"".dup is null

[Steven Schveighoffer]

On Mon, 04 May 2009 10:22:49 -0400, Qian Xu <quian.xu at stud.tu-ilmenau.de>  
wrote:

> Steven Schveighoffer wrote:
>
>> I think you might have a bug?
>>
>> "".dup is the same as s.dup, not sure why you would expect it to be
>> not-null.
>>
>> -Steve
>
> If I have not explained clearly.
> Here is the full code:
>
>   char[] s;
>   assert(s     is null);
>   assert(s.dup is null);
>
>   assert(""     !is null); // OK
>   assert("".dup !is null); // FAILED
>
> At least the last two lines behave not consistent.
> Either both are failed, or both are passed.


OK, your original post was this:

   assert( s.dup  is null); // OK
   assert("".dup !is null); // FAILED


The compiler always returns a null array if you dup an empty array.  The  
reason being: why allocate memory for something that is zero length?

If anything, the oddity is this line:

assert("" !is null);

But of course, no memory is allocated for literals, so at least needless  
memory allocation does not occur.

To be consistent, I think assert("" is null); should pass, but it's a  
minor inconsistency at best.

I usually never compare arrays to null for this reason...

-Steve