Miguel Negrao wrote:
Thanks for the explanation. I was wondering, how would one translate this Yampa code into reactive-banana:
fallingBall :: Pos -> Vel -> SF () (Pos, Vel) fallingBall y0 v0 = proc () -> do v <- (v0 +) ˆ<< integral -< -9.81 y <- (y0 +) ˆ<< integral -< v returnA -< (y, v)
fallingBall’ :: Pos -> Vel -> SF () ((Pos,Vel), Event (Pos,Vel)) fallingBall’ y0 v0 = proc () -> do yv@(y, _) <- fallingBall y0 v0 -< () hit <- edge -< y <= 0 returnA -< (yv, hit ‘tag‘ yv)
bouncingBall :: Pos -> SF () (Pos, Vel) bouncingBall y0 = bbAux y0 0.0 where bbAux y0 v0 = switch (fallingBall’ y0 v0) $ \(y,v) -> bbAux y (-v)
Would it be possible to do this without dynamic event switching ? What about with the new event switching in v0.7 ? Also, is it possible (and is it easy ?) to do looping such as it is done in Yampa using the the loop arrow in reactive-banana/classic FRP ?
The Animation.hs example may help http://www.haskell.org/haskellwiki/Reactive-banana/Examples#animation Essentially, the main difference is that reactive-banana doesn't have functions like integral or edge because they depend on an implicit time step. In reactive-banana, you have to manage time yourself, for instance by making a timer event from a wxTimer. To calculate velocity and position, you can you use accumE on the timer event. To do collision detection, you can check whether the ball will move below the floor at each time step. Dynamic event switching is not needed here. For a more complex example, have a look at Andreas Bernstein's paddle ball game https://github.com/bernstein/breakout Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com