Ordered rings and semirings #
This file develops the basics of ordered (semi)rings.
Each typeclass here comprises
- an algebraic class (
Semiring
,CommSemiring
,Ring
,CommRing
) - an order class (
PartialOrder
,LinearOrder
) - assumptions on how both interact ((strict) monotonicity, canonicity)
For short,
- "
+
respects≤
" means "monotonicity of addition" - "
+
respects<
" means "strict monotonicity of addition" - "
*
respects≤
" means "monotonicity of multiplication by a nonnegative number". - "
*
respects<
" means "strict monotonicity of multiplication by a positive number".
Typeclasses #
OrderedSemiring
: Semiring with a partial order such that+
and*
respect≤
.StrictOrderedSemiring
: Nontrivial semiring with a partial order such that+
and*
respects<
.OrderedCommSemiring
: Commutative semiring with a partial order such that+
and*
respect≤
.StrictOrderedCommSemiring
: Nontrivial commutative semiring with a partial order such that+
and*
respect<
.OrderedRing
: Ring with a partial order such that+
respects≤
and*
respects<
.OrderedCommRing
: Commutative ring with a partial order such that+
respects≤
and*
respects<
.LinearOrderedSemiring
: Nontrivial semiring with a linear order such that+
respects≤
and*
respects<
.LinearOrderedCommSemiring
: Nontrivial commutative semiring with a linear order such that+
respects≤
and*
respects<
.LinearOrderedRing
: Nontrivial ring with a linear order such that+
respects≤
and*
respects<
.LinearOrderedCommRing
: Nontrivial commutative ring with a linear order such that+
respects≤
and*
respects<
.CanonicallyOrderedCommSemiring
: Commutative semiring with a partial order such that+
respects≤
,*
respects<
, anda ≤ b ↔ ∃ c, b = a + c
.
Hierarchy #
The hardest part of proving order lemmas might be to figure out the correct generality and its corresponding typeclass. Here's an attempt at demystifying it. For each typeclass, we list its immediate predecessors and what conditions are added to each of them.
OrderedSemiring
OrderedAddCommMonoid
& multiplication &*
respects≤
Semiring
& partial order structure &+
respects≤
&*
respects≤
StrictOrderedSemiring
OrderedCancelAddCommMonoid
& multiplication &*
respects<
& nontrivialityOrderedSemiring
&+
respects<
&*
respects<
& nontriviality
OrderedCommSemiring
OrderedSemiring
& commutativity of multiplicationCommSemiring
& partial order structure &+
respects≤
&*
respects<
StrictOrderedCommSemiring
StrictOrderedSemiring
& commutativity of multiplicationOrderedCommSemiring
&+
respects<
&*
respects<
& nontriviality
OrderedRing
OrderedSemiring
& additive inversesOrderedAddCommGroup
& multiplication &*
respects<
Ring
& partial order structure &+
respects≤
&*
respects<
StrictOrderedRing
StrictOrderedSemiring
& additive inversesOrderedSemiring
&+
respects<
&*
respects<
& nontriviality
OrderedCommRing
OrderedRing
& commutativity of multiplicationOrderedCommSemiring
& additive inversesCommRing
& partial order structure &+
respects≤
&*
respects<
StrictOrderedCommRing
StrictOrderedCommSemiring
& additive inversesStrictOrderedRing
& commutativity of multiplicationOrderedCommRing
&+
respects<
&*
respects<
& nontriviality
LinearOrderedSemiring
StrictOrderedSemiring
& totality of the orderLinearOrderedAddCommMonoid
& multiplication & nontriviality &*
respects<
LinearOrderedCommSemiring
StrictOrderedCommSemiring
& totality of the orderLinearOrderedSemiring
& commutativity of multiplication
LinearOrderedRing
StrictOrderedRing
& totality of the orderLinearOrderedSemiring
& additive inversesLinearOrderedAddCommGroup
& multiplication &*
respects<
Ring
&IsDomain
& linear order structure
LinearOrderedCommRing
StrictOrderedCommRing
& totality of the orderLinearOrderedRing
& commutativity of multiplicationLinearOrderedCommSemiring
& additive inversesCommRing
&IsDomain
& linear order structure
Note that OrderDual
does not satisfy any of the ordered ring typeclasses due to the
zero_le_one
field.
