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# std::function::function

From cppreference.com
< cpp‎ | utility‎ | functional‎ | function

function(); | (1) | (since C++11)
function( std::nullptr_t ); | (2) | (since C++11)
function( const function& other ); | (3) | (since C++11)
function( function&& other ); | (4) | (since C++11)
template< class F > function( F f ); | (5) | (since C++11)
template< class Alloc > function( std::allocator_arg_t, const Alloc& alloc ); | (6) | (since C++11)
template< class Alloc > function( std::allocator_arg_t, const Alloc& alloc, std::nullptr_t ); | (7) | (since C++11)
template< class Alloc > function( std::allocator_arg_t, const Alloc& alloc, const function& other ); | (8) | (since C++11)
template< class Alloc > function( std::allocator_arg_t, const Alloc& alloc, function&& other ); | (9) | (since C++11)
template< class F, class Alloc > function( std::allocator_arg_t, const Alloc& alloc, F f ); | (10) | (since C++11)

Constructs a `std::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`. (since C++14)
6-10) Same as (1-5) just that `alloc` is used to allocate memory for any internal data structures that the `function` might use.

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::function object, no dynamic allocation takes place. Other large objects may be constructed in dynamic allocated storage and accessed by the std::function object through a pointer.

### [edit] 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`.
- `Alloc` must meet the requirements of `Allocator`.

### [edit] 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)
`noexcept` specification:
noexcept
9) (none)

### [edit] Example

| This section is incomplete Reason: no example

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Categories:

- unconditionally noexcept
- Todo no example