Re: [Haskell-cafe] More ideas for controlled mutation

Yep. It harkens to my days of forcing impure, non-thread-safe C libraries into nice, pure, Haskell FFI bindings. I suppose what I'd like to do here is work in the unsafe IO much more closely with GHC's existing facilities, so that we spend as much time as possible /not/ in unsafePerformIO. A kind of hybrid approach, if you will. P.S. Don Stewart points out that Edward Kmett has can access GHC's pointer tags http://hackage.haskell.org/package/tag-bits, thus allowing us to approximate evaluated/not evaluated. Maybe I'll hack up a prototype next time round. Excerpts from Ketil Malde's message of Sun Apr 24 17:41:23 -0400 2011:

"Edward Z. Yang" writes:

...

I've been toying around with some ideas where we do alternative forms of controlled mutation. One such idea has to do with memoization. [..] Hash tables take advantage of this fact by simply chaining together values in a linked list if they land in the same bucket. [...] An obvious way to do this is to use unsafePerformIO to read out an IORef stating the value currently being looked up, and have the thunk evaluate to the pair of that key and the result. There are some synchronization concerns, of course:

Seen this?

http://augustss.blogspot.com/2011/04/ugly-memoization-heres-problem-that-i.h...

-k