[customization.point.object]

# 16 Library introduction [[library]](./#library)

## 16.3 Method of description [[description]](description#customization.point.object)

### 16.3.3 Other conventions [[conventions]](conventions#customization.point.object)

#### 16.3.3.3 Type descriptions [[type.descriptions]](type.descriptions#customization.point.object)

#### 16.3.3.3.5 Customization Point Object types [customization.point.object]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L853)

A [*customization point object*](#def:customization_point_object) is a function object ([[function.objects]](function.objects "22.10 Function objects"))
with a literal class type that interacts with program-defined types while
enforcing semantic requirements on that interaction[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L858)

The type of a customization point object, ignoring cv-qualifiers, shall model[semiregular](concepts.object#concept:semiregular "18.6 Object concepts [concepts.object]") ([[concepts.object]](concepts.object "18.6 Object concepts"))[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L862)

All instances of a specific customization point object type shall
be equal ([[concepts.equality]](concepts.equality "18.2 Equality preservation"))[.](#3.sentence-1)

The effects of invoking different instances
of a specific customization point object type on the same arguments
are equivalent[.](#3.sentence-2)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L869)

The type T of a customization point object,
ignoring [*cv-qualifier*](dcl.decl.general#nt:cv-qualifier "9.3.1 General [dcl.decl.general]")*s*, shall model[invocable](concept.invocable#concept:invocable "18.7.2 Concept invocable [concept.invocable]")<T&, Args...>,[invocable](concept.invocable#concept:invocable "18.7.2 Concept invocable [concept.invocable]")<const T&, Args...>,[invocable](concept.invocable#concept:invocable "18.7.2 Concept invocable [concept.invocable]")<T, Args...>, and[invocable](concept.invocable#concept:invocable "18.7.2 Concept invocable [concept.invocable]")<const T, Args...> ([[concept.invocable]](concept.invocable "18.7.2 Concept invocable"))
when the types in Args... meet the requirements specified in that
customization point object's definition[.](#4.sentence-1)

When the types of Args... do
not meet the customization point object's requirements, T shall not have
a function call operator that participates in overload resolution[.](#4.sentence-2)

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L881)

For a given customization point object o,
let p be a variable initialized as if by auto p = o;[.](#5.sentence-1)

Then for any sequence of arguments args...,
the following expressions have effects equivalent to o(args...):

- [(5.1)](#5.1)

p(args...)

- [(5.2)](#5.2)

as_const(p)(args...)

- [(5.3)](#5.3)

std​::​move(p)(args...)

- [(5.4)](#5.4)

std​::​move(as_const(p))(args...)