编写的一套系统，想要测试，可弹出对话框说信号是有的，但是都无法成交，请问会是什么原因呢？谢谢！代码如下：
a1:=ref(high,1);
a2:=ref(low,1);
a3:high>a1 and low<a2 and close>a1;
a4:high>a1 and low<a2 and close<a2;
a5:time>010500 and time<185000;
if a5 and holding<=0 and a3 then begin
buy(1,1,close);
end
if a5 and holding>=0 and a4 then begin
buyshort(1,1,close);
end
if time>=185500 and holding<>0 then begin
sell(holding>0,0,close);
sellshort(holding<0,0,close);
end