topic Re: Macro isBlank never returns a true condition. in SAS Studio

Macro isBlank never returns a true condition.

chinli72 — Sat, 06 Oct 2018 21:09:52 GMT

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. */

Re: Macro isBlank never returns a true condition.

PaigeMiller — Sat, 06 Oct 2018 21:16:16 GMT

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.

%let a=XXX;

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

%let a=;

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

Re: Macro isBlank never returns a true condition.

Astounding — Sat, 06 Oct 2018 21:30:46 GMT

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.

Re: Macro isBlank never returns a true condition.

chinli72 — Sat, 06 Oct 2018 21:35:35 GMT

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

Re: Macro isBlank never returns a true condition.

chinli72 — Sat, 06 Oct 2018 21:39:48 GMT

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

Re: Macro isBlank never returns a true condition.

chinli72 — Sat, 06 Oct 2018 21:43:00 GMT

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

Re: Macro isBlank never returns a true condition.

Astounding — Sat, 06 Oct 2018 21:52:04 GMT

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.

Re: Macro isBlank never returns a true condition.

chinli72 — Sat, 06 Oct 2018 21:55:34 GMT

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

Re: Macro isBlank never returns a true condition.

Ksharp — Sun, 07 Oct 2018 10:36:28 GMT

Calling @data_null__

Re: Macro isBlank never returns a true condition.

PaigeMiller — Sun, 07 Oct 2018 10:57:05 GMT

@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 */

Re: Macro isBlank never returns a true condition.

chinli72 — Mon, 08 Oct 2018 13:24:11 GMT

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.

Re: Macro isBlank never returns a true condition.

Ksharp — Mon, 08 Oct 2018 13:31:49 GMT

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

I mentioned him here to let him notice this question .

Re: Macro isBlank never returns a true condition.

chinli72 — Mon, 08 Oct 2018 18:16:13 GMT

Got it. Thank you.