主题：求解 为什么历史测试成交里面没有开空单

IF BS_DIR = 1 THEN BEGIN                                                                                                                                                                                                                        sellshort(holding<0,0,market);                   
        BUY(HOLDING = 0, 1, MARKET);                                                                                                                                                                                                                                   
        BS_DIR := 0;                                                                                                                                                                                                                                                   
    END;                                                                                                                                                                                                                                                               
    IF BS_DIR = -1 THEN BEGIN                                                                                                                                                                                                                   sell(holding>0,0,market);                       
        BUYSHORT(HOLDING = 0, -1, MARKET);                                                                                                                                                                                                                             
        BS_DIR := 0;                                                                                                                                                                                                                                                   
    END;                                                                                                               

END;