Re: [Haskell-cafe] functions making their own memos

Thanks, that's a cool solution. Here's another thought to avoid IO. What if we're operating inside a state monad which has a list of memos. The creation function newCounter then adds a memo to the list and creates getCount as a closure with that index. The problem is that when we define the state with its list of memos, we don't know what data type each individual function will want to use. D On Sun, Jul 8, 2018 at 4:15 AM, Greg Horn wrote:

What about something like:

import Data.IORef ( IORef, newIORef, readIORef, writeIORef )

newCounter :: IO (IO Int) newCounter = do counterRef <- newIORef 0 :: IO (IORef Int) let getCount :: IO Int getCount = do count <- readIORef counterRef writeIORef counterRef (count + 1) return count return getCount

The user calls this function which creates the cache and returns the stateful function. You can use MVars instead of IORefs if you want it to work concurrently.

On Sun, Jul 8, 2018 at 2:29 AM Dennis Raddle wrote:

...

In this one use case, there might be a simpler solution, but I have encountered lots of situations in which a particular algorithm could benefit from an associated stored cache of information. The most natural way to write an algorithm, sometimes, is in terms of its past decisions or past state of the program, interacting with current state.

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