diff --git a/include/etl/array.h b/include/etl/array.h
index efb2ce04..f1624209 100644
--- a/include/etl/array.h
+++ b/include/etl/array.h
@@ -1136,7 +1136,7 @@ namespace etl
   ///\return <b>true</b> if the arrays are equal, otherwise <b>false</b>
   //*************************************************************************
   template <typename T, size_t SIZE>
-  bool operator ==(const etl::array<T, SIZE>& lhs, const etl::array<T, SIZE>& rhs)
+  ETL_CONSTEXPR14 bool operator ==(const etl::array<T, SIZE>& lhs, const etl::array<T, SIZE>& rhs)
   {
     return etl::equal(lhs.cbegin(), lhs.cend(), rhs.cbegin());
   }
@@ -1148,7 +1148,7 @@ namespace etl
   ///\return <b>true</b> if the arrays are not equal, otherwise <b>false</b>
   //*************************************************************************
   template <typename T, size_t SIZE>
-  bool operator !=(const etl::array<T, SIZE>& lhs, const etl::array<T, SIZE>& rhs)
+  ETL_CONSTEXPR14 bool operator !=(const etl::array<T, SIZE>& lhs, const etl::array<T, SIZE>& rhs)
   {
     return !(lhs == rhs);
   }
diff --git a/include/etl/intrusive_links.h b/include/etl/intrusive_links.h
index 5c9544bf..69012668 100644
--- a/include/etl/intrusive_links.h
+++ b/include/etl/intrusive_links.h
@@ -944,7 +944,7 @@ namespace etl
   {
     TLink* current = &first;
     ((current->etl_next = &links, static_cast<TLink&>(links).etl_previous = current, current = &links), ...);
- 
+
     return current;
   }
 
@@ -1303,16 +1303,30 @@ namespace etl
   typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type
     link_rotate_left(TLink& parent, TLink& leaf)
   {
-     parent.etl_right = leaf.etl_left;
+    TLink* grandparent = parent.etl_parent;
 
-     if (parent.etl_right != ETL_NULLPTR)
-     {
-       parent.etl_right->etl_parent = &parent;
-     }
+    parent.etl_right = leaf.etl_left;
 
-     leaf.etl_parent   = parent.etl_parent;
-     parent.etl_parent = &leaf;
-     leaf.etl_left     = &parent;
+    if (parent.etl_right != ETL_NULLPTR)
+    {
+      parent.etl_right->etl_parent = &parent;
+    }
+
+    leaf.etl_parent   = grandparent;
+    parent.etl_parent = &leaf;
+    leaf.etl_left     = &parent;
+
+    if (grandparent != ETL_NULLPTR)
+    {
+      if (grandparent->etl_left == &parent)
+      {
+        grandparent->etl_left = &leaf;
+      }
+      else if (grandparent->etl_right == &parent)
+      {
+        grandparent->etl_right = &leaf;
+      }
+    }
   }
 
   //***********************************
@@ -1358,19 +1372,32 @@ namespace etl
   typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type
     link_rotate_right(TLink& parent, TLink& leaf)
   {
-     parent.etl_left = leaf.etl_right;
+    TLink* grandparent = parent.etl_parent;
 
-     if (parent.etl_left != ETL_NULLPTR)
-     {
-       parent.etl_left->etl_parent = &parent;
-     }
+    parent.etl_left = leaf.etl_right;
 
-     leaf.etl_parent   = parent.etl_parent;
-     parent.etl_parent = &leaf;
-     leaf.etl_right    = &parent;
+    if (parent.etl_left != ETL_NULLPTR)
+    {
+      parent.etl_left->etl_parent = &parent;
+    }
+
+    leaf.etl_parent   = grandparent;
+    parent.etl_parent = &leaf;
+    leaf.etl_right    = &parent;
+
+    if (grandparent != ETL_NULLPTR)
+    {
+      if (grandparent->etl_left == &parent)
+      {
+        grandparent->etl_left = &leaf;
+      }
+      else if (grandparent->etl_right == &parent)
+      {
+        grandparent->etl_right = &leaf;
+      }
+    }
   }
 
- 
   template <typename TLink>
   typename etl::enable_if<etl::is_same<TLink, etl::tree_link<TLink::ID> >::value, void>::type
     link_rotate_right(TLink* parent, TLink* leaf)
diff --git a/include/etl/type_list.h b/include/etl/type_list.h
index 3030efcd..2ef16c6d 100644
--- a/include/etl/type_list.h
+++ b/include/etl/type_list.h
@@ -53,6 +53,17 @@ namespace etl
   template <typename... TTypes>
   struct type_list;
 
