pgl@cup.portal.com (Peter G Ludemann) (12/01/89)
Not in Lisp or Scheme put possibly useful: "Unification-based Conditional Binding Constructs" by Harvey Abramson, Proceedings of the 1st International Logic Programming Conference, Marseilles: Sept. 14-17, 1982 (also UBC CompSci TR 82-7) "A Prological Definition of HASL a Purely Functional Language with Unification Based Conditional Binding Expressions" by Harvey Abramson (University of British Columbia Computer Science TR 83-8) (also published but I don't recall where right now -- if you're interested, send me a note) The latter contains a complete Prolog program.