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Date: Thu, 15 Oct 1998 19:25:27 +0200
From: Xavier Leroy <Xavier.Leroy@inria.fr>
To: Don Syme <dsyme@microsoft.com>, caml-list@inria.fr
Subject: Re: Boxing wrt. unary constructors
References: <39ADCF833E74D111A2D700805F1951EF0B2EF53D@RED-MSG-06>
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In-Reply-To: <39ADCF833E74D111A2D700805F1951EF0B2EF53D@RED-MSG-06>; from Don Syme on Wed, Oct 14, 1998 at 02:43:31AM -0700
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> This is probably a FAQ, but if I have a type
>   type abc = ABC of int
> then does Ocaml 2.00 use a boxed or unboxed repr. of values of this
> type?

Boxed.  While it would not be hard to make a special case for
one-constructor datatypes, this is not currently done in the OCaml
compiler.  However, you can use type abstraction to obtain much of the
same effects while keeping an unboxed representation:

        (struct type abc = int  let abc x = x  let proj_abs x = x end :
         sig    type abc     val abc: int->abc   val proj_abc: abc->int end)

Regards,

- Xavier Leroy