std::experimental::function<R(Args...)>::function

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

Technical specifications

Symbols index

External libraries

 

Experimental

Technical Specification

Filesystem library (filesystem TS)

Library fundamentals (library fundamentals TS)

Library fundamentals 2 (library fundamentals TS v2)

Library fundamentals 3 (library fundamentals TS v3)

Extensions for parallelism (parallelism TS)

Extensions for parallelism 2 (parallelism TS v2)

Extensions for concurrency (concurrency TS)

Extensions for concurrency 2 (concurrency TS v2)

Concepts (concepts TS)

Ranges (ranges TS)

Reflection (reflection TS)

Mathematical special functions (special functions TR)

Experimental Non-TS

Pattern Matching

Linear Algebra

std::execution

Contracts

2D Graphics

 

Library fundamentals

experimental::optional

experimental::any

experimental::basic_string_view

experimental::sample

experimental::shared_ptr

experimental::weak_ptr

experimental::apply

experimental::invocation_typeexperimental::raw_invocation_type

experimental::search

experimental::default_searcherexperimental::make_default_searcher

experimental::boyer_moore_searcherexperimental::make_boyer_moore_searcher

experimental::boyer_moore_horspool_searcherexperimental::make_boyer_moore_horspool_searcher

Type-erased and polymorphic allocators

Variable templates for type traits

 

Polymorphic allocator library

polymorphic_allocator

Convenience aliases for containers using polymorphic_allocator

Memory resource classes

memory_resource

synchronized_pool_resource

unsynchronized_pool_resource

monotonic_buffer_resource

resource_adaptor

Global memory resources

new_delete_resource

null_memory_resource

get_default_resource

set_default_resource

Type-erased allocator support for existing classes

function

packaged_task

promise

 

function() noexcept;	(1)	(library fundamentals TS)
function( std::nullptr_t ) noexcept;	(2)	(library fundamentals TS)
function( const function& other );	(3)	(library fundamentals TS)
function( function&& other );	(4)	(library fundamentals TS)
template< class F > function( F f );	(5)	(library fundamentals TS)
	(6)
template< class Alloc > function( std::allocator_arg_t, const Alloc& alloc ) noexcept;			(library fundamentals TS)
function( std::allocator_arg_t,           const allocator_type& alloc ) noexcept;			(library fundamentals TS v3)
		(7)
template< class Alloc > function( std::allocator_arg_t, const Alloc& alloc,           std::nullptr_t ) noexcept;				(library fundamentals TS)
function( std::allocator_arg_t, const allocator_type& alloc,           std::nullptr_t ) noexcept;				(library fundamentals TS v3)
			(8)
template< class Alloc > function( std::allocator_arg_t, const Alloc& alloc,           const function& other );					(library fundamentals TS)
function( std::allocator_arg_t, const allocator_type& alloc,           const function& other );					(library fundamentals TS v3)
				(9)
template< class Alloc > function( std::allocator_arg_t, const Alloc& alloc,           function&& other );						(library fundamentals TS)
function( std::allocator_arg_t, const allocator_type& alloc,           function&& other );						(library fundamentals TS v3)
					(10)
template< class F, class Alloc > function( std::allocator_arg_t, const Alloc& alloc, F f );							(library fundamentals TS)
function( std::allocator_arg_t, const allocator_type& alloc, F f );							(library fundamentals TS v3)

Constructs a std::experimental::function from a variety of sources.

1,2) Creates an empty function.

3) Copies the target of other to the target of *this. If other is empty, *this will be empty after the call too.

4) Moves the target of other to the target of *this. If other is empty, *this will be empty after the call too. After construction, *this stores a copy of other.get_allocator().(library fundamentals TS v3)

5) Initializes the target with a copy of f. If f is a null pointer to function or null pointer to member, *this will be empty after the call. This constructor does not participate in overload resolution unless f is Callable for argument types Args... and return type R.

6-10) Same as (1-5) except that alloc is used to allocate memory for any internal data structures that the function might use. These constructors treat alloc as a type-erased allocator (see below).(until library fundamentals TS v3)

After construction via (1-5), this->get_memory_resource() returns the same value as std::experimental::pmr::get_default_resource() during construction.	(library fundamentals TS) (until library fundamentals TS v3)
After construction via (1-3) and (5), *this stores a default constructed std::pmr::polymorphic_allocator<>.	(library fundamentals TS v3)

When the target is a function pointer or a std::reference_wrapper, small object optimization is guaranteed, that is, these targets are always directly stored inside the std::experimental::function object, no dynamic allocation takes place. Other large objects may be constructed in dynamic allocated storage and accessed by the std::experimental::function object through a pointer.

If a constructor moves or copies a function object, including an instance of std::experimental::function, then that move or copy is performed by using-allocator construction with allocator this->get_memory_resource()(until library fundamentals TS v3)this->get_allocator()(library fundamentals TS v3).

Type-erased allocator

The constructors of function taking an allocator argument alloc treats that argument as a type-erased allocator. The memory resource pointer used by function to allocate memory is determined using the allocator argument (if specified) as follows:

Type of alloc	Value of the memory resource pointer
Non-existent (no allocator specified at time of construction)	The value of std::experimental::pmr::get_default_resource() at time of construction.
std::nullptr_t	The value of std::experimental::pmr::get_default_resource() at time of construction.
A pointer type convertible to std::experimental::pmr::memory_resource*	static_cast<std::experimental::pmr::memory_resource*>(alloc)
A specialization of std::experimental::pmr::polymorphic_allocator	alloc.resource()
Any other type meeting the Allocator requirements	A pointer to a value of type std::experimental::pmr::resource_adaptor<A>(alloc), where A is the type of alloc. The pointer remains valid only for the lifetime of the function object.
None of the above	The program is ill-formed.

Parameters

other	-	the function object used to initialize *this
f	-	a callable used to initialize *this
alloc	-	an allocator used for internal memory allocation
Type requirements
- F must meet the requirements of Callable and CopyConstructible.

Exceptions

3,8) Does not throw if other's target is a function pointer or a std::reference_wrapper, otherwise may throw std::bad_alloc or any exception thrown by the copy constructor of the stored callable object.

4) (none)

5,10) Does not throw if f is a function pointer or a std::reference_wrapper, otherwise may throw std::bad_alloc or any exception thrown by the copy constructor of the stored callable object.

9) (none)