Dean Herington wrote:
I can't seem to figure out how to achieve strictness in the context of the State monad.
Unfortunately, the current situation is that State is only available as a lazy monad, and StateT is only available as a strict monad. It seems to me that this should clearly be considered a serious bug in the library. It has been reported on numerous occasions over the years, but it has still not been fixed. At the very least, the two should be consistent. I would much prefer for them both to be lazy. I have written a lot of code that depends on that; it is the natural assumption in Haskell that everything is lazy by default, except seq, IO, and their friends. The obvious solution would be to have available both a lazy and a strict version of each monad: State, State', StateT, and State'T (or some such), with functions to convert between them. It is trivial to implement that in the current library. If someone can come up with a more elegant solution right away, that would be great. (Iavor - do you have a solution?) Otherwise, I think we have waited long enough. Let's implement the simple fix. This bug is a major inconvenience to users of this library.
(try 1000000) overflows the stack.
In the current situation, you can use
where final = runIdentity $ execStateT prog (0::Int) ... tick :: (Num a, MonadState a m) => m a ...
Regards, Yitz