Mathlib.Algebra.GroupWithZero.Defs

class MulZeroClass (M₀ : Type u) extends Mul M₀, Zero M₀ :

Typeclass for expressing that a type M₀ with multiplication and a zero satisfies 0 * a = 0 and a * 0 = 0 for all a : M₀.

mul : M₀ → M₀ → M₀
zero : M₀
zero_mul (a : M₀) : 0 * a = 0
Zero is a left absorbing element for multiplication
mul_zero (a : M₀) : a * 0 = 0
Zero is a right absorbing element for multiplication

Instances

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class IsLeftCancelMulZero (M₀ : Type u) [Mul M₀] [Zero M₀] :

Prop

A mixin for left cancellative multiplication by nonzero elements.

mul_left_cancel_of_ne_zero {a b c : M₀} : a ≠ 0 → a * b = a * c → b = c
Multiplication by a nonzero element is left cancellative.

Instances

Nat.instIsLeftCancelMulZero

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theorem mul_left_cancel₀ {M₀ : Type u_1} [Mul M₀] [Zero M₀] [IsLeftCancelMulZero M₀] {a b c : M₀} (ha : a ≠ 0) (h : a * b = a * c) :

b = c

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theorem mul_right_injective₀ {M₀ : Type u_1} [Mul M₀] [Zero M₀] [IsLeftCancelMulZero M₀] {a : M₀} (ha : a ≠ 0) :

Function.Injective fun (x : M₀) => a * x

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class IsRightCancelMulZero (M₀ : Type u) [Mul M₀] [Zero M₀] :

Prop

A mixin for right cancellative multiplication by nonzero elements.

mul_right_cancel_of_ne_zero {a b c : M₀} : b ≠ 0 → a * b = c * b → a = c
Multiplicatin by a nonzero element is right cancellative.

Instances

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theorem mul_right_cancel₀ {M₀ : Type u_1} [Mul M₀] [Zero M₀] [IsRightCancelMulZero M₀] {a b c : M₀} (hb : b ≠ 0) (h : a * b = c * b) :

a = c

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theorem mul_left_injective₀ {M₀ : Type u_1} [Mul M₀] [Zero M₀] [IsRightCancelMulZero M₀] {b : M₀} (hb : b ≠ 0) :

Function.Injective fun (a : M₀) => a * b

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class IsCancelMulZero (M₀ : Type u) [Mul M₀] [Zero M₀] extends IsLeftCancelMulZero M₀, IsRightCancelMulZero M₀ :

Prop

A mixin for cancellative multiplication by nonzero elements.

mul_left_cancel_of_ne_zero {a b c : M₀} : a ≠ 0 → a * b = a * c → b = c
mul_right_cancel_of_ne_zero {a b c : M₀} : b ≠ 0 → a * b = c * b → a = c

Instances

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class NoZeroDivisors (M₀ : Type u_2) [Mul M₀] [Zero M₀] :

Prop

Predicate typeclass for expressing that a * b = 0 implies a = 0 or b = 0 for all a and b of type G₀.

eq_zero_or_eq_zero_of_mul_eq_zero {a b : M₀} : a * b = 0 → a = 0 ∨ b = 0
For all a and b of G₀, a * b = 0 implies a = 0 or b = 0.

Instances

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class SemigroupWithZero (S₀ : Type u) extends Semigroup S₀, MulZeroClass S₀ :

Type u

A type S₀ is a "semigroup with zero” if it is a semigroup with zero element, and 0 is left and right absorbing.

mul : S₀ → S₀ → S₀
mul_assoc (a b c : S₀) : a * b * c = a * (b * c)
zero : S₀
zero_mul (a : S₀) : 0 * a = 0
mul_zero (a : S₀) : a * 0 = 0

Instances

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class MulZeroOneClass (M₀ : Type u) extends MulOneClass M₀, MulZeroClass M₀ :

Type u

A typeclass for non-associative monoids with zero elements.

one : M₀
mul : M₀ → M₀ → M₀
one_mul (a : M₀) : 1 * a = a
mul_one (a : M₀) : a * 1 = a
zero : M₀
zero_mul (a : M₀) : 0 * a = 0
mul_zero (a : M₀) : a * 0 = 0

Instances

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class MonoidWithZero (M₀ : Type u) extends Monoid M₀, MulZeroOneClass M₀, SemigroupWithZero M₀ :

Type u

A type M₀ is a “monoid with zero” if it is a monoid with zero element, and 0 is left and right absorbing.

