c0dfe2e439
This introduces lemma support for BitVec.ofInt/BitVec.toInt as well as lemmas upstreamed from Std and Mathlib for reasoning about emod and bmod.
500 lines
20 KiB
Text
500 lines
20 KiB
Text
/-
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Copyright (c) 2016 Jeremy Avigad. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Jeremy Avigad, Deniz Aydin, Floris van Doorn, Mario Carneiro
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-/
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prelude
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import Init.Data.Int.Lemmas
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import Init.ByCases
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/-!
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# Results about the order properties of the integers, and the integers as an ordered ring.
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-/
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open Nat
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namespace Int
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/-! ## Order properties of the integers -/
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theorem nonneg_def {a : Int} : NonNeg a ↔ ∃ n : Nat, a = n :=
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⟨fun ⟨n⟩ => ⟨n, rfl⟩, fun h => match a, h with | _, ⟨n, rfl⟩ => ⟨n⟩⟩
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theorem NonNeg.elim {a : Int} : NonNeg a → ∃ n : Nat, a = n := nonneg_def.1
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theorem nonneg_or_nonneg_neg : ∀ (a : Int), NonNeg a ∨ NonNeg (-a)
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| (_:Nat) => .inl ⟨_⟩
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| -[_+1] => .inr ⟨_⟩
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theorem le_def (a b : Int) : a ≤ b ↔ NonNeg (b - a) := .rfl
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theorem lt_iff_add_one_le (a b : Int) : a < b ↔ a + 1 ≤ b := .rfl
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theorem le.intro_sub {a b : Int} (n : Nat) (h : b - a = n) : a ≤ b := by
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simp [le_def, h]; constructor
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attribute [local simp] Int.add_left_neg Int.add_right_neg Int.neg_add
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theorem le.intro {a b : Int} (n : Nat) (h : a + n = b) : a ≤ b :=
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le.intro_sub n <| by rw [← h, Int.add_comm]; simp [Int.sub_eq_add_neg, Int.add_assoc]
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theorem le.dest_sub {a b : Int} (h : a ≤ b) : ∃ n : Nat, b - a = n := nonneg_def.1 h
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theorem le.dest {a b : Int} (h : a ≤ b) : ∃ n : Nat, a + n = b :=
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let ⟨n, h₁⟩ := le.dest_sub h
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⟨n, by rw [← h₁, Int.add_comm]; simp [Int.sub_eq_add_neg, Int.add_assoc]⟩
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protected theorem le_total (a b : Int) : a ≤ b ∨ b ≤ a :=
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(nonneg_or_nonneg_neg (b - a)).imp_right fun H => by
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rwa [show -(b - a) = a - b by simp [Int.add_comm, Int.sub_eq_add_neg]] at H
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@[simp, norm_cast] theorem ofNat_le {m n : Nat} : (↑m : Int) ≤ ↑n ↔ m ≤ n :=
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⟨fun h =>
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let ⟨k, hk⟩ := le.dest h
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Nat.le.intro <| Int.ofNat.inj <| (Int.ofNat_add m k).trans hk,
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fun h =>
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let ⟨k, (hk : m + k = n)⟩ := Nat.le.dest h
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le.intro k (by rw [← hk]; rfl)⟩
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theorem ofNat_zero_le (n : Nat) : 0 ≤ (↑n : Int) := ofNat_le.2 n.zero_le
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theorem eq_ofNat_of_zero_le {a : Int} (h : 0 ≤ a) : ∃ n : Nat, a = n := by
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have t := le.dest_sub h; rwa [Int.sub_zero] at t
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theorem eq_succ_of_zero_lt {a : Int} (h : 0 < a) : ∃ n : Nat, a = n.succ :=
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let ⟨n, (h : ↑(1 + n) = a)⟩ := le.dest h
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⟨n, by rw [Nat.add_comm] at h; exact h.symm⟩
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theorem lt_add_succ (a : Int) (n : Nat) : a < a + Nat.succ n :=
