ECSTypes.elm

type alias Entity = {
  position : Vector,
  velocity : Vector,
  scale    : Vector,
  ...
}

type alias World = List Entity
type alias ComponentCreator = Entity -> Entity

-- Actions need to also take the world as input
-- Consider collision detection for example
-- Collision depends on all other collider entities
type alias Action = Entity -> World -> Entity

position : Float -> Float -> ComponentCreator
position x y entity = 
  {entity | position <- Just (Vector x y)
  
...

moveEntity : Action 
moveEntity entity _ = 
  case (entity.position, entity.velocity) of
        (Just pos, Just vel) -> 
            entity |> position (pos.x + vel.x) (pos.y + vel.y)
        _ -> entity
        

resolveCollision : Action
resolveCollision entity world = 
  let collidingEntities = filter (collide entity) world
  in 
    case collidingEntities of 
      [] -> entity
      x :: xs -> resolveCollision (resolve entity x) xs