为何提示不允许是-1

 死叉:=CROSS(DEA,DIF);
N1:=BARSLAST(死叉),NODRAW;
N2:=REF(BARSLAST(死叉),N1+1),NODRAW;
N3:=REF(BARSLAST(死叉),N2+N1+2),NODRAW;
CL1:=LLV(C,N1+1),NODRAW;
DIFL1:=LLV(DIF,N1+1),NODRAW;

CL2:=REF(CL1,N1+1),NODRAW;
DIFL2:=REF(DIFL1,N1+1),NODRAW;
CL3:=REF(CL2,N1+1),NODRAW;
DIFL3:=REF(DIFL2,N1+1),NODRAW;
PDIFL2:=IF(DIFL2>0,INTPART(LOG(DIFL2))-1,INTPART(LOG(-DIFL2))-1);

老师上面公式为何软件提示如下：

第16行 'IFL2'面不允许是'1'

 来源:程序化99