how to use user-defined namespaces in another file?

[q1670741824]

Write your question here.

//filex.cpp
namespace xxx
{int x = 5;}

//file.cpp
//and here i want to use the filex.cpp namespace xxx
...
using namespace xxx;// turned out to be wrong.
...

How to make it?

[MatthewRock]

You have to write namespace xx in filex.h or filex.hpp(header file), not in .cpp file. Include header file then, and it should work

[q1670741824]

should i include all the user-defined namespaces in the header files? what if i want to include something like int x; or function definitions inside a namespace?

[MatthewRock]

Sorry, I misunderstand you.

Looks like it is your problem, with solution:
http://stackoverflow.com/questions/8971824/multiple-definition-of-namespace-variable-c-compilation

(tl;dr - you can't define variable in header; use extern keyword, and define var in .cpp file)
Basically, in filex.cpp you only define variables or functions. Declare them in header file, and use them in your code.

[Mats]

In your namespace you only declare variables. You cannot give them a value.

namespace mynspace
{
int x = 5; //wrong
int x; //correct
}

To use variables from this namespace:

mynspace::x = 1; 

using namespace <name of name space> would seem to totally defeat the point of namespaces to begin with.