function template
<functional>
std::ref
| reference (1) | template <class T> reference_wrapper<T> ref (T& elem) noexcept;
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| copy (2) | template <class T> reference_wrapper<T> ref (reference_wrapper<T>& x) noexcept;
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| move (3) | template <class T> void ref (const T&&) = delete; |
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Construct reference_wrapper
Parameters
- elem
- An lvalue reference, whose reference is stored in the object.
- x
- A reference_wrapper object, which is copied.
Return Value
A reference_wrapper object of the appropriate type to hold an element of type T.
Example
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// ref example
#include <iostream> // std::cout
#include <functional> // std::ref
int main () {
int foo (10);
auto bar = std::ref(foo);
++bar;
std::cout << foo << '\n';
return 0;
}
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Output:
Data races
The initialization version (1) does not access elem, but the returned object can be used to access or modify it.
The copying version (2) accesses its argument (x), returning an object that which can be used to access or modify its referred element.
Exception safety
No-throw guarantee: never throws exceptions.