Nullable types

[Bill Baxter]

On Tue, Oct 21, 2008 at 9:35 AM, Bill Baxter <wbaxter at gmail.com> wrote:
> On Tue, Oct 21, 2008 at 9:11 AM, Lionello Lunesu <lio at lunesu.remove.com> wrote:
>> Bent Rasmussen wrote:
>>>
>>> Not true. It wraps the value type in a struct with a boolean field
>>> expressing whether it is null or not.
>>>
>>> http://msdn.microsoft.com/en-us/library/1t3y8s4s(VS.80).aspx
>>
>> Indeed. Thanks for pointing that out.
>>
>> So C#'s 'foo?' syntax has even less to do with this compile-time nullness
>> checking.
>
> Now it makes sense.  Yes the C# feature is apparently just a
> convenient way to create a value type with a special
> "none-of-the-above" value.
> I guess this feature is driven by need to connect with databases that
> often have nullable types.
>
> This chapter of a C# 2.0 book covering Nullable Types seems to agree
> with that assessment :
> http://www.springerlink.com/content/w2mh0571776t3114/

Also C++ has *non*-Nullable types in the form of references.

void aFunction(ref Struct xyz) {
     // &xyz is a pointer that can't be null
}

ref Struct anotherFunction() {
    ...
}

&(anotherFunction()) --> can't be null

I think that may be a C++ FAQ  for "When do I use references vs
pointers?"  One answer to that is that if you don't want to allow
NULLs, use a reference.  If you do, then use a pointer.

--bb