6.1.6.4.3 "COBOL Language Reference" IBM Library Server

X 6.1.6.4.3 Pointer Data Items

X Only EQUAL and NOT EQUAL are allowed as relational operators when
X specifying pointer data items. Pointer data items are items defined
X explicitly as USAGE IS POINTER, or are ADDRESS OF special registers, which
X are implicitly defined as USAGE IS POINTER.

X The operands are equal if the two addresses used in the comparison would
X both result in the same storage location.

X This relation condition is allowed in IF, PERFORM, EVALUATE, and SEARCH
X Format 1 statements. It is not allowed in SEARCH Format 2 (SEARCH ALL)
X statements, because there is no meaningful ordering that can be applied to
X pointer data items.


 X  ___ Format 2 ___________________________________________________________ 
 X |                                                                        |
 X | >>__ _ADDRESS OF__identifier-1_ __ ____ __ _____ ____________________> |
 X |     |_identifier-2_____________|  |_IS_|  |_NOT_|                      |
 X |     |_NULL_____________________|                                       |
 X |     |_NULLS____________________|                                       |
   |                                                                        |
 X | >__ _EQUAL__ ____ _ __ _ADDRESS OF__identifier-3_ __________________>< |
 X |    |        |_TO_| |  |_identifier-4_____________|                     |
 X |    |_=_____________|  |_NULL_____________________|                     |
 X |                       |_NULLS____________________|                     |
   |                                                                        |
   |________________________________________________________________________|

X identifier-1

X identifier-3

X Can specify any level item defined in the Linkage Section, except 66
X and 88.

X identifier-2

X identifier-4

X Must be described as USAGE IS POINTER.

X NULL(S)

X As in this syntax diagram, can be used only if the other operand is
X defined as USAGE IS POINTER. That is, NULL=NULL is not allowed.

X Table 23 summarizes the permissible comparisons for USAGE IS POINTER,
X NULL, and ADDRESS OF.

X X X First Operand	X USAGE IS X POINTER	X X ADDRESS OF	X X NULL/NULLS

X Table 23. Permissible Comparisons for USAGE IS POINTER, NULL, and ADDRESS X OF
X X X First Operand	X Second Operand
X USAGE IS POINTER	X Yes	X Yes	X Yes
X ADDRESS OF	X Yes	X Yes	X Yes
X NULL/NULLS	X Yes	X Yes	X No
X Note: X YES = Comparison allowed only for EQUAL, NOT EQUAL X NO = No comparison allowed

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X 6.1.6.4.3 Pointer Data Items

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