Date:         Thu, 30 Oct 2008 17:18:06 -0400
Reply-To:     "Howard Schreier <hs AT dc-sug DOT org>"
              <schreier.junk.mail@GMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         "Howard Schreier <hs AT dc-sug DOT org>"
              <schreier.junk.mail@GMAIL.COM>
Subject:      Re: Test if a var is available inside data step?

On Thu, 30 Oct 2008 14:52:58 -0400, Ya Huang <ya.huang@AMYLIN.COM> wrote:

>Hi there,
>
>%macro cat(v1=,v2=,v3=);
>&v3=trim(&v1)||trim(&v2);
>%mend cat;
>
>
>*first call is OK;
>data xx;
> set sashelp.class (obs=1);
>%cat(v1=sex,v2=name,v3=sname);
>run;
>
>proc print;
>run;
>
>*second call failed, because name is not available;
>data yy;
> set sashelp.class (obs=1 drop=name);
>%cat(v1=sex,v2=name,v3=sname);
>run;
>
>proc print;
>run;
>
>What I want is somehow add test in the macro, so that if v2
>is not available, then switch to
>
>&v3=trim(&v1)||trim(&v2);
>to
>&v3=trim(&v1);
>
>The message like "NOTE: Variable name is uninitialized" should
>be avoided too.
>
>Thanks
>
>Ya

Try

   &v3=trim(&v1)||trim( vvaluex("&v3") );