Compactly supported continuous functions #
In this file, we define the type C_c(α, β)
of compactly supported continuous functions and the
class CompactlySupportedContinuousMapClass
, and prove basic properties.
Main definitions and results #
This file contains various instances such as Add
, Mul
, SMul F C_c(α, β)
when F
is a class of
continuous functions.
When β
has more structures, C_c(α, β)
inherits such structures as AddCommGroup
,
NonUnitalRing
and StarRing
.
When the domain α
is compact, ContinuousMap.liftCompactlySupported
gives the identification
C(α, β) ≃ C_c(α, β)
.
C_c(α, β)
is the type of continuous functions α → β
with compact support from a topological
space to a topological space with a zero element.
When possible, instead of parametrizing results over f : C_c(α, β)
,
you should parametrize over {F : Type*} [CompactlySupportedContinuousMapClass F α β] (f : F)
.
When you extend this structure, make sure to extend CompactlySupportedContinuousMapClass
.
- toFun : α → β
- continuous_toFun : Continuous self.toFun
- hasCompactSupport' : HasCompactSupport self.toFun
The function has compact support .
Instances For
C_c(α, β)
is the type of continuous functions α → β
with compact support from a topological
space to a topological space with a zero element.
When possible, instead of parametrizing results over f : C_c(α, β)
,
you should parametrize over {F : Type*} [CompactlySupportedContinuousMapClass F α β] (f : F)
.
When you extend this structure, make sure to extend CompactlySupportedContinuousMapClass
.
Equations
Instances For
C_c(α, β)
is the type of continuous functions α → β
with compact support from a topological
space to a topological space with a zero element.
When possible, instead of parametrizing results over f : C_c(α, β)
,
you should parametrize over {F : Type*} [CompactlySupportedContinuousMapClass F α β] (f : F)
.
When you extend this structure, make sure to extend CompactlySupportedContinuousMapClass
.
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Instances For
CompactlySupportedContinuousMapClass F α β
states that F
is a type of continuous maps with
compact support.
You should also extend this typeclass when you extend CompactlySupportedContinuousMap
.
- hasCompactSupport (f : F) : HasCompactSupport ⇑f
Each member of the class has compact support.
Instances
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Copy of a CompactlySupportedContinuousMap
with a new toFun
equal to the old one. Useful
to fix definitional equalities.
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Instances For
A continuous function on a compact space automatically has compact support.
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Instances For
Composition of a continuous function f
with compact support with another continuous function
g
sending 0
to 0
from the left yields another continuous function g ∘ f
with compact
support.
If g
doesn't send 0
to 0
, f.compLeft g
defaults to 0
.
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Instances For
Algebraic structure #
Whenever β
has the structure of continuous additive monoid and a compatible topological structure,
then C_c(α, β)
inherits a corresponding algebraic structure. The primary exception to this is that
C_c(α, β)
will not have a multiplicative identity.
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the product of f : F
assuming ContinuousMapClass F α γ
and ContinuousSMul γ β
and
g : C_c(α, β)
is in C_c(α, β)
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Coercion to a function as a AddMonoidHom
. Similar to AddMonoidHom.coeFn
.
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Star structure #
It is possible to equip C_c(α, β)
with a pointwise star
operation whenever there is a continuous
star : β → β
for which star (0 : β) = 0
. We don't have quite this weak a typeclass, but
StarAddMonoid
is close enough.
The StarAddMonoid
class on C_c(α, β)
is inherited from their counterparts on α →ᵇ β
.
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The partial order in C_c
#
When β
is equipped with a partial order, C_c(α, β)
is given the pointwise partial order.
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C_c
as a functor #
For each β
with sufficient structure, there is a contravariant functor C_c(-, β)
from the
category of topological spaces with morphisms given by CocompactMap
s.
Composition of a continuous function with compact support with a cocompact map yields another continuous function with compact support.
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Composition as an additive monoid homomorphism.
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Composition as a semigroup homomorphism.
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Composition as a linear map.
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Composition as a non-unital algebra homomorphism.
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A continuous function on a compact space has automatically compact support. This is not an instance to avoid type class loops.
The nonnegative part of a bounded continuous ℝ
-valued function as a bounded
continuous ℝ≥0
-valued function.
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The compactly supported continuous ℝ≥0
-valued function as a compactly supported ℝ
-valued
function.
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The map toReal
defined as a ℝ≥0
-linear map.
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Instances For
For a positive linear functional Λ : C_c(α, ℝ) → ℝ
, define a ℝ≥0
-linear map.
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Instances For
For a positive linear functional Λ : C_c(α, ℝ≥0) → ℝ≥0
, define a ℝ
-linear map.