[Haskell-cafe] Bytestrings and [Char]

John Lato jwlato at gmail.com
Wed Mar 24 11:50:48 EDT 2010

I still think that getting other authors to use it would be the
biggest difficulty.  Another concern of mine is that RULEs-based
fusion can be fragile; if the type classes prevent fusion from
occurring you'll never approach the performance of monomorphic code.

That said, I think this is worth pursuing further because of the
benefits you describe.  I have spent a great deal of time on exactly
this issue with the iteratee package, although my needs there are
relatively simple.

As a general question to the Haskell community: have you ever
attempted to write container-polymorphic code?  I'd like to hear about
either successes or stumbling blocks.

On Wed, Mar 24, 2010 at 12:02 PM, Alberto G. Corona <agocorona at gmail.com> wrote:
> Once we have a  tree of type classes suitable for all containers, as you
> said, theoretically it  shouldn't very difficult to incorporate the testing
> of different instances for each class used in a program, besides  testing
> different compilation flags in a genetic algoritm. This latter has already
> been done.
> http://donsbot.wordpress.com/2010/03/01/evolving-faster-haskell-programs-now-with-
> To find automatically the best combination of class implementations and
> compilation flags in a single process would be very useful and would save a
> lot of manual testing.
> 2010/3/24 John Lato <jwlato at gmail.com>
>> Hi Alberto,
>> To some extent this already exists, it's just that nobody uses it.  I
>> believe it's the approach taken by the Edison libraries.  Also the
>> ListLike package provides the type classes ListLike, StringLike, and a
>> few others.  Neither seems to have become very popular despite having
>> well-respected authors (Okasaki and Goerzon, respectively).
>> Some container functions are already provided by other classes, namely
>> Foldable, Traversable, and Monoid.
>> The first bit, creating a tree of type classes suitable for all
>> containers, is probably a few hours work.
>> An automated system to determine the best implementation is
>> significantly more difficult; I can't say if the scope would be
>> appropriate for SoC.
>> Best,
>> John
>> > From: "Alberto G. Corona " <agocorona at gmail.com>
>> >
>> > Just a dream:
>> > -separate interface and implementation for all containers, via type
>> > classes
>> > -develop, by genetic programming techniques + quickcheck, a system that
>> > find
>> > the best container implementation for a particular program.
>> >
>> > Is that suitable for a Google Summer of Code project?
>> >
>> > 2010/3/23 Alberto G. Corona <agocorona at gmail.com>
>> >
>> > The question can be generalized via type classes: Is there any common
>> > set of
>> >> primitives encapsulated into a single type class that has instances for
>> >> Strings (Data.List) ByteStrings, Data.Text, Lazy bytestrings, Arrays,
>> >> vectors and wathever container that can store an boxed, unboxed, packed
>> >> unpacked sequence of wathever including chars? All of them have folds,
>> >> heads, tails and a lot of common functions with the same name, but
>> >> since
>> >> there is not a single type class, the library programmer can not
>> >> abstract
>> >> his code when it is possible, so the library user can chose the
>> >> particular
>> >> instance for his particular problem.

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