Solved

about namespaces

Posted on 2000-03-01
5
235 Views
Last Modified: 2013-11-19
what are the namespaces in c++? what is the importance of them? can we create user defined namespaces?
0
Comment
Question by:maheshhatolkar
  • 4
5 Comments
 
LVL 22

Accepted Solution

by:
nietod earned 50 total points
ID: 2573791
namespaces are "scopes" in which the symbolic names you create in your source code are placed.  All names within a namespace must be unique, but names in seperate namespaces may be duplicated.

continues
0
 
LVL 22

Expert Comment

by:nietod
ID: 2573809
In a function, you cannot have two local variables with the same name.  However two seperate functions may have variables that have the same name, like in

void f1()
{
   int X;
   double X; // Error.
}

there is an error because the same name is used twice but in

void f1()
{
   int X;
}

void f2()
{
   double X;
}

there is no error bacuase the two names are iin seperate function, i.e. seperate scopes.

continues
0
 
LVL 22

Expert Comment

by:nietod
ID: 2573831
A namespace works the same way.  It is a scope in which you can define templates, classes, constants, enums and other symbolic names.  Those names must be unique within that namespace but may be used in other namespaces. like

namepace vehicles
{
    class plane
    {
    };
};

namespace geometry
{
    class plane
    {
   };
}

the two classes defined are distinct classes buth they both can have the same name because they are defined in seperate namespaces.
0
 
LVL 22

Expert Comment

by:nietod
ID: 2573848
>> what is the importance of them?
They are used to prevent naming conflicts.  This is especially important when dealing with code libraries.  For example the STL library defines a class caled "string"  Well string is a VERY popular name.  If that name was not placed in a namespace it would conflict with the name "string" used in other circumstances.  But the name is placed in a namespace called "std"

Note to use a name that is defined in a namespace, you must preceed the name with the namespace name and a scope resolution operaotr ("::")  Like to use the STL string, you woudl specify "std::string".  Another option is to include the std::string name into the current namespace using

using std::string;

Then you don't have to specify the "std::" before "string"  Finally you could all the names defined in the std namespace into the current namespace using a single statement like

using namespace std;

>> can we create user defined namespaces?
Absolutely.
0
 

Author Comment

by:maheshhatolkar
ID: 2580335
Thanks neitod, i got really a good answer.
0

Featured Post

3 Use Cases for Connected Systems

Our Dev teams are like yours. They’re continually cranking out code for new features/bugs fixes, testing, deploying, testing some more, responding to production monitoring events and more. It’s complex. So, we thought you’d like to see what’s working for us.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

I found this questions asking how to do this in many different forums, so I will describe here how to implement a solution using PHP and AJAX. The logical flow for the problem should be: Write an event handler for the first drop down box to get …
Container Orchestration platforms empower organizations to scale their apps at an exceptional rate. This is the reason numerous innovation-driven companies are moving apps to an appropriated datacenter wide platform that empowers them to scale at a …
The viewer will learn how to pass data into a function in C++. This is one step further in using functions. Instead of only printing text onto the console, the function will be able to perform calculations with argumentents given by the user.
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.

803 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question