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A variable of type Void is an undefined variable.

Undefining Variables

You can use nil to undefine variables.

myVar = 1;
myVar = nil;

myVar => undefined


No comparison with variables of this type will work.


// error
if (undefinedVar == ...) then ...
// error
if (undefinedVar == undefinedVar) then ...

In Operation Flashpoint, a Variable becomes undefined when it is assigned to an undefined value, or an expression which refers to an undefined value somewhere.


The String representation of an undefined variable is one of the following:

Anything: scalar bool array string 0xfcffffef (OFP)

Anything: scalar bool array string 0xe0ffffef (ArmA)

Nothing: scalar bool array string nothing 0xfcffffef

Number: scalar

Boolean: bool

Array: array

Caution: the string specification of the undefined variables is undocumented, and it is very likely to change in future version of the scripting language.

The reliable way to check if the variable is undefined is that it silently fails any expression evaluations on it.


defined=false;if var==var then {defined=true};if var!=var then {defined=true};
if !defined then {/*we know it is undefined here*/}

The code above should not work in Arma 2, as stated here.

In Armed Assault or later isNil is the preferred way to check for this, like

 isNil "varName"

Type Inference

Suppose the variable a is undefined, and we set the variable b like so:
b = a + []

The inferred type of b is now array - since b was the product result of an array add operation with a definite array ([]) and an unknown type (a)

b's string representation will now be 'array', and b wil be considered an undefined array.