#include <iostream>
using namespace std;int main()
{int x = 0;decltype(x) y = 1;  //y -> intcout << y << endl;decltype(x + y) z = 2; //z -> intcout << z << endl;const int& i = x;decltype(i) j = y;  //j -> const int &
cout << j << endl;const decltype(z) *p = &z;  //*p -> const intdecltype(z) *pi = &z;       //*pi -> int, pi->int*decltype(pi) *pp = &pi;     //*pp -> int*, pp->int**
cout << pp << endl;         //打印结果：0x61fe80cout << *pp << endl;        //打印结果：0x61fe84cout << **pp << endl;       //打印结果：2return 0;
}

#include <iostream>
using namespace std;class Test
{
public:Test() {}public:static const int nNumber = 0;int x;
};int main()
{//类访问表达式decltype(Test::nNumber) c = 10;Test test;decltype(test.x) d = 20;cout << c << "," << d <<endl;//标识符表达式int y = 20;decltype(y) z = 30;return 0;
}

#include <iostream>using namespace std;class Test
{
public:Test() {}public:int m_nNum = -10;
};int Test_Int();             //纯右值
int& Test_Int_One();        //左值const int Test_Cint();      //纯右值
const int& Test_Cint_One(); //左值const Test Test_Class();    //纯右值int main()
{int x = 10;decltype(Test_Int()) a1 = x;        //a1->intcout << a1 << endl;decltype(Test_Cint_One()) a2 = x;   //a2->int&int y = a2;cout << y << endl;cout << a2 << endl;decltype(Test_Cint()) b1 = x;       //b1->const intb1 = 20;cout << b1 << endl;decltype(Test_Cint_One()) b2 = x;   //b2->const& int//b2 = 30;                            //error:b2只是一个只读引用，不可再为其赋值cout << b2 << endl;decltype(Test_Class()) c1 = Test();cout << c1.m_nNum << endl;return 0;
}

#include <iostream>using namespace std;class Test
{
public:Test() {}public:static const int nNum = -10;int x = 0;
};int main()
{const Test test = Test();decltype(test.x) a = 0;     //a->intdecltype((test.x)) b = a;   //b->const int&b = 10;                     //error:b为只读引用cout << b << endl;int m =0,n=0;decltype(m + n) c = 10;     //c->intdecltype(m += n) d = c;      //d ->int &return 0;
}