help determining whether a variable exists

[Tom]

---

@Shmuel wrote:

@Tom may I ask, suppose you have a macro program in a macro program:

/* %let choice = xxx; -- either exists as global or does not exits */

%macro main;
   %local choise;
    ...
    %called(....);
   ...
%mend;

%macro called(...arguments ...);
    %global choice;
     %if  %symexist(choice) %then ... ;
%mend;

%main;
      

in such case which macro variable CHOICE shall %symexist() check - the %local or the %global ?

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So that is the combination will generate an error message. When the sub-macro CALLED starts and tries to create a global symbol named CHOICE it will issue an error message since CHOICE already exists in the symbol table for the MAIN macro.

We are essentially trying to deal with what I call "external" macro variables.  They are not defined as parameters to the macro or defined as local macro variables that the macro uses for its own purpose.  The reference to them just seems to appear in the code and how they are supposed to have ever gotten assigned a value is magic of some type. 

Here is the general pattern I would follow.

1) Test if the macro variable exists or not and then create it in the appropriate scope.

2) Test if the macro variable is populated or not and if appropriate assign it a default value (or take appropriate action for when the value is empty.).

%macro called(...arguments ...);
    %if not %symexist(choice) %then %local choice;
    %if 0=%length(%superq(choice)) %then ... ;
     ...
%mend;

[Shmuel]

Thanks @Tom , you absolutely clarified the point.

[DanD999]

Thanks to everyone for their help. I wasn't able to get the code to work like I wanted so I changed other parts of the code to solve the problem. 

Thanks again

[Prashanth_J]

Hey..

It pretty much simple.

data check_var;

dsname=open("sashelp.class");

varname_=varnum(dsname,'AGE');

if varname_ >0 then flag="Y"; else flag="N";

/* if flag="Y";*/

run;

** If you want to create a macro then use the below code .

data _NULL_;
call symputx("Checkv", varnum(open("sashelp.class"),'AGE'));
run;
%put &Checkv.;