Pointers

[PeteAmsterdam]

I was reading an RPG 400 book. they talked about pointers in the RPG program. I have never seen any code using this.
How is it used?

 

[MdnghtPgmr]

PeteAmsterdam,

Here is ONE thing you can do with them. A lot of the API's (mostly the C function ones) use pointers.

 * Named indicators                                       
                                                          
D                 DS                  Based( IndicatorP ) 
D Exit                    3      3N                       
D Refresh                 5      5N                       
D F06                     6      6N                       
D Update                 10     10N                       
D Cancel                 12     12N                       
D RollDown               26     26N                       
D RollUp                 27     27N                       
D Error                  30     30N                       
D OpenError              76     76N                       
D DspMessage             80     80N                       
D SflDsp                 81     81N                       
D SflDspCtl              82     82N                       
D SflClr                 83     83N                       
D LastRecord             89     89N                       
D SubfileEOF             90     90N                       
D RcdNotFound            99     99N                       
                                                          
D IndicatorP      S               *   Inz( %Addr( *In ) )

HTH,
MdnghtPgmr

 

[MdnghtPgmr]

Forgot to post the example! Anyway setting up your indicators in this manner then lets you write code without using indicators. Some are for this and some are against it. I choose to like it! ;-)

   // Always display the message subfile              
                                                      
   DspMessage = *ON;                                  
                                                      
   // Mainline code                                   
                                                      
   DoW NOT Exit;                                      
       Request = 'DISPLAY';                           
       ExSr MsgRoutine;                               
       Write MSGCTL;                                  
       ExFmt EFD020A;                                 
       If NOT Exit;                                   
          Chain DBKEYS EFLACHDC03;                    
          If NOT( %FOUND( EFLACHDC03 ) );             
             IndAndMsg = '00' + 'XAI0001';            
             Request = 'SNDMSG';                      
             ExSr MsgRoutine;                         
          Else;                                       
             DoW NOT Exit And NOT Cancel;             
                 Request = 'DISPLAY';                 
                 ExSr MsgRoutine;                     
                 Write MSGCTL;                        
                 ExFmt EFD020B;                       
                 If Cancel;

 

[Mercury2]

Also check out

http://www.scottklement.com/rpg/pointers.html