+  template <typename T>
+  struct is_type_list : etl::false_type {};
+
+  template <typename... TTypes>
+  struct is_type_list<etl::type_list<TTypes...>> : etl::true_type {};
+
+#if ETL_USING_CPP17
+  template <typename T>
+  inline constexpr bool is_type_list_v = is_type_list<T>::value;
+#endif
+
   //***************************************************************************
   /// Check if a type is an etl::type_list.
   //***************************************************************************
diff --git a/test/test_array.cpp b/test/test_array.cpp
index 9edd0719..27eaf674 100644
--- a/test/test_array.cpp
+++ b/test/test_array.cpp
@@ -631,6 +631,16 @@ namespace
       CHECK(data1 == data2);
     }
 
+    //*************************************************************************
+    TEST(test_equal_constexpr)
+    {
+      ETL_CONSTEXPR14 Data data1 = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+      ETL_CONSTEXPR14 Data data2 = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+
+      ETL_CONSTEXPR14 bool result = (data1 == data2);
+      CHECK(result);
+    }
+
     //*************************************************************************
     TEST(test_not_equal)
     {
@@ -640,6 +650,16 @@ namespace
       CHECK(data1 != data2);
     }
 
+    //*************************************************************************
+    TEST(test_not_equal_constexpr)
+    {
+      ETL_CONSTEXPR14 Data data1 = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 };
+      ETL_CONSTEXPR14 Data data2 = { 9, 8, 7, 6, 5, 4, 3, 2, 1, 0 };
+
+      ETL_CONSTEXPR14 bool result = (data1 != data2);
+      CHECK(result);
+    }
+
     //*************************************************************************
     TEST(test_less_than)
     {
diff --git a/test/test_intrusive_links.cpp b/test/test_intrusive_links.cpp
index c5bb92c8..2407b724 100644
--- a/test/test_intrusive_links.cpp
+++ b/test/test_intrusive_links.cpp
@@ -554,7 +554,7 @@ namespace
       CHECK(data1.FLink0::etl_next == &data2);
       CHECK(data2.FLink0::etl_next == nullptr);
       CHECK(data3.FLink0::etl_next == nullptr);
-      
+
       etl::link_clear_range(*start);
       CHECK(data0.FLink0::etl_next == &data3);
       CHECK(data1.FLink0::etl_next == nullptr);
@@ -882,11 +882,11 @@ namespace
       BData data2(2);
       BData data3(3);
 
-      // Use reference interface    
+      // Use reference interface
       data0.BLink0::set_next(data1);
       data1.BLink0::set_next(data2);
       data2.BLink0::set_next(data3);
-      
+
       data1.BLink0::set_previous(data0);
       data2.BLink0::set_previous(data1);
       data3.BLink0::set_previous(data2);
@@ -1625,17 +1625,45 @@ namespace
       etl::link_right(a, c);
       etl::link_left(a, e);
 
+      //      r    //
+      //     /     //
+      //    b      //
+      //   / \     //
+      //  d   a    //
+      //     / \   //
+      //    e   c  //
+
       etl::link_rotate_left(b, a);
 
+      //        r  //
+      //       /   //
+      //      a    //
+      //     / \   //
+      //    b   c  //
+      //   / \     //
+      //  d   e    //
+
+      CHECK(r.etl_left   == &a);
+
       CHECK(a.etl_parent == &r);
-      CHECK(b.etl_parent == &a);
-      CHECK(e.etl_parent == &b);
-      CHECK(d.etl_parent == &b);
-      CHECK(c.etl_parent == &a);
       CHECK(a.etl_left   == &b);
       CHECK(a.etl_right  == &c);
+
+      CHECK(b.etl_parent == &a);
       CHECK(b.etl_left   == &d);
       CHECK(b.etl_right  == &e);
+
+      CHECK(d.etl_parent == &b);
+      CHECK(d.etl_left   == nullptr);
+      CHECK(d.etl_right  == nullptr);
+
+      CHECK(c.etl_parent == &a);
+      CHECK(c.etl_left   == nullptr);
+      CHECK(c.etl_right  == nullptr);
+
+      CHECK(e.etl_parent == &b);
+      CHECK(e.etl_left   == nullptr);
+      CHECK(e.etl_right  == nullptr);
     }
 
