Haskell's missing mutable reference type

michaelpj:

modifications to an IOScopedRef in one thread would not be observed by another thread

Do you mean any other thread, or would child threads see it?

I mean any thread, not even child threads.

michaelpj:

I’m pretty sure that’s what you would want, otherwise your logging example gets very annoying as soon as you do any concurrency inside a modification block.

I’m skeptical. Can you share an example?