sas call sortc 函数

data a; 
input x$ y$ @@; 
cards; 
a b
c d 
b a 
d c 
a b ; 
data b; 
set a; 
call sortc(x,y);
proc sort data = b out = c nodupkey;
by x y;
/*proc sql;
create table c 
as select distinct x,y from b;
quit;*/ 
proc print; run; 

/*
data b;
set a;
if x > y then z = x||y;
else z = y ||x;
run;
proc sort data = b out = c nodupkey;
by z;
proc print;
run; 
*/

call sortc;

call sortn;