RE: Web apps on the AS/400 -- MIDRANGE-L

Leif, I'm going to have to disagree with you here.  Classes and subroutines
are completely different programming entities.  Subroutine take parameters
passed to them and do things to those parameters.  Classes, on the other
hand, have an internal state that they act on in response to messages, and
that they will communicate to the outside world.  The two concepts - classes
and subroutines - can often be used to solve the same programming problems,
but they are very, very different beasts.

Now, when your subroutine is part of a service program that has an internal
state (like many operating system calls), then yes, it's closer to a class.
Or even in RPG III, if you just don't set on LR, and call the program
repeatedly getting different results based on the programs current internal
state, then it's closer to the class concept.  But the other things that
make classes so powerful, such as multiple entry points (polymorphism) and
more importantly being able to change the behavior of an object through
subclassing, are too powerful to be ignored and thought of as just the "1%"
difference between OO and procedural code.

We just had a fairly long and enjoyable conversation on JAVA400-L between
Brad Stone and I on how true OO design makes a simple program incredibly
powerful.  In this case, we showed how, by changing his design in some ways
that are counter-intuitive to most procedural programmers, he would be able
to add the capability for his program to return either XML or HTML by
changing just one line of code.  More importantly, he'd be able to add a
whole new style, say WML or VML, without having to change his program at
all - just add a new class.

This CAN be done procedurally, using subroutines, but it's almost
impossible, and it requires reinventing wheels (for example, a dispatcher)
that are already present in Java.

Alien, perhaps, but if you can come to terms with BIFs and APIs and
activation groups, you can manage classes and objects.  I did, and I'm a 20+
year RPG dinosaur.


> Joe, part of what scares people is simply the alien words.
> "Classes", "instantiation", etc. The "class" is  99% the same
> as the good ol'e external subroutine. The 1% being the fancy
> stuff most application programmers don't need to know and
> (sadly) don't want to know. Everyone is familiar with the concept
> of a good in-house subroutine library. And don't call them "business
> objects", either.

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