By the way, since we are again discussing this srfi, I have to say I
think it was a mistake to make streams a separate type from other
promises, for the following reasons:

- It ascribes truth to false statements.  For example,

     (stream? (stream-delay 'not-a-stream))  ==> #t (this is wrong)

   This shows that the result of stream-delay should be a promise,
   not a stream.

- It prevents reuse of the implementation's primitive {delay, force, lazy}.
   These have to be redone especially for streams, as the presence of
   "stream-promise" in srfi-40:force shows.

Andre