what does "&" means in operator overloading

Question

The following is a sample code for operator overloading. what does the "&" means in the syntax

complx operator+(const complx&) const; ?

#include <iostream>
using namespace std;
class complx
{
      double real,
             imag;
public:
      complx( double real = 0., double imag = 0.); // constructor
      complx operator+(const complx&) const;       // operator+()
};

// define constructor
complx::complx( double r, double i )
{
      real = r; imag = i;
}

// define overloaded + (plus) operator
complx complx::operator+ (const complx& c) const
{
      complx result;
      result.real = (this->real + c.real);
      result.imag = (this->imag + c.imag);
      return result;

}

int main()
{
      complx x(4,4);
      complx y(6,6);
      complx z = x + y; // calls complx::operator+()
}

That's a reference. Any [decent introductory C++ book](http://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list) should cover this. — R. Martinho Fernandes, Apr 22 '13 at 09:24
Wikipedia also has decent information for beginners: [operators wiki](http://en.wikipedia.org/wiki/Operators_in_C_and_C%2B%2B#Member_and_pointer_operators) — Dariusz, Apr 22 '13 at 09:26

score 2 · Answer 1 · answered Apr 22 '13 at 09:24

2

That means that you are passing a reference to a variable, instead of a copy of it.

answered Apr 22 '13 at 09:24

SingerOfTheFall

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score 2 · Answer 2 · answered Apr 22 '13 at 09:37

(const complx&)

You are passing the value by reference.
Reference is just an alias to the original object.
Extra copy operation is avoided here. If you have used 'pass by value' like : (const complex ), then the copy constructor of complex is invoked for formal parameters.

Hope this helps to some extend.

score 0 · Answer 3 · answered Apr 22 '13 at 09:32

That is called as pass by reference and it is not specific to operator overloading. It is one of the ways you would pass arguments to a function [ 1.Pass by Copy, 2.Pass by address, 3.Pass by Reference ]. With C you make use of pointers when you want your original argument value to be modified when you modify it within a function. But Cpp also provides pass by reference, the name appended with & acts like an alternate name to the passed argument. [and also saves you from all that dereferencing and stuff associated with pointers]

what does "&" means in operator overloading

3 Answers3