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le.intro n <| by rw [Int.add_comm, Int.add_left_comm]; rfl
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theorem lt.intro {a b : Int} {n : Nat} (h : a + Nat.succ n = b) : a < b :=
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h ▸ lt_add_succ a n
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theorem lt.dest {a b : Int} (h : a < b) : ∃ n : Nat, a + Nat.succ n = b :=
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let ⟨n, h⟩ := le.dest h; ⟨n, by rwa [Int.add_comm, Int.add_left_comm] at h⟩
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@[simp, norm_cast] theorem ofNat_lt {n m : Nat} : (↑n : Int) < ↑m ↔ n < m := by
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rw [lt_iff_add_one_le, ← ofNat_succ, ofNat_le]; rfl
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@[simp, norm_cast] theorem ofNat_pos {n : Nat} : 0 < (↑n : Int) ↔ 0 < n := ofNat_lt
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theorem ofNat_nonneg (n : Nat) : 0 ≤ (n : Int) := ⟨_⟩
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theorem ofNat_succ_pos (n : Nat) : 0 < (succ n : Int) := ofNat_lt.2 <| Nat.succ_pos _
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@[simp] protected theorem le_refl (a : Int) : a ≤ a :=
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le.intro _ (Int.add_zero a)
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protected theorem le_trans {a b c : Int} (h₁ : a ≤ b) (h₂ : b ≤ c) : a ≤ c :=
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let ⟨n, hn⟩ := le.dest h₁; let ⟨m, hm⟩ := le.dest h₂
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le.intro (n + m) <| by rw [← hm, ← hn, Int.add_assoc, ofNat_add]
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protected theorem le_antisymm {a b : Int} (h₁ : a ≤ b) (h₂ : b ≤ a) : a = b := by
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let ⟨n, hn⟩ := le.dest h₁; let ⟨m, hm⟩ := le.dest h₂
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have := hn; rw [← hm, Int.add_assoc, ← ofNat_add] at this
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have := Int.ofNat.inj <| Int.add_left_cancel <| this.trans (Int.add_zero _).symm
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rw [← hn, Nat.eq_zero_of_add_eq_zero_left this, ofNat_zero, Int.add_zero a]
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protected theorem lt_irrefl (a : Int) : ¬a < a := fun H =>
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let ⟨n, hn⟩ := lt.dest H
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have : (a+Nat.succ n) = a+0 := by
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rw [hn, Int.add_zero]
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have : Nat.succ n = 0 := Int.ofNat.inj (Int.add_left_cancel this)
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show False from Nat.succ_ne_zero _ this
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protected theorem ne_of_lt {a b : Int} (h : a < b) : a ≠ b := fun e => by
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cases e; exact Int.lt_irrefl _ h
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protected theorem ne_of_gt {a b : Int} (h : b < a) : a ≠ b := (Int.ne_of_lt h).symm
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protected theorem le_of_lt {a b : Int} (h : a < b) : a ≤ b :=
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let ⟨_, hn⟩ := lt.dest h; le.intro _ hn
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protected theorem lt_iff_le_and_ne {a b : Int} : a < b ↔ a ≤ b ∧ a ≠ b := by
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refine ⟨fun h => ⟨Int.le_of_lt h, Int.ne_of_lt h⟩, fun ⟨aleb, aneb⟩ => ?_⟩
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let ⟨n, hn⟩ := le.dest aleb
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have : n ≠ 0 := aneb.imp fun eq => by rw [← hn, eq, ofNat_zero, Int.add_zero]
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apply lt.intro; rwa [← Nat.succ_pred_eq_of_pos (Nat.pos_of_ne_zero this)] at hn
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theorem lt_succ (a : Int) : a < a + 1 := Int.le_refl _
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protected theorem zero_lt_one : (0 : Int) < 1 := ⟨_⟩
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protected theorem lt_iff_le_not_le {a b : Int} : a < b ↔ a ≤ b ∧ ¬b ≤ a := by
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rw [Int.lt_iff_le_and_ne]
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constructor <;> refine fun ⟨h, h'⟩ => ⟨h, h'.imp fun h' => ?_⟩
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· exact Int.le_antisymm h h'
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· subst h'; apply Int.le_refl
