Re: RPG,COBOL or JAVA

["David Morris" <dmorris@xxxxxxxxxxxxx>]

Hans,

I do agree that RPGIV is lacks many basic features of 
an object oriented language.  Primarily the interfaces 
provided do not allow very much flexibility.  You cannot 
pass variable type parameters, and because of parameter 
passing restrictions, you cannot simulate inheritance 
directly.  In order to support these things you have to 
define your own storage system.  RPGIV will do little to 
help you understand OO, but I think it is a better 
starting point than RPGIII.

I am interested to find out how your experience with OO 
programming progresses.  We had problems when we 
assumed that inheritance should be used wherever 
possible.  We ended up backing off quite a bit.  I 
suspect this has happened to others.

I am no expert in Java and I am sure most of our problems 
with OO have been caused by a lack of experience.   I 
have been working on a system that uses  inheritance 
extensively, and there were drawbacks.  One problem 
is that inheritance is defined at compile time.  Another 
problem, and the one caused the most problems for us 
was that changes to a parent can affect subclasses.  
A system built of components is generally more flexible, 
the trade-off is that you do not get the same level of 
re-use.

David Morris

>>> <boldt@ca.ibm.com> 12/08 7:50 AM >>>


Buck Calabro wrote:
>I think that this is very well said.  An aside is
>that RPG IV/ILE RPG can help you learn OO while
>you work, rather than have to learn OO AND a new
>language AND a new environment (GUI) all at the
>same time.

I have to disagree with this.  New features of
RPG IV, such as prototyped procedures, allow you
to apply the technique of "modular programming",
which became popular in the early 80's.  Object
oriented programming goes well beyond modular
programming.  Being well-versed in modular
programming offers little advantage when faced
with fundamental OO concepts such as inheritance.
...
To summarize my point:  Inheritance is a very
fundamental characteristic of OO programming and
cannot be fully appreciated without experiencing
OO.  Using a non-OO language, like RPG IV, can
never prepare you for OO.

Cheers!  Hans

Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com 


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