pointers, tests, casts

[Guy Harris]

>Otherwise, there are are implementations, those defining NULL as
>(char *)0, which will give an error on the latter statement.

Great!  That means that if I get an error, I get to throw rotten eggs at
the implementor.  It's a good test to see who understood what they were
doing when they implemented C.... 

If NULL is properly defined as specified by the dpANS, namely as 0 or
"(void *)0",

	if (ptr == 0)

and

	if (ptr == NULL)

are equivalent.