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std::copyable_function - cppreference.com

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Defined in header <functional>

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.

Member types

Type Definition
result_type R

Member functions

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

Non-member functions

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

Example

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]