Hi.

>> For instance, 0 gcd: 3 is 3. But the #gcd: on Squeak gives a division by 
zero 
>> error when the gcd is to be taken with a null argument.
>Huh?  In what sense is 0 generally null?

In the sense that I've seen the word null treated as if it was the number 
zero a lot of times... it was mathematical null, the zero.

Andres.