Simon Marlow

I agree that a MonadIO instance is unsafe, but I'll take your word for it that you want it anyway... Re your example, you can only cause a runtime crash...

I'm not a heavy lens user so I have no strong feelings on this, but I'd rather not take a dependency on lens. Can this be added in a separate...

It is tempting. One small difference in behaviour with this version is when the current thread receives an async exception from another thread: with your version, `left` will get the...

The remaining problem is that this still doesn't match the spec, namely ``` haskell concurrently left right = withAsync left $ \a -> withAsync right $ \b -> waitBoth a...

I've been thinking about this, and I'd really like to have the more efficient `concurrently`. Suppose `withAsync` was changed so that if it catches an `AsyncException` then it propagates it...

I've been trying to put my finger on what I'm uneasy about here. I think it is this: I don't like synchronous exceptions (e.g. `IOException`) being re-thrown asynchronously in another...

Here's what I want to do instead: - change the behaviour of withAsync: if it catches an AsyncException, then throw it to the async thread, but otherwise `cancel` the async...

Yes, I'd pretty much decided to do that, just hadn't got around to it.

I will try to fix the link for posterity, but this material was a precursor to the book that is available online here: http://simonmar.github.io/pages/pcph.html

Is this really a problem? A finished `ThreadId` will only keep alive the topmost stack chunk, which is 1KB. I'm worried the cost of fixing this "leak" could be worse...