When is a cast not a cast?

[Andrew Koenig]

In article <2747 at buengc.BU.EDU>, bph at buengc.BU.EDU (Blair P. Houghton) writes:

> 3	char *c;
> 4	char *p;
> 5	int i;
> 6	...
> 7	c = "somestring";  /* Nothing fancy, null-terminated. */
> 8	i = 4;  /* For example. */

> 10 	p = (c + (char *) i);  /* More trouble than it's worth... */

> wherupon both the lint(1) and cc(1) in my Ultrix 2.2 piped-up with
> warnings that the 'operands of + have incompatible types' on line 10...

Correct.  You cannot add two pointers -- you can only add
a pointer and an integer.

You can SUBTRACT two pointers (to the same type); the result
of that is an integer, not a pointer.

If p is a pointer to element n of some array, then p+i is a
pointer to element n+i of that array.

If p isn't a pointer to an array element, you're on your own.
[C-T&P, p. 29]
-- 
				--Andrew Koenig
				  ark at europa.att.com