Date:         Thu, 4 Oct 2001 18:04:34 -0600
Reply-To:     Jack Hamilton <JackHamilton@FIRSTHEALTH.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Jack Hamilton <JackHamilton@FIRSTHEALTH.COM>
Subject:      Re: Order in the data step
Comments: To: pete.lund@NWCSR.COM
Content-Type: text/plain; charset=us-ascii

My guess it that it's because SAS uses a one-pass compiler in the data step.  Or perhaps it uses a two pass compiler now, but originally used a one pass compiler, and that particular design constraint was left in place.

A hint to what's happening:  put the statement

   array z _numeric_;

before the SET statement in DATA A:

-----
336  data a;
337   length _numeric_ 3;
338   array z _numeric_;
WARNING: Defining an array with zero elements.
339   set x;
340  run;
-----

The WARNING message is issued for the same reason that the lengths aren't set.



--
JackHamilton@FirstHealth.com
Development Manager, Technical Group
METRICS Department, First Health
West Sacramento, California USA


>>> "Pete Lund" <pete.lund@NWCSR.COM> 10/04/2001 4:49 PM >>>
Howdy all-
  In a private post Puddin' Man suggested that I be sadistic and ask Ian to
explain a twist on one of the previous posts in this thread.  I thought I'd
go all the way and pose it to all.  Why is the behavior of the length
statements in the datasteps creating A and B different?  The variables in A
remain with length 8, while those in B are converted to length 3.  BTW - as
Puddin' demonstrated earlier, if you move the LENGTH statements after the
SET then both the _NUMERIC_ and variable list behave the same.

data x;
 input var1= var2= var3=;
cards;
var1=6 var2=8 var3=9
var1=6 var3=9
run;

data a;
 length _numeric_ 3;
 set x;
run;

data b;
 length var1 var2 var3 3;
 set x;
run;

proc contents data=a;
run;
proc contents data=b;
run;


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Pete Lund
Northwest Crime and Social Research, Inc.
313-D Fifth Ave SE
Olympia, WA   98501
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pete.lund@nwcsr.com
www.nwcsr.com
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