libstdc++: Implement ranges::repeat_view from P2474R2

libstdc++-v3/ChangeLog:

	* include/std/ranges (repeat_view): Define.
	(repeat_view::_Iterator): Define.
	(views::__detail::__can_repeat_view): Define.
	(views::__detail::__can_bounded_repeat_view): Define.
	(views::_Repeat, views::repeat): Define.
	* testsuite/std/ranges/repeat/1.cc: New test.

1 files changed, 93 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/std/ranges/repeat/1.cc b/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
new file mode 100644
index 00000000000..3698ed12c14
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/repeat/1.cc
@@ -0,0 +1,93 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do run { target c++23 } }
+
+#include <ranges>
+#include <algorithm>
+#include <testsuite_hooks.h>
+
+namespace ranges = std::ranges;
+namespace views = std::views;
+
+constexpr bool
+test01()
+{
+  auto v = views::repeat(42);
+  static_assert(ranges::random_access_range<decltype(v)>
+		&& !ranges::sized_range<decltype(v)>);
+  auto i = ranges::begin(v);
+  auto s = ranges::end(v);
+  VERIFY( *i == 42 );
+  VERIFY( i[0] == 42 );
+  VERIFY( &i[0] == &i[1] );
+  VERIFY( &*i == &*(i+1) );
+  VERIFY( i != s );
+  auto j = i + 5, k = i + 12;
+  VERIFY( k - i == 12 );
+  VERIFY( k - j == 7 );
+  VERIFY( i - j == -5 );
+  VERIFY( k > j );
+  VERIFY( j < k );
+  VERIFY( i + 5 == j );
+  VERIFY( i != j );
+  VERIFY( i + 5 <= j );
+  VERIFY( j - 5 >= i );
+
+  return true;
+}
+
+constexpr bool
+test02()
+{
+  constexpr int bound = 20;
+  auto v = views::repeat(42, bound);
+  static_assert(ranges::random_access_range<decltype(v)>
+		&& ranges::sized_range<decltype(v)>);
+  VERIFY( ranges::equal(v, views::repeat(42) | views::take(bound)) );
+  auto i = ranges::begin(v);
+  auto s = ranges::end(v);
+  VERIFY( *i == 42 );
+  VERIFY( i[0] == 42 );
+  VERIFY( &i[0] == &i[1] );
+  VERIFY( &*i == &*(i+1) );
+  VERIFY( i != s );
+  auto j = i + 5, k = i + 12;
+  VERIFY( k - i == 12 );
+  VERIFY( k - j == 7 );
+  VERIFY( i - j == -5 );
+  VERIFY( k > j );
+  VERIFY( j < k );
+  VERIFY( i + 5 == j );
+  VERIFY( i != j );
+  VERIFY( i + 5 <= j );
+  VERIFY( j - 5 >= i );
+
+  VERIFY( ranges::size(v) == bound );
+  VERIFY( s - i == bound );
+  VERIFY( s - j == bound - (j - i) );
+  VERIFY( i + bound == s );
+  VERIFY( bound + i == s );
+
+  return true;
+}
+
+constexpr bool
+test03()
+{
+  struct A { int n, m; };
+  auto v = ranges::repeat_view<A, unsigned>(std::piecewise_construct,
+					    std::tuple{1, 2},
+					    std::tuple{3});
+  VERIFY( v[0].n == 1 );
+  VERIFY( v[0].m == 2 );
+  VERIFY( ranges::size(v) == 3 );
+
+  return true;
+}
+
+int
+main()
+{
+  static_assert(test01());
+  static_assert(test02());
+  static_assert(test03());
+}