On Fri, Apr 05, 2013 at 08:36:51AM -0400, Chris K. Jester-Young wrote:
> > The clarity of this code could greatly benefit from some helper
> > procedures.  One possibility would be a procedure that takes a promise
> > and two continuation arguments: one to call if the promise has already
> > been computed, and another to call if it has not yet been.  Another
> > possibility would be to simply have a predicate that tells whether a
> > promise has already been computed.
> 
> I was actually mimicking the style used in the SRFI 45 reference
> implementation of delay. If we change this here, we should also
> correspondingly change delay. The two continuations thing is probably
> worth trying.

Attached is a patch for implementing this. Whether this results in
"greatly benefitted clarity" is debateable, but it was worth a try. :-)

Cheers,
Chris.