RE: Calling an RPG procedure with optional parameters from C code

RPG doesn't allow optional parameters to be specified before required
ones either.

Note the RPG offers omittable (*OMIT) and optional (*NOPASS) parameters.

C/C++ don't have the equivalent of an omittable param.  Or rather, all
C/C++ parms passed by reference could be (are by default) omittable.

When you pass *OMIT to an RPG IV procedure, what you are really doing is
passing a NULL pointer.

Thus, in your C/C++ program just make sure you pass a NULL pointer for
the *OMITted parameter.

HTH,

Charles Wilt
--
iSeries Systems Administrator / Developer
Mitsubishi Electric Automotive America
ph: 513-573-4343
fax: 513-398-1121
  

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx 
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Phil Kestenbaum
Sent: Wednesday, November 01, 2006 10:45 AM
To: RPG programming on the AS400 / iSeries
Subject: RE: Calling an RPG procedure with optional 
parameters from C code

Neither C nor C++ allows optional parameters to be specified before
required ones.  In C++, optional parameters can only be 
specified at the
end like this:

void func( int param1, int param2, int optional1 = 0, int 
optional2 = 0
)
{
   ...
}
I'm not familiar with the latest C standard, but I don't 
believe you can
overload a function like that in any version of C.

However, if you are really getting desperate, you could always use the
... operator the way functions like printf() & scanf() do.

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Osborn, Stephen
Sent: Wednesday, November 01, 2006 8:25 AM
To: c400-l@xxxxxxxxxxxx; rpg400-l@xxxxxxxxxxxx
Subject: Calling an RPG procedure with optional parameters from C code

I have RPG procedures where the first two parameters are alternates,
i.e.
values must be supplied for 
param1, param3, param4, etc
or 
param2, param3, param4, etc

Using *OMIT I can call these in either mode from RPG, e.g.
callp procname(value1 : *OMIT : value3 : value4)
or 
callp procname(*OMIT : value2 : value3 : value4)

However I need to call some of these routines from some legacy C code.


How do I specify in C (both the prototype and the code) that param1 &
param2
can be *OMIT'd?


regards

Stephen Osborn
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