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Date: Thu, 19 Aug 2010 15:14:17 +0200
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Subject: Re: [Caml-list] Question about float refs.
From: Lukasz Stafiniak <lukstafi@gmail.com>
To: Ethan Burns <burns.ethan@gmail.com>
Cc: caml-list@yquem.inria.fr, Wheeler Ruml <ruml@cs.unh.edu>
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X-Spam: no; 0.00; lukasz:01 mutable:01 ocaml:01 pervasives:01 mutable:01 unboxed:01 foo:01 burns:98 burns:98 polymorphic:01 polymorphic:01 wrote:01 caml-list:01 defined:02 seems:03 

On Thu, Aug 19, 2010 at 1:52 PM, Ethan Burns <burns.ethan@gmail.com> wrote:
> Hello,
>
> I noticed a strange behavior when using references to floating point
> values. =A0My suspicion, initially, was that the references would not be
> boxed because they are the same as a record with a single mutable
> field that is of type float. =A0It seems that OCaml still boxes float
> refs.

Note that refs are just a standard polymorphic type defined in Pervasives:

  type 'a ref =3D {
    mutable contents : 'a ;
  }

Being polymorphic, the "float ref" are not unboxed: imagine what would
happen when you passed them to a function

foo : 'a ref -> 'a list =3D fun x -> [ !x ]

or similar (with a negative occurrence of polymorphic ref).