Semantic analysis of virtual classes and nested classes

Abstract

Virtual classes and nested classes are distinguishing features of BETA. Nested classes originated from Simula, but until recently they have not been part of main stream object- oriented languages. C++ has a restricted form of nested classes and they were included in Java 1.1. Virtual classes is the BETA mechanism for expressing generic classes and virtual classes is an alternative to parameterized classes. There has recently been an increasing interest in virtual classes and a number of proposals for adding virtual classes to other languages, extending virtual classes, and unifying virtual classes and parameterized classes have been made. Although virtual classes and nested classes have been used in BETA for more than a decade, their implementation has not been published. The purpose of this paper is to contribute to the understanding of virtual classes and nested classes by presenting the central elements of the semantic analysis used in the Mjølner BETA compiler. © 1999 ACM.