Denis Koroskin wrote:
> On Sun, 27 Sep 2009 03:01:48 +0400, Walter Bright
> <newshou...@digitalmars.com> wrote:
>
>> Denis Koroskin wrote:
>>> One more:
>>> T foo(bool someCondition)
>>> {
>>> T? t;
>>> if (someCondition) t = someInitializer();
>>> // ...
>>> if (t.isNull) { // not initialized yet
>>> // ...
>>> }
>>> return enforce(t); // throws if t is not initialized yet,
>>> because foo *must* return a valid value by a contract
>>> }
>>
>> It seems to me you've got null references there anyway?
>>
>> What would you do about:
>>
>> T[] a;
>> a[i] = foo();
>>
>> where you want to have unused slots be null (or empty, or nothing)?
>
> Easy:
>
> T? foo(); // returns valid object or a null
>
> T?[] a;
> a[i] = foo();
The case of a non-null array is, I think, worthy of some more consideration.
These are the things that would not be possible with a non-nullable array:
- newing it
- setting .length to a greater value
- appending a nullable array of the same base type.
Basically, anything that may fill it with nulls.
The only two allowed instructions would be ~= NonNullable and ~=
NonNullableArray. And it's good that way.
