條件邏輯與運算子

//+------------------------------------------------------------------+
//| Lesson 6 - Pre-trade validation gate                             |
//+------------------------------------------------------------------+
#property copyright "Strategist Academy"
#property version   "1.00"

void OnStart()
{
   string sym   = _Symbol;
   double ask   = SymbolInfoDouble(sym, SYMBOL_ASK);
   double bid   = SymbolInfoDouble(sym, SYMBOL_BID);
   double point = _Point;

   long   stopsLevel = SymbolInfoInteger(sym, SYMBOL_TRADE_STOPS_LEVEL);
   long   tradeMode  = SymbolInfoInteger(sym, SYMBOL_TRADE_MODE);

   double spreadPoints = (ask - bid) / point;
   double stopPts      = 200;          // candidate stop distance in points
   double maxSpread    = 20;           // our own tolerance

   bool spreadOk = (spreadPoints <= maxSpread);
   bool stopOk   = (stopPts >= (double)stopsLevel);
   bool modeOk   = (tradeMode == SYMBOL_TRADE_MODE_FULL);

   Print("Symbol:        ", sym);
   Print("Spread:        ", DoubleToString(spreadPoints, 1), " points (limit ", maxSpread, ")  ok=", spreadOk ? "YES" : "NO");
   Print("Stop distance: ", DoubleToString(stopPts, 0), " points (broker min ", stopsLevel, ")  ok=", stopOk ? "YES" : "NO");
   Print("Trade mode:    ", EnumToString((ENUM_SYMBOL_TRADE_MODE)tradeMode), "  ok=", modeOk ? "YES" : "NO");

   if(spreadOk && stopOk && modeOk)
      Print("RESULT: all pre-trade checks passed - safe to send.");
   else if(!modeOk)
      Print("RESULT: symbol is not fully tradable right now (session or broker restriction).");
   else if(!spreadOk)
      Print("RESULT: spread too wide - skip this entry, it is not worth the cost.");
   else
      Print("RESULT: stop too close - the broker would reject this with invalid stops.");

   // --- float comparison ----------------------------------------------
   double a = 0.1 + 0.2;
   Print("");
   Print("0.1 + 0.2 == 0.3 ?        ", (a == 0.3) ? "true" : "false   <-- never compare doubles");
   Print("with 1e-6 tolerance:      ", (MathAbs(a - 0.3) < 0.000001) ? "true" : "false");
}