c++ - Difference between classes and namespaces?

Question

I'm looking at namespaces and I don't really see a difference between these and classes. I'm teaching myself C++ I've gotten several books online, so I know I'm not learning the most effectively. Anyway, can someone tell me the difference between the two, and what would be the best time to use a namepace over a class? Also, I don't see much about structs in the book I'm reading.

Is this the format?

struct go
{

  goNow(){ cout << "go Now"};

}

Thanks in advance for your assistance.

Answer 1

Classes and structs define types. You can create an object of a type. Namespaces simply declare a scope inside which other types, functions, objects, or namespaces can exist. You can't create an object of type std (unless of course you created a type called std, which would hide the std namespace).

When you define a function inside a struct/class (a method) you're saying "This function is a fundamental operation on the associated data". When you define a function inside a namespace you're saying "This function is logically related to other functions, types, and objects in the namespace"

Edit

It's probably worth pointing out that "everything is an object" languages like Java and C# regularly use classes as if they were namespaces because they don't allow "free" functions. This may be where the confusion comes from. If you have a class in another language that contains nothing but static members, you would want to use a namespace and free functions in the C++ version.