Macro isBlank never returns a true condition.

[chinli72]

Hi Everyone,

   I've been spending a lot of time on this macro routine and could not figure out what is going on.  In this link, Chung and King presented a macro, isBlank, to test if a macro's argument is blank. In this discussion, Ballardw illustrated a usage of isBlank. However, when I used isBlank in my test macro below, the IF condition is never true. Somehow the 1 returned by %isBlank looks like a 1 but is not really a 1. Would someone help to demystify this please. Thank you very much.

-Chin

%macro isBlank(param);
  %sysevalf(%superq(param)=,boolean);
%mend isBlank;

%put %isBlank(); /* Returns 1. */
%put %isBlank(a); /* Returns 0. */

%macro test(arg);
    %if %isBlank(&arg) = 1 %then %put Blank;   /* This IF is never true.  Is %isBlank(&arg) returning a numerical 1? */
    %else %put Notblank; run;
%mend;

%test();     /* Returns: Notblank  */
%test(a);   /* Returns: Notblank ALSO. */

[PaigeMiller]

The %isblank macro works on macro variables. If you feed it text or a null argument, I have no idea what it will do, but it wasn't designed for that.

So

%let a=XXX;

%put %isblank(&a); /* Should return a 1 */

%let a=;

%put %isblank(&a); /* Should return a 0 */

[chinli72]

PaigeMiller, Thank you for your reply. While I was trying out your suggestion, Astounding replied another solution, which I quickly tested and confirmed that is where my problem is. Thank you for your help.  -Chin

[PaigeMiller]

---

@PaigeMiller wrote:

The %isblank macro works on macro variables. If you feed it text or a null argument, I have no idea what it will do, but it wasn't designed for that.

So

%let a=XXX;

%put %isblank(&a); /* Should return a 1 */

%let a=;

%put %isblank(&a); /* Should return a 0 */

---

Correcting my reply

%let a=XXX;
%put %isblank(&a); /* Should return a 0 */

%let a=;
%put %isblank(&a); /* Should return a 1 */

[Astounding · Accepted solution]

I can't test this right now, but to my eyes, your macro definition is incorrect.  You have an extra semicolon on this line:

 %sysevalf(%superq(param)=,boolean);

"Extra" here means that you have one, but there shouldn't be any.

[chinli72]

Astounding, You are absolutely correct. By removing the ";" in isBlank macro, the code worked. Truly astounded. Thank you very much.

[chinli72]

Are macro's always invoked without a ";" at the end?

[Astounding]

No, ";" is never needed at the end of a macro invocation.  As a result, if you add one, it adds ";" to the program at that point  Much of the time an extra semicolon in the middle of a program doesn't hurt anything.  But in this case, it would.

[chinli72]

I will keep an eye on these ";". Your suggestion has really made my day. Thanks again.

[Ksharp]

Calling @data_null__

[chinli72]

Hi Ksharp,

    Are you suggesting that on the 2nd line, the added ";" 

       %macro isBlank(param) /store source;
           %sysevalf(%superq(param)=,boolean);
       %mend isBlank;

has the effect as 

       %macro isBlank(param) /store source;
           @Data_null_
       %mend isBlank;

calling @data_null__?  

Thank you.

[Ksharp]

This macro is written by John King a.k.a  @data_null__ .

I mentioned him here to let him notice this question .

[chinli72]

Got it. Thank you.