Re: [Haskell-beginners] Global variables

On Thu, Jun 30, 2011 at 8:35 AM, Ertugrul Soeylemez wrote:

Michael Snoyman wrote:

...

Though in this case, you can go with the cheaper IORef, since (presumably) the only operation is going to be incrementing the counter. Just be sure to use atomicModifyIORef[1].

I never recommend (or mention for that matter) IORefs in the beginner list.  Also I think than an atomically modified IORef is not necessarily faster.  TVars are optimized for that kind of operation.

I understand why you avoid mentioning IORef, but I personally find it a simpler solution to the problem, and avoids the need for a beginner to jump into STM. I'd be very interested in seeing if TVars can be as fast as IORefs for this kind of stuff; I know switching the timeout code in Warp to use atomic IORef operations produced a *huge* speed gain, but I may be conflating multiple code changes together. Michael