Converting to Freeform RPG
Sunday, May 31st, 2009I didn’t think I’d be considering free-format RPG so soon as a final solution for the current RPG programs on the system at work (some of which date back to the 70’s), but a number of interesting events have taken place.
Our IBM representative made us aware of a software package that accomplishes the conversion of RPGII, RPGIII, and RPG400 programs into true RPGIV. This means (among other things) ditching the left-hand indicators and attempting to really use more modern operation codes. If you are at all familiar with what would be necessary, you can appreciate how difficult this task would be without some kind of automation. The painstaking code changes and testing would be incredible on a code base of any size.
This package is called RPG Toolbox, from Linoma Software.
So we downloaded the trial version, which allows 10 source conversions from another RPG dialect - or even RPGIV that has simply been converted from an older format using IBM’s CVTRPGSRC utility. CVTRPGSRC simply reformats old code into RPGIV syntax; it does not attempt to modernize it. We converted a source member with a lot of left-hand indicators, and we were impressed how it converted into a reasonably neat format without those indicators. What really impressed me was that it would attempt to convert a series of MOVE statements, which was commonly the method used to piece together larger fields, into EVAL statements. This could be a dangerous technique, but the RPG Toolbox utility carefully analyzes the code to make sure it is safe. In the manual, it describes how it makes decisions about code conversion; if one is interested in this product, that person would do well to download and read the manual before making decisions about what the program should do in the course of conversion.
I also had an inspiration- why not use it to convert RPG IV to freeform? In earlier posts, I have declared my reservations about how valuable freeform is. But, if it’s easy, why not live dangerously? So I tried converting one of the RPGIV programs in my file cross-reference system to freeform. The results were impressive. It looked VERY good. The more I looked at it, the more I liked it. So I said to myself, why not convert ALL our code to freeform?
But then my younger cohort brought me back down to earth. He wasn’t so sure that would be a good idea. So we converted the old-format code referred to above into freeform. The results were messy. There was much code that simply could not be converted, often involving the MOVE and MOVEL opcodes. (I have also commented on this previously.) When this happens, the free-format code is enclosed in a /FREE - /END-FREE set of compiler directives and the code drops back into fixed format. Switching back and forth between free and fixed can be maddeningly ugly.
So I have backed off the idea of a total conversion to freeform RPG. But we still feel that converting our code to a clean RPGIV that uses as much as possible of RPGIV’s modern syntax and opcodes would certainly be a good thing; and it appears that it would be relatively safe. We have ordered the software. Where the conversion of a program to freeform would not create too messy a result, we can still convert it.
I was also surprised to learn how quickly the most experienced one on our crew would take to freeform. He first started programming in ALGOL; so freeform is not really that much of a leap for him. He has in the past several weeks written new programs in freeform RPG, of his own free will. My other partner has a Pascal/Java background; so freeform would come “naturally” to him. I am the one who will take some getting used to the idea.