Question

1. Write the class Trace with a copy constructor and an assignment operator, printing a short message in each. Use this class to demonstrate

   1. the difference between initialization

Trace t("abc");

Trace u = t;

and assignment.

Trace t("abc");

Trace u("xyz");

u = t;

2. the fact that all constructed objects are automatically destroyed.

3. the fact that the copy constructor is invoked if an object is passed by value to a

function.

4. the fact that the copy constructor is not invoked when a parameter is passed

by reference.

5. the fact that the copy constructor is used to copy a return value to the caller.

Programing language: C++

Requirement: provide answer to cover 1-5.

Answer 1

Code:

#include<iostream> 
#include<string> 
using namespace std; 
class Trace 
{ 
private: 
    string str;
public: 
    Trace(string s)  //parameterised constructor to initialize variable
    { 
        str=s;
    } 
  
    // Copy constructor 
    Trace(const Trace &p2){  // this will copies value of one class object1 to 
        str = p2.str;        // another class object
    } 
    string getstr(){  //this method is use to print value of class object
        return str; 
    } 
}; 
int main() 
{ 
    Trace p1("Hello"); // Parameterised(Normal) constructor is called here 
    Trace p2 = p1; // Copy constructor is called here 
   
    // Let us access values assigned by constructors and copied constructor 
    cout << "For object p1 : " << p1.getstr()<<endl;  //this will print value of p1 that is created by calling constructor
    //this will print value of p2 that is created by copy constructor
    cout << "For object p2 genrated by copy constructor : " << p2.getstr()<<endl; 
    
    Trace p3("Hello1");
    p1=p3;       //assignment of object 
    
    cout << "For object p3 : " << p3.getstr()<<endl;   //this will print value of p3,created by calling constructor
    //this will print value of p3,created by calling constructor after assignment
    cout << "For object p1 after assignment of object p3 : " << p1.getstr();  
    return 0; 
}

Output: