Hello John, Thursday, July 21, 2005, 4:20:16 PM, you wrote:
you can either: 1) made all calls from single thread 2) put all calls in "withMVar lock", where `lock` is a global MVar
JG> OK, that makes sense. Simon Marlow has corrected me :)
JG> 1. It seems that there is no function that says "block the current JG> thread until the thread given by ThreadId dies"
GHC concurrency stuff is very basic and low-level. there is several libs which adds some more high-level abilities, including MissingH (see Child.hs) and some functions in http://www-i2.informatik.rwth-aachen.de/~stolz/Haskell/CA.hs
JG> Err, got a bit of egg on my face for that one. Would have hoped I'd JG> have remembered what's in the library I maintain ;-) it's cool :) JG> But actually, looking at it now, it's not a plain ThreadId that it waits JG> for, but rather a Child, which is: JG> data Child a = Child ThreadId (MVar a) JG> Great if you use the Child.hs (which, for the record, is one of Peter JG> Simons' works), but if somebody isn't using it, it may be nice to have JG> another option. I'll look into Simon's recipe and see if I can JG> understand it ;-) please see Child.hs sources - it uses the same technique as Simon suggested. currently there is no way to directly determine whether some thread was finished or not, all solutions add some code which is is executed after actual thread code. if you will clean Simon Marlow's code, you will get: finished <- newEmptyMVar forkIO (do_thread >>= putMVar finished) and then using `isEmptyMVar finished` in main thread to test whether the code runned by `do_thread` is done JG> FWIW, I think Python has some really great threading primitives. From a JG> brief look at what's in Haskell, I think they are all implementable in JG> terms of the low-level features Haskell has (I'll trust you all on the JG> waiting for a thread thing). I may write something up along those JG> lines, stick it in MissingH and offer it up for fptools if anyone is JG> interested. i will see, it's interesting. btw, i also make small process-related lib, but it is very narrow-purposed - it helps organizing threads into unix-fashion pipes like, for example, "reader |> modifier |> writer" -- Best regards, Bulat mailto:bulatz@HotPOP.com