144 lines
7.9 KiB
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144 lines
7.9 KiB
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<title>IF command</title>
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<body id="ifcmd"><a name="ifcmd"><!-- --></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">IF command</h1>
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<div><p>The IF command is used to state a condition that, if true, specifies
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some statement or group of statements in the procedure to be run. </p>
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<div class="section"><p> The ELSE command can be used with the IF command to specify a
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statement or group of statements to be run if the condition expressed by the
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IF command is false.</p>
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<p>The command includes an expression, which is tested
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(true or false), and a THEN parameter that specifies the action to be taken
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if the expression is true. The IF command is formatted as follows:</p>
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<pre>IF COND(logical-expression) THEN(CL-command)</pre>
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<p>The logical expression on the COND parameter may be a single
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logical variable or constant, or it must describe a relationship between two
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or more operands; the expression is then evaluated as true or false.</p>
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<p>If
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the condition described by the logical expression is evaluated as true, the
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procedure processes the CL command on the THEN parameter. This may be a single
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command, or a group of commands. If the condition is not true, the procedure
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runs the next sequential command.</p>
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<p>Both COND and THEN are keywords on
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the command, and they can be omitted for positional entry. The following
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are syntactically correct uses of this command:</p>
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<pre>IF COND(&RESP=1) THEN(CALL CUS210)
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IF (&A *EQ &B) THEN(GOTO LABEL)
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IF (&A=&B) GOTO LABEL</pre>
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<p>Blanks are required between the command name (IF) and the keyword
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(COND) or value (&A). No blanks are permitted between the keyword, if
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specified, and the left parenthesis enclosing the value.</p>
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<p>The following
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is an example of conditional processing with an IF command. Processing branches
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in different ways depending on the evaluation of the logical expression in
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the IF commands. Assume, for instance, that at the start of the following
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code, the value of &A is 2 and the value of &C is 4. </p>
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<pre> IF (&A=2) THEN(GOTO FINAL)
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IF (&A=3) THEN(CHGVAR &C 5)
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.
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.
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.
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FINAL: IF (&C=5) CALL PROGA
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ENDPGM</pre>
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<p>In this case, the procedure processes the first IF command
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before branching to FINAL, skipping the intermediate code. It does not return
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to the second IF command. At FINAL, because the test for <samp class="codeph">&C=5</samp> fails,
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PROGA is not called. The procedure then processes the next command, ENDPGM,
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which signals the end of the procedure, and returns control to the calling
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procedure.</p>
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<p>Processing logic would be different if, using the same code,
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the initial values of the variables were different. For instance, if at the
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beginning of this code the value of &A is 3 and the value of &C is
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4, the first IF statement is evaluated as false. Instead of processing the
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GOTO FINAL command, the procedure ignores the first IF statement and moves
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on to the next one. The second IF statement is evaluated as true, and the
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value of &C is changed to 5. Subsequent statements, not shown here, are
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also processed consecutively. When processing reaches the last IF statement,
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the condition <samp class="codeph">&C=5</samp> is evaluated as true, and PROGA is
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called.</p>
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<p>A series of consecutive IF statements are run independently.
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For instance:</p>
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<pre> PGM /* IFFY */
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DCL &A..
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DCL &B..
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DCL &C..
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DCL &D..
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DCL &AREA *CHAR LEN(5) VALUE(YESNO)
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DCL &RESP..
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IF (&A=&B) THEN(GOTO END) /* IF #1 */
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IF (&C=&D) THEN(CALL PGMA) /* IF #2 */
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IF (&RESP=1) THEN(CHGVAR &C 2) /* IF #3 */
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IF (%SUBSTRING(&AREA 1 3) *EQ YES) THEN(CALL PGMB) /* IF #4 */
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CHGVAR &B &C
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.
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.
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.
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END: ENDPGM</pre>
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<p>If, in this example, &A is not equal to &B, the next
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statement is run. If &C is equal to &D, PGMA is called. When PGMA
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returns, the third IF statement is considered, and so on. An embedded command
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is a command that is completely enclosed in the parameter of another command.</p>
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<p>In
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the following examples, the <span class="cmdname">Change Variable (CHGVAR)</span> command
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and the DO command are embedded:</p>
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<pre>IF (&A *EQ &B) THEN(CHGVAR &A (&A+1))
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IF (&B *EQ &C) THEN(DO)
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.
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.
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.
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ENDDO</pre>
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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="expr.htm" title="The logical operators *AND and *OR specify the relationship between operands in a logical expression. The logical operator *NOT is used to negate logical variables or constants.">*AND, *OR, and *NOT operators</a></div>
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<div><a href="docmd.htm" title="The DO command allows you to process a group of commands together.">DO command and DO groups</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>
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<div class="relinfo"><strong>Related information</strong><br />
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<div><a href="../clfinder/finder.htm">CL command finder</a></div>
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<div><a href="../cl/if.htm">If (IF) command</a></div>
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</div>
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</div>
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</body>
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</html>
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