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Docs/Samples/SymbolInfoDouble.md

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+# SymbolInfoDouble
+
+[Reference](https://docs.mql4.com/marketinformation/symbolinfodouble);
+
+Returns the corresponding property of a specified symbol. There are 2 variants of the function.
+
+1. Immediately returns the property value.
+
+```mq4
+double  SymbolInfoDouble(
+   string                   name,       // symbol
+   ENUM_SYMBOL_INFO_DOUBLE  prop_id     // identifier of the property
+   );
+```
+
+2. Returns true or false depending on whether a function is successfully performed. In case of success, the value of the property is placed into a recipient variable, passed by reference by the last parameter.
+
+```mq4
+bool  SymbolInfoDouble(
+   string                   name,       // symbol
+   ENUM_SYMBOL_INFO_DOUBLE  prop_id,    // identifier of the property
+   double&                  double_var  // here we accept the property value
+   );
+```
+
+Parameters
+
+name
+
+[in] Symbol name.
+
+prop_id
+
+[in] Identifier of a symbol property. The value can be one of the values of the ENUM_SYMBOL_INFO_DOUBLE enumeration.
+
+double_var
+
+[out] Variable of double type receiving the value of the requested property.
+
+Return Value
+
+The value of double type. In case of execution failure, information about the error can be obtained using GetLastError() function:
+
+4106 — symbol is not selected in "Market Watch" (not found in the list of available ones),
+4051 — invalid identifier of a symbol property,
+4024 — internal error.
+Note
+
+It is recommended to use SymbolInfoTick() if the function is used for getting information about the last tick. It may well be that not a single quote has appeared yet since the terminal is connected to a trading account. In such a case, the requested value will be indefinite.
+
+In most cases, it is enough to use SymbolInfoTick() function allowing a user to receive the values of Ask, Bid, Last, Volume and the time of the last tick's arrival during a single call.
+
+Example:
+
+```mq4
+void OnTick()
+  {
+//--- obtain spread from the symbol properties
+   bool spreadfloat=SymbolInfoInteger(Symbol(),SYMBOL_SPREAD_FLOAT);
+   string comm=StringFormat("Spread %s = %I64d points\r\n",
+                            spreadfloat?"floating":"fixed",
+                            SymbolInfoInteger(Symbol(),SYMBOL_SPREAD));
+//--- now let's calculate the spread by ourselves
+   double ask=SymbolInfoDouble(Symbol(),SYMBOL_ASK);
+   double bid=SymbolInfoDouble(Symbol(),SYMBOL_BID);
+   double spread=ask-bid;
+   int spread_points=(int)MathRound(spread/SymbolInfoDouble(Symbol(),SYMBOL_POINT));
+   comm=comm+"Calculated spread = "+(string)spread_points+" points";
+   Comment(comm);
+  }
+```