detected on a bool signal. In that case, it would be easier to define it in terms of transfer:
accumIf :: a -> (a -> a) -> Signal Bool -> SignalMonad (Signal a) accumIf v0 f b = transfer v0 g b where g _dt c x0 = if c then f x0 else x0
event :: a -> Signal Bool -> (a -> a) -> SignalMonad (Signal a) event v0 b f = accumIf v0 f =<< edge b
nice
Also, your flat function is practically equivalent to (return . pure), why did you define it using transfer?
lack of reflex (and reflexion !)
Another thing to note is that you might want to define playerX as an integral of a velocity derived from lpress and rpress, so you wouldn't need to press and release the buttons repeatedly, and the speed would be the same regardless of sampling rate, since integral takes the time step into account.
or event :: a -> Signal Bool -> (a -> a) -> SignalMonad (Signal a) event v0 b f = accumIf v0 f =<< return b ?
For instance, the accumIf function is a conditional version of stateful, and it might be generally useful. Whether it's the best name, that's another question.
Gergely
thank you for your very helpful post