Module: Mathlib.SetTheory.Ordinal.Notation

Goal state before:
pp: case oadd.inl.none.inl.some.succ
a : ONote
m : ℕ+
b : ONote
ihb : b = 0
e✝ : b.fundamentalSequence = Sum.inl none
a' : ONote
iha : a.repr = succ a'.repr ∧ (a.NF → a'.NF)
e : a.fundamentalSequence = Sum.inl (some a')
m' : ℕ
e' : m.natPred = m' + 1
⊢ IsSuccLimit (ω ^ a'.repr * ω * ↑m' + ω ^ a'.repr * ω + ω ^ a'.repr * ω) ∧
    (∀ (i : ℕ),
        0 < ω ^ a'.repr ∧
          ω ^ a'.repr * ↑i + ω ^ a'.repr < ω ^ a'.repr * ω ∧
            ((a.oadd (m' + 1).succPNat 0).NF → (a.oadd m'.succPNat (a'.oadd i.succPNat 0)).NF)) ∧
      ∀ a < ω ^ a'.repr * ω * ↑m' + ω ^ a'.repr * ω + ω ^ a'.repr * ω,
        ∃ i, a < ω ^ a'.repr * ω * ↑m' + ω ^ a'.repr * ω + (ω ^ a'.repr * ↑i + ω ^ a'.repr)

pp: case oadd.inl.none.inr.zero
a : ONote
m : ℕ+
b : ONote
ihb : b = 0
e✝ : b.fundamentalSequence = Sum.inl none
f : ℕ → ONote
iha :
  IsSuccLimit a.repr ∧
    (∀ (i : ℕ), f i < f (i + 1) ∧ f i < a ∧ (a.NF → (f i).NF)) ∧ ∀ a_1 < a.repr, ∃ i, a_1 < (f i).repr
e : a.fundamentalSequence = Sum.inr f
e' : m.natPred = 0
⊢ IsSuccLimit (ω ^ a.repr) ∧
    (∀ (i : ℕ), (f i).repr < (f (i + 1)).repr ∧ (f i).repr < a.repr ∧ ((a.oadd 1 0).NF → ((f i).oadd 1 0).NF)) ∧
      ∀ a_1 < ω ^ a.repr, ∃ i, a_1 < ω ^ (f i).repr

pp: case oadd.inl.none.inr.succ
a : ONote
m : ℕ+
b : ONote
ihb : b = 0
e✝ : b.fundamentalSequence = Sum.inl none
f : ℕ → ONote
iha :
  IsSuccLimit a.repr ∧
    (∀ (i : ℕ), f i < f (i + 1) ∧ f i < a ∧ (a.NF → (f i).NF)) ∧ ∀ a_1 < a.repr, ∃ i, a_1 < (f i).repr
e : a.fundamentalSequence = Sum.inr f
m' : ℕ
e' : m.natPred = m' + 1
⊢ IsSuccLimit (ω ^ a.repr * ↑m' + ω ^ a.repr + ω ^ a.repr) ∧
    (∀ (i : ℕ),
        (f i).repr < (f (i + 1)).repr ∧
          (f i).repr < a.repr ∧ ((a.oadd (m' + 1).succPNat 0).NF → (a.oadd m'.succPNat ((f i).oadd 1 0)).NF)) ∧
      ∀ a_1 < ω ^ a.repr * ↑m' + ω ^ a.repr + ω ^ a.repr, ∃ i, a_1 < ω ^ a.repr * ↑m' + ω ^ a.repr + ω ^ (f i).repr

Tactic:
· have := opow_pos (repr a') omega0_pos
      refine
        ⟨isSuccLimit_add _ (isSuccLimit_mul_right this isSuccLimit_omega0), fun i => ⟨this, ?_, ?_⟩,
          exists_lt_add exists_lt_mul_omega0'⟩
      · rw [← mul_add_one, ← Nat.cast_add_one]
        gcongr
        apply natCast_lt_omega0
      · refine fun H => H.fst.oadd _ (NF.below_of_lt' ?_ (@NF.oadd_zero _ _ (iha.2 H.fst)))
        rw [repr, repr_zero, add_zero, iha.1, opow_succ]
        gcongr
        apply natCast_lt_omega0

Goal state after:
case oadd.inl.none.inr.zero
a : ONote
m : ℕ+
b : ONote
ihb : b = 0
e✝ : b.fundamentalSequence = Sum.inl none
f : ℕ → ONote
iha :
  IsSuccLimit a.repr ∧
    (∀ (i : ℕ), f i < f (i + 1) ∧ f i < a ∧ (a.NF → (f i).NF)) ∧ ∀ a_1 < a.repr, ∃ i, a_1 < (f i).repr
e : a.fundamentalSequence = Sum.inr f
e' : m.natPred = 0
⊢ IsSuccLimit (ω ^ a.repr) ∧
    (∀ (i : ℕ), (f i).repr < (f (i + 1)).repr ∧ (f i).repr < a.repr ∧ ((a.oadd 1 0).NF → ((f i).oadd 1 0).NF)) ∧
      ∀ a_1 < ω ^ a.repr, ∃ i, a_1 < ω ^ (f i).repr

case oadd.inl.none.inr.succ
a : ONote
m : ℕ+
b : ONote
ihb : b = 0
e✝ : b.fundamentalSequence = Sum.inl none
f : ℕ → ONote
iha :
  IsSuccLimit a.repr ∧
    (∀ (i : ℕ), f i < f (i + 1) ∧ f i < a ∧ (a.NF → (f i).NF)) ∧ ∀ a_1 < a.repr, ∃ i, a_1 < (f i).repr
e : a.fundamentalSequence = Sum.inr f
m' : ℕ
e' : m.natPred = m' + 1
⊢ IsSuccLimit (ω ^ a.repr * ↑m' + ω ^ a.repr + ω ^ a.repr) ∧
    (∀ (i : ℕ),
        (f i).repr < (f (i + 1)).repr ∧
          (f i).repr < a.repr ∧ ((a.oadd (m' + 1).succPNat 0).NF → (a.oadd m'.succPNat ((f i).oadd 1 0)).NF)) ∧
      ∀ a_1 < ω ^ a.repr * ↑m' + ω ^ a.repr + ω ^ a.repr, ∃ i, a_1 < ω ^ a.repr * ↑m' + ω ^ a.repr + ω ^ (f i).repr