An implicitly-declared default constructor is an inline publicmember of its class.
一个隐式声明的构造函数是这个类的一个内联公有成员。
2
If neither of the two is defined, the compiler provides an implicit version that is a publicmember function.
如果二者都未定义,那么编译器会提供一种作为公共成员函数的隐式版本。
3
This example shows the C++ source code that contains a non-class function, a Private member function of a class, and a Publicmember function of a class.