topic Re: "ERROR: Required operator not found in expression" when testing for null in SAS Programming

"ERROR: Required operator not found in expression" when testing for null

deleted_user — Wed, 23 Sep 2009 20:59:31 GMT

Hello!

I suspect this problem has something to do with when the variable is being resolved, but I'm not sure how to solve it...

Here's a sample of the code I'm using:

********
%macro test(exlimitint);

%if &exlimitint= %then
%do;
%put variable is null;
%end;

%else
%do;
%put &exlimitint.;
%end;

%mend test;
***********

If I run this with a null value, it works fine. For example:

*********
%let exlimitint=;

%test(&exlimitint);
***********

...produces the following log

MLOGIC(TEST): Beginning execution.
SYMBOLGEN: Macro variable EXLIMITINT resolves to
MLOGIC(TEST): Parameter EXLIMITINT has value
SYMBOLGEN: Macro variable EXLIMITINT resolves to
MLOGIC(TEST): %IF condition &exlimitint= is TRUE
MLOGIC(TEST): %PUT variable is null
variable is null
MLOGIC(TEST): Ending execution.

If I run it with a the variable set to a simple value, it works fine. Like so...

***********
%let exlimitint=x;

%test(&exlimitint);
***********

...results in:

MLOGIC(TEST): Beginning execution.
SYMBOLGEN: Macro variable EXLIMITINT resolves to x
MLOGIC(TEST): Parameter EXLIMITINT has value x
SYMBOLGEN: Macro variable EXLIMITINT resolves to x
MLOGIC(TEST): %IF condition &exlimitint= is FALSE
MLOGIC(TEST): %PUT &exlimitint.
SYMBOLGEN: Macro variable EXLIMITINT resolves to x
x
MLOGIC(TEST): Ending execution.

However, if I try to set the variable to a value that contains a put statement (which is what I actually need), it bombs.

*********
%let exlimitint=if put(x,$intfmt)='FMT VALUE';

%test(&exlimitint);
*********

MLOGIC(TEST): Beginning execution.
SYMBOLGEN: Macro variable EXLIMITINT resolves to if put(x,$intfmt)='FMT VALUE'
MLOGIC(TEST): Parameter EXLIMITINT has value if put(x,$intfmt)='FMT VALUE'
SYMBOLGEN: Macro variable EXLIMITINT resolves to if put(x,$intfmt)='FMT VALUE'
ERROR: Required operator not found in expression: &exlimitint=
ERROR: The macro TEST will stop executing.
MLOGIC(TEST): Ending execution.

Thoughts, anyone?

Thanks!!!
Emily

Re: "ERROR: Required operator not found in expression" when testing for null

Cynthia_sas — Wed, 23 Sep 2009 22:33:13 GMT

Hi:
Generally, folks don't pass whole IF statements in a %LET. Although it is possible to do, usually, you want to -do- something if a macro variable exists. Well, what is the thing you want to do?? Usually, it is some kind of conditional process, procedure or data step (or piece of data step program.)

I see that as one issue. Then there's the fact that you're passing an IF statement to a macro program and the IF statement will be hanging out in open code, unless you haven't shown the whole program. You can only use an IF statement inside a DATA step program. Don't confuse a data step IF with a macro logic %IF.

But, assuming that you haven't shown us all the code, and you are hiding a data step program someplace, I would expect to see a quoting function like %STR or %NRSTR being used to protect the IF statement snippet.

Even if you DO have a data step program, however, your PUT statement is incorrect. The FORMAT is missing a '.' -- it should be $INTFMT. (your syntax is missing the period. Also, the rest of your code will need to have the rest of the IF statement -- including the action to take on the TRUE and the closing semi-colon.

One rule of thumb for macro processing is to start with a working SAS program and then macro-ize the working program. I don't see that you have a working SAS program that can be macro-ized -- where is the rest of your IF statement going to be?? It seems to me that you want to do some kind of error checking -- which is a good thing, but I'd expect to see something like what's shown at the bottom of this posting -- I made up a program to show the difference between a macro %IF and a data step IF.

In my program, I show the %IF controllling whether an entire data step program would be run. Alternately, I could have coded the %IF -inside- the DATA step program, but generally error checking and issuing messages in the log is something that's done before a major process starts because if you don't have all of your macro variables with values, you might not want to go forward with the data step program.

cynthia

[pre]
%macro test(exlimitint);

%if &exlimitint= %then %do;
%put -------***** EXLIMITINT macro variable is null;
%end;
%else %if %upcase(&exlimitint) ne SEX %then %do;
%put -------***** You can only ask for the SEX variable;
%end;
%else %if %upcase(&exlimitint) eq SEX %then %do;
proc format;
value $intfmt 'M' = 'FMT VALUE'
'F' = 'XXXXXXXXX';
run;

data new;
set sashelp.class;
newvar = put(&exlimitint,$intfmt.);
if put(&exlimitint,$intfmt.)='FMT VALUE'
then output;
run;

ods listing;
proc print data=new noobs;
title 'Correct macro var and condition';
title2 "Value of EXLIMITINT macro var is: &EXLIMITINT";
run;

%end;

%mend test;

options nodate nonumber center;
** invoke with null;
%test()

** invoke with SEX (since program uses SASHELP.CLASS);
%test(sex)

** invoke with NAME -- not what program is coded for;
%test(name)
[/pre]

Re: "ERROR: Required operator not found in expression" when testing for null

sbb — Wed, 23 Sep 2009 23:41:26 GMT

I do this all the time with SAS - using SAS macro variables as code exit-points but you need to surround your macro variable using %QUOTE (* your code goes here;);

Also, I encourage you to code your macro language %IF %THEN %-whatever-; statements so that there is never an unbalanced condition with the operator -- for readability I choose to use the . (period) character. Another technique if you are checking for a zero-length is to use the %LENGTH(&macrovar) and then do some logic accordingly.

And in some unique cases, you will need to call upon some of the more complex macro language functions for resolution. So I suggest you get familiar with the ins/outs of macro function and make extensive use of the most-valuable forum resources like Cynthia but more importantly get used to checking the SAS Support http://support.sas.com/ website for SAS-hosted DOC and supplemental technical and conference topic-related reference material.

Scott Barry
SBBWorks, Inc.