Re: read on a do loop

dkahn@xxxxxxxxxxxxxxxxx wrote:

"Jeff Crosby" <jlcrosby@xxxxxxxxxxxxxxxx> wrote:

So do this:

Dou %eof(myfile);
  Read myfile;
  If %eof(myfile);
    Leave;
  Endif;
  If itactv = 'N';
    Iter;
  Endif;
  // process
Enddo;

This works of course, but I still have a minor quibble with it. The only
way out of the loop is via the Leave operation, so why code %eof as the end
condition on the Do? One very good answer would be that it documents the
condition that causes processing to break out of the loop. However, it
looks like something that ought itself to cause the loop to end, but it
actually doesn't. Whenever I see this construction I always find myself
looking twice at the code to see if I've missed something. If the Leave is
the only way out of the loop I would prefer to see the until condition
coded explicitly as an impossible one, so it would read something like:

 dou '0';   // Do forever
   Read myfile;
   If %eof(myfile);
     Leave;
   Endif;
   If itactv = 'N';
     Iter;
   Endif;
   // process
 Enddo;

I know many people will think this is less clear than Jeff's code, but I
think it's slightly more correct. To me <Dou %eof(myfile)> implies that
eventually processing could reach this point with the %eof condition true.
<Dou '0'> on the other hand (ugly though it is) tells me explicitly that
there needs to be another way of breaking out of the loop and highlights
the significance of the Leave as the only way of doing so.

--
Dave...
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