RE: This is cool. -- RPG400-L

It has taken me all day to fathom what's going on here. I suppose it's
because (to give me an excuse) I have not used a compiler that enabled
free-format D-specs. Once Jon showed (see below) the fixed-format, I
remembered that Mr. Tuohy showed me this years ago. Even used it more than
once.

Jerry C. Adams
It ain't bragging if you can do it. -Dizzy Dean
IBM i Programmer/Analyst
--
NMM&D
615-832-2730

-----Original Message-----
From: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Jon Paris
Sent: Saturday, July 29, 2017 10:16 AM
To: Rpg400 Rpg400-L
Subject: Re: This is cool.

Yes it does Alan. You apparently didn't get as far as page 3 where this code
appears:

D Messages DS
D 20a Inz('Invalid Item Code')
D 20a Inz('Too many selections')
D 20a Inz('Item Code required')
D 20a Inz('Huh?')
D Msg 20a Overlay(Messages) Dim(4)
See - no names!

When this is converted to free-form you cannot leave the name blank because
it would confuse the compiler and have to replace the blank with *N.

So the only difference is that I had to give the array a name in order to
allow Overlay to be used. IBM decided that they no longer wanted to support
Overlay against the DS name and so introduced POS instead and that allows
the DS name to be omitted. Personally I wouldn't have omitted the DS name
anyway even using POS to create the array.

Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Jul 28, 2017, at 6:54 PM, Alan Campin <alan0307d@xxxxxxxxx> wrote:

Jon, the article you reference says nothing about *N and about using Pos.
Using *N and Pos seems to be considerable improvement to me and, of
course, free format.

The neat thing I think is I have to name nothing except the array I am
trying to create. No trying to create dummy names that are nothing but
place holders.

On Fri, Jul 28, 2017 at 3:40 PM, Jon Paris <jon.paris@xxxxxxxxxxxxxx

<mailto:jon.paris@xxxxxxxxxxxxxx>> wrote:

Alan, when you say "Before I would have had to do something like ..."

When is "before" because I can't see anything in the technique that
could not have been done many moons ago. Ugly as sin but it could be
done in the original RPG IV if not RPG/400 - just not as easily.

Booth - you'll find the answers to why/how it works in this piece
which dates back to 2003. http://ibmsystemsmag.com/ibmi/
<http://ibmsystemsmag.com/ibmi/> developer/general/d-spec-discoveries
<http://ibmsystemsmag.com/ <http://ibmsystemsmag.com/>
ibmi/developer/general/d-spec-discoveries>

Jon Paris

www.partner400.com
www.SystemiDeveloper.com

On Jul 28, 2017, at 6:31 PM, Alan Campin <alan0307d@xxxxxxxxx> wrote:

1. ErrorReturn is a qualified data structure that has a field named
MessageId. When you call a system API it is filled.

dcl-ds ErrorReturn LikeDs(TD_StdErrorModel) Inz(*LikeDs);

dcl-ds TD_StdErrorModel Qualified Template;
Size Int(10) Inz(%Size(TD_StdErrorModel));
BytesAvailable Int(10) Inz(0);
MessageId Char(7);
*N Char(1); <<--- Reserved piece of memory but
you don't need to name.
MessageData Char(1024);
end-ds;

What I am showing is a lookup array but I am only naming the array.
*N means no name.

Before I would have had to do something like

dcl-ds dsOkList;
MsgId1 Char(7) Inz('CPF3C51');
Msgid2 Char(7) Inz('CPF3C52');
MsgId3 Char(7) Inz('CPF3C53');
MsgId4 Char(7) Inz('CPF3C54');
MsgId5 Char(7) Inz('CPF3C55');
OkList Char(7) Dim(5) Overlay(dsOkList) Ascend; end-ds;

The same thing but a lot more work and I don't need to worry about
name conflicts. MsgId1 is global in the procedure. If you name
another

variable

MsgId1 it would conflict. With *N, no name. Just storage allocated.

On Fri, Jul 28, 2017 at 3:06 PM, Booth Martin <booth@xxxxxxxxxxxx>

wrote:

It takes me a while to catch on. Its not clear to me exactly what
is happening here. I do not understand ErrorReturn.MessageID and
I'd also

bet

I do not understand *N

I say this because it looks to me like it doesn't do anything we

couldn't

already do with the same basic code. Therefore I am assuming I am

missing

something?

On 7/28/2017 1:18 PM, JRusling@xxxxxxxxxxx wrote:

It is...!

<snip>
dcl-ds *N;
*N Char(7) Inz('CPF3C51');
*N Char(7) Inz('CPF3C52');
*N Char(7) Inz('CPF3C53');
*N Char(7) Inz('CPF3C54');
*N Char(7) Inz('CPF3C55');
OkList Char(7) Dim(5) Pos(1) Ascend; end-ds;

If %Lookup(ErrorReturn.MessageId:OkList) > 0; </snip>

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