Object-reference relation conditions
A data item of usage OBJECT
REFERENCE can be compared for equality or inequality with another data item of
usage OBJECT REFERENCE or with NULL, NULLS, or SELF.
| Format 4: object-reference |
 >>-+-object-reference-identifier-1-+--+----+--+-----+----------->
+-SELF--------------------------+ '-IS-' '-NOT-'
+-NULL--------------------------+
'-NULLS-------------------------'
>--+-EQUAL--+----+-+--+-object-reference-identifier-2-+--------><
| '-TO-' | +-SELF--------------------------+
'- = -----------' +-NULL--------------------------+
'-NULLS-------------------------'
|
A comparison with SELF is allowed only in a method.
Two object-references compare equal only if the data items identify the same
object.
|