Theorem: Nat.sInf_add
File: Mathlib/Data/Nat/Lattice.lean

tactic: obtain h | ⟨m, hm⟩ := { m | p (m + n) }.eq_empty_or_nonempty
state_before: n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
⊢ sInf {m | p (m + n)} + n = sInf {m | p m}
state_after: case inl
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
⊢ sInf {m | p (m + n)} + n = sInf {m | p m}

case inr.intro
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
m : ℕ
hm : m ∈ {m | p (m + n)}
⊢ sInf {m | p (m + n)} + n = sInf {m | p m}

tactic: rw [h, Nat.sInf_empty, zero_add]
state_before: case inl
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
⊢ sInf {m | p (m + n)} + n = sInf {m | p m}
state_after: case inl
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
⊢ n = sInf {m | p m}

tactic: obtain hnp | hnp := hn.eq_or_lt
state_before: case inl
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
⊢ n = sInf {m | p m}
state_after: case inl.inl
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
hnp : n = sInf {m | p m}
⊢ n = sInf {m | p m}

case inl.inr
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
hnp : n < sInf {m | p m}
⊢ n = sInf {m | p m}

tactic: suffices hp : p (sInf { m | p m } - n + n) from (h.subset hp).elim
state_before: case inl.inr
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
hnp : n < sInf {m | p m}
⊢ n = sInf {m | p m}
state_after: case inl.inr
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
hnp : n < sInf {m | p m}
⊢ p (sInf {m | p m} - n + n)

tactic: rw [Nat.sub_add_cancel hn]
state_before: case inl.inr
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
hnp : n < sInf {m | p m}
⊢ p (sInf {m | p m} - n + n)
state_after: case inl.inr
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
hnp : n < sInf {m | p m}
⊢ p (sInf {m | p m})

tactic: exact csInf_mem (nonempty_of_pos_sInf <| n.zero_le.trans_lt hnp)
state_before: case inl.inr
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
hnp : n < sInf {m | p m}
⊢ p (sInf {m | p m})
state_after: no goals

tactic: exact hnp
state_before: case inl.inl
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
h : {m | p (m + n)} = ∅
hnp : n = sInf {m | p m}
⊢ n = sInf {m | p m}
state_after: no goals

tactic: have hp : ∃ n, n ∈ { m | p m } := ⟨_, hm⟩
state_before: case inr.intro
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
m : ℕ
hm : m ∈ {m | p (m + n)}
⊢ sInf {m | p (m + n)} + n = sInf {m | p m}
state_after: case inr.intro
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
m : ℕ
hm : m ∈ {m | p (m + n)}
hp : ∃ n, n ∈ {m | p m}
⊢ sInf {m | p (m + n)} + n = sInf {m | p m}

tactic: rw [Nat.sInf_def ⟨m, hm⟩, Nat.sInf_def hp]
state_before: case inr.intro
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
m : ℕ
hm : m ∈ {m | p (m + n)}
hp : ∃ n, n ∈ {m | p m}
⊢ sInf {m | p (m + n)} + n = sInf {m | p m}
state_after: case inr.intro
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
m : ℕ
hm : m ∈ {m | p (m + n)}
hp : ∃ n, n ∈ {m | p m}
⊢ Nat.find ⋯ + n = Nat.find hp

tactic: rw [Nat.sInf_def hp] at hn
state_before: case inr.intro
n : ℕ
p : ℕ → Prop
hn : n ≤ sInf {m | p m}
m : ℕ
hm : m ∈ {m | p (m + n)}
hp : ∃ n, n ∈ {m | p m}
⊢ Nat.find ⋯ + n = Nat.find hp
state_after: case inr.intro
n : ℕ
p : ℕ → Prop
m : ℕ
hm : m ∈ {m | p (m + n)}
hp : ∃ n, n ∈ {m | p m}
hn : n ≤ Nat.find hp
⊢ Nat.find ⋯ + n = Nat.find hp

tactic: exact find_add hn
state_before: case inr.intro
n : ℕ
p : ℕ → Prop
m : ℕ
hm : m ∈ {m | p (m + n)}
hp : ∃ n, n ∈ {m | p m}
hn : n ≤ Nat.find hp
⊢ Nat.find ⋯ + n = Nat.find hp
state_after: no goals