Thu, May
1 New Articles

RPG Building Blocks: Maxima and Minima

  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

When the RPG IV development team designed built-in functions in the language, they omitted the functions that find the maximum and minimum among a group of values. This article presents these functions, plus two others I haven’t seen in any high-level language.

Often when comparing multiple numeric values, it’s useful to determine which value is the highest (maximum) and which is the lowest (minimum). Most programming languages offer a max() and a min() function precisely for this purpose, but RPG IV didn’t—until now. To demonstrate how useful these functions are, consider a typical sales analysis report: It determines which of the last 12 months provided the highest and lowest sales, information you need to know.

Functions such as max() and min() must be able to accept a variable number of parameters, since you may have to compare two numbers in one case, but 12 in another. Figure 1 shows the prototypes for four such functions: max(), maxid(), min(), and minid(). They have been defined with a maximum of 20 parameters, of which only the first and second are required. All others (third to 20th) bear OPTIONS(*NOPASS) to make them optional.

I have already described max() and min(). The other two functions don’t return the value of the maximum or minimum, but actually identify the value by its relative position within the parameter list. For instance, maxid() returns a 4 if the fourth parameter has the highest value. And minid() does the same for the minimum.

How They Work

All four functions have similar logic, so I’ll pick max() as an example of how the functions operate. Within subprocedure MAX (Figure 2), I define the procedure interface, which is a virtual duplicate of the prototype copied from MAXMIN@. I also declare a local variable maxval, which holds the maximum value found.

I initialize maxval to *LOVAL at the start of the C-specs. This makes maxval the potential minimum for all 20 parameters. Then, I compare it against nbr01, the first

parameter value. If nbr01 is greater than maxval, I update maxval accordingly. When this IF block ends, maxval will be either *LOVAL or equal to nbr01, whichever is greater.

Then, I repeat the process with the other 19 parameter values. When all 20 tests are performed, maxval will have the value of the maximum. Notice that, starting with the comparison against nbr03 (which is optional), the IFs ensure that the actual number of parameters received by max() includes the parameter in question. So, in the third IF block, I make sure that the function received is at least three parameters by comparing the built-in function %PARMS against 3. %PARMS always returns the number of parameters received by the current procedure.

How to Use It

Figure 3 shows a short RPG IV program that illustrates how to use the MAXMIN service program. All that remains after coding a /COPY directive to copy the prototypes is to use the functions.

Here, two of them are used: max() and minid(). In the first case, I determine that 30 is the highest of the numbers 10, 20, and 30; in the second case, the first parameter contains the lowest number.

Figure 3 illustrates something else. The receiving field, r, does not have to be defined to match the format of the function’s returned value. For example, the max() function returns the maximum value in a packed decimal field 30 digits long. Field r, however, has only seven digits but contains two decimal positions; yet the function works, and the receiving field is updated correctly.

One last item: All four functions accept only whole numbers as parameters. If you need to compare numbers that may have decimal positions, you’ll have to convert them to whole numbers first. Fortunately, you can do this with expressions already embedded within the function itself. For instance, if you want to find the minimum between field a and b (each having two decimal positions), you can code the min() function as follows:


You guarantee that both numbers are whole numbers because each is multiplied by



Support MC Press Online

$0.00 Raised:

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: