Expert Advisor Programming by Andrew R. Young

EXPERT ADVISOR PROGRAMMING
if((BooleanVar1 == true && Indicator1 > Indicator2) || BooleanVar1 == false)
The statement (BooleanVar1 == true && Indicator1 > Indicator2) is evaluated first. If both
of these conditions are true, the statement evaluates to true, and we are left with an OR operation:
if(true || BooleanVar1 == false)
This statement automatically evaluates to true, since one of the conditions is already true. But what if
(BooleanVar1 == true && Indicator1 > Indicator2) evaluates to false?
if(false || BooleanVar1 == false)
If the condition BooleanVar1 == false evaluates to true, then the entire statement is true. (In
other words, if BooleanVar1 is set to false, that condition evaluates to true.) Otherwise, the
statement is false.
It's possible to create complex boolean operations using AND, OR and parentheses to control the
order of operations. Be sure to watch the locations of your parentheses, as one wrong parenthesis
can cause the statement to evaluate differently, and a missing parenthesis could lead to some tedious
debugging.
Turning An Indicator On and Off
You can use the AND/OR example in the previous section to turn an indicator on and off. Let's say
your EA uses multiple indicators, and you'd like to be able to switch indicators on and off. Here's how
we do it. First, let's declare an external boolean variable to use as the on/off switch. We'll use the
stochastic indicator in this example:
extern bool UseStochastic = true;
We define two sets of conditions for our indicator – an "on" state and an "off" state. The on state
consists of the on/off variable being set to true, along with the order opening condition. The off state
simply consists of the on/off variable being set to false.
if((UseStochastic == true && Kline > Dline) || UseStochastic == false)
{
// Buy order
}
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