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picking / marshaling to strings in ocaml-revision-stable way
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Date: -- (:)
From: Robert Fischer <robert@f...>
Subject: Re: [Caml-list] picking / marshaling to strings in ocaml-revision-stable way
How far is the reach from the Jane St S-exp library from producing JSON?  I've not actually looked
at it, but that'd be super nifty in the interoperation world.

~~ Robert.

Luca de Alfaro wrote:
> Thanks for this insight... I imagined the lack of robustness of Marshaling,
> but without all the details you mentioned!... actually, I DO desperately
> need speed, as I am processing TB's of Wikipedia data, but precisely because
> the datasets are so large, I cannot afford having to recompute / convert
> them often, and so I want a robust format. Furthermore, I think the
> bottleneck for me is anyway the speed of mysql and the disk, not really the
> small amount of time that natively compiled Ocaml would take for the
> conversion (I have anyway to do more complex computation that converting a
> few lists and datatypes to ascii, unfortunately).  Moreover, a plaintext
> format greatly helps debugging; it also helps that I can read the same data
> with other programming languages.
> 
> Speaking of debugging, and said in passing, I cannot say enough how much I
> LOVE the ability of ocamldebug of executing code backwards.  It is such a
> revelation.  You simply go to the error, then back off a bit to see how you
> got there.  But, this is a topic for another thread.
> 
> Many thanks,
> 
> Luca
> 
> 
> On Sat, May 31, 2008 at 2:38 AM, Berke Durak <berke.durak@gmail.com> wrote:
> 
>> I second Luca's suggestion to use Sexplib.  At the very least, use a
>> plaintext format.
>> Don't use Marshal for long-term storage of values.  Avoid it if you
>> can.  Been there, done that.
>> Why?
>>
>> (1) Not type-safe.  Translation: your program *wil segfault* and you
>> won't know why.
>> (2) Not human-readable nor editable.
>> (3) Not future-proof.  What happens if you change your type
>> definition?  Your program
>> will segfault.  So you'll have to migrate your data.  But how?  You'll
>> have to find
>> the exact revision used to generate the binary data.  Good luck with
>> that.  Did you put
>> a revision number in your data?  Are you sure it was up-to-date?  Then
>> you'll have to hand-write a converter that uses type declarations from
>> the old and the new modules.
>> I hope your dependencies are not too complex.  Not fun *at all*.
>>
>> However, there are some situations where Marshal is appropriate :
>>
>> (1) Your data is not acyclic, contains closures, or needs sharing to
>> be compact enough.  Sexplib doesn't handle these.
>> (2) The data won't live long anyway.  As in: you're doing IPC between
>> known versions of Ocaml programs.
>> (3) You desperately need speed.  As in: you're processing 200GB of
>> Wikipedia data.
>> Then I can understand.
>> --
>> Berke Durak
>>
> 
> 
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