How to write a type trait `is_container` or `is_vector`?

Question

Is it possible to write a type trait whose value is true for all common STL structures (e.g., vector, set, map, ...)?

To get s

Answer 1

The way I like to detect whether something is a container is to look for data() and size() member functions. Like this:

template 
struct is_container : std::false_type {};

template 
struct is_container().data())
      , decltype(std::declval().size())>> : std::true_type {};