LibraryMaterial::print();
os << "title:" << _title
<< "author" << _author << endl;
}
AudioBook类，派生于Book类，并加入附加信息，比如旁述，音频格式等等。这些东西都用它的print函数输出。再这之前，我们需要调用Book::print()来显示前面的信息。
inline void
AudioBook::
print( ostream &os )
{
// ok, this is resolved statically,
// and therefore is inline expanded ...
Book::print();
os << "narrator:" << _narrator << endl;
}
这和虚析构函数调用链的例子一样，都只是最初调用的虚函数没有被静态决议，其它的都被原地展开。This unnamed hierarchical design pattern is significantly less effective if we never declare a virtual function to be inline.
那么对于第二个原因中代码膨胀的问题呢？我们来分析一下，如果我们写下：
LibraryMaterial *p =
new AudioBook( "Mason & Dixon",
"Thomas Pynchon", "Johnny Depp" );
// ...
p->print();
责任编辑：cyth
