Re: [PATCH] libstdc++: P0769R2 Add shift to

[Jonathan Wakely]

On 02/03/20 10:03 +0100, Stephan Bergmann wrote:

On 21/02/2020 20:29, Patrick Palka wrote:

diff --git a/libstdc++-v3/include/bits/ranges_algo.h 
b/libstdc++-v3/include/bits/ranges_algo.h
index 7de1072abf0..c36afc6e19b 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -3683,6 +3683,54 @@ namespace ranges
   inline constexpr __prev_permutation_fn prev_permutation{};
 } // namespace ranges
+
+  template<class ForwardIterator>
+    constexpr ForwardIterator
+    shift_left(ForwardIterator __first, ForwardIterator __last,
+              typename iterator_traits<ForwardIterator>::difference_type __n)
+    {
+      __glibcxx_assert(__n >= 0);
+      if (__n == 0)
+       return __last;
+
+      auto __mid = ranges::next(__first, __n, __last);
+      if (__mid == __last)
+       return __first;
+      return std::move(std::move(__mid), std::move(__last), 
std::move(__first));
+    }
+
+  template<class ForwardIterator>
+    constexpr ForwardIterator
+    shift_right(ForwardIterator __first, ForwardIterator __last,
+               typename iterator_traits<ForwardIterator>::difference_type __n)
+    {
+      __glibcxx_assert(__n >= 0);
+      if (__n == 0)
+       return __first;
+
+      using _Cat = iterator_traits<ForwardIterator>::iterator_category;

^ FYI, the above line causes recent Clang 10 trunk with -std=c++20 to fail due to a "missing" typedef

Thanks, fixed by this patch, committed to master now.

commit 5fad000324d0bcc87283dc339423bfad6fa42c74
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Mon Mar 2 12:18:45 2020 +0000

    libstdc++: Add 'typename' to fix compilation with Clang
    
            * include/bits/ranges_algo.h (shift_right): Add 'typename' to
            dependent type.

diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h
index 8fa4a8a9161..a34f75f53d8 100644
--- a/libstdc++-v3/include/bits/ranges_algo.h
+++ b/libstdc++-v3/include/bits/ranges_algo.h
@@ -3710,7 +3710,7 @@ namespace ranges
       if (__n == 0)
 	return __first;
 
-      using _Cat = iterator_traits<ForwardIterator>::iterator_category;
+      using _Cat = typename iterator_traits<ForwardIterator>::iterator_category;
       if constexpr (derived_from<_Cat, bidirectional_iterator_tag>)
 	{
 	  auto __mid = ranges::next(__last, -__n, __first);