Comparing RPG code to C# : The For Loop

There are similarities between free format RPGIV and C#. In the example below I show a small program that accomplishes the same task in both languages. The task is to find the first blank character in a string from the end to the beginning. I'm well aware there is a single method available for this on String in C# but the purpose here is to show the similarities.
RPG is below:


















Now C#:

You can see some basic similarities:

• Statements end with a ';' ,


• the For loop is similar.


• 'Leave' gets you out of an RPG loop while 'Break' exits a C# loop.


• Assigning values is the same in both.


• Declaring variables in RPGIV requires both type and how many characters (you can declare varying length variables but do define an initial length). To define a variable you must put values in fixed positions in a special kind of statement block called 'Definition Specifications' or D-specs. In C# you simply declare the type. The type of the index 'i' is denoted by a zero in the decimal placess position.


• C# requires a 'Main' method. RPG just executes from the first executable line.


• C# variables are local by default. I can't access that 'i' variable outside of that For loop - the program wouldn't even compile. RPG variables are global unless used in procedures.



• C# requires a class definition, namespace and you define what other namespaces in .Net you want to refer to in your program with the 'Using' statements. The using just means you don't have to refer to the full name like 'System.Console.Readline()'.



• C# doesn't need 'EndFor' or 'EndIf'. Coding is accomplished in blocks between curly braces '{' and '}'.



• The biggest difference is that C# strings and objects have a multitude of methods and properties on the string itself - not part of the language. RPGIV is pretty good at string manipulation too but can never approach the flexibility of C# as the RPG designers would have to create a new keyword when it needs to perform a function on a string that it doesn't already have. In C# there are only a handful of keywords - most actions are accmplished by methods on the objects themselves. For instance in the above example you access the length of a string by examining its property. e.g. 'field.length' returns an integer value whereas in RPG I chose to use the built-in-function %len to do the same thing.
  To find the first non-blank in a string starting from the end you can use field.IndexofLast(' ') . RPGers note how the methods and properties are on the string 'field' which I defined. As soon as you define a variable it creates a copy of the string object so you have full access to a huge amount of manipulation techniques. Adding new methods and properties to strings and other types isn't a major change in the language.

RPG Output below

C# Output:

C# for iSeries RPG programmers

There are many iSeries RPG programmers out there who are keen to get started on another programming language that matches the flexibility and scope of RPG with the added web, windows and forms simplicity available in modern IDE's.
Which language will you invest your valuable time in? Java, PHP, Visual Basic, Delphi, Ruby, C#?


Java is a good, mature candidate since it also runs on the iSeries. Ruby is open and emerging as easy to learn, productive and object oriented. Delphi (Object Pascal) has been around for donkey's. PHP is mainly used for scripting and web pages so only server partial needs. Visual Basic and C# are just variations of Microsoft's powerful .NET platform but C# programmers get paid more. For someone still on the iSeries you will want a language that has excellent connectivity to the black box. That leaves Java and C#. C# has Linq! and is far easier than Java at creating windows desktop applications but Java does run on the iSeries. So it's a toss up but my friends, Linq pushes the argument to C#.

Let's look at C#.
C# (like Java) can be hard to read, is full of abstruse concepts such as polymorphism, inheritance and encapsulation. Five lines of RPG could be one line in c# and one line in RPG could be five in c#.
It's Geeky. At first glance code will appear to operate your vacum cleaner but will just read a file and print its contents. It gives you lots of ways to accomplish the same thing. Lots.
It's not simple. It's not easy. It's a pain in the ass.
It's a great language.

I recommend that RPG developers dive in to c# despite the challenges. The best way to deal with challenges is, of course, to ignore them. Yes, run away. Start writing code c# just as you would in RPG. In other words I am advocating to begin your next language which is built specifically for object oriented (OO) development to start using it as a functional procedural language. Write short little programs to display iSeries data in grids for the web, for windows, for handhelds. Think of c# as RPG for the desktop.
You may well be persecuted by OO idealogues who are (bitterly) passionate about the 'right ' way to code. They like 'coding'. RPG programmers like 'going home at 5'. They really couldn't give a shite. RPG developers are for the most part business oriented types who create software to solve real life business situations.

As time passes you'll find that you'll write more complicated code and will need to start using object oriented principles.Keep your eyes on this blog for step by step instructions for writing c# programs for use against the iSeries data and legacy applications and together we will work up to object oriented development beginning with procedural C# - let's call it RPG#.