On 17 October 2016 at 17:18, Sokolov Yura <funny.fal...@gmail.com> wrote: > > понедельник, 17 октября 2016 г., 18:12:59 UTC+3 пользователь Roberto Zanotto > написал: >> >> I missed the chance to comment on github... >> >> This also works for implementing futures and it's simple, type-safe and >> can be used with select: >> https://play.golang.org/p/VDT36rC5A- >> Of course the syntax is not as nice as built-in futures. > > > Roberto, no it doesn't work. > You miss possibility of filling future from several (usually, two) > concurrently running goroutines.
I'd suggest that this requirement is fairly unusual. For example, I just glanced at the C++ future implementation which suggests using std::promise::set_value to set the associated value, and that raises an exception if you try to set the value twice. If you want to make it possible, it's pretty easy: https://play.golang.org/p/YWYFSL2QTe There's another idiom I quite like for futures (when there's only one possible source of the value) putting the value back after taking it out: https://play.golang.org/p/_7p69KE_RZ Quite a while ago I wrote a blog post that leveraged that idiom to make a kind of broadcast channel: https://rogpeppe.wordpress.com/2009/12/ That technique is also applicable to having multiple values in a channel to implement a pool of available tokens. BTW here's an example of a Go package that uses the future idiom quite a bit: https://godoc.org/github.com/hashicorp/raft#ApplyFuture It doesn't seem so onerous to do something like this without needing direct support in the language (it would be easy to add a wait channel too). cheers, rog. > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
