mathlib3 documentation

algebra.order.kleene

Kleene Algebras #

THIS FILE IS SYNCHRONIZED WITH MATHLIB4. Any changes to this file require a corresponding PR to mathlib4.

This file defines idempotent semirings and Kleene algebras, which are used extensively in the theory of computation.

An idempotent semiring is a semiring whose addition is idempotent. An idempotent semiring is naturally a semilattice by setting a ≤ b if a + b = b.

A Kleene algebra is an idempotent semiring equipped with an additional unary operator ∗, the Kleene star.

Main declarations #

Notation #

a∗ is notation for kstar a in locale computability.

References #

TODO #

Instances for add_opposite, mul_opposite, ulift, subsemiring, subring, subalgebra.

Tags #

kleene algebra, idempotent semiring

@[instance]
def idem_semiring.to_semiring (α : Type u) [self : idem_semiring α] :
@[class]
structure idem_semiring (α : Type u) :

An idempotent semiring is a semiring with the additional property that addition is idempotent.

Instances of this typeclass
Instances of other typeclasses for idem_semiring
  • idem_semiring.has_sizeof_inst
@[instance]
@[class]
structure idem_comm_semiring (α : Type u) :

An idempotent commutative semiring is a commutative semiring with the additional property that addition is idempotent.

Instances of this typeclass
Instances of other typeclasses for idem_comm_semiring
  • idem_comm_semiring.has_sizeof_inst
@[class]
structure has_kstar (α : Type u_5) :
Type u_5
  • kstar : α → α

Notation typeclass for the Kleene star ∗.

Instances of this typeclass
Instances of other typeclasses for has_kstar
  • has_kstar.has_sizeof_inst
@[instance]
@[class]
structure kleene_algebra (α : Type u_5) :
Type u_5

A Kleene Algebra is an idempotent semiring with an additional unary operator kstar (for Kleene star) that satisfies the following properties:

  • 1 + a * a∗ ≤ a∗
  • 1 + a∗ * a ≤ a∗
  • If a * c + b ≤ c, then a∗ * b ≤ c
  • If c * a + b ≤ c, then b * a∗ ≤ c
Instances of this typeclass
Instances of other typeclasses for kleene_algebra
  • kleene_algebra.has_sizeof_inst
@[instance]
def kleene_algebra.to_has_kstar (α : Type u_5) [self : kleene_algebra α] :
@[protected, instance]
Equations
@[reducible]
def idem_semiring.of_semiring {α : Type u_1} [semiring α] (h : ∀ (a : α), a + a = a) :

Construct an idempotent semiring from an idempotent addition.

Equations
@[simp]
theorem add_eq_sup {α : Type u_1} [idem_semiring α] (a b : α) :
a + b = a ⊔ b
theorem add_idem {α : Type u_1} [idem_semiring α] (a : α) :
a + a = a
theorem nsmul_eq_self {α : Type u_1} [idem_semiring α] {n : ℕ} (hn : n ≠ 0) (a : α) :
n • a = a
theorem add_eq_left_iff_le {α : Type u_1} [idem_semiring α] {a b : α} :
a + b = a ↔ b ≤ a
theorem add_eq_right_iff_le {α : Type u_1} [idem_semiring α] {a b : α} :
a + b = b ↔ a ≤ b
theorem has_le.le.add_eq_left {α : Type u_1} [idem_semiring α] {a b : α} :
b ≤ a → a + b = a

Alias of the reverse direction of add_eq_left_iff_le.

theorem has_le.le.add_eq_right {α : Type u_1} [idem_semiring α] {a b : α} :
a ≤ b → a + b = b

Alias of the reverse direction of add_eq_right_iff_le.

