lrpalmer:
Several very elegant FRP approaches are emerging, most visibly FRP.Reactive, which rely on blocking on multiple variables at once, continuing when the *first* of them is available. . . inside an unsafePerformIO, so the beautiful STM "orElse" solution is not available. The current solution is to race threads against each other, and have the one that finishes first kill the other one. This is implemented, for example, in Data.Unamb. However, our empirical tests have shown that the GHC scheduler is not *quite* good enough to handle this efficiently, and ends up introducing too much latency and nondeterminacy.
Cool! Does you IVar implementation have anything in common with previous proposals for things called IVar (or say, 'ports', http://www.cse.unsw.edu.au/~chak/haskell/ports/)? What's the background for this abstraction? -- Don