137 lines
6.9 KiB
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137 lines
6.9 KiB
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<meta name="DC.Title" content="Embedded IF commands" />
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<meta name="abstract" content="An IF command can be embedded in another IF command." />
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<meta name="DC.Relation" scheme="URI" content="ifcmd.htm" />
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<title>Embedded IF commands</title>
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<body id="embif"><a name="embif"><!-- --></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">Embedded IF commands</h1>
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<div><p>An IF command can be embedded in another IF command. </p>
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<div class="section"><p>This would occur when the command to be processed under a true
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evaluation (the CL command placed on the THEN parameter) is itself another
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IF command:</p>
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<pre>IF (&A=&B) THEN(IF (&C=&D) THEN(GOTO END))
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GOTO START</pre>
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<p>This can be useful when several conditions must be satisfied
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before a certain command or group of commands is run. In the preceding example,
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if the first expression is true, the system then reads the first THEN parameter;
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within that, if the <samp class="codeph">&C=&D</samp> expression is evaluated
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as true, the system processes the command in the second THEN parameter, GOTO
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END. Both expressions must be true to process the GOTO END command. If one
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or the other is false, the GOTO START command is run. Note the use of parentheses
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to organize expressions and commands.</p>
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<p>Up to 25 levels of such embedding
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are permitted in CL programming.</p>
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<p>As the levels of embedding increase
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and logic grows more complex, you may wish to enter the code in free-form
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design to clarify relationships: </p>
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<pre>PGM
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DCL &A *DEC 1
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DCL &B *CHAR 2
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DCL &RESP *DEC 1
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IF (&RESP=1) +
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IF (&A=5) +
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IF (&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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CALL PGM(DAILY)
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ENDPGM</pre>
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<p>The preceding IF series is handled as one embedded command.
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Whenever any one of the IF conditions fails, processing branches to the remainder
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of the code (<span class="cmdname">Change Variable (CHGVAR)</span> and subsequent commands).
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If the purpose of this code is to accumulate a series of conditions, all
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of which must be true for the Do group to process, it could be more easily
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coded using *AND with several expressions in one command.</p>
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<p>In
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some cases, however, the branch must be different depending on which condition
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fails. You can accomplish this by adding an ELSE command for each embedded
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IF command: </p>
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<pre>PGM
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DCL &A ...
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DCL &B ...
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DCL &RESP ...
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IF (&RESP=1) +
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IF (&A=5) +
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IF (&B=NO) THEN(DO)
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.
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.
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.
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SNDPGMMSG ...
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.
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.
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.
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ENDDO
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ELSE CALLPRC PROCA
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ELSE CALLPRC PROCB
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CHGVAR &A 8
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CALLPRC PROC(DAILY)
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ENDPGM</pre>
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<p>Here, if all conditions are true, the <span class="cmdname">Send Program
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Message (SNDPGMMSG)</span> command is processed, followed by the <span class="cmdname">Change
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Variable (CHGVAR)</span> command. If the first and second conditions (<samp class="codeph">&RESP=1</samp> and <samp class="codeph">&A=5</samp>)
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are true, but the third (<samp class="codeph">&B=NO</samp>) is false, PROCA is called;
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when PROCA returns, the CHGVAR command is processed. If the second conditions
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fails, PROCB is called (<samp class="codeph">&B=NO</samp> is not tested), followed
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by the CHGVAR command. Finally, if &RESP does not equal 1, the CHGVAR
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command is immediately processed. The ELSE command has been used to provide
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a different branch for each test.</p>
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<div class="note"><span class="notetitle">Note:</span> The following three examples are
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correct syntactical equivalents to the embedded IF command in the preceding
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example:</div>
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<pre>IF (&RESP=1) THEN(IF (&A=5) THEN(IF (&B=NO) THEN(DO)))
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IF (&RESP=1) THEN +
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(IF (&A=5) THEN +
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(IF (&B=NO) THEN(DO)))
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IF (&RESP=1) +
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(IF (&A=5) +
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(IF (&B=NO) THEN(DO)))</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="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="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>
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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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