Helm Translate

translate.hs

{-
- Haskell experiment with functional reactive programming game engine Helm. 
- just a basic square with x position and speed property, translating on the x axis.
-
- run:
- ghc translate.hs
- ./translate
-}

module Main where

import FRP.Helm
import qualified FRP.Helm.Time as Time
import qualified FRP.Helm.Window as Window

data Box = Box { x :: Double, speed :: Double }

update :: Time -> Double -> Double
update dt n = n + Time.inSeconds dt

translate :: Double -> Box -> Box
translate _x _box = _box { x = ( speed _box * _x ) }

render :: Double -> (Int, Int) -> Element
render delta (w, h)  = collage w h [ move ( x $ translate delta initialBox, 225 ) $ rotate ( angle ) $ filled red $ square 64 ]
    where
        angle = delta * 12
        initialBox = Box { x = 0, speed = 50 * delta }

main :: IO()
main = do
        engine <- startup config
        run engine $ render <~ stepper ~~ Window.dimensions engine
    where
        config  = defaultConfig { windowTitle = "Translate",
                                  windowDimensions   = (650, 450),
                                  windowIsFullscreen = False,
                                  windowIsResizable  = True
                                }
        stepper = foldp update 0 $ Time.delay $ Time.fps $ 60