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

NAME
     std::function_ref - std::function_ref

Synopsis
	Defined in header <functional>
	template< class... >			       (1) (since C++26)
	class function_ref; // not defined
	template< class R, class... Args >

	class function_ref<R(Args...)>;
	template< class R, class... Args >
	class function_ref<R(Args...) noexcept>;       (2) (since C++26)
	template< class R, class... Args >
	class function_ref<R(Args...) const>;
	template< class R, class... Args >

	class function_ref<R(Args...) const noexcept>;

	Class  template  std::function_ref  is	a  non-owning  function wrapper.
     std::function_ref
	objects can store and invoke reference to Callable target  -  functions,
     lambda
	expressions, bind expressions, or other function objects, but not point-
     ers to member
	functions  and	pointers  to member objects. std::nontype can be used to
     construct
	std::function_ref by passing function pointers, pointers to member func-
     tions, and
	pointers to member objects.

	std::function_refs supports every possible combination of cv-qualifiers,
     and
	noexcept-specifiers not including volatile provided in its template  pa-
     rameter.

	Every  specialization  of  std::function_ref is a TriviallyCopyable type
     that satisfies
	copyable.

Member objects
	Member name	       Definition
			       an object that has an unspecified  TriviallyCopy-
     able type
			       BoundEntityType,  that  satisfies copyable and is
     capable of
	bound-entity (private) storing a pointer to object value or  pointer  to
     function
			       value
			       (exposition-only member object*)
			       a  pointer  to function of type R(*)(BoundEntity-
     Type,
			       Args&&...) noexcept(/*noex*/) where  /*noex*/  is
     true if
	thunk-ptr (private)    noexcept is present in function signature as part
     of the
			       template parameter of std::function_ref
			       (exposition-only member object*)

Member functions
	constructor   constructs a new function_ref object
	(C++26)       (public member function)
	operator=     assigns a function_ref
	(C++26)       (public member function)
	operator()    invokes the stored thunk of a function_ref
	(C++26)       (public member function)

	Deduction guides

Notes
	  Feature-test macro	Value	 Std	    Feature
	__cpp_lib_function_ref 202306L (C++26) std::function_ref

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)
	copyable_function   refinement	of  std::move_only_function  that  wraps
     callable object
	(C++26) 	   of any copy constructible type
			   (class template)
	move_only_function  wraps  callable  object  of  any type with specified
     function call
	(C++23) 	   signature
			   (class template)
	nontype 	   value construction tag
	nontype_t	   (tag)
	(C++26)

Category:
	  * Todo with reason

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