Theorem: CompositionSeries.jordan_holder
File: Mathlib/Order/JordanHolder.lean

tactic: induction' hle : s₁.length with n ih generalizing s₁ s₂
state_before: X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
⊢ s₁.Equivalent s₂
state_after: case zero
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = 0
⊢ s₁.Equivalent s₂

case succ
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
⊢ s₁.Equivalent s₂

tactic: rw [eq_of_head_eq_head_of_last_eq_last_of_length_eq_zero hb ht hle]
state_before: case zero
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = 0
⊢ s₁.Equivalent s₂
state_after: no goals

tactic: have h0s₂ : 0 < s₂.length :=
  length_pos_of_head_eq_head_of_last_eq_last_of_length_pos hb ht (hle.symm ▸ Nat.succ_pos _)
state_before: case succ
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
⊢ s₁.Equivalent s₂
state_after: case succ
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
⊢ s₁.Equivalent s₂

tactic: rcases exists_last_eq_snoc_equivalent s₁ s₂.eraseLast.last
    (ht.symm ▸ isMaximal_eraseLast_last h0s₂)
    (hb.symm ▸ s₂.head_eraseLast ▸ head_le_of_mem (last_mem _)) with
  ⟨t, htb, htl, htt, hteq⟩
state_before: case succ
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
⊢ s₁.Equivalent s₂
state_after: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
⊢ s₁.Equivalent s₂

tactic: have := ih t s₂.eraseLast (by simp [htb, ← hb]) htt (Nat.succ_inj'.1 (htl.trans hle))
state_before: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
⊢ s₁.Equivalent s₂
state_after: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ s₁.Equivalent s₂

tactic: refine hteq.trans ?_
state_before: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ s₁.Equivalent s₂
state_after: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ Equivalent (snoc t (last s₁) ⋯) s₂

tactic: conv_rhs => rw [eq_snoc_eraseLast h0s₂]
state_before: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ Equivalent (snoc t (last s₁) ⋯) s₂
state_after: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ Equivalent (snoc t (last s₁) ⋯) ((eraseLast s₂).snoc (last s₂) ⋯)

tactic: simp only [ht]
state_before: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ Equivalent (snoc t (last s₁) ⋯) ((eraseLast s₂).snoc (last s₂) ⋯)
state_after: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ Equivalent (snoc t (last s₂) ⋯) ((eraseLast s₂).snoc (last s₂) ⋯)

tactic: exact Equivalent.snoc this (by simpa [htt] using (isMaximal_eraseLast_last h0s₂).iso_refl)
state_before: case succ.intro.intro.intro.intro
X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ Equivalent (snoc t (last s₂) ⋯) ((eraseLast s₂).snoc (last s₂) ⋯)
state_after: no goals

tactic: simp [htb, ← hb]
state_before: X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
⊢ head t = (eraseLast s₂).head
state_after: no goals

tactic: simpa [htt] using (isMaximal_eraseLast_last h0s₂).iso_refl
state_before: X : Type u
inst✝¹ : Lattice X
inst✝ : JordanHolderLattice X
n : ℕ
ih : ∀ (s₁ s₂ : CompositionSeries X), head s₁ = head s₂ → last s₁ = last s₂ → s₁.length = n → s₁.Equivalent s₂
s₁ s₂ : CompositionSeries X
hb : head s₁ = head s₂
ht : last s₁ = last s₂
hle : s₁.length = n + 1
h0s₂ : 0 < s₂.length
t : CompositionSeries X
htb : head t = head s₁
htl : t.length + 1 = s₁.length
htt : last t = (eraseLast s₂).last
hteq : s₁.Equivalent (snoc t (last s₁) ⋯)
this : t.Equivalent (eraseLast s₂)
⊢ Iso (last t, last s₂) ((eraseLast s₂).last, last s₂)
state_after: no goals