On 3/14/07, Peter Dimov <pdimov@mmltd.net> wrote:
Braddock Gaskill wrote:
So, that would mean that for f3 = f1 || f2, if f1 propagates an exception while f2 succeeds, f3 still propagates an exception?
I think that one sensible meaning of f1 || f2 is to wait until either one of f1 or f2 returns a value, or both fail.
The "first to complete" approach is supported by my proposed future<>, but not in a composable way. You can hand the same future<> to two producers and the first one to place a value or an exception into it wins. But I haven't investigated the infrastructure that would allow operator||.
As for operator&&, it doesn't deliver any extra functionality. Instead of wating for f1 && f2, you just wait for f1, then f2:
future<int> f1 = fork( f, x ); future<int> f2 = fork( f, y );
std::cout << f1 + f2 << std::endl;
There's no need to do:
future< pair<int, int> > f3 = f1 && f2; pair<int,int> p = f3; std::cout << p.first + p.second << std::endl;
While there is no added functionality to being able to wait to two or more futures at the same time, it could improve performance: the waiting thread need to be awaken only once and you could save some context switches. gpd