Re: RE: Variable parameter type

["David Morris" <dmorris@xxxxxxxxxxxxx>]

Bob,

Passing pointers is obviously fraught with danger.  That is the only 
alternative 
when you have a long list of variable type parameters.  We are only talking 
about 1 parameter with three possible types.  This breaks down when there 
several parameters with a bunch of types.  This is why RPG should really 
support variable types.  Without this support RPG programmers are forced 
to manage storage, which is not the best use of our time.

Speaking as a RPG guy with almost no C++ experience, I would think that
overloading is one method that could be used to support this in RPG.  RPG 
could also benefit from parameterized type support.  This would be like to a 
template in C++.

David Morris

>>> Bob Crothers <bob@cstoneindy.com> 11/17 3:36 AM >>>
Speaking as a C++ guy with a LOT of experience in pointers, BEWARE OF 
THIS APPROACH!

Passing back a generic pointer (Don't know if you can even do this in 
RPG) and letting the caller decide what it is a pointer to, is very 
dangerous.  This is the sort of thing that gives pointers a bad name.

If you pass back a pointer  to a character string, but the app decides 
that you should be passing a pointer to an integer, then nasty things 
will happen.

I highly recommend that you do not do this.  Instead, declare 3 
different functions.

In C++, there is a cool thing called "overloading" that is meant for 
this sort of thing.  Perhaps someday, RPG will be able to do this.

Say you have a function "ConvertMyThing" that must handle 3 different 
types of parms.  You would declare them as:

int ConvertMyThing (int myNumber);

string ConvertMyThing (string myString);

double ConvertMyThing (double myDouble);

In your code, you would always just call ConvertMyThing ().  And the 
compiler picks the correct function to call based on the parameter 
types you are using.  And of course, if the type changes, the correct 
function is always called.

BTW, like anything else, there can be pitfalls in overloading also.

Regards,
Bob Crothers
Cornerstone Communications, LLC
www.faxserver401.com 


-----Original Message-----
From:   Denis Robitaille [SMTP:DRobitaille@cascades.com] 
Sent:   Tuesday, November 17, 1998 9:05 AM
To:     MIDRANGE-L@midrange.com 
Subject:        Variable parameter type

Hello all, on a project i am working on, i need to write a program or 
procedure that will return a value. The type of the value returned 
depends on the parameters passed. It can be a number, a caracter 
string or a booleean. I would like to avoied declaring 3 parameters 
for each possible type of values. I tought that i may use a pointer, 
but i am not sure.

Any suggestions?

Denis Robitaille
Cascades inc.
Tel: 819-363-5187
DRobitaille@cascades.com

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