Check if a variable type is iterable?

by

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.

More Related Contents:

  1. How does `is_base_of` work?
  2. What do compilers do with compile-time branching?
  3. Disambiguate overloaded member function pointer being passed as template parameter
  4. How to write `is_complete` template?
  5. C++11 is_same type trait for templates
  6. How to tell if template type is an instance of a template class?
  7. Check if a type is passed in variadic template parameter pack
  8. How to test whether class B is derived from template family of classes
  9. How to tell if a type is an instance of a specific template class?
  10. C++11 does not deduce type when std::function or lambda functions are involved
  11. Why can’t the template argument be deduced when it is used as template parameter to another template?
  12. Why can’t I use float value as a template parameter?
  13. Explicit specialization in non-namespace scope [duplicate]
  14. Explicit template instantiation – when is it used?
  15. Accessing inherited variable from templated parent class [duplicate]
  16. SFINAE to check for inherited member functions
  17. When to use std::forward to forward arguments?
  18. check variadic templates parameters for uniqueness
  19. How does the standard library implement std::swap?
  20. Inheritance and templates in C++ – why are inherited members invisible?
  21. Template specialization of a single method from a templated class
  22. Template class with template container
  23. Expansion with variadic templates [duplicate]
  24. Get index of a tuple element’s type?
  25. Reason for using non-type template parameter instead of regular parameter?
  26. Template default arguments
  27. Default template argument when using std::enable_if as templ. param.: why OK with two template functions that differ only in the enable_if parameter?
  28. compile time loops
  29. C++ Template Metaprogramming – Is it possible to output the generated code?
  30. if / else at compile time in C++?

Leave a Comment