(as Mathew notes as a bug) any value can be raised
* Actually use an applicable struct, so we can printout something
sensible. The current printout is:
#<promise!exn!...exn-message...> for exceptions
#<promise!(raise val)> for other values
svn: r10423
nested streams example (from Jos Koot).
* Replaced with `call-with-exception-handler' which is (intentionally)
not tail-recursive, but it seems to work fine now.
* The `lazy' form is restricted to single-valued expressions only.
svn: r10416
