Copy Constructor in c++ not working as expected - c++

Question

I was trying to make a Complex class which would represent the Complex numbers in c++ but I have encountered an error. The copy constructor seems to be the problem but I am not sure as to what is wrong or why it is wrong. The / operator works well as I return a reference to an object of Complex class. but the * operator does not works when I return an object of Complex class. Please explain this behaviour,
edit: I have used the new operator and a custom copy constructor as it was a requirement of my school to dynamically allocate memory.
here is my code.
#include <iostream>
using namespace std;
class Complex
{
public:
double r, i;
Complex() : r(0), i(0) {}
Complex(int r, int i)
{
this->r = double(r);
this->i = double(i);
}
Complex(double r, int i)
{
this->r = r;
this->i = double(i);
}
Complex(int r, double i)
{
this->r = double(r);
this->i = i;
}
Complex(double r, double i)
{
this->r = r;
this->i = i;
}
Complex(Complex &c)
{
cout<<"cpy constructor called"<<endl;
r = c.r;
i = c.i;
}
void operator()(float r, float i)
{
this->r = r;
this->i = i;
}
void operator()(int r, int i)
{
this->r = r;
this->i = i;
}
Complex operator+(Complex &c)
{
Complex *c1 = new Complex(r + c.r, i + c.i);
return *c1;
}
Complex operator-(Complex &c)
{
Complex *c1 = new Complex(r - c.r, i - c.i);
return *c1;
}
Complex operator*(Complex &c)
{
Complex *c1 = new Complex(
r * c.r + (-1) * (i * c.i),
r * c.i + i * c.r);
return *c1;
}
Complex& operator/(Complex &c)
{
float dem;
Complex num;
num = (*this) * * (new Complex(c.r,-c.i));
dem = c.r*c.r + (c.i*c.i);
Complex *c1 = new Complex(num.r/dem,num.i/dem);
return *c1;
}
operator string()
{
string temp, s;
temp = to_string(r);
while (true)
{
if (temp[temp.length() - 1] == '0')
{
temp.pop_back();
}
else
break;
}
if (temp[temp.length() - 1] == '.')
temp.pop_back();
s += temp;
if (i >= 0)
{
s += '+';
}
temp = to_string(i);
while (true)
{
if (temp[temp.length() - 1] == '0')
{
temp.pop_back();
}
else
break;
}
if (temp[temp.length() - 1] == '.')
temp.pop_back();
s += temp;
s += 'i';
return s;
}
friend ostream &operator<<(ostream &out, Complex c);
};
ostream& operator<<(ostream &out, Complex c)
{
out << string(c);
return out;
}
int main()
{
Complex c(5, 5);
Complex d(5,5);
cout << c/d <<endl;
cout<< c*d <<endl;
}
and this is the error I encounter after this
test.cpp: In function 'int main()':
test.cpp:123:13: error: invalid initialization of non-const reference of type 'Complex&' from an rvalue of type 'Complex'
cout<< c*d <<endl;
~^~
test.cpp:31:5: note: initializing argument 1 of 'Complex::Complex(Complex&)'
Complex(Complex &c)
^~~~~~~
test.cpp:111:10: note: initializing argument 2 of 'std::ostream& operator<<(std::ostream&, Complex)'
ostream& operator<<(ostream &out, Complex c)
This is the image to the error

Answer 1

Repeat the pattern of the code below for your other operators. Note the operator takes the parameter by const ref and returns the result by value:
Complex operator+(Complex const &c)
{
return Complex(r + c.r, i + c.i);
}
The copy constructor should also be changed to take it's parameter by const ref ie
Complex(Complex const &c)
{
r = c.r;
i = c.i;
}

Answer 2

The minimal fix isComplex(Complex &c) -> Complex(const Complex &c)
But then there will remain leaks due to the inappropriate usage of new there, after some cleanup:
#include <iostream>
using namespace std;
class Complex
{
public:
double r, i;
Complex(double r, double i) : r(r), i(i) {}
Complex operator+(Complex c)
{
return Complex(r + c.r, i + c.i);
}
Complex operator-(Complex c)
{
return Complex(r - c.r, i - c.i);
}
Complex operator*(Complex c)
{
return Complex(
r * c.r + (-1) * (i * c.i),
r * c.i + i * c.r);
}
Complex operator/(Complex c)
{
auto num = Complex (*this) * Complex(c.r,-c.i);
auto dem = c.r*c.r + (c.i*c.i);
return Complex(num.r/dem,num.i/dem);
}
operator string()
{
string temp, s;
temp = to_string(r);
while (!temp.empty() && temp.back() == '0')
temp.pop_back();
if (!temp.empty() && temp.back() == '.')
temp.pop_back();
s += temp;
if (i >= 0)
{
s += '+';
}
temp = to_string(i);
while (!temp.empty() && temp.back() == '0')
temp.pop_back();
if (!temp.empty() && temp.back() == '.')
temp.pop_back();
s += temp;
s += 'i';
return s;
}
friend ostream &operator<<(ostream &out, Complex c);
};
ostream& operator<<(ostream &out, Complex c)
{
out << string(c);
return out;
}
int main()
{
Complex c(5, 5);
Complex d(5,5);
cout << c/d <<endl;
cout<< c*d <<endl;
}

Answer 3

The big problem is lack of const on your references and members. The second problem is not using =default. The third problem is too many overloads. Forth, your new use is wrong. operstor() are all wrong. The last problem is your operator strategy. And don't use namespace std;.
struct Complex
Complex is both default public and basically an aggregate. I'd use struct
{
double r=0
double i=0;
you can do default initialization in C++ now.
Complex()=default;
now this ctor is auto-written, because we initialized the members at declaration. DRY is "don't repeat yourself"; when easy, don't repeat member names.
Complex(double r_in, double i_in):r(r_in),i(i_in){}
ctors should construct, not assign, members.
Drop the other 2 arg ctors. Callers can convert.
Complex(Complex const&c)=default;
const here, and let the compiler write a member-wise copy with =default; DRY.
Complex(Complex &&c)=default;
Complex& operator=(Complex const&c)=default;
Complex& operator=(Complex &&c)=default;
also assignment and moves
Now other operators...
Complex& operator+=(Complex const& o)&{
implement a+=b before +.
r+=o.r;
i+=o.i;
return *this;
}
here we repeat member names; it isn't easy to avoid.
Do the same for -= and *=
Next,
friend Complex operator+(Complex lhs, Complex const& rhs){
lhs+=rhs;
return lhs;
}
this makes a non-member +. It makes a copy of its left hand argument by taking it by value, and a const reference to its right hand argument.
We then increment the left hand copy by the right, and return it.
This pattern chans wonderfully in 99% of situations;
Complex x=a+b+c
becomes
Complex x=a;
x+=b;
x+=c;
after accounting for moves and elision.
And you get a+=b; and a+b by writing only one member-wise operation.
Just don't use your operator(), they are nonsense.