Checking if a string is null

[Don Clugston]

Regan Heath wrote:
>>> The only thing that should compare equal to null is null.  Likewise 
>>> an empty array should only compare equal to another empty array.
>>  >
>>  > My reasoning for this is consistency, see at end.
>>
>> Since null arrays have length 0, they *are* empty arrays :P.
> 
> I can't tell in which way you're joking so I'm just going to come out 
> with...
> 
> The length of something be it an array, a car, a <insert thing> is 
> totally independant of whether it exists (though a non-existant item 
> cannot have a length).
> 
> It either exists or it does not.  If it exists, it has a length which 
> may or may not be zero.
> 
> Something which exists cannot be equal to something which doesn't.

I don't think that's really what's happening here.
Consider vectors. If a vector has a length of zero, the direction doesn't exist.
Take two arbitrary vectors with different directions, a and b.
a*0 == b*0, even though the direction of a is completely different to that of b.
This is the same model which is being used for arrays; if the .length is zero, 
the .ptr is irrelevant.