Copy Constructor And Assignment Operator

#include <iostream>
using namespace std;

class A {
public: 
  A(){ cout << "default A() called" << endl;}

  A(const A& rhs){cout << "copy constructor called\n";}
  A& operator=(const A& rhs) { cout << "= operator called\n";}
};

void pass_by_reference_is_faster(A& obj) {}

//pass by value, forcing copy constructor to call to make a copy of A
void will_make_a_copy_with_copy_constructor(A obj) {}

void test_A()
{
  A a;
  A a2;
  cout << "before a2=a \n";

  a2 = a; //this will call operator=

  cout << "before A a3 = a2 \n";

  A a3 = a2; // this will call copy constructor;

             // why? faster, so we don't call A(), make all 
             // member variables uninitialized/default
             // , and THEN assign
             // INSTEAD, upon creation, we get all values ready
             // this will make a big difference if A is complex

  cout << endl;

  will_make_a_copy_with_copy_constructor(a);
  cout << endl;

  pass_by_reference_is_faster(a); //will not call copy constructor

}

int main()
{
  test_A();
}