A question of The List Container.

I have a question about the list class. The data consists of objects of the type intEntry

Here is my header file

Code:

class intEntry
{
public:
	intEntry(int v, int c = 1);
		// initalize the integer value and its count

	int getValue() const;
		// return value;

	int getCount() const;
		// return count
	
	void increment();
		// increment count

	friend bool operator< (const intEntry& lhs, const intEntry& rhs);
	friend bool operator== (const intEntry& lhs, const intEntry& rhs);
		// compate lhs and rhs using value

	friend ostream& operator<< (ostream& ostr, const intEntry& obj);
		// output obj in format "value value ... value" (const times)


private:
	int value;
		// integer value;

	int count;
		// number of occurrences of value

};

My question is what those codes for

Code:

friend bool operator< (const intEntry& lhs, const intEntry& rhs);
	friend bool operator== (const intEntry& lhs, const intEntry& rhs);
		// compate lhs and rhs using value

	friend ostream& operator<< (ostream& ostr, const intEntry& obj);
		// output obj in format "value value ... value" (const times)

Why do I need to put a "friend" at the first?
Also, what is "operator<" ?
and (const intEntry& lhs) means the address of lhs?

Last one, What is the operator== for?

Thanks for helping.

Originally Posted by joenching

Why do I need to put a "friend" at the first?

You need to do this because the member variables are private to the intEntry class. Putting "friend" in front of them means they have access to these private member variables so they can do their job.

Originally Posted by joenching

Also, what is "operator<" ?

It is an overloaded "less-than" operator for comparing items of the intEntry class, for example:

Code:

intEntry a, b;

if( a < b )  // Here the "operator<" is being used to compare a with b
{
    // Do something
}

Originally Posted by joenching

and (const intEntry& lhs) means the address of lhs?

It is a const-reference argument. Arguments are passed by copy as a default which means a copy of the passed in value is made for the function to work with. Passing by reference means that the actual object is passed into the function instead of a copy.

Originally Posted by joenching

Last one, What is the operator== for?

It is an overloaded equality operator for use in comparing items of the intEntry class:

Code:

intEntry a, b;
...
if( a == b )  // Here the "operator==" is used to test for equality
{
    // They are equal
}
else
{
    // They are not equal
}

Your questions have nothing to do with the list container...

Oh, it's because i have a list container question ahead

That's why i want to make sure myself undestand everything before i work in.