/************************************************************
 * check if a macro variable is blank.
 *
 * Peng Zeng (Auburn University)
 * 10-16-2018
 ************************************************************/


/************************************************************
 * macro function to test if a macro variable is blank
 * returns 
 *   1 if the tested macro variable is blank 
 *   0 otherwise 
 * 
 * blank means that the macro variable resolves to a blank 
 * if the macro variable is not defined, return 0
 ************************************************************/
 
%macro isBlank(param);
  %sysevalf(%superq(param)=, boolean)
%mend isBlank;

%let amacro = 123;
%let nullmacro = ;
%let blankmacro = "";

data one;
   a = %isBlank(&amacro);       /* value = 0 */
   b = %isBlank(&nullmacro);    /* value = 1 */
   c = %isBlank(&blankmacro);   /* value = 0 */
   d = %isBlank(&notmacro);     /* value = 0, macro not defined */
run;

proc print data = one; run;