ceph/src/boost/libs/config/test/boost_no_cxx17_iterator_traits.ipp

   1 //  Copyright (c) Andrey Semashev 2017.
   2 //  Use, modification and distribution are subject to the
   3 //  Boost Software License, Version 1.0. (See accompanying file
   4 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5
   6 //  See http://www.boost.org/libs/config for most recent version.
   7
   8 //  MACRO:         BOOST_NO_CXX17_ITERATOR_TRAITS
   9 //  TITLE:         C++17 std::iterator_traits
  10 //  DESCRIPTION:   The compiler does not support SFINAE-friendly std::iterator_traits defined in C++17.
  11
  12 #include <iterator>
  13
  14 namespace boost_no_cxx17_iterator_traits {
  15
  16 struct iterator
  17 {
  18    typedef std::random_access_iterator_tag iterator_category;
  19    typedef char value_type;
  20    typedef std::ptrdiff_t difference_type;
  21    typedef char* pointer;
  22    typedef char& reference;
  23
  24    reference operator*()const;
  25    iterator operator++();
  26 };
  27
  28 struct non_iterator {};
  29
  30 template< typename T >
  31 struct void_type { typedef void type; };
  32
  33 template< typename Traits, typename Void = void >
  34 struct has_iterator_category
  35 {
  36     enum { value = false };
  37 };
  38
  39 template< typename Traits >
  40 struct has_iterator_category< Traits, typename void_type< typename Traits::iterator_category >::type >
  41 {
  42     enum { value = true };
  43 };
  44
  45 int test()
  46 {
  47     static_assert(has_iterator_category< std::iterator_traits< boost_no_cxx17_iterator_traits::iterator > >::value, "has_iterator_category failed");
  48
  49     static_assert(!has_iterator_category< std::iterator_traits< boost_no_cxx17_iterator_traits::non_iterator > >::value, "has_iterator_category negative check failed");
  50
  51     return 0;
  52 }
  53
  54 }