Simplify rotate_left and rotate_right

Author: Morwenn

include/cpp-sort/detail/rotate_left.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2022 Morwenn
+ * Copyright (c) 2015-2025 Morwenn
  * SPDX-License-Identifier: MIT
  */
 #ifndef CPPSORT_DETAIL_ROTATE_LEFT_H_
@@ -17,41 +17,20 @@ namespace cppsort
 {
 namespace detail
 {
-    template<std::size_t N>
-    struct rotate_left_n
-    {
-        template<typename RandomAccessIterator>
-        auto operator()(RandomAccessIterator first) const
-            -> void
-        {
-            using utility::iter_move;
-            using difference_type = difference_type_t<RandomAccessIterator>;
-
-            auto tmp = iter_move(first);
-            for (difference_type i = 0 ;
-                 i < static_cast<difference_type>(N - 1) ;
-                 ++i)
-            {
-                first[i] = iter_move(first + (i + 1));
-            }
-            first[N-1] = std::move(tmp);
-        }
-    };
-
-    template<>
-    struct rotate_left_n<0u>
-    {
-        template<typename RandomAccessIterator>
-        auto operator()(RandomAccessIterator) const noexcept
-            -> void
-        {}
-    };
-
     template<std::size_t N, typename RandomAccessIterator>
     auto rotate_left(RandomAccessIterator first)
         -> void
     {
-        return rotate_left_n<N>{}(first);
+        static_assert(N > 1);
+
+        using utility::iter_move;
+        using difference_type = difference_type_t<RandomAccessIterator>;
+
+        auto tmp = iter_move(first);
+        for (difference_type i = 0; i < static_cast<difference_type>(N - 1); ++i) {
+            first[i] = iter_move(first + (i + 1));
+        }
+        first[N-1] = std::move(tmp);
     }
 }}
 

include/cpp-sort/detail/rotate_right.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2022 Morwenn
+ * Copyright (c) 2015-2025 Morwenn
  * SPDX-License-Identifier: MIT
  */
 #ifndef CPPSORT_DETAIL_ROTATE_RIGHT_H_
@@ -17,39 +17,20 @@ namespace cppsort
 {
 namespace detail
 {
-    template<std::size_t N>
-    struct rotate_right_n
-    {
-        template<typename RandomAccessIterator>
-        auto operator()(RandomAccessIterator first) const
-            -> void
-        {
-            using utility::iter_move;
-            using difference_type = difference_type_t<RandomAccessIterator>;
-
-            auto tmp = iter_move(first + N - 1);
-            for (difference_type i = N - 1 ; i > 0 ; --i)
-            {
-                first[i] = iter_move(first + (i - 1));
-            }
-            first[0] = std::move(tmp);
-        }
-    };
-
-    template<>
-    struct rotate_right_n<0u>
-    {
-        template<typename RandomAccessIterator>
-        auto operator()(RandomAccessIterator) const noexcept
-            -> void
-        {}
-    };
-
     template<std::size_t N, typename RandomAccessIterator>
     auto rotate_right(RandomAccessIterator first)
         -> void
     {
-        return rotate_right_n<N>{}(first);
+        static_assert(N > 1);
+
+        using utility::iter_move;
+        using difference_type = difference_type_t<RandomAccessIterator>;
+
+        auto tmp = iter_move(first + N - 1);
+        for (difference_type i = N - 1; i > 0; --i) {
+            first[i] = iter_move(first + (i - 1));
+        }
+        first[0] = std::move(tmp);
     }
 }}