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protected theorem not_le {a b : Int} : ¬a ≤ b ↔ b < a :=
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⟨fun h => Int.lt_iff_le_not_le.2 ⟨(Int.le_total ..).resolve_right h, h⟩,
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fun h => (Int.lt_iff_le_not_le.1 h).2⟩
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protected theorem not_lt {a b : Int} : ¬a < b ↔ b ≤ a :=
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by rw [← Int.not_le, Decidable.not_not]
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protected theorem lt_trichotomy (a b : Int) : a < b ∨ a = b ∨ b < a :=
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if eq : a = b then .inr <| .inl eq else
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if le : a ≤ b then .inl <| Int.lt_iff_le_and_ne.2 ⟨le, eq⟩ else
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.inr <| .inr <| Int.not_le.1 le
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protected theorem ne_iff_lt_or_gt {a b : Int} : a ≠ b ↔ a < b ∨ b < a := by
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constructor
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· intro h
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cases Int.lt_trichotomy a b
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case inl lt => exact Or.inl lt
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case inr h =>
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cases h
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case inl =>simp_all
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case inr gt => exact Or.inr gt
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· intro h
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cases h
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case inl lt => exact Int.ne_of_lt lt
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case inr gt => exact Int.ne_of_gt gt
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protected theorem lt_or_gt_of_ne {a b : Int} : a ≠ b → a < b ∨ b < a:= Int.ne_iff_lt_or_gt.mp
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protected theorem eq_iff_le_and_ge {x y : Int} : x = y ↔ x ≤ y ∧ y ≤ x := by
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constructor
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· simp_all
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· intro ⟨h₁, h₂⟩
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exact Int.le_antisymm h₁ h₂
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protected theorem lt_of_le_of_lt {a b c : Int} (h₁ : a ≤ b) (h₂ : b < c) : a < c :=
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Int.not_le.1 fun h => Int.not_le.2 h₂ (Int.le_trans h h₁)
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protected theorem lt_of_lt_of_le {a b c : Int} (h₁ : a < b) (h₂ : b ≤ c) : a < c :=
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Int.not_le.1 fun h => Int.not_le.2 h₁ (Int.le_trans h₂ h)
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protected theorem lt_trans {a b c : Int} (h₁ : a < b) (h₂ : b < c) : a < c :=
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Int.lt_of_le_of_lt (Int.le_of_lt h₁) h₂
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instance : Trans (α := Int) (· ≤ ·) (· ≤ ·) (· ≤ ·) := ⟨Int.le_trans⟩
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instance : Trans (α := Int) (· < ·) (· ≤ ·) (· < ·) := ⟨Int.lt_of_lt_of_le⟩
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instance : Trans (α := Int) (· ≤ ·) (· < ·) (· < ·) := ⟨Int.lt_of_le_of_lt⟩
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instance : Trans (α := Int) (· < ·) (· < ·) (· < ·) := ⟨Int.lt_trans⟩
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protected theorem min_def (n m : Int) : min n m = if n ≤ m then n else m := rfl
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protected theorem max_def (n m : Int) : max n m = if n ≤ m then m else n := rfl
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protected theorem min_comm (a b : Int) : min a b = min b a := by
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simp [Int.min_def]
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by_cases h₁ : a ≤ b <;> by_cases h₂ : b ≤ a <;> simp [h₁, h₂]
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· exact Int.le_antisymm h₁ h₂
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· cases not_or_intro h₁ h₂ <| Int.le_total ..
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protected theorem min_le_right (a b : Int) : min a b ≤ b := by rw [Int.min_def]; split <;> simp [*]
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protected theorem min_le_left (a b : Int) : min a b ≤ a := Int.min_comm .. ▸ Int.min_le_right ..
