Anyone care to code up a Haskell implementation of this trivial interpreter for comparison: http://groups.google.co.uk/group/comp.lang.lisp/browse_frm/thread/7b1ab36f5d5cce0a/0ca59e0bfb794e07?hl=en#0ca59e0bfb794e07 -- Dr Jon D Harrop, Flying Frog Consultancy Ltd. OCaml for Scientists http://www.ffconsultancy.com/products/ocaml_for_scientists/?e