Pointwise operations on filters #
This file defines pointwise operations on filters. This is useful because usual algebraic operations distribute over pointwise operations. For example,
(f₁ * f₂).map m = f₁.map m * f₂.map m𝓝 (x * y) = 𝓝 x * 𝓝 y
Main declarations #
0(Filter.instZero): Pure filter at0 : α, or alternatively principal filter at0 : Set α.1(Filter.instOne): Pure filter at1 : α, or alternatively principal filter at1 : Set α.f + g(Filter.instAdd): Addition, filter generated by alls + twheres ∈ fandt ∈ g.f * g(Filter.instMul): Multiplication, filter generated by alls * twheres ∈ fandt ∈ g.-f(Filter.instNeg): Negation, filter of all-swheres ∈ f.f⁻¹(Filter.instInv): Inversion, filter of alls⁻¹wheres ∈ f.f - g(Filter.instSub): Subtraction, filter generated by alls - twheres ∈ fandt ∈ g.f / g(Filter.instDiv): Division, filter generated by alls / twheres ∈ fandt ∈ g.f +ᵥ g(Filter.instVAdd): Scalar addition, filter generated by alls +ᵥ twheres ∈ fandt ∈ g.f -ᵥ g(Filter.instVSub): Scalar subtraction, filter generated by alls -ᵥ twheres ∈ fandt ∈ g.f • g(Filter.instSMul): Scalar multiplication, filter generated by alls • twheres ∈ fandt ∈ g.a +ᵥ f(Filter.instVAddFilter): Translation, filter of alla +ᵥ swheres ∈ f.a • f(Filter.instSMulFilter): Scaling, filter of alla • swheres ∈ f.
For α a semigroup/monoid, Filter α is a semigroup/monoid.
As an unfortunate side effect, this means that n • f, where n : ℕ, is ambiguous between
pointwise scaling and repeated pointwise addition. See note [pointwise nat action].
Implementation notes #
We put all instances in the locale Pointwise, so that these instances are not available by
default. Note that we do not mark them as reducible (as argued by note [reducible non-instances])
since we expect the locale to be open whenever the instances are actually used (and making the
instances reducible changes the behavior of simp).
Tags #
filter multiplication, filter addition, pointwise addition, pointwise multiplication,
0/1 as filters #
Filter negation/inversion #
The negation of a filter is the pointwise preimage under - of its sets.
Equations
- Filter.instNeg = { neg := Filter.map Neg.neg }
The inverse of a filter is the pointwise preimage under ⁻¹ of its sets.
Equations
- Filter.instInv = { inv := Filter.map Inv.inv }
Negation is involutive on Filter α if it is on α.
Equations
- Filter.instInvolutiveNeg = let __src := Filter.instNeg; InvolutiveNeg.mk ⋯
Instances For
Inversion is involutive on Filter α if it is on α.
Equations
- Filter.instInvolutiveInv = let __src := Filter.instInv; InvolutiveInv.mk ⋯
Instances For
Filter addition/multiplication #
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Filter subtraction/division #
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Repeated pointwise multiplication/division (not the same as pointwise repeated
multiplication/division!) of a Filter. See Note [pointwise nat action].
Instances For
Filter α is an AddSemigroup under pointwise operations if α is.
Equations
- Filter.addSemigroup = AddSemigroup.mk ⋯
Instances For
Filter α is a Semigroup under pointwise operations if α is.
Equations
- Filter.semigroup = Semigroup.mk ⋯
Instances For
Filter α is an AddCommSemigroup under pointwise operations if α is.
Equations
- Filter.addCommSemigroup = let __src := Filter.addSemigroup; AddCommSemigroup.mk ⋯
Instances For
Filter α is a CommSemigroup under pointwise operations if α is.
Equations
- Filter.commSemigroup = let __src := Filter.semigroup; CommSemigroup.mk ⋯
Instances For
Filter α is an AddZeroClass under pointwise operations if α is.
Equations
- Filter.addZeroClass = AddZeroClass.mk ⋯ ⋯
Instances For
Filter α is a MulOneClass under pointwise operations if α is.
Equations
- Filter.mulOneClass = MulOneClass.mk ⋯ ⋯
Instances For
If φ : α →+ β then mapAddMonoidHom φ is the monoid homomorphism
Filter α →+ Filter β induced by map φ.