mul : M₀ → M₀ → M₀
mul_assoc (a b c : M₀) : a * b * c = a * (b * c)
one : M₀
one_mul (a : M₀) : 1 * a = a
mul_one (a : M₀) : a * 1 = a
npow : ℕ → M₀ → M₀
npow_zero (x : M₀) : Monoid.npow 0 x = 1
npow_succ (n : ℕ) (x : M₀) : Monoid.npow (n + 1) x = Monoid.npow n x * x
zero : M₀
zero_mul (a : M₀) : 0 * a = 0
mul_zero (a : M₀) : a * 0 = 0

Instances

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theorem pow_mul_apply_eq_pow_mul {M₀ : Type u_1} [MonoidWithZero M₀] {M : Type u_2} [Monoid M] (f : M₀ → M) {x : M₀} (hx : ∀ (y : M₀), f (x * y) = f x * f y) (n : ℕ) (y : M₀) :

f (x ^ n * y) = f x ^ n * f y

If x is multiplicative with respect to f, then so is any x^n.

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class CancelMonoidWithZero (M₀ : Type u_2) extends MonoidWithZero M₀, IsCancelMulZero M₀ :

Type u_2

A type M is a CancelMonoidWithZero if it is a monoid with zero element, 0 is left and right absorbing, and left/right multiplication by a non-zero element is injective.

mul : M₀ → M₀ → M₀
mul_assoc (a b c : M₀) : a * b * c = a * (b * c)
one : M₀
one_mul (a : M₀) : 1 * a = a
mul_one (a : M₀) : a * 1 = a
npow : ℕ → M₀ → M₀
npow_zero (x : M₀) : Monoid.npow 0 x = 1
npow_succ (n : ℕ) (x : M₀) : Monoid.npow (n + 1) x = Monoid.npow n x * x
zero : M₀
zero_mul (a : M₀) : 0 * a = 0
mul_zero (a : M₀) : a * 0 = 0
mul_left_cancel_of_ne_zero {a b c : M₀} : a ≠ 0 → a * b = a * c → b = c
mul_right_cancel_of_ne_zero {a b c : M₀} : b ≠ 0 → a * b = c * b → a = c

Instances

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class CommMonoidWithZero (M₀ : Type u_2) extends CommMonoid M₀, MonoidWithZero M₀ :

Type u_2

A type M is a commutative “monoid with zero” if it is a commutative monoid with zero element, and 0 is left and right absorbing.

mul : M₀ → M₀ → M₀
mul_assoc (a b c : M₀) : a * b * c = a * (b * c)
one : M₀
one_mul (a : M₀) : 1 * a = a
mul_one (a : M₀) : a * 1 = a
npow : ℕ → M₀ → M₀
npow_zero (x : M₀) : Monoid.npow 0 x = 1
npow_succ (n : ℕ) (x : M₀) : Monoid.npow (n + 1) x = Monoid.npow n x * x
mul_comm (a b : M₀) : a * b = b * a
zero : M₀
zero_mul (a : M₀) : 0 * a = 0
mul_zero (a : M₀) : a * 0 = 0

Instances

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theorem mul_left_inj' {M₀ : Type u_1} [CancelMonoidWithZero M₀] {a b c : M₀} (hc : c ≠ 0) :

a * c = b * c ↔ a = b

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theorem mul_right_inj' {M₀ : Type u_1} [CancelMonoidWithZero M₀] {a b c : M₀} (ha : a ≠ 0) :

a * b = a * c ↔ b = c

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theorem IsLeftCancelMulZero.to_isRightCancelMulZero {M₀ : Type u_1} [CommSemigroup M₀] [Zero M₀] [IsLeftCancelMulZero M₀] :

IsRightCancelMulZero M₀

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theorem IsRightCancelMulZero.to_isLeftCancelMulZero {M₀ : Type u_1} [CommSemigroup M₀] [Zero M₀] [IsRightCancelMulZero M₀] :

IsLeftCancelMulZero M₀

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theorem IsLeftCancelMulZero.to_isCancelMulZero {M₀ : Type u_1} [CommSemigroup M₀] [Zero M₀] [IsLeftCancelMulZero M₀] :

IsCancelMulZero M₀

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theorem IsRightCancelMulZero.to_isCancelMulZero {M₀ : Type u_1} [CommSemigroup M₀] [Zero M₀] [IsRightCancelMulZero M₀] :

IsCancelMulZero M₀

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class CancelCommMonoidWithZero (M₀ : Type u_2) extends CommMonoidWithZero M₀, IsLeftCancelMulZero M₀ :

Type u_2

A type M is a CancelCommMonoidWithZero if it is a commutative monoid with zero element, 0 is left and right absorbing, and left/right multiplication by a non-zero element is injective.

