// namespace-main-1-2.cpp		By: Aiman Hanna -  ©1993-2006 Aiman Hanna

// This program illustrates why namespaces are needed. 
// By default, every object, function, type or template declared in global scope, 
// also called global namespace scope, introduces a global entity. Each global entity 
// that is introduced in the global namespace scope must have a unique name. A function  
// and object, for example, cannot have the same name, whether or not they are declared 
// in the same program text file. 
// When create names, programmers must then make sure that their names will not conflict
// with other names from the libraries in which they will link to; otherwise name clashing 
// occurs. This name clashing problem is referred to as "global namespace pollution problem". 
// Namespaces can be used to avoid these problems. 

// In fact, this program  does not show anything about namespaces; rather it illustrates 
// why they are needed. 
//
// Key points:  1) Namespace
//				2) Global namespace scope
//				3) Global namespace pollution problem

#include "namespace1.h"
#include "namespace2.h"
int main()
{
	
	Calc1 c1(22), c11(45);
	c1.setValue(24);
	Calc2 c2;
	c2.setValue(c1);
	cout << "The value of object \"c2\" has been set to : " << c2.getValue(); 

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

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

	// Errors will still occur whether or not the dup method is called
	// Uncomment-out the following two lines and recompile
	
	// dup(c1, c11);
	// cout << "The value of object \"c1\" has been set to : " << c1.getValue() << endl; 

	return 0;
}


// The result of compiling the program
/*
--------------------Configuration: namespace-main-1-2 - Win32 Debug--------------------
Compiling...
namespace-main-1-2.cpp
namespace2.h(22) : error C2371: 'dup' : redefinition; different basic types
namespace-main-1-2.cpp(34) : error C2228: left of '.setValue' must have class/struct/union type
namespace-main-1-2.cpp(35) : error C2228: left of '.getValue' must have class/struct/union type
namespace1.cpp
namespace2.cpp
namespace2.h(22) : error C2371: 'dup' : redefinition; different basic types
Error executing cl.exe.

namespace-main-1-2.exe - 4 error(s), 0 warning(s)

*/