Thread: header file

hi all,
I guess i'm missing somthing, because this header file just won't complile.
I get loads of errors....
the first error is marked, (".... error C2143: syntax error : missing ';' before 'const')
i didn't bother marking the subsequent errors... (ther're all very similar)
thanks

Code:

//Graph.h
#ifndef _GRAPH_
#define _GRAPH_

#include <iostream>
//#include "LinkedList.h"
using namespace std;


/**************FORWARD DECLARATIONS******************************************/
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(const int &source,const int &dest); // <--- ERROR!!!
	
	//find vertex (by id value)
	Node* findVer const(const int & id);

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

	//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 (const Graph & g2);
	
	//operator substarct
	Graph operator- const (const Graph & g2);

};
#endif

Assuming that you want to declare findEdge() and the others as const member functions, the proper syntax is

Code:

EdgeNode* findEdge(const int &source,const int &dest) const;

The compiler is complaining because "const" is in the wrong place.

Also, it's not a good idea to put a using declaration in a header file.

obviously!!!

please explain why it's not a good idea to put a using declaration in a header file

Sorry, that was a using directive in your header file, not a using declaration.

The reason it's not a good idea to put a using directive in a header file is that it opens the namespace in every source file (.cpp or whatever your C++ extension is) in which the header file is included. This defeats the purpose of the namespace feature, which is to prevent name collisions. Using directives are best used only in source files.

When you need to use an identifier from a namespace in a header file, use the namespace name with the scope resolution operator and identifier:

Code:

std::cout

dunno,
it's what i've been taught. whenever i want to protect a value and assure it won't be changed- pass as const ref...