never executed always true always false

    1 module HelVM.HelMA.Automata.Piet.Types.DirectionPointer
    2   ( DirectionPointer (..)
    3   , addCoordinates
    4   , move
    5   , nextPointer
    6   , rotate
    7   ) where
    8 
    9 import           HelVM.HelMA.Automata.Piet.Types.Coordinates
   10 import           HelVM.HelMA.Automata.Piet.Types.Extra
   11 
   12 import           Lens.Micro
   13 
   14 addCoordinates ∷ DirectionPointer → Coordinates → Coordinates
   15 addCoordinates DPRight (x, y) = (x + 1, y)
   16 addCoordinates DPDown  (x, y) = (x, y + 1)
   17 addCoordinates DPLeft  (x, y) = (x - 1, y)
   18 addCoordinates DPUp    (x, y) = (x, y - 1)
   19 
   20 move ∷ DirectionPointer → Coordinates → Coordinates
   21 move DPLeft  = _1 -~ 1
   22 move DPRight = _1 +~ 1
   23 move DPUp    = _2 -~ 1
   24 move DPDown  = _2 +~ 1
   25 
   26 nextPointer ∷ DirectionPointer → DirectionPointer
   27 nextPointer DPLeft  = DPUp
   28 nextPointer DPUp    = DPRight
   29 nextPointer DPRight = DPDown
   30 nextPointer DPDown  = DPLeft
   31 
   32 rotate ∷ Int → DirectionPointer → DirectionPointer
   33 rotate = change 4
   34 
   35 data DirectionPointer
   36   = DPRight
   37   | DPDown
   38   | DPLeft
   39   | DPUp
   40   deriving stock (Bounded, Enum, Eq, Ord, Read, Show)