Expert Advisor Programming by Andrew R. Young

EXPERT ADVISOR PROGRAMMING
// Error Handling
if(TicketMod == false)
{
int ErrorCode = GetLastError();
string ErrDesc = ErrorDescription(ErrorCode);
string ErrAlert = StringConcatenate("Add Stop/Profit - Error ",ErrorCode,": ",
ErrDesc);
Alert(ErrAlert);
}
string ErrLog = StringConcatenate("Bid: ",MarketInfo(OrderSymbol(),MODE_BID),
" Ask: ",MarketInfo(OrderSymbol(),MODE_ASK)," Ticket: ",argTicket,
" Stop: ",argStopLoss," Profit: ",argTakeProfit);
Print(ErrLog);
return(TicketMod);
}
We check first to see if either a stop loss or a take profit price has been supplied. If not, we will exit
the function. Otherwise, we will modify the order using the stop loss and take profit that was passed
to the function. The error handling function will run if the order modification was not successful. This
function will work on all order types.
Using Include Files
To keep our functions organized for easy inclusion in our source code files, we'll place the functions
into an include file. An include file can consist of function declarations, imported functions, and any
global or external variables that you wish to include in an expert advisor.
Include files require no special syntax. You declare the functions and variables in the include file just
as you would in any source code file. Include files should not have an init(), start() or deinit()
function. The file must have an .mqh extension and be located in the \experts\include folder.
All of the functions we create in this book will be placed in an include file named
IncludeExample.mqh. The contents of this file are listed in Appendix D.
Using Libraries
A library is a compiled collection of functions. Whereas an include file is a source code file whose
contents are "included" in the executable file, a library is a separate executable that contains the
imported functions. Therefore you must have both your expert advisor executable and the library
executable to run your EA.
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