a sample question....

[ahura24]

hi everybody . i read in CookBook herbert schildt 4 place a copy constructor is call
1) cl a(b)
2) cl a = b
3) f1( a )
4) a = f2()

now my question is :

#include <iostream>
using namespace std;

class ahura {
public:
	ahura()
	{ 
		cout << "ahura()\n"; 
	}

	ahura(const ahura &o)
	{ 
		cout << "ahura(ahura &o)\n"; 
	}

	~ahura()
	{ 
		cout << "~ahura()\n"; 
	}

	ahura &operator =(const ahura &o)
	{
		cout << "operator =\n"; 
		return *this;
	}
};

void f(ahura a)
{ }

ahura f2()
{ return ahura(); }

void main()
{
	ahura a;
	a = f2(); //why doesnt call copy constructor?!!!instead call operator = ?!!!!!
}

[Peter87]

A constructor is used to initialize an object when the object is created. If you do ahura a; a is created and the default constructor is used. You never call the constructor on an already existing object so a = f2(); can't use a constructor. Instead it uses operator=.