Using Inheritance

Abstract

In the programming examples discussed up to this point, no special concepts as they exist in object-oriented systems have been used. The development of the GEO++ functionality was stimulated by a few simple rules which we already formulated in the introduction, such as: “Call every visible graphics object by its name”. It was shown that, as far as the functionality used in the examples is concerned, GEO++ may be easily formulated in traditional languages such as Fortran or Pascal (Wisskirchen, 1989). In this chapter we go a step further and discuss farther-reaching concepts, such as the use of call-backs and inheritance. As mentioned in Chap. 1, we require that subclassing can be performed for all transparent classes whose methods ar part of the functional specification of the the applications programmer’s interface. With this in mind, we allow, for example, the creation of subclasses of Group, Primitive, Attribute, Part.