ∈ ↑X
i : Fin (l.append [Y]).length
lchain :
  ∀ (i : ℕ) (h : i < (((?'⊤) :: δ).zip (X :: (l ++ [Y]))).length - 1),
    pairRel (↑MG) ((((?'⊤) :: δ).zip (X :: (l ++ [Y]))).get ⟨i, ⋯⟩)
      ((((?'⊤) :: δ).zip (X :: (l ++ [Y]))).get ⟨i + 1, ⋯⟩)
IHδ : ∀ d ∈ δ, ∀ (X' Y' : { x // x ∈ Worlds }) (φ' : Formula), (⌈d⌉φ') ∈ ↑X' → relate (↑MG) d X' Y' → φ' ∈ ↑Y'
IH : (⌈⌈List.drop (↑i.castSucc) δ⌉⌉φ) ∈ ↑((X :: (l ++ [Y])).get i.castSucc)
help1 : (l.append [Y]).length = δ.length
⊢ ↑i < (((?'⊤) :: δ).zip (X :: (l ++ [Y]))).length - 1
case a.mk
Worlds : Finset (Finset Formula)
MG : ModelGraph Worlds
X Y : { x // x ∈ Worlds }
δ : List Program
φ : Formula
l : List { x // x ∈ Worlds }
length_def : l.length + 1 = δ.length
δφ_in_X : (⌈⌈δ⌉⌉φ) ∈ ↑X
lchain :
  ∀ (i : ℕ) (h : i < (((?'⊤) :: δ).zip (X :: (l ++ [Y]))).length - 1),
    pairRel (↑MG) ((((?'⊤) :: δ).zip (X :: (l ++ [Y]))).get ⟨i, ⋯⟩)
      ((((?'⊤) :: δ).zip (X :: (l ++ [Y]))).get ⟨i + 1, ⋯⟩)
IHδ : ∀ d ∈ δ, ∀ (X' Y' : { x // x ∈ Worlds }) (φ' : Formula), (⌈d⌉φ') ∈ ↑X' → relate (↑MG) d X' Y' → φ' ∈ ↑Y'
help1 : (l.append [Y]).length = δ.length
val : ℕ
hyp : val < (l.append [Y]).length
IH : (⌈⌈List.drop (↑⟨val, hyp⟩.castSucc) δ⌉⌉φ) ∈ ↑((X :: (l ++ [Y])).get ⟨val, hyp⟩.castSucc)
⊢ ↑⟨val, hyp⟩ < (((?'⊤) :: δ).zip (X :: (l ++ [Y]))).length - 1