revision #1: 更新第二章中已维护的代码

code/2/todo/2.8.cpp

@@ -0,0 +1,51 @@
+//
+// 2.8.cpp
+// c++1x tutorial
+//
+// created by changkun at changkun.de
+//
+// 强类型枚举
+
+#include <iostream>
+template<typename T>
+std::ostream& operator<<(typename std::enable_if<std::is_enum<T>::value, std::ostream>::type& stream, const T& e)
+{
+    return stream << static_cast<typename std::underlying_type<T>::type>(e);
+}
+
+// 如果两个都定义为 value1 和 value2，将引发重定义错误
+enum Left {
+    left_value1 = 1,
+    left_value2
+};
+enum Right {
+    right_value1 = 1,
+    right_value2
+};
+
+enum class new_enum : unsigned int{
+    value1,
+    value2,
+    value3 = 100,
+    value4 = 100
+};
+
+int main() {
+    
+    if (Left::left_value1 == Right::right_value2) {
+        std::cout << "Left::value1 == Right::value2" << std::endl;
+    }
+    
+    // 引发编译错误
+    // if(new_enum::value1 == 1) {
+    //     std::cout << "true!" << std::endl;
+    // }
+    if (new_enum::value3 == new_enum::value4) {
+        std::cout << "new_enum::value3 == new_enum::value4" << std::endl;
+    }
+    
+    std::cout << new_enum::value3 << std::endl;
+    
+    
+    return 0;
+}