LWG3848 adjacent_view, adjacent_transform_view and slide_view missing base accessor

Author: burblebee

source/ranges.tex

@@ -10573,6 +10573,9 @@
     adjacent_view() requires @\libconcept{default_initializable}@<V> = default;
     constexpr explicit adjacent_view(V base);
 
+    constexpr V base() const & requires @\libconcept{copy_constructible}@<V> { return @\exposid{base_}@; }
+    constexpr V base() && { return std::move(@\exposid{base_}@); }
+
     constexpr auto begin() requires (!@\exposconcept{simple-view}@<V>) {
       return @\exposid{iterator}@<false>(ranges::begin(@\exposid{base_}@), ranges::end(@\exposid{base_}@));
     }
@@ -11214,6 +11217,9 @@
     adjacent_transform_view() = default;
     constexpr explicit adjacent_transform_view(V base, F fun);
 
+    constexpr V base() const & requires @\libconcept{copy_constructible}@<@\exposid{InnerView}@> { return @\exposid{inner_}@.base(); }
+    constexpr V base() && { return std::move(@\exposid{inner_}@).base(); }
+
     constexpr auto begin() {
       return @\exposid{iterator}@<false>(*this, @\exposid{inner_}@.begin());
     }
@@ -12680,6 +12686,9 @@
   public:
     constexpr explicit slide_view(V base, range_difference_t<V> n);
 
+    constexpr V base() const & requires @\libconcept{copy_constructible}@<V> { return @\exposid{base_}@; }
+    constexpr V base() && { return std::move(@\exposid{base_}@); }
+
     constexpr auto begin()
       requires (!(@\exposconcept{simple-view}@<V> && @\exposconcept{slide-caches-nothing}@<const V>));
     constexpr auto begin() const requires @\exposconcept{slide-caches-nothing}@<const V>;