decode
  :: Matrix.Matrix String -- ^ Grid to solve for
  -> String -- ^ Solution key that's being built up
  -> Position -- ^ Current position
  -> [String] -- ^ List of movements for each code character
  -> String -- ^ Solution
decode _ key _ [] = key
decode
  :: Matrix.Matrix String -- ^ Grid to solve for
  -> String -- ^ Solution key that's being built up
  -> Position -- ^ Current position
  -> [String] -- ^ List of movements for each code character
  -> String
decode _ key _ [] = key
decode _ key _ [] = key