Re: Optional Parameters in Subproceedures

Hello Mike,

You wrote:
>Thanks, one more question. How can I tell if that parameter was passed or
>not?

That depends on how the parameter was coded on the prototype.

OPTIONS(*NOPASS) means the parameter is optional, i.e., it may not even be
there at all.

OPTIONS(*OMIT) means the parameter is omissable.  That means it is required
but you can specify *OMIT to cause a null pointer to be passed.

MEMORISE THIS *********
Optional and omissable are distinctly different things and not
interchangeable!
***********************

If the parameter is coded as OPTIONS(*NOPASS) then use %PARMS to check the
parameter count.

C               IF      ( %PARMS >= 2 )
 *              do stuff

If the parameter is coded as OPTIONS(*OMIT) then a null pointer is passed
and %PARMS will count it.  You can test the address using %ADDR and
comparing for *NULL. (You can also call CEETSTA to test for the omitted
argument but %ADDR is easier.)

C               IF      ( %ADDR(parm1) <> *NULL )
 *              do stuff

If the parameter was coded as OPTIONS(*NOPASS : *OMIT) then you MUST use
%PARMS followed by a call to CEETSTA to test for an omitted argument.  The
reason you must do it this way is that if the parameter was not specified
at all CEETSTA will fail with a missing descriptor (or worse, pick up a
descriptor on the stack from a previous function call).  If *OMIT was
specified then %PARMS will count it as a parameter. You must do both things
to know whether you have a valid parameter or not.

C               IF      ( %PARMS >= 2 )
C               CALLP   ceeTestArg( argOmitted : 2 : *OMIT )
C               ENDIF

C               IF      ( %PARMS >= 2 AND
C                         argOmitted = $CEE_ARG_OMITTED_NO )
 *              do stuff

NOTE: In the above example I have prototyped the CEETSTA bound procedure so
I can use it on CALLP.  Without the prototype you have to code:

C               CALLB   'CEETSTA'
C               PARM                    argOmitted
C               PARM    2               argNbr
C               PARM                    *OMIT

(or something like that -- I haven't used CALLB for years)

Regards,
Simon Coulter.

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