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
