Nullable or Optional? Or something else?

[Danny Wilson]

Op Wed, 02 Sep 2009 22:20:04 +0200 schreef Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org>:

> Jarrett Billingsley wrote:
>> On Wed, Sep 2, 2009 at 4:13 PM, Simen Kjaeraas<simen.kjaras at gmail.com>  
>> wrote:
>>> Danny Wilson <bluezenix at gmail.com> wrote:
>>>
>>>> Op Wed, 02 Sep 2009 21:39:28 +0200 schreef Andrei Alexandrescu
>>>> <SeeWebsiteForEmail at erdani.org>:
>>>>
>>>>> I plan to add a Nullable struct to Phobos (akin to C#'s Nullable,  
>>>>> Boost's
>>>>> Optional).
>>>>>
>>>>> Apparently a good design is to define Optional!T with a minimum of  
>>>>> member
>>>>> functions (ideally none) and have it use the "alias this" feature to
>>>>> masquerade as a T. That way Optional!T looks and feels much like a  
>>>>> T, except
>>>>> that it supports a function
>>>>>
>>>>> bool isNull(T)(Optional!T value);
>>>>>
>>>>> Am I on the right track? If so, what is the name you'd prefer for  
>>>>> this
>>>>> artifact?
>>>>>
>>>>>
>>>>> Andrei
>>>>
>>>> How about:  Maybe!T
>>>>
>>>>
>>>> Got that from Haskell :-)
>>> I also feel the bikeshed should be colored 'Maybe'.
>>  Thirded!
>
> Great. Now, before we get all jolly about Maybe, let me point out that  
> we also need the "ref" corresponding type. And OptionalRef and  
> NullableRef may sound better to some than MaybeRef.
>
> Andrei

So if pointers wouldn't be considered evil,  Maybe!T*  would suffice?

Can someone point me out what the big difference is between ref and simply  
disallowing pointer arithmitic?  Is it marketing?