Copyright 2015 William D Clinger.

Permission to copy this software, in whole or in part, to use this
software for any lawful purpose, and to redistribute this software
is granted subject to the restriction that all copies made of this
software must include this copyright and permission notice in full.

I also request that you send me a copy of any improvements that you
make to this software so that they may be incorporated within it to
the benefit of the Scheme community.
