revision #1: 更新第二章中已维护的代码

code/2/2.1.nullptr.cpp

@@ -0,0 +1,34 @@
+//
+// 2.1.nullptr.cpp
+// chapter 2 language usability
+// modern cpp tutorial
+//
+// created by changkun at changkun.de
+//
+
+#include <iostream>
+#include <type_traits>
+
+void foo(char *);
+void foo(int);
+
+int main() {
+    if (std::is_same<decltype(NULL), decltype(0)>::value)
+        std::cout << "NULL == 0" << std::endl;
+    if (std::is_same<decltype(NULL), decltype((void*)0)>::value)
+        std::cout << "NULL == (void *)0" << std::endl;
+    if (std::is_same<decltype(NULL), std::nullptr_t>::value)
+        std::cout << "NULL == nullptr" << std::endl;
+
+    foo(0);          // will call foo(int)
+    // foo(NULL);    // doen't compile
+    foo(nullptr);    // will call foo(char*)
+    return 0;
+}
+
+void foo(char *) {
+    std::cout << "foo(char*) is called" << std::endl;
+}
+void foo(int i) {
+    std::cout << "foo(int) is called" << std::endl;
+}