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

[Don Stewart]

UArr operations subject to stream fusion:

    http://code.haskell.org/~dons/code/uvector/Data/Array/Vector/Strict/

Direct-style operations, not subject to the optimization:

    http://code.haskell.org/~dons/code/uvector/Data/Array/Vector/UArr.hs

/me needs to write a tutorial on this.

-- Don

briand:
> Don,
>
> There is more than one indexU ?
>
> In Data.Array.Vector there is only 1 indexU that I can find.
>
> Brian
>
> On Nov 3, 2009, at 9:15 PM, Don Stewart wrote:
>
>> Well, it depends on which indexU the OP means. The one linked in the  
>> docs is
>> the O(1) UA type class version.
>>
>> -- Don
>>
>> gcross:
>>> Actually, it's not a typo.  If you look at the source, what you'll  
>>> see
>>> is
>>>
>>> indexU arr n = indexS (streamU arr) n
>>>
>>> and then tracking down indexS, you'll see
>>>
>>>
>>> indexS (Stream next s0 _) n0
>>>    | n0 < 0    = error "Data.Array.Vector.Stream.indexS: negative
>>> index"
>>>    | otherwise = loop_index n0 s0
>>>  where
>>>    loop_index n s = case next s of
>>>      Yield x s' | n == 0    -> x
>>>                 | otherwise -> s' `seq` loop_index (n-1) s'
>>>      Skip    s'             -> s' `seq` loop_index  n    s'
>>>      Done                   -> error  
>>> "Data.Array.Vector.Stream.indexS:
>>> index too large"
>>>
>>>
>>> So in other words, indexU really does have O(n) complexity since it
>>> first converts the array into a stream and then walks down the  
>>> stream in
>>> order to find the desired element.
>>>
>>> Cheers,
>>> Greg
>>>
>>>
>>> On Nov 3, 2009, at 6:25 PM, Roman Leshchinskiy wrote:
>>>
>>>> On 04/11/2009, at 13:12, brian wrote:
>>>>
>>>>> indexU :: UA e => UArr e -> Int -> e
>>>>>
>>>>> O(n). indexU extracts an element out of an immutable unboxed array.
>>>>
>>>> This is a typo (unless Don inserted a nop loop into the original DPH
>>>> code).
>>>>
>>>> Roman
>>>>
>>>>
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