Error while adding Complex numbers - c++

Question

In below program I am getting 2 errors at below lines.
r = sum(p,q); //Function sum should have a prototype.
r = sum(p,q); //Cannot convert int to complex
Kindly advise the changes in the code.
Note: I have to do the code by passing objects of complex class to add and also the addition should return a complex number.
#include<iostream.h>
#include<conio.h>
class Complex
{
private:
int real;
int imag;
public:
void getNo()
{
cout<<"Enter real part : "<<endl;
cin>>real;
cout<<"Enter imaginary part : "<<endl;
cin>>imag;
}
void showNo()
{
cout<<real<<"+"<<imag<<"i";
}
Complex sum(Complex, Complex);
};
Complex Complex :: sum(Complex c1, Complex c2)
{
Complex a;
a.real = c1.real + c2.real;
a.imag = c1.imag + c2.imag;
return a;
}
void main()
{
clrscr();
Complex p,q,r,s;
p.getNo();
q.getNo();
cout<<endl<<"First complex number is : ";
p.showNo();
cout<<endl<<"Second complex number is : ";
q.showNo();
r = sum(p,q);
cout<<"Addtion of the complex no is : ";
r.showNo();
getch();
}

Answer 1

For your purpose the "sum" function should not be in the "Complex" class. Here a bit changed code:
#include <iostream>
#include <conio.h>
using namespace std;
class Complex
{
public:
int real;
int imag;
void getNo ()
{
cout << "Enter real part : " << endl;
cin >> real;
cout << "Enter imaginary part : " << endl;
cin >> imag;
}
void showNo ()
{
cout << real << "+" << imag << "i";
}
};
Complex sum (Complex c1, Complex c2);
int main ()
{
//clrscr ();
Complex p, q, r, s;
p.getNo ();
q.getNo ();
cout << endl << "First complex number is : ";
p.showNo ();
cout << endl << "Second complex number is : ";
q.showNo ();
r = sum (p, q);
cout << endl << "Addtion of the complex no is : ";
r.showNo ();
getch ();
}
Complex sum (Complex c1, Complex c2)
{
Complex
a;
a.real = c1.real + c2.real;
a.imag = c1.imag + c2.imag;
return a;
}
Edit
Functions in class require an instance (object) of class.
Simply you CAN do this:
p.getNo();
t.sum();
myComplexNum.getReal();
But in your code you are trying to do this which you CAN NOT:
a = getNo();
b = sum();
getReal();
Additionally you CAN make the function static like other answer.
static functions and variables does not require an instance. Calling:
// We have 1 Box named b
Box b;
b.setHeight(5);
b.setWidth(3);
b.setDepth(3);
//ClassName::StaticVariable;
int c1 = Box::count; // returns 1
//ClassName::StaticFunction(Parameters);
int c2 = Box::getCount(); // returns 1

Answer 2

When you declare a function (a method) in a class, this method can be called on a instance of this class (a object).
In the given code the function Complex sum (Complex c1, Complex c2); should be called on an object of type Complex.
But as the function doesn't change anything inside the object, it rather creates a new object and returns it, you should better declare a static method.
static Complex sum(Complex, Complex);
in this case you can call the function without an existing Complex object.
The syntax is the following :
r = Complex::sum(a, b);