[Haskell-beginners] Haskell Serialization

[Ashish Agarwal]

Thanks for the reference. Sounds like a neat idea so I'll definitely check
it out!

Right now, there are lots of complications in designing this library, at
least if I want a nice API. I have lots and lots of type definitions to
encode the various constructs of the protocol I'm working with. New versions
could make arbitrary changes: add or remove a field to a record, change the
type of a record field, add or remove one of several possible cases (which I
encode with sum types), and so on. It's not at all clear to me yet how I
should factor my type definitions, and/or use other features such as
polymorphic types, type classes, etc. But I guess this is a different
thread.

On Wed, May 12, 2010 at 4:35 PM, Stephen Blackheath [to Haskell-Beginners] <
mutilating.cauliflowers.stephen at blacksapphire.com> wrote:

> Ashish,
>
> I've been using XML picklers for serialization, which you might want to
> consider if you can handle a little extra CPU/data cost.  I'm the author
> of hexpat-pickle, so this is a plug for my package.  I lifted the idea
> wholesale from the HXT package.
>
> Handling changes in protocol version is really easy.  I've been doing a
> lot of
>
> xpSomething = new `xpTryCatch` old
>  where
>     new = ...
>     old = ...
>
> If the new encoding fails to parse, it tries the old one, and on
> transmission it uses the new one.  I find it very quick and convenient
> to bang out a new pickler now that I'm familiar with it.  You write your
> pickler and your unpickler with the same code - it works well.
>
> I am also working on hexpat-iteratee which is a lot more socket friendly
> since it doesn't use Haskell's lazy I/O.  The learning curve increases a
> little bit with doing it that way, though.
>
>
> Steve
>
> On 13/05/10 05:15, Ashish Agarwal wrote:
> > Thanks for all the advice. It seems I should avoid making my types
> > instances of Binary. In fact, this relates to another design issue I've
> > been grappling with, supporting multiple versions of the protocol.
> > Probably I'll need something like, putProtVersion1, putProtVersion2,
> > etc. Or something along this line.
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