From: Francois Berenger <berenger@riken.jp>
To: caml-list@inria.fr
Subject: Re: [Caml-list] Stability of order between polymorphic variants
Date: Thu, 05 Sep 2013 11:18:34 +0900 [thread overview]
Message-ID: <5227E9FA.1020301@riken.jp> (raw)
In-Reply-To: <CAN=ouMQ+vC1uR4M3EqS8odZ2M+ohRY-wx7hD9ZA2Dz_c5wPzrA@mail.gmail.com>
On 09/05/2013 11:11 AM, Anthony Tavener wrote:
> Addendum: On a 32b arch, those names will wrap.
Why not write a to_int for your type
and then a specialized comparator using it?
> On Wed, Sep 4, 2013 at 8:06 PM, Anthony Tavener
> <anthony.tavener@gmail.com <mailto: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 <mailto: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
>
>
>
> --
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>
>
next prev parent reply other threads:[~2013-09-05 2:18 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
2013-09-05 2:18 ` Francois Berenger [this message]
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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