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Flexible are Your Calculations? | IBM i | IBM Systems Magazine http://www.ibmsystemsmag.com/ibmi/enewsletterexclusive/1706

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Developer> RPG

How Flexible are Your Calculations?RPG programming techniques to help you solve unsolvable problems.

September 2007 | by Jon Parisand Susan Gantner

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In this EXTRA article, we want to introduce some RPG programming techniques and hopefully make you think about ways to combine them to solve

unsolvable problems. One such case is how to provide user-controlled, spreadsheet-style calculations within an RPG program.

Weve addressed this problem several times in the past, but on this occasion the trigger was a request during a customer training class for a simpler

approach to pricing calculations. The customers existing solution was inflexible and required significant effort to introduce new pricing schemes. The

end users (bless their little cotton socks) simply wanted to enter the names of the variables and the required calculation steps entered into a database.

The program would then retrieve these details, apply them to a set of data and report the results. The calculation steps were very similar to how we

used to perform math in RPG/400 (e.g., add two variables, store the result in a temporary field, then multiply the temporary by a third field and so

on). Had it been an option to write the new program in PHP, for example, this requirement wouldnt have presented much of a problem such tasks

are simpler to handle in an interpreted language. But, naturally, the required solution needed to be integrated into an RPG application!

While a comprehensive solution to problems like this isnt really practical, RPG provides the basic tools to handle the requirement providing the

problem space is constrained. We'll discuss what we mean by that later. The problem has two basic elements. First, we need to be able to select the

actual calculation performed (add, subtract, etc.) based on the database entry. Second, we need to perform the selected calculation on fields whose

names were also supplied in the database entry.

Let's look at the calculation aspect first. Suppose you wanted to accommodate the basic add, subtract, divide and multiply operations. You might be

tempted to do something like this:

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Jon Paris is a technical editor with IBM Systems Magazine and co-owner of Partner400.

More Articles From Jon Paris

Susan Gantner is a technical editor with IBM Systems Magazine and co-owner of Partner400.

More Articles From Susan Gantner


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Related Articles

Even More Flexible Calculations

E-Newsletter Exclusive | In the September EXTRA e-Newsletter, Jon Paris and Susan Gantner shared some solutions to &qout;unsolvable&qout;

RPG problems with a technique for flexible calculations. Now they delve deeper with a more complex example, making a sequence of calculations

not only possible but simple to create and use.

RPG - Anchoring Your Team

Cover Story | Alternate approaches to extending your RPG applications.

The State of Modernization

Cover Story | Bruce Vining talks modernization with Jon Paris and Susan Gantner

RPG for the Web

iSeries EXTRA: By Now, the Case for RPG IV Should Be a No-Brainer

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