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protected theorem min_eq_left {a b : Int} (h : a ≤ b) : min a b = a := by simp [Int.min_def, h]
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protected theorem min_eq_right {a b : Int} (h : b ≤ a) : min a b = b := by
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rw [Int.min_comm a b]; exact Int.min_eq_left h
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protected theorem le_min {a b c : Int} : a ≤ min b c ↔ a ≤ b ∧ a ≤ c :=
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⟨fun h => ⟨Int.le_trans h (Int.min_le_left ..), Int.le_trans h (Int.min_le_right ..)⟩,
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fun ⟨h₁, h₂⟩ => by rw [Int.min_def]; split <;> assumption⟩
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protected theorem max_comm (a b : Int) : max a b = max b a := by
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simp only [Int.max_def]
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by_cases h₁ : a ≤ b <;> by_cases h₂ : b ≤ a <;> simp [h₁, h₂]
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· exact Int.le_antisymm h₂ h₁
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· cases not_or_intro h₁ h₂ <| Int.le_total ..
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protected theorem le_max_left (a b : Int) : a ≤ max a b := by rw [Int.max_def]; split <;> simp [*]
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protected theorem le_max_right (a b : Int) : b ≤ max a b := Int.max_comm .. ▸ Int.le_max_left ..
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protected theorem max_le {a b c : Int} : max a b ≤ c ↔ a ≤ c ∧ b ≤ c :=
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⟨fun h => ⟨Int.le_trans (Int.le_max_left ..) h, Int.le_trans (Int.le_max_right ..) h⟩,
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fun ⟨h₁, h₂⟩ => by rw [Int.max_def]; split <;> assumption⟩
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protected theorem max_eq_right {a b : Int} (h : a ≤ b) : max a b = b := by
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simp [Int.max_def, h, Int.not_lt.2 h]
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protected theorem max_eq_left {a b : Int} (h : b ≤ a) : max a b = a := by
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rw [← Int.max_comm b a]; exact Int.max_eq_right h
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theorem eq_natAbs_of_zero_le {a : Int} (h : 0 ≤ a) : a = natAbs a := by
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let ⟨n, e⟩ := eq_ofNat_of_zero_le h
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rw [e]; rfl
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theorem le_natAbs {a : Int} : a ≤ natAbs a :=
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match Int.le_total 0 a with
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| .inl h => by rw [eq_natAbs_of_zero_le h]; apply Int.le_refl
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| .inr h => Int.le_trans h (ofNat_zero_le _)
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theorem negSucc_lt_zero (n : Nat) : -[n+1] < 0 :=
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Int.not_le.1 fun h => let ⟨_, h⟩ := eq_ofNat_of_zero_le h; nomatch h
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@[simp] theorem negSucc_not_nonneg (n : Nat) : 0 ≤ -[n+1] ↔ False := by
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simp only [Int.not_le, iff_false]; exact Int.negSucc_lt_zero n
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protected theorem add_le_add_left {a b : Int} (h : a ≤ b) (c : Int) : c + a ≤ c + b :=
