Data Abstraction Mechanisms in Sina/st

This paper describes a new data abstraction mechanism in an object-oriented model of computing. The data abstraction mechanism described here has been devised in the context of the design of Sina/st language. In Sina/st no language constructs have been adopted for specifying inheritance or delegation, but rather, we introduce simpler mechanisms that can support a wide range of code sharing strategies without selecting one among them as a language feature. Sina/st also provides a stronger data encapsulation than most of the existing object-oriented languages. This language has been implemented on the SUN 3 workstation using Smalltalk

Multiple dispatch in practice

Multiple dispatch uses the run time types of more than one argument to a method call to determine which method body to run. While several languages over the last 20 years have provided multiple dispatch, most object-oriented languages still support only single dispatch — forcing programmers to implement multiple dispatch manually when required. This paper presents an empirical study of the use of multiple dispatch in practice, considering six languages that support multiple dispatch, and also investigating the potential for multiple dispatch in Java programs. We hope that this study will help programmers understand the uses and abuses of multiple dispatch; virtual machine implementors optimise multiple dispatch; and language designers to evaluate the choice of providing multiple dispatch in new programming languages

New Inheritance Models That Facilitate Source Code Reuse in Object-oriented Programming

Code reusability is a primary objective in the development of software systems. The object-oriented programming methodology is one of the areas that facilitate the development of software systems by allowing and promoting code reuse and modular designs. Object-oriented programming languages (OOPLs) provide different facilities to attain efficient reuse and reliable extension of existing software components. Inheritance is an important language feature that is conducive to reusability and extensibility. Various OOPLs provide different inheritance models based on different interpretations of the inheritance notion. Therefore, OOPLs have different characteristics derived from their respective inheritance models. This dissertation is concerned with solutions for three major problems that limit the utilization of inheritance for code reusability. The range of object -oriented applications and thus the usage of object-oriented programming in general is also discussed. The three major problems are: 1) the relationship between inheritance and other related issues such as encapsulation, access techniques, visibility of inheritance, and subtyping; 2) the hierarchical structure imposed by inheritance among classes; and 3) the accessibility of previous versions of the modified methods defmed in classes located at higher levels of the inheritance structure than the parent classes. 1be proposed solutions for these problems are presented as new inheritance models that facilitate code reuse and relax the restrictions imposed on inheritance models by languages. A survey and taxonomy of the conventional inheritance models, and a comparison and analysis of some of the common OOPLs are also presented in the dissertation.Computer Scienc