hana/detail/type_foldr1.hpp

0001 /*!
0002 @file
0003 Defines `boost::hana::detail::type_foldr1`.
0004
0005 Copyright Louis Dionne 2013-2022
0006 Distributed under the Boost Software License, Version 1.0.
0007 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
0008  */
0009
0010 #ifndef BOOST_HANA_DETAIL_TYPE_FOLDR1_HPP
0011 #define BOOST_HANA_DETAIL_TYPE_FOLDR1_HPP
0012
0013 #include <boost/hana/config.hpp>
0014
0015
0016 namespace boost { namespace hana { namespace detail {
0017     template <unsigned n>
0018     struct type_foldr1_t;
0019
0020     template <>
0021     struct type_foldr1_t<0> {
0022         template <
0023             template <typename ...> class f,
0024             typename state
0025         >
0026         using result = state;
0027     };
0028
0029     template <>
0030     struct type_foldr1_t<1> {
0031         template <
0032             template <typename ...> class f,
0033             typename x1,
0034             typename state
0035         >
0036         using result = typename f<x1, state>::type;
0037     };
0038
0039     template <>
0040     struct type_foldr1_t<2> {
0041         template <
0042             template <typename ...> class f,
0043             typename x1, typename x2,
0044             typename state
0045         >
0046         using result = typename f<x1, typename f<x2, state>::type>::type;
0047     };
0048
0049     template <>
0050     struct type_foldr1_t<3> {
0051         template <
0052             template <typename ...> class f,
0053             typename x1, typename x2, typename x3,
0054             typename state
0055         >
0056         using result = typename f<
0057             x1,
0058             typename f<
0059                 x2,
0060                 typename f<
0061                     x3,
0062                     state
0063                 >::type
0064             >::type
0065         >::type;
0066     };
0067
0068     template <>
0069     struct type_foldr1_t<4> {
0070         template <
0071             template <typename ...> class f,
0072             typename x1, typename x2, typename x3, typename x4,
0073             typename state
0074         >
0075         using result = typename f<
0076             x1,
0077             typename f<
0078                 x2,
0079                 typename f<
0080                     x3,
0081                     typename f<
0082                         x4,
0083                         state
0084                     >::type
0085                 >::type
0086             >::type
0087         >::type;
0088     };
0089
0090     template <>
0091     struct type_foldr1_t<5> {
0092         template <
0093             template <typename ...> class f,
0094             typename x1, typename x2, typename x3, typename x4, typename x5,
0095             typename state
0096         >
0097         using result = typename f<
0098             x1,
0099             typename f<
0100                 x2,
0101                 typename f<
0102                     x3,
0103                     typename f<
0104                         x4,
0105                         typename f<
0106                             x5,
0107                             state
0108                         >::type
0109                     >::type
0110                 >::type
0111             >::type
0112         >::type;
0113     };
0114
0115     template <>
0116     struct type_foldr1_t<6> {
0117         template <
0118             template <typename ...> class f,
0119             typename x1, typename x2, typename x3, typename x4, typename x5, typename x6,
0120             typename ...xs
0121         >
0122         using result =
0123         typename f<
0124             x1,
0125             typename f<
0126                 x2,
0127                 typename f<
0128                     x3,
0129                     typename f<
0130                         x4,
0131                         typename f<
0132                             x5,
0133                             typename type_foldr1_t<(sizeof...(xs) > 6 ? 6 : sizeof...(xs))>::
0134                             template result<f, x6, xs...>
0135                         >::type
0136                     >::type
0137                 >::type
0138             >::type
0139         >::type;
0140     };
0141
0142     template <template <typename ...> class f, typename x1, typename ...xn>
0143     struct type_foldr1 {
0144         using type = typename type_foldr1_t<(sizeof...(xn) > 6 ? 6 : sizeof...(xn))>
0145                      ::template result<f, x1, xn...>;
0146     };
0147 } }} // end namespace boost::hana
0148
0149 #endif // !BOOST_HANA_DETAIL_TYPE_FOLDR1_HPP