Proposal : allocations made easier with non nullable types.

[Andrei Alexandrescu]

Denis Koroskin wrote:
> On Mon, 09 Feb 2009 13:48:39 +0300, Alex Burton <alexibu at mac.com> wrote:
> 
>> I think it makes no sense to have nullable pointers in a high level 
>> language like D.
>>
>> In D :
>>
>> X x = new X;
>> This is a bit redundant, if we take away the ability to write X x; to 
>> mean X x = 0; then we can have X x; mean X x = new X;
>> If the class has a ctor then we can write X x(32); instead of X x = 
>> new X(32);
>> Only when the types of the pointer and class are different do we need 
>> to write X x = new Y;
>> We can do this syntactically in D because classes cannot be 
>> instantiated on the stack (unless scope is used, which I have found a 
>> bit pointless, as members are not scope so no deterministic dtor)
>>
>> This makes the code much less verbose and allows code to change from X 
>> being a struct to X being a class without having to go around and 
>> change all the X x; to X = new X;
>>
>> As I said in the nullable types thread:
>> Passing 0 or 0x012345A or anything else that is not a pointer to an 
>> instance of X to a variable declared as X x is the same as mixing in a 
>> bicycle when a recipe asks for a cup of olive oil.
>>
>> There are much better, and less error prone ways to write code in a 
>> high level language than allowing null pointers.
>>
>> Alex
> 
> I remember Andrei has showed interest in unification of the way value 
> and reference types are instantiated:
> 
> Foo foo(arg1, arg2); // valid instance, be it reference of value type
> Bar bar; // same here (default ctor is called)
> 
> and ditch 'new' keyword altogether.

That would be nice but Walter says he dislikes a dynamic allocation 
going under the covers.

> Note that you can't delete 
> non-nullable reference so 'delete' keyword is not needed, too (use scope 
> instead). Nullable types, however, may be recycled with e.g. 
> GC.delete(foo);

Delete-ing either non- or yes-nullable references is just as dangerous. 
IMHO the delete facility of the GC should be eliminated. (Long story.)


Andrei