Chapter 12, Simple Shapes

[mkohlhaas]

-- The void function takes a functor and replaces its value with Unit.
-- In the example, it is used to make main conform with its signature.
main :: Effect Unit
main = void $ unsafePartial do
  Just canvas <- getCanvasElementById "canvas"
  ctx <- getContext2D canvas

main :: Effect Unit
main = unsafePartial do
  Just canvas ← getCanvasElementById "canvas"
  ctx ← getContext2D canvas
  setFillStyle ctx "#00F"
  fillPath ctx $ rect ctx
    { x: 250.0
    , y: 250.0
    , width: 300.0
    , height: 100.0
    }

void is not needed in this case b/c rect has already the desired result type:

fillPath :: ∀ a. Context2D → Effect a → Effect a
rect :: Context2D → Rectangle → Effect Unit

Similar in other examples. void is only needed in Example.LSystem.