RE: CONST vs. VALUE on a pointer parameter

Darren,
        Sorry, I did not clearly read your message in regards to the
VALUE, CONST and pointers.  I reread the manual and I know see your
confusion between the two in regards to pointers.  Both states that the
value passed will not be modified from the caller's point of view.    I
think the difference is that VALUE passes the pointer address and that
the caller will not return a different pointer address, but it still
allows you to modify memory. 

        Since, CONST has the authority to create a temporary variable
(or pointer) passing a pointer via a pointer is... well... pointless.
You would be modifying a different memory location that will then be
discarded after the call.  SO, CONST says make the caller's value read
only and allow them to pass any similar sized value to this parameter
and the compiler will make up the difference by padding.  It can create
a temporary variable at compile time since it can identify the size of
the variable/constant being passed.  If the variable being passed is
exactly the same, then I think it just uses the address of that
variable.   Also, you need to consider the read only aspect.  Why would
you want the compiler to allow you to have the possibility to modify
read only memory?       

        This is how I understand pointers in the context of VALUE and
CONST.

Thank you,
Matt Tyler
WinCo Foods, LLC


-----Original Message-----
From: rpg400-l-bounces+mattt=wincofoods.com@xxxxxxxxxxxx
[mailto:rpg400-l-bounces+mattt=wincofoods.com@xxxxxxxxxxxx] On Behalf Of
darren@xxxxxxxxx
Sent: Friday, January 27, 2006 8:39 AM
To: RPG programming on the AS400 / iSeries
Subject: RE: CONST vs. VALUE on a pointer parameter

I'm familiar with the basic differences between CONST and VALUE.  I read
this information when writing my application and I inferred that the
actual
passing mechanics were the same between VALUE and CONST, except that
CONST
should not be changed by the calling program.  I can't see that this
information  clarifies why a call to an API would fail as mine did using
CONST for an INPUT only variable(pointer).  Did I miss something?





 

             "Tyler, Matt"

             <mattt@wincofoods

             .com>
To 
             Sent by:                  "RPG programming on the AS400 /

             rpg400-l-bounces@         iSeries" <rpg400-l@xxxxxxxxxxxx>

             midrange.com
cc 
 

                                                                    Fax
to 
             01/27/2006 10:20

             AM
Subject 
                                       RE: CONST vs. VALUE on a pointer

                                       parameter

             Please respond to

              RPG programming

              on the AS400 /

                  iSeries

             <rpg400-l@midrang

                  e.com>

 

 





Darren,
             First read the Book "WebSphere(r) Development Studio:
ILE RPG Programmer's Guide" found here,
http://publib.boulder.ibm.com/iseries/v5r2/ic2924/books/c0925074.pdf or
http://publib.boulder.ibm.com/infocenter/iseries/v5r3/topic/books/sc0925
07.pdf .

See Pages starting 135.

Thank you,
Matt Tyler
WinCo Foods, LLC


--

This is the RPG programming on the AS400 / iSeries (RPG400-L) mailing
list
To post a message email: RPG400-L@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/rpg400-l
or email: RPG400-L-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/rpg400-l.