RE: FOR op-code

[Tom Daly <Tdaly@xxxxxxxxxxxxxx>]

Hans,

I take your point about breaking existing FOR loops.  That would be bad.
But as far as the syntax making it clear which direction to iterate....  The
problem is that I must know *beforehand* which direction to loop and commit
that to code.  Maybe it's that (reaching way back) BASIC showing.  The
increment variable should be evaluated once at the beginning of the loop.

An application for this that springs to mind is a READ/READP loop where I
need to get, let's say, the next 10 records or the previous 10 records.  Say
for a page-at-a-time SFL or something similar.

Tom

 |  -----Original Message-----
 |  From: boldt@ca.ibm.com [mailto:boldt@ca.ibm.com]
 |  Sent: Wednesday, December 12, 2001 09:13
 |  To: rpg400-l@midrange.com
 |  Subject: Re: FOR op-code
 |

|
 |  >But since we're on the subject of
 |  >wish-lists...
 |
 |  >I wish the FOR op-code did away with the TO/DOWNTO and
 |  instead looked at
 |  the
 |  >sign of the BY increment.  There would also have to be a
 |  change in the way
 |  >the limit value and the index are compared.
 |  >
 |  >So that I can fill an array 'forwards' or 'backwards', for
 |  instance.
 |  This
 |  >seems more 'natural' to me.
 |
 |  Since that might cause existing FOR loops to behave differently,
 |  this isn't going to happen.  With the current syntax, it is clear
 |  exactly which direction the loop interates.
 |
 |  One problem with the proposal is what happens when the sign of
 |  the increment variable changes during the looping?  The limit
 |  test would also change sense, and would likely cause the loop
 |  to exit earlier than expected since the index value would now
 |  be on the other side of the limit value.
 |
 |  Cheers!  Hans
 |
 |  Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com
 |
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