Quoth Jason Dagit
Yes. From my perspective (that of a library writer) that's what makes this tricky in GHCi. I need GHCi's cooperation. From GHCi's perspective it's tricky too.
It seems to me that ideally, GHCi would do its thing in a child thread, like the extra runtime threads, and let the program execute in the main thread, as in a compiled program. I mean, ideal from the point of view of supporting the general case of library functions that care what the main thread is doing. I'm not saying that's possible - have no idea - but just that where you're dealing with a possibly unconscious and probably poorly documented expectation like that, it's better to not break it in the first place, than to have to try to patch it up at run time. I have been wondering while reading this thread if my Haiku API functions are subject to this restriction - there is an application object that normally runs in main() - but while that would be easy to verify empirically, it wouldn't really tell me what I need to know. A subsequent OS release could easily introduce some thread sensitivity, and I guess if my Haskell programs must run from a child thread under certain circumstances, even if I could make them work I would have to consider that success temporary and provisional. Donn