This is the source code of the Stutter language interpreter and examples presented in Gary W. Flake's book "The Computational Beauty of Nature", ISBN 978-0262561273.
Stutter is minimalist Lisp "that only understands car, cdr, cons, if,
set, equal, quote, and lambda, but is still Turing-complete" (from the
source code, stutter.c).
The *.slp files are examples written in Stutter.
The files were extracted from an archive containing other examples from the book, copied on 2011-10-29 from:
http://mitpress.mit.edu/books/FLAOH/cbnhtml/cbn-noarch-src+docs.tgz
License (from the source code, stutter.c):
AUTHOR Copyright (c) 1997, Gary William Flake.
Permission granted for any use according to the standard GNU ``copyleft'' agreement provided that the author's comments are neither modified nor removed. No warranty is given or implied.