scaffolding for http://realmode.com/

punch22.hs

import Data.Bool
import qualified Data.Map.Lazy as Map

data Encoding = Encoding (Bool, Bool, Bool) deriving (Eq, Ord)

data Assignment = Assignment { initial::Encoding, subsequent::[Encoding]}

data Letter = A | B | C | D deriving (Show, Enum, Eq, Ord)

type Solution = Map.Map Letter Assignment

checkPair solution pair = let (from, to) = pair
                              Just fromEncoding = Map.lookup from solution
                              Just toEncoding = Map.lookup to solution
                              hasPotentialTransition = any (initial fromEncoding <=) $ initial toEncoding : subsequent toEncoding
                          in hasPotentialTransition


check solution =
  let allLetters = enumFrom A
      pairs = [(x,y) | x <- allLetters, y <- allLetters]
  in
      all (checkPair solution) pairs

main = let
    foo = Encoding (False, False, False)
    bar = Encoding (True, True, True)
    good = Map.fromList
      [(A, Assignment {initial= Encoding (False, False, False), subsequent=[Encoding (True, True, True)]}),
       (B, Assignment {initial= Encoding (False, False, True), subsequent=[Encoding (True, True, False)]}),
       (C, Assignment {initial= Encoding (False, True, False), subsequent=[Encoding (True, False, True)]}),
       (D, Assignment {initial= Encoding (True, False, False), subsequent=[Encoding (False, True, True)]})]
    bad = Map.fromList
      [(A, Assignment {initial= Encoding (False, False, False), subsequent=[]}),
       (B, Assignment {initial= Encoding (False, False, True), subsequent=[Encoding (True, True, False)]}),
       (C, Assignment {initial= Encoding (False, True, False), subsequent=[Encoding (True, False, True)]}),
       (D, Assignment {initial= Encoding (True, False, False), subsequent=[Encoding (False, True, True)]})]
  in do
    print $ check good
    print $ check bad