Why two outcomes are different in the case of operator overloading? - c++

Question

I have this code of overloaded operator for vectors class, which is a class of vector of dimension 3:
class Vectors
{
//private:
// double* vector;
public:
double* vector;
Vectors(double*);
Vectors();
Vectors(const Vectors&);
~Vectors();
void print_vector();
};
Class Methods:
Constructors:
Vectors::Vectors(double* value)
{
this->vector = new double[3];
for (auto i = 0; i < 3; i++)
{
this->vector[i] = value[i];
}
}
Vectors::Vectors()
{
this->vector = new double[3];
for (auto i = 0; i < 3; i++)
{
this->vector[i] = 0.0;
}
}
Copy Constructors:
Vectors::Vectors(const Vectors& copy)
{
this->vector = new double[3];
for (auto i = 0; i < 3; i++)
{
this->vector[i] = copy.vector[i];
}
}
Destructor:
Vectors::~Vectors()
{
//cout << "desctructor called \n";
delete[] vector;
}
void Vectors::print_vector(){
for (int i=0; i<3 ;i++){
cout << this->vector[i];
cout << '\t';
}
cout << endl;
}
Overloaded Operator:
Vectors operator+(const Vectors& obj1,const Vectors& obj2)
{
Vectors *res = new Vectors;
for (int i = 0; i < 3; i++){
//cout << obj1.vector[i] << '\t' << obj2.vector[i] << '\t' << obj1.vector[i] + obj2.vector[i] << endl;
res->vector[i] = obj1.vector[i] + obj2.vector[i];
//cout << res->vector[i] << endl;
}
//res->print_vector();
return *res;
}
int main()
{
double a[3] = {3.5,4.10,5.30};
double b[3] = {7.0,8.0,9.0};
Vectors* A = new Vectors(a);
Vectors* B = new Vectors(b);
Vectors* C = new Vectors();
*C = *A+*B; // This does not work
(*A+*B).print_vector(); // This works
C->print_vector();
Vectors D = *A+*B; // This works
D.print_vector();
}
When creating a pointer to an object Vectors, I get different results when compared to creating direct objects.
Output is:
1st Output:
0 4.68558e-310 14.3
2nd Output:
10.5 12.1 14.3
3rd Output:
10.5 12.1 14.3

Answer 1

This version works, but I have still got memory leak using valgrind. Can somebody point out where?
#include <iostream>
using namespace std;
class Vectors
{
//private:
// double* vector;
public:
double* vector;
Vectors(double*);
Vectors();
Vectors(const Vectors&);
~Vectors();
void print_vector();
Vectors operator=(const Vectors&);
};
Vectors::Vectors(double* value)
{
this->vector = new double[3];
for (auto i = 0; i < 3; i++)
{
this->vector[i] = value[i];
}
}
Vectors::Vectors()
{
this->vector = new double[3];
for (auto i = 0; i < 3; i++)
{
this->vector[i] = 0.0;
}
}
Vectors::Vectors(const Vectors& copy)
{
this->vector = new double[3];
for (auto i = 0; i < 3; i++)
{
this->vector[i] = copy.vector[i];
}
//this->vector = (copy.vector);
}
Vectors::~Vectors()
{
//cout << "desctructor called \n";
delete[] vector;
}
void Vectors::print_vector(){
for (int i=0; i<3 ;i++){
cout << this->vector[i];
cout << '\t';
}
cout << endl;
}
Vectors Vectors::operator=(const Vectors& obj1)
{
this->vector = new double[3];
if (this != &obj1)
{
for (int i = 0; i < 3; i++) {
this->vector[i] = obj1.vector[i];
}
}
return *this;
}
Vectors operator+(const Vectors& obj1,const Vectors& obj2)
{
Vectors res;
for (int i = 0; i < 3; i++){
res.vector[i] = obj1.vector[i] + obj2.vector[i];
}
return res;
}
int main()
{
double a[3] = {3.5,4.10,5.30};
double b[3] = {7.0,8.0,9.0};
Vectors* A = new Vectors(a);
Vectors* B = new Vectors(b);
Vectors* C = new Vectors();
*C = *A+*B;
C->print_vector();
//(*A+*B).print_vector();
//cout << C->vector[1]<<endl;
//double a[3] = {3.5,4.10,5.30};
//double b[3] = {7.0,8.0,9.0};
//Vectors A(a), B(b);
Vectors D = *A+*B;
//Vectors C = A-B;
//Vectors C = A*B;
//Vectors C = 5*A;
//Vectors C = 5.5*A;
//Vectors C = A/B;
//Vectors C = 5/A;
//Vectors C = 5.5/A;
D.print_vector();
delete[] A;
delete[] B;
delete[] C;
}