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<title>*AND, *OR, and *NOT operators</title>
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<body id="expr"><a name="expr"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">*AND, *OR, and *NOT operators</h1>
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<div><p>The logical operators *AND and *OR specify the relationship between
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operands in a logical expression. The logical operator *NOT is used to negate
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logical variables or constants.</p>
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<div class="section"><p>*AND and *OR are the reserved values used to specify the relationship
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between operands in a logical expression. The ampersand symbol (&) can
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replace the reserved value *AND, and the vertical bar (|) can replace *OR.
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The reserved values must be preceded and followed by blanks. The operands
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in a logical expression consist of relational expressions or logical variables
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or constants separated by logical operators. The *AND operator indicates that
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both operands (on either side of the operator) have to be true to produce
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a true result. The *OR operator indicates that one or the other of its operands
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must be true to produce a true result. </p>
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<div class="note"><span class="notetitle">Note:</span> Using the ampersand symbol
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or the vertical bar can cause problems because the symbols are not at the
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same code point for all code pages. To avoid this, use *AND and *OR instead
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of the symbols.</div>
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<p>Use operators other than logical operators in expressions
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to indicate the actions to perform on the operands in the expression or the
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relationship between the operands. There are three kinds of operators other
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than logical operators: </p>
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<ul><li>Arithmetic (+, -, *, /)</li>
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<li>Character (*CAT, ||, *BCAT, |>, *TCAT, |<)</li>
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<li>Relational (*EQ, =, *GT, >, *LT, <, *GE, >=, *LE, <=, *NE,
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¬=, *NG, ¬>, *NL, ¬<)</li>
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</ul>
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<p>The following are examples of logical expressions: </p>
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<pre>((&C *LT 1) *AND (&TIME *GT 1430))
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(&C *LT 1 *AND &TIME *GT 1430)
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((&C < 1) & (&TIME>1430))
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((&C< 1) & (&TIME>1430))</pre>
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<p>In each of these cases, the logical expression consists of
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three parts: two operands and one operator (*AND or *OR, or their symbols).
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It is the type of operator (*AND or *OR) that characterizes the expression
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as logical, not the type of operand. Operands in logical expressions can
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be logical variables or other expressions, such as relational expressions.
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(Relational expressions are characterized by &gt, &lt, or = symbols
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or corresponding reserved values.) For instance, in following example the
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entire logical expression is enclosed in parentheses, and both operands are
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relational expressions, also enclosed separately in parentheses:</p>
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<pre>((&C *LT 1) *AND (&TIME *GT 1430))</pre>
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<p>As you can see from the second example of logical expressions,
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the operands need not be enclosed in separate parentheses, but it is recommended
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for clarity. Parentheses are not needed because *AND and *OR have different
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priorities. *AND is always considered before *OR. For operators of the same
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priority, parentheses can be used to control the order in which operations
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are performed.</p>
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<p>A simple relational expression can be written as the
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condition in a command:</p>
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<pre>IF (&A=&B) THEN(DO)
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.
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.
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.
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ENDDO</pre>
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<p>The operands in this relational expression could also be constants.</p>
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<p>If
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you wish to specify more than one condition, you can use a logical expression
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with relational expressions as operands:</p>
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<pre>IF ((&A=&B) *AND (&C=&D)) THEN(DO)
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.
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.
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.
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ENDDO</pre>
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<p>The series of dependent IF commands cited as an example in <a href="embif.htm#embif">Embedded IF commands</a> could be coded:</p>
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<pre>PGM
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DCL &RESP *DEC 1
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DCL &A *DEC 1
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DCL &B *CHAR 2
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IF ((&RESP=1) *AND (&A=5) *AND (&B=NO)) THEN(DO)
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.
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.
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.
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ENDDO
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CHGVAR &A VALUE(8)
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CALLPRC PROC(DAILY)
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ENDPGM</pre>
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<p>Here the logical operators are again used between relational
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expressions.</p>
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<p>Because a logical expression can also have other logical
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expressions as operands, quite complex logic is possible:</p>
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<pre>IF (((&A=&B) *OR (&A=&C)) *AND ((&C=1) *OR (&D='0'))) THEN(DO)</pre>
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<p>In this case, &D is defined as a logical variable.</p>
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<p>The
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result of the evaluation of any relational or logical expression is a '1'
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or '0' (true or false). The dependent command is processed only if the complete
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expression is evaluated as true ('1'). The following command is interpreted
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in these terms: </p>
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<pre>IF ((&A = &B) *AND (&C = &D)) THEN(DO)
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((<em>true'1'</em>) *AND (<em>not true'0'</em>))
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(<em>not true '0'</em>)</pre>
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<p>The expression is finally evaluated as not true ('0'), and,
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therefore, the DO is not processed. For an explanation of how this evaluation
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was reached, see the matrices later in this section.</p>
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<p>This same process
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is used to evaluate a logical expression using logical variables, as in this
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example:</p>
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<pre>PGM
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DCL &A *LGL
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DCL &B *LGL
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IF (&A *OR &B) THEN(CALL PGM(PGMA))
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.
