"using namespace std; " in c/c++

[relsoft]

What does it do?

Thanks!!

[shiftLynx]

Namespaces are used to collect together functions and objects from a library. They just make things nicer by adding a prefix... so if you had:

Code:

namespace MyNamespace
{
    class SomeClass
    {
        // ...
    }
}

You can either declare a new instance of the class by doing this:

Code:

MyNamespace::SomeClass someInstance;

Or you can save time and code clearer by using the 'using' statement:

Code:

using namespace MyNamespace;    // somewhere at the top

    //...

    SomeClass someInstance;

This also applies for the stdlib; for example, the official name of the 'string' class is:

Code:

std::string

However, by adding 'using namespace std;' to the top of your program, you only have to type:

Code:

string

(P.S. could somebody tell me how to tell phpBB that I specifically want C++ code in the code tags?)

[relsoft]

Oh, thanks!!!

[Oz]

(P.S. could somebody tell me how to tell phpBB that I specifically want C++ code in the code tags?)

[syntax = <<c>>][/syntax

jsut replace '<<' and '>>' with quotations

Oz~

[VonGodric]

On short -they help to clear things up and avoid nameclashes.

[helium]

You can do things like

Code:

using std::cout;

to only import specific things from a namespace. This is called a "using-declaration" (in contrast to using namespace foo, wich is called a "using-directive").

One thing you mustn't do is using "using" in a header.