revision #1: 更新第二章中已维护的代码

code/2/todo/2.xxx.cpp

@@ -0,0 +1,21 @@
+#include <iostream>
+
+template<typename T0>
+void printf(T0 value) {
+    std::cout << value << std::endl;
+}
+template<typename T, typename... Args>
+void printf(T value, Args... args) {
+    std::cout << value << std::endl;
+    printf(args...);
+}
+
+template<typename T0, typename... T>
+void printf_short(T0 t0, T... t) {
+    std::cout << t0 << std::endl;
+    if constexpr (sizeof...(t) > 0) printf(t...);
+}
+int main() {
+    printf_short(1, 2, "123", 1.1);
+    return 0;
+}