Re: Latest RPG Updates -- RPG400-L

Hiding overridden procedures does not necessarily have to break
compatibility. I am not sure how it works right now, I suspect that the
exports appear in the service program in binder source order. Based on the
way service programs work, I don't think you would necessarily break
compatibility of existing programs. Maybe it would force a source change
when you recompile though. Maybe a new binder source keyword that maintains
the slot, but prevents binding to the overridden procedure except through
the common procedure name.

This would prevent the unique procedure names from being used going forward
which is the point of procedure overloading anyway.

On Wed, Oct 9, 2019 at 11:35 AM Jon Paris <jon.paris@xxxxxxxxxxxxxx> wrote:

Then you'd also have to have an extra rule that said that no overridden
entity could ever be called directly. In other words you'd break
compatibility with existing code that was being enhanced.

On Oct 9, 2019, at 8:20 AM, Mark Murphy <jmarkmurphy@xxxxxxxxx> wrote:

As I am not in a position to test this, my only real concern is that I
would have to have extra prototypes in my outline list (though this could
possibly be mitigated by RDi). Maybe they could hide overridden

prototypes

in the outline unless they were specifically used.

On Wed, Oct 9, 2019 at 11:13 AM Mark Murphy <jmarkmurphy@xxxxxxxxx>

wrote:

It should be able to if it were completely implemented, but as of now,

it

only supports character parameters.

On Wed, Oct 9, 2019 at 9:29 AM Vernon Hamberg <vhamberg@xxxxxxxxxxxxxxx

wrote:

Jon

Could operational descriptor support help with any of this?

Vern

On 10/9/2019 1:24 AM, Jon Paris wrote:

"I'm not convinced it would be impossible."

Not impossible no - b ut it requires work at the OS level - RP{G could

not do it by itself in any meaningful fashion. At present the

information

is just not stored anywhere in the compiled objects. Foe example a

program

knows its maximum an minimum number of parameters - but not what type

of

data and size they should be. Same with service program procedures.

that

data is just not stored by the system. The closest we come is when the
compiler generates on request the PCML data for a call. But even that

would

require a lot more work before it could be used for the type of
introspection needed. PCML currently can only support a subset of the

full

range of data that can be passed as parameters - so PCML has to be

enhanced

significantly before you can even think of using it as the foundation

for a

call mechanism.

Not saying it wouldn't be nice - just that I don't see it happening

any

time soon.

On Oct 8, 2019, at 9:24 PM, Peter Dow <petercdow@xxxxxxxxx> wrote:

I remember having this same feeling about having to include PIs and

PRs for every procedure. That eventually was resolved at the local

level.

Yes, it would be a lot more work for the compiler to have to look at

the

service program to determine the prototypes for each candidate

procedure;

I'm not convinced it would be impossible. Same thing with procedure
prototypes.

My understanding of programs and other objects on the IBM i is that

they can be composed of object subtypes, for example a file has

metadata,

index data, actual data, etc. To make things simpler for the compiler,

how

about a subtype object containing the prototypes?

I know, Barbara does a great job and has more than enough work just

adding all the other things we want RPG to do, and this is not that

big a

deal. I just don't like to think that it's impossible.

On 10/8/2019 4:37 PM, Jon Paris wrote:

I thought that is what I had said Peter - but yes ALL have to be

present otherwise how would the overload one know which to pick? If

they

are not there it has nothing to compare with.

The only time that an overloaded prototype is not required is for

procedures that are local and the parameter information can de derived

from

the procedure interface.

On Oct 8, 2019, at 3:52 PM, Peter Dow <petercdow@xxxxxxxxx> wrote:

Yes, but my question is, are the candidate prototypes *required*,

or

just the overloading prototype? If it is indeed fundamentally a

compiler

directive, then it would seem they are all required. And if they're

all

required, one might as well use the candidate prototypes.

On 10/8/2019 1:21 PM, Jon Paris wrote:

Basically the rules haven't changed. For a procedure/program to

be

called, a prototype (or the PI for internals) must be present.

That includes the overloading proto. Normally I would have all

(say) three protos in a /Copy source - I'm just going to add the

overload

one to that set. No increase in work except for the original

definition of

the overload proto.

This is all a compile time function and as I said earlier

fundamentally a compiler directive in a different form.

On Oct 8, 2019, at 1:11 PM, Peter Dow <petercdow@xxxxxxxxx>

wrote:

Jon,

Assuming the FORMAT procedure and its candidate procedures are

all

in a service program, how do I use it in another RPG program? I would
guess that I have to put the prototype in the RPG program, yes? Do I

have

to put all the candidate prototypes in there too? My thought was the

RPG

program using it would simply have

Dcl-Pr Format Override( ProcA, PgmB, JavaC );

but now that I put it that way, the compiler would have to go to

the service program to check my usage against each of those candidate
prototypes to see if it's allowed.

--
*Peter Dow* /
Dow Software Services, Inc.
909 793-9050
petercdow@xxxxxxxxx <mailto:petercdow@xxxxxxxxx>
pdow@xxxxxxxxxxxxxx <mailto:pdow@xxxxxxxxxxxxxx>

/
On 10/8/2019 12:14 PM, Jon Paris wrote:

FORMAT is never exported because it is only really a compiler

directive.

For example thing of it this way.

Dcl-Pr Format Override( ProcA, PgmB, JavaC );

This is handled by the compiler much like a conditional

compilation directive such as ...

/IF ParmMatches ProcA
CallP ProcA(parm);
/ELSEIF ParmMatches ProcB
CallP PgmB(parm);
/ELSE
....

It is that simple.

On Oct 8, 2019, at 11:28 AM, Justin Taylor <

JUSTIN@xxxxxxxxxxxxx>

wrote:

Is FORMAT exported? There will be times when I want it

exported

and other times I don't. My best guess is that it inherits from the

actual

procedures.

-----Original Message-----
From: Jon Paris [mailto:jon.paris@xxxxxxxxxxxxxx]
Sent: Tuesday, October 08, 2019 1:04 PM
To: RPG programming on IBM i <rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: Latest RPG Updates

Actually it doesn't matter if the procedure is exported or not.

In fact the overloaded routines can include programs, Java calls, and
subprocs.

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