boost/pfr/tuple_size.hpp

0001 // Copyright (c) 2016-2025 Antony Polukhin
0002 //
0003 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0004 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0005
0006
0007 #ifndef BOOST_PFR_TUPLE_SIZE_HPP
0008 #define BOOST_PFR_TUPLE_SIZE_HPP
0009 #pragma once
0010
0011 #include <boost/pfr/detail/config.hpp>
0012
0013 #include <type_traits>
0014 #include <utility>      // metaprogramming stuff
0015
0016 #include <boost/pfr/detail/sequence_tuple.hpp>
0017 #include <boost/pfr/detail/fields_count.hpp>
0018
0019 /// \file boost/pfr/tuple_size.hpp
0020 /// Contains tuple-like interfaces to get fields count \forcedlink{tuple_size}, \forcedlink{tuple_size_v}.
0021 ///
0022 /// \b Synopsis:
0023 namespace boost { namespace pfr {
0024
0025 BOOST_PFR_BEGIN_MODULE_EXPORT
0026
0027 /// Has a static const member variable `value` that contains fields count in a T.
0028 /// Works for any T that satisfies \aggregate.
0029 ///
0030 /// \b Example:
0031 /// \code
0032 ///     std::array<int, boost::pfr::tuple_size<my_structure>::value > a;
0033 /// \endcode
0034 template <class T>
0035 using tuple_size = detail::size_t_< boost::pfr::detail::fields_count<T>() >;
0036
0037
0038 /// `tuple_size_v` is a template variable that contains fields count in a T and
0039 /// works for any T that satisfies \aggregate.
0040 ///
0041 /// \b Example:
0042 /// \code
0043 ///     std::array<int, boost::pfr::tuple_size_v<my_structure> > a;
0044 /// \endcode
0045 template <class T>
0046 constexpr std::size_t tuple_size_v = tuple_size<T>::value;
0047
0048 BOOST_PFR_END_MODULE_EXPORT
0049
0050 }} // namespace boost::pfr
0051
0052 #endif // BOOST_PFR_TUPLE_SIZE_HPP