Namespaces
Variants
Views
Actions

std::function::function

From cppreference.com
< cpp‎ | utility‎ | functional‎ | function
 
 
 
Function objects
Function wrappers
(C++11)
(C++11)
Bind
(C++11)
Reference wrappers
(C++11)(C++11)
Operator wrappers
Negators
Deprecated binders and adaptors
(deprecated)
(deprecated)
(deprecated)
(deprecated)
(deprecated)(deprecated)(deprecated)(deprecated)
(deprecated)
(deprecated)(deprecated)(deprecated)(deprecated)
(deprecated)(deprecated)
(deprecated)(deprecated)
 
 
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