[Haskell-cafe] newbie: maintaining relationships

23 May 2008

      I am learning haskell and i need some advice about writing
functional-style code.

Give the following code below, my question is - how do i setup a
dependency of User on Common?

Obviously what i have there is wrong, because a change in common (i know
it's actually immutable) is not reflected in the version captured by
User. I understand why my current approach has not a chance a of
working, I am using it to, hopefully, illustrate my goal.

Thanks for any suggestions
...
data Common = Common {
      		cName :: String,
      		cValue :: Int
      		} deriving (Show)
data User = User {
      		uCommon	:: Common
      		} deriving (Show)
makeWorld = (commons, users)
  where
  commons = [Common "A" 1, Common "B" 2]
  users	= [User (head commons)]
main = do
  let world = makeWorld
  putStrLn (show world)

[Haskell-cafe] newbie: maintaining relationships

geoffrey