-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Wednesday 14 March 2007 15:26 pm, Braddock Gaskill wrote:
On Wed, 14 Mar 2007 14:09:37 -0400, Frank Mori Hess wrote:
then you should be able to do (without blocking) promise<A> p; future<A> fa(p); future<B> fb = fa;
Does libpoet already do this? Any advice on implementation? I split my future_impl from the actual value type so that I could more easily support this, but haven't worked out the details yet.
Yes. I have a future_body and a future_body_proxy class, both derived from future_body_base. A future_body handles the simple case of a future waiting on a value. A future_body_proxy observes another future_body_base and becomes ready when the future_body_base it is observing becomes ready. It then sets its value by applying a conversion function to the value from the other future_body_base. This handles implicit conversions, and conversions done with a user-specified conversion function. See the poet/future.hpp file: http://www.comedi.org/cgi-bin/viewcvs.cgi/libpoet/poet/future.hpp
-Constructing a future from another with an incompatible template type via a user-supplied conversion function. Useful for extracting future elements from future containers, for example.
I think I saw you mention this in another post, and hoped you would come back with it. Can you give me a short example of how this syntax would work that I can work towards?
I just have a constructor that takes an additional argument for the conversion function. The conversion function argument is really a boost::function<T (const U&)> . See http://www.comedi.org/projects/libpoet/classpoet_1_1future.html#a3
-Adding a promise::fulfill() that accepts a future with a compatible template type. The effect would be that promise::fulfill() would be called with the value from the future when it is ready.
So this effectively chains the future's? Ie: promise<T> p1; future<T> f1(p1); promise<U> p2; future<U> f2(p2); p2.fulfill(f1); f2.wait(); //actually waits for f1 to complete.
I think of it as chaining the promises, but yes you're understanding me correctly. - -- Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.1 (GNU/Linux) iD8DBQFF+Fqm5vihyNWuA4URAkIvAJ4pAJHA8YU+HTwoNelKFN7j31amrgCfai1j ifWPvF7GrBL8peAwCycpNGQ= =jwST -----END PGP SIGNATURE-----