std::string 拼接字符串

#include <iostream>
#include <string>
#include <sstream>
using namespace std;


int main()
{
    string a = "123";

    stringstream b;
    b << 123 << "456" << 789 << "-=-=";
    
    a += b.str();

    // 123123456789-=-=
    cout << a << endl;

    return 1;
}