boost/hana/detail/variadic/split_at.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::detail::variadic::split_at`.
   4
   5 @copyright Louis Dionne 2013-2017
   6 Distributed under the Boost Software License, Version 1.0.
   7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   8  */
   9
  10 #ifndef BOOST_HANA_DETAIL_VARIADIC_SPLIT_AT_HPP
  11 #define BOOST_HANA_DETAIL_VARIADIC_SPLIT_AT_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/functional/partial.hpp>
  15 #include <boost/hana/functional/reverse_partial.hpp>
  16
  17 #include <cstddef>
  18
  19
  20 BOOST_HANA_NAMESPACE_BEGIN namespace detail { namespace variadic {
  21     template <std::size_t n>
  22     struct split_at_t {
  23         template <typename F, typename X1, typename X2, typename X3, typename X4, typename X5, typename X6, typename X7, typename X8, typename ...Xs>
  24         constexpr decltype(auto) operator()(F&& f, X1&& x1, X2&& x2, X3&& x3, X4&& x4, X5&& x5, X6&& x6, X7&& x7, X8&& x8, Xs&& ...xs) const {
  25             return split_at_t<n - 8>{}(
  26                 hana::partial(static_cast<F&&>(f),
  27                     static_cast<X1&&>(x1),
  28                     static_cast<X2&&>(x2),
  29                     static_cast<X3&&>(x3),
  30                     static_cast<X4&&>(x4),
  31                     static_cast<X5&&>(x5),
  32                     static_cast<X6&&>(x6),
  33                     static_cast<X7&&>(x7),
  34                     static_cast<X8&&>(x8)
  35                 ),
  36                 static_cast<Xs&&>(xs)...
  37             );
  38         }
  39     };
  40
  41     template <>
  42     struct split_at_t<0> {
  43         template <typename F, typename ...Xs>
  44         constexpr decltype(auto) operator()(F&& f, Xs&& ...xs) const {
  45             return static_cast<F&&>(f)()(static_cast<Xs&&>(xs)...);
  46         }
  47     };
  48
  49     template <>
  50     struct split_at_t<1> {
  51         template <typename F, typename X1, typename ...Xs>
  52         constexpr decltype(auto) operator()(F&& f, X1&& x1, Xs&& ...xs) const {
  53             return static_cast<F&&>(f)(
  54                 static_cast<X1&&>(x1)
  55             )(static_cast<Xs&&>(xs)...);
  56         }
  57     };
  58
  59     template <>
  60     struct split_at_t<2> {
  61         template <typename F, typename X1, typename X2, typename ...Xs>
  62         constexpr decltype(auto) operator()(F&& f, X1&& x1, X2&& x2, Xs&& ...xs) const {
  63             return static_cast<F&&>(f)(
  64                 static_cast<X1&&>(x1),
  65                 static_cast<X2&&>(x2)
  66             )(static_cast<Xs&&>(xs)...);
  67         }
  68     };
  69
  70     template <>
  71     struct split_at_t<3> {
  72         template <typename F, typename X1, typename X2, typename X3, typename ...Xs>
  73         constexpr decltype(auto) operator()(F&& f, X1&& x1, X2&& x2, X3&& x3, Xs&& ...xs) const {
  74             return static_cast<F&&>(f)(
  75                 static_cast<X1&&>(x1),
  76                 static_cast<X2&&>(x2),
  77                 static_cast<X3&&>(x3)
  78             )(static_cast<Xs&&>(xs)...);
  79         }
  80     };
  81
  82     template <>
  83     struct split_at_t<4> {
  84         template <typename F, typename X1, typename X2, typename X3, typename X4, typename ...Xs>
  85         constexpr decltype(auto) operator()(F&& f, X1&& x1, X2&& x2, X3&& x3, X4&& x4, Xs&& ...xs) const {
  86             return static_cast<F&&>(f)(
  87                 static_cast<X1&&>(x1),
  88                 static_cast<X2&&>(x2),
  89                 static_cast<X3&&>(x3),
  90                 static_cast<X4&&>(x4)
  91             )(static_cast<Xs&&>(xs)...);
  92         }
  93     };
  94
  95     template <>
  96     struct split_at_t<5> {
  97         template <typename F, typename X1, typename X2, typename X3, typename X4, typename X5, typename ...Xs>
  98         constexpr decltype(auto) operator()(F&& f, X1&& x1, X2&& x2, X3&& x3, X4&& x4, X5&& x5, Xs&& ...xs) const {
  99             return static_cast<F&&>(f)(
 100                 static_cast<X1&&>(x1),
 101                 static_cast<X2&&>(x2),
 102                 static_cast<X3&&>(x3),
 103                 static_cast<X4&&>(x4),
 104                 static_cast<X5&&>(x5)
 105             )(static_cast<Xs&&>(xs)...);
 106         }
 107     };
 108
 109     template <>
 110     struct split_at_t<6> {
 111         template <typename F, typename X1, typename X2, typename X3, typename X4, typename X5, typename X6, typename ...Xs>
 112         constexpr decltype(auto) operator()(F&& f, X1&& x1, X2&& x2, X3&& x3, X4&& x4, X5&& x5, X6&& x6, Xs&& ...xs) const {
 113             return static_cast<F&&>(f)(
 114                 static_cast<X1&&>(x1),
 115                 static_cast<X2&&>(x2),
 116                 static_cast<X3&&>(x3),
 117                 static_cast<X4&&>(x4),
 118                 static_cast<X5&&>(x5),
 119                 static_cast<X6&&>(x6)
 120             )(static_cast<Xs&&>(xs)...);
 121         }
 122     };
 123
 124     template <>
 125     struct split_at_t<7> {
 126         template <typename F, typename X1, typename X2, typename X3, typename X4, typename X5, typename X6, typename X7, typename ...Xs>
 127         constexpr decltype(auto) operator()(F&& f, X1&& x1, X2&& x2, X3&& x3, X4&& x4, X5&& x5, X6&& x6, X7&& x7, Xs&& ...xs) const {
 128             return static_cast<F&&>(f)(
 129                 static_cast<X1&&>(x1),
 130                 static_cast<X2&&>(x2),
 131                 static_cast<X3&&>(x3),
 132                 static_cast<X4&&>(x4),
 133                 static_cast<X5&&>(x5),
 134                 static_cast<X6&&>(x6),
 135                 static_cast<X7&&>(x7)
 136             )(static_cast<Xs&&>(xs)...);
 137         }
 138     };
 139
 140     template <std::size_t n>
 141     struct _makesplit_at_t {
 142         template <typename ...Xs>
 143         constexpr decltype(auto) operator()(Xs&& ...xs) const {
 144             return hana::reverse_partial(split_at_t<n>{},
 145                                          static_cast<Xs&&>(xs)...);
 146         }
 147     };
 148
 149     template <std::size_t n>
 150     constexpr _makesplit_at_t<n> split_at{};
 151 }} BOOST_HANA_NAMESPACE_END
 152
 153 #endif // !BOOST_HANA_DETAIL_VARIADIC_SPLIT_AT_HPP