Language Prototyping in GLoo

Rapid prototyping is a viable engineering technique to explore and validate desirable system characteristics of software products in a flexible and agile manner. Dynamic programming languages with their emphasis on developer productivity and software quality provide a good fit for the required programming approach. However, with the exception of Scheme or Smalltalk, these languages are seldom used to study programming language concepts. In this paper, we explore GLoo, a small open-ended dynamic programming language, whose design philosophy aims at an unified approach in which program and language evolution result directly from the definition of ”extensible domain sub-languages”. Surprisingly, these domain sub-lanuages do not only provide a high-level tool to capture domain expertise, but give also rise to a powerful compositional model for language extension. To demonstrate their effectiveness, we present the underlying concepts and illustrate their application by defining a GLoo model for object-oriented and class-based language extensions. We also demonstrate that the concept of composable parsers, in combination with open contexts, plays a crucial role in achieving the resulting flexibility and expressiveness.