c++ 继承

单继承                                                              多继承

class ImageBook：public Book {  }                 class ImageBook： public Book， public Image  {             }；

virtual inheritance ：//li例子如下

class 　Book ：virtual public Paper {  };

class   Image : virtual  public Paper {  }

 class ImageBook： public Book， public Image  {             }；// 只会出现一个 Paper 几类 ，使用virtual 继承的话

only a single occurrence of the base class is maintained (called a
subobject) regardless of how many times the class is derived from within the inheritance chain