SeqAn3  3.2.0
The Modern C++ library for sequence analysis.
type_reduce.hpp
Go to the documentation of this file.
1 // -----------------------------------------------------------------------------------------------------
2 // Copyright (c) 2006-2022, Knut Reinert & Freie Universität Berlin
3 // Copyright (c) 2016-2022, Knut Reinert & MPI für molekulare Genetik
4 // This file may be used, modified and/or redistributed under the terms of the 3-clause BSD-License
5 // shipped with this file and also available at: https://github.com/seqan/seqan3/blob/master/LICENSE.md
6 // -----------------------------------------------------------------------------------------------------
7 
13 #pragma once
14 
15 #include <concepts>
16 #include <ranges>
17 #include <span>
18 #include <string_view>
19 
22 
23 namespace seqan3::detail
24 {
25 
26 // ============================================================================
27 // type_reduce_fn (adaptor definition)
28 // ============================================================================
29 
32 class type_reduce_fn : public adaptor_base<type_reduce_fn>
33 {
34 private:
36  using base_t = adaptor_base<type_reduce_fn>;
37 
38 public:
40  using base_t::base_t;
41 
42 private:
44  friend base_t;
45 
49  template <std::ranges::range urng_t>
50  static constexpr auto impl(urng_t && urange)
51  {
52  static_assert(
53  std::ranges::viewable_range<urng_t>,
54  "The views::type_reduce adaptor can only be passed viewable_ranges, i.e. Views or &-to-non-View.");
55 
56  // string_view
57  if constexpr (is_type_specialisation_of_v<std::remove_cvref_t<urng_t>, std::basic_string_view>)
58  {
59  return std::views::all(std::forward<urng_t>(urange));
60  }
61  // string const &
62  else if constexpr (is_type_specialisation_of_v<std::remove_cvref_t<urng_t>, std::basic_string>
64  {
65  return std::basic_string_view{std::ranges::data(urange), std::ranges::size(urange)};
66  }
67  // contiguous
68  else if constexpr (std::ranges::borrowed_range<urng_t> && std::ranges::contiguous_range<urng_t>
69  && std::ranges::sized_range<urng_t>)
70  {
71  return std::span{std::ranges::data(urange), std::ranges::size(urange)};
72  }
73  // random_access
74  else if constexpr (std::ranges::borrowed_range<urng_t> && std::ranges::random_access_range<urng_t>
75  && std::ranges::sized_range<urng_t>)
76  {
77  return std::ranges::subrange<std::ranges::iterator_t<urng_t>, std::ranges::iterator_t<urng_t>>{
78  std::ranges::begin(urange),
79  std::ranges::begin(urange) + std::ranges::size(urange),
80  std::ranges::size(urange)};
81  }
82  // pass to std::views::all (will return a view or ref-view)
83  else
84  {
85  return std::views::all(std::forward<urng_t>(urange));
86  }
87  }
88 };
89 
90 } // namespace seqan3::detail
91 
92 // ============================================================================
93 // views::type_reduce (adaptor instance definition)
94 // ============================================================================
95 
96 namespace seqan3::views
97 {
150 inline constexpr auto type_reduce = detail::type_reduce_fn{};
151 
152 } // namespace seqan3::views
153 
154 namespace seqan3
155 {
161 template <typename t>
162 using type_reduce_t = decltype(views::type_reduce(std::declval<t>()));
163 } // namespace seqan3
Provides seqan3::detail::adaptor_base and seqan3::detail::combined_adaptor.
The <concepts> header from C++20's standard library.
constexpr size_t size
The size of a type pack.
Definition: type_pack/traits.hpp:146
constexpr auto type_reduce
A view adaptor that behaves like std::views::all, but type erases certain ranges.
Definition: type_reduce.hpp:150
T is_const_v
The SeqAn namespace for views.
Definition: char_strictly_to.hpp:22
The main SeqAn3 namespace.
Definition: aligned_sequence_concept.hpp:29
decltype(views::type_reduce(std::declval< t >())) type_reduce_t
Deduces the return value of seqan3::views::type_reduce.
Definition: type_reduce.hpp:162
The <ranges> header from C++20's standard library.
Provides std::span from the C++20 standard library.
Provides type traits for working with templates.