Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
-- >8 --
libstdc++-v3/ChangeLog:
* include/bits/version.def (ranges_cache_latest): Define.
* include/bits/version.h: Regenerate.
* include/std/ranges (cache_latest_view): Define for C++26.
(cache_latest_view::_Iterator): Likewise.
(cache_latest_view::_Sentinel): Likewise.
(views::__detail::__can_cache_latest): Likewise.
(views::_CacheLatest, views::cache_latest): Likewise.
* testsuite/std/ranges/adaptors/cache_latest/1.cc: New test.
---
libstdc++-v3/include/bits/version.def | 8 ++
libstdc++-v3/include/bits/version.h | 10 ++
libstdc++-v3/include/std/ranges | 189 ++++++++++++++++++++++++++
3 files changed, 207 insertions(+)
diff --git a/libstdc++-v3/include/bits/version.def
b/libstdc++-v3/include/bits/version.def
index 002e560dc0d..6fb5db2e1fc 100644
--- a/libstdc++-v3/include/bits/version.def
+++ b/libstdc++-v3/include/bits/version.def
@@ -1837,6 +1837,14 @@ ftms = {
};
};
+ftms = {
+ name = ranges_cache_latest;
+ values = {
+ v = 202411;
+ cxxmin = 26;
+ };
+};
+
ftms = {
name = ranges_concat;
values = {
diff --git a/libstdc++-v3/include/bits/version.h
b/libstdc++-v3/include/bits/version.h
index 70de189b1e0..db61a396c45 100644
--- a/libstdc++-v3/include/bits/version.h
+++ b/libstdc++-v3/include/bits/version.h
@@ -2035,6 +2035,16 @@
#endif /* !defined(__cpp_lib_is_virtual_base_of) &&
defined(__glibcxx_want_is_virtual_base_of) */
#undef __glibcxx_want_is_virtual_base_of
+#if !defined(__cpp_lib_ranges_cache_latest)
+# if (__cplusplus > 202302L)
+# define __glibcxx_ranges_cache_latest 202411L
+# if defined(__glibcxx_want_all) ||
defined(__glibcxx_want_ranges_cache_latest)
+# define __cpp_lib_ranges_cache_latest 202411L
+# endif
+# endif
+#endif /* !defined(__cpp_lib_ranges_cache_latest) &&
defined(__glibcxx_want_ranges_cache_latest) */
+#undef __glibcxx_want_ranges_cache_latest
+
#if !defined(__cpp_lib_ranges_concat)
# if (__cplusplus > 202302L)
# define __glibcxx_ranges_concat 202403L
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 5c795a90fbc..db9a00be264 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -58,6 +58,7 @@
#define __glibcxx_want_ranges_as_const
#define __glibcxx_want_ranges_as_rvalue
#define __glibcxx_want_ranges_cartesian_product
+#define __glibcxx_want_ranges_cache_latest
#define __glibcxx_want_ranges_concat
#define __glibcxx_want_ranges_chunk
#define __glibcxx_want_ranges_chunk_by
@@ -1534,6 +1535,8 @@ namespace views::__adaptor
this->_M_payload._M_apply(_Optional_func{__f}, __i);
return this->_M_get();
}
+
+ using _Optional_base<_Tp>::_M_reset;
};
template<range _Range>
@@ -10203,6 +10206,192 @@ namespace ranges
} // namespace ranges
#endif // __cpp_lib_ranges_concat
+#if __cpp_lib_ranges_cache_latest // C++ >= 26
+namespace ranges
+{
+ template<input_range _Vp>
+ requires view<_Vp>
+ class cache_latest_view : public view_interface<cache_latest_view<_Vp>>
+ {
+ _Vp _M_base = _Vp();
+
+ using __cache_t = conditional_t<is_reference_v<range_reference_t<_Vp>>,
+ add_pointer_t<range_reference_t<_Vp>>,
+ range_reference_t<_Vp>>;
+ __detail::__non_propagating_cache<__cache_t> _M_cache;
+
+ class _Iterator;
+ class _Sentinel;
+
+ public:
+ cache_latest_view() requires default_initializable<_Vp> = default;
+
+ constexpr explicit
+ cache_latest_view(_Vp __base)
+ : _M_base(std::move(__base))
+ { }
+
+ constexpr _Vp
+ base() const & requires copy_constructible<_Vp>
+ { return _M_base; }
+
+ constexpr _Vp
+ base() &&
+ { return std::move(_M_base); }
+
+ constexpr auto
+ begin()
+ { return _Iterator(*this); }
+
+ constexpr auto
+ end()
+ { return _Sentinel(*this); }
+
+ constexpr auto
+ size() requires sized_range<_Vp>
+ { return ranges::size(_M_base); }
