revision #2: 修改文件名

code/2/todo/2.6.autox.cpp

@@ -1,49 +0,0 @@
-//
-// 2.3.cpp
-// c++1x tutorial
-//
-// created by changkun at changkun.de
-//
-// auto/decltype/尾返回类型/返回类型推导
-
-
-#include <iostream>
-
-// 传统 C++
-template <typename R, typename T, typename U>
-R add1(T x, U y) {
-    return x+y;
-}
-
-// 尾返回类型
-template <typename T, typename U>
-auto add2(T x, U y) -> decltype(x+y) {
-    return x+y;
-}
-
-// C++14 返回类型推导
-template <typename T, typename U>
-auto add3(T x, U y) {
-    return x+y;
-}
-
-int main() {
-    auto i = 5;
-    
-    int arr[10] = {0};
-    auto auto_arr = arr;        // 正确，对整个类型进行推导
-    // auto auto_arr2[10] = arr;   // 错误,  无法推导数组元素类型
-
-    auto x = 1;
-    auto y = 2;
-    decltype(x+y) z1;
-    //auto z2;                  // 错误, 无法推导
-
-    
-    std::cout << add1<int, int, int>(1,1) << std::endl;
-    std::cout << add1<int, int>(1,1) << std::endl;
-    std::cout << add1<int, int>(1,1) << std::endl;
-    
-    
-    return 0;
-}

code/2/todo/2.6.cpp

@@ -0,0 +1,76 @@
+//
+// 2.6.cpp
+// c++1x tutorial
+//
+// created by changkun at changkun.de
+//
+// 模板增强
+
+
+#include <iostream>
+#include <vector>
+#include <string>
+
+template class std::vector<bool>;            // 强行实例化
+extern template class std::vector<double>;   // 不在该编译文件中实例化模板
+
+
+template< typename T, typename U, int value>
+class SuckType {
+public:
+    T a;
+    U b;
+    SuckType():a(value),b(value){}
+};
+// template< typename T>
+// typedef SuckType<std::vector<int>, T, 1> NewType; // 不合法
+
+template <typename T>
+using NewType = SuckType<int, T, 1>;                 // 合法
+
+// 默认模板类型
+template<typename T = int, typename U = int>
+auto add(T x, U y) -> decltype(x+y) {
+    return x+y;
+}
+
+// sizeof...
+template<typename... Args>
+void magic(Args... args) {
+    std::cout << sizeof...(args) << std::endl;
+}
+
+
+// 1. 递归解参数包
+template<typename T>
+void printf1(T value) {
+    std::cout << value << std::endl;
+}
+template<typename T, typename... Args>
+void printf1(T value, Args... args) {
+    std::cout << value << std::endl;
+    printf1(args...);
+}
+// 2.初始化列表展开解参数包
+template<typename T, typename... Args>
+auto printf2(T value, Args... args) {
+    std::cout << value << std::endl;
+    return std::initializer_list<T>{([&] {
+        std::cout << args << std::endl;
+    }(), value)...};
+}
+
+int main() {
+    
+    std::vector<std::vector<int>> wow;      // 注意尖括号
+    
+    NewType<int> t;
+    
+    magic();
+    magic(1);
+    magic(1,"");
+    
+    printf1(1, 2.3, "abc");
+    printf2(1, 2.3, "abc");
+    return 0;
+}