Re: Can RPGLE simulate OO programming? -- RPG400-L

> Ahhh...  so what you're suggesting (if I follow you) is that every
> global/static variable be kept in a seperate, dynamically allocated,
> memory location for each instance of each object...  calling a
> "create_new_instance" (or similar) procedure to allocate new ones
> as needed, and assign them some sort of ID or handle so each call to
> the service program could know which "object" you're referring to?

Exactly, one could pass the pointer of the "object" back and forth or a
handle... Personal preference. The list of objects could be contained in a
linked list or a btree or whatever makes sense. I like having the service
program do all the memory management though :-) And you could allocate the
memory in blocks and then do things in a way so that you would not have to
worry so much about a fragmented heap.

> In that way, you could keep the memory separate for each "instance"
> of the object that you need to deal with.
>
> Yes.  That could get very ugly.  But it'd probably work, which is
> pretty neat.  Now, can you make it become threadsafe?  :)
Yes I think so with the use of Semaphores and such. The burden of thread
safety of course depends on the creator of the service program. But seeing
as each call has one entry point into the service program that could make it
a lot easier.  A very inefficient way to do it is to try to allocate the
semaphore as the first step and that way no two threads could be changing
info at the same time. A better solution would be to have a locking scheme
per each attribute of each object. Somewhere in the middle of those two
extremes would be the most common route I would think.

> A compiler?  An intriguing idea!  What would it compile the source
> into?  MI?  Could you actually make an executable *PGM object, without
> calling an IBM-supplied compiler, somewhere?   (In which case, is your
> program really a compiler, or just a language converter?)

I really think that all compilers are language converters of some sort, and
yes I would probably target MI if I were such a masochist. Then I could use
the QPRCRTPG API to make the program object... Unfortunately it would be
limited to OPM


> An interpreter you could certainly do...  You could make your own
> "Eric-BASIC" which would be interpreted by your RPG program, and
> other people could write programs in it... :)
Simply evil :-) If I ever have that much time on my hands then I may just do
it :-) If I were to do the language thing I think I would port the Free
Pascal to the AS/400 as I really like Delphi and I would love to have a tool
like it for the AS/400 :-)

______________________________________________
Eric N. Wilson
President
Doulos Software & Computer Services
2913 N Alder St.
Tacoma WA 98407


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