Re: Common routines and optional parameters

[Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx>]

Ahhhhhhhhhhhhhh.  That's very interesting, Charles.  I tried a lot of 
combinations but not that one.  I'll look at it the next time I get a 
chance.


On 4/2/2019 3:33 PM, Charles Wilt wrote:
> Joe,
>
> You can take the %addr() of a CONST parm...but only if comparing it to
> *NULL.  In other words, the compiler will allow
> if %addr(iParm1) = *NULL;
>
> but it won't allow
> myPtr = %addr(iParm1);
>
> But you only need to do that if the parm is options(*OMIT)
>
> with options(*NOPASS), all you need is %parms().
>
>
> I'd probably do LogCommon() with all parms as options(*OMIT)
>
> then for instance, in LogCode() do
> select;
>    when %parms() = 2;
>       LogCommon(*OMIT:code:*OMIT:*OMIT:*OMIT);
>   when %parms() = 3;
>    LogCommon(*OMIT:code:parm1:*OMIT:*OMIT);
>   <ect>
> endsl;
>
> Charles
>
> On Tue, Apr 2, 2019 at 2:13 PM Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx> wrote:
>
> > Every time I get close to a solution, I get whacked.
> >
> > Here's my simple case.  I want to write this procedure:
> >
> >          dcl-proc LogData;
> >            dcl-pi *n;
> >              iTYPE like(dsLOGDTA.L0TYPE) const;
> >              iCODE like(dsLOGDTA.L0CODE) const;
> >              iPARM1 like(dsLOGDTA.L0PARM1) const options(*nopass);
> >              iPARM2 like(dsLOGDTA.L0PARM2) const options(*nopass);
> >              iPARM3 like(dsLOGDTA.L0PARM3) const options(*nopass);
> >            end-pi;
> >
> > It's really pretty simple.  A type, a code, and up to 3 optional
> > parameters, all of which can be literals or expressions.  The above
> > works.  However, I'd like to encapsulate those further so users can call
> > them without the type and code, like so:
> >
> >          dcl-proc LogCode;
> >            dcl-pi *n;
> >              iCODE like(dsLOGDTA.L0CODE) const;
> >              iPARM1 like(dsLOGDTA.L0PARM1) const options(*nopass);
> >              iPARM2 like(dsLOGDTA.L0PARM2) const options(*nopass);
> >              iPARM3 like(dsLOGDTA.L0PARM3) const options(*nopass);
> >            end-pi;
> >
> >          dcl-proc LogType;
> >            dcl-pi *n;
> >              iTYPE like(dsLOGDTA.L0TYPE) const;
> >              iPARM1 like(dsLOGDTA.L0PARM1) const options(*nopass);
> >              iPARM2 like(dsLOGDTA.L0PARM2) const options(*nopass);
> >              iPARM3 like(dsLOGDTA.L0PARM3) const options(*nopass);
> >            end-pi;
> >
> >          dcl-proc LogOnlyParms;
> >            dcl-pi *n;
> >              iPARM1 like(dsLOGDTA.L0PARM1) const options(*nopass);
> >              iPARM2 like(dsLOGDTA.L0PARM2) const options(*nopass);
> >              iPARM3 like(dsLOGDTA.L0PARM3) const options(*nopass);
> >            end-pi;
> >
> > I'd like these three functions all to call LogData.  Each of them
> > defaults the values that are not passed in.  I know I can pass "special
> > values" for type and code, but for various reasons I'd really like to be
> > able to call without those parameters.  This seemed like an easy thing
> > to do, but I ran into difficulties. Clearly I can't just call this way
> > from LogCode:
> >
> >      LogData( C_DEFAULT_TYPE: iCODE: iPARM1: iPARM2: iPARM3);
> >
> > I'll get an MCH pointer exception if I don't pass all three variables.
> > I tried being a little sneakier and did this:
> >
> >      LogCommon( C_DEFAULT_TYPE: iCODE: %parms:
> >        %addr(iPARM1): %addr(iPARM2): %addr(iPARM3));
> >
> > I wrote a new routine LogCommon that instead of the parameters accepts
> > pointers to the parameters along with (for belt and suspenders security)
> > passing the number of parameters.  I only then used the actual number of
> > parameters that were passed, and ignore the others.  Initial testing
> > looked good with the address of unpassed parameters being sent as *NULL.
> >
> > Unfortunately, it turns out you can't get the address of a parameter
> > defined this way:
> >
> >             iPARM1 like(dsLOGDTA.L0PARM1) const options(*nopass);
> >
> > You can only get the address of this:
> >
> >              iPARM1 like(dsLOGDTA.L0PARM1) options(*nopass);
> >
> > Specifying /const/ angers the compiler and it won't let you take the
> > address of the parameter.
> >
> > So now I'm stuck.  My guess is I'll end up with a common routine with no
> > optional parameters and code like this in every front end:
> >
> > if %parms = 0;
> >     LogCommon( C_DEFAULT_TYPE: C_DEFAULT_CODE: ' ': ' ': ' ');
> > elseif %parms = 1;
> >     LogCommon( C_DEFAULT_TYPE: C_DEFAULT_CODE: iParm1: ' ': ' ');
> > elseif %parms = 20;
> >     LogCommon( C_DEFAULT_TYPE: C_DEFAULT_CODE: iParm1: iParm2: ' ');
> > else;
> >     LogCommon( C_DEFAULT_TYPE: C_DEFAULT_CODE: iParm1: iParm2: iParm3);
> > endif;
> >
> > Has anybody else dealt with this?  It's a common pattern in Java, and
> > I'd like to be as clean about it as possible as I start to build some
> > library functions.
> >
> >
> >
> >
> >
> >
> >
> >
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