Inheriting from a Common Abstract Ancestor in Timor.

Abstract

A particular case of multiple inheritance, involving a family of related types with a common abstract ancestor, is examined, and a substantial example, involving five abstract and nine concrete collection types, is presented. The separation of types and implementations, together with the separation of subtyping and code re-use, results in a clearly structured and easily intelligible type library which allows extensive polymorphic use of collections at the type level. A full implementation of only one of these types, together with a few additional trivial code units, can be re-used to implement all nine concrete types. The paper concludes by describing how the binary methods and constructors can also be easily and efficiently designed and implemented.

Persistent Objects and Capabilities in Timor.

“…In contrast with the conventional OO class construct, Timor distinguishes between type definitions and their implementations [11][12][13]. A Timor type definition (introduced by the keyword type) can have several implementations (introduced by the keyword impl) and it is possible that different instances of the same type can have different implementations, even within a single program.…”

Statically Qualified Types in Timor.

“…However, we consider it inappropriate to define a Set in terms of a Bag, inter alia because it would result in considerable restrictions from the viewpoint of polymorphism when compared to the definition given in [4]. As that paper illustrates, Set is better defined as part of a more comprehensive collection hierarchy based on the combining of orthogonal properties, as this creates more opportunities to take advantage of subtyping.…”

“…[4]), the entire duplicate-free types in the TCL can easily be implemented with re-use variables of DuplControlling's implementations, as follows: The qualifiers DuplIgnore and DuplSignal are not marked as re-use variables (with the ^ symbol) because they have no instance methods which are re-used to match the interface definitions of the types being defined.…”

“…A simpler version of the qualifier's first implementation, which might simply update the current sum before or after invoking body without ensuring (by comparing the 4 The conventional iterator technique has been modified slightly for reasons which will be discussed in a future paper. Using the conventional technique would also require access to base.…”

“…In [4] a different, more complicated technique was used to implement the duplicate free types of the TCL. In view of the relative simplicity of the above examples, which J OURNAL OF OBJECT TECHNOLOGY V OL.…”