std::copyable_function - cppreference.com (original) (raw)

Defined in header
template< class... > class copyable_function; // not defined	(1)	(since C++26)
template< class R, class... Args > class copyable_function<R(Args...)>; template< class R, class... Args > class copyable_function<R(Args...) noexcept>; template< class R, class... Args > class copyable_function<R(Args...) &>; template< class R, class... Args > class copyable_function<R(Args...) & noexcept>; template< class R, class... Args > class copyable_function<R(Args...) &&>; template< class R, class... Args > class copyable_function<R(Args...) && noexcept>; template< class R, class... Args > class copyable_function<R(Args...) const>; template< class R, class... Args > class copyable_function<R(Args...) const noexcept>; template< class R, class... Args > class copyable_function<R(Args...) const &>; template< class R, class... Args > class copyable_function<R(Args...) const & noexcept>; template< class R, class... Args > class copyable_function<R(Args...) const &&>; template< class R, class... Args > class copyable_function<R(Args...) const && noexcept>;	(2)	(since C++26)

Class template std::copyable_function is a general-purpose polymorphic function wrapper. std::copyable_function objects can store and invoke any CopyConstructible Callable target — functions, lambda expressions, bind expressions, or other function objects, as well as pointers to member functions and pointers to member objects.

The stored callable object is called the target of std::copyable_function. If a std::copyable_function contains no target, it is called empty. Unlike std::function, invoking an empty std::copyable_function results in undefined behavior.

std::copyable_functions supports every possible combination of cv-qualifiers (not including volatile), ref-qualifiers, and noexcept-specifiers provided in its template parameter. These qualifiers and specifier (if any) are added to its operator().

std::copyable_function satisfies the requirements of CopyConstructible and CopyAssignable.

[edit] Member types

Type	Definition
result_type	R

[edit] Member functions

(constructor)	constructs a new std::copyable_function object (public member function) [edit]
(destructor)	destroys a std::copyable_function object (public member function) [edit]
operator=	replaces or destroys the target (public member function) [edit]
swap	swaps the targets of two std::copyable_function objects (public member function) [edit]
operator bool	checks if the std::copyable_function has a target (public member function) [edit]
operator()	invokes the target (public member function) [edit]

[edit] Non-member functions

[edit] Notes

Implementations may store a callable object of small size within the std::copyable_function object. Such small object optimization is effectively required for function pointers and std::reference_wrapper specializations, and can only be applied to types T for which std::is_nothrow_move_constructible_v<T> is true.

Feature-test macro	Value	Std	Feature
__cpp_lib_copyable_function	202306L	(C++26)	std::copyable_function

[edit] Example

[edit] See also

| | copyable wrapper of any copy constructible callable object (class template) [edit] | | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | | move-only wrapper of any callable object that supports qualifiers in a given call signature (class template) [edit] | | | non-owning wrapper of any callable object (class template) [edit] |