[Haskell-cafe] Re: Left fold enumerator - a real pearl overlooked?

Don Stewart dons at galois.com
Sat Feb 28 17:54:16 EST 2009

> Hello Günther,
> I think the largest reason Haskellers don't use left-fold enumerators
> is that there isn't a ready-to-use package on Hackage.  Oleg's code is
> extremely well commented and easy to follow, but it's not cabalized.
> In addition to Takusen, Johan Tibbe's hyena application server uses
> enumerators for IO:
> http://github.com/tibbe/hyena/tree/master
> There is a darcs repo of a cabalized iteratee package available at
> http://inmachina.net/~jwlato/haskell/iteratee/
> This is essentially Oleg's code, slightly modified and reorganized.
> If anyone is interested in using left-fold enumerators for IO, please
> give it a look and let me know what you think.  I'd like to put this
> on hackage in about a week or so, if possible.  I would especially
> appreciate build reports.
> There are a few iteratee/enumerator design questions that remain,
> which Oleg and others would like to explore more fully.  The results
> of that research will likely find there way into this library.

I agree. There's no left-fold 'bytestring' equivalent. So it remains a
special purpose technique.

-- Don

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