Release plans

Doaitse Swierstra doaitse at
Tue Apr 17 06:50:48 EDT 2007

Just to show what kind of problems we are currently facing. The  
following type checks in our EHC compiler and in Hugs, but not in the  

module Test where

data T s = forall x. T (s -> (x -> s) -> (x, s, Int))

run :: (forall s . T s) -> Int
run ts  = case ts of
             T g -> let (x,_, b) =  g x id
                    in b

Doaitse Swierstra

On Apr 17, 2007, at 12:41 AM, Stefan O'Rear wrote:

> On Mon, Apr 16, 2007 at 03:54:56PM +0100, Simon Marlow wrote:
>> - left-to-right impredicative instantiation: runST $ foo
> This concerns me.  With each ad-hoc extension of the type system, I
> worry that soon the GHC type system will become so byzantine and
> ill-specified that the type checker can only be cloned, not
> substantially improved on.  I personally have a type checker idea I am
> working on, but I doubt I will ever be able to implement features such
> as this, because the type checking abstraction is now leaking badly.
> Once the Hindley-Damas-Milner algorithm is exposed, I fear programmers
> will rely on it and progress in Haskell typechecker implementation
> will be effectively halted.  (Yes, I know I'm a bit late in
> complaining...)
>> - list fusion
> Nitpick - you did mean stream fusion, right?
>> We think the above feature set makes for a pretty strong 6.8 release.
>> What do you think of this plan?  Are there features/bug-fixes that  
>> you
>> really want to see in 6.8?
> Good code generation for loops.  I understand they are rare in
> practice, but it's kinda disheartening to write memset() and see in
> the asm loop 11 memory references, 9 to the stack (numbers from
> unreliable memory).
> I don't mind the plan, either.
> Stefan
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