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let ⟨n, hn⟩ := le.dest h; le.intro n <| by rw [Int.add_assoc, hn]
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protected theorem add_lt_add_left {a b : Int} (h : a < b) (c : Int) : c + a < c + b :=
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Int.lt_iff_le_and_ne.2 ⟨Int.add_le_add_left (Int.le_of_lt h) _, fun heq =>
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b.lt_irrefl <| by rwa [Int.add_left_cancel heq] at h⟩
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protected theorem add_le_add_right {a b : Int} (h : a ≤ b) (c : Int) : a + c ≤ b + c :=
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Int.add_comm c a ▸ Int.add_comm c b ▸ Int.add_le_add_left h c
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protected theorem add_lt_add_right {a b : Int} (h : a < b) (c : Int) : a + c < b + c :=
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Int.add_comm c a ▸ Int.add_comm c b ▸ Int.add_lt_add_left h c
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protected theorem le_of_add_le_add_left {a b c : Int} (h : a + b ≤ a + c) : b ≤ c := by
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have : -a + (a + b) ≤ -a + (a + c) := Int.add_le_add_left h _
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simp [Int.neg_add_cancel_left] at this
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assumption
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protected theorem le_of_add_le_add_right {a b c : Int} (h : a + b ≤ c + b) : a ≤ c :=
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Int.le_of_add_le_add_left (a := b) <| by rwa [Int.add_comm b a, Int.add_comm b c]
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protected theorem add_le_add_iff_left (a : Int) : a + b ≤ a + c ↔ b ≤ c :=
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⟨Int.le_of_add_le_add_left, (Int.add_le_add_left · _)⟩
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protected theorem add_le_add_iff_right (c : Int) : a + c ≤ b + c ↔ a ≤ b :=
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⟨Int.le_of_add_le_add_right, (Int.add_le_add_right · _)⟩
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protected theorem add_le_add {a b c d : Int} (h₁ : a ≤ b) (h₂ : c ≤ d) : a + c ≤ b + d :=
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Int.le_trans (Int.add_le_add_right h₁ c) (Int.add_le_add_left h₂ b)
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protected theorem le_add_of_nonneg_right {a b : Int} (h : 0 ≤ b) : a ≤ a + b := by
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have : a + b ≥ a + 0 := Int.add_le_add_left h a
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rwa [Int.add_zero] at this
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protected theorem le_add_of_nonneg_left {a b : Int} (h : 0 ≤ b) : a ≤ b + a := by
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have : 0 + a ≤ b + a := Int.add_le_add_right h a
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rwa [Int.zero_add] at this
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protected theorem neg_le_neg {a b : Int} (h : a ≤ b) : -b ≤ -a := by
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have : 0 ≤ -a + b := Int.add_left_neg a ▸ Int.add_le_add_left h (-a)
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have : 0 + -b ≤ -a + b + -b := Int.add_le_add_right this (-b)
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rwa [Int.add_neg_cancel_right, Int.zero_add] at this
