bitwise operations on registers

[Andrew Morton]

I'm sure I'm doing something silly.

(gdb) p $esp + 4
$15 = (void *) 0xca9c3ea4
(gdb) p $esp & 4
Argument to arithmetic operation not a number or boolean.
(gdb) 

I don't seem to be able to perform the `&' and `|' arithmetic
operators against machine registers.

GNU gdb Red Hat Linux (5.1.1-1)

Thanks.