theorem add_le_iff {α : Type u_1} [idem_semiring α] {a b c : α} :
a + b ≤ c ↔ a ≤ c ∧ b ≤ c
theorem add_le {α : Type u_1} [idem_semiring α] {a b c : α} (ha : a ≤ c) (hb : b ≤ c) :
a + b ≤ c
@[simp]
theorem one_le_kstar {α : Type u_1} [kleene_algebra α] {a : α} :
theorem mul_kstar_le_kstar {α : Type u_1} [kleene_algebra α] {a : α} :
theorem kstar_mul_le_kstar {α : Type u_1} [kleene_algebra α] {a : α} :
theorem mul_kstar_le_self {α : Type u_1} [kleene_algebra α] {a b : α} :
theorem kstar_mul_le_self {α : Type u_1} [kleene_algebra α] {a b : α} :
theorem mul_kstar_le {α : Type u_1} [kleene_algebra α] {a b c : α} (hb : b ≤ c) (ha : c * a ≤ c) :
theorem kstar_mul_le {α : Type u_1} [kleene_algebra α] {a b c : α} (hb : b ≤ c) (ha : a * c ≤ c) :
theorem kstar_le_of_mul_le_left {α : Type u_1} [kleene_algebra α] {a b : α} (hb : 1 ≤ b) :
theorem kstar_le_of_mul_le_right {α : Type u_1} [kleene_algebra α] {a b : α} (hb : 1 ≤ b) :
@[simp]
theorem le_kstar {α : Type u_1} [kleene_algebra α] {a : α} :
@[simp]
theorem kstar_eq_one {α : Type u_1} [kleene_algebra α] {a : α} :
@[simp]
theorem kstar_zero {α : Type u_1} [kleene_algebra α] :
@[simp]
theorem kstar_one {α : Type u_1} [kleene_algebra α] :
@[simp]
@[simp]
theorem kstar_eq_self {α : Type u_1} [kleene_algebra α] {a : α} :
has_kstar.kstar a = a ↔ a * a = a ∧ 1 ≤ a
@[simp]
theorem kstar_idem {α : Type u_1} [kleene_algebra α] (a : α) :
@[simp]
theorem pow_le_kstar {α : Type u_1} [kleene_algebra α] {a : α} {n : ℕ} :
theorem prod.kstar_def {α : Type u_1} {β : Type u_2} [kleene_algebra α] [kleene_algebra β] (a : α × β) :
@[simp]
theorem prod.fst_kstar {α : Type u_1} {β : Type u_2} [kleene_algebra α] [kleene_algebra β] (a : α × β) :
@[simp]
theorem prod.snd_kstar {α : Type u_1} {β : Type u_2} [kleene_algebra α] [kleene_algebra β] (a : α × β) :
theorem pi.kstar_def {ι : Type u_3} {π : ι → Type u_4} [Π (i : ι), kleene_algebra (π i)] (a : Π (i : ι), π i) :
has_kstar.kstar a = λ (i : ι), has_kstar.kstar (a i)
@[simp]
theorem pi.kstar_apply {ι : Type u_3} {π : ι → Type u_4} [Π (i : ι), kleene_algebra (π i)] (a : Π (i : ι), π i) (i : ι) :
@[protected, reducible]
def function.injective.idem_semiring {α : Type u_1} {β : Type u_2} [idem_semiring α] [has_zero β] [has_one β] [has_add β] [has_mul β] [has_pow β ℕ] [has_smul ℕ β] [has_nat_cast β] [has_sup β] [has_bot β] (f : β → α) (hf : function.injective f) (zero : f 0 = 0) (one : f 1 = 1) (add : ∀ (x y : β), f (x + y) = f x + f y) (mul : ∀ (x y : β), f (x * y) = f x * f y) (nsmul : ∀ (x : β) (n : ℕ), f (n • x) = n • f x) (npow : ∀ (x : β) (n : ℕ), f (x ^ n) = f x ^ n) (nat_cast : ∀ (n : ℕ), f ↑n = ↑n) (sup : ∀ (a b : β), f (a ⊔ b) = f a ⊔ f b) (bot : f ⊥ = ⊥) :

Pullback an idem_semiring instance along an injective function.

Equations
@[protected, reducible]
def function.injective.idem_comm_semiring {α : Type u_1} {β : Type u_2} [idem_comm_semiring α] [has_zero β] [has_one β] [has_add β] [has_mul β] [has_pow β ℕ] [has_smul ℕ β] [has_nat_cast β] [has_sup β] [has_bot β] (f : β → α) (hf : function.injective f) (zero : f 0 = 0) (one : f 1 = 1) (add : ∀ (x y : β), f (x + y) = f x + f y) (mul : ∀ (x y : β), f (x * y) = f x * f y) (nsmul : ∀ (x : β) (n : ℕ), f (n • x) = n • f x) (npow : ∀ (x : β) (n : ℕ), f (x ^ n) = f x ^ n) (nat_cast : ∀ (n : ℕ), f ↑n = ↑n) (sup : ∀ (a b : β), f (a ⊔ b) = f a ⊔ f b) (bot : f ⊥ = ⊥) :

Pullback an idem_comm_semiring instance along an injective function.

Equations
@[protected, reducible]
def function.injective.kleene_algebra {α : Type u_1} {β : Type u_2} [kleene_algebra α] [has_zero β] [has_one β] [has_add β] [has_mul β] [has_pow β ℕ] [has_smul ℕ β] [has_nat_cast β] [has_sup β] [has_bot β] [has_kstar β] (f : β → α) (hf : function.injective f) (zero : f 0 = 0) (one : f 1 = 1) (add : ∀ (x y : β), f (x + y) = f x + f y) (mul : ∀ (x y : β), f (x * y) = f x * f y) (nsmul : ∀ (x : β) (n : ℕ), f (n • x) = n • f x) (npow : ∀ (x : β) (n : ℕ), f (x ^ n) = f x ^ n) (nat_cast : ∀ (n : ℕ), f ↑n = ↑n) (sup : ∀ (a b : β), f (a ⊔ b) = f a ⊔ f b) (bot : f ⊥ = ⊥) (kstar : ∀ (a : β), f (has_kstar.kstar a) = has_kstar.kstar (f a)) :

Pullback an idem_comm_semiring instance along an injective function.

Equations