Re: Benefits of Sub-procedures

["Andy Holmer" <aholmer@xxxxxxxxxx>]

Bob, 

> I'm looking for some ammo, guys!

One of many reasons I like sub-procedures is because I can pass
parameters by value.  Consider the following code for two programs 

Disclaimer: Please don't lynch me for posting RPGIII

PGM 1:
     H        1   M                                           
     INAMED       DS                                          
     I                                        1  10 FIELD1    
     I                                       11  20 FIELD2    
     I              'FIELD_NUM1'          C         CON1      
     I              'FIELD_NUM2'          C         CON2      
     C                     MOVE CON1      FIELD1              
     C                     MOVE CON2      FIELD2              
     C*                                                       
     C                     CALL 'PGM2'                        
     C                     PARM           FIELD1              
     C*                                                       
     C                     DSPLY          FIELD2              
     C                     SETON                     LR       
     C                     RETRN                              
PGM 2:
     H        1   M                                              
     C*                                                          
     C           *ENTRY    PLIST                                 
     C                     PARM           INPUT  15              
     C*                                                          
     C                     MOVE *BLANKS   INPUT                  
     C*                                                          
     C                     SETON                     LR          
     C                     RETRN                                 

Now the obvious problem is that the parameter lengths are mismatched
between the two programs.  I have shown this to seasoned "RPGIII 'til I
die" and they never guess that you can mess up a field that doesn't even
show up in your called program.  This isn't something I can take lightly
if I start updating files with incorrect data.  Considering the fact
that this can be avoided completely by passing by value, (or
prototyping) plus all the other benefits mentioned like local variables,
modularity, and so on, any program I write is now modular and
sub-routines are getting rarer.

HTH, Andy

BTW: Thanks to Jon Paris and COMMON for showing me the interesting set
of programs above.