Proposal: Make StateT in mtl lazy

[Donald Bruce Stewart]

igloo:
> 
> http://hackage.haskell.org/trac/ghc/ticket/1127
> 
> Deadline: 28 February 2007.
> 
> I propose we make StateT lazy, as I suspect was the intention all along
> and as has been discussed (without reaching a conclusion) before.
> 
> The patch is simply (in the definition of (>>=)):
> 
> hunk ./Control/Monad/State.hs 195
> -               (a, s') <- runStateT m s
> +               ~(a, s') <- runStateT m s

Is it possible to provide a short example of the different behaviours
you need or expect?

-- Don