boost/stl_interfaces/fwd.hpp

0001 // Copyright (C) 2019 T. Zachary Laine
0002 //
0003 // Distributed under the Boost Software License, Version 1.0. (See
0004 // accompanying file LICENSE_1_0.txt or copy at
0005 // http://www.boost.org/LICENSE_1_0.txt)
0006 #ifndef BOOST_STL_INTERFACES_FWD_HPP
0007 #define BOOST_STL_INTERFACES_FWD_HPP
0008
0009 #include <boost/stl_interfaces/config.hpp>
0010
0011 #if BOOST_STL_INTERFACES_USE_CONCEPTS
0012 #include <ranges>
0013 #endif
0014 #if defined(__cpp_lib_three_way_comparison)
0015 #include <compare>
0016 #endif
0017
0018 #ifndef BOOST_STL_INTERFACES_DOXYGEN
0019
0020 #if defined(_MSC_VER) || defined(BOOST_GCC) && __GNUC__ < 8
0021 #define BOOST_STL_INTERFACES_NO_HIDDEN_FRIEND_CONSTEXPR
0022 #define BOOST_STL_INTERFACES_HIDDEN_FRIEND_CONSTEXPR
0023 #else
0024 #define BOOST_STL_INTERFACES_HIDDEN_FRIEND_CONSTEXPR constexpr
0025 #endif
0026
0027 #if defined(BOOST_GCC) && __GNUC__ < 9
0028 #define BOOST_STL_INTERFACES_CONCEPT concept bool
0029 #else
0030 #define BOOST_STL_INTERFACES_CONCEPT concept
0031 #endif
0032
0033 #endif
0034
0035
0036 namespace boost { namespace stl_interfaces {
0037
0038     /** An enumeration used to indicate whether the underlying data have a
0039         contiguous or discontiguous layout when instantiating `view_interface`
0040         and `sequence_container_interface`. */
0041     enum class element_layout : bool {
0042         discontiguous = false,
0043         contiguous = true
0044     };
0045
0046     BOOST_STL_INTERFACES_NAMESPACE_V1 {
0047
0048         namespace v1_dtl {
0049             template<typename... T>
0050             using void_t = void;
0051
0052             template<typename Iter>
0053             using iter_difference_t =
0054                 typename std::iterator_traits<Iter>::difference_type;
0055
0056             template<typename Range, typename = void>
0057             struct iterator;
0058             template<typename Range>
0059             struct iterator<
0060                 Range,
0061                 void_t<decltype(std::declval<Range &>().begin())>>
0062             {
0063                 using type = decltype(std::declval<Range &>().begin());
0064             };
0065             template<typename Range>
0066             using iterator_t = typename iterator<Range>::type;
0067
0068             template<typename Range, typename = void>
0069             struct sentinel;
0070             template<typename Range>
0071             struct sentinel<
0072                 Range,
0073                 void_t<decltype(std::declval<Range &>().end())>>
0074             {
0075                 using type = decltype(std::declval<Range &>().end());
0076             };
0077             template<typename Range>
0078             using sentinel_t = typename sentinel<Range>::type;
0079
0080             template<typename Range>
0081             using range_difference_t = iter_difference_t<iterator_t<Range>>;
0082
0083             template<typename Range>
0084             using common_range =
0085                 std::is_same<iterator_t<Range>, sentinel_t<Range>>;
0086
0087             template<typename Range, typename = void>
0088             struct decrementable_sentinel : std::false_type
0089             {
0090             };
0091             template<typename Range>
0092             struct decrementable_sentinel<
0093                 Range,
0094                 void_t<decltype(--std::declval<sentinel_t<Range> &>())>>
0095                 : std::true_type
0096             {
0097             };
0098         }
0099
0100     }
0101 }}
0102
0103 #endif