[Haskell-cafe] What's the deal with Clean?

[Daniel Peebles]

In the presence of fusion (as is the case in uvector), it's hard to
give meaningful time complexities for operations as they depend on
what operations they are paired with. We need to think of a better way
to express this behavior in the documentation though.

On Tue, Nov 3, 2009 at 9:12 PM, brian <briand at aracnet.com> wrote:
> Really, arrays in Haskell are the most @#!$! confusing thing in the world.
>
> There's a bunch of different array structures.
>
> I can't tell which one works best, and all I want to do is x[i] = value.
>
> I thought uvector was the answer, you know, fast unboxed ARRAYs.  Imagine my
> surprise when I saw this
>
>  indexU :: UA e => UArr e -> Int -> e
>
>  O(n). indexU extracts an element out of an immutable unboxed array.
>
> An array implementation with an order N lookup.  huh ??  That's not an
> array, that's a list.  I was looking for an array.
>
> However, I then found in the same hackage:
>
>  readMU :: MUArr e s -> Int -> ST s e
>
>  O(1). readMU reads the element at the specified index of a mutable unboxed
> array.
>
> So O(1) for mutable, but O(n) for immutable ? See, confusing...  I'm sure
> there's a really good, lofty type safety, something
> or other reason for that, that I'm sure I don't care about ;-)
>
> There's also ST.  So why is there a uvector, when there's ST ??
>
> etc, etc, etc...
>
> and then there's monads...
>
> other than that, having fun with haskell :-)
>
> Brian
>
>
> On Nov 3, 2009, at 3:42 PM, David Leimbach wrote:
>
>>
>>
>> On Tue, Nov 3, 2009 at 2:16 PM, Tracy Wadleigh <tracy.wadleigh at gmail.com>
>> wrote:
>>
>> I had to implement a ring buffer, and I wanted the code using it to be
>> written in Haskell.  I ended up implementing the buffer in C, and wrapping
>> it in FFI from Haskell because implementing a destructive array in Haskell
>> is kind of unwieldy to someone of my experience level.  In Clean, it looks
>> like the uniqueness typing allows for destructive updates in a very
>> controlled manner.
>>
>> The ST monad provides this functionality. The
>> never-instantiated-in-a-visible-way state parameter of the ST monad provides
>> the "uniqueness" required for doing destructive updates in a pure way.
>>
>> Someone suggested that to me on IRC once I'd already cranked out a C
>> implementation with FFI bindings.  It's just too easy to use the FFI in
>> Haskell :-)
>>
>> If we raise the barrier of FFI, more people will use ST!
>>
>> Dave
>>
>>
>>
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