Line data    Source code

       1            1 : // Distributed under the MIT License.
       2              : // See LICENSE.txt for details.
       3              : 
       4              : /// \file
       5              : /// Defines functions for slicing tuples
       6              : 
       7              : #pragma once
       8              : 
       9              : #include <cstddef>
      10              : #include <tuple>
      11              : #include <utility>
      12              : 
      13              : namespace tuple_impl_detail {
      14              : template <size_t Start, typename Tuple, size_t... Is>
      15              : constexpr std::tuple<std::tuple_element_t<Is + Start, std::decay_t<Tuple>>...>
      16              : slice_impl(Tuple&& tuple, std::index_sequence<Is...> /*meta*/) {
      17              :   return {std::get<Is + Start>(std::forward<Tuple>(tuple))...};
      18              : }
      19              : }  // namespace tuple_impl_detail
      20              : 
      21              : /// \ingroup UtilitiesGroup
      22              : /// The subset of elements in `tuple` from index `Start` to (excluding) `Stop`
      23              : template <size_t Start, size_t Stop, typename Tuple>
      24            1 : constexpr auto tuple_slice(Tuple&& tuple) {
      25              :   constexpr size_t tuple_size = std::tuple_size<std::decay_t<Tuple>>::value;
      26              :   static_assert(
      27              :       Start <= Stop and Stop <= tuple_size,
      28              :       "'Start' and 'Stop' must satisfy Start <= Stop <= size of 'Tuple'");
      29              :   return tuple_impl_detail::slice_impl<Start>(
      30              :       std::forward<Tuple>(tuple), std::make_index_sequence<Stop - Start>{});
      31              : }
      32              : 
      33              : /// \ingroup UtilitiesGroup
      34              : /// The first `Size` elements in `tuple`
      35              : template <size_t Size, typename Tuple>
      36            1 : constexpr auto tuple_head(Tuple&& tuple) {
      37              :   constexpr size_t tuple_size = std::tuple_size<std::decay_t<Tuple>>::value;
      38              :   static_assert(Size <= tuple_size,
      39              :                 "'Size' must not exceed the size of 'Tuple'");
      40              :   return tuple_slice<0, Size>(std::forward<Tuple>(tuple));
      41              : }
      42              : 
      43              : /// \ingroup UtilitiesGroup
      44              : /// The last `Size` elements in `tuple`
      45              : template <size_t Size, typename Tuple>
      46            1 : constexpr auto tuple_tail(Tuple&& tuple) {
      47              :   constexpr size_t tuple_size = std::tuple_size<std::decay_t<Tuple>>::value;
      48              :   static_assert(Size <= tuple_size,
      49              :                 "'Size' must not exceed the size of 'Tuple'");
      50              :   return tuple_slice<tuple_size - Size, tuple_size>(std::forward<Tuple>(tuple));
      51              : }