References in D

[Franciszek Czekała" <home at valentimex.com>]

On Saturday, 15 September 2012 at 17:12:23 UTC, Jonathan M Davis 
wrote:
> 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

Agreed. Nullable types are a feature not a bug. There is no need 
to change it. Bugs occur when you do not know the language rules 
and make assumptions instead. This can happen whith any language 
and any rules. As to an example use of nullable references: 
consider a board game (for example chess). The boards has cells 
which can be empty or occupied. Model this with an array of class 
objects  representing pieces. null reference means a cell is not 
occupied. If you want to remove a piece from the board assign 
null to it and GC will take care of the rest. Now, doing this 
with full objects representing empty cells would require needless 
work to define such "null" objects and would be wasteful of 
memory (typically boards are sparsely populated). Now imagine a 
really big board and every cell holding references to useless 
objects simulating null references. It would not make sense. 
Saying that null references are evil is just propaganda. Let's 
keep D a sane language.