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

Look, another SFINAE-based solution for detecting STL-like containers:

template
struct is_container : std::false_type {};

template
struct is_container_helper {};

template
struct is_container<
        T,
        std::conditional_t<
            false,
            is_container_helper<
                typename T::value_type,
                typename T::size_type,
                typename T::allocator_type,
                typename T::iterator,
                typename T::const_iterator,
                decltype(std::declval().size()),
                decltype(std::declval().begin()),
                decltype(std::declval().end()),
                decltype(std::declval().cbegin()),
                decltype(std::declval().cend())
                >,
            void
            >
        > : public std::true_type {};

Of course, you might change methods and types to be checked.

If you want to detect only STL containers (it means std::vector, std::list, etc) you should do something like this.