【MQL4】パラボリックSARをトレーリングストップに使うEAの作り方｜損切りは『近づける』方向にしか動かさない設計

//+------------------------------------------------------------------+
//|                                    SarTrailingStopEA.mq4          |
//|                     Copyright 2026, FX-EA System Project Creator |
//|                        https://creator.fx-ea-system-project.com/ |
//+------------------------------------------------------------------+
#property copyright "Copyright 2026, FX-EA System Project Creator"
#property link      "https://creator.fx-ea-system-project.com/"
#property version   "1.00"
#property strict

input int    MagicNumber = 45678;//マジックナンバー
input double Lots        = 0.01;//ロット数
input int    TakeProfit  = 100;//利確(pips、0で利確なし)
input int    Slippage    = 3;//スリッページ
input double SarStep     = 0.02;//SARの加速係数の増分
input double SarMaximum  = 0.2;//SARの加速係数の最大値

//+------------------------------------------------------------------+
//| このEA(マジックナンバー)の保有チケットを返す(なければ-1)          |
//+------------------------------------------------------------------+
int GetMyTicket()
  {
   for(int i=OrdersTotal()-1; i>=0; i--)
     {
      if(!OrderSelect(i,SELECT_BY_POS,MODE_TRADES)) continue;
      if(OrderSymbol()==Symbol() && OrderMagicNumber()==MagicNumber)
         return(OrderTicket());
     }
   return(-1);
  }

//+------------------------------------------------------------------+
//| shift本前の足でSARが上昇転換したか(価格の上→下へ移動)             |
//+------------------------------------------------------------------+
bool SarFlippedBullish(int shift)
  {
   double sarNow  = iSAR(NULL,0,SarStep,SarMaximum,shift);
   double sarPrev = iSAR(NULL,0,SarStep,SarMaximum,shift+1);
   double closeNow  = iClose(NULL,0,shift);
   double closePrev = iClose(NULL,0,shift+1);

   return(sarPrev > closePrev && sarNow < closeNow);
  }

//+------------------------------------------------------------------+
//| shift本前の足でSARが下降転換したか(価格の下→上へ移動)             |
//+------------------------------------------------------------------+
bool SarFlippedBearish(int shift)
  {
   double sarNow  = iSAR(NULL,0,SarStep,SarMaximum,shift);
   double sarPrev = iSAR(NULL,0,SarStep,SarMaximum,shift+1);
   double closeNow  = iClose(NULL,0,shift);
   double closePrev = iClose(NULL,0,shift+1);

   return(sarPrev < closePrev && sarNow > closeNow);
  }

//+------------------------------------------------------------------+
//| 保有中のポジションをSARの現在値でトレーリングする(近づける方向のみ) |
//+------------------------------------------------------------------+
void TrailStopWithSAR(int ticket)
  {
   if(!OrderSelect(ticket,SELECT_BY_TICKET)) return;

   double sarLive = iSAR(NULL,0,SarStep,SarMaximum,0);
   double minDistance = MarketInfo(Symbol(),MODE_STOPLEVEL)*Point;

   if(OrderType()==OP_BUY)
     {
      bool improves   = (sarLive > OrderStopLoss());
      bool farEnough  = (Bid - sarLive >= minDistance);

      if(improves && farEnough)
         if(!OrderModify(ticket,OrderOpenPrice(),sarLive,OrderTakeProfit(),0,clrLimeGreen))
            Print("買いポジションのSL更新に失敗しました。エラーコード=",GetLastError());
     }

   if(OrderType()==OP_SELL)
     {
      bool improves   = (sarLive < OrderStopLoss());
      bool farEnough  = (sarLive - Ask >= minDistance);

      if(improves && farEnough)
         if(!OrderModify(ticket,OrderOpenPrice(),sarLive,OrderTakeProfit(),0,clrTomato))
            Print("売りポジションのSL更新に失敗しました。エラーコード=",GetLastError());
     }
  }

//+------------------------------------------------------------------+
//| Expert initialization function                                   |
//+------------------------------------------------------------------+
int OnInit()
  {
   return(INIT_SUCCEEDED);
  }
//+------------------------------------------------------------------+
//| Expert deinitialization function                                 |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
  {
  }
//+------------------------------------------------------------------+
//| Expert tick function                                             |
//+------------------------------------------------------------------+
void OnTick()
  {
   int ticket = GetMyTicket();

   if(ticket < 0)
     {
      int shift = 1;//直近の確定足で判定する

      if(SarFlippedBullish(shift))
        {
         double sl = iSAR(NULL,0,SarStep,SarMaximum,shift);
         double tp = (TakeProfit>0) ? Ask+TakeProfit*Point*10 : 0;
         int result = OrderSend(Symbol(),OP_BUY,Lots,Ask,Slippage,sl,tp,"SAR Trail Buy",MagicNumber,0,Blue);
         if(result < 0)
            Print("買い注文に失敗しました。エラーコード=",GetLastError());
        }

      if(SarFlippedBearish(shift))
        {
         double sl = iSAR(NULL,0,SarStep,SarMaximum,shift);
         double tp = (TakeProfit>0) ? Bid-TakeProfit*Point*10 : 0;
         int result = OrderSend(Symbol(),OP_SELL,Lots,Bid,Slippage,sl,tp,"SAR Trail Sell",MagicNumber,0,Red);
         if(result < 0)
            Print("売り注文に失敗しました。エラーコード=",GetLastError());
        }
     }
   else
     {
      TrailStopWithSAR(ticket);
     }
  }
//+------------------------------------------------------------------+