std::experimental::function::function

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

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

1-2) Creates an empty function.

3-4) Copies (3) or moves (4) the target of other to the target of *this. If other is empty, *this will be empty after the call too.

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).

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().

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

1-2)

noexcept specification:

noexcept

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.

6-7)