c++委托构造和继承构造

#include "iostream"

using namespace::std;

class AA
{
public:
    int m_a;
    int m_b;
    double m_c;
    AA(){};
    //有一个参数的构造函数，初始化m_c
    AA(double c)
    {
        m_c=c+3;//初始化m_c
        cout<<"AA(double c)"<<endl;
    }
    AA(int a,int b)
    {
        m_a=a+1;
        m_b=b+2;
        cout<<"AA(int a,int b)"<<endl;
    }
    //构造函数?
    AA(int a,int b,const string&str):AA(a,b)
    {
        cout<<"m_a="<<m_a<<",m_b="<<m_b<<",str="<<str<<endl;
    }
    //构造函数？
    AA(double const c,const string& str):AA(c)
    {
        cout<<"m_c="<<m_c<<",str="<<str<<endl;
    }
};
class BB :public AA//派生类
{
public:
    double m_c;
    using AA::AA;//使用基类的构造函数。
    //有三个参数的构造函数，调用A(a,b)初始化m_a和m_b，同时初始化m_c
    BB(int a,int b,double c):AA(a,b),m_c(c)
    {
        cout<<"BB(int a,int b,double c)"<<endl;
    }
    void show()
    {
        cout<<"m_a="<<m_a<<"，m_b="<<m_b<<",m_c="<<m_c<<endl;
    }
};


int main()
{
//    AA a1(10,20,"我是一只傻傻鸟。");
//    AA a2(3.8,"我有一只小小鸟。");
    //就使用基类有一个参数的构造函数，参数化m_a；
    BB b1(10);
    b1.show();

    //将使用基类有两个参数的构造函数，初始化m_a和m_b
    BB b2(10,20);
    b2.show();

    //将使用派生类有三个参数的构造函数，调用A(a,b)初始化m_a和m_b，通时初始化m_c
    BB b3(10,20,10.58);
    b3.show();
}

AA(double c)
m_a=8，m_b=0,m_c=1.22691e-311
AA(int a,int b)
m_a=11，m_b=22,m_c=0
AA(int a,int b)
BB(int a,int b,double c)
m_a=11，m_b=22,m_c=10.58