[Haskell-cafe] HDBC, postgresql, bytestrings and embedded NULLs

Michael Snoyman michael at snoyman.com
Tue Jan 18 22:34:43 CET 2011

On Tue, Jan 18, 2011 at 1:17 PM, John Lato <jwlato at gmail.com> wrote:
>> From: Michael Snoyman <michael at snoyman.com>
>> > I took a quick look at the enumerators library, but it doesn't seem to
>> > have
>> > the necessary support for handling data that comes from arbitrary C API
>> > function calls rather than handles or sockets.
>> It does support this, for prior art see yaml[1] or yajl-enumerator[2].
>> I'd be happy to help you with this, as having some enumerator
>> experience is a big help here.
> This is one of the things that iteratee supports rather better than
> enumerator, IMHO.  See "enumFromCallback"[1].

My yaml package originally used iteratee, and I did not even know
about enumFromCallback. Is it a recent addition?

> But if you want this style of code with database access, why not try
> Takusen?

For one, it's easier to build an enumerator-package-based solution
based on a cursor-oriented library than a library using a different
type of enumerator. Also, I'm not quite sure how well the Takusen
approach of using compile-time flags to determine which backends get
built would work for my users. Right now, by typing "cabal install
persistent-postgresql", they can be guaranteed to get all of the
needed libraries, compiled in a manner which will let them actually
use the database. It seems like that would not be the case with

But the third, and probably biggest, reason, is that I was already
familiar with HDBC.

> John L.
> [1] http://hackage.haskell.org/packages/archive/iteratee/


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