Upgrade old RPG ‘DO’ loops to sexy new RPGLE ‘FOR’ loops

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January 7, 2016

Upgrade old RPG ‘DO’ loops to sexy new RPGLE ‘FOR’ loops

By NickLitten

January 7, 2016

DO, FOR, ILE, LOOP, modernize, RPG, RPG400, RPGLE, upgrade

Upgrade old RPG source code — aka refactoring — is a fun past time

There are frequent little code snippets that I refactor over and over again. Some look similar but some look very different in modern language style. It’s perhaps worth documenting them in case someone else is trying to figure out alternative ways of refactoring old-style RPG3 or RPG400 code.

I frequently upgrade old RPG programs and ‘DO’ loops always get converted to RPGLE ‘FOR’ loops.

I just refactored an old RPG program that had a tasty little DO loop that looked like this:


C START     DO   END          COUNT
... do lots of logic and stuff
Upgrade old rpg

This can be refactor to look like this:

RPG4 – also known as RPGLE /FreeFormat

For Count = Start to End;
... do lots of logic and stuff

I prefer the syntax and layout of FOR loops – just more readable in my brain.

Plus we have some other nice and very readable techniques to control the count up and down. Lets say we wanted to count from 1 to 200 in steps of 5

for Count = 1 by 5 to 200;

or we can do that in reverse

for Count = 200 by 5 downto 1;
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