next i_eq_zero =>
simp only [List.length_cons, i_eq_zero, List.get, Nat.add_zero]
case pos
n : Nat
arr : Array (Literal (PosFin n))
arrNodup : ∀ (i j : Fin arr.size), ↑i ≠ ↑j → arr[i] ≠ arr[j]
c : DefaultClause n
h :
  Array.foldr
      (fun l acc =>
        match acc with
        | none => none
        | some acc => acc.insert l)
      (some empty) arr arr.size =
    some c
motive : Nat → Option (DefaultClause n) → Prop :=
  fun idx acc =>
    ∃ idx_le_arr_size,
      ∀ (c' : DefaultClause n),
        acc = some c' →
          ∃ hsize,
            ∀ (i : Fin c'.clause.length),
              let_fun idx_in_bounds := ⋯;
              c'.clause.get i = arr[idx + ↑i]
h_base : motive arr.size (some empty)
fold_fn : Literal (PosFin n) → Option (DefaultClause n) → Option (DefaultClause n) :=
  fun l acc =>
    match acc with
    | none => none
    | some acc => acc.insert l
idx : Fin arr.size
idx_add_one_le_arr_size : ↑idx + 1 ≤ arr.size
c' : DefaultClause n
acc✝ : Option (DefaultClause n)
acc : DefaultClause n
hsize : acc.clause.length = arr.size - (↑idx + 1)
ih : ∀ (i : Fin acc.clause.length), acc.clause.get i = arr[↑idx + 1 + ↑i]
h✝² : ¬acc.clause.contains (arr[↑idx].fst, !arr[↑idx].snd) = true
h✝¹ : ¬acc.clause.contains arr[↑idx] = true
heq : { clause := arr[↑idx] :: acc.clause, nodupkey := ⋯, nodup := ⋯ } = c'
hsize' : c'.clause.length = arr.size - ↑idx
i : Fin c'.clause.length
lhs_rw : c'.clause = arr[↑idx] :: acc.clause
h✝ : ↑i = 0
⊢ (arr[↑idx] :: acc.clause).get ⟨↑i, ⋯⟩ = arr[↑idx + ↑i]
no goals