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95 lines
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<meta name="DC.Title" content="Use defined variables" />
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<meta name="abstract" content="Defined variables make it easy to manage complex data structures in CL by eliminating the need to substring values out of a large variable." />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Use defined variables</title>
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</head>
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<body id="definedv"><a name="definedv"><!-- --></a>
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<img src="./delta.gif" alt="Start of change" /><!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Use defined variables</h1>
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<div><p>Defined variables make it easy to manage complex data structures
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in CL by eliminating the need to substring values out of a large variable. </p>
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<div class="section"><p>Defined variables can be used to map different parts of the defined
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on variable or the same part of a given variable in different ways.</p>
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<p>In
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the following example, the variables &LIBNAME will always be equal to
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the first 10 bytes of &OBJECT. Using the defined variable &LIBNAME
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will improves the readability of the code and makes it easier to work with.
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The variable &OBJECT provides the storage for the &LIBNAME and &OBJNAME
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variables.</p>
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<pre>PGM
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DCL &OBJECT *CHAR 20
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DCL &LIBNAME *CHAR 10 STG(*DEFINED) DEFVAR(&OBJECT)
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DCL &OBJNAME *CHAR 10 STG(*DEFINED) DEFVAR(&OBJECT 11)
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:
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IF COND(%SST(&OBJECT 11 10) *EQ &OBJNAME) +
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THEN(...))
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:
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ENDPGM</pre>
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<p>You can also make the same storage with multiple definitions.
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In this example, the variables &BINLEN and &CHARLEN both refer to
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the same 4 bytes of variable &STRUCT. The program can then use the definition
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that best suits its requirements.</p>
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<pre>PGM
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DCL &STRUCT *CHAR 50
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DCL &BINLEN *INT 4 STG(*DEFINED) DEFVAR(&STRUCT)
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DCL &CHARLEN *CHAR 4 STG(*DEFINED) DEFVAR(&STRUCT)
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:
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ENDPGM</pre>
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<p>This example shows how a defined variable can be used to change
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values in a variable. This example also makes use of the %OFFSET built-in
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function and a based variable to navigate the library list. This is not the
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optimal way to do message substation but illustrates some of the capabilities
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of defined variables.</p>
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<pre>PGM
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DCL &MESSAGE *CHAR 25 VALUE('LIBRARY NNN IS XXXXXXXXXX')
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DCL &SEQUENCE *CHAR 3 STG(*DEFINED) DEFVAR(&MESSAGE 9)
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DCL &MSGLIBN *CHAR 10 STG(*DEFINED) DEFVAR(&MESSAGE 16)
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DCL &COUNTER *INT 2
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DCL &LIBL *CHAR 165
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DCL &PTR *PTR ADDRESS(&LIBL)
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DCL &LIBLNAME *CHAR 10 STG(*BASED) BASPTR(&PTR)
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:
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RTVJOBA SYSLIBL(&LIBL)
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CHGVAR &COUNTER 0
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DOFOR &COUNTER FROM(1) TO(15)
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IF (&LIBLNAME *EQ ' ') THEN(LEAVE)
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CHGVAR &SEQUENCE &COUNTER
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CHGVAR &MSGLIBN &LIBLNAME
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SNDPGMMSG MSGID(CPF9898) MSGF(QSYS/QCPFMSG) MSGDTA(&MESSAGE)
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CHGVAR %OFS(&PTR) (%OFS(&PTR) + 11)
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ENDDO
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:
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ENDPGM</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="workv.htm" title="CL procedures consist of CL commands, and the commands themselves consist of the command statement, parameters, and parameter values.">Use variables</a></div>
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</div>
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</div>
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<img src="./deltaend.gif" alt="End of change" /></body>
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