RE: Starting out with sub-procedures

["Jon Paris" <Jon.Paris@xxxxxxxxxxxxxx>]

JT

 >> That's in the C-world.  CPF checks number of parms,

Sorry but you are wrong, the system doesn't do checks.  The compilers can
generate code to check and some do - to some extent.  But they can only
count number of parms which is only part of the story.  For example, CL
programs check for the right number of parms, but in RPG400 the compiler
checks only for too many parms - not for too few.  RPG IV doesn't check
anything and will happily accept too many or too few.  Try calling this RPG
program with 1, 2, or 3 parameters and see what happens.

C     *entry        PList
C                   parm                    P1                1
C                   parm                    P2                1
C     P1            Dsply
C     P2            Dsply                   p2
C                   Eval      *InLR = *On

 >> and programs that pass wrong data types consistently error off.  They
don't corrupt data, generally speaking.

If it is a data type mismatch then it _may_ blow up - but not always, and
not predictably.  A packed field will appear perfectly valid for character
operations, but introduce (say) spaces into it in the called routine and
you'll have lots of fun later.  If you have never experienced this then all
I can say is that you have been lucky.  However, we are not just talking
about data types.  In fact corruption is more likely to occur with
mismatched lengths - e.g. passing a ten character field to a routine that
expects 20.

The critical point is that if you are expecting the system to check for you
then you are in for a nasty surprise at some point in time.

Given that this conversation is about subprocedures - which means bound
calls - we should also consider them here.  They work differently and there
is far less likelihood of a "missing" parm causing an immediate error since
there may well be a valid pointer on the stack - it just won't be to the
right data!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 >> OTOH:

 >> | Only nasty
 >> | explosions if you are lucky, and corrupted data if you are not.

 >> Is that why my posts are, apparently, being moderated by some group(s)
of
 >> people, besides David??

I have absolutely no idea what you are talking about nor do I understand the
relevance to this topic of the rant that follows so I'm going to pass on
that.

Jon Paris
Partner400
www.Partner400.com