关于MT4自带的EA--Moving Average问题

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有几个关于该EA的问题，请各朋友指点：
1. 在自定义函数CalculateCurrentOrders()中，形参symbol并没有在函数中被应用，为何还需要定义该参数？
2. 在自定义函数CalculateCurrentOrders()中，最后一个return返回-sells，为何不是直接返回sells？
3. 在自定义函数LotsOptimized()中，lot=NormalizeDouble(AccountFreeMargin()*MaximumRisk/1000.0,1);为何要除以1000？

Thanks a lot!

P.S.

订单的ticket number和magic number有什么区别?

iMA中的ma_shift是什么意思?

//+------------------------------------------------------------------+
//| Moving Average.mq4 |
//| Copyright ?2005, MetaQuotes Software Corp. |
//| https://www.metaquotes.net// |
//+------------------------------------------------------------------+
#define MAGICMA 20050610

extern double Lots = 0.1;
extern double MaximumRisk = 0.02;
extern double DecreaseFactor = 3;
extern double MovingPeriod = 12;
extern double MovingShift = 6;
//+------------------------------------------------------------------+
//| Calculate open positions |
//+------------------------------------------------------------------+
int CalculateCurrentOrders(string symbol)
{
int buys=0,sells=0;
//----
for(int i=0;i<OrdersTotal();i++)
{
if(OrderSelect(i,SELECT_BY_POS,MODE_TRADES)==false) break;
if(OrderSymbol()==Symbol() && OrderMagicNumber()==MAGICMA)
{
if(OrderType()==OP_BUY) buys++;
if(OrderType()==OP_SELL) sells++;
}
}
//---- return orders volume
if(buys>0) return(buys);
else return(-sells);
}
//+------------------------------------------------------------------+
//| Calculate optimal lot size |
//+------------------------------------------------------------------+
double LotsOptimized()
{
double lot=Lots;
int orders=OrdersHistoryTotal(); // history orders total
int losses=0; // number of losses orders without a break
//---- select lot size
lot=NormalizeDouble(AccountFreeMargin()*MaximumRisk/1000.0,1);
//---- calculate number of losses orders without a break
if(DecreaseFactor>0)
{
for(int i=orders-1;i>=0;i--)
{
if(OrderSelect(i,SELECT_BY_POS,MODE_HISTORY)==false) { Print("Error in history!"); break; }
if(OrderSymbol()!=Symbol() || OrderType()>OP_SELL) continue;
//----
if(OrderProfit()>0) break;
if(OrderProfit()<0) losses++;
}
if(losses>1) lot=NormalizeDouble(lot-lot*losses/DecreaseFactor,1);
}
//---- return lot size
if(lot<0.1) lot=0.1;
return(lot);
}
//+------------------------------------------------------------------+
//| Check for open order conditions |
//+------------------------------------------------------------------+
void CheckForOpen()
{
double ma;
int res;
//---- go trading only for first tick of new bar
if(Volume[0]>1) return;
//---- get Moving Average
ma=iMA(NULL,0,MovingPeriod,MovingShift,MODE_SMA,PRICE_CLOSE,0);
//---- sell conditions
if(Open[1]>ma && Close[1]<ma)
{
res=OrderSend(Symbol(),OP_SELL,LotsOptimized(),Bid,3,0,0,"",MAGICMA,0,Red);
return;
}
//---- buy conditions
if(Open[1]<ma && Close[1]>ma)
{
res=OrderSend(Symbol(),OP_BUY,LotsOptimized(),Ask,3,0,0,"",MAGICMA,0,Blue);
return;
}
//----
}
//+------------------------------------------------------------------+
//| Check for close order conditions |
//+------------------------------------------------------------------+
void CheckForClose()
{
double ma;
//---- go trading only for first tiks of new bar
if(Volume[0]>1) return;
//---- get Moving Average
ma=iMA(NULL,0,MovingPeriod,MovingShift,MODE_SMA,PRICE_CLOSE,0);
//----
for(int i=0;i<OrdersTotal();i++)
{
if(OrderSelect(i,SELECT_BY_POS,MODE_TRADES)==false) break;
if(OrderMagicNumber()!=MAGICMA || OrderSymbol()!=Symbol()) continue;
//---- check order type
if(OrderType()==OP_BUY)
{
if(Open[1]>ma && Close[1]<ma) OrderClose(OrderTicket(),OrderLots(),Bid,3,White);
break;
}
if(OrderType()==OP_SELL)
{
if(Open[1]<ma && Close[1]>ma) OrderClose(OrderTicket(),OrderLots(),Ask,3,White);
break;
}
}
//----
}
//+------------------------------------------------------------------+
//| Start function |
//+------------------------------------------------------------------+
void start()
{
//---- check for history and trading
if(Bars<100 || IsTradeAllowed()==false) return;
//---- calculate open orders by current symbol
if(CalculateCurrentOrders(Symbol())==0) CheckForOpen();
else CheckForClose();
//----
}
//+------------------------------------------------------------------+