Checking if a string is null

[Regan Heath]

Bruno Medeiros wrote:
> Frits van Bommel wrote:
>> Regan Heath wrote:
>>> This all boils down to the empty vs null string debate where some 
>>> people want to be able to distinguish between them and some see no 
>>> point.
>>>
>>> I'm in the 'distinguishable' camp.  I can see the merit.  At the very 
>>> least it should be consistent!
>>
>> They *are* distinguishable. That's why above code returns different 
>> results for the 'is' comparison...
>>
> 
> The .ptr of empty arrays may be different than the .ptr of null arrays, 
> but they are conceptually the same, and thus not safely distinguishable.
> Example:
>     writefln("" is null); // false
>     writefln("".dup is null); // true
> 
> "".ptr is not null, but "".dup.ptr is null. Such duplication is correct, 
> because empty arrays are conceptually the same as null arrays, and 
> trying to use .ptr do distinguish them is unsafe, 
> implementation-depedendent behavior (aka a program error).

Ick.  IMO "".dup should allocate 1 byte of memory, set it to '\0' and 
create a reference to it with length of 0.

What do you mean by "empty arrays are conceptually the same as null 
arrays"?

To me null arrays (non-existant) and "" arrays (empty) are conceptually 
different.  null indicates the array does not exist (no set at all), "" 
indicates it does but contains no items (an empty set).

Regan