fix

Author: changkhothuychung

libcxx/include/CMakeLists.txt

@@ -668,6 +668,7 @@ set(files
   __ranges/as_rvalue_view.h
   __ranges/chunk_by_view.h
   __ranges/common_view.h
+  __ranges/concat_view.h
   __ranges/concepts.h
   __ranges/container_compatible_range.h
   __ranges/counted.h

libcxx/include/__cxx03/module.modulemap

@@ -1720,6 +1720,7 @@ module cxx03_std_private_ranges_empty                      [system] { header "__
 module cxx03_std_private_ranges_empty_view                 [system] { header "__ranges/empty_view.h" }
 module cxx03_std_private_ranges_enable_borrowed_range      [system] { header "__ranges/enable_borrowed_range.h" }
 module cxx03_std_private_ranges_enable_view                [system] { header "__ranges/enable_view.h" }
+module cxx03_std_private_ranges_concat_view                [system] { header "__ranges/concat_view.h" }
 module cxx03_std_private_ranges_filter_view                [system] {
   header "__ranges/filter_view.h"
   export std_private_ranges_range_adaptor

libcxx/include/ranges

@@ -197,6 +197,16 @@ namespace std::ranges {
     inline constexpr unspecified filter = unspecified;
   }
 
+  // [range.concat], concat view
+  template <input_range... Views>
+      requires (view<Views> && ...) && (sizeof...(Views) > 0) &&
+                concatable<Views...>
+  class concat_view;
+
+  namespace views {
+    inline constexpr unspecified concat = unspecified;
+  }
+
   // [range.drop], drop view
   template<view V>
     class drop_view;