Activity simulation in Modula-2: An exercise in language extension

Discrete event simulation modelling is enhanced by the provision of adequate modelling tools to assist the programmer in defining the entities of a system, their interrelationships and how they interact over time. Several methodologies exist. We develop a high level language for the activity approach in this paper. A promising approach to developing an appropriate programming language for any application area is to adapt existing languages by restriction and extension to fit in with the problem environment. In this case, we adapt Modula-2 by several extensions to this specific domain. By this means, programmers already familiar with Modula-2 will be encouraged to design simulation models using features more suited to this task than by programming in the non-problem specific features available in basic Modula-2. The idea of creating a hierarchy of programming languages has been proposed as the ideal language design mechanism by Bailes. The justification for this approach is the conceptual parallels between programming and language design, and the way in which programmer defined constructs are in practice not distinguished from those provided as part of the programming language