References in D

[Regan Heath]

On Sun, 16 Sep 2012 23:46:34 +0100, deadalnix <deadalnix at gmail.com> wrote:

> Le 15/09/2012 19:13, Jonathan M Davis a écrit :
>> On Saturday, September 15, 2012 15:24:27 Henning Pohl wrote:
>>> On Saturday, 15 September 2012 at 12:49:23 UTC, Russel Winder
>>>
>>> wrote:
>>>> On Sat, 2012-09-15 at 14:44 +0200, Alex Rønne Petersen wrote:
>>>> […]
>>>>
>>>>> Anyway, it's too late to change it now.
>>>>
>>>> I disagree. There are always opportunities to make changes to
>>>> things,
>>>> you just have manage things carefully.
>>>
>>> I don't know if people really use the ability of references being
>>> null. If so, large amounts of code will be broken.
>>
>> Of course people use it. Having nullable types is _highly_ useful. It  
>> would
>> suck if references were non-nullable. That would be _horrible_ IMHO.  
>> Having a
>> means to have non-nullable references for cases where that makes sense  
>> isn't
>> necessarily a bad thing, but null is a very useful construct, and I'd  
>> _hate_
>> to see normal class references be non-nullable.
>>
>> - Jonathan M Davis
>
> Years of java have proven me the exact opposite. Nullable is a usefull  
> construct, but nullable by default is on the wrong side of the force.

I think it depends on your background.  Most of my experience has been  
with C and C++ and I agree with Jonathan that null is incredibly useful,  
and something I use a lot.  In fact, I am often annoyed that 'int' doesn't  
have an equivalent value, and instead I have to invent a magic number and  
ensure it's never a possible valid value.

What I've noticed looking at Java code written by others is that null as a  
possible state is ignored by the vast bulk of the code, which is  
completely the opposite when reviewing C/C++ code where null is checked  
for and handled where applicable.  I think it's a mindset thing brought on  
by the language, or how it's taught, or something.  It seems to me that  
Java would have benefited from non-null references :p

My uses of null all seem to boil down to being able to represent something  
as being "not there yet" or "not specified" etc without having to resort  
to a magic value, or 2nd flag/boolean/parameter.  I find null is a nice  
clean way to do this.

As to whether it should be the default or not.. well, you might have a  
point there.  I think I probably want to use null less than otherwise.

But, all we need is a compiler which says "Oi, you haven't initialised  
this" forcing me to explicitly set it to null where desired, or a valid  
value and problem solved, right?  That combined with a construct like  
NotNull!(T) which would assert in debug that the reference is not null and  
you can basically stop doing null checks in release code.  Win win, right?

R

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