Equations
- Filter.mapAddMonoidHom φ = { toFun := Filter.map ⇑φ, map_zero' := ⋯, map_add' := ⋯ }
Instances For
If φ : α →* β then mapMonoidHom φ is the monoid homomorphism
Filter α →* Filter β induced by map φ.
Equations
- Filter.mapMonoidHom φ = { toFun := Filter.map ⇑φ, map_one' := ⋯, map_mul' := ⋯ }
Instances For
Equations
- ⋯ = ⋯
Instances For
pure as an AddMonoidHom.
Equations
- Filter.pureAddMonoidHom = let __src := Filter.pureAddHom; let __src_1 := Filter.pureZeroHom; { toFun := __src.toFun, map_zero' := ⋯, map_add' := ⋯ }
Instances For
Filter α is an AddMonoid under pointwise operations if α is.
Equations
- Filter.addMonoid = let __src := Filter.addZeroClass; let __src_1 := Filter.addSemigroup; let __src_2 := Filter.instNSMul; AddMonoid.mk ⋯ ⋯ nsmulRec ⋯ ⋯
Instances For
Filter α is an AddCommMonoid under pointwise operations if α is.
Equations
- Filter.addCommMonoid = let __src := Filter.addZeroClass; let __src_1 := Filter.addCommSemigroup; AddCommMonoid.mk ⋯
Instances For
Filter α is a CommMonoid under pointwise operations if α is.
Equations
- Filter.commMonoid = let __src := Filter.mulOneClass; let __src_1 := Filter.commSemigroup; CommMonoid.mk ⋯
Instances For
Filter α is a subtraction monoid under pointwise operations if
α is.
Equations
- Filter.subtractionMonoid = let __src := Filter.addMonoid; let __src_1 := Filter.instInvolutiveNeg; let __src_2 := Filter.instSub; let __src_3 := Filter.instZSMul; SubtractionMonoid.mk ⋯ ⋯ ⋯
Instances For
Filter α is a division monoid under pointwise operations if α is.
Equations
- Filter.divisionMonoid = let __src := Filter.monoid; let __src_1 := Filter.instInvolutiveInv; let __src_2 := Filter.instDiv; let __src_3 := Filter.instZPow; DivisionMonoid.mk ⋯ ⋯ ⋯
Instances For
Filter α is a commutative subtraction monoid under pointwise operations if α is.
Equations
- Filter.subtractionCommMonoid = let __src := Filter.subtractionMonoid; let __src_1 := Filter.addCommSemigroup; SubtractionCommMonoid.mk ⋯
Instances For
Filter α is a commutative division monoid under pointwise operations if α is.
Equations
- Filter.divisionCommMonoid = let __src := Filter.divisionMonoid; let __src_1 := Filter.commSemigroup; DivisionCommMonoid.mk ⋯
Instances For
Filter α has distributive negation if α has.
Equations
- Filter.instDistribNeg = let __src := Filter.instInvolutiveNeg; HasDistribNeg.mk ⋯ ⋯
Instances For
Note that Filter is not a MulZeroClass because 0 * ⊥ ≠ 0.
Note that Filter α is not a group because f / f ≠ 1 in general
Scalar addition/multiplication of filters #
Scalar subtraction of filters #
Translation/scaling of filters #
a +ᵥ f is the map of f under a +ᵥ in locale Pointwise.
Equations
- Filter.instVAddFilter = { vadd := fun (a : α) => Filter.map fun (x : β) => a +ᵥ x }
Instances For
a • f is the map of f under a • in locale Pointwise.
Equations
- Filter.instSMulFilter = { smul := fun (a : α) => Filter.map fun (x : β) => a • x }
Instances For
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
Equations
- ⋯ = ⋯
A distributive multiplicative action of a monoid on an additive monoid β gives a distributive
multiplicative action on Filter β.
Equations
- Filter.distribMulActionFilter = DistribMulAction.mk ⋯ ⋯
Instances For
A multiplicative action of a monoid on a monoid β gives a multiplicative action on Set β.
Equations
- Filter.mulDistribMulActionFilter = MulDistribMulAction.mk ⋯ ⋯
Instances For
Note that we have neither SMulWithZero α (Filter β) nor SMulWithZero (Filter α) (Filter β)
because 0 * ⊥ ≠ 0.