How to use ‘Conditional Selection in RPGLE and CLLE’

Way back in 2008, I wrote this blog about how to do various condition selection in RPG. So, I suppose it time to modernize those code examples in modern RPGLE Free, tidy it up, and add the same code examples in CLLE.

In RPGLE (and in CLLE sorta kinda) we have the following conditional opcodes available:

• The If-EndIf block
• The If – Else- EndIf block
• The If – ElseIf – Elseif – EndIf block
• The Select Block

Let’s look at them one by one.

The If-EndIf Programming Condition

If we want some code Statement(s) to be executed conditionally. We put these statements inside an If-EndIf block:

Simple *IF* in RPGLE

 dcl-s VARIABLE char(1) Inz('A');
 
 If VARIABLE = 'A';
    Dsply VARIABLE;
 EndIf;

 Return;

Simple *IF* in CLLE

 DCL VAR(&VARIABLE) TYPE(CHAR) LEN(1) VALUE('A')

 IF COND(&VARIABLE *EQ 'A') THEN(DO)
    SNDPGMMSG  MSG(&VARIABLE) 
 ENDDO

 RETURN

The output of the above program is as expected ‘A’

The *If-Else-EndIf* Programming Condition

If we want some RPGLE Statement(s) to be executed conditionally and a different set of statements if the condition fails, we use If-Else-EndIf blocks.

Let’s look at the same logic with a little more complexity added.

Simple If-Else-End in RPGLE

 dcl-s VARIABLE char(1) inz('A');
 dcl-s PASSTEST char(20) Inz('variable is A') ;
 dcl-s FAILTEST char(20) Inz('variable not A');

 If VARIABLE = 'A';
   Dsply PASSTEST;
 Else;
   Dsply FAILTEST;
 EndIf;

 Return;    

Simple *IF* in CLLE

PGM
 DCL VAR(&VARIABLE) TYPE(CHAR) LEN(1) VALUE('A')

 IF COND(&VARIABLE *EQ 'A') THEN(DO)
    SNDPGMMSG  MSG(&VARIABLE) 
 ENDDO
 ELSE CMD(DO)
    SNDPGMMSG  MSG(&FAILTEST)
 ENDDO           

 RETURN
ENDPGM

Note the difference in CLLE is that each IF group has a corresponding ENDDO statement then the next ELSE group follows.

Alternative *IF* in CLLE

We could also do this with single statements like this:

PGM
 DCL VAR(&VARIABLE) TYPE(CHAR) LEN(1) VALUE('A')

 IF COND(&VARIABLE *EQ 'A') THEN(SNDPGMMSG  MSG(&VARIABLE))
     
 ENDDO
 ELSE CMD(DO)
    SNDPGMMSG  MSG(&FAILTEST)
 ENDDO           

 RETURN
ENDPGM

The If-ElseIf-Else-EndIf Programming Condition

(this is the same as the SELECT condition which we will look at in the next section)

If we have multiple sets of condition-statements then we can go for If-ElseIf-Else-EndIf statements.

The different conditions are specified as factor 2 of If and ElseIf opcodes. The Else in this condition-rule is optional.

Actually, I think the If-ElseIf-Else-EndIf is the only conditional block in RPGLE where Only the first opcode ‘If’ and its ending opcode ‘EndIf’ are mandatory!

Simple *If-ElseIf-Else-EndIf* Example in RPGLE

Let’s make this a bit more interesting by adding an input parameter (‘p_input’) and checking for various conditions

 dcl-pi *n;
   p_input char(1);
 end-pi;

 If  p_input = 'A';
   Dsply 'Input value was A';
 elseif  p_input = 'B';
   Dsply 'Input value was B';
 elseif  p_input = 'C';
   Dsply 'Input value was C';
 Else;
   Dsply 'Input value was not A, B or C';
 EndIf;

 Return; 

The final ELSE is equivalent to saying “if all the IFELSE statements fail then do this”.

If I compile and run this from the command line it look like this:

Simple *If-ElseIf-Else-EndIf* Example in CLLE

I would like to do the same thing in CLLE but there is no ELSEIF command in CLLE (not right now anyway)

But we can easily do the ELSEIF logic by using a SELECT statement:

*SELECT* in CLLE

PGM PARM(&P_INPUT)
 DCL VAR(&P_INPUT) TYPE(*CHAR) LEN(1)

 SELECT                                                
 WHEN COND(&P_INPUT *EQ 'A') THEN(DO)            
        SNDPGMMSG  MSG('Input value was A')                
      ENDDO
 WHEN COND(&P_INPUT *EQ 'B') THEN(DO)
        SNDPGMMSG  MSG('Input value was B')                
      ENDDO
 WHEN COND(&P_INPUT *EQ 'C') THEN(DO)
        SNDPGMMSG  MSG('Input value was C')                
      ENDDO
 OTHERWISE CMD(DO)                                    
        SNDPGMMSG  MSG('Input value was not A, B or C')
 ENDDO
 ENDSELECT
                                                 
 RETURN
 ENDPGM

The OTHERWISE is equivalent to saying “if all else fails do this”.

Pretty obvious stuff once you know the syntax right?

Executing this little bit of code looks like this:

*SELECT* in RPGLE

Now the exact same thing in RPGLE is marginally different but still essentially the same:

 dcl-pi *n;                               
   p_input char(1);                       
 end-pi; 
                                 
 select;                                  
 when p_input = 'A';                      
   Dsply 'Input value was A';             
 when  p_input = 'B';                     
   Dsply 'Input value was B';             
 when  p_input = 'C';                     
   Dsply 'Input value was C';             
 other;                                   
   Dsply 'Input value was not A, B or C'; 
 EndSl; 
                                  
 Return;                                  

And there you have it. 🙂