From Jason Turner

[range.utility]

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  1. tmp/tmpclt_znua/{from.md → to.md} +36 -27
tmp/tmpclt_znua/{from.md → to.md} RENAMED
@@ -5,23 +5,23 @@
5
  The components in [[range.utility]] are general utilities for
6
  representing and manipulating ranges.
7
 
8
  ### Helper concepts <a id="range.utility.helpers">[[range.utility.helpers]]</a>
9
 
10
- Many of the types in subclause  [[range.utility]] are specified in terms
11
- of the following exposition-only concepts:
12
 
13
  ``` cpp
14
  template<class R>
15
  concept simple-view = // exposition only
16
  view<R> && range<const R> &&
17
  same_as<iterator_t<R>, iterator_t<const R>> &&
18
  same_as<sentinel_t<R>, sentinel_t<const R>>;
19
 
20
  template<class I>
21
  concept has-arrow = // exposition only
22
- input_iterator<I> && (is_pointer_v<I> || requires(I i) { i.operator->(); });
23
 
24
  template<class T, class U>
25
  concept different-from = // exposition only
26
  !same_as<remove_cvref_t<T>, remove_cvref_t<U>>;
27
 
@@ -135,21 +135,21 @@ shall be complete, and model both `derived_from<view_interface<D>>` and
135
  ``` cpp
136
  constexpr decltype(auto) front() requires forward_range<D>;
137
  constexpr decltype(auto) front() const requires forward_range<const D>;
138
  ```
139
 
140
- *Preconditions:* `!empty()` is `true`.
141
 
142
  *Effects:* Equivalent to: `return *ranges::begin(`*`derived`*`());`
143
 
144
  ``` cpp
145
  constexpr decltype(auto) back() requires bidirectional_range<D> && common_range<D>;
146
  constexpr decltype(auto) back() const
147
  requires bidirectional_range<const D> && common_range<const D>;
148
  ```
149
 
150
- *Preconditions:* `!empty()` is `true`.
151
 
152
  *Effects:* Equivalent to:
153
  `return *ranges::prev(ranges::end(`*`derived`*`()));`
154
 
155
  ### Sub-ranges <a id="range.subrange">[[range.subrange]]</a>
@@ -216,21 +216,21 @@ namespace std::ranges {
216
  template<different-from<subrange> PairLike>
217
  requires pair-like-convertible-from<PairLike, const I&, const S&>
218
  constexpr operator PairLike() const;
219
 
220
  constexpr I begin() const requires copyable<I>;
221
- [[nodiscard]] constexpr I begin() requires (!copyable<I>);
222
  constexpr S end() const;
223
 
224
  constexpr bool empty() const;
225
  constexpr make-unsigned-like-t<iter_difference_t<I>> size() const
226
  requires (K == subrange_kind::sized);
227
 
228
- [[nodiscard]] constexpr subrange next(iter_difference_t<I> n = 1) const &
229
  requires forward_iterator<I>;
230
- [[nodiscard]] constexpr subrange next(iter_difference_t<I> n = 1) &&;
231
- [[nodiscard]] constexpr subrange prev(iter_difference_t<I> n = 1) const
232
  requires bidirectional_iterator<I>;
233
  constexpr subrange& advance(iter_difference_t<I> n);
234
  };
235
 
236
  template<input_or_output_iterator I, sentinel_for<I> S>
@@ -309,11 +309,11 @@ constexpr I begin() const requires copyable<I>;
309
  ```
310
 
311
  *Effects:* Equivalent to: `return `*`begin_`*`;`
312
 
313
  ``` cpp
314
- [[nodiscard]] constexpr I begin() requires (!copyable<I>);
315
  ```
316
 
317
  *Effects:* Equivalent to: `return std::move(`*`begin_`*`);`
318
 
319
  ``` cpp
@@ -338,11 +338,11 @@ constexpr make-unsigned-like-t<iter_difference_t<I>> size() const
338
  - If *StoreSize* is `true`, equivalent to: `return `*`size_`*`;`
339
  - Otherwise, equivalent to:
340
  `return `*`to-unsigned-like`*`(`*`end_`*` - `*`begin_`*`);`
341
 
342
  ``` cpp
343
- [[nodiscard]] constexpr subrange next(iter_difference_t<I> n = 1) const &
344
  requires forward_iterator<I>;
345
  ```
346
 
347
  *Effects:* Equivalent to:
348
 
@@ -351,22 +351,22 @@ auto tmp = *this;
351
  tmp.advance(n);
352
  return tmp;
353
  ```
354
 
355
  ``` cpp
356
- [[nodiscard]] constexpr subrange next(iter_difference_t<I> n = 1) &&;
357
  ```
358
 
