2021-04-24 20:57:01 CST W16D6

metaprogramming/template_recursion/README.md

@@ -1,2 +1,13 @@
+## CRTP 奇异递归模板模式 (Curiously recurring Template Pattern)
 
-### CRTP (Curiously recurring Template Pattern)
+1980年代作为 F-bound polymorphism 被提出。Jim Coplien 于 1995 年称之为 CRTP 。
+
+CRTP 在 C++ 中主要有两种用途：
+
+- 静态多态（static polymorphism）
+- 添加方法同时精简代码
+
+
+### Reference
+
+- https://zhuanlan.zhihu.com/p/54945314

metaprogramming/template_recursion/hello_01.cpp

@@ -0,0 +1,22 @@
+#include <iostream>
+using namespace std;
+
+template <typename Child>
+struct Base {
+    void interface() {
+        static_cast<Child*>(this)->implementation();
+    }
+};
+
+struct Derived : Base<Derived> {
+    void implementation() {
+        cerr << "Derived implementation\n";
+    }
+};
+
+int main() {
+    Derived d;
+    d.interface();  // Prints "Derived implementation"
+
+    return 0;
+}

metaprogramming/template_recursion/hello_02.cpp

@@ -0,0 +1,38 @@
+#include <iostream>
+using namespace std;
+
+template <typename Child>
+class Animal {
+   public:
+    void Run() {
+        static_cast<Child *>(this)->Run();
+    }
+};
+
+class Dog : public Animal<Dog> {
+   public:
+    void Run() {
+        cout << "Dog Run" << endl;
+    }
+};
+
+class Cat : public Animal<Cat> {
+   public:
+    void Run() {
+        cout << "Cat Run" << endl;
+    }
+};
+
+template <typename T>
+void Action(Animal<T> &animal) {
+    animal.Run();
+}
+
+int main() {
+    Dog dog;
+    Action(dog);
+
+    Cat cat;
+    Action(cat);
+    return 0;
+}