55 lines
1.5 KiB
C++
55 lines
1.5 KiB
C++
// Copyright (c) Andrey Semashev 2017.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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// See http://www.boost.org/libs/config for most recent version.
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// MACRO: BOOST_NO_CXX17_ITERATOR_TRAITS
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// TITLE: C++17 std::iterator_traits
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// DESCRIPTION: The compiler does not support SFINAE-friendly std::iterator_traits defined in C++17.
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#include <iterator>
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namespace boost_no_cxx17_iterator_traits {
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struct iterator
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{
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typedef std::random_access_iterator_tag iterator_category;
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typedef char value_type;
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typedef std::ptrdiff_t difference_type;
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typedef char* pointer;
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typedef char& reference;
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reference operator*()const;
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iterator operator++();
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};
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struct non_iterator {};
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template< typename T >
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struct void_type { typedef void type; };
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template< typename Traits, typename Void = void >
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struct has_iterator_category
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{
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enum { value = false };
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};
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template< typename Traits >
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struct has_iterator_category< Traits, typename void_type< typename Traits::iterator_category >::type >
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{
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enum { value = true };
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};
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int test()
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{
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static_assert(has_iterator_category< std::iterator_traits< boost_no_cxx17_iterator_traits::iterator > >::value, "has_iterator_category failed");
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static_assert(!has_iterator_category< std::iterator_traits< boost_no_cxx17_iterator_traits::non_iterator > >::value, "has_iterator_category negative check failed");
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return 0;
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}
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}
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