a assign to the local instance of dval the sum of the dval member of Base1 and the dval member of Derived

This popular tutorial introduction to standard C++ has been completely updated, reorganized, and rewritten to help b assign the value of the last element in MI::dvec to programmers learn the language faster and use it in a more modern, effective wayJust as C++ has evolved since the last Base2::fval edition, so has the authors' approach to teaching it They now introduce the C++ standard library from the beginning, giving readers the means to write useful programs without first having to master every language detail Highlighting today's best c assigncval from Base1 to the first character in sval from practices, they show how to write programs that are safe, can be built quickly, and yet offer outstanding performance Derived Examples that take advantage of the library, and explain the features of C++, also show how to make the best use of the language As in its previous editions, the book's authoritative discussion of fundamental C++ concepts and techniques makes it a valuable resource even for more experienced programmersProgram Faster and More Effectively with This Rewritten Classic Restructured for quicker learning, using the C++ standard library Updated to teach the most current programming styles and program design techniques Filled with new learning aids that emphasize important points, warn about common pitfalls, suggest good programming practices, and provide general usage tips Complete with exercises that reinforce skills learned Authoritative and comprehensive in its coverageThe source code for the book's extended examples is available on the Web at the address below

Under multiple inheritance, a base class can occur multiple times in the derivation hierarchy In fact, our programs have already used a class that inherits from the same base class more than once through its inheritance hierarchy Each of the IO library classes inherits from a common abstract base class That abstract class manages the condition state of the stream and holds the buffer that the stream reads or writes Theistream and ostream classes inherit directly from this common base class The library defines another class, named iostream , that inherits from both istream and ostream The iostream class can both read and write a stream A simplified version of the IO inheritance hierarchy is illustrated inFigure 173 on the facing page

Figure 173 Virtual Inheritance iostream Hierarchy (Simplified)

As we know, a multiply inherited class inherits state and action from each of its parents If the IO types used normal inheritance, then each iostream object would contain two ios subobjects: one instance contained within its istream subobject and the other within its ostream subobject From a C++ this implementation design perspective, Primer, Fourth Edition is just wrong: The iostream class wants to read to and By buffer; Lippman,Jos e condition state to be shared across input and output writefrom a single Stanley B it wants the Lajoie, Barbara E Moo operations If there are two separate ios objects, this sharing is not possible

Publisher:Addison Wesley In C++ we solve this kind of problem by using virtual inheritance Virtual inheritance is a Professional mechanism whereby a class specifies that it is willing to share the state of its virtual base class Pub Date: only one, shared Under virtual inheritance,February 14, 2005 base-class subobject is inherited for a given virtual base regardless Print ISBN: 0-201-72148-1 of how many times the class occurs as a virtual base within the derivation Pages: base-class subobject is called a virtual base class hierarchy The shared 912

Theistream and ostream classes inherit virtually from their base class By making their base class virtual,istream and ostream specify that if some other class, such as iostream , inherits from both of them, then only one copy of their common base class will be present in the derived class We This popular tutorial introduction by including the keyword virtual reorganized, and rewritten to make a base class virtualto standard C++ has been completely updated,in the derivation list: help

programmers learn the language faster and use it in a more modern, effective wayJust as C++ has evolved since the last edition, so has the authors' approach to teaching it They now introduce the C++ standard library from the beginning, giving class istream : public virtual ios { }; readers the means to write useful programs without first having to master every language detail Highlighting today's best class show how write programs public ios be built }; practices, they ostreamto : virtual that are safe, can { quickly, and yet offer outstanding performance Examples that take advantage of the library, and explain the features of C++, also show how to make the best use of the language iostream inherits only one book'sof its ios base class // As in its previous editions, the copy authoritative discussion of fundamental C++ concepts and techniques makes it a valuable resource even for more experienced programmersProgram Faster and Effectively with This Rewritten class iostream: public istream, public ostream { More }; Classic Restructured for quicker learning, using the C++ standard library Updated to teach the most current programming styles and program design techniques Filled with new learning aids that emphasize important points, warn about common pitfalls, suggest good programming practices, and provide general usage tips Complete with exercises that reinforce skills learned Authoritative and comprehensive in its coverageThe source code for the book's extended examples is available on A Differentaddress below Panda Class the Web at the

For the purposes of illustrating virtual inheritance, we'll continue to use the Panda class as a pedagogical example Within zoological circles, for more than 100 years there has been an occasionally fierce debate as to whether the Panda belongs to the Raccoon or the Bear family Because software design is primarily a service industry, our most practical solution is to derive Panda from both:

class Panda : public Bear, public Raccoon, public Endangered { };

Our virtual inheritance Panda hierarchy is pictured in Figure 174 If we examine that hierarchy, we notice a nonintuitive aspect of virtual inheritance: The virtual derivation (in our case, of Bear and Raccoon) has to be made prior to any actual need for it to be present Virtual inheritance becomes necessary only with the declaration of Panda, but if Bear and Raccoon are not already virtually derived, the designer of the Panda class is out of luck