On 2/26/2011 5:06 AM, Barton Willis wrote: > I thought this was fun; maybe it is useful too. Could be useful. A more ambitious approach is via overloaded ops as in http://www.cs.berkeley.edu/~fateman/generic . You could also make lisp programs into symbolic programs by replacing (+ a b) by (list '(mplus) a b) etc. :) RJF