At Wed, 4 Jul 2012 09:06:32 -0700, KC wrote:

you can turn the flag off when you are ready to do the computational heavy lifting so that you don't have to modify your code base?

That is, GHC can then apply its algebraic transformation optimizations to the "code algebra" of the pure functions.

What do you mean "allow mutable top level state"? As in

import Foreign.Ptr import Foreign.StablePtr import Foreign.Storable import System.IO.Unsafe

destructiveUpdate :: Storable a => a -> a -> () destructiveUpdate x y = unsafePerformIO $ do ptr <- newStablePtr x poke (castPtr (castStablePtrToPtr ptr)) y freeStablePtr ptr

? The only problem that the above function does not work - you can't poke or peek off StablePtrs. If that's what you mean, no. And I doubt it'll ever exist, since it breaks the most important invariant in Haskell - that is, that values don't change. An Haskell compiler will rely on this assumption quite heavily, so changes to that are likely to disrupt things seriously. Also, I don't see how destructive updates help debugging. -- Francesco * Often in error, never in doubt