https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100631
Bug ID: 100631
Summary: ranges::elements_view:: _Sentinel is missing
__distance_from() that can access _M_current of
_Iterator
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: hewillk at gmail dot com
Target Milestone: ---
We should add a __distance_from() to elements_view::_Sentinel just like
transform_view:: _Sentinel does.
https://godbolt.org/z/Ezxh78bv5
#include <ranges>
int main() {
auto r = std::views::iota(0)
| std::views::filter([](int){ return true; })
| std::views::take(42)
| std::views::reverse
| std::views::transform([](int) { return std::make_pair(42, "hello"); })
| std::views::take(42)
| std::views::keys;
auto b = r.begin();
auto e = r.end();
e - b;
}
<source>:13:8: required from here
/opt/compiler-explorer/gcc-trunk-20210513/include/c++/12.0.0/ranges:3689:39:
error:
'std::ranges::iterator_t<std::ranges::take_view<std::ranges::transform_view<std::ranges::reverse_view<std::ranges::take_view<std::ranges::filter_view<std::ranges::iota_view<int,
std::unreachable_sentinel_t>, main()::<lambda(int)> > > >,
main()::<lambda(int)> > > >
std::ranges::elements_view<std::ranges::take_view<std::ranges::transform_view<std::ranges::reverse_view<std::ranges::take_view<std::ranges::filter_view<std::ranges::iota_view<int,
std::unreachable_sentinel_t>, main()::<lambda(int)> > > >,
main()::<lambda(int)> > >, 0>::_Iterator<false>::_M_current' is private within
this context
3689 | { return __x._M_end - __y._M_current; }
| ~~~~^~~~~~~~~~
/opt/compiler-explorer/gcc-trunk-20210513/include/c++/12.0.0/ranges:3465:29:
note: declared private here
3465 | iterator_t<_Base> _M_current = iterator_t<_Base>();
| ^~~~~~~~~~