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protected theorem le_of_neg_le_neg {a b : Int} (h : -b ≤ -a) : a ≤ b :=
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suffices - -a ≤ - -b by simp [Int.neg_neg] at this; assumption
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Int.neg_le_neg h
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protected theorem neg_nonpos_of_nonneg {a : Int} (h : 0 ≤ a) : -a ≤ 0 := by
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have : -a ≤ -0 := Int.neg_le_neg h
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rwa [Int.neg_zero] at this
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protected theorem neg_nonneg_of_nonpos {a : Int} (h : a ≤ 0) : 0 ≤ -a := by
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have : -0 ≤ -a := Int.neg_le_neg h
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rwa [Int.neg_zero] at this
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protected theorem neg_lt_neg {a b : Int} (h : a < b) : -b < -a := by
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have : 0 < -a + b := Int.add_left_neg a ▸ Int.add_lt_add_left h (-a)
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have : 0 + -b < -a + b + -b := Int.add_lt_add_right this (-b)
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rwa [Int.add_neg_cancel_right, Int.zero_add] at this
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protected theorem neg_neg_of_pos {a : Int} (h : 0 < a) : -a < 0 := by
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have : -a < -0 := Int.neg_lt_neg h
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rwa [Int.neg_zero] at this
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protected theorem neg_pos_of_neg {a : Int} (h : a < 0) : 0 < -a := by
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have : -0 < -a := Int.neg_lt_neg h
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rwa [Int.neg_zero] at this
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protected theorem sub_nonneg_of_le {a b : Int} (h : b ≤ a) : 0 ≤ a - b := by
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have h := Int.add_le_add_right h (-b)
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rwa [Int.add_right_neg] at h
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protected theorem le_of_sub_nonneg {a b : Int} (h : 0 ≤ a - b) : b ≤ a := by
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have h := Int.add_le_add_right h b
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rwa [Int.sub_add_cancel, Int.zero_add] at h
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protected theorem sub_pos_of_lt {a b : Int} (h : b < a) : 0 < a - b := by
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have h := Int.add_lt_add_right h (-b)
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rwa [Int.add_right_neg] at h
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protected theorem lt_of_sub_pos {a b : Int} (h : 0 < a - b) : b < a := by
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have h := Int.add_lt_add_right h b
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rwa [Int.sub_add_cancel, Int.zero_add] at h
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protected theorem sub_left_le_of_le_add {a b c : Int} (h : a ≤ b + c) : a - b ≤ c := by
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have h := Int.add_le_add_right h (-b)
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rwa [Int.add_comm b c, Int.add_neg_cancel_right] at h
|
||
|
||
protected theorem sub_le_self (a : Int) {b : Int} (h : 0 ≤ b) : a - b ≤ a :=
