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 14namespace boost_no_cxx17_iterator_traits { 15 16struct 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 28struct non_iterator {}; 29 30template< typename T > 31struct void_type { typedef void type; }; 32 33template< typename Traits, typename Void = void > 34struct has_iterator_category 35{ 36 enum { value = false }; 37}; 38 39template< typename Traits > 40struct has_iterator_category< Traits, typename void_type< typename Traits::iterator_category >::type > 41{ 42 enum { value = true }; 43}; 44 45int 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} 55