Unknown type name 'namespace' in Xcode 4.2
I suspect the translation is C or Objective-C, where
namespace is not a keyword as it is in C++ and Objective-C++.
Another possibility is that a previous header did not close a body (e.g. forgotten
}; at end of class declaration of forgotten
} at end of function definition).
You can rename your file with .mm or you can select your .m file and change the "File Type" to "Objective-C++ Source".