std::reference_converts_from_temporary
Defined in header <type_traits> |
||
|---|---|---|
template< class T, class U > struct reference_converts_from_temporary; |
(since C++23) |
If.
-
Tis a reference type, and - given the hypothetic function declared as
U makeval();, the variable definitionT ref = makeval();is well-formed and binds a temporary object toref,
provides the member constant value equal to true. Otherwise value is false.
If T is a reference type, both std::remove_reference_t<T> and U shall be complete types, cv void, or an arrays of unknown bound; otherwise the behavior is undefined.
If an instantiation of a template above depends, directly or indirectly, on an incomplete type, and that instantiation could yield a different result if that type were hypothetically completed, the behavior is undefined.
The behavior of a program that adds specializations for reference_converts_from_temporary or reference_converts_from_temporary_v is undefined.
Helper variable template
template< class T, class U >
inline constexpr reference_converts_from_temporary_v =
std::reference_converts_from_temporary<T, U>::value; |
(since C++23) |
Inherited from std::integral_constant
Member constants
|
value
[static]
|
true if T is a reference type, a U value can be bound to T in copy-initialization, and a temporary object would be bound to the reference, false otherwise (public static member constant) |
Member functions
|
operator bool
|
converts the object to bool, returns value (public member function) |
|
operator()
(C++14)
|
returns value (public member function) |
Member types
| Type | Definition |
|---|---|
value_type |
bool |
type |
std::integral_constant<bool, value> |
Notes
reference_converts_from_temporary can be used for rejecting some cases that always produce dangling references.
Example
#include <type_traits>
#include <iostream>
int main()
{
std::cout << std::boolalpha
<< std::reference_converts_from_temporary_v<int&&, int> << '\n'
<< std::reference_converts_from_temporary_v<const int&, int> << '\n'
<< std::reference_converts_from_temporary_v<int&&, int&&> << '\n'
<< std::reference_converts_from_temporary_v<const int&, int&&> << '\n'
<< std::reference_converts_from_temporary_v<int&&, long&&> << '\n';
<< std::reference_converts_from_temporary_v<int&&, long> << '\n';
}
Output:
true true false false true true
See also
|
(C++11)(C++20)
|
checks if a type can be converted to the other type (class template) |
|
(C++17)(C++23)
|
invokes any Callable object with given arguments and possibility to specify return type (since C++23) (function template) |
|
(C++11)
|
binds one or more arguments to a function object (function template) |
|
(C++17)
|
calls the provided functor with the arguments held by one or more variants (function template) |
constructs a new std::function instance (public member function of std::function<R(Args...)>) |
|
|
(C++23)
|
constructs a new std::move_only_function object (public member function of std::move_only_function<R(Args...) cv ref noexcept(noex)>) |
| constructs the task object (public member function of std::packaged_task<R(Args...)>) |
© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
https://en.cppreference.com/w/cpp/types/reference_converts_from_temporary
