Trying out a Scheme solution for this problem (), and it errored out on filter. My version of Gambit (Windows x64, 4.9.3) does not have filter. Steve -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mailman.iro.umontreal.ca/pipermail/gambit-list/attachments/20191205/0d977bf3/attachment.htm>