Actor.hs

module Actor where

-- | 2D position on the screen.
type Position   = (Float, Float)

-- | Force and velocity vectors.
type Force      = (Float, Float)
type Velocity   = (Float, Float)

-- | Time in seconds
type Time       = Float

-- | Radius of a bead
type Radius     = Float

-- | Each actor has its own unique index.
type Index      = Int

-- | The actors in the world.
data Actor
        = Wall  !Index          -- ^ unique index of this actor
                !Position       -- ^ wall starting point
                !Position       -- ^ wall ending point

        | Bead  !Index          -- ^ unique index of this actor 
                !Int            -- ^ whether the bead is stuck
                !Radius         -- ^ radius of bead
                !Position       -- ^ position of bead
                !Velocity       -- ^ velocity of bead

        deriving Show

-- | Equality and ordering of actors will consider their index only.
--      We need Ord so we can put them in Maps and Sets.
instance Eq Actor where
 a1 == a2       = actorIx a1 == actorIx a2
        
instance Ord Actor where
 compare a1 a2  = compare (actorIx a1) (actorIx a2)

-- | Check whether an actor is a bead.
isBead :: Actor -> Bool
isBead (Bead _ _ _ _ _) = True
isBead _                = False


-- | Check whether an actor is a wall.
isWall :: Actor -> Bool
isWall (Wall _ _ _)     = True
isWall _                = False


-- | Take the index of an actor
actorIx :: Actor -> Index
actorIx actor
 = case actor of
        Wall ix _ _     -> ix
        Bead ix _ _ _ _ -> ix


-- | Set the index of an actor
actorSetIndex :: Actor -> Index -> Actor
actorSetIndex actor ix
 = case actor of
        Bead _ m r pos vel      -> Bead ix m r pos vel 
        Wall _ p1 p2            -> Wall ix p1 p2


-- | Set whether a bead is stuck
actorSetMode :: Int -> Actor -> Actor
actorSetMode m (Bead ix _ r p v)
        = Bead ix m r p v