[Haskell-cafe] Data Structures GSoC

Nathan Hunter enferris at gmail.com
Tue Apr 6 00:26:42 EDT 2010

Well, one of my most important questions has been indirectly answered. It
seems like Map is still the main point of interest, and Jamie Brandon's list
of remaining objectives<http://www.haskell.org/pipermail/haskell-cafe/2009-March/058270.html>
modifying the API to work with the edison or collections API, and
benchmarking. I haven't attempted a project this large before, so I'm not
sure what is feasible in the allotted time. A complete Data Structures
overhaul seems out of the question, but polishing up a single one seems far
too sparse. Then again, the benchmarking could represent a significant chunk
of work.


On Wed, Mar 31, 2010 at 11:28 AM, wren ng thornton <wren at freegeek.org>wrote:

> Nathan Hunter wrote:
>> Hello.
>> I am hoping to take on the Data Structures project proposed two years ago
>> by
>> Don Stewart here<
>> http://hackage.haskell.org/trac/summer-of-code/ticket/1549>,
>> this summer.
>> Before I write up my proposal to Google, I wanted to gauge the reaction of
>> the Haskell community to this project.
>> Particularly:
>> -What Data Structures in the current libraries are in most dire need of
>> improvement?
>> -How necessary do you think a Containers Library revision is?
> One thing I've seen come up repeatedly is the issue of presenting a unified
> and general interface for Data.Map, Data.IntMap, and related things like
> Data.Set, bytestring-trie, pqueue, etc which intended to mimic their
> interface. That alone isn't big enough for a GSoC, but it would be a very
> nice thing to have. Every few months there's a request on the libraries at list to alter, generalize, or reunify the map interface in some way.
> ** Just to be clear, I do not mean coming up with a typeclass nor doing
> things like the generalized-trie tricks, I just mean a good old fashioned
> standard API. **
> There are countervailing forces for making a good API. On the one hand we
> want functions to do whatever we need, on the other hand we want the API to
> be small enough to be usable/memorable. In the bytestring-trie library I
> attempted to resolve this conflict by offering a small set of highly
> efficient ueber-combinators in the internals module, a medium sized set of
> functions for standard use in the main module, and then pushed most
> everything else off into a convenience module.
> The containers library would do good to follow this sort of design. The
> Data.Map and Data.IntMap structures don't provide the necessary
> ueber-combinators, which has led to the proliferation of convenience
> functions which are more general than the standard use functions but not
> general enough to make the interface complete. Also, these generalized
> functions are implemented via code duplication rather than having a single
> implementation, which has been known to lead to cut&paste bugs and
> maintenance issues. Provided the correct ueber-combinators are chosen, there
> is no performance benefit for this code duplication either (so far as I've
> discovered with bytestring-trie).
> Additionally, it'd be nice if some of the guts were made available for
> public use (e.g., the bit-twiddling tricks of Data.IntMap so I don't have to
> duplicate them in bytestring-trie).
> Also it would be nice to develop a cohesive test and benchmarking suite,
> which would certainly be a large enough task for GSoC, though perhaps not
> fundable.
> I would be willing to co-mentor API and algorithm design for cleaning the
> cobwebs out of the containers library. I wouldn't have the time for
> mentoring the choice of datastructures or benchmarking however.
> --
> Live well,
> ~wren
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