Re: Combining IO and state monads

G'day all. On Sat, May 17, 2003 at 12:30:11PM +0100, Ganesh Sittampalam wrote:

Also, I strongly recommend the use of a record to keep your state - if you use a tuple, then each time you add something new you'll have to change all the getters and setters (or any other code that acts directly on the structure of the state).

One thing that I've also found useful is to stack a ReaderT on top of IO, and store a record of IORefs in the ReaderT state. This way, not only is it extensible, but you don't pay the cost of repacking the state tuple in code that modifies state a lot. You could, of course, also do this with STRefs. Cheers, Andrew Bromage