Debug output of game objects in Haskell / Yampa and HOOD

Question

I am stuck in generating debug output for my game objects using Haskell / Yampa (= Arrows) (with HOOD).

My engine basically launches a list of game objects that produce output states (line, circle), which are then displayed.

data Output = Circle Position2 Double | Line Vector2

output :: [Output] -> IO ()
output oos = mapM render oos

render :: Output -> IO ()
render (Circle p r) = drawCircle p r
render (Line   vec) = drawLine (Point2 0 0) vec

The player’s object simply moves to the right and appears as a (located) circle.

playerObject :: SF () Output -- SF is an Arrow run by time
   p <- mover (Point2 0 0) -< (Vector2 10 0)
   returnA -< (Circle p 2.0)

mover is just a simple integrator (acceleration position-> speed->), where I want to observe the speed and output it as a result of debugging as a (non-positional) line.

mover :: Position2 -> SF Vector2 Position2
mover position0 = proc acceleration -> do
    velocity <- integral -< acceleration -- !! I want to observe velocity
    position <- (position0 .+^) ^<< integral -< velocity
    returnA -< position

How to create additional graphical debug output for internal values ​​of functions of my game objects?

, (), ( ). , HOOD, Haskell , HOOD .

Answer 1

HOOD, Debug.Trace :

> import Debug.Trace
> mover position0 = proc acceleration -> do
> > velocity <- integral -< acceleration
> > position <- trace ("vel:" ++ show velocity ++ "\n") $
> > > > > > > > > > > (position0 .+^) ^<< integral -< velocity
> > returnA -< position

, , .

Answer 2

, , , , - mover , ( velocity) . , HOOD , FRP . .

- :

mover :: Position2 -> SF Vector2 (Position2, Vector2)
mover position0 = proc acceleration -> do
    velocity <- integral -< acceleration -- !! I want to observe velocity
    position <- (position0 .+^) ^<< integral -< velocity
    returnA -< (position, velocity)

playerObject :: SF () [Output]
   (p, v) <- mover (Point2 0 0) -< (Vector2 10 0)
   returnA -< [Circle p 2.0, Line v]