// namespace-main-15-16.cpp		By: Aiman Hanna -  ©1993-2006 Aiman Hanna

// This program illustrates the "using declarations" for namespaces and program scopes. 
// It is possible to make the member of a namespace visible so that it can be 
// referred to outside the namespace directly with its name (no need 
// for namespace_name:: before the variable). That is possible if the member 
// is declared with a using declarations. 
//
// As with any other declaration, a name introduced by a using declaration has 
// these characteristics: 
//      1) It must be unique in its scope
//      2) It hides the same name introduced by a declaration in an enclosing scope
//      3) It is hidden by a declaration of the same name in a nested scope
 
// Key points:  1) Using Declaration & scope


#include "namespace16.h"

void fun1()
{
cout << "Starting call to fun1()" << endl;

	
using region4::dup;
using region3::Greeting;

Greeting();
region3::Calc1 c1(200);
dup.setValue(c1);
cout << "The value of object \"dup\" has been set to : " << dup.getValue() << endl; 

cout << "Ending call to fun1()" << endl;


}





int main()
{
	
// The following using declarations are introduced inside the main() function; as a 
// result they are only in effect inside this function. 

using region3::Calc1;
using region3::dup;	
using region3::region31::message1;
using region3::region31::region32::message2;
using region3::region31::region32::region33::message3;
using region3::Greeting;

using region4::Calc2;
// The following can NOT be done since it will cause multiple declaration 
// in the same scope. Un-comment-out the following line and compile for details. 

// using region4::dup;	

	Greeting();

	Calc1 c1(30), c11(45);;
	c1.setValue(32);

	Calc2 c2;
	c2.setValue(c1);
	cout << "The value of object \"c2\" has been set to : " << c2.getValue() << endl; 

	// use the global object - set it to the same value as c1

	region4::dup.setValue(c1);
	cout << "The value of object \"dup\" has been set to : " << region4::dup.getValue() << endl; 

	region3::dup(c1, c11);
	cout << "The value of object \"c1\" has been set to : " << c1.getValue() << endl; 

	cout << "\n\n==============================================\n";
	message1();
	message2();
	message3();
	cout << "==============================================\n";

	//start a scope 

	{
	cout << "Inside Main() / Scope" << endl;

	
	using region4::dup;
	

	Greeting();
	Calc1 c1(5000);
	dup.setValue(c1);
	cout << "The value of object \"dup\" has been set to : " << dup.getValue() << endl; 

	cout << "Leaving Main() / Scope" << endl;
	}


	fun1();
	return 0;
}


// The result of running the program
/*
Hello from region 3.
The value of object "c2" has been set to : 32
The value of object "dup" has been set to : 32
The value of object "c1" has been set to : 45


==============================================
Hello...there...Is that really much better?
==============================================
Inside Main() / Scope
Hello from region 3.
The value of object "dup" has been set to : 5000
Leaving Main() / Scope
Starting call to fun1()
Hello from region 3.
The value of object "dup" has been set to : 200
Ending call to fun1()

*/