Re: New Template Type

[Charles Wilt <charles.wilt@xxxxxxxxx>]

Bob,

Coding isn't the problem.

The issue Mark is trying to solve is ensuring that a procedure passed by
pointer has the interface expected.
Right now, it's left to the developer to ensure this.  If you screw it up
and your lucky, the code will crash.  If you're not lucky you can have all
kinds of funny runtime issues caused by parameter mismatches.

Mark, I agree this would be nice to have....it would be some nice insurance
to have when using procedure pointers

Charles

On Wed, Mar 25, 2015 at 9:35 AM, Roche, Bob <broche@xxxxxxxxxxxxxxxxx>
wrote:

> Save it as a snippet?
>
> -----Original Message-----
> From: RPG400-L [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Mark
> Murphy/STAR BASE Consulting Inc.
> Sent: Wednesday, March 25, 2015 8:30 AM
> To: RPG programming on the IBM i (AS/400 and iSeries)
> Subject: New Template Type
>
> You know what would be useful? A prototype template, let me explain.
>
> I created a procedure that takes as a parameter a pointer to a callback
> procedure. The module with the caller (procA) and the callback (procB)
> procedures doesn't really need a prototype for procB as it isn't really
> called in a traditional way. But, the called procdedure (procC) which
> receives a pointer to procB and executes it, does need a prototype that
> references the procedure pointer. Now that prototype in procC has to be
> local because it references the procedure pointer being passed in as a
> parameter, but even if I found a way to make the pointer and prototype
> global, I couldn't use the same prototype for procB because it references
> the pointer, and I really don't necessarily always want to use the same
> name for procB. It is a callback after all, and I might have more than one
> procedure in a given program providing services to procC. A prototype
> template would allow me to define the prototype in procC
> LikeProc(callback_t) with a reverence to the local procedure pointer be
>
>  ing passed in as a parameter, and also define the callback procB
> LikeProc(callback_t) which would provide the matching procedure interface
> without the procedure pointer, but the parameters and return would be the
> same. Here is what I would like to see.
>
> dcl-pr callback_t Int(10) Template;
>   Parm1     <keywords>;
>   Parm2     <keywords>;
> end-pr;
>
>
> dcl-proc procA;
>
>   ...
>   procC(%paddr(procB));
>   ...
> end-proc;
>
> dcl-proc procB LikeProc(callback_t);
>
>   <procedure body>
> end-proc;
>
> dcl-proc procC;
>   dcl-pi *n;
>     callbackPtr   Pointer(*Proc);
>   end-pi;
>
>   dcl-pr callback  LikeProc(callback_t) ExtProc(callbackPtr);
>
>   callback(...: ...);
>   ...
> end-proc;
>
> Mark Murphy
> STAR BASE Consulting, Inc.
> mmurphy@xxxxxxxxxxxxxxx
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