sjoerd at w3future.com
Fri Jun 15 15:43:24 CEST 2012
> > An alternative, equivalent interface for waitEither and friends would be
> > waitEither :: Async a -> Async a -> IO (Either SomeException a)
> > waitEitherThrow :: Async a -> Async a -> IO a
> > This might be conceptually simpler, leaving it to the user to decide
> > whether to mark the results with Left/Right, or something else, or not.
> > Similarly the Async now returned by waitAny and friends could be left
> > to the user. That would leave the two sets of functions more in line.
> I liked this suggestion at first, but later concluded that it isn't
> as nice. The problem is that to convert an 'Async a' to an 'Async
> (Either a b)' has to be done when you create the Async in the first
> place, or else you have to write some STM code to lift the result.
> If you're writing some STM code anyway, then there's little point in
> using waitEither.
What's the problem with converting when you create the Async?
> withAsync (Left <$> getUrl url1) $ a1 -> do
> withAsync (Right <$> getUrl url2) $ a2 -> do
> waitEither a1 a2
This seems more explicit to me. And if you really don't care which of
the results you want, they'll probably have the same type anyway.
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