arrays: if(null == [ ])

[deadalnix]

Le 16/05/2012 23:15, Steven Schveighoffer a écrit :
> On Wed, 16 May 2012 17:11:58 -0400, deadalnix <deadalnix at gmail.com> wrote:
>
>> Le 16/05/2012 15:12, Steven Schveighoffer a écrit :
>>> On Tue, 15 May 2012 04:42:10 -0400, deadalnix <deadalnix at gmail.com>
>>> wrote:
>>>
>>>> Le 14/05/2012 21:53, Steven Schveighoffer a écrit :
>>>>> On Mon, 14 May 2012 15:30:25 -0400, deadalnix <deadalnix at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Le 14/05/2012 16:37, Steven Schveighoffer a écrit :
>>>>>>> Note that [] is a request to the runtime to build an empty array.
>>>>>>> The
>>>>>>> runtime detects this, and rather than consuming a heap allocation to
>>>>>>> build nothing, it simply returns a null-pointed array. This is 100%
>>>>>>> the
>>>>>>> right decision, and I don't think anyone would ever convince me (or
>>>>>>> Andrei or Walter) otherwise.
>>>>>>>
>>>>>>
>>>>>> Obviously this is the right thing to do !
>>>>>>
>>>>>> The question is why an array of length 0 isn't nulled ? It lead to
>>>>>> confusing semantic here, and can keep alive memory that can't be
>>>>>> accessed.
>>>>>
>>>>> int[] arr;
>>>>> arr.reserve(10000);
>>>>> assert(arr.length == 0);
>>>>>
>>>>> -Steve
>>>>
>>>> The length isn't set to 0 here. You obviously don't want that to be
>>>> nulled.
>>>
>>> The assert disagrees with you :)
>>>
>>> -Steve
>>
>> The length IS 0. It IS 0 before the call to reserve. It is never SET
>> to 0.
>
> OK, so it's allowed to be 0 and not-null. doesn't this lead to the
> confusing semantics you were talking about?
>
> What about this?
>
> int[] arr;
> arr.reserve(10000);
>
> int[] arr2 = [1,2,3];
> arr2 = arr; // now length has been *set* to 0, should it also be nulled?
>
> But I want arr2 and arr to point at the same thing, maybe I'm not using
> arr anymore. Maybe I returned it from a function, and I no longer have
> access to arr.
>
> -Steve

That make sense :D