有朋友可以告诉下HASH object初始化后添加CALL missing routine有什么作用！还有以下一个小程序
data c;
length t 4;
length tt 4;
if _n_=1 then do;
declare hash h(hashexp:4,order:'a');
rc=h.definekey("t");
rc=h.definedata('t','tt');
rc=h.definedone();
call missing(t,tt);
end;
t=1;
tt=2;
rc=h.add();
if (rc=0) then output;
else put "add failed";
t=3;
tt=4;
rc=h.add();
if (rc ne 0) then put "add failed";
t=5;
tt=6;
rc=h.add();
if (rc eq 0) then put "add successed";
t=3;
rc=h.find();
if (rc eq 0) then put "tt=";
else put "t=3 is not found";
t=9;
rc=h.find();
if (rc eq 0) then put "tt=";
else put "t=9 is not found";
rc=h.output(dataset:"x");
run;
proc print data=x;
run;得出的DATA-SET  X中的各条记录为什么没有按顺序排列！
望高手指点。谢谢！！