mul : M₀ → M₀ → M₀
mul_assoc (a b c : M₀) : a * b * c = a * (b * c)
one : M₀
one_mul (a : M₀) : 1 * a = a
mul_one (a : M₀) : a * 1 = a
npow : ℕ → M₀ → M₀
npow_zero (x : M₀) : Monoid.npow 0 x = 1
npow_succ (n : ℕ) (x : M₀) : Monoid.npow (n + 1) x = Monoid.npow n x * x
mul_comm (a b : M₀) : a * b = b * a
zero : M₀
zero_mul (a : M₀) : 0 * a = 0
mul_zero (a : M₀) : a * 0 = 0
mul_left_cancel_of_ne_zero {a b c : M₀} : a ≠ 0 → a * b = a * c → b = c

Instances

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@[instance 100]

instance CancelCommMonoidWithZero.toCancelMonoidWithZero {M₀ : Type u_1} [CancelCommMonoidWithZero M₀] :

CancelMonoidWithZero M₀

Equations

CancelCommMonoidWithZero.toCancelMonoidWithZero = CancelMonoidWithZero.mk

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class MulDivCancelClass (M₀ : Type u_2) [MonoidWithZero M₀] [Div M₀] :

Prop

Prop-valued mixin for a monoid with zero to be equipped with a cancelling division.

The obvious use case is groups with zero, but this condition is also satisfied by ℕ, ℤ and, more generally, any euclidean domain.

mul_div_cancel (a b : M₀) : b ≠ 0 → a * b / b = a

Instances

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@[simp]

theorem mul_div_cancel_right₀ {M₀ : Type u_1} [MonoidWithZero M₀] [Div M₀] [MulDivCancelClass M₀] (a : M₀) {b : M₀} (hb : b ≠ 0) :

a * b / b = a

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@[simp]

theorem mul_div_cancel_left₀ {M₀ : Type u_1} [CommMonoidWithZero M₀] [Div M₀] [MulDivCancelClass M₀] (b : M₀) {a : M₀} (ha : a ≠ 0) :

a * b / a = b

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class GroupWithZero (G₀ : Type u) extends MonoidWithZero G₀, DivInvMonoid G₀, Nontrivial G₀ :

Type u

A type G₀ is a “group with zero” if it is a monoid with zero element (distinct from 1) such that every nonzero element is invertible. The type is required to come with an “inverse” function, and the inverse of 0 must be 0.

Examples include division rings and the ordered monoids that are the target of valuations in general valuation theory.

mul : G₀ → G₀ → G₀
mul_assoc (a b c : G₀) : a * b * c = a * (b * c)
one : G₀
one_mul (a : G₀) : 1 * a = a
mul_one (a : G₀) : a * 1 = a
npow : ℕ → G₀ → G₀
npow_zero (x : G₀) : Monoid.npow 0 x = 1
npow_succ (n : ℕ) (x : G₀) : Monoid.npow (n + 1) x = Monoid.npow n x * x
zero : G₀
zero_mul (a : G₀) : 0 * a = 0
mul_zero (a : G₀) : a * 0 = 0
inv : G₀ → G₀
div : G₀ → G₀ → G₀
div_eq_mul_inv (a b : G₀) : a / b = a * b⁻¹
zpow : ℤ → G₀ → G₀
zpow_zero' (a : G₀) : GroupWithZero.zpow 0 a = 1
zpow_succ' (n : ℕ) (a : G₀) : GroupWithZero.zpow (↑n.succ) a = GroupWithZero.zpow (↑n) a * a
zpow_neg' (n : ℕ) (a : G₀) : GroupWithZero.zpow (Int.negSucc n) a = (GroupWithZero.zpow (↑n.succ) a)⁻¹
exists_pair_ne : ∃ (x : G₀), ∃ (y : G₀), x ≠ y
inv_zero : 0⁻¹ = 0
The inverse of 0 in a group with zero is 0.
mul_inv_cancel (a : G₀) : a ≠ 0 → a * a⁻¹ = 1
Every nonzero element of a group with zero is invertible.

Instances

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@[simp]

theorem inv_zero {G₀ : Type u} [GroupWithZero G₀] :

0⁻¹ = 0

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@[simp]

theorem mul_inv_cancel₀ {G₀ : Type u} [GroupWithZero G₀] {a : G₀} (h : a ≠ 0) :

a * a⁻¹ = 1

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@[instance 100]

instance GroupWithZero.toMulDivCancelClass {G₀ : Type u} [GroupWithZero G₀] :

MulDivCancelClass G₀

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class CommGroupWithZero (G₀ : Type u_2) extends CommMonoidWithZero G₀, GroupWithZero G₀ :

Type u_2

A type G₀ is a commutative “group with zero” if it is a commutative monoid with zero element (distinct from 1) such that every nonzero element is invertible. The type is required to come with an “inverse” function, and the inverse of 0 must be 0.

