A different kind of programming languages course

The complexity of the well-explored regions of the programming language design space has increased substantially in the last twenty-five years with the addition of a large number of object-oriented programming languages (OOPLs). This design domain was already known to be large and complex before OOPLs came on the scene, and many offerings of the standard programming languages course before that time did not even mention the object-oriented programming (OOP) paradigm. Now that OOP has become mainstream, undergraduate programs which include a course on programming language design and implementation have responded by expanding their existing course or by jettisoning some of the alternative ideas in favor of expanded coverage of OOPLs. There are two facts, however, which must be confronted as we consider what information we would like to pass on to our students in this fascinating area of our discipline. The first is that the design space represented by OOPLs is large enough to justify a separate course, and the second is that a large number of ideas from other language paradigms appear in subsets of well-known languages for OOP. This paper presents a course in the design and implementation of programming languages that (as OOP itself did in the late eighties) turns some accepted notions "inside out" by proposing that the entire course be presented from the OOP point of view. Such a course has been offered by Grove City College for a decade and has matured into a very effective means of communicating essential programming language design and implementation ideas to our students. The course could be offered as the only advanced course in the area, as one course in a two-semester sequence, or as an alternative to the traditional course.