Proposal : allocations made easier with non nullable types.

[Don]

Ary Borenszweig wrote:
> Alex Burton 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
> 
> How would you do this?
> 
> X x;
> 
> if(someCondition) {
>   x = new SomeX();
> } else {
>   x =  new SomeOtherX();
> }

That's interesting, because even there, you don't want X to be a 
nullable type. You don't want x to be readable AT ALL until one of the 
constructor calls has happened.

In fact, there's already a syntax for this. The solution is:

X x = void;
if(someCondition) {
    x = new SomeX();
} else {
    x =  new SomeOtherX();
}