overloading operators<<>>, virtual functions

[fyodor]

All that i have to do is write class Vector2D and then implement some methods:

class Vector2D {
	double x,y;
	virtual double GetLength();
	virtual void Put(ostream& out);
	virtual void Get(istream& in);
	friend operator<<(ostream&, Vector2D&)
	friend operator>>(istream&, Vector2D&)
}

I don't know what means this ostream&...istream&...Can somebody explain me how to do this?

[Albatross]

http://cplusplus.com/doc/tutorial/pointers/
http://cplusplus.com/doc/tutorial/functions2/

Operators:
http://msdn.microsoft.com/en-us/library/5tk49fh2(v=VS.80).aspx

-Albatross

[moorecm]

Something like this?

ostream & operator<<( ostream & out, const Vector2D & obj ) {
    out << "(" << obj.x << ", " << obj.y << ")";  // send individual values to out
    return out;                                   // return ostream so that calls may be chained (<< a << b << c)
}

[Bazzy]

Those aren't pointers but references ( http://www.cplusplus.com/doc/tutorial/functions2/ )
Streams must be passed by reference ( or pointer ) since they aren't copyable

[Albatross]

Those aren't pointers but references

Then why does one find the reference operator under "pointers"?

-Albatross

[Bazzy]

Nope, they may be implemented as pointers but that is not how they are exposed to the C++ programmer

[Albatross]

Mistype, I got my terminology mixed up. I meant what you see above now.

-Albatross

[fyodor]

my code now looks like that:
.h:

#include <iostream>
#include <string>

using namespace std;

class Vector
{
	protected:
		int x, y;
	public:
		Vector();				
		friend ostream& operator<<(ostream& out, Vector vector);
		~Vector();
};

.cpp:

#include <iostream>
#include "Przyklad.h"

using namespace std;

Vector::Vector():x(3), y(2)
{}

ostream& operator<<(ostream& out, Vector& vector)
{
	out<<"X: "<<vector.x<<endl<<"Y: "<<vector.y;
	return out;
}

Vector::~Vector()
{}

but this friend function can't acces x and y...what should i do?

[m4ster r0shi]

it doesn't work because it's not the same function ;)

the one in your class definition is:
ostream& operator<<(ostream& out, Vector vector); <- here you pass Vector

and the one you declare is:
ostream& operator<<(ostream& out, Vector& vector); <- here you pass Vector &

just add a '&' in the one in your class definition and it should be fine

[fyodor]

HAAAA!! it's working:D thank you...how stupid i'm!!

[fyodor]

Ehh...sorry, but i have one more question... how can I make functions Put(istream&) and Get(ostream&) ? i did something like that:
in declaration:

class Vector
{
	protected:
		int x, y;
	public:
		Vector();
		virtual void Get(istream& in);
		virtual void Put(ostream& out);
.
.
.

in definition:

void Vector::Get(istream& in)
{
	cout<<"X: ";
	in<<this->x;
	cout<<"Y: ";
	in>>this->y;
}
void Vector::Put(ostream& out)
{
	out<<"X : "<<this->x<<endl;
	out<<"Y : "<<this->y<<endl;
}

and it's not working... can't compile...

binary '<<' : no operator found which takes a left-hand operand of type 'std::istream' (or there is no acceptable conversion)

could be 'std::ostream &operator <<(std::ostream &,Vector &)'

can you help me one more time?

[m4ster r0shi]

your compiler is complaining about this:
in<<this->x;

it should be like this:
in>>this->x;

:P

also, since Get and Put are member functions, you don't have to use this to access the members, just write plain x and y.