The C++ namespace: the 'using' directive C++ code example

 

Compiler: Visual C++ Express Edition 2005

Compiled on Platform: Windows XP Pro SP2

Header file: Standard

Additional library: none/default

Additional project setting: Set project to be compiled as C++

Project -> your_project_name Properties -> Configuration Properties -> C/C++ -> Advanced -> Compiled As: Compiled as C++ Code (/TP)

Other info: none

To do: Separating the different namespaces using the namespace 'using' directive in C++ programming

To show: How to have different namespaces in C++ programming using the namespace 'using' directive

 

// the using directive

#include <iostream>

using namespace std;

 

namespace One

{

double p = 3.1234;

}

 

namespace Two

{

using namespace One;

 

double q = 4.5678;

 

namespace InTwo

{

double r = 5.1234;

}

}

 

int main(void)

{

// this using directive gives you all which declared in Two

using namespace Two;

 

// this using directive gives you only the InTwo namespace

using namespace Two::InTwo;

 

// this is local declaration, it takes precedence

// to see the different, comment this code and re-run this program

double p = 6.12345;

 

cout<<"p = "<<p<<endl;

cout<<"q = "<<q<<endl;

cout<<"r = "<<r<<endl;

 

return 0;

}

 

Output example:

 

p = 6.12345

q = 4.5678

r = 5.1234

Press any key to continue . . .

 

 

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