Nullable types

[Bent Rasmussen]

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

- Bent

"Lionello Lunesu" <lio at lunesu.remove.com> skrev i meddelelsen 
news:gdhs01$1jnp$1 at digitalmars.com...
> samabeau wrote:
>> Lionello Lunesu Wrote:
>>
>>> * Are there any other languages with this concept?
>>
>> C# does. Nullable types have a question mark after them.
>> eg:-
>>
>> int? num = null;
>>
>> http://msdn.microsoft.com/en-us/library/1t3y8s4s(VS.80).aspx
>>
>
> In C#, that "?" basically wraps (boxes?) a value type into a reference 
> type.
>
> Once you have an object reference (either an instanced class or such a 
> wrapped value type) you still must check for null everywhere you use it. 
> And in some situations you just know it's never null and you would like to 
> use that information.
>
> At the moment, the way you can tell that an object is never null is by
> (1) using an assertion;
> (2) mentioning it in a comment;
> (3) using some hungarian-like naming scheme;
>
> None of which have any value at compile-time. In fact, if you think those 
> 3 alternatives are good enough, you could drop all the compile-time type 
> checking.
>
> And what happens nowadays when none of those 3 is present? You check for 
> null, whether the check makes sense or not. If I'd only get a penny for 
> every if-null check I've encountered...
>
> Letting the type system track whether a reference is null or not should 
> result in more readable code. No more wondering "What if x is null? 
> Where's it checked?" and no more "let's check for null, just in case."
>
> L.