An RPG programmer wants to substitute the values of variables ITEM and PRICE into the string template "The price of item %ITEM% is $%PRICE%.".

The programmer can use DATA-GEN to handle this.

The program using the DATA-GEN opcode

**free
// price_msg - a data structure for the MULTRPL generator for DATA-GEN
// - the first subfield is the message template
// - the second subfield is the character that surrounds the replacement names
// - the remaining subfields are the replacement subfields
dcl-ds price_msg qualified;
   message varchar(100) inz('The price of item "%ITEM%" is $%PRICE%.');
   marker char(1) inz('%');
   item varchar(20) inz('Table');
   price packed(5:2) inz(123.45);
end-ds price_msg;
     
// A variable to receive the formatted message
dcl-s output char(50);

// This DATA-GEN will substitute ITEM and PRICE
data-gen ds %data(output) %gen('MULTRPL');
     
// Display the result: The price of item "Table" is $123.45.
dsply output;
return;

The DATA-GEN generator program MULTRPL

**free
// A generator for the DATA-GEN opcode to substitute
// several values into a string
//
// Usage:
// 1. Define a data structure where
// - the first subfield is the string "template"
// message inz('The price of item "%ITEM%" is $%PRICE%')
// - the second subfield is the character placed before
// and after the replacement values
// marker inz('%')
// - the remaining subfields are the replacement values
// - they can have any data type
// item varchar(20) inz('Table');
// price packed(7:2) inz(123.45);
// 2. Specify the data structure as the first operand of DATA-GEN
// 3. Specify this program for %GEN

/if defined(*crtbndrpg)
   ctl-opt dftactgrp(*no);
/endif
ctl-opt option(*srcstmt);
ctl-opt debug(*constants);
ctl-opt ccsid(*ucs2 : *utf16);
ctl-opt main(multipleReplacements);

/copy qoar/qrpglesrc,qrndtagen

dcl-proc multipleReplacements;
   dcl-pi *n;
      parm likeds(QrnDgParm_T);
   end-pi;
   dcl-s subf varchar(100);
   dcl-s i int(10);
   dcl-s value ucs2(1000) based(pValue);
   dcl-s subfValue varucs2(1000);
   dcl-s replaceName varucs2(1000);

   dcl-ds state qualified based(pState);
      result varucs2(10000);
      marker varucs2(10);
   end-ds;

   pQrnDgEnv = parm.env;
   if parm.event = QrnDgEvent_03_Start;
      // Start of generation: Allocate the
      // "state" info
      parm.generatorState = %alloc(%size(state));
   endif;
   pState = parm.generatorState;

   if parm.event = QrnDgEvent_04_End;
      // End of generation: Report the resulting string
      QrnDgAddText (parm.handle 
                  : %addr(state.result : *data)
                  : %len(state.result));
       // Free the state info
       dealloc(n) parm.generatorState;
   elseif parm.event = QrnDgEvent_11_ScalarValue;
      if parm.scalar.subfieldNumber = 1;
         // The first subfield has the template string
         pValue = parm.scalar.value;
         state.result =
            %subst(value : 1 : parm.scalar.valueLenChars);
      elseif parm.scalar.subfieldNumber = 2;
         // The second subfield has the substitution marker
         // - it is placed before and after each substitution
         // value in the template string
         pValue = parm.scalar.value;
         state.marker =
            %subst(value : 1 : parm.scalar.valueLenChars);
      else;
         // The result of the subfields have the replacement
         // values
         pValue = parm.scalar.value;
         subfValue = %subst(value : 1 : parm.scalar.valueLenChars);
         replaceName = state.marker + %upper(parm.name) + state.marker;
         state.result = %scanrpl(replaceName
                               : subfValue
                               : state.result);
      endif;
   endif;
   return;
end-proc;