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4235. cache_latest_view and to_input_view miss reserve_hint

Section: 25.7.34.2 [range.cache.latest.view], 25.7.35.2 [range.to.input.view] Status: New Submitter: Hewill Kang Opened: 2025-03-25 Last modified: 2025-03-27

Priority: Not Prioritized

View all issues with New status.

Discussion:

Intuitively, both view classes should also have reserve_hint members.

Proposed resolution:

This wording is relative to N5008.

1. Modify 25.7.34.2 [range.cache.latest.view] as indicated:

   namespace std::ranges {
     template<input_range V>
       requires view<V>
     class cache_latest_view : public view_interface<cache_latest_view<V>> {
       […]
       constexpr auto size() requires sized_range<V>;
       constexpr auto size() const requires sized_range<const V>;
   
       constexpr auto reserve_hint() requires approximately_sized_range<V>;
       constexpr auto reserve_hint() const requires approximately_sized_range<const V>;
     };
     […]
   }
   

   […]

   constexpr auto size() requires sized_range<V>;
   constexpr auto size() const requires sized_range<const V>;
   

   -4- Effects: Equivalent to: return ranges::size(base_);

   
   constexpr auto reserve_hint() requires approximately_sized_range<V>;
   constexpr auto reserve_hint() const requires approximately_sized_range<const V>;
   

   -?- Effects: Equivalent to: return ranges::reserve_hint(base_);

2. Modify 25.7.35.2 [range.to.input.view] as indicated:

   template<input_range V>
     requires view<V>
   class to_input_view : public view_interface<to_input_view<V>> {
     […]
     constexpr auto size() requires sized_range<V>;
     constexpr auto size() const requires sized_range<const V>;
   
     constexpr auto reserve_hint() requires approximately_sized_range<V>;
     constexpr auto reserve_hint() const requires approximately_sized_range<const V>;
   };
   […]
   

   […]

   constexpr auto size() requires sized_range<V>;
   constexpr auto size() const requires sized_range<const V>;
   

   -5- Effects: Equivalent to: return ranges::size(base_);

   
   constexpr auto reserve_hint() requires approximately_sized_range<V>;
   constexpr auto reserve_hint() const requires approximately_sized_range<const V>;
   

   -?- Effects: Equivalent to: return ranges::reserve_hint(base_);