Check if a variable type is iterable?

Question

Is there any way to check if an arbitrary variable type is iterable?

So to check if it has indexed elements or I can actually loop over it's children? (Use foreach for example?)

Is it possible to create a universal template for that?

I've found techniques for other programming languages while searching for it. Yet still have to find out how to do this in C++.

Answer 1

You may create a trait for that:

namespace detail {     // To allow ADL with custom begin/end     using std::begin;     using std::end;      template <typename T>     auto is_iterable_impl(int)     -> decltype (         begin(std::declval<T&>()) != end(std::declval<T&>()), // begin/end and operator !=         void(), // Handle evil operator ,         ++std::declval<decltype(begin(std::declval<T&>()))&>(), // operator ++         void(*begin(std::declval<T&>())), // operator*         std::true_type{});      template <typename T>     std::false_type is_iterable_impl(...);  }  template <typename T> using is_iterable = decltype(detail::is_iterable_impl<T>(0)); 

Live example.