UnicStep-a visual stepper for COMMON LISP: portability and language aspects

Abstract

This article presents a visual stepper for Common Lisp with simple backup feature. The stepper is based on Lieberman's approach for visual stepping. The stepper operates at the source level of programs and uses the GNU Emacs editor for source code processing. Problems encountered on implementing this stepper are described: read-syntax, macroexpansion, and source-localization. Especially, language features are discussed which affected our goal to make this tool portable across Common Lisp systems.