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Nathan,
Thanks for your input!
I was thinking on this approach of multipying the data with one instance of
the program and saving the data using dynamic storage allocation too.
There are some details, I would change in your program (I would define the car
DS in the /Copy with the prototypes and use LIKEDS and qualified names for
the Car Properties), but that's not the issue of importance.
I skipped this approach ta the point, I began tho think about composition. A
car has a motor and a gearbox and some other complex components. A motor
itself is composed from other complex objects and maybe 10 steps down their
is a screw, wich is combined of elementar values.
Stability of this approach is rather weak too (its not you, who is responsable
for this, its ile). The Pointer to the car is located in the upper programm
(the example), storage allocation is done in the car programm, if the amounts
differ after a change of one of these programms we will get MCHCK conditions.
What about the activation group aspect here? What's happening if the example
runs in a diffrent activation group than the car programm? Now we have a
pointer in the example activation group pointing to storage allocated in the
car activation group, doesn't this get inconsistent if I would reclaim one of
them? Controlling Heap Size might be another problem to solve.
To avoid this, we can run car in the *CALLER Activation Group. Now it might
happen, that there exist two instances of the car programm in diffrent
Activation groups. Passing a car from one program to another the RCLACTGRP
problem comes back.
If we never reclaim Activation Groups the storage of the program grows and
grows.
I don't want to say, that you did not solve this problems, but it took you
some time to do. And same question to you I asked to Phil: is this available
as Open Source or Freeware, or has everybody to reevent the wheel and to
write this stuff on his own? In java it would be available as Open Source, if
java wouldn't have this capabilities already as base functinality.
And at least the java code to use a car object is more easy and the compiler
makes extensive type checks for you, even error conditions, that might occur
are checked by the complier. That all will make the java code more readable
and stable without any work of the programmer, than the rpg code could be
made by a very experienced rpg programmer like you.
Its not a comparison of programmers we need, its a comparison of compilers and
runtime enironments we have to do in a mailing list like java400-l. writing
in java, we don't need storage allocation by our own, we don't need
prototypes, the declaration (call it PI) is enough, there are no /copy
modules, that could differ. In java there is no binding of arrays of
procedure pointers at compile times, there are many things rpg doesn't
provide. You get this stuff all without paying, but not for free, you pay
with runtime overhead, but IMHO today the power of CPUs is high enough by low
costs to get the power this needs.
Dieter
On Freitag, 19. März 2004 21:50, Nathan M. Andelin wrote:
> > The problem here is: you have no qualified naming
> > for referencing methods and you can't have more
> > than one instance of a rpg program.
>
> Dieter,
>
> The following program uses a "Car" class to save and retrieve car
> properties. I've also included code to the *SRVPGM which defines the Car
> class, and procedure prototypes included in both modules, if you'd like to
> build and test this yourself.
>
> One instance of the *SRVPGM is used to create multiple instances of the Car
> object. If you read the *SRVPGM code carefully, I think you'll see the
> technique.
>
> HTH,
>
> Nathan.
>
>
> *********************************************
>
> Example:
> program using "car" class
>
> *********************************************
>
> *-----------------------------------------------------------------
>
> /COPY *LIBL/QRPGLESRC,CAR#1
>
> *-----------------------------------------------------------------
>
> D car DS
> D car_make 20A
> D car_model 20A
> D car_year 4S 0
>
> *-----------------------------------------------------------------
>
> D car1 S *
> D car2 S *
>
> *-----------------------------------------------------------------
> * create two (2) instances of car object
>
> C Eval car1 = carNew
> C Eval car2 = carNew
>
> *-----------------------------------------------------------------
> * set car # 1 properties
>
> C Callp carSetInst(car1)
>
> C Callp carSetMake('Ford')
> C Callp carSetModel('Taurus')
> C Callp carSetYear(1996)
>
> *-----------------------------------------------------------------
> * set car # 2 properties
>
> C Callp carSetInst(car2)
>
> C Callp carSetMake('Volkswagon')
> C Callp carSetModel('Beetle')
> C Callp carSetYear(1964)
>
> *-----------------------------------------------------------------
> * get car # 1 properties
>
> C Callp carSetInst(car1)
>
