Addition of complex numbers using classes - c++

Question

I am trying to add 2 complex numbers together, but i am getting the errors:
no operator "+" matches these operands
no operator "<<" matches these operands
#include <iostream>
using namespace std;
class complex
{
public:
double get_r() { return r; }
void set_r(double newr) { r=newr; }
double set_i() { return i; }
void set_i(double newi) { i = newi; }
private:
double r, i;
};
int main()
{
complex A, B;
A.set_r(1.0);
A.set_i(2.0);
B.set_r(3.0);
B.set_i(2.0);
complex sum = A+B;
cout << "summen er: " << sum << endl;
system("PAUSE");
return 0;
};
I'm very new to programming, but i can't see why it won't add these numbers together. What have I done wrong?

Answer 1

You must overload operators + and << (and each one in your need) for your defined classes. Note that operators are no more than specific functions with specific definition syntax (operator+, for example: C = A + B could be understood as C = A.sum(B)). Here a link about http://en.cppreference.com/w/cpp/language/operators

Answer 2

Operator + is defined for builtin types and for some types from the standard library. As complex is here a custom class, you must define all operators that should act on it.
operator + could be defined as:
class complex {
...
complex operator + (const complex& other) {
return complex(get_r() + other.get_r(), get_i() + other.get_i());
}
...
};
Beware that does allow neither A++ nor A-B. They would require (resp.) complex & operator ++() or complex operator - (const complex &).
For stream insertion, the first parameter is the stream itself, so you must define a friend operator with 2 parameters outside the class:
outstream& opererator << (outstream &out, const complex& val) {
// output it the way you want
return out;
}

Answer 3

Complex numbers are part of the C++ standard. Here is the example from http://en.cppreference.com/w/cpp/numeric/complex.
#include <iostream>
#include <iomanip>
#include <complex>
#include <cmath>
int main()
{
using namespace std::complex_literals;
std::cout << std::fixed << std::setprecision(1);
std::complex<double> z1 = 1i * 1i;
std::cout << "i * i = " << z1 << '\n';
std::complex<double> z2 = std::pow(1i, 2);
std::cout << "pow(i, 2) = " << z2 << '\n';
double PI = std::acos(-1);
std::complex<double> z3 = std::exp(1i * PI);
std::cout << "exp(i * pi) = " << z3 << '\n';
std::complex<double> z4 = 1. + 2i, z5 = 1. - 2i;
std::cout << "(1+2i)*(1-2i) = " << z4*z5 << '\n';
}
Trying to implement a class complex yourself would require you define addition, equality, and ostream. And you would only have 5% of a fully implemented class. Looking at the header itself will reveal how those that wrote the C++ standard library implemented the whole thing.

Answer 4

All the arithmetic operators like plus, minus, multiply or divide only work with pre defined data types, like int, char, float etc.
Now if you want to add something in a class, you have to use the fundamental aspect of OO programming that is operator overloading.
Here is how you can achieve it.
#include <iostream>
using namespace std;
class complex
{
float x, y;
public:
complex()
{
}
complex(float real, float img)
{
x = real;
y = img;
}
friend complex operator+(complex,complex);
void display(void);
};
complex operator+(complex c,complex d)
{
complex t;
t.x = d.x + c.x;
t.y = d.y + t.y;
return(t);
};
void complex::display(void)
{
cout << x << "+i" << y << endl;
}
int main()
{
complex c1, c2, c3;
c1 = complex(2.5, 3.5);
c2 = complex(1.5, 5.5);
c3 = c1 + c2;//c3=opra+(c1,c2)
cout << "C1:" << endl;
c1.display();
cout << "C2:" << endl;
c2.display();
cout << "C3:" << endl;
c3.display();
}