Direction

direction.hs

entity2order :: Ant -> Point -> [Order]
entity2order a food = let xant = snd.point $ a
                          yant = fst.point $ a
                          xfood = snd food
                          yfood = fst food
                          in case compare xant xfood of
                                  GT -> map (Order a) (directionClockWise West)
                                  LT -> map (Order a) (directionClockWise East)
                                  EQ -> case compare yant yfood of
                                             GT        -> map (Order a) (directionClockWise North)
                                             otherwise -> map (Order a) (directionClockWise South)

direction_clock.hs

int2dir x | x `mod` 4 == 0 = North
          | x `mod` 4 == 1 = East
          | x `mod` 4 == 2 = South
          | x `mod` 4 == 3 = West

dir2int x | x == North = 0
          | x == East  = 1
          | x == South = 2              
          | x == West  = 3


rotateDirection op x = [ x
                       , int2dir $ (dir2int x) `op` 1
                       , int2dir $ (dir2int x) `op` 2
                       , int2dir $ (dir2int x) `op` 3 ]

directionClockWise = rotateDirection (+)
directionCounterClockWise = rotateDirection (-)