Using a namespace in place of a static class in C++?

Question

Is it good or okay practice to use a namespace as a static class? For example:

namespace MyStaticFunctions {
    void doSomething();
}

Vers

Answer 1

There's no such thing as a "static class" in C++, so from a C++ point of view you're not using it "as a static class", you're using it "as a namespace". It's certainly accepted practice to use namespaces to group functions together.

It's up to you, though, how big you want the groups to be. It's not unusual for C++ libraries to use a single namespace for the whole public interface. That might come as a surprise to someone who is used to (say) Java, where classes are often used to group together smaller numbers of static methods. Since C++ was here first, you could say that Java is using classes as namespaces.

So, in C++ you don't tend to see classes similar to java.util.Collections or java.lang.Math, full of static members. If you want groups of functions like that in C++, use namespaces.

The exception (isn't there always a special case in C++?) is traits types like std::numeric_limits, where the template parameter makes the class do something that a namespace can't do. You could define a namespace numeric_limits containing function templates max(), min() etc, but it's not as good. Firstly, it groups things slightly differently, the type T appears "lower down the hierarchy". Secondly it doesn't do everything that a traits type does, because there's no such thing as an "object template" that would let you define a value numeric_limits::digits.

I don't know C# well enough to comment on the practical uses of static classes there, but AFAIK it's just a class restricted to having no non-static members, so it's analogous to those Java classes.