Modularizing Language Constructs: A Reflective Approach

Programming languages are in a continuous state of flux in order to keep up with emerging needs of programmers. They are grown with new constructs so that programmers can express the problems from their domain within the language they are using. Growing languages means to grow their implementations along with them. To support this, we wish to preserve the decomposition of languages into language constructs in their implementations. As the design of a language implementation directly reflects our intuitive decomposition, a developer can engage in the natural process of developing a language. We preserve the decomposition into language constructs by modularizing the definition of language constructs in separate implementation modules containing their syntactical representation and their translational semantics. In this setting, growing a language boils down to writing or selecting the appropriate language constructs and establishing the necessary interactions. As the language is continuously evolving during its implementation and future evolutions, the modularization of the language constructs renders the implementation less susceptible to the continuous changes. The modularization of language implementations has been the subject of much research in the domain of compiler technology. The complexity of this research lies in the fact that language constructs intrinsically take into account other language constructs and therefore compromise their opportunities for modularization. Indeed, the mechanisms presented by the contemporary state of the art technologies for separating a language implementation into modules do not suffice. In this dissertation, we define a lightweight formal model for the modularization of language constructs. From this model we deduce a new language implementation design in which languages consists of three kinds of concerns: the basic language concerns defining the language constructs, the language specification defining the interactions between the basic concerns by using the special-purpose concerns which define the mechanisms to implement the interactions. As a solution for the above model, we present an open design for a new lan-