Checking if a string is null

[Manfred Nowak]

Bruno Medeiros wrote

> I dont' get it, in D's arrays, what are the neutral elements 0 and
> 1? A zero length, and a one-length array, respectively? Or
> something else? And how can there be two different neutral
> elements? 

Please read here for a first impression: 
http://en.wikipedia.org/wiki/Kleene_algebra

Then notice, that D at least implicitely has the `+'-operator. It shows 
up in overloading. Therefore a 0 is needed.

There seem to be a consensus in the particpants of this thread that the 
1 in D's arrays is the array with length zero.

-manfred