What is the motivation behind static polymorphism in C++?

Question

I understand the mechanics of static polymorphism using the Curiously Recurring Template Pattern. I just do not understand what is it good for.

The declared motivat

Answer 1

While there may be cases where static polymorphism is useful (the other answers have listed a few), I would generally see it as a bad thing. Why? Because you cannot actually use a pointer to the base class anymore, you always have to provide a template argument providing the exact derived type. And in that case, you could just as well use the derived type directly. And, to put it bluntly, static polymorphism is not what object orientation is about.

The runtime difference between static and dynamic polymorphism is exactly two pointer dereferenciations (iff the compiler really inlines the dispatch method in the base class, if it doesn't for some reason, static polymorphism is slower). That's not really expensive, especially since the second lookup should virtually always hit the cache. All in all, those lookups are usually cheaper than the function call itself, and are certainly worth it to get the real flexibility provided by dynamic polymorphism.