Function templates ref and cref are helper functions that generate an object of type std::reference_wrapper, using template argument deduction to determine the template argument of the result.
T may be an incomplete type.
2) t
5) t
3,6) rvalue reference wrapper is deleted.
[edit] Example#include <functional>
#include <iostream>
void f(int& n1, int& n2, const int& n3)
{
std::cout << "In function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
++n1; // increments the copy of n1 stored in the function object
++n2; // increments the main()'s n2
// ++n3; // compile error
}
int main()
{
int n1 = 1, n2 = 2, n3 = 3;
std::function<void()> bound_f = std::bind(f, n1, std::ref(n2), std::cref(n3));
n1 = 10;
n2 = 11;
n3 = 12;
std::cout << "Before function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
bound_f();
std::cout << "After function: " << n1 << ' ' << n2 << ' ' << n3 << '\n';
}
Output:
Before function: 10 11 12 In function: 1 11 12 After function: 10 12 12[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 3146 C++11 unwrapping overloads sometimes led to error made always valid [edit] See alsoRetroSearch is an open source project built by @garambo | Open a GitHub Issue
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