iteratee [] suggestion for mapStreamM

[Ben]

Hi --

I see you have distributed the unfinished tutorial.  That is fine, but
please put a note on it saying it is not finished in the next release
(hopefully I will finish it before the next release so this will be
unnecessary!)

I haven't had time to edit it for wiki publication, but I will try to
get to that sometime.

Best, Ben Lee

On Mon, Aug 23, 2010 at 11:24 AM, John Lato <jwlato at gmail.com> wrote:
> Hi Ben,
>
> Thanks very much for submitting this; it looks very good.  I'm sure it will
> be helpful.  I could distribute this with the package if you like, but
> perhaps you might want to put some of this on the wiki?  I think it would
> reach more viewers then.
>
> Sincerely,
> John
>
> On Mon, Aug 23, 2010 at 6:36 PM, Ben <midfield at gmail.com> wrote:
>>
>> i have been unable to finish my iteratee tutorial due to my job being
>> crazy right now.  i might be able to get back to it at a later date,
>> but with the advent of the new simplified iteratee library, i thought
>> it might be useful to have in this unfinished form, because the most
>> finished part is about CPS-style versus ADT style.  it might be useful
>> to cut out (it's at the end, under the CPS heading) to help teach
>> people how to convert their old-style iteratee code into CPS style.
>>
>> best, b
>>
>> On Mon, Aug 16, 2010 at 8:10 AM, John Lato <jwlato at gmail.com> wrote:
>> > On Sun, Aug 15, 2010 at 1:20 AM, Ben <midfield at gmail.com> wrote:
>> >>
>> >> A suggestion for Data.Iteratee.ListLike :
>> >>
>> >> mapStreamM :: (Monad m) =>
>> >>  (el -> m el')
>> >>  -> Enumeratee [el] [el'] m a
>> >> mapStreamM mf = eneeCheckIfDone (liftI . step)
>> >>  where
>> >>    step k (Chunk xs)
>> >>      | LL.null xs = liftI (step k)
>> >>      | otherwise  = joinIM $ do ys <- mapM mf xs
>> >>                                 return $ mapStreamM mf $ k (Chunk ys)
>> >>    step k s       = idone (liftI k) s
>> >>
>> >> an improvement would be something that actually uses the ListLike
>> >> class (or some monadic extension of it.)
>> >
>> > Thanks for this suggestion; I think it would be useful.
>> > This gets to a related issue I've been struggling with for some time.  I
>> > would like for iteratee to support using mutable buffers.  I believe
>> > this
>> > could be very efficient as it would completely bypass a large amount of
>> > allocation/gc work.  There are two primary issues I have so far:
>> > 1)  I don't know how to make them 100% compatible with standard
>> > iteratees
>> > because the Monad instance needs to be slightly different.  In my test
>> > implementation I use a newtype of Iteratee, which is mostly
>> > satisfactory.
>> > 2) Everything in ListLike needs to be re-written for a monadic version.
>> >  ListLike itself is not widely used, but for mutable buffers there's
>> > even
>> > more disparity.  At least ListLike instances for Vector, Text, etc. can
>> > be
>> > written relatively mechanically.
>> > Is there any interest in further developments in this direction?
>> > John
>
>