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

[Brian Hurt <bhurt@spnz.org>]

On Thu, 15 Jul 2004, John Carr wrote:

> 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.

Yes, but in Some(0), the 0 is boxed (because of the Some)- so Some(0) is 
different from None.  I trust the type checker to make sure I can't have 0 
and None in the same variable, just like I trust the type checker to make 
sure I can't have 0 and false in the same variable.

> 
> Is there valid code (no Obj.magic) that cares that (Some None) and
> (None) are both represented by the same bit pattern?

let foo = function
    | None -> 0
    | Some(None) -> 1
    | Some(Some(_)) -> 2
;;

Now, wether you would actually see code like that in the "real world" is a 
different argument.

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Brian

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