Cacher is the code snippet organizer for pro developers

-- Using http://www.learnyouahaskell.com/ as reference

data Coordinate = Coordinate Int Int deriving(Show, Eq)
data Direction = North | West | South | East deriving(Show, Eq)
data Position = Position Coordinate Direction deriving(Show, Eq)

instance Enum Direction where
    toEnum 0 = North
    toEnum 1 = East
    toEnum 2 = South
    toEnum 3 = West
    toEnum x = toEnum (x `mod` 4)

    fromEnum North = 0
    fromEnum East = 1
    fromEnum South = 2
    fromEnum West = 3

turn (Position coordinate direction) findAdjacentDirection = Position coordinate newDirection
    where newDirection = findAdjacentDirection direction

turnLeft position = turn position pred
turnRight position = turn position succ

moveForward (Position coordinate direction) = Position newCoordinate direction
    where moveCoordinateInDirection (Coordinate x y) North = Coordinate x (y + 1)
          moveCoordinateInDirection (Coordinate x y) South = Coordinate x (y - 1)
          moveCoordinateInDirection (Coordinate x y) East = Coordinate (x + 1) y
          moveCoordinateInDirection (Coordinate x y) West = Coordinate (x - 1) y
          newCoordinate = moveCoordinateInDirection coordinate direction

startingDirection = North
startingCoordinate = Coordinate 0 0

inInitialDirection (Position _ direction) = direction == startingDirection
atStartingCoordinate (Position coordinate _) = coordinate == startingCoordinate

inFiniteCircle instructions = inFiniteCircle' instructions startingPosition
    where startingPosition = Position startingCoordinate startingDirection
inFiniteCircle' instructions position
    | atStartingCoordinate newPosition = True
    | not (inInitialDirection newPosition) = inFiniteCircle' instructions newPosition
    | otherwise = False
    where newPosition = consumeInstructions instructions position

consumeInstructions "" position = position
consumeInstructions (i:is) position = consumeInstructions is newPosition
    where newPosition = consumeInstruction i position

consumeInstruction 'L' position = turnLeft position
consumeInstruction 'R' position = turnRight position
consumeInstruction 'G' position = moveForward position

-- ~/tmp% ghci
-- GHCi, version 7.10.1: http://www.haskell.org/ghc/  :? for help
-- Prelude> :load myntra-challenge
-- [1 of 1] Compiling Main             ( myntra-challenge.hs, interpreted )
-- Ok, modules loaded: Main.
-- *Main> inFiniteCircle "L"
-- True
-- *Main> inFiniteCircle "GRGL"
-- False
-- *Main> inFiniteCircle "GRGR"
-- True