参考了之前jinzhe的代码，写了一个判断主力合约的代码：
//判断主力合约，作为走势判断依据
v0:=callstock('if00',vtopenint,6,-1);
v1:=callstock('if01',vtopenint,6,-1);
v2:=callstock('if02',vtopenint,6,-1);
v3:=callstock('if03',vtopenint,6,-1);
v4:=callstock('if04',vtopenint,6,-1);
v5:=callstock('if05',vtopenint,6,-1);
v6:=callstock('if06',vtopenint,6,-1);
v7:=callstock('if07',vtopenint,6,-1);
v8:=callstock('if08',vtopenint,6,-1);
v9:=callstock('if09',vtopenint,6,-1);
v10:=callstock('if10',vtopenint,6,-1);
v11:=callstock('if11',vtopenint,6,-1);
v12:=callstock('if12',vtopenint,6,-1);
nn:=if(v1>v12*0.85 and v1>v0*0.85 and v1>v2,'IF01',if(v2>v1*0.85 and v2>v0*0.85 and v2>v3,'IF02',if(v3>v2*0.85 and v3>v0*0.85 and v3>v4,'IF03',if(v4>v3*0.85 and v4>v0*0.85 and v4>v5,'IF04',if(v5>v4*0.85 and v5>v0*0.85 and v5>v6,'IF05',if(v6>v5*0.85 and v6>v0*0.85 and v6>v7,'IF06',if(v7>v6*0.85 and v7>v0*0.85 and v7>v8,'IF07',if(v8>v7*0.85 and v8>v0*0.85 and v8>v9,'IF08',if(v9>v8*0.85 and v9>v0*0.85 and v9>v10,'IF09',if(v10>v9*0.85 and v10>v0*0.85 and v10>v11,'IF10',if(v11>v10*0.85 and v11>v0*0.85 and v11>v12,'IF11',if(v12>v11*0.85 and v12>v0*0.85 and v12>v1,'IF12','IF00'))))))))))));
原理就是用昨日收盘持仓量来判断，持仓量最大的或下一月份持仓量即将超过本月持仓量时，就选取为主力合约。
nn就是主力合约的代码。可以用来在公式里面用callstock等函数来分析，一般用持仓量最大的主力合约来作交易信号分析比较有效，因为主力和约持仓量交易量都大，一般不容易出现小概率的极端行情。