On 19/09/2022 7:59 am, Charles Mills wrote:
I've never had occasion to try write OO programs on the mainframe.
to me it seems that the chief value of classes and class methods is a
way of organizing my subroutines and functions and limiting their
scope to particular uses which seems to me would be useful in some
mainframe programs
I gather some OO languages are available to OMVS users here
Let me jump in here with a very personal note and say I *have* written a very
successful* mainframe program in a totally OO paradigm. So yes, OO is totally
relevant to mainframe software.
And kudos to you because not everybody could make the jump from HLASM to
C++.
I have been coding in C++ and Java for so long OOP is second nature to
me now. Well, in C++ I prefer the interfaces using templates. Java has
morphed into into a hybrid OO/FP language since the introduction of the
Streams API in Java 8. It's common now not to code imperative loop
statements at all. One can use object based programming in any language
that supports function pointers. I have seen a lot of HLASM code that
would benefit from such a design. One of the key principles of OO was to
replace conditional logic with polymorphic types. An example in C is the
z/OS stdio library. fopen() is a factory function that returns an opaque
handle with read/write/close functions pointers set that can handle many
different access methods using the same abstract functions. This is a
clean design that unfortunately isn't as common as it should be.
To me, yes, it is a method of organization of data and subroutines. It is a totally different way of thinking
about things. Let me see if I can express this. You have a program. You want to add some functionality to it.
Rather than thinking separately "I will need some new data fields" and "I will need some new
subroutines" instead you think "I will need a 'package' of new data fields and subroutines that
operate on those fields." It is a way of organizing the effort that I found to work extremely well for
me. I cannot picture writing a large program any other way: not as a hodgepodge of fields and subroutines,
but rather as a collection of smallish 'packages' of data and their attendant subroutines.
Utterly industry-standard C++ is available for developing both "legacy" and UNIX programs on z/OS. The
program I refer to above is run with JCL as an STC; nothing external about it screams "C" or "OO"
or "OMVS."
*Licensed by quite a few "name" companies and then acquired by a big-name
software company for fairly big bucks.
Charles
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