double转换为string 及代理构造函数

#include <iostream>
/* #include <string>
#include <sstream> */
class C
{
int x = 0;  
public:
    //1.
    C(int x):x{x}{
        std::cout<<"C(" + std::to_string(x) + ")"<<"
";
    }

    //2.
    C(double d):C(static_cast<int>(d)){    
        std::string s = std::to_string(d);
        std::cout<< "C(" + s.erase(s.find_last_not_of('0')+1) + ")" <<std::endl;
        /* std::ostringstream oss; 
        oss<<d; 
        std::cout<< "C(" + oss.str() + ")" <<std::endl; */
    }
    
    //3.
    C():C(3.8){
        std::cout<<"C()"<<std::endl;
    }    
};
int main()
{
    C c3;
    C c2{2.2};
    C c1{1};
    return 0;
}