Proposal : allocations made easier with non nullable types.

[Denis Koroskin]

Andrei Alexandrescu Wrote:

> 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.
> 

How about dynamic closures? It's way much harder to /properly/ determine whether a closure allocates that to determine if Foo foo; allocates But it reduces syntax complexity (by removing one syntax construct) and make structs and classes a little bit more intechangeble, which is a plus, I think.

> > 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.)
> 

I competely agree. Don't remember last time I used delete in D.

> 
> Andrei