I see… Unfortunately I did not spent enough time playing with Clean, and I’m still learning Haskell, so I can’t give any feedback on your questions J

Now from the little time I’ve spent in the company of Clean, I must say there’s another advantage of uniqueness typing: it is very easy to understand. While monads are a tiny bit more demanding! But monads give such a mental satisfaction once you see the light  ;-)

So you say uniqueness typing might be more general… Can one make list monads and all the other funky Haskell monads with Clean’s uniqueness typing then?

Peter

From: Jeff φ [mailto:jeff1.61803@gmail.com]
Sent: woensdag 6 februari 2008 20:21
To: Peter Verswyvelen; Neil Mitchell; Don Stewart
Cc: haskell-cafe@haskell.org
Subject: Re: [Haskell-cafe] Mutable arrays

On 2/6/08, Peter Verswyvelen <bf3@telenet.be> wrote:

Yeah, I also believed that, but then I'm confused:

So monads *do* enforce uniqueness... So what is the difference between
Haskell's monad approach and Clean's uniqueness typing? I always thought
these were just two different ways to tackle the same problem, and I had the
feeling Haskell's approach was actually more general.

IO and mutable array monads could be implemented on top of Clean's unique arrays and world objects.  So, I'd argue that Clean is at least as general as Haskell. 

On the other hand, I've posted two similar problems to this list. In Haskell I want to . . .

1) turn a mutable array into a lazy list

2) turn the contents of a file into a lazy list

The responses I've received are typically:

1) Use unsafeFreeze / unsafeThaw

2) Use hGetContents. (which uses unsafePeformIO under the hood.)

3) Don't use a lazy list.  Rewrite the code to break the data up into smaller chunks and process the chunks in a loop.

I have solved both of these problems in Clean using a lazy list without resorting to unsafe operations.  So, it seems to me that uniqueness types are more general than monads.

By the way, I'm not good enough to use unsafe functions.  My code would crash for sure.  :-)