DrawComponents.ps

import Data.Exists (Exists, mkExists, runExists)

type Circle = {x:: Int, y:: Int, r:: Int}
type Rectangle = {x:: Int, y:: Int, w:: Int, h:: Int}

drawCircle :: Circle -> String
drawCircle c = "This is a circle!"

drawRectangle :: Rectangle -> String
drawRectangle r = "This is a rectangle!"

data Component o = Component {
  data:: o,
  draw:: o -> String
}

aCircle = Component {
  data: {x: 100, y:100, r: 100},
  draw: drawCircle
}

aRectangle = Component {
  data: {x:100, y:100, w:100, h:100},
  draw: drawRectangle
}

objects :: Array (Exists Component)
objects = [
  mkExists aCircle,
  mkExists aRectangle
]

drawObject :: (Exists Component) -> String
drawObject = runExists (\(Component c) -> c.draw c.data)