SeqAn3  3.2.0
The Modern C++ library for sequence analysis.
deep.hpp
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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 <ranges>
16 
19 
20 namespace seqan3::views
21 {
22 
102 template <typename underlying_adaptor_t>
103 class deep : public detail::adaptor_base<deep<underlying_adaptor_t>, underlying_adaptor_t>
104 {
105 private:
107  using base_type = detail::adaptor_base<deep<underlying_adaptor_t>, underlying_adaptor_t>;
108 
110  friend base_type;
111 
112 public:
116  constexpr deep() noexcept = default;
117  constexpr deep(deep const &) noexcept = default;
118  constexpr deep(deep &&) noexcept = default;
119  constexpr deep & operator=(deep const &) noexcept = default;
120  constexpr deep & operator=(deep &&) noexcept = default;
121  ~deep() noexcept = default;
122 
123  using base_type::base_type;
125 
127 
129  using base_type::operator();
130 
138  template <std::ranges::input_range urng_t, typename underlying_adaptor_t_>
139  static constexpr auto impl(urng_t && urange, underlying_adaptor_t_ && deep_adaptor)
140  {
141  static_assert(std::same_as<underlying_adaptor_t_, underlying_adaptor_t>,
142  "Internally stored deep-adaptor does not match!");
143 
144  constexpr size_t range_dimension = range_dimension_v<urng_t>;
145 
146  // note: if range_dimension == 1, the expression will actually be
147  // `std::forward<underlying_adaptor_t_>(adap)(urange)`, thus allowing the stateful adaptor to move its arguments
148  // into the view that will be constructed.
149  return recursive_adaptor<range_dimension>(std::forward<underlying_adaptor_t_>(deep_adaptor))(urange);
150  }
151 
173  template <std::size_t range_dimension>
174  static constexpr decltype(auto) recursive_adaptor(underlying_adaptor_t deep_adaptor)
175  {
176  if constexpr (range_dimension > 1u)
177  {
178  auto transform = [adaptor = recursive_adaptor<range_dimension - 1u>(
179  std::forward<underlying_adaptor_t>(deep_adaptor))](auto && inner_range)
180  {
181  // We don't want to move a stateful adaptor here, as this adaptor will be called on any element of this
182  // std::views::transform range.
183  return adaptor(std::forward<decltype(inner_range)>(inner_range));
184  };
185  return std::views::transform(std::move(transform));
186  }
187  else
188  {
189  // recursion anchor: only the innermost std::views::transform will store the deep_adaptor.
190  // In an earlier version of seqan3 we recursively passed the deep_adaptor through all std::view::transform
191  // instances and each depth stored the same deep_adaptor. The current approach can save memory as it only
192  // stores the deep_adaptor once in the innermost std::views::transform. It will also produce slightly better
193  // stack-traces by defining the recursion over the range_dimension.
194 
195  // NOTE: to allow an lvalue to be returned we need to have the return type decltype(auto).
196  return deep_adaptor;
197  }
198  }
199 
208  template <typename first_arg_t, typename... stored_arg_types>
209  requires (!std::ranges::input_range<first_arg_t>)
210  constexpr auto operator()(first_arg_t && first, stored_arg_types &&... args) const
211  {
212  // The adaptor currently wrapped is a proto-adaptor and this function has the arguments to "complete" it.
213  // We extract the adaptor that is stored and invoke it with the given arguments.
214  // This returns an adaptor closure object.
215  auto adaptor_closure =
216  std::get<0>(this->arguments)(std::forward<first_arg_t>(first), std::forward<stored_arg_types>(args)...);
217  // Now we wrap this closure object back into a views::deep to get the deep behaviour.
218  return deep<decltype(adaptor_closure)>{std::move(adaptor_closure)};
219  }
220 
222  constexpr auto operator()() const
223  {
224  // Proto-adaptors require arguments by definition, but some support defaulting those (e.g. views::translate).
225  // This extracts the proto adaptor and invokes it without args which yields a different object, the closure
226  // with default arguments.
227  auto adaptor_closure = std::get<0>(this->arguments)();
228  // Now we wrap this closure object back into a views::deep to get the deep behaviour.
229  return deep<decltype(adaptor_closure)>{std::move(adaptor_closure)};
230  }
231 
244  template <std::ranges::input_range urng_t, typename... stored_arg_types>
245  requires (sizeof...(stored_arg_types) > 0)
246  constexpr auto operator()(urng_t && urange, stored_arg_types &&... args) const
247  {
248  auto adaptor_closure = std::get<0>(this->arguments)(std::forward<stored_arg_types>(args)...);
249  deep<decltype(adaptor_closure)> deep_adaptor{std::move(adaptor_closure)};
250  return deep_adaptor(std::forward<urng_t>(urange));
251  }
252 };
253 
259 template <typename underlying_adaptor_t>
260 deep(underlying_adaptor_t && inner) -> deep<underlying_adaptor_t>;
261 
263 
264 } // namespace seqan3::views
Provides seqan3::detail::adaptor_base and seqan3::detail::combined_adaptor.
A wrapper type around an existing view adaptor that enables "deep view" behaviour for that view.
Definition: deep.hpp:104
deep(underlying_adaptor_t &&inner) -> deep< underlying_adaptor_t >
Template argument deduction helper that preserves lvalue references and turns rvalue references into ...
constexpr deep() noexcept=default
Defaulted.
Provides various transformation traits used by the range module.
T forward(T... args)
decltype(detail::transform< trait_t >(list_t{})) transform
Apply a transformation trait to every type in the list and return a seqan3::type_list of the results.
Definition: type_list/traits.hpp:469
The SeqAn namespace for views.
Definition: char_strictly_to.hpp:22
SeqAn specific customisations in the standard namespace.
The <ranges> header from C++20's standard library.