+
+ constexpr auto
+ size() const requires sized_range<const _Vp>
+ { return ranges::size(_M_base); }
+ };
+
+ template<typename _Range>
+ cache_latest_view(_Range&&) -> cache_latest_view<views::all_t<_Range>>;
+
+ template<input_range _Vp>
+ requires view<_Vp>
+ class cache_latest_view<_Vp>::_Iterator
+ {
+ cache_latest_view* _M_parent;
+ iterator_t<_Vp> _M_current;
+
+ constexpr explicit
+ _Iterator(cache_latest_view& __parent)
+ : _M_parent(std::__addressof(__parent)),
+ _M_current(ranges::begin(__parent._M_base))
+ { }
+
+ friend class cache_latest_view;
+
+ public:
+ using difference_type = range_difference_t<_Vp>;
+ using value_type = range_value_t<_Vp>;
+ using iterator_concept = input_iterator_tag;
+
+ _Iterator(_Iterator&&) = default;
+
+ _Iterator&
+ operator=(_Iterator&&) = default;
+
+ constexpr iterator_t<_Vp>
+ base() &&
+ { return std::move(_M_current); }
+
+ constexpr const iterator_t<_Vp>&
+ base() const & noexcept
+ { return _M_current; }
+
+ constexpr range_reference_t<_Vp>&
+ operator*() const
+ {
+ if constexpr (is_reference_v<range_reference_t<_Vp>>)
+ {
+ if (!_M_parent->_M_cache)
+ _M_parent->_M_cache =
std::__addressof(__detail::__as_lvalue(*_M_current));
+ return **_M_parent->_M_cache;
+ }
+ else
+ {
+ if (!_M_parent->_M_cache)
+ _M_parent->_M_cache._M_emplace_deref(_M_current);
+ return *_M_parent->_M_cache;
+ }
+ }
+
+ constexpr _Iterator&
+ operator++()
+ {
+ _M_parent->_M_cache._M_reset();
+ ++_M_current;
+ return *this;
+ }
+
+ constexpr void
+ operator++(int)
+ { ++*this; }
+
+ friend constexpr range_rvalue_reference_t<_Vp>
+ iter_move(const _Iterator& __i)
+ noexcept(noexcept(ranges::iter_move(__i._M_current)))
+ { return ranges::iter_move(__i._M_current); }
+
+ friend constexpr void
+ iter_swap(const _Iterator& __x, const _Iterator& __y)
+ noexcept(noexcept(ranges::iter_swap(__x._M_current, __y._M_current)))
+ requires indirectly_swappable<iterator_t<_Vp>>
+ { ranges::iter_swap(__x._M_current, __y._M_current); }
+ };
+
+ template<input_range _Vp>
+ requires view<_Vp>
+ class cache_latest_view<_Vp>::_Sentinel
+ {
+ sentinel_t<_Vp> _M_end = sentinel_t<_Vp>();
+
+ constexpr explicit
+ _Sentinel(cache_latest_view& parent)
+ : _M_end(ranges::end(parent._M_base))
+ { }
+
+ friend class cache_latest_view;
+
+ public:
+ _Sentinel() = default;
+
+ constexpr sentinel_t<_Vp>
+ base() const
+ { return _M_end; }
+
+ friend constexpr bool
+ operator==(const _Iterator& __x, const _Sentinel& __y)
+ { return __x._M_current == __y._M_end; }
+
+ friend constexpr range_difference_t<_Vp>
+ operator-(const _Iterator& __x, const _Sentinel& __y)
+ requires sized_sentinel_for<sentinel_t<_Vp>, iterator_t<_Vp>>
+ { return __x._M_current - __y._M_end; }
+
+ friend constexpr range_difference_t<_Vp>
+ operator-(const _Sentinel& __x, const _Iterator& __y)
+ requires sized_sentinel_for<sentinel_t<_Vp>, iterator_t<_Vp>>
+ { return __x._M_end - __y._M_current; }
+ };
+
+ namespace views
+ {
+ namespace __detail
+ {
+ template<typename _Tp>
+ concept __can_cache_latest = requires {
cache_latest_view(std::declval<_Tp>()); };
+ }
+
+ struct _CacheLatest : __adaptor::_RangeAdaptorClosure<_CacheLatest>
+ {
+ template<viewable_range _Range>
+ requires __detail::__can_cache_latest<_Range>
+ constexpr auto
+ operator() [[nodiscard]] (_Range&& __r) const
+ { return cache_latest_view(std::forward<_Range>(__r)); }
+
+ static constexpr bool _S_has_simple_call_op = true;
+ };
+
+ inline constexpr _CacheLatest cache_latest;
+ }
+} // namespace ranges
+#endif // __cpp_lib_ranges_cache_latest
+
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std
#endif // library concepts
--
2.48.1.291.g388218fac7.dirty
