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Date: Thu, 19 Aug 2010 09:34:57 -0400
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Subject: Re: [Caml-list] Question about float refs.
From: David House <dmhouse@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; val:01 val:01 caml-list:01 functions:01 int:01 int:01 define:02 float:03 float:03 let:03 let:03 refs:04 repr:04 repr:04 describe:07 

Note that you can directly observe boxedness using the Obj functions:

# type t1 = { a : float; b : int };;
type t1 = { a : float; b : int; }
# type t2 = { c : float; d : float };;
type t2 = { c : float; d : float; }
# let x1 = { a = 1.; b = 2 };;
val x1 : t1 = {a = 1.; b = 2}
# let x2 = { c = 3.; d = 4. };;
val x2 : t2 = {c = 3.; d = 4.}
# Obj.tag (Obj.repr x1);;
- : int = 0
# Obj.tag (Obj.repr x2);;
- : int = 254

For the use case you describe, I believe your best bet is to define a
float_ref type as you describe.