On Wed, Nov 23, 2005 at 10:47:02AM -0000, Simon Marlow wrote:
Apologies for being a bit blunt, but can't this problem be solved by introducing a LazyStateT in addition to StateT? This follows the pattern of ST (default is strict, we also have Control.Monad.ST.Lazy).
That would be great. Except that I would prefer StrictState, with laziness the default. ST is from the IO family of monads, so one expects strictness. MTL monads are usually pure, so the default should be laziness like everywhere else in Haskell. Many of the programs I have written in the past few years would break if State were to become strict. But in any case, there is still a bug to fix. State and StateT are currently straddling both sides of the fence; State is lazy, and StateT is strict. Regards, Yitz