Expert Advisor Programming by Andrew R. Young

EXPERT ADVISOR PROGRAMMING
from M1 data. The trades that occur in live trading will not necessarily correspond to trade made in
the Strategy Tester.
But by placing our trades on the close on the bar and using "Open prices only" as the testing model,
we can get testing results that more accurately reflect real-time trades. The disadvantage of trading
once per bar is that trades may be executed late, especially if there is a lot of price movement over
the course of the bar. It's basically a trade-off between responsiveness and reliability.
To check the trade conditions once per bar, we must examine the time stamp of the current bar. We
will save this time stamp to a global variable. Upon each execution of the expert advisor, we will
compare the saved time stamp to the current time stamp. Once the time stamp of the current bar
changes, indicating that a new bar has opened, we will then check the trading conditions.
We must also adjust the shift parameter of our indicator functions, price functions and arrays to
return the value of the previous bar. If an indicator function or price array is set to check the current
bar, we will shift the bar index by 1 to check the previous bar instead. All indicators and price arrays
must have their shift parameters incremented by 1.
Technically, we are checking trading conditions on the first tick of a new bar, while examining the
closing value of the previous bar. We do not check the currently opened bar when executing once per
bar.
Here is the code to check for the opening of a new bar. First, we declare an external variable named
CheckOncePerBar to turn this feature on and off. Then we declare a datetime global variable to
store the time stamp of the current bar – this will be CurrentTimeStamp.
In the init() function, we will assign the time stamp of the current bar to CurrentTimeStamp. This
will delay the trade condition check until the opening of the next bar:
// External variables
extern bool CheckOncePerBar = true;
// Global variables
datetime CurrentTimeStamp;
// Init function
int init()
{
CurrentTimeStamp = Time[0];
}
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