mul : G₀ → G₀ → G₀
mul_assoc (a b c : G₀) : a * b * c = a * (b * c)
one : G₀
one_mul (a : G₀) : 1 * a = a
mul_one (a : G₀) : a * 1 = a
npow : ℕ → G₀ → G₀
npow_zero (x : G₀) : Monoid.npow 0 x = 1
npow_succ (n : ℕ) (x : G₀) : Monoid.npow (n + 1) x = Monoid.npow n x * x
mul_comm (a b : G₀) : a * b = b * a
zero : G₀
zero_mul (a : G₀) : 0 * a = 0
mul_zero (a : G₀) : a * 0 = 0
inv : G₀ → G₀
div : G₀ → G₀ → G₀
div_eq_mul_inv (a b : G₀) : a / b = a * b⁻¹
zpow : ℤ → G₀ → G₀
zpow_zero' (a : G₀) : CommGroupWithZero.zpow 0 a = 1
zpow_succ' (n : ℕ) (a : G₀) : CommGroupWithZero.zpow (↑n.succ) a = CommGroupWithZero.zpow (↑n) a * a
zpow_neg' (n : ℕ) (a : G₀) : CommGroupWithZero.zpow (Int.negSucc n) a = (CommGroupWithZero.zpow (↑n.succ) a)⁻¹
exists_pair_ne : ∃ (x : G₀), ∃ (y : G₀), x ≠ y
inv_zero : 0⁻¹ = 0
mul_inv_cancel (a : G₀) : a ≠ 0 → a * a⁻¹ = 1

Instances

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theorem eq_zero_or_one_of_sq_eq_self {M₀ : Type u_1} [CancelMonoidWithZero M₀] {x : M₀} (hx : x ^ 2 = x) :

x = 0 ∨ x = 1

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@[simp]

theorem mul_inv_cancel_right₀ {G₀ : Type u} [GroupWithZero G₀] {b : G₀} (h : b ≠ 0) (a : G₀) :

a * b * b⁻¹ = a

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@[simp]

theorem mul_inv_cancel_left₀ {G₀ : Type u} [GroupWithZero G₀] {a : G₀} (h : a ≠ 0) (b : G₀) :

a * (a⁻¹ * b) = b

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theorem mul_eq_zero_of_left {M₀ : Type u_1} [MulZeroClass M₀] {a : M₀} (h : a = 0) (b : M₀) :

a * b = 0

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theorem mul_eq_zero_of_right {M₀ : Type u_1} [MulZeroClass M₀] (a : M₀) {b : M₀} (h : b = 0) :

a * b = 0

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@[simp]

theorem mul_eq_zero {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} :

a * b = 0 ↔ a = 0 ∨ b = 0

If α has no zero divisors, then the product of two elements equals zero iff one of them equals zero.

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@[simp]

theorem zero_eq_mul {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} :

0 = a * b ↔ a = 0 ∨ b = 0

If α has no zero divisors, then the product of two elements equals zero iff one of them equals zero.

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theorem mul_ne_zero_iff {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} :

a * b ≠ 0 ↔ a ≠ 0 ∧ b ≠ 0

If α has no zero divisors, then the product of two elements is nonzero iff both of them are nonzero.

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theorem mul_eq_zero_comm {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} :

a * b = 0 ↔ b * a = 0

If α has no zero divisors, then for elements a, b : α, a * b equals zero iff so is b * a.

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theorem mul_ne_zero_comm {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} :

a * b ≠ 0 ↔ b * a ≠ 0

If α has no zero divisors, then for elements a, b : α, a * b is nonzero iff so is b * a.

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theorem mul_self_eq_zero {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a : M₀} :

a * a = 0 ↔ a = 0

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theorem zero_eq_mul_self {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a : M₀} :

0 = a * a ↔ a = 0

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theorem mul_self_ne_zero {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a : M₀} :

a * a ≠ 0 ↔ a ≠ 0

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theorem zero_ne_mul_self {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a : M₀} :

0 ≠ a * a ↔ a ≠ 0

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theorem mul_eq_zero_iff_left {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} (ha : a ≠ 0) :

a * b = 0 ↔ b = 0

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theorem mul_eq_zero_iff_right {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} (hb : b ≠ 0) :

a * b = 0 ↔ a = 0

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theorem mul_ne_zero_iff_left {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} (ha : a ≠ 0) :

a * b ≠ 0 ↔ b ≠ 0

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theorem mul_ne_zero_iff_right {M₀ : Type u_1} [MulZeroClass M₀] [NoZeroDivisors M₀] {a b : M₀} (hb : b ≠ 0) :

a * b ≠ 0 ↔ a ≠ 0

Documentation

Mathlib.Algebra.GroupWithZero.Defs

Typeclasses for groups with an adjoined zero element #

Main definitions #