问tuple/tie的返回值优化

EN

Test duo output, non_reference tuple
Default constructor invoked
Parameter constructor invoked
Copy constructor invoked
Move Assignment operator invoked
100

#include <iostream>
#include <tuple>

class A
{
public:
     int value;
     A() : value(-1)
     {
         std::cout << "Default constructor invoked" << std::endl;
     }

     explicit A(const int v) : value(v)
     {
         std::cout << "Parameter constructor invoked" << std::endl;
     }

     A(const A& rhs)
     {
         value = rhs.value;
         std::cout << "Copy constructor invoked" << std::endl;
     }

     A(const A&& rhs)
     {
         value = rhs.value;
         std::cout << "Move constructor invoked" << std::endl;
     }

     A& operator=(const A& rhs)
     {
         value = rhs.value;
         std::cout << "Assignment operator invoked" << std::endl;
         return *this;
     }

     A& operator=(const A&& rhs)
     {
         value = rhs.value;
         std::cout << "Move Assignment operator invoked" << std::endl;
         return *this;
     }
 };

 std::tuple<A, int> return_two_non_reference_tuple()
 {
     A tmp(100);

     return std::make_tuple(tmp, 99);
 }

 int main(int argc, char* argv[])
 {

      std::cout << "Test duo output, non_reference tuple" << std::endl;    
      A t3;
      int v1;
      std::tie(t3, v1) = return_two_non_reference_tuple();
      std::cout << t3.value << std::endl << std::endl;

      system("pause");
      return 0;
}