paulcc

class Valid a where
  valid :: a -> OkF Errors

class Valid a => Persist m a where
  save :: a -> m (OkF a)  -- or errors

data User = User {name :: String} 
data Organisation = Organisation {name :: String, users :: [User]}

paulcc

-- see below for commentary

makeUpTo :: Int -> [String] -> [String]
makeUpTo n = mlu []
  where
    mlu pre []     = [pre]
    mlu []  (w:ws) = mlu w ws
    mlu pre (w:ws) | length pre + 1 + length w <= n = mlu (pre ++ ' ' : w) ws
                   | otherwise                      = pre : mlu [] (w:ws)

paulcc

1. http://pragprog.com/magazines/2012-08/thinking-functionally-with-haskell
2. http://pragprog.com/magazines/2012-09/thinking-functionally-with-haskell
3. http://pragprog.com/magazines/2012-10/thinking-functionally-with-haskell
4. http://pragprog.com/magazines/2012-11/thinking-functionally-with-haskell
5. http://pragprog.com/magazines/2012-12/web-programming-in-haskell
6. http://pragprog.com/magazines/2013-01/web-programming-in-haskell-part-ii
7. http://pragprog.com/magazines/2013-03/uncle-bob-and-functional-programming
8. http://pragprog.com/magazines/2013-04/dependent-types
9. http://pragprog.com/magazines/2013-05/dependent-types-part-ii
10. http://pragprog.com/magazines/2013-06/unification