An OrderedSemiring
is a semiring with a partial order such that addition is monotone and
multiplication by a nonnegative number is monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- zero_le_one : 0 ≤ 1
0 ≤ 1
in any ordered semiring. In an ordered semiring, we can multiply an inequality
a ≤ b
on the left by a non-negative element0 ≤ c
to obtainc * a ≤ c * b
.In an ordered semiring, we can multiply an inequality
a ≤ b
on the right by a non-negative element0 ≤ c
to obtaina * c ≤ b * c
.
Instances
An OrderedCommSemiring
is a commutative semiring with a partial order such that addition is
monotone and multiplication by a nonnegative number is monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- zero_le_one : 0 ≤ 1
Instances
An OrderedRing
is a ring with a partial order such that addition is monotone and
multiplication by a nonnegative number is monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- neg : α → α
- sub : α → α → α
- zero_le_one : 0 ≤ 1
0 ≤ 1
in any ordered ring. The product of non-negative elements is non-negative.
Instances
An OrderedCommRing
is a commutative ring with a partial order such that addition is monotone
and multiplication by a nonnegative number is monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- neg : α → α
- sub : α → α → α
- zero_le_one : 0 ≤ 1
Instances
A StrictOrderedSemiring
is a nontrivial semiring with a partial order such that addition is
strictly monotone and multiplication by a positive number is strictly monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- exists_pair_ne : ∃ (x : α), ∃ (y : α), x ≠ y
- zero_le_one : 0 ≤ 1
In a strict ordered semiring,
0 ≤ 1
. Left multiplication by a positive element is strictly monotone.
Right multiplication by a positive element is strictly monotone.
Instances
A StrictOrderedCommSemiring
is a commutative semiring with a partial order such that
addition is strictly monotone and multiplication by a positive number is strictly monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- exists_pair_ne : ∃ (x : α), ∃ (y : α), x ≠ y
- zero_le_one : 0 ≤ 1
Instances
A StrictOrderedRing
is a ring with a partial order such that addition is strictly monotone
and multiplication by a positive number is strictly monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- neg : α → α
- sub : α → α → α
- exists_pair_ne : ∃ (x : α), ∃ (y : α), x ≠ y
- zero_le_one : 0 ≤ 1
In a strict ordered ring,
0 ≤ 1
. The product of two positive elements is positive.
Instances
A StrictOrderedCommRing
is a commutative ring with a partial order such that addition is
strictly monotone and multiplication by a positive number is strictly monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- neg : α → α
- sub : α → α → α
- exists_pair_ne : ∃ (x : α), ∃ (y : α), x ≠ y
- zero_le_one : 0 ≤ 1
Instances
A LinearOrderedSemiring
is a nontrivial semiring with a linear order such that
addition is monotone and multiplication by a positive number is strictly monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- exists_pair_ne : ∃ (x : α), ∃ (y : α), x ≠ y
- zero_le_one : 0 ≤ 1
- min : α → α → α
- max : α → α → α
- decidableLE : DecidableRel fun (x1 x2 : α) => x1 ≤ x2
- decidableLT : DecidableRel fun (x1 x2 : α) => x1 < x2
Instances
A LinearOrderedCommSemiring
is a nontrivial commutative semiring with a linear order such
that addition is monotone and multiplication by a positive number is strictly monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- exists_pair_ne : ∃ (x : α), ∃ (y : α), x ≠ y
- zero_le_one : 0 ≤ 1
- min : α → α → α
- max : α → α → α
- decidableLE : DecidableRel fun (x1 x2 : α) => x1 ≤ x2
- decidableLT : DecidableRel fun (x1 x2 : α) => x1 < x2
Instances
A LinearOrderedRing
is a ring with a linear order such that addition is monotone and
multiplication by a positive number is strictly monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- neg : α → α
- sub : α → α → α
- exists_pair_ne : ∃ (x : α), ∃ (y : α), x ≠ y
- zero_le_one : 0 ≤ 1
- min : α → α → α
- max : α → α → α
- decidableLE : DecidableRel fun (x1 x2 : α) => x1 ≤ x2
- decidableLT : DecidableRel fun (x1 x2 : α) => x1 < x2
Instances
A LinearOrderedCommRing
is a commutative ring with a linear order such that addition is
monotone and multiplication by a positive number is strictly monotone.
