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  1.  Home
  2. RPG400-L
  3. April 2001

Re: Variable length MODS

  • Subject: Re: Variable length MODS
  • From: tomh@xxxxxxxxx
  • Date: Mon, 16 Apr 2001 10:05:38 -0500

I was helping my son with a VisualBasic program recently, and we came across the DIM/REDIM statements which are used to set the upper limits of an array (not new to me, but they are to him).  Using the REDIM I could set the upper limit to a variable value in much the same way that we handle the MODS and pointers combo.  The difference is that with VBs REDIM I can't exceed the bounds specified in the variable, and don't need to set some arbitrary and ridiculously large DIM(value).




Jon.Paris@hal.it
Sent by: owner-rpg400-l@midrange.com

04/14/01 12:24 PM
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 >> What happens if I try to access Labels(4) in my  program?  Will I get
an array bounds error?  Will I get weird  data?
Maybe, maybe not.  If you have previously used occurrence (and you are
still using the same memory allocation) that data may still be there.  Or
you may get garbage or you may get a machine check.  The two things that
are certain are that you will not get the data you want and RPG will not
issue a bounds error - only hard crashes.


If you use dynamically allocated memory you _must_ assume all
responsibility for bounds checking yourself.


I'm still hopeful that Hans and Barbara will at least let us set the actual
top of any array/MODS in the future.  It would be so useful, not just in
the case of dynamic memory but also when doing SORTA, LOOKUP, etc. to have
the compiler constrain the operation to only the _active_ members.





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