C++的string类

#include 
#include 

using namespace std;


int main()
{
    int n(20);
    cout << n << endl;
    string a = "dog";
    string b =a + ", cat";
    cout << b << endl;
    string c = a +  "dog" + "cat";
    cout << c << endl;
    //string d = "dog" + "cat"; //错误！！！
	return 0;
}

运行结果：

20
dog, cat
dogdogcat