From Jason Turner

[view.interface]

C++20 → C++23 3.8 KB 43 lines
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Archived: C++20 | C++23
Markdown: C++20 | C++23
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  1. tmp/tmp43z2im40/{from.md → to.md} +30 -8
tmp/tmp43z2im40/{from.md → to.md} RENAMED
@@ -1,31 +1,53 @@
1
  ### View interface <a id="view.interface">[[view.interface]]</a>
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- The class template `view_interface` is a helper for defining `view`-like
 
 
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  types that offer a container-like interface. It is parameterized with
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  the type that is derived from it.
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  ``` cpp
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  namespace std::ranges {
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  template<class D>
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  requires is_class_v<D> && same_as<D, remove_cv_t<D>>
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- class view_interface : public view_base {
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  private:
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  constexpr D& derived() noexcept { // exposition only
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  return static_cast<D&>(*this);
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  }
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  constexpr const D& derived() const noexcept { // exposition only
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  return static_cast<const D&>(*this);
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  }
 
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  public:
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- constexpr bool empty() requires forward_range<D> {
 
 
 
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  return ranges::begin(derived()) == ranges::end(derived());
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  }
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- constexpr bool empty() const requires forward_range<const D> {
 
 
 
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  return ranges::begin(derived()) == ranges::end(derived());
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  }
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  constexpr explicit operator bool()
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  requires requires { ranges::empty(derived()); } {
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  return !ranges::empty(derived());
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  }
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  constexpr explicit operator bool() const
@@ -41,15 +63,15 @@ namespace std::ranges {
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  return to_address(ranges::begin(derived()));
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  }
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  constexpr auto size() requires forward_range<D> &&
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  sized_sentinel_for<sentinel_t<D>, iterator_t<D>> {
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- return ranges::end(derived()) - ranges::begin(derived());
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  }
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  constexpr auto size() const requires forward_range<const D> &&
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  sized_sentinel_for<sentinel_t<const D>, iterator_t<const D>> {
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- return ranges::end(derived()) - ranges::begin(derived());
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  }
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  constexpr decltype(auto) front() requires forward_range<D>;
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  constexpr decltype(auto) front() const requires forward_range<const D>;
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@@ -80,20 +102,20 @@ shall be complete, and model both `derived_from<view_interface<D>>` and
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  ``` cpp
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  constexpr decltype(auto) front() requires forward_range<D>;
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  constexpr decltype(auto) front() const requires forward_range<const D>;
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  ```
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- *Preconditions:* `!empty()`.
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  *Effects:* Equivalent to: `return *ranges::begin(`*`derived`*`());`
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  ``` cpp
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  constexpr decltype(auto) back() requires bidirectional_range<D> && common_range<D>;
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  constexpr decltype(auto) back() const
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  requires bidirectional_range<const D> && common_range<const D>;
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  ```
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- *Preconditions:* `!empty()`.
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  *Effects:* Equivalent to:
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  `return *ranges::prev(ranges::end(`*`derived`*`()));`
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  ### View interface <a id="view.interface">[[view.interface]]</a>
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+ #### General <a id="view.interface.general">[[view.interface.general]]</a>
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+
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+ The class template `view_interface` is a helper for defining view-like
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  types that offer a container-like interface. It is parameterized with
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  the type that is derived from it.
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  ``` cpp
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  namespace std::ranges {
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  template<class D>
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  requires is_class_v<D> && same_as<D, remove_cv_t<D>>
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+ class view_interface {
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  private:
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  constexpr D& derived() noexcept { // exposition only
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  return static_cast<D&>(*this);
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  }
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  constexpr const D& derived() const noexcept { // exposition only
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  return static_cast<const D&>(*this);
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  }
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+
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  public:
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+ constexpr bool empty() requires sized_range<D> || forward_range<D> {
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+ if constexpr (sized_range<D>)
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+ return ranges::size(derived()) == 0;
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+ else
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  return ranges::begin(derived()) == ranges::end(derived());
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  }
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+ constexpr bool empty() const requires sized_range<const D> || forward_range<const D> {
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+ if constexpr (sized_range<const D>)
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+ return ranges::size(derived()) == 0;
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+ else
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  return ranges::begin(derived()) == ranges::end(derived());
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  }
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+ constexpr auto cbegin() requires input_range<D> {
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+ return ranges::cbegin(derived());
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+ }
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+ constexpr auto cbegin() const requires input_range<const D> {
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+ return ranges::cbegin(derived());
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+ }
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+ constexpr auto cend() requires input_range<D> {
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+ return ranges::cend(derived());
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+ }
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+ constexpr auto cend() const requires input_range<const D> {
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+ return ranges::cend(derived());
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+ }
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+
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  constexpr explicit operator bool()
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  requires requires { ranges::empty(derived()); } {
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  return !ranges::empty(derived());
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  }
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  constexpr explicit operator bool() const
 
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  return to_address(ranges::begin(derived()));
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  }
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  constexpr auto size() requires forward_range<D> &&
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  sized_sentinel_for<sentinel_t<D>, iterator_t<D>> {
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+ return to-unsigned-like(ranges::end(derived()) - ranges::begin(derived()));
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  }
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  constexpr auto size() const requires forward_range<const D> &&
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  sized_sentinel_for<sentinel_t<const D>, iterator_t<const D>> {
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+ return to-unsigned-like(ranges::end(derived()) - ranges::begin(derived()));
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  }
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  constexpr decltype(auto) front() requires forward_range<D>;
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  constexpr decltype(auto) front() const requires forward_range<const D>;
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  ``` cpp
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  constexpr decltype(auto) front() requires forward_range<D>;
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  constexpr decltype(auto) front() const requires forward_range<const D>;
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  ```
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+ *Preconditions:* `!empty()` is `true`.
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  *Effects:* Equivalent to: `return *ranges::begin(`*`derived`*`());`
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  ``` cpp
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  constexpr decltype(auto) back() requires bidirectional_range<D> && common_range<D>;
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  constexpr decltype(auto) back() const
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  requires bidirectional_range<const D> && common_range<const D>;
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  ```
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+ *Preconditions:* `!empty()` is `true`.
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  *Effects:* Equivalent to:
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  `return *ranges::prev(ranges::end(`*`derived`*`()));`
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