The example from the paper doesn't compile without the proposed
resolution for LWG 3406, so we'll add a testcase for this once the
proposed resolution is in.
libstdc++-v3/ChangeLog:
P1994R1: elements_view needs its own sentinel.
* include/std/ranges (elements_view::end): Replace these two
overloads with four new overloads.
(elements_view::_Iterator::operator==): Remove.
(elements_view::_Iterator::operator-): Likewise.
(elements_view::_Sentinel): Define.
---
libstdc++-v3/include/std/ranges | 74 ++++++++++++++++++++++++++-------
1 file changed, 60 insertions(+), 14 deletions(-)
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 9d22b138082..efa8d2cf9f4 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -3366,12 +3366,20 @@ namespace views
{ return _Iterator<true>(ranges::begin(_M_base)); }
constexpr auto
- end() requires (!__detail::__simple_view<_Vp>)
- { return ranges::end(_M_base); }
+ end()
+ { return _Sentinel<false>{ranges::end(_M_base)}; }
constexpr auto
- end() const requires __detail::__simple_view<_Vp>
- { return ranges::end(_M_base); }
+ end() requires common_range<_Vp>
+ { return _Iterator<false>{ranges::end(_M_base)}; }
+
+ constexpr auto
+ end() const requires range<const _Vp>
+ { return _Sentinel<true>{ranges::end(_M_base)}; }
+
+ constexpr auto
+ end() const requires common_range<const _Vp>
+ { return _Iterator<true>{ranges::end(_M_base)}; }
constexpr auto
size() requires sized_range<_Vp>
@@ -3382,6 +3390,9 @@ namespace views
{ return ranges::size(_M_base); }
private:
+ template<bool _Const>
+ struct _Sentinel;
+
template<bool _Const>
struct _Iterator
{
@@ -3484,10 +3495,6 @@ namespace views
requires equality_comparable<iterator_t<_Base>>
{ return __x._M_current == __y._M_current; }
- friend constexpr bool
- operator==(const _Iterator& __x, const sentinel_t<_Base>& __y)
- { return __x._M_current == __y; }
-
friend constexpr bool
operator<(const _Iterator& __x, const _Iterator& __y)
requires random_access_range<_Base>
@@ -3536,15 +3543,54 @@ namespace views
requires random_access_range<_Base>
{ return __x._M_current - __y._M_current; }
- friend constexpr difference_type
- operator-(const _Iterator<_Const>& __x, const sentinel_t<_Base>& __y)
+ friend _Sentinel<_Const>;
+ };
+
+ template<bool _Const>
+ struct _Sentinel
+ {
+ private:
+ constexpr bool
+ _M_equal(const _Iterator<_Const>& __x) const
+ { return __x._M_current == _M_end; }
+
+ using _Base = __detail::__maybe_const_t<_Const, _Vp>;
+ sentinel_t<_Base> _M_end = sentinel_t<_Base>();
+
+ public:
+ _Sentinel() = default;
+
+ constexpr explicit
+ _Sentinel(sentinel_t<_Base> __end)
+ : _M_end(std::move(__end))
+ { }
+
+ constexpr
+ _Sentinel(_Sentinel<!_Const> __other)
+ requires _Const
+ && convertible_to<sentinel_t<_Vp>, sentinel_t<_Base>>
+ : _M_end(std::move(__other._M_end))
+ { }
+
+ constexpr sentinel_t<_Base>
+ base() const
+ { return _M_end; }
+
+ friend constexpr bool
+ operator==(const _Iterator<_Const>& __x, const _Sentinel& __y)
+ { return __y._M_equal(__x); }
+
+ friend constexpr range_difference_t<_Base>
+ operator-(const _Iterator<_Const>& __x, const _Sentinel& __y)
requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
- { return __x._M_current - __y; }
+ { return __x._M_current - __y._M_end; }
- friend constexpr difference_type
- operator-(const sentinel_t<_Base>& __x, const _Iterator<_Const>& __y)
+ friend constexpr range_difference_t<_Base>
+ operator-(const _Sentinel& __x, const _Iterator<_Const>& __y)
requires sized_sentinel_for<sentinel_t<_Base>, iterator_t<_Base>>
- { return -(__y - __x); }
+ { return __x._M_end - __y._M_current; }
+
+ friend _Sentinel<!_Const>;
};
_Vp _M_base = _Vp();
--
2.28.0.337.ge9b77c84a0
