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Contents
module Robot (Bearing(..),
mkRobot,
coordinates,
bearing,
simulate,
turnRight,
turnLeft
) where
import Data.List (foldl')
import Control.Arrow (first, second)
data Movement = TurnLeft
| TurnRight
| Advance
deriving (Show, Eq, Enum)
data Bearing = North
| East
| South
| West
deriving (Show, Eq, Enum, Bounded)
type Coordinates = (Int, Int)
data Robot = Robot { bearing :: Bearing
, coordinates :: Coordinates
} deriving (Show, Eq)
mkRobot :: Bearing -> Coordinates -> Robot
mkRobot = Robot
advance :: Bearing -> Coordinates -> Coordinates
advance dir = case dir of
North -> second succ
East -> first succ
South -> second pred
West -> first pred
turnLeft, turnRight :: Bearing -> Bearing
turnLeft d | d == minBound = maxBound
| otherwise = pred d
turnRight d | d == maxBound = minBound
| otherwise = succ d
instructions :: String -> [Movement]
instructions = map fromChar
where fromChar c = case c of
'L' -> TurnLeft
'R' -> TurnRight
'A' -> Advance
_ -> error ("Unknown movement " ++ show c)
step :: Movement -> Robot -> Robot
step Advance r = r { coordinates = advance (bearing r) (coordinates r) }
step TurnLeft r = r { bearing = turnLeft (bearing r) }
step TurnRight r = r { bearing = turnRight (bearing r) }
simulate :: Robot -> String -> Robot
simulate r = foldl' (flip step) r . instructions
Version data entries
396 entries across 396 versions & 1 rubygems