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Telegram/ThirdParty/range-v3/include/range/v3/view/empty.hpp

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+/// \file
+// Range v3 library
+//
+//  Copyright Eric Niebler 2014-present
+//
+//  Use, modification and distribution is subject to the
+//  Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+// Project home: https://github.com/ericniebler/range-v3
+//
+
+#ifndef RANGES_V3_VIEW_EMPTY_HPP
+#define RANGES_V3_VIEW_EMPTY_HPP
+
+#include <range/v3/range_fwd.hpp>
+
+#include <range/v3/view/interface.hpp>
+
+#include <range/v3/detail/prologue.hpp>
+
+namespace ranges
+{
+    /// \addtogroup group-views
+    /// @{
+    template<typename T>
+    struct empty_view : view_interface<empty_view<T>, (cardinality)0>
+    {
+        static_assert(std::is_object<T>::value,
+                      "The template parameter to empty_view must be an object type.");
+        empty_view() = default;
+        static constexpr T * begin() noexcept
+        {
+            return nullptr;
+        }
+        static constexpr T * end() noexcept
+        {
+            return nullptr;
+        }
+        static constexpr std::size_t size() noexcept
+        {
+            return 0u;
+        }
+        static constexpr T * data() noexcept
+        {
+            return nullptr;
+        }
+        RANGES_DEPRECATED(
+            "Replace views::empty<T>() with views::empty<T>. "
+            "It is now a variable template.")
+        empty_view operator()() const
+        {
+            return *this;
+        }
+    };
+
+    template<typename T>
+    RANGES_INLINE_VAR constexpr bool enable_borrowed_range<empty_view<T>> = true;
+
+    namespace views
+    {
+        template<typename T>
+        RANGES_INLINE_VAR constexpr empty_view<T> empty{};
+    }
+
+    namespace cpp20
+    {
+        namespace views
+        {
+            using ranges::views::empty;
+        }
+        template(typename T)(
+            requires std::is_object<T>::value) //
+            using empty_view = ranges::empty_view<T>;
+    } // namespace cpp20
+
+    /// @}
+} // namespace ranges
+
+#include <range/v3/detail/epilogue.hpp>
+#include <range/v3/detail/satisfy_boost_range.hpp>
+RANGES_SATISFY_BOOST_RANGE(::ranges::empty_view)
+
+#endif