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.
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.
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ENDPGM</pre>
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<p>Here the conditional expression is evaluated to see if the
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value of &A or of &B is equal to '1' (true). If either is true, the
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whole expression is true, and PGMA is called.</p>
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<p>The final evaluation arrived
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at for all these examples of logical expressions is based on standard matrices
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comparing two values (referred to here as &A and &B) under an *OR
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or *AND operator.</p>
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<p>Use the following matrix when using *OR with logical
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variables or constants: </p>
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<dl><dt class="dlterm">If &A is:</dt>
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<dd>'0' '0' '1' '1'</dd>
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<dt class="dlterm">and &B is:</dt>
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<dd>'0' '1' '0' '1'</dd>
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<dt class="dlterm">the OR expression is:</dt>
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<dd>'0' '1' '1' '1'</dd>
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</dl>
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<p>In short, for multiple OR operators with logical variables
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or constants, the expression is false ('0') if all values are false. The
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expression is true ('1') if any values are true.</p>
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<pre>PGM
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DCL &A *LGL VALUE('0')
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DCL &B *LGL VALUE('1')
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DCL &C *LGL VALUE('1')
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IF (&A *OR &B *OR &C) THEN(CALL PGMA)
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.
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.
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.
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ENDPGM</pre>
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<p>Here the values are not all false; therefore, the expression
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is true, and PGMA is called.</p>
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<p>Use the following matrix when evaluating
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a logical expression with *AND with logical variables or constants:</p>
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<dl><dt class="dlterm">If &A is:</dt>
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<dd>'0' '0' '1' '1'</dd>
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<dt class="dlterm">and &B is:</dt>
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<dd>'0' '1' '0' '1'</dd>
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<dt class="dlterm">the ANDed expression is:</dt>
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<dd>'0' '0' '0' '1'</dd>
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</dl>
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<p>For multiple AND operators with logical variables or constants,
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the expression is false ('0') when any value is false, and true when they
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are all true. </p>
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<pre>PGM
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DCL &A *LGL VALUE('0')
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DCL &B *LGL VALUE('1')
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DCL &C *LGL VALUE('1')
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IF (&A *AND &B *AND &C) THEN(CALL PGMA)
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.
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.
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.
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ENDPGM</pre>
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<p>Here the values are not all true; therefore, the expression
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is false, and PGMA is not called.</p>
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<p>These logical operators can only be
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used <em>within</em> an expression when the operands represent a logical value,
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as in the preceding examples. It is <em>incorrect</em> to attempt to use OR
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or AND for variables that are not logical. For instance: </p>
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<pre>PGM
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DCL &A *CHAR 3
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DCL &B *CHAR 3
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DCL &C *CHAR 3
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Incorrect: IF (&A *OR &B *OR &C = YES) THEN...</pre>
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<p>The correct coding for this would be:</p>
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<pre>IF ((&A=YES) *OR (&B=YES) *OR (&C=YES)) THEN...</pre>
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<p>In this case, the ORing occurs between relational expressions.</p>
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<p>The
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logical operator *NOT (or ¬) is used to negate logical variables or constants.
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Any *NOT operators must be evaluated before the *AND or *OR operators are
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evaluated. Any values that follow *NOT operators must be evaluated before
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the logical relationship between the operands is evaluated. </p>
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<pre>PGM
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DCL &A *LGL '1'
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DCL &B *LGL '0'
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IF (&A *AND *NOT &B) THEN(CALL PGMA)</pre>
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<p>In this example, the values are all true; therefore, the expression
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is true, and PGMA is called. </p>
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<pre>PGM
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DCL &A *LGL
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DCL &B *CHAR 3 VALUE('ABC')
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DCL &C *CHAR 3 VALUE('XYZ')
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CHGVAR &A VALUE(&B *EQ &C)
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IF (&A) THEN(CALLPRC PROCA)</pre>
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<p>In this example, the value is false, therefore, PROCA is not
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called.</p>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="contp.htm" title="You can use commands to change the flow of logic within your CL procedure.">Control processing within a CL procedure</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="ifcmd.htm" title="The IF command is used to state a condition that, if true, specifies some statement or group of statements in the procedure to be run.">IF command</a></div>
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<div><a href="elsec.htm" title="The ELSE command is a way of specifying alternative processing if the condition on the associated IF command is false.">ELSE command</a></div>
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<div><a href="embif.htm" title="An IF command can be embedded in another IF command.">Embedded IF commands</a></div>
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<div><a href="dountilcmd.htm" title="The Do Until (DOUNTIL) command processes a group of CL commands one or more times.">DOUNTIL command</a></div>
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<div><a href="dowhilecmd.htm" title="The DOWHILE command lets you process a group of commands zero or more times while the value of a logical expression is true.">DOWHILE command</a></div>
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<div><a href="selectcmd.htm" title="The Select (SELECT) command is used to identify one or more conditions and an associated group of commands to process when that condition is true.">SELECT command and SELECT groups</a></div>
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