Re: [Haskell-cafe] Bytestrings and [Char]

I have a very specific StringLike typeclass in the web-encodings package so that I can- for example- to HTML entity encoding on String, (lazy) bytestrings and (lazy) text. Of course, I need to make assumptions about character encoding for the bytestring version. Michael On Wed, Mar 24, 2010 at 8:50 AM, John Lato wrote:

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 wrote:

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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.

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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

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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

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From: "Alberto G. Corona "

Just a dream: -separate interface and implementation for all containers, via type classes -develop, by genetic programming techniques + quickcheck, a system

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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

The question can be generalized via type classes: Is there any common set of

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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,

http://donsbot.wordpress.com/2010/03/01/evolving-faster-haskell-programs-now... that packed

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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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