see #2: move non-type template param auto to ch02

code/2/2.15.variadic.template.param.cpp

@@ -0,0 +1,46 @@
+//
+// 2.15.variadic.template.param.cpp
+// chapter 2 language usability
+// modern cpp tutorial
+//
+// created by changkun at changkun.de
+//
+
+#include <iostream>
+#include <vector>
+#include <string>
+
+// sizeof...
+template<typename... Ts>
+void magic(Ts... args) {
+    std::cout << sizeof...(args) << std::endl;
+}
+
+
+// 1 recursive parameter unpack
+template<typename T0>
+void printf1(T0 value) {
+    std::cout << value << std::endl;
+}
+template<typename T, typename... Ts>
+void printf1(T value, Ts... args) {
+    std::cout << value << std::endl;
+    printf1(args...);
+}
+
+// 2 variadic template parameter unfold
+template<typename T0, typename... T>
+void printf2(T0 t0, T... t) {
+    std::cout << t0 << std::endl;
+    if constexpr (sizeof...(t) > 0) printf2(t...);
+}
+
+int main() {
+    magic();
+    magic(1);
+    magic(1,"");
+    
+    printf1(1, 2, "123", 1.1);
+    printf2(1, 2.3, "abc");
+    return 0;
+}