Re: [Caml-list] Unboxing options, was RE: assertions or exceptions?

[John Prevost <j.prevost@gmail.com>]

On Fri, 16 Jul 2004 09:35:17 +0900 (JST), Jacques GARRIGUE
<garrigue@kurims.kyoto-u.ac.jp> wrote:
> The idea is just to reserve a sufficiently large memory area to
> represent every needed (Some (Some ...(Some None) ...)).

Apologies for keeping the conversation going, but since I just thought of this:

Caml's internal pointers are at minimum 4-byte aligned.  What about
using the other "safe" set of trailing bits, "10", to mark options? 
i.e.:

None = ...0010 (2)
Some None =  ...0110 (6)
Some Some None = ...1010 (10)
Some Some Some None = ...1110 (14)

and so on?  This would remove the need to use a special memory area
(or check that area) for wrapping and unwrapping.  There'd still be a
cost, but I would think it should be smaller than the cost you
describe?

That said, I also don't think this is a critical issue.

John.

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