函式、include 與標準函式庫

//+------------------------------------------------------------------+
//| Lesson 8 - Reusable helpers and the standard library             |
//+------------------------------------------------------------------+
#property copyright "Strategist Academy"
#property version   "1.00"

#include <Trade/Trade.mqh>

//+------------------------------------------------------------------+
//| Round a volume to what the broker actually accepts               |
//+------------------------------------------------------------------+
double NormalizeVolumeFor(const string sym, double vol)
{
   double vMin  = SymbolInfoDouble(sym, SYMBOL_VOLUME_MIN);
   double vMax  = SymbolInfoDouble(sym, SYMBOL_VOLUME_MAX);
   double vStep = SymbolInfoDouble(sym, SYMBOL_VOLUME_STEP);

   vol = MathMax(vMin, MathMin(vMax, vol));

   if(vStep > 0)
      vol = vMin + MathFloor((vol - vMin) / vStep + 0.0000001) * vStep;

   return NormalizeDouble(vol, 2);
}

//+------------------------------------------------------------------+
//| Convert a distance in points into an absolute price              |
//+------------------------------------------------------------------+
double PointsToPrice(const double points, const double fromPrice, const bool below)
{
   double offset = points * _Point;
   return below ? NormalizeDouble(fromPrice - offset, _Digits)
                : NormalizeDouble(fromPrice + offset, _Digits);
}

//+------------------------------------------------------------------+
//| Is there already a position opened by this magic number?         |
//+------------------------------------------------------------------+
bool HasPosition(const string sym, const ulong magic)
{
   if(!PositionSelect(sym))
      return false;
   return ((ulong)PositionGetInteger(POSITION_MAGIC) == magic);
}

void OnStart()
{
   string sym = _Symbol;

   Print("Volume normalisation on ", sym);
   Print("  0.137  -> ", DoubleToString(NormalizeVolumeFor(sym, 0.137), 2));
   Print("  1.005  -> ", DoubleToString(NormalizeVolumeFor(sym, 1.005), 2));
   Print("  999.0  -> ", DoubleToString(NormalizeVolumeFor(sym, 999.0), 2), "  (clamped to max)");

   double bid = SymbolInfoDouble(sym, SYMBOL_BID);
   double ask = SymbolInfoDouble(sym, SYMBOL_ASK);

   Print("Stop 200 points below bid: ", DoubleToString(PointsToPrice(200, bid, true),  _Digits));
   Print("Target 400 points above ask: ", DoubleToString(PointsToPrice(400, ask, false), _Digits));

   Print("Has position with magic 12345? ", HasPosition(sym, 12345) ? "yes" : "no");

   // CTrade is ready to use - Part 3 will actually send orders with it.
   CTrade trade;
   trade.SetExpertMagicNumber(12345);
   trade.SetDeviationInPoints(10);
   trade.SetTypeFillingBySymbol(sym);
   Print("CTrade configured. Filling mode selected by symbol: ",
         EnumToString((ENUM_ORDER_TYPE_FILLING)SymbolInfoInteger(sym, SYMBOL_FILLING_MODE)));
}