Talk Topic: From Scripts to Programs
Matthias Felleisen, Northeastern University
June 18, 2008

Abstract
Like it or not, dynamically typed scripting languages are far more popular than programming languages that originate in academic laboratories. Most scripting languages are untyped and have a flexible semantics for primitive operations. A lot of programmers find these attributes appealing and use scripting languages for just these reasons. Reflective programmers are also beginning to notice, however, that when small untyped scripts grow old (and/or large), maintaining them becomes difficult. A lack of types means that programmers must (re)discover critical pieces of design information every time they wish to change or improve a program.

My team and I have therefore embarked on a research program that aims to solve this large and growing engineering problem with a combination of experience and tools from academic programming language research. In this talk I will present the first milestone: Typed Scheme, an explicitly typed extension of PLT Scheme, an untyped scripting language. Using Typed Scheme, programmers can add types to a code base on a module by module basis. Two factors make such transformations straightforward and useful. First, the type system is highly flexible, combining numerous academic results with the novel notion of occurrence typing. Second, the type system uses Findler's higher-order contracts to make the integration of typed and untyped modules safe.

Collaborators: Sam Tobin-Hochstadt, Ryan Culpepper

Bio
Matthias Felleisen is currently a Trustee Professor at Northeastern University. He joined its College of Computer and Information Science in 2001, after a 14-year career at Rice University in Houston with sabbaticals at Carnegie Mellon University in Pittsburgh and École Normale Supérieure in Paris. He received his Ph.D. from Daniel P. Friedman in 1987.

Felleisen's research career consists of two distinct 10-year periods. For the first ten years, he focused on the semantics of programming languages and its applications. His work on operational semantics has become one of the standard working methods in programming languages. For the second ten years, Felleisen and his research group (PLT) developed a novel method for teaching introductory programming, including a new approach to program design and a programming environment for novice programmers (Dr. Scheme). This environment has become a popular alternative to the conventional set of teaching tools and is now used at a couple of hundred colleges and high schools around the world. For Felleisen and his team, the construction of a large, realistic software application has posed many interesting and challenging research problems in programming languages, component programming, software contracts, and software engineering.

Over the past 20 years, Felleisen has published several dozen research papers in scientific journals, conferences, and magazines. In addition, he has co-authored five books, including How to Design Programs and The Little LISPer (now called The Little Schemer), which, at the age of 35, is one of the oldest continuously published books in the field.