topic Re: why %if %then does not work? in SAS Programming

why %if %then does not work?

ZRick — Fri, 06 Apr 2012 13:59:06 GMT

In a macro program, if, then statement, you have to use %if %then

but following macro program it says:

ERROR: Required operator not found in expression: symlocal('c')

ERROR: The macro TEST will stop executing.

Rather, if, then statement works,

I can't wrap my head around it.

%let c=yes;

%macro test;

%let d=yes;

data _null_;

%if symlocal('c') %then %put '**** c a is local';

%else %put '**** c is global';

if symlocal ('d') then put '**** d is local';

else put '**** d is global';

run;

%mend test;

%test

Re: why %if %then does not work?

DonH — Fri, 06 Apr 2012 14:22:13 GMT

Macro is a text processing facility and so you don't quote character strings. Plus it need not run in a data step. See:

%let c=yes;

%macro test;

%let d=yes;

%if %symlocal(c) %then %put **** c a is local;

%else %put **** c is global;

run;

%mend test;

%test

Also note that sumlocal is both a macro function and not a data step function. So you need to use %symlocal when running it as macro code.

If you are new to macro I would suggest that you do a Google search for any papers by Ian Whitlock on the macro facility. His papers do a great job of explaining the background behind why what you tried did not work.

Re: why %if %then does not work?

ZRick — Sat, 07 Apr 2012 04:40:34 GMT

Well, it confuses me because I don't know how to tell if it is macro variable or data step variable.

The example in my question is from: http://www2.sas.com/proceedings/sugi31/107-31.pdf

originally it is written like this:

%let c=yes;

%macro test;

%let d=yes;

data _null_;

if symlocal('c') then put '**** c a is local';

else put '**** c is global';

if symlocal ('d') then put '**** d is local';

else put '**** d is global';

run;

%mend test;

%test

so, you see, c and d are quoted in the symlocal function, and in the macro, %if %then statement are not used but only if then, it confuses me.

Can someone help explain?

Re: why %if %then does not work?

art297 — Sat, 07 Apr 2012 13:08:10 GMT

Actually, unless you changed the original, you had them mixed (i.e., used symlocal once and %symlocal once.

I agree with Don that Ian's papers would be a good way to start. If you are serious about wanting to learn, I have a spreadsheet that contains links to all of his SAS-L posts.

In the meantime, here is a different mixture that all work:

%let c=yes;

%macro test;

%let d=yes;

%if %symlocal(c) %then %put '**** c a is local';

%else %put '**** c is global';

data _null_;

%if %symlocal(c) %then %put '**** c a is local';

%else %put '**** c is global';

if symlocal ('d') then put '**** d is local';

else put '**** d is global';

run;

%mend test;

%test

Re: why %if %then does not work?

ZRick — Sat, 07 Apr 2012 16:24:03 GMT

Hi, Art297,

Can you please share the links you have? I really love to check it out.

Re: why %if %then does not work?

art297 — Sat, 07 Apr 2012 16:41:48 GMT

Send me an email at atabachneck at gmail dot com. I can't post it here because Ian never gave me permission to post it on the web. I wish he would, because there are numerous gold nuggets in those posts.

Re: why %if %then does not work?

Linlin — Sat, 07 Apr 2012 17:21:56 GMT

Are you going to email me too if I ask for it? Thanks - Linlin

Re: why %if %then does not work?

art297 — Sat, 07 Apr 2012 17:29:10 GMT

Sure, just send me an email. I don't have any problem sharing the spreadsheet, I just don't feel comfortable putting it on the web without Ian's permission.

Re: why %if %then does not work?

Linlin — Sat, 07 Apr 2012 17:50:52 GMT

Thank you! I just emailed you. - Linlin

Re: why %if %then does not work?

ZRick — Sat, 07 Apr 2012 19:26:28 GMT

Fantastic, I just sent an email to you, really appreciate your help, Art