Tip

Don't proliferate old, bad code

In an effort to hasten the completion of projects, most programmers "steal" code from other sources within their libraries. The problem is that many times, the code originated years ago and is cumbersome, lengthy, and not easy to maintain. Even most ILE code resulted from old code that was passed through a conversion utility. Using the functionality of RPGIV's Keywords and Built-In-Functions usually can make the code much smaller and manageable. Here are just a couple of examples that I've come upon recently.


Example 1:
A file contains many fields used as buckets, such as monthly totals, and each field needs to be interrogated.

OLD WAY:
Define a Data Structure with each file field as a subfield and define an array and move data structure to array.

 FINPUTFIL  IF   E           K DISK
D ARY             S             10    DIM(4)
D FILDS           DS            40 
D  FLD01                  1     10 
D  FLD02                 11     20 
D  FLD03                 21     30 
D  FLD04                 31     40
C     FILKEY        CHAIN     INPUTFIL 

.... Move each Field to array and do processing
or
Do a rename of each field.

 
IINPFIL                                
I              FLD01                       ARY(1)
I              FLD02                       ARY(2)
I              FLD03                       ARY(3)
I              FLD04                       ARY(4)

NEW WAY:
Define External Data Structure and Overlay Array on Data Structure

 
FINPUTFIL  IF   E           K DISK
D FILDS         E DS            40    EXTNAME(INPUTFIL)
D  ARY                    1     40    DIM(4)
C     FILKEY        CHAIN     INPUTFIL
.... Now ARY(1) = FLD01, etc. automatically 

Example 2:
Date Validation.

OLD WAY:
Use Data Structures and moves to check each field. This example was passed on to many different programs.

 
I            DS                                      
I                                        1   60DSPDAT 
I                                        1   20$@M   
I                                        3   40$@D   
I                                        5   60$@Y   
C           $@D       CABLT1         $TG001       11 
C           $@M       CABGT12        $TG001     11   
C           $@M       CABLT1         $TG001       11 
C           $@Y       DIV  4         $@REM   10      
C                     MVR            $@REM           
C                     Z-ADD$@M       $@MS    20      
C           $@REM     IFEQ 0                         
C           $@M       IFEQ 2                         
C                     Z-ADD13        $@MS         
C                     END                         
C                     END                         
C           $@D       CABGT$@E,$@MS  $TG001     11 

NEW WAY:
Use ILE Date operations and edits.

 
D Today           S               D   Inz(*SYS)
D WrkDate         S               D
D Days            S              4  0
C     *MDY          Test(DE)                DSPDAT
C                   If        %Error    
C                   Eval      *In81 = *On
C                   Endif                            
C     *MDY          Move      DSPDAT        WrkDate
C     WrkDate   SubDur     Today         Days:*D
C                   If        Days < *Zero
C                   Eval      *In81 = *On            
C                   Endif 

Example 3:
Building text strings.

OLD WAY:
The most common examples include using arrays with loops that test for each character or builds an array of characters and moves the array to a text field.

NEW WAY:
Using BIFs like %Editc, %Subst, %Scan, %Trim, %Xlate will allow complex text strings to be validated and built with as little as one eval statement through concatenation.

 
DExcCmd           PR                  ExtPgm('QCMDEXC')
D Command                      320    Const            
D Length                        15  5 Const            
C                   Eval      Clock# = %Subst(User:3:5)                   
C                   Eval      #UsrDta = %Subst(Pm1CLASS:1:2) + '-' +      
C                              %Trim(%Editc(JobTckt#:'Z'))                
C                   Eval      #SplNm = %Subst(DayOfWeek:1:3) +            
C                              PullHouse                                  
C                   Eval      Command = 'OVRPRTF BCLABELS OUTQ(' + Outq + 
C                              ') HOLD(*YES) SAVE(*NO) SPLFNAME(' +       
C                              #SplNm + ') USRDTA(''' + #UsrDta + ''')'   
C                   Eval      WrkClass = Pm1CLASS                         
C                   Callp     ExcCmd(Command:Length) 

Moral of the story: Use the full capabilities of RPGIV with Keywords and Bifs, especially when taking old code and re-using it.

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This was first published in March 2002

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