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std::copyable_function(3)      C++ Standard Libary     std::copyable_function(3)

NAME
     std::copyable_function - std::copyable_function

Synopsis
	Defined in header <functional>
	template< class... >				       (1) (since C++26)
	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>;       (2) (since C++26)
	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  Copy-
     Constructible
	Callable  target  a  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_func-
     tion. 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-quali-
     fiers,
	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
	Type	    Definition
	result_type R

Member functions
	constructor   constructs a new std::copyable_function object
	(C++26)       (public member function)
	destructor    destroys a std::copyable_function object
	(C++26)       (public member function)
	operator=     replaces or destroys the target
	(C++26)       (public member function)
	swap	      swaps the targets of two std::copyable_function objects
	(C++26)       (public member function)
	operator bool checks if the std::copyable_function has a target
	(C++26)       (public member function)
	operator()    invokes the target
	(C++26)       (public member function)

Non-member functions
	swap(std::copyable_function) overloads the std::swap algorithm
	(C++26) 		     (function)
	operator==		       compares  a  std::copyable_function  with
     nullptr
	(C++26) 		     (function)

Notes
	Implementations may store a callable object of small size within the
	std::copyable_function object. Such small object optimization is  effec-
     tively
	required  for  function  pointers and std::reference_wrapper specializa-
     tions, and can
	only  be  applied  to  types  T  for   which   std::is_nothrow_move_con-
     structible_v<T> is
	true.

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

Example
	 This section is incomplete
	 Reason: example

See also
	function	    wraps callable object of any copy constructible type
     with
	(C++11) 	   specified function call signature
			   (class template)
	move_only_function wraps callable object  of  any  type  with  specified
     function call
	(C++23) 	   signature
			   (class template)

Category:
	  * Todo with reason

http://cppreference.com 	   2024.06.10	       std::copyable_function(3)
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