359
  *Effects:* Equivalent to:
360
 
361
  ``` cpp
362
  advance(n);
363
  return std::move(*this);
364
  ```
365
 
366
  ``` cpp
367
- [[nodiscard]] constexpr subrange prev(iter_difference_t<I> n = 1) const
368
  requires bidirectional_iterator<I>;
369
  ```
370
 
371
  *Effects:* Equivalent to:
372
 
@@ -530,30 +530,38 @@ constexpr bool reservable-container = // exposition only
530
  { c.capacity() } -> same_as<decltype(n)>;
531
  { c.max_size() } -> same_as<decltype(n)>;
532
  };
533
  ```
534
 
535
- Let *`container-insertable`* be defined as follows:
536
 
537
  ``` cpp
538
  template<class Container, class Ref>
539
- constexpr bool container-insertable = // exposition only
540
  requires(Container& c, Ref&& ref) {
541
- requires (requires { c.push_back(std::forward<Ref>(ref)); } ||
 
 
542
  requires { c.insert(c.end(), std::forward<Ref>(ref)); });
543
  };
544
  ```
545
 
546
- Let *`container-inserter`* be defined as follows:
547
 
548
  ``` cpp
549
- template<class Ref, class Container>
550
- constexpr auto container-inserter(Container& c) { // exposition only
551
- if constexpr (requires { c.push_back(declval<Ref>()); })
552
- return back_inserter(c);
 
 
 
 
 
553
  else
554
- return inserter(c, c.end());
 
555
  }
556
  ```
557
 
558
  #### `ranges::to` <a id="range.utility.conv.to">[[range.utility.conv.to]]</a>
559
 
@@ -589,21 +597,22 @@ the following manner:
589
  ``` cpp
590
  C(ranges::begin(r), ranges::end(r), std::forward<Args>(args)...)
591
  ```
592
  - Otherwise, if
593
  - `constructible_from<C, Args...>` is `true`, and
594
- - *`container-insertable`*`<C, range_reference_t<R>>` is `true`:
595
 
596
  ``` cpp
597
  C c(std::forward<Args>(args)...);
598
- if constexpr (sized_range<R> && reservable-container<C>)
599
- c.reserve(static_cast<range_size_t<C>>(ranges::size(r)));
600
- ranges::copy(r, container-inserter<range_reference_t<R>>(c));
601
  ```
 
602
  - Otherwise, if `input_range<range_reference_t<R>>` is `true`:
603
  ``` cpp
604
- to<C>(r | views::transform([](auto&& elem) {
605
  return to<range_value_t<C>>(std::forward<decltype(elem)>(elem));
606
  }), std::forward<Args>(args)...);
607
  ```
608
  - Otherwise, the program is ill-formed.
609
 
 
5
  The components in [[range.utility]] are general utilities for
6
  representing and manipulating ranges.
7
 
8
  ### Helper concepts <a id="range.utility.helpers">[[range.utility.helpers]]</a>
9
 
10
+ Many of the types in [[range.utility]] are specified in terms of the
11
+ following exposition-only concepts:
12
 
13
  ``` cpp
14
  template<class R>
15
  concept simple-view = // exposition only
16
  view<R> && range<const R> &&
17
  same_as<iterator_t<R>, iterator_t<const R>> &&
18
  same_as<sentinel_t<R>, sentinel_t<const R>>;
19
 
20
  template<class I>
21
  concept has-arrow = // exposition only
22
+ input_iterator<I> && (is_pointer_v<I> || requires(const I i) { i.operator->(); });
23
 
24
  template<class T, class U>
25
  concept different-from = // exposition only
26
  !same_as<remove_cvref_t<T>, remove_cvref_t<U>>;
27
 
 
135
  ``` cpp
136
  constexpr decltype(auto) front() requires forward_range<D>;
137
  constexpr decltype(auto) front() const requires forward_range<const D>;
138
  ```
139
 
140
+ `!empty()` is `true`.
141
 
142
  *Effects:* Equivalent to: `return *ranges::begin(`*`derived`*`());`
143
 
144
  ``` cpp
145
  constexpr decltype(auto) back() requires bidirectional_range<D> && common_range<D>;
146
  constexpr decltype(auto) back() const
147
  requires bidirectional_range<const D> && common_range<const D>;
148
  ```
149
 
150
+ `!empty()` is `true`.
151
 
152
  *Effects:* Equivalent to:
153
  `return *ranges::prev(ranges::end(`*`derived`*`()));`
154
 
155
  ### Sub-ranges <a id="range.subrange">[[range.subrange]]</a>
 
216
  template<different-from<subrange> PairLike>
217
  requires pair-like-convertible-from<PairLike, const I&, const S&>
218
  constexpr operator PairLike() const;
219
 
220
  constexpr I begin() const requires copyable<I>;
221
+ constexpr I begin() requires (!copyable<I>);
222
  constexpr S end() const;
223
 
