From Jason Turner

[range.reverse]

C++20 → C++23 3.2 KB 33 lines
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Archived: C++20 | C++23
Markdown: C++20 | C++23
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  1. tmp/tmpm2b1ooe0/{from.md → to.md} +12 -14
tmp/tmpm2b1ooe0/{from.md → to.md} RENAMED
@@ -1,24 +1,21 @@
1
  ### Reverse view <a id="range.reverse">[[range.reverse]]</a>
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  #### Overview <a id="range.reverse.overview">[[range.reverse.overview]]</a>
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- `reverse_view` takes a bidirectional `view` and produces another `view`
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- that iterates the same elements in reverse order.
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  The name `views::reverse` denotes a range adaptor object
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  [[range.adaptor.object]]. Given a subexpression `E`, the expression
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  `views::reverse(E)` is expression-equivalent to:
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  - If the type of `E` is a (possibly cv-qualified) specialization of
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  `reverse_view`, equivalent to `E.base()`.
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- - Otherwise, if the type of `E` is cv-qualified
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- ``` cpp
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- subrange<reverse_iterator<I>, reverse_iterator<I>, K>
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- ```
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-
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- for some iterator type `I` and value `K` of type `subrange_kind`,
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  - if `K` is `subrange_kind::sized`, equivalent to:
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  ``` cpp
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  subrange<I, I, K>(E.end().base(), E.begin().base(), E.size())
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  ```
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  - otherwise, equivalent to:
@@ -31,13 +28,12 @@ The name `views::reverse` denotes a range adaptor object
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  [*Example 1*:
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  ``` cpp
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  vector<int> is {0,1,2,3,4};
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- reverse_view rv {is};
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- for (int i : rv)
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- cout << i << ' '; // prints: 4 3 2 1 0
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  ```
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  — *end example*]
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  #### Class template `reverse_view` <a id="range.reverse.view">[[range.reverse.view]]</a>
@@ -47,12 +43,13 @@ namespace std::ranges {
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  template<view V>
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  requires bidirectional_range<V>
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  class reverse_view : public view_interface<reverse_view<V>> {
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  private:
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  V base_ = V(); // exposition only
 
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  public:
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- reverse_view() = default;
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  constexpr explicit reverse_view(V r);
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  constexpr V base() const & requires copy_constructible<V> { return base_; }
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  constexpr V base() && { return std::move(base_); }
@@ -65,10 +62,11 @@ namespace std::ranges {
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  constexpr auto end() const requires common_range<const V>;
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  constexpr auto size() requires sized_range<V> {
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  return ranges::size(base_);
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  }
 
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  constexpr auto size() const requires sized_range<const V> {
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  return ranges::size(base_);
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  }
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  };
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@@ -101,15 +99,15 @@ the `reverse_view` for use on subsequent calls.
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  constexpr reverse_iterator<iterator_t<V>> begin() requires common_range<V>;
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  constexpr auto begin() const requires common_range<const V>;
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  ```
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  *Effects:* Equivalent to:
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- `return make_reverse_iterator(ranges::end(base_));`
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  ``` cpp
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  constexpr reverse_iterator<iterator_t<V>> end();
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  constexpr auto end() const requires common_range<const V>;
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  ```
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  *Effects:* Equivalent to:
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- `return make_reverse_iterator(ranges::begin(base_));`
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1
  ### Reverse view <a id="range.reverse">[[range.reverse]]</a>
2
 
3
  #### Overview <a id="range.reverse.overview">[[range.reverse.overview]]</a>
4
 
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+ `reverse_view` takes a bidirectional view and produces another view that
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+ iterates the same elements in reverse order.
7
 
8
  The name `views::reverse` denotes a range adaptor object
9
  [[range.adaptor.object]]. Given a subexpression `E`, the expression
10
  `views::reverse(E)` is expression-equivalent to:
11
 
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  - If the type of `E` is a (possibly cv-qualified) specialization of
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  `reverse_view`, equivalent to `E.base()`.
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+ - Otherwise, if the type of `E` is cv
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+ `subrange<reverse_iterator<I>, reverse_iterator<I>, K>` for some
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+ iterator type `I` and value `K` of type `subrange_kind`,
 
 
 
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  - if `K` is `subrange_kind::sized`, equivalent to:
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  ``` cpp
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  subrange<I, I, K>(E.end().base(), E.begin().base(), E.size())
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  ```
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  - otherwise, equivalent to:
 
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  [*Example 1*:
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  ``` cpp
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  vector<int> is {0,1,2,3,4};
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+ for (int i : is | views::reverse)
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+ cout << i << ' '; // prints 4 3 2 1 0
 
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  ```
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  — *end example*]
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  #### Class template `reverse_view` <a id="range.reverse.view">[[range.reverse.view]]</a>
 
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  template<view V>
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  requires bidirectional_range<V>
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  class reverse_view : public view_interface<reverse_view<V>> {
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  private:
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  V base_ = V(); // exposition only
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+
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  public:
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+ reverse_view() requires default_initializable<V> = default;
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  constexpr explicit reverse_view(V r);
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  constexpr V base() const & requires copy_constructible<V> { return base_; }
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  constexpr V base() && { return std::move(base_); }
 
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  constexpr auto end() const requires common_range<const V>;
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  constexpr auto size() requires sized_range<V> {
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  return ranges::size(base_);
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  }
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+
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  constexpr auto size() const requires sized_range<const V> {
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  return ranges::size(base_);
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  }
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  };
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  constexpr reverse_iterator<iterator_t<V>> begin() requires common_range<V>;
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  constexpr auto begin() const requires common_range<const V>;
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  ```
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  *Effects:* Equivalent to:
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+ `return make_reverse_iterator(ranges::end(`*`base_`*`));`
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  ``` cpp
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  constexpr reverse_iterator<iterator_t<V>> end();
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  constexpr auto end() const requires common_range<const V>;
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  ```
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  *Effects:* Equivalent to:
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+ `return make_reverse_iterator(ranges::begin(`*`base_`*`));`
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