How to define two functions with the same name and parameters, if one of them has a reference?

Question

I have code:

int SomeClass::sum(int x)
{
    return x+=x;
}

int SomeClass::sum(int & x)
{
    return x+=x;
}

....

int num = 0;
int result = sum(num);

that not work. How I can use both functions and indicate which of them I want to use when I сall them?

Answer 1

You can provide two different overloads taking int& and const int& , which might somehow meet your needs...

But the whole code is a bit strange... in the function that takes the argument by value you are modifying it ( += ), when it probably makes sense to only read it return x+x; . In the overload that takes the reference, you are both modifying the argument and returning the new value. That is a bit strange.

Other than that, sum is a horrible name for a function that multiplies by 2.

Answer 2

You can not have such functions in C++ . They will have to be named differently for instance sumByCopy and sumByRef . How would you expect the compiler to decide which one are you referring to at each point?

Answer 3

You can overload in this way, it will compile OK if you do not call any of them directly. However, it will cause ambiguity when you call sum(num) . Therefore, it is no sense to provide those overloads of a function since we cannot directly call none of them. This kind of overloads is useless and violates good practice.