Re: [Haskell-cafe] Reifying case expressions [was: Re: On stream processing, and a new release of timeplot coming]

On Mon, Dec 26, 2011 at 12:32:13PM +0400, Eugene Kirpichov wrote:

2011/12/26 Gábor Lehel

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On Sun, Dec 25, 2011 at 9:19 PM, Eugene Kirpichov wrote:

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Hello Heinrich,

Thanks, that's sure some food for thought!

A few notes: * This is indeed analogous to Iteratees. I tried doing the same with Iteratees but failed, so I decided to put together something simple of my own. * The Applicative structure over this stuff is very nice. I was thinking, what structure to put on - and Applicative seems the perfect fit. It's also possible to implement Arrows - but I once tried and failed; however, I was trying that for a more complex stream transformer datatype (a hybrid of Iteratee and Enumerator). * StreamSummary is trivially a bifunctor. I actually wanted to make it an instance of Bifunctor, but it was in the category-extras package and I hesitated to reference this giant just for this purpose :) Probably bifunctors should be in prelude.

Edward Kmett has been splitting that up into a variety of smaller packages, for instance:

http://hackage.haskell.org/package/bifunctors

Actually it's not a bifunctor - it's a functor in one argument and contrafunctor in the other. Is there a name for such a structure?

"Bifunctor" is usually used for such things as well. Data.Bifunctor only covers bifunctors which are covariant in both arguments. -Brent