Experimenting with the Magda Language

Chapter 1 Introduction It is often thought that the languages commonly and widely used by programmers are perfect. As far the term perfect in general can not be used properly, it repre- sents the feeling, in my opinion diused, of maximum condence about reliability and completeness of the language itself and thus of the development platform. Another important issue which should be considered concerns the rules of modern market that impose and require to the developers a growing organization aimed at producing software rich in content, with few defects and quickly. Which one can be a response from the computer science research? We think that it can be methods, models and languages that press forward to the maximum software composability, safety and eciency, in order to promote the distribution of the software development in dierent teams as well as the reuse of pieces of code previously written. As already mentioned, people place great condence in the model of object-oriented programming, largely used in languages such as C++[25] and Java [28], and often ignore which may be their weaknesses, or worse, potential hidden problems. In particular, in this thesis, we look at some of the problems closely linked to the mechanisms of inheritance, with the aim of improving composability and thus facilitate code reuse. We address the issue by proposing a new language, named Magda, which we use as model to describe some of the problems and to oer possible solutions. The study and design of the Magda language, in terms of motivations, structures, metatheory, was presented in Jarek Ku smierek’s PhD thesis [2] which led also to a rst evaluable prototype. We build then on that work. Magda is proposed as an alternative language that oers possible solutions to: Limitations inherent to single inheritance and problems connected to multiple inheritance. Lack of modularity of initiation protocol (contructors). Accidental name clashes on method signatures and eld names. More precisely, this new language does not exploit the class-based paradigm of traditional object oriented programming, but it is based on the notion of mixin [7, 6, 8, 9, 10, 11, 12]. We will return on this notion in the sequel. My task was to test thoroughly a prototypical implementation of Magda, previously developed, via programming applications useful to highlight the innovative features of the language. As an important side eect, this work led to a tuning of the prototype to make it more usable and complete, as well as the redenition of the formal syntax of the language, with respect to the implementation. 5