Theorem: TruncatedWittVector.eq_of_le_of_cast_pow_eq_zero
File: Mathlib/RingTheory/WittVector/Compare.lean

tactic: contrapose! hpi
state_before: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i ≤ n
hpi : ↑p ^ i = 0
⊢ i = n
state_after: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i ≤ n
hpi : i ≠ n
⊢ ↑p ^ i ≠ 0

tactic: replace hin := lt_of_le_of_ne hin hpi
state_before: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i ≤ n
hpi : i ≠ n
⊢ ↑p ^ i ≠ 0
state_after: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hpi : i ≠ n
hin : i < n
⊢ ↑p ^ i ≠ 0

tactic: clear hpi
state_before: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hpi : i ≠ n
hin : i < n
⊢ ↑p ^ i ≠ 0
state_after: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ↑p ^ i ≠ 0

tactic: have : (p : TruncatedWittVector p n R) ^ i = WittVector.truncate n ((p : 𝕎 R) ^ i) := by
  rw [RingHom.map_pow, map_natCast]
state_before: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ↑p ^ i ≠ 0
state_after: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
this : ↑p ^ i = (WittVector.truncate n) (↑p ^ i)
⊢ ↑p ^ i ≠ 0

tactic: rw [this, ne_eq, ext_iff, not_forall]
state_before: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
this : ↑p ^ i = (WittVector.truncate n) (↑p ^ i)
⊢ ↑p ^ i ≠ 0
state_after: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
this : ↑p ^ i = (WittVector.truncate n) (↑p ^ i)
⊢ ∃ x, ¬coeff x ((WittVector.truncate n) (↑p ^ i)) = coeff x 0

tactic: clear this
state_before: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
this : ↑p ^ i = (WittVector.truncate n) (↑p ^ i)
⊢ ∃ x, ¬coeff x ((WittVector.truncate n) (↑p ^ i)) = coeff x 0
state_after: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ∃ x, ¬coeff x ((WittVector.truncate n) (↑p ^ i)) = coeff x 0

tactic: use ⟨i, hin⟩
state_before: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ∃ x, ¬coeff x ((WittVector.truncate n) (↑p ^ i)) = coeff x 0
state_after: case h
p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ¬coeff ⟨i, hin⟩ ((WittVector.truncate n) (↑p ^ i)) = coeff ⟨i, hin⟩ 0

tactic: rw [WittVector.coeff_truncate, coeff_zero, Fin.val_mk, WittVector.coeff_p_pow]
state_before: case h
p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ¬coeff ⟨i, hin⟩ ((WittVector.truncate n) (↑p ^ i)) = coeff ⟨i, hin⟩ 0
state_after: case h
p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ¬1 = 0

tactic: haveI : Nontrivial R := CharP.nontrivial_of_char_ne_one hp.1.ne_one
state_before: case h
p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ¬1 = 0
state_after: case h
p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
this : Nontrivial R
⊢ ¬1 = 0

tactic: exact one_ne_zero
state_before: case h
p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
this : Nontrivial R
⊢ ¬1 = 0
state_after: no goals

tactic: rw [RingHom.map_pow, map_natCast]
state_before: p : ℕ
hp : Fact (Nat.Prime p)
n : ℕ
R : Type u_1
inst✝¹ : CommRing R
inst✝ : CharP R p
i : ℕ
hin : i < n
⊢ ↑p ^ i = (WittVector.truncate n) (↑p ^ i)
state_after: no goals