Date:         Tue, 18 Jul 2000 14:13:19 -0600
Reply-To:     Kenneth Moody <KennethMoody@FIRSTHEALTH.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Kenneth Moody <KennethMoody@FIRSTHEALTH.COM>
Subject:      Re: SAS: Iterative do loops with until statement
Content-Type: text/plain; charset=us-ascii

The answer to your question (a) is in the definition of the iterative DO.  In your first example you've used one "specification", in the second example you've used three "specifications".  In the second example, the "until (flag=1)" is part of the third specification and doesn't get executed until the bottom of the loop when n is three.

You can mimic the behavior of the first example by explicitly coding the test at the bottom of the loop:
 do n= ...;


     if flag=1 then leave;
  end;

Ken Moody
First Health, Metrics Department
Voice: 916-374-3924
EMail: KennethMoody@firsthealth.com

>>> "Hudson, Spencer" <shudson@VIROPHARMA.COM> 07/18 12:25 PM >>>
Sometimes when you're not looking, the simple stuff comes and bites. In the
following two steps, the first stops at n = 6, but the second continues to
n=3. Can anyone tell me (a) why, and (b) can I mimic the first do loop using
the syntax of the second. I ask this because my real specification list does
not have even increments, so I cannot use the first syntax.

Thanks,
Spencer Hudson

308
309  data _null_;
310          flag = 0;
311          do n = 9 to 3 by -3 until (flag=1);
312                  if 7 >= n then flag = 1;
313                  put n= flag=;
314          end;
315          put n= flag=;
316  run;

N=9 FLAG=0
N=6 FLAG=1
N=6 FLAG=1
NOTE: The DATA statement used 0.01 seconds.


317
318  data _null_;
319          flag = 0;
320          do n = 9, 6, 3 until (flag=1);
321                  if 7 >= n then flag = 1;
322                  put n= flag=;
323          end;
324          put n= flag=;
325  run;

N=9 FLAG=0
N=6 FLAG=1
N=3 FLAG=1
N=3 FLAG=1