224
  constexpr bool empty() const;
225
  constexpr make-unsigned-like-t<iter_difference_t<I>> size() const
226
  requires (K == subrange_kind::sized);
227
 
228
+ constexpr subrange next(iter_difference_t<I> n = 1) const &
229
  requires forward_iterator<I>;
230
+ constexpr subrange next(iter_difference_t<I> n = 1) &&;
231
+ constexpr subrange prev(iter_difference_t<I> n = 1) const
232
  requires bidirectional_iterator<I>;
233
  constexpr subrange& advance(iter_difference_t<I> n);
234
  };
235
 
236
  template<input_or_output_iterator I, sentinel_for<I> S>
 
309
  ```
310
 
311
  *Effects:* Equivalent to: `return `*`begin_`*`;`
312
 
313
  ``` cpp
314
+ constexpr I begin() requires (!copyable<I>);
315
  ```
316
 
317
  *Effects:* Equivalent to: `return std::move(`*`begin_`*`);`
318
 
319
  ``` cpp
 
338
  - If *StoreSize* is `true`, equivalent to: `return `*`size_`*`;`
339
  - Otherwise, equivalent to:
340
  `return `*`to-unsigned-like`*`(`*`end_`*` - `*`begin_`*`);`
341
 
342
  ``` cpp
343
+ constexpr subrange next(iter_difference_t<I> n = 1) const &
344
  requires forward_iterator<I>;
345
  ```
346
 
347
  *Effects:* Equivalent to:
348
 
 
351
  tmp.advance(n);
352
  return tmp;
353
  ```
354
 
355
  ``` cpp
356
+ constexpr subrange next(iter_difference_t<I> n = 1) &&;
357
  ```
358
 
359
  *Effects:* Equivalent to:
360
 
361
  ``` cpp
362
  advance(n);
363
  return std::move(*this);
364
  ```
365
 
366
  ``` cpp
367
+ constexpr subrange prev(iter_difference_t<I> n = 1) const
368
  requires bidirectional_iterator<I>;
369
  ```
370
 
371
  *Effects:* Equivalent to:
372
 
 
530
  { c.capacity() } -> same_as<decltype(n)>;
531
  { c.max_size() } -> same_as<decltype(n)>;
532
  };
533
  ```
534
 
535
+ Let *`container-appendable`* be defined as follows:
536
 
537
  ``` cpp
538
  template<class Container, class Ref>
539
+ constexpr bool container-appendable = // exposition only
540
  requires(Container& c, Ref&& ref) {
541
+ requires (requires { c.emplace_back(std::forward<Ref>(ref)); } ||
542
+ requires { c.push_back(std::forward<Ref>(ref)); } ||
543
+ requires { c.emplace(c.end(), std::forward<Ref>(ref)); } ||
544
  requires { c.insert(c.end(), std::forward<Ref>(ref)); });
545
  };
546
  ```
547
 
548
+ Let *`container-append`* be defined as follows:
549
 
550
  ``` cpp
551
+ template<class Container>
552
+ constexpr auto container-append(Container& c) { // exposition only
553
+ return [&c]<class Ref>(Ref&& ref) {
554
+ if constexpr (requires { c.emplace_back(declval<Ref>()); })
555
+ c.emplace_back(std::forward<Ref>(ref));
556
+ else if constexpr (requires { c.push_back(declval<Ref>()); })
557
+ c.push_back(std::forward<Ref>(ref));
558
+ else if constexpr (requires { c.emplace(c.end(), declval<Ref>()); })
559
+ c.emplace(c.end(), std::forward<Ref>(ref));
560
  else
561
+ c.insert(c.end(), std::forward<Ref>(ref));
562
+ };
563
  }
564
  ```
565
 
566
  #### `ranges::to` <a id="range.utility.conv.to">[[range.utility.conv.to]]</a>
567
 
 
597
  ``` cpp
598
  C(ranges::begin(r), ranges::end(r), std::forward<Args>(args)...)
599
  ```
600
  - Otherwise, if
601
  - `constructible_from<C, Args...>` is `true`, and
602
+ - *`container-appendable`*`<C, range_reference_t<R>>` is `true`:
603
 
604
  ``` cpp
605
  C c(std::forward<Args>(args)...);
606
+ if constexpr (approximately_sized_range<R> && reservable-container<C>)
607
+ c.reserve(static_cast<range_size_t<C>>(ranges::reserve_hint(r)));
608
+ ranges::for_each(r, container-append(c));
609
  ```
610
+ - Otherwise, the program is ill-formed.
611
  - Otherwise, if `input_range<range_reference_t<R>>` is `true`:
612
  ``` cpp
613
+ to<C>(ref_view(r) | views::transform([](auto&& elem) {
614
  return to<range_value_t<C>>(std::forward<decltype(elem)>(elem));
615
  }), std::forward<Args>(args)...);
616
  ```
617
  - Otherwise, the program is ill-formed.
618