- add : α → α → α
- zero : α
- mul : α → α → α
- one : α
- natCast_zero : NatCast.natCast 0 = 0
- neg : α → α
- sub : α → α → α
- exists_pair_ne : ∃ (x : α), ∃ (y : α), x ≠ y
- zero_le_one : 0 ≤ 1
- min : α → α → α
- max : α → α → α
- decidableLE : DecidableRel fun (x1 x2 : α) => x1 ≤ x2
- decidableLT : DecidableRel fun (x1 x2 : α) => x1 < x2
Instances
Equations
- OrderedRing.toOrderedSemiring = OrderedSemiring.mk ⋯ ⋯ ⋯ ⋯
Equations
- OrderedCommRing.toOrderedCommSemiring = OrderedCommSemiring.mk ⋯
A choice-free version of StrictOrderedSemiring.toOrderedSemiring
to avoid using choice in
basic Nat
lemmas.
Equations
- StrictOrderedSemiring.toOrderedSemiring' = OrderedSemiring.mk ⋯ ⋯ ⋯ ⋯
Instances For
Equations
- StrictOrderedSemiring.toOrderedSemiring = OrderedSemiring.mk ⋯ ⋯ ⋯ ⋯
A choice-free version of StrictOrderedCommSemiring.toOrderedCommSemiring'
to avoid using
choice in basic Nat
lemmas.
Equations
- StrictOrderedCommSemiring.toOrderedCommSemiring' = OrderedCommSemiring.mk ⋯
Instances For
Equations
- StrictOrderedCommSemiring.toOrderedCommSemiring = OrderedCommSemiring.mk ⋯
Equations
- StrictOrderedRing.toStrictOrderedSemiring = StrictOrderedSemiring.mk ⋯ ⋯ ⋯ ⋯ ⋯
A choice-free version of StrictOrderedRing.toOrderedRing
to avoid using choice in basic
Int
lemmas.
Equations
- StrictOrderedRing.toOrderedRing' = OrderedRing.mk ⋯ ⋯ ⋯
Instances For
Equations
- StrictOrderedRing.toOrderedRing = OrderedRing.mk ⋯ ⋯ ⋯
A choice-free version of StrictOrderedCommRing.toOrderedCommRing
to avoid using
choice in basic Int
lemmas.
Equations
- StrictOrderedCommRing.toOrderedCommRing' = OrderedCommRing.mk ⋯
Instances For
Equations
- StrictOrderedCommRing.toStrictOrderedCommSemiring = StrictOrderedCommSemiring.mk ⋯
Equations
- StrictOrderedCommRing.toOrderedCommRing = OrderedCommRing.mk ⋯
Equations
- One or more equations did not get rendered due to their size.
Equations
- LinearOrderedRing.toLinearOrderedSemiring = LinearOrderedSemiring.mk ⋯ LinearOrderedRing.decidableLE LinearOrderedRing.decidableEq LinearOrderedRing.decidableLT ⋯ ⋯ ⋯
Equations
- LinearOrderedRing.toLinearOrderedAddCommGroup = LinearOrderedAddCommGroup.mk ⋯ LinearOrderedRing.decidableLE LinearOrderedRing.decidableEq LinearOrderedRing.decidableLT ⋯ ⋯ ⋯
Equations
- LinearOrderedCommRing.toStrictOrderedCommRing = StrictOrderedCommRing.mk ⋯
Equations
- LinearOrderedCommRing.toLinearOrderedCommSemiring = LinearOrderedCommSemiring.mk ⋯ LinearOrderedRing.decidableLE LinearOrderedRing.decidableEq LinearOrderedRing.decidableLT ⋯ ⋯ ⋯