#include<iostream>
using namespace std;
class Complex
{
    private:
     double real;
     double imag;
    public:
     Complex(double r=0,double i=0)
     {
         cout<<" constructing···\n";
      real=r;
      imag=i;
     }
     Complex(Complex &c)
     {
         cout<<"copy constructing···\n";
      real=c.real;
      imag=c.imag;
     }
     ~Complex()
     {
      cout<<"destructing···\n";
     }
     double realcomplex()
     {
      return real;
     }
     double imagcomplex()
     {
      return imag;
     }
};
void display(Complex p)
{
     cout<<"The real of complex="<<p.realcomplex()<<endl;
     cout<<"The imag of complex="<<p.imagcomplex()<<endl;
}
int main()
{
     Complex a(1.1,2.2);
     Complex b;
     Complex c(a);
     display(a);
     display(b);
     display(c);
 return 0;
}

constructing···
constructing···
copy constructing···
copy constructing···
The real of complex=1.1
The imag of complex=2.2
destructing···
copy constructing···
The real of complex=0
The imag of complex=0
destructing···
copy constructing···
The real of complex=1.1
The imag of complex=2.2
destructing···
destructing···
destructing···
destructing···

Process returned 0 (0x0) execution time : 0.891 s
Press any key to continue.

该程序中的拷贝构造函数在不同的时刻被调用了三次，为什么会成这种情况，我主要想问拷贝构造函数什么时候被调用？