PSD—a portable scheme debugger
Pertti Kellomäki · ACM SIGPLAN Lisp Pointers · 1993
Psd is a portable debugger for the Scheme language. Debugging with Psd is accomplished by instrumenting the original source program. When the instrumented program is run, it presents the user with an interactive interface that lets him or her examine and change values of variables, set breakpoints, and single step evaluation. Psd is designed to be run within GNU Emacs, which is used for displaying the current source code position.