MultipleDwelling.hs

import Control.Monad
import Data.List

distinct :: Eq a => [a] -> Bool
distinct [] = True
distinct (x:xs) = case x `elem` xs of
                   True -> False
                   False -> distinct xs

multipleDwelling :: [[(String, Integer)]]
multipleDwelling = [ [ ("Baker", baker)
                     , ("Cooper", cooper)
                     , ("Fletcher", fletcher)
                     , ("Miller", miller)
                     , ("Smith", smith) ] | baker <- [1..5]
                                          , cooper <- [1..5]
                                          , fletcher  <- [1..5]
                                          , miller <- [1..5]
                                          , smith  <- [1..5]
                                          , distinct [baker, cooper, fletcher, miller, smith]
                                          , (baker /=  5)
                                          , (cooper /= 1)
                                          , (fletcher /= 5)
                                          , (fletcher /= 1)
                                          , (miller > cooper)
                                          , abs (smith - fletcher) /= 1
                                          , abs (fletcher - cooper) /= 1 ]

multipleDwellingDo :: [[(String, Int)]]
multipleDwellingDo = do
  baker    <- [1..5]
  cooper   <- [1..5]
  fletcher <- [1..5]
  miller   <- [1..5]
  smith    <- [1..5]

  guard (distinct [baker, cooper, fletcher, miller, smith])

  guard (baker /=  5)
  guard (cooper /= 1)
  guard (fletcher /= 5)
  guard (fletcher /= 1)
  guard (miller > cooper)
  guard (abs (smith - fletcher) /= 1)
  guard (abs (fletcher - cooper) /= 1)

  return [
      ("Baker"   , baker)
    , ("Cooper"  , cooper)
    , ("Fletcher", fletcher)
    , ("Miller"  , miller)
    , ("Smith"   , smith)
    ]