Scheme language standardization process
On 06/12/2012 12:07 PM, John Cowan wrote: > Per Bothner scripsit: > >> (Though a future version of Kawa might optimize (delay 4) to 4, >> that's OK, since I can't think of a use case for you needing >> the delay to evaluate specifically to a promise.) > > As I keep saying, the use case is to be able to write procedures that > are guaranteed to return a promise that the caller may safely force. > The only way to accomplish this in the presence of insta-forcing is > to require `force` to return its argument if it is not a promise. Certainly: If you have automatic forcing, then I'm pretty sure you want force to be a no-op when passed a non-promise. And definitely if you allow optimizing (delay 4) to 4. Kawa does this: (force (+ 4 5)) ==> 9 -- --Per Bothner per@x http://per.bothner.com/ _______________________________________________ Scheme-reports mailing list Scheme-reports@x http://lists.scheme-reports.org/cgi-bin/mailman/listinfo/scheme-reports