From: Anthony Tavener <anthony.tavener@gmail.com>
To: "Daniel Bünzli" <daniel.buenzli@erratique.ch>
Cc: caml list <caml-list@inria.fr>
Subject: Re: [Caml-list] Stability of order between polymorphic variants
Date: Wed, 4 Sep 2013 20:11:49 -0600 [thread overview]
Message-ID: <CAN=ouMQ+vC1uR4M3EqS8odZ2M+ohRY-wx7hD9ZA2Dz_c5wPzrA@mail.gmail.com> (raw)
In-Reply-To: <CAN=ouMR37Wszt1GT_t3+joaPkS9A1cQB8ONkwB86SfFVF3RkEA@mail.gmail.com>
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Addendum: On a 32b arch, those names will wrap.
On Wed, Sep 4, 2013 at 8:06 PM, Anthony Tavener
<anthony.tavener@gmail.com>wrote:
> I haven't looked at how the compare happens for polyvariants, but I assume
> it's going to treat them as integers. And the integer value of the
> polymorphic variants is a simple hashing-type function (byterun/hash.c:
> caml_hash_variant). A multiplication by 223 is involved for each character
> of the variant name, so with a long enough name, compared to the integer
> size, you'll get wraparound. The short names you have there are okay.
>
> I'd be uncomfortable relying on this ordering, but I can imagine it would
> make some things a lot simpler...
>
>
>
> On Wed, Sep 4, 2013 at 6:17 PM, Daniel Bünzli <daniel.buenzli@erratique.ch
> > wrote:
>
>> Hello,
>>
>> I have this type
>>
>> type weight = [ `W100 | `W200 | `W300 | `W400 | `W500 | `W600 | `W700 |
>> `W800 | `W900 ]
>>
>> In the current compiler it has the property that `Wx00 < `Wy00 if x < y.
>>
>> The question is, is the order between polymorphic variants an invariant
>> provided by the compiler or is it subject to change ?
>>
>> Best,
>>
>> Daniel
>>
>>
>>
>> --
>> Caml-list mailing list. Subscription management and archives:
>> https://sympa.inria.fr/sympa/arc/caml-list
>> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
>> Bug reports: http://caml.inria.fr/bin/caml-bugs
>>
>
>
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next prev parent reply other threads:[~2013-09-05 2:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-05 0:17 Daniel Bünzli
2013-09-05 2:06 ` Anthony Tavener
2013-09-05 2:11 ` Anthony Tavener [this message]
2013-09-05 2:18 ` Francois Berenger
2013-09-05 2:31 ` Anthony Tavener
2013-09-05 7:47 ` Stéphane Glondu
2013-09-05 8:24 ` Jacques Garrigue
2013-09-05 8:39 ` Mark Shinwell
2013-09-05 9:26 ` Jeremy Yallop
2013-09-05 14:46 ` Goswin von Brederlow
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