Drscheme: A pedagogic programming environment for scheme

Abstract

Teaching introductory computing courses with Scheme elevates the intellectual level of the course and thus makes the subject more appealing to students with scientific interests. Unfortunately, the poor quality of the available programming environments negates many of the pedagogic advantages. To overcome this problem, we have developed DrScheme, a comprehensive programming environment for Scheme. It fully integrates a graphics-enriched editor, a multi-lingual parser that can process a hierarchy of syntactically restrictive variants of Scheme, a functional read-eval-print loop, and an algebraically sensible printer. The environment catches the typical syntactic mistakes of beginners and pinpoints the exact source location of run-time exceptions. DrScheme also provides an algebraic stepper, a syntax checker and a static debugger. The first reduces Scheme programs, including programs with assignment and control effects, to values (and effects). The tool is useful for explaining the semantics of linguistic facilities and for studying the behavior of small programs. The syntax checker annotates programs with font and color changes based on the syntactic structure of the program. It also draws arrows on demand that point from bound to binding occurrences of identifiers. The static debugger, roughly speaking, provides a type inference system with explanatory capabilities. Preliminary experience with the environment shows that Rice University students find it helpful and that they greatly prefer it to shell- or Emacs-based systems.