|
||
calc a + -b
|
||
_ ≤ a + 0 := Int.add_le_add_left (Int.neg_nonpos_of_nonneg h) _
|
||
_ = a := by rw [Int.add_zero]
|
||
|
||
protected theorem sub_lt_self (a : Int) {b : Int} (h : 0 < b) : a - b < a :=
|
||
calc a + -b
|
||
_ < a + 0 := Int.add_lt_add_left (Int.neg_neg_of_pos h) _
|
||
_ = a := by rw [Int.add_zero]
|
||
|
||
theorem add_one_le_of_lt {a b : Int} (H : a < b) : a + 1 ≤ b := H
|
||
|
||
/- ### Order properties and multiplication -/
|
||
|
||
|
||
protected theorem mul_nonneg {a b : Int} (ha : 0 ≤ a) (hb : 0 ≤ b) : 0 ≤ a * b := by
|
||
let ⟨n, hn⟩ := eq_ofNat_of_zero_le ha
|
||
let ⟨m, hm⟩ := eq_ofNat_of_zero_le hb
|
||
rw [hn, hm, ← ofNat_mul]; apply ofNat_nonneg
|
||
|
||
protected theorem mul_pos {a b : Int} (ha : 0 < a) (hb : 0 < b) : 0 < a * b := by
|
||
let ⟨n, hn⟩ := eq_succ_of_zero_lt ha
|
||
let ⟨m, hm⟩ := eq_succ_of_zero_lt hb
|
||
rw [hn, hm, ← ofNat_mul]; apply ofNat_succ_pos
|
||
|
||
protected theorem mul_lt_mul_of_pos_left {a b c : Int}
|
||
(h₁ : a < b) (h₂ : 0 < c) : c * a < c * b := by
|
||
have : 0 < c * (b - a) := Int.mul_pos h₂ (Int.sub_pos_of_lt h₁)
|
||
rw [Int.mul_sub] at this
|
||
exact Int.lt_of_sub_pos this
|
||
|
||
protected theorem mul_lt_mul_of_pos_right {a b c : Int}
|
||
(h₁ : a < b) (h₂ : 0 < c) : a * c < b * c := by
|
||
have : 0 < b - a := Int.sub_pos_of_lt h₁
|
||
have : 0 < (b - a) * c := Int.mul_pos this h₂
|
||
rw [Int.sub_mul] at this
|
||
exact Int.lt_of_sub_pos this
|
||
|
||
protected theorem mul_le_mul_of_nonneg_left {a b c : Int}
|
||
(h₁ : a ≤ b) (h₂ : 0 ≤ c) : c * a ≤ c * b :=
|
||
if hba : b ≤ a then by
|
||
rw [Int.le_antisymm hba h₁]; apply Int.le_refl
|
||
else if hc0 : c ≤ 0 then by
|
||
simp [Int.le_antisymm hc0 h₂, Int.zero_mul]
|
||
else by
|
||
exact Int.le_of_lt <| Int.mul_lt_mul_of_pos_left
|
||
(Int.lt_iff_le_not_le.2 ⟨h₁, hba⟩) (Int.lt_iff_le_not_le.2 ⟨h₂, hc0⟩)
|
||
|
||
protected theorem mul_le_mul_of_nonneg_right {a b c : Int}
|
||
(h₁ : a ≤ b) (h₂ : 0 ≤ c) : a * c ≤ b * c := by
|
||
rw [Int.mul_comm, Int.mul_comm b]; exact Int.mul_le_mul_of_nonneg_left h₁ h₂
|
||
|
||
protected theorem mul_le_mul {a b c d : Int}
|
||
(hac : a ≤ c) (hbd : b ≤ d) (nn_b : 0 ≤ b) (nn_c : 0 ≤ c) : a * b ≤ c * d :=
|
||
Int.le_trans (Int.mul_le_mul_of_nonneg_right hac nn_b) (Int.mul_le_mul_of_nonneg_left hbd nn_c)
|
||
|
||
protected theorem mul_nonpos_of_nonneg_of_nonpos {a b : Int}
|
||
(ha : 0 ≤ a) (hb : b ≤ 0) : a * b ≤ 0 := by
|
||
have h : a * b ≤ a * 0 := Int.mul_le_mul_of_nonneg_left hb ha
|
||
rwa [Int.mul_zero] at h
|
||
|
||
protected theorem mul_nonpos_of_nonpos_of_nonneg {a b : Int}
|
||
(ha : a ≤ 0) (hb : 0 ≤ b) : a * b ≤ 0 := by
|
||
have h : a * b ≤ 0 * b := Int.mul_le_mul_of_nonneg_right ha hb
|
||
rwa [Int.zero_mul] at h
|
||
|
||
protected theorem mul_le_mul_of_nonpos_right {a b c : Int}
|
||
(h : b ≤ a) (hc : c ≤ 0) : a * c ≤ b * c :=
|
||
have : -c ≥ 0 := Int.neg_nonneg_of_nonpos hc
|
||
have : b * -c ≤ a * -c := Int.mul_le_mul_of_nonneg_right h this
|
||
Int.le_of_neg_le_neg <| by rwa [← Int.neg_mul_eq_mul_neg, ← Int.neg_mul_eq_mul_neg] at this
|
||
|
||
protected theorem mul_le_mul_of_nonpos_left {a b c : Int}
|
||
(ha : a ≤ 0) (h : c ≤ b) : a * b ≤ a * c := by
|
||
rw [Int.mul_comm a b, Int.mul_comm a c]
|
||
apply Int.mul_le_mul_of_nonpos_right h ha
|
||
|
||
/- ## natAbs -/
|
||
|
||
@[simp] theorem natAbs_ofNat (n : Nat) : natAbs ↑n = n := rfl
|
||
@[simp] theorem natAbs_negSucc (n : Nat) : natAbs -[n+1] = n.succ := rfl
|
||
@[simp] theorem natAbs_zero : natAbs (0 : Int) = (0 : Nat) := rfl
|
||
@[simp] theorem natAbs_one : natAbs (1 : Int) = (1 : Nat) := rfl
