Add slides. (#69)

Co-authored-by: Bowen Fu <missing>

LICENSE

@@ -186,7 +186,7 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright [yyyy] [name of copyright owner]
+   Copyright [2021] [Bowen Fu]
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.

sample/Red-black-Tree-Rebalancing.cpp

@@ -28,6 +28,7 @@ bool operator==(Node<T> const &lhs, Node<T> const &rhs)
          lhs.value == rhs.value && lhs.rhs == rhs.rhs;
 }
 
+#if 0
 template <typename T>
 void Node<T>::balance()
 {
@@ -81,6 +82,55 @@ void Node<T>::balance()
   );
 }
 
+#else
+
+template <typename T>
+void Node<T>::balance()
+{
+  using namespace matchit;
+
+  constexpr auto dsN = [](auto &&color, auto &&lhs, auto &&value, auto &&rhs)
+  {
+    return and_(app(&Node<T>::color, color), app(&Node<T>::lhs, lhs),
+                app(&Node<T>::value, value), app(&Node<T>::rhs, rhs));
+  };
+
+  constexpr auto blackN = [dsN](auto &&lhs, auto &&value, auto &&rhs)
+  {
+    return dsN(Black, lhs, value, rhs);
+  };
+
+  constexpr auto redN = [dsN](auto &&lhs, auto &&value, auto &&rhs)
+  {
+    return dsN(Red, lhs, value, rhs);
+  };
+
+  Id<std::shared_ptr<Node<T>>> a, b, c, d;
+  Id<T> x, y, z;
+  Id<Node> self;
+  *this = match(*this)(
+      pattern | blackN(some(redN(some(redN(a, x, b)), y, c)), z, d) // left-left case
+      = [&]
+      { return Node{Red, std::make_shared<Node>(Black, *a, *x, *b), *y,
+                    std::make_shared<Node>(Black, *c, *z, *d)}; },
+      pattern | blackN(some(redN(a, x, some(redN(b, y, c)))), z, d) // left-right case
+      = [&]
+      { return Node{Red, std::make_shared<Node>(Black, *a, *x, *b), *y,
+                    std::make_shared<Node>(Black, *c, *z, *d)}; },
+      pattern | blackN(a, x, some(redN(some(redN(b, y, c)), z, d))) // right-left case
+      = [&]
+      { return Node{Red, std::make_shared<Node>(Black, *a, *x, *b), *y,
+                    std::make_shared<Node>(Black, *c, *z, *d)}; },
+      pattern | blackN(a, x, some(redN(b, y, some(redN(c, z, d))))) // right-right case
+      = [&]
+      { return Node{Red, std::make_shared<Node>(Black, *a, *x, *b), *y,
+                    std::make_shared<Node>(Black, *c, *z, *d)}; },
+      pattern | self = expr(self) // do nothing
+  );
+}
+
+#endif
+
 int main()
 {
   auto x = std::make_shared<Node<int>>(Color::Red, std::shared_ptr<Node<int>>{},