Wopp!

gistfile1.hs

wopp = map sayIt [1..]
    where woppln n | (mod n 7 == 0) = True
                   | ('7' `elem` show n) = True
                   | otherwise = False
          sayIt n = (if woppln n then "wopp" else show n, if direction n > 0 then "right" else "left")
          direction 1 = 1
          direction n | woppln n = (-1) * direction (n-1)
                      | otherwise = direction (n-1)

main = do
    printWopp $ take 100 wopp

printWopp :: [(String, String)] -> IO ()
printWopp [] = do return ()
printWopp (x:xs) = do
    putStrLn $ fst x ++ ", next person is " ++ snd x
    printWopp xs
    return ()