     //*************************************************************************
@@ -1656,16 +1684,41 @@ namespace
       etl::link_left(b, d);
       etl::link_right(a, c);
 
+      //      r    //
+      //     /     //
+      //    b      //
+      //   / \     //
+      //  d   a    //
+      //       \   //
+      //        c  //
+
       etl::link_rotate_left(b, a);
 
+      //        r  //
+      //       /   //
+      //      a    //
+      //     / \   //
+      //    b   c  //
+      //   /       //
+      //  d        //
+
+      CHECK(r.etl_left   == &a);
+
       CHECK(a.etl_parent == &r);
-      CHECK(b.etl_parent == &a);
-      CHECK(d.etl_parent == &b);
-      CHECK(c.etl_parent == &a);
       CHECK(a.etl_left   == &b);
       CHECK(a.etl_right  == &c);
+
+      CHECK(b.etl_parent == &a);
       CHECK(b.etl_left   == &d);
       CHECK(b.etl_right  == nullptr);
+
+      CHECK(d.etl_parent == &b);
+      CHECK(d.etl_left   == nullptr);
+      CHECK(d.etl_right  == nullptr);
+
+      CHECK(c.etl_parent == &a);
+      CHECK(c.etl_left   == nullptr);
+      CHECK(c.etl_right  == nullptr);
     }
 
     //*************************************************************************
@@ -1684,21 +1737,49 @@ namespace
       e.clear();
       etl::link_left(r, a);
       etl::link_left(a, b);
-      etl::link_left(b, d);
       etl::link_right(a, c);
+      etl::link_left(b, d);
       etl::link_right(b, e);
 
+      //        r    //
+      //       /     //
+      //      a      //
+      //     / \     //
+      //    b   c    //
+      //   / \       //
+      //  d   e      //
+
       etl::link_rotate_right(a, b);
 
+      //        r    //
+      //       /     //
+      //      b      //
+      //     / \     //
+      //    d   a    //
+      //       / \   //
+      //      e   c  //
+
+      CHECK(r.etl_left   == &b);
+
       CHECK(b.etl_parent == &r);
-      CHECK(d.etl_parent == &b);
-      CHECK(a.etl_parent == &b);
-      CHECK(e.etl_parent == &a);
-      CHECK(c.etl_parent == &a);
       CHECK(b.etl_left   == &d);
       CHECK(b.etl_right  == &a);
+
+      CHECK(d.etl_parent == &b);
+      CHECK(d.etl_left   == nullptr);
+      CHECK(d.etl_right  == nullptr);
+
+      CHECK(a.etl_parent == &b);
       CHECK(a.etl_left   == &e);
       CHECK(a.etl_right  == &c);
+
+      CHECK(c.etl_parent == &a);
+      CHECK(c.etl_left   == nullptr);
+      CHECK(c.etl_right  == nullptr);
+
+      CHECK(e.etl_parent == &a);
+      CHECK(e.etl_left   == nullptr);
+      CHECK(e.etl_right  == nullptr);
     }
 
     //*************************************************************************
@@ -1719,16 +1800,41 @@ namespace
       etl::link_left(b, d);
       etl::link_right(a, c);
 
+      //        r   //
+      //       /    //
+      //      a     //
+      //     / \    //
+      //    b   c   //
+      //   /        //
+      //  d         //
+
       etl::link_rotate_right(a, b);
 
+      //        r    //
+      //       /     //
+      //      b      //
+      //     / \     //
+      //    d   a    //
+      //         \   //
+      //          c  //
+
+      CHECK(r.etl_left   == &b);
+
       CHECK(b.etl_parent == &r);
-      CHECK(d.etl_parent == &b);
-      CHECK(a.etl_parent == &b);
-      CHECK(c.etl_parent == &a);
       CHECK(b.etl_left   == &d);
       CHECK(b.etl_right  == &a);
+
+      CHECK(d.etl_parent == &b);
+      CHECK(d.etl_left   == nullptr);
+      CHECK(d.etl_right  == nullptr);
+
+      CHECK(a.etl_parent == &b);
       CHECK(a.etl_left   == nullptr);
       CHECK(a.etl_right  == &c);
+
+      CHECK(c.etl_parent == &a);
+      CHECK(c.etl_left   == nullptr);
+      CHECK(c.etl_right  == nullptr);
     }
   }
 }