/************************************************************
 * evaluate a string as an expression
 *
 * Peng Zeng (Auburn University)
 * 10-16-2018
 ************************************************************/

data mydata;
   input x $;
datalines;
1+2
3>2
;

proc print data = mydata; run;

proc contents data = mydata; run;

data updated;
   set mydata;
   y_char = resolve(cats('%sysevalf(', x, ')'));
   y_num = input(y_char, 12.);
run;

proc print data = updated; run;

proc contents data = updated; run;

/* in proc sql */

data mydata2;
   input x $;
datalines;
3>2
1<2
4=5
5<2
4>9
1
2
0
.
;

proc print data = mydata2; run;

proc sql;
   select *, 
      case missing(x) 
         when 1 then 1 
         else input(resolve(cats('%sysevalf(', x, ')')), 12.) 
      end as condition
   from mydata2
   where (calculated condition) > 0;
quit;