On Thu, 24 Apr 2008 12:57:56 +0200, apfelmus wrote: > there is also the option of collapsing ReadOnlySTM a and STM a > by changing the semantics of writeTVar . > > I mean, writeTVar can be used for two different things: > > 1) communicate with other threads, i.e. crossing > atomically boundaries > 2) communicating inside a single thread/STM action > à la mutable state (IORef). > > We only want 1), but 2) is expendable, we can always use parameters to > pass state around or wrap the whole thing into a state monad. For 1), > it's enough to have a primitive > > scheduleWriteTVar :: TVar a -> a -> STM () > > that ensures to write the TVar at the very end of the atomically block.
Unfortunately, though, this breaks the very thing that makes STM attractive: namely, composability. Now in order to work with a TVar, I need to know whether anything that came before me might have modified it, and if so take the current value as a parameter instead of reading it like normal. Or am I misunderstanding something? -- Chris Smith _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
