RE: what is object oriented programming

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx]On Behalf Of David Gibbs
Sent: Tuesday, May 06, 2003 1:38 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: what is object oriented programming


>> Do you agree that an object is a "thing" that is accessed only thru
>>exposed
>> interfaces? That no access to the internal components of the object, by
>> definition, is allowed?

>An object is a THING that encapsulates both data & methods to operate on
>that data.

>A data structure is simply an area of memory that has been given a specific
>format.  There is no means for code to be attached to a data structure.


Consider an rpg compiler pre processor whose use is enforced by the DP mgr
via the indomitable security of the iSeries.  The pre processor scans the
RPG code for any direct references to the subfields of data structures which
are declared LIKEDS a predefined set of data structs.
 d Tp_Order        ds                qualified
 d  CustNbr                     7a
 d  OrdNbr                      7a
 d  OrdQty                      7p 0

 d Orders1         ds                likeds(Tp_Order)

Any such references have to occur in procs which start with the nickname of
the template and receive the data struct by reference as the first parm.

  /free
       orders1.OrdNbr = 'abc' ;                // pre processor error!
       Order_AssignOrdNbr( orders1: 'abc' ) ;  // thats OO!

 p Order_AssignOrdNbr  b
 d Order_AssignOrdNbr  pi
 d InOrder                            likeds(Tp_Order)
 d InOrdNbr                      7a   value
  /free
       InOrder.OrdNbr  = InOrdNbr ;  // pre processor says ok.
       return ;
  /end-free
 p                      e

Wouldnt those RPG data structures then be considered objects?

-Steve