|
||
|
||
@[simp] theorem natAbs_eq_zero : natAbs a = 0 ↔ a = 0 :=
|
||
⟨fun H => match a with
|
||
| ofNat _ => congrArg ofNat H
|
||
| -[_+1] => absurd H (succ_ne_zero _),
|
||
fun e => e ▸ rfl⟩
|
||
|
||
theorem natAbs_pos : 0 < natAbs a ↔ a ≠ 0 := by rw [Nat.pos_iff_ne_zero, Ne, natAbs_eq_zero]
|
||
|
||
@[simp] theorem natAbs_neg : ∀ (a : Int), natAbs (-a) = natAbs a
|
||
| 0 => rfl
|
||
| succ _ => rfl
|
||
| -[_+1] => rfl
|
||
|
||
theorem natAbs_eq : ∀ (a : Int), a = natAbs a ∨ a = -↑(natAbs a)
|
||
| ofNat _ => Or.inl rfl
|
||
| -[_+1] => Or.inr rfl
|
||
|
||
theorem natAbs_negOfNat (n : Nat) : natAbs (negOfNat n) = n := by
|
||
cases n <;> rfl
|
||
|
||
theorem natAbs_mul (a b : Int) : natAbs (a * b) = natAbs a * natAbs b := by
|
||
cases a <;> cases b <;>
|
||
simp only [← Int.mul_def, Int.mul, natAbs_negOfNat] <;> simp only [natAbs]
|
||
|
||
theorem natAbs_eq_natAbs_iff {a b : Int} : a.natAbs = b.natAbs ↔ a = b ∨ a = -b := by
|
||
constructor <;> intro h
|
||
· cases Int.natAbs_eq a with
|
||
| inl h₁ | inr h₁ =>
|
||
cases Int.natAbs_eq b with
|
||
| inl h₂ | inr h₂ => rw [h₁, h₂]; simp [h]
|
||
· cases h with (subst a; try rfl)
|
||
| inr h => rw [Int.natAbs_neg]
|
||
|
||
theorem natAbs_of_nonneg {a : Int} (H : 0 ≤ a) : (natAbs a : Int) = a :=
|
||
match a, eq_ofNat_of_zero_le H with
|
||
| _, ⟨_, rfl⟩ => rfl
|
||
|
||
theorem ofNat_natAbs_of_nonpos {a : Int} (H : a ≤ 0) : (natAbs a : Int) = -a := by
|
||
rw [← natAbs_neg, natAbs_of_nonneg (Int.neg_nonneg_of_nonpos H)]
|
||
|
||
/-! ### toNat -/
|
||
|
||
theorem toNat_eq_max : ∀ a : Int, (toNat a : Int) = max a 0
|
||
| (n : Nat) => (Int.max_eq_left (ofNat_zero_le n)).symm
|
||
| -[n+1] => (Int.max_eq_right (Int.le_of_lt (negSucc_lt_zero n))).symm
|
||
|
||
@[simp] theorem toNat_zero : (0 : Int).toNat = 0 := rfl
|
||
|
||
@[simp] theorem toNat_one : (1 : Int).toNat = 1 := rfl
|
||
|
||
@[simp] theorem toNat_of_nonneg {a : Int} (h : 0 ≤ a) : (toNat a : Int) = a := by
|
||
rw [toNat_eq_max, Int.max_eq_left h]
|
||
|
||
@[simp] theorem toNat_ofNat (n : Nat) : toNat ↑n = n := rfl
|
||
|
||
@[simp] theorem toNat_ofNat_add_one {n : Nat} : ((n : Int) + 1).toNat = n + 1 := rfl
|
||
|
||
theorem self_le_toNat (a : Int) : a ≤ toNat a := by rw [toNat_eq_max]; apply Int.le_max_left
|
||
|
||
@[simp] theorem le_toNat {n : Nat} {z : Int} (h : 0 ≤ z) : n ≤ z.toNat ↔ (n : Int) ≤ z := by
|
||
rw [← Int.ofNat_le, Int.toNat_of_nonneg h]
|
||
|
||
@[simp] theorem toNat_lt {n : Nat} {z : Int} (h : 0 ≤ z) : z.toNat < n ↔ z < (n : Int) := by
|
||
rw [← Int.not_le, ← Nat.not_le, Int.le_toNat h]
|
||
|
||
theorem toNat_add {a b : Int} (ha : 0 ≤ a) (hb : 0 ≤ b) : (a + b).toNat = a.toNat + b.toNat :=
|
||
match a, b, eq_ofNat_of_zero_le ha, eq_ofNat_of_zero_le hb with
|
||
| _, _, ⟨_, rfl⟩, ⟨_, rfl⟩ => rfl
|
||
|
||
theorem toNat_add_nat {a : Int} (ha : 0 ≤ a) (n : Nat) : (a + n).toNat = a.toNat + n :=
|
||
match a, eq_ofNat_of_zero_le ha with | _, ⟨_, rfl⟩ => rfl
|
||
|
||
@[simp] theorem pred_toNat : ∀ i : Int, (i - 1).toNat = i.toNat - 1
|
||
| 0 => rfl
|
||
| (n+1:Nat) => by simp [ofNat_add]
|
||
| -[n+1] => rfl
|
||
|
||
@[simp] theorem toNat_sub_toNat_neg : ∀ n : Int, ↑n.toNat - ↑(-n).toNat = n
|
||
| 0 => rfl
|
||
| (_+1:Nat) => Int.sub_zero _
|
||
| -[_+1] => Int.zero_sub _
|
||
|
||
@[simp] theorem toNat_add_toNat_neg_eq_natAbs : ∀ n : Int, n.toNat + (-n).toNat = n.natAbs
|
||
| 0 => rfl
|
||
| (_+1:Nat) => Nat.add_zero _
|
||
| -[_+1] => Nat.zero_add _
|
||
|
||
@[simp] theorem toNat_neg_nat : ∀ n : Nat, (-(n : Int)).toNat = 0
|
||
| 0 => rfl
|
||
| _+1 => rfl
|