Proposal : allocations made easier with non nullable types.

[Alex Burton]

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();
> }

I would try to never write code like that.
The reason being if the if statement becomes a bit more complicated you risk leaving x = 0;
Better to write a small function:

X getX(bool someCondition)
{
 if(someCondition) {
    return new SomeX();
 } else {
    return new SomeOtherX();
 }
}

That way the compiler will have to tell you if X can be possibly returned null.

Alex