Error accessing private data in a class

[mucker2b]

I'm new to programming and I'm having a problem with an assignment I was given to add complex numbers.
When I run the code it always points to these sections of code stating that a and b are private. I am guessng it is because am usng the complex type within the complex class.

Could somebody give me an idea as to where I'm going wrong.

Thanks

class complex
{
   float a, b;

   public:
      void input(float real, float img);
      void display(complex c);
      complex sum(complex, complex);
};

complex::complex sum(complex c1, complex c2)
   {
      complex c3;
      c3.a = c1.a + c2.a;
      c3.b = c1.b + c2.b;
      return (c3);
   }

[guestgulkan]

complex::complex sum(complex c1, complex c2) //ERROR ON THIS LINE
   {
      complex c3;
      c3.a = c1.a + c2.a;
      c3.b = c1.b + c2.b;
      return (c3);
   }

You mean complex complex::sum(complex c1, complex c2)
Notice the position of the ::


By the way, a sum function written as a member function like this would be awkward to use.

[mahlerfive]

The above poster is correct, if you want to add two objects together like this you should overload the addition operator. Try googling "c++ overload operator". After overloading the add operator you can do stuff like:

// c1 and c2 are complex
complex c3 = c1 + c2;

instead of:

complex c3 = c1.sum( c1, c2 );

At the very least, if you don't overload the addition operator, make the function static.

[Xilas]

I agree, overloading the + operator is way better and easier to use afterward. A few months ago I made, for fun, a class named complex.h. It was getting right to the point of overloading operators. I just wanted to remember such things hehe, so anyway you wanna see it ? I know it is quite not good for your learnings... :D

[Zaita]

The actual problem you are experiencing is that .a and .b are private members. Therefore you cannot access the .a or .b of the parameters passed in.

You should make a function called.

float getA() { return a; }
float getB() { return b; }

then use
c3.a = c1.getA() + c2.getA();

Welcome to Encapsulation. 1 of the 3 Fundamentals of Object-Orientated Development

[jsmith]

That should be ok, though. sum() is a member function of complex, and should therefore be able to access the private data members of its own instance or of any other instance of complex passed in.

Anyway, I tend to follow the rule of making non-public things protected rather than private unless there is a strong reason why derived classes should not have direct access to the members.