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A Handy RPG FUNction
by Ted Holt
I like functions. I like the ones built into RPG, like %SUBST and %DATE and %CHAR and %FOUND. I like the ones built into SQL, like UPPER and DIGITS. Functions accomplish a lot of work with little effort because the code inside a function does not need to be included in the routines that call the function. I enjoy writing my own functions and using them in my programming. Today, I'm going to share a function I recently wrote that is proving to be useful to me. You may like it, too.
Not long ago, I was working on an RPG program and needed to display a Y or N to indicate whether certain fields were true or not. I had a lot of five-line tests like this:
if Type = 'E';
EDICust = 'Y';
else;
EDICust = 'N';
endif;
Something about this looked familiar, and I finally realized what it was. I thought back to my System/34 and System/36 RPG II days, when I would look at RPG III code in the trade magazines and see things like this:
C TYPE IFEQ 'E'
C MOVE '1' *IN25
C ELSE
C MOVE '0' *IN25
C END
This type of code looked strange to me at the time, since I was used to accomplishing the same task with one COMP operation.
C* HILOEQ
C TYPE COMP 'E' 25
Anyway, back to the present. I had the nagging thought that I should be able to replace the five-line IF-ELSE-ENDIF structure with one line, even in free-format RPG IV. Finally it dawned on me that I had used such a technique in Microsoft Access and Visual Basic. In a few minutes, I had my own IIF function.
IIF is a very simple function. It accepts three arguments: a condition, a value to return if the condition is true, and a value to return if the condition is false. Here is the prototype:
D iif pr 256a varying
D Condition n value
D TrueValue 256a varying value
D FalseValue 256a varying value
And here is the function itself:
P iif b
D pi 256a varying
D Condition n value
D TrueValue 256a varying value
D FalseValue 256a varying value
/free
if Condition;
return TrueValue;
else;
return FalseValue;
endif;
/end-free
P e
Using IIF, I was able to reduce the many five-line tests to one line each. Here's the first example again:
if Type = 'E';
EDICust = 'Y';
else;
EDICust = 'N';
endif;
Here's the same code, using the IIF function.
EDICust = iif (Type = 'E': 'Y': 'N');
Notice that my IIF function works with character data only. It would be nice to have another IIF function for numeric values, but I haven't needed one yet. If I decide to write a numeric IIF, I will have to give it another name, since IBM doesn't allow different functions of the same name in RPG. (At least, not yet. I hope we'll see function overloading in a future release.)
There is no need for an IIF function to set indicator variables. Setting indicator variables with one operation is easily handled with the present RPG syntax. For example, this:
C TYPE IFEQ 'E'
C MOVE '1' *IN25
C ELSE
C MOVE '0' *IN25
C END
is easily replaced by this:
*in25 = (type = 'E')
If type has a value of E, indicator 25 turns on. If not, indicator 25 turns off. You can do the same thing in CL, by the way.
dcl &in25 type(*lgl)
chgvar var(&in25) value(&TYPE *EQ 'E')
Here is a short program interested professionals can compile and play with. Each test is done twice; the long way comes first, followed by the IIF version.
H option(*srcstmt: *nodebugio)
H dftactgrp(*no) actgrp(*new)
D iif pr 256a varying
D Condition n value
D TrueValue 256a varying value
D FalseValue 256a varying value
D DropShipCode s 1a
D ShipMsg s 3a
D Option s 1a
D Balance s 7p 2
D Age s 3p 0
D AgeCategory s 12a
/free
// 1. If DropShipCode = 'X', print Yes, else print blanks.
if DropShipCode = 'X';
ShipMsg = 'Yes';
else;
ShipMsg = *blanks;
endif;
ShipMsg = iif (DropShipCode = 'X': 'Yes': *blanks);
// 2. If Option is blank, assume Option = 'A'
if Option = *blank;
Option = 'A';
endif;
Option = iif (Option = *blank: 'A': Option);
// 3. Place into categories by age.
if Age < 6;
AgeCategory = 'Preschool';
elseif Age < 18;
AgeCategory = 'School age';
else;
AgeCategory = 'Graduate';
endif;
AgeCategory = iif(Age<6: 'Preschool':
iif(Age<18:'School Age': 'Graduate'));
// 4. If Balance <= *zero, turn on indicator 25.
if Balance <= *zero;
*in25 = *on;
else;
*in25 = *off;
endif;
*in25 = (Balance <= *zero);
*inlr = *on;
/end-free
* ====================================================
P iif b
D pi 256a varying
D Condition n value
D TrueValue 256a varying value
D FalseValue 256a varying value
/free
if Condition;
return TrueValue;
else;
return FalseValue;
endif;
/end-free
P e
I continually look for ideas for new functions to help me in my work. I hope you like IIF, and if you are not writing your own functions, I hope you will learn to do so soon. If you have a useful function you'd like to share with readers of Four Hundred Guru, please email it to me.
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