prepare for c++17

code/2/2.1.cpp

@@ -0,0 +1,32 @@
+//
+// 2.1.cpp
+// c++1x tutorial
+//
+// created by changkun at shiyanlou.com
+//
+// nullptr
+
+#include <iostream>
+
+void foo(char *);
+void foo(int);
+
+int main() {
+    
+    if(NULL == (void *)0)
+        std::cout << "NULL == 0" << std::endl;  // 该行将输出
+    else
+        std::cout << "NULL != 0" << std::endl;
+    
+    foo(0);         // 调用 foo(int)
+    //foo(NULL);    // 该行不能通过编译
+    foo(nullptr);   // 调用 foo(char*)
+    
+    return 0;
+}
+void foo(char *ch) {
+    std::cout << "call foo(char*)" << std::endl;
+}
+void foo(int i) {
+    std::cout << "call foo(int)" << std::endl;
+}