2008/5/22 Marc Weber
So in haskell it would look like this: let updatedCd = 0x22 CD (0x6 "My song") (0x20 ( 0x23 : ...) updatedTrack = 0x23 Track ( 0x21 "updated track title" ) 0x22 in (0x27) DB (0x24 (updatedCd:otherCds)) (0x25 (updatedTrack:otherTracks))
Mmmm I don't think that this is a good way to go. Let me do a counter-example: data A = A String data B = B String [A] data C = C String [B] data D = D String [C] Suppose to have some As, Bs, Cs, Ds in your database. Now you want to "update" the String of A. As you cannot "update" stuff in Haskell mantaining the same pointer, you've got a "new A". So you must find all Bs that had this A in their list, and update that. Unfortunately lists are not mutable too, so you are creating a new list; so you need to create new containing Bs too. But then you must change Cs... and so on. A little change like changing the String in A requires updating the whole "DB". Salvatore