> C Eval car_make = carGetMake
> C Eval car_model = carGetModel
> C Eval car_year = carGetYear
>
> *-----------------------------------------------------------------
> * display car # 1
>
> C car dsply
>
> *-----------------------------------------------------------------
> * get car # 2 properties
>
> C Callp carSetInst(car2)
>
> C Eval car_make = carGetMake
> C Eval car_model = carGetModel
> C Eval car_year = carGetYear
>
> *-----------------------------------------------------------------
> * display car # 2
>
> C car dsply
>
> *-----------------------------------------------------------------
> * destroy both cars
>
> C Callp carSetInst(car1)
> C Callp carDestroy
> C Callp carSetInst(car2)
> C Callp carDestroy
>
> *-----------------------------------------------------------------
> * end program
> C Seton LR
> C Return
>
>
> *********************************************
>
> Example:
> *SRVPGM defining car class
>
> *********************************************
>
> H NoMain
>
> * ----------------------------------------------------------------
>
> /COPY *LIBL/QRPGLESRC,CAR#1
>
> * ----------------------------------------------------------------
>
> D car DS Based(carPtr)
> D car_make 20A
> D car_model 20A
> D car_year 4S 0
>
> D carSz C %Size(car)
>
> * ----------------------------------------------------------------
>
> P carNew B Export
>
> * ----------------------------------------------------------------
>
> D carNew PI *
>
> * ----------------------------------------------------------------
>
> C Alloc carSz carPtr
>
> C Clear car
>
> C Return carPtr
>
> P carNew E
>
> * ----------------------------------------------------------------
>
> P carSetInst B Export
>
> * ----------------------------------------------------------------
>
> D carSetInst PI
> D ptr * Value
>
> * ----------------------------------------------------------------
>
> C Eval carPtr = ptr
>
> P carSetInst E
>
> * ----------------------------------------------------------------
>
> P carSetMake B Export
>
> * ----------------------------------------------------------------
>
> D carSetMake PI
> D make 20A Const
>
> * ----------------------------------------------------------------
>
> C Eval car_make = make
>
> P carSetMake E
>
> * ----------------------------------------------------------------
>
> P carSetModel B Export
>
> * ----------------------------------------------------------------
>
> D carSetModel PI
> D model 20A Const
>
> * ----------------------------------------------------------------
>
> C Eval car_model = model
>
> P carSetModel E
>
> * ----------------------------------------------------------------
>
> P carSetYear B Export
>
> * ----------------------------------------------------------------
>
> D carSetYear PI
> D year 4S 0 Const
>
> * ----------------------------------------------------------------
>
> C Eval car_year = year
>
> P carSetYear E
>
> * ----------------------------------------------------------------
>
> P carGetMake B Export
>
> * ----------------------------------------------------------------
>
> D carGetMake PI 20A
>
> * ----------------------------------------------------------------
>
> C Return car_make
>
> P carGetMake E
>
> * ----------------------------------------------------------------
>
> P carGetModel B Export
>
> * ----------------------------------------------------------------
>
> D carGetModel PI 20A
>
> * ----------------------------------------------------------------
>
> C Return car_model
>
> P carGetModel E
>
> * ----------------------------------------------------------------
>
> P carGetYear B Export
>
> * ----------------------------------------------------------------
>
> D carGetYear PI 4S 0
>
> * ----------------------------------------------------------------
>
> C Return car_year
>
> P carGetYear E
>
> * ----------------------------------------------------------------
>
> P carDestroy B Export
>
> * ----------------------------------------------------------------
>
> C Dealloc carPtr
>
> P carDestroy E
>
> *********************************************
>
> Example:
> Car procedure prototypes
>
> *********************************************
>
> D carNew PR * ExtProc('carNew')
>
> D carSetInst PR ExtProc('carSetInst')
> D inst * Value
>
> D carSetMake PR ExtProc('carSetMake')
> D make 20A Const
>
> D carSetModel PR ExtProc('carSetModel')
> D model 20A Const
>
> D carSetYear PR ExtProc('carSetYear')
> D year 4S 0 Const
>
> D carGetMake PR 20A ExtProc('carGetMake')
>
> D carGetModel PR 20A ExtProc('carGetModel')
>
> D carGetYear PR 4S 0 ExtProc('carGetYear')
>
> D carDestroy PR ExtProc('carDestroy')
>
>
> _______________________________________________
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--
mfG
Dieter Bender
DV-Beratung Dieter Bender
Wetzlarerstr. 25
35435 Wettenberg
Tel. +49 641 9805855
Fax +49 641 9805856
www.bender-dv.de
eMail dieter.bender@xxxxxxxxxxxx
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