【c++11关键字】decltype

/*
 * c++11关键字
 * decltype
 * 小鱼号的代码日志
*/
#include <QCoreApplication>
#include <iostream>
using namespace  std;
struct st
{
    double x;
};
template<typename T,typename U>
auto add(T m,U n) ->decltype(m+n)
{
    return m+n;
}
int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    const st* s = new st{0};
    auto aa = s->x;
    decltype(s->x) y = 0.2;  //double
    decltype((s->x)) z = y;  //double &
    auto& cc = y;
    cout << aa << " "<< y << " " << z << endl;
    y = 0.3;
    cout << y << " " << z << endl;
    auto g = add(1,0.3);
    cout << g << endl;
    return a.exec();
}