Help on Overloading operators.

[ragecoder]

So I have just been teaching myself C++ for a while now and I seem to have found myself stuck in a rut of code so to say. What I need help under standing is what the purpose is, and how the "&" in the open parenthesis affects what this here snippet of code does. Whenever I see it my brain just assumes address of. Thanks in advance fellow humans, sorry for anything that may have slipped my mind and made my question unclear.

  bool operator == (const ClassType& compareTo)
{
   //comparison code here, return true if equal else false.
}


//actual app
#include <iostream>

class Date
{
private:
    int Day, Month, Year;

public:

    //Constructor that initializes the object to a day, month and year
    Date(int InputDay, int InputMonth, int InputYear)
    : Day(InputDay), Month(InputMonth), Year(InputYear) {};

    bool operator == (const Date& compareTo)
    {
        return((Day == compareTo.Day)
        && (Month == compareTo.Month)
        && (Year == compareTo.Year));
    }

    bool operator != (const Date &compareTo)
    {
        return !(this->operator==(compareTo));
    }

    void DisplayDate()
    {
    std::cout << Day << " / " << Month << " / " << Year << std::endl;
    }
};

int main()
{
    Date Holiday1 (25,12,2011);
    Date Holiday2 (31,12,2011);

    std::cout << "Holiday 1 is: ";
    Holiday1.DisplayDate();
    std::cout << "Holiday 2 is: ";
    Holiday2.DisplayDate();

    if(Holiday1 == Holiday2)
    {
        std::cout << "Equality operator: The two are on the same day" << std::endl;
    }
    else
    {
        std::cout << "Equality operator: The two are on diffrent days" << std::endl;
    }
    if(Holiday1 != Holiday2)
    {
        std::cout << "Inequality operator: The two are on diffrent days" << std::endl;
    }
    else
    {
        std::cout << "Inequality operator: The two are on the smae day" << std::endl;
    }

    return 0;
}

Edit: On a side note whether it's there or not it seems to compile in my program just fine as well as run.

[nvrmnd]

What I need help under standing is what the purpose is, and how the "&" in the open parenthesis affects what this here snippet of code does

For user defined types, it's always better to pass it by reference to const instead of by copy, like :

bool operator ( Date compareTo ) { } // pass a Date by copy (slow)

Since with the above code, you are copying a whole Date object every time you call that function
and that may slow down ur program.

If you pass by reference it will only copy a reference to the object passed to the function
(it's something like a pointer, i dont know the details) and it takes only a few bytes

http://www.learncpp.com/cpp-tutorial/73-passing-arguments-by-reference/

[ragecoder]

Hey thanks I don't know why that didn't come to mind when I did this, cheers and may the bytes be with you.

[KyiannaJones]

Here is an example that should be helpful.

http://www.cprogramming.com/tutorial/operator_overloading.html