A little elm program based on http://elm-lang.org/edit/examples/Intermediate/Physics.elm

gistfile1.txt

---- Put it together and show it ----

main = lift3 presentation sunAndEarth bouncingBall sineGraph

presentation figure1 figure2 f3 =
  flow down [ figure1, figure2, f3 ]


-- Signal.foldp : (a -> b -> b) -> b -> Signal a -> Signal b
-- Text.asText : a -> Element
-- Signal.lift : (a -> b) -> Signal a -> Signal b
-- Time.fps : number -> Signal Time
-- Signal.lift2 : (a -> b -> c) -> Signal a -> Signal b -> Signal c

---- Text ----


---- Diagrams ----

time = lift (inSeconds . fst) (timestamp (fps 20))

sunAndEarthAt angle =
  let earth = group [ filled lightBlue (circle 20), toForm (plainText "Earth") ]
      sun = group [ filled lightYellow (circle 35), toForm (plainText "Sun") ]
  in  collage 300 200
        [ earth |> move (120 * cos angle, 80 * sin angle)
        , sun   |> move (25,0), toForm (asText angle) |> move (50,-90)]

sunAndEarth = lift sunAndEarthAt time

bouncingBallAt angle =
  let ball = filled red (circle 15)
      ground = filled green (rect 300 50)
  in  collage 300 200
          [ ball   |> move (0, abs (150 * sin angle) - 75),
            ground |> move (0,-100) ]

bouncingBall = lift bouncingBallAt time

bounds w h = { 
  center = (0,0), top = h / 2, right = w / 2,
  topRight = (round <| w / 2, round <| h / 2), bottonLeft = (round <| -w / 2, round <| -h / 2),
  width = round <| w + 2, height = round <| h + 2 }
  
b = bounds 302 302
  
colWithBounds b = collage b.width b.height

lineColor c = { defaultLine | width <- 3, color <- c } 

toDegrees : Float -> Int
toDegrees x = round <| 180 * x / pi

formText = toForm . asText

sine t = 
  let y = b.top * sin t
      x = b.right * cos t
      s = (b.right,y)
      c = (x,-b.top)
      cs = (x,y)
      angle = toDegrees <| (\x -> (x/1000)) 
        <| toFloat <| rem (round (1000*(t - pi/2))) (round (2000 * pi))
  in colWithBounds b [ 
    segment (0,0)    cs |> traced (lineColor red),
    segment (0,-150) c  |> traced (lineColor green),
    segment (150,0)  s  |> traced (lineColor blue),
    segment (-150,0) (150,0) |> traced (solid black),
    segment (0,-150) (0,150) |> traced (solid black),
    move (10, 75) <| formText <| angle ]
  
sineGraph = lift sine time

d'oh... integer division give me the angle, d'oh