When statements such as DO WHILE, DO UNTIL, and IF, as well as functions such IFC and IFN, contain compound expressions to be evaluated, all expressions are evaluated prior to determining the overall truth of the compound expression. This can lead to unexpected warning or error messages in the SAS log when you anticipate that expressions are evaluated in the order in which they appear.

The evaluations do not cease when the overall truth could be determined without evaluating all expressions.

To prevent these unexpected messages, do not write code that depends on the order of evaluation or relies on fewer than every expression being evaluated.

Operating System and Release Information

Product Family	Product	System	SAS Release
			Reported	Fixed*
SAS System	Base SAS	Microsoft Windows Server 2003 Enterprise 64-bit Edition	9.2 TS2M0
		Microsoft Windows Server 2003 Datacenter 64-bit Edition	9.2 TS2M0
		Microsoft Windows XP 64-bit Edition	9.2 TS2M0
		Microsoft® Windows® for x64	9.2 TS2M0
		Microsoft Windows Server 2003 Datacenter Edition	9.2 TS2M0
		Microsoft Windows Server 2003 Enterprise Edition	9.2 TS2M0
		Microsoft Windows Server 2003 Standard Edition	9.2 TS2M0
		Microsoft Windows XP Professional	9.2 TS2M0
		Windows Vista	9.2 TS2M0
		64-bit Enabled AIX	9.2 TS2M0
		64-bit Enabled HP-UX	9.2 TS2M0
		64-bit Enabled Solaris	9.2 TS2M0
		z/OS	9.2 TS2M0
		Microsoft® Windows® for 64-Bit Itanium-based Systems	9.2 TS2M0
		HP-UX IPF	9.2 TS2M0
		Linux	9.2 TS2M0
		Linux for x64	9.2 TS2M0
		OpenVMS on HP Integrity	9.2 TS2M0
		Solaris for x64	9.2 TS2M0

* For software releases that are not yet generally available, the Fixed Release is the software release in which the problem is planned to be fixed.

---

/* create test data */

data test;
  infile datalines truncover;
  input ID :$3. chgdate ??mmddyy10.;
  format chgdate date9.;
datalines;
aaa .
bbb 1/1/2009
ccc 1/1/2008
ddd 1/1/2007
eee 1/1/2006
fff .
ggg 9/1/2009
hhh 8/1/2009
iii 7/1/2009
jjj 6/1/2009
kkk 5/1/2009
mmm .
nnn 4/1/2009
ppp 3/1/2009
qqq 2/1/2009
;

/* generates warning message */
%let dt = '02Oct2009'd;
data result1 ;
  set test;
IF not (CHGDATE = .  OR  &dt - CHGDATE > 370) THEN                 
  output;   
run; 

/* does not generate warning message */
data result2 ;
  set test;
if chgdate ne .;
IF not( &dt - CHGDATE > 370) THEN                 
  output;   
run; 

Output when messages are generated                                      

Obs    ID       chgdate

 1     bbb    01JAN2009
 2     ggg    01SEP2009
 3     hhh    01AUG2009
 4     iii    01JUL2009
 5     jjj    01JUN2009
 6     kkk    01MAY2009
 7     nnn    01APR2009
 8     ppp    01MAR2009
 9     qqq    01FEB2009

Output when no messages are generated                                   

Obs    ID       chgdate

 1     bbb    01JAN2009
 2     ggg    01SEP2009
 3     hhh    01AUG2009
 4     iii    01JUL2009
 5     jjj    01JUN2009
 6     kkk    01MAY2009
 7     nnn    01APR2009
 8     ppp    01MAR2009
 9     qqq    01FEB2009

All expressions in a compound expression are evaluated regardless of whether the Boolean truth of the compound expression could be determined by evaluating only the first or less than every expression.

Type:	Usage Note
Priority:
Topic:	Common Programming Tasks ==> Selecting Data Common Programming Tasks ==> Reading and Writing SAS Data Common Programming Tasks ==> Combining Data Common Programming Tasks ==> Conditional Processing SAS Reference ==> Statements ==> Action ==> IF, subsetting SAS Reference ==> DATA Step SAS Reference ==> Statements ==> Control ==> DO UNTIL SAS Reference ==> Statements ==> Control ==> DO WHILE SAS Reference ==> Statements ==> Control ==> IF-THEN/ELSE SAS Reference ==> Functions ==> Character ==> IFC SAS Reference ==> Functions ==> Character ==> IFN

Date Modified:	2011-01-17 13:34:21
Date Created:	2009-10-02 12:45:13