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std::function_ref

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< cpp‎ | utility‎ | functional
 
 
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(until C++17*)
(until C++17*)(until C++17*)(until C++17*)(until C++17*)
(until C++20*)
(until C++20*)
 
 
Defined in header <functional>
template< class... >
class function_ref; // not defined
(1) (since C++26)
template< class R, class... Args >

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

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

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 pointers 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 functions, 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 parameter.

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

Contents

[edit] Member objects

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

[edit] Member functions

constructs a new function_ref object
(public member function) [edit]
(C++26)
assigns a function_ref
(public member function) [edit]
invokes the stored thunk of a function_ref
(public member function) [edit]

[edit] Deduction guides

[edit] Notes

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

[edit] Example

[edit] See also

(C++11)
wraps callable object of any copy constructible type with specified function call signature
(class template) [edit]
refinement of std::move_only_function that wraps callable object of any copy constructible type
(class template) [edit]
wraps callable object of any type with specified function call signature
(class template) [edit]
value construction tag
(tag)[edit]