Subject: Re: [Haskell-cafe] Either Monad and Laziness

On 9/14/12 5:16 PM, Eric Velten de Melo wrote:

...

But now I'm kinda lost. Is there an easy way to explain the difference between: -iteratee -conduit -enumerator

I tend to group them into three families. 'iteratee' and 'enumerator' are fairly directly drawn from Oleg's code, with mostly implementation differences (at least when compared to the other families). They've tended to keep Oleg's original names (iteratee, enumerator, enumeratee). The biggest user-visible difference between iteratee and enumerator is the level of datastream abstraction. iteratee abstracts over the stream, and enumerator abstracts over elements of the stream. The stream is explicitly a list of elements. This exposes some of the details of data chunking to the user, which has both advantages and disadvantages (iteratee exposes this also, but it's not necessary as is the case for enumerator). The second family (chronologically) includes conduit and (maybe) iterIO. I've written a little about this group at http://johnlato.blogspot.sg/2012/06/understandings-of-iteratees.html Although they serve the same goals in spirit, the implementation may or may not necessarily be an iteratee/enumerator arrangement (e.g. conduit). This is a technical observation, not a criticism, depending on exactly what you consider to define the style in the first place. This group has usually renamed functions. I discuss some of the other differences on my blog. The third familiy is all the pipes-* stuff. This group tends towards emphasizing the relationship between iteratee/enumerator pairs and coroutines, and also emphasizing (to use Oleg terminology) composition of enumeratees. I've been meaning to write more about this group, but thus far have been unable to do so. I'd rather not hijack by evangelizing, but obviously I think iteratee provides several important advantages over the other options. John L.