Thanks, Ryan, for the reminder and explanation of this problem. - Conal
On Mon, Apr 28, 2008 at 8:01 PM, Ryan Ingram
The problem I have with all of these STM-based solutions to this problem is that they don't actually cache until the action fully executes successfully.
For example, if you have a :: TIVal a, and f :: a -> TIVal b, and you execute force (a >>= f)
and the action returned by f executes retry for whatever reason, then the caching done in "a" gets undone. Ideally I want to be able to provide some proof that the result of a is pure and have it committed immediately when it finishes.
Every attempt I've had so far to solve this problem ends up being some type of the form newtype X a = IO (STM (Either a (X a))) which has its own problems.
-- ryan