X 6.1.6.11.1 Using Parentheses

1. X Parentheses can be used to change the order of evaluation of the
   X logical operators AND and OR.

2. X The word NOT participates as part of the relational operator when it
   X is immediately followed by GREATER THAN, >, LESS THAN, <, EQUAL TO,
   X and =.

3. X NOT in any other position is considered a logical operator and thus
   X results in a negated relation-condition. If you use NOT as a logical
   X operator, only the relation condition immediately following the NOT is
   X negated; the negation is not propagated through the abbreviated
   X combined relation condition along with the subject and relational
   X operator.

4. X The logical NOT operator can appear within a parenthetical expression
   X that immediately follows a relational operator.

5. X When a left parenthesis appears immediately after the relational
   X operator, the relational operator is distributed to all objects
   X enclosed in the parentheses. In the case of a "distributed"
   X relational operator, the subject and relational operator remain
   X current after the right parenthesis which ends the distribution. The
   X following three restrictions apply to cases where the relational
   X operator is distributed throughout the expression:
   1. X A simple condition cannot appear within the scope of the
      X distribution.
   2. X Another relational operator cannot appear within the scope of the
      X distribution.
   3. X The logical operator NOT cannot appear immediately after the left
      X parenthesis, which defines the scope of the distribution.

6. X Evaluation proceeds from the least to the most inclusive condition.

7. X There must be a one-to-one correspondence between left and right
   X parentheses, with each left parenthesis to the left of its
   X corresponding right parenthesis. If the parentheses are unbalanced,
   X the compiler inserts a parenthesis and issues an E-level message.
   X Note, however, that if the compiler-inserted parenthesis results in
   X the truncation of the expression, you will receive an S-level
   X diagnostic message.

8. X The last stated subject is inserted in place of the missing subject.

9. X The last stated relational operator is inserted in place of the
   X missing relational operator.

10. X Insertion of the omitted subject and/or relational operator ends when:
    1. X Another simple condition is encountered,
    2. X A condition-name is encountered,
    3. X A right parenthesis is encountered that matches a left parenthesis
       X that appears to the left of the subject.

11. X In any consecutive sequence of relation conditions, you can use both
    X abbreviated relation conditions that contain parentheses and those
    X that don't.

12. X Consecutive logical NOT operators cancel each other and result in an
    X S-level message. Note, however, that an abbreviated combined relation
    X condition can contain two consecutive NOT operators when the second
    X NOT is part of a relational operator. For example, you can abbreviate
    X the first condition as the second condition listed below.

    
     X       A = B and not A not = C
     X       A = B and not not = C
    
    
    

X  Table 30. Abbreviated Combined Conditions--Permissible Element Sequences
X  Combined    X  Condition   X  Element	X         X  Left   X  most	X  When not leftmost,     X  can be immediately     X  preceded by:	X         X  Right  X  most	X  When not rightmost,   X  can be immediately    X  followed by:
X  Subject	X  Yes	X  NOT (	X  No	X  Relational operator
X  Object      X	X  No     X	X  Relational operator    X  AND OR NOT (	X  Yes    X	X  AND OR )              X
X  Relational  X  operator	X  No     X	X  Subject AND OR NOT     X	X  No     X	X  Object (              X
X  AND OR      X	X  No     X	X  Object )               X	X  No     X	X  Object Relational     X  operator NOT (
X  NOT         X              X	X  Yes    X         X	X  AND OR (               X                         X	X  No     X         X	X  Subject Object        X  Relational operator   X  (
X  (           X	X  Yes    X	X  Relational operator    X  AND OR NOT (	X  No     X	X  Subject Object NOT (  X
X  )	X  No	X  Object )	X  Yes	X  AND OR )

Table 31. Abbreviated Combined Conditions--Unabbreviated Equivalents
Abbreviated Combined Relation         Condition	Equivalent
A = B AND NOT < C OR D	((A = B) AND (A NOT < C))  OR (A      NOT < D)
A NOT > B OR C	(A NOT > B)  OR (A NOT > C)
NOT A = B OR C	(NOT (A = B)) OR (A = C)
X  NOT (A = B OR < C)	X  NOT ((A = B) OR (A < C))
X  NOT (A NOT = B AND C AND NOT D)      X	X  NOT ((((A NOT = B) AND (A NOT = C))  X   AND (NOT (A NOT = D))))

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