overloading <<

Hi,
i'm new with c++, and this is my first overloading
in the last line of this .h file (marked), the compiler desagrees.
it says:

Code:

error C2143: syntax error : missing ';' before '&'
error C2433: 'ostream' : 'friend' not permitted on data declarations
error C4430: missing type specifier - int assumed. Note: C++ does not support default-int

now, when i add "std:stream&" instead of "ostream&, i get:

Code:

 error C2270: '<<' : modifiers not allowed on nonmember functions

the file: (error line is marked)

Code:

//Graph.h
#ifndef _GRAPH_
#define _GRAPH_

#include <iostream>

/**************FORWARD DECLERATIONS******************************************/
class LinkedList;
class EdgeNode;
class Edge;
class Vertex;

class Node;
class EdgeList;

/*********************END OF FORWARD DECLARATIONS***************************/
class Graph 
{
private:
	LinkedList *m_list;
	int m_countVer;

public:

	//locate edge. return pointer to location or NULL (if not found)
	EdgeNode* findEdge (const int &source,const int &dest)const;
	
	//find vertex (by id value)
	Node* findVer (const int & id)const;

	//find vertex (by vertex)
	Node* findVer (const Vertex &)const;

	//Ccot
	Graph(const Graph & g2);
	//ctor
	Graph();
	//dtor
	~Graph();

	//add vertex to graph (check if not exist first)
	void addVer(const Vertex & v1);

	//add edge to graph, add vertexes if not exist
	void addEd(const int & sourceId, const int & destSource);
	
	//delete vertex (argument- vertex)
	void delVer(const Vertex & v1);

	//delete edge. 
	void delEd(const Edge & ed1);

	//delete edges (by id)
	void delEd(const int & source,const int & dest);

	//operator union
	Graph operator+ (const Graph & g2) const ;
	
	//operator Intersection
	Graph operator-  (const Graph & g2)const;

	//operator - unary - complement
	Graph operator- () const;
 
	//operator equal and opposite
	bool operator == (const Graph & g2) const;
	bool operator != (const Graph & g2) const {return !((*this)==g2);};
	
	//operator print
	friend ostream& operator <<(ostream & os,const Graph & g2)const; // <--ERROR
};
#endif

It is a free function (or nonmember function). Free functions can't be declared const - as the error message rather clearly says.

The const after member functions applies to the implicitly passed this pointer (the object on the left of the . or -> operator). There is no this pointer in nonmember functions.

Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.