From: Karl Zilles <zilles@1969.ws>
To: John Carr <jfc@mit.edu>
Cc: caml-list@inria.fr
Subject: Re: [Caml-list] Unboxing options, was RE: assertions or exceptions?
Date: Thu, 15 Jul 2004 14:15:54 -0700 [thread overview]
Message-ID: <40F6F40A.6080708@1969.ws> (raw)
In-Reply-To: <200407152049.i6FKnnSd004687@psi-phi.mit.edu>
John Carr wrote:
> [None represented internally as 0]
>
>
>>What's the representation of Some(None) then? The Some() goes away, and
>>the containing value is unboxed- it turns out to be the same as just None.
>>There is no way to differentiate Some(Some(Some(Some(None)))) from None.
>
>
> There is also no way to distinguish 0 from None in the current
> system. OCaml relies on type information to determine the meaning
> of a value.
0 and None are different types. There is no need to distinguish them.
>
> Is there valid code (no Obj.magic) that cares that (Some None) and
> (None) are both represented by the same bit pattern?
(Some None) and (None) are both the same type: a' option option
Valid code:
match x with
| Some a -> printf "Some!"
| None -> printf "None!"
(Some None) should print Some!, (None) should print None!, but since the
bit patterns are now the same...
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next prev parent reply other threads:[~2004-07-15 21:13 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-15 8:03 [Caml-list] " Radu Grigore
2004-07-15 10:18 ` Richard Jones
2004-07-15 10:28 ` Daniel Andor
2004-07-15 12:49 ` Radu Grigore
2004-07-15 13:33 ` Richard Jones
2004-07-15 13:58 ` Radu Grigore
2004-07-16 18:53 ` Aleksey Nogin
2004-07-17 2:55 ` John Prevost
2004-07-17 14:24 ` David MENTRE
2004-07-15 12:35 ` Jon Harrop
2004-07-15 13:45 ` Radu Grigore
2004-07-15 14:33 ` Jon Harrop
2004-07-15 15:05 ` Radu Grigore
2004-07-15 16:24 ` skaller
2004-07-15 15:38 ` [Caml-list] Unboxing options, was " Brian Hurt
2004-07-15 16:25 ` John Hughes
2004-07-15 17:00 ` Brian Hurt
2004-07-15 17:20 ` John Prevost
2004-07-15 19:14 ` Radu Grigore
2004-07-15 19:56 ` John Carr
2004-07-15 20:48 ` Brian Hurt
2004-07-15 20:49 ` John Carr
2004-07-15 21:15 ` John Prevost
2004-07-15 21:15 ` Karl Zilles [this message]
2004-07-15 21:26 ` Brian Hurt
2004-07-15 21:04 ` John Prevost
2004-07-15 21:17 ` skaller
2004-07-15 21:35 ` Brian Hurt
2004-07-15 21:51 ` skaller
2004-07-15 21:42 ` skaller
2004-07-16 0:35 ` Jacques GARRIGUE
2004-07-16 1:03 ` John Prevost
2004-07-16 2:00 ` Jacques GARRIGUE
2004-07-16 16:40 ` Xavier Leroy
2004-07-19 8:58 ` Damien Doligez
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