Today we were working on integrating Atom code with some hand-written C, and one of my colleagues posed the question: Is it possible to use Atom just for its task scheduler for existing C code? This turns out to be very simple. It just requires a few combinators built on top of 'action'. -- Call a C function with type 'void f(void)'. call :: Name -> Atom () call n = action (\ _ -> n ++ "()") [] -- Call a C function in its own rule, atomically. callAtomic :: Name -> Atom () callAtomic n = atom n $ call n -- Call a C function atomically with a guard condition. callGuardedAtomic :: E Bool -> Name -> Atom () callGuardedAtomic g n = atom n (cond g >> call n) Then scheduling a collection of tasks becomes easy: -- 20 millisecond tasks. period 20 $ do callAtomic "task1" callAtomic "task2" -- 5 millisecond tasks. period 5 $ do callAtomic "task3" callAtomic "task4" -- 1 millisecond tasks. period 1 $ do callGuardedAtomic task5Ready "task5" callGuardedAtomic task6Ready "task6" I'll added these 'call' combinators in the next release of Atom.