std::copyable_function

template< class... >
class copyable_function; // not defined

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>;

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, ref-qualifiers, and noexcept-specifiers not including volatile 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

Member functions

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.

Example

See also