Operators

Operators are the base commands each programming language is built on. They provide ability to perform basic mathematical and logical operations.

Requirements

To understand this article, you should read the following articles:

• Variables

Terms

Operand

An operand is any value given to an operator.

Expression

An expression is basically any code that returns a value. Read Expression for more information.

Unary Operator

An unary operator is an operator that requires only one operand.

Unary operation:

operator expression

Binary Operator

A binary operator is an operator that requires two operands.

Binary operation:

expression operator expression

Assignment Operators

Assignment operators are used to assign values to a variable. OFP's scripting language provides only one assignment operator.

Assignment:

identifier = expression

Example 1:

a = b

You might think that this operator compares a and b, but that is not the case. '=' simply sets the left value to be the right one. There don't exist any other assignment operators like '+=', '-=' etc., that can be found in other programming languages.

Example 2:

a = b*c

Arithmetic Operators

Remember arithmetic operations from school? These work just the same way.

All operands of arithmetic operations must be Numbers. Arithmetic operations always return a Number.

Unary arithmetic operators

Operator	Name	Example
-	Negation	-a

Binary arithmetic operators

Operator	Name	Example
+	Addition	a + b
-	Substraction	a - b
*	Multiplication	a * b
/	Division	a / b
%	Modulo	a % b
^	Raise to the power of	a ^ b

Modulo returns the remainder of the division a / b.

Logical Operators

Logical operators evaluate Boolean values. All operands of logical operations are Booleans.

A logical operation always returns a Boolean.

Unary logical operators

Operator	Name	Example
!	Not	!a
not	Not	not a

The Not-operator always returns the inverse Boolean value. If a Boolean a is true, !a returns false and vice versa.

Binary logical operators

Operator	Name	Example
&&	And	a && b
and	And	a and b
||	Or	a || b
or	Or	a or b

• && only returns true if both operands are true
• || returns true if one or both operands are true

There is no Xor, Nor and Nand operator. Those can be simulated using the basic operators though:

Combined logical operators

Name	Combination
Xor	(a || b) && !(a && b))
Nor	!(a || b)
Nand	!(a && b)

Comparison Operators

Comparison operators compare two values. Operands of comparisons may be Numbers and Strings.

Comparisons always return a Boolean: true if the comparison matches, false if not.

Comparison operators

Operator	Name	Example
==	Equal	a == b
!=	Not equal	a != b
<	Less than	a < b
>	Greater than	a > b
<=	Less or equal	a <= b
>=	Greater or equal	a >= b

Note: You can't compare Boolean values. Comparing a Boolean value with true is the same as the value itself. Comparing a Boolean value with false is the same as the inverse value.

a == true
// invalid, but equal to
a

a == false
// invalid, but equal to
!a

Array Operators

The scripting language offers own operators to deal with arrays. All operands, of course, have to be of type Array.

The return value of an array operation is an Array.

Unary array operators

Operator	Name	Example
+	Copy	+myArray

Normally arrays are assigned by reference. That means, if you assign array a to array b and change a afterwards, also b is changed. Use the copy operator to avoid this otherwise useful feature.

Example 1:

_arrayA = [1,2];
_arrayB = _arrayA;
_arrayA set [1,5];

_arrayA => [5,2]
_arrayB => [5,2]

Example 2:

_arrayA = [1,2];
_arrayB = +_arrayA;
_arrayA set [1,5];

_arrayA => [5,2]
_arrayB => [1,2]

Binary array operators

Operator	Name	Example
+	Concatenation	myArray1 + myArray2
-	Removal	myArray1 - myArray2

• + adds the second operand on the end of the first operand
• - removes all elements of the second operand from the first operand

Example 1:

_arrayA = [1,2];
_arrayB = [3,2,4];

_arrayC = _arrayA + _arrayB;

_arrayC => [1,2,3,2,4]

Example 2:

_arrayA = [1,2,3,2,4];
_arrayB = [2,3];

_arrayC = _arrayA - _arrayB;

_arrayC => [1,4]

String Operators

The scripting language offers one single string operator to concatenate strings. Both operands must be Strings.

The return value of a string operation is a String.

Expressions

Every expression is created from operands and operators. Operators call interpreter what it should do with operands. For example: AKMagazines * AmmoPerMagazine says: "multiple value in variable AKMagazines with value in variable AmmoPerMagazine". We evaluate expressions for obtain outcomes. If you want to store it, you must evaluate statement. For example: AllAKAmmo = AKMagazines * AmmoPerMagazine. It's order to interpreter to multiple value in variable AKMagazines with value in variable AmmoPerMagazine and prouuct store in variable AllAKAmmo (if there is any value, it will be rewritten). You need to know that expressions are evaluated from left side to right side, in statements is evaluated right expression first and outcome is stored in variable in left side. Another typical statement is VictorSide = side Victor or CarDamage = damage car.

Evaluating for outcome or side effects

When interpreter evaluates expression, gives you its outcome. Im most of cases it gives to you nothing, but it change something in game. (

PrivateHonka setDamage 1

increase global IQ of all army solders (kill him) ;-) ).

Operators

Operators in ArmA SL are implemented as commands (as everything). More important that previous information is that outcome of expression with arithmetic operators is number, when logical operators are used, its logical value (true or false (it's also commands which returns logical values. In other scripting languages (Python, etc.) is this value part of interpreter. (it's only small different, if you learn ArmA SL principles, you will be able to learn any other language (Python) easily). There you can see Arma SL has commands for everything.), it's data type is bool).

• Arithmetical operators
  • + // This operator can contact two strings too.
  • -
  • /
  • *
  • %
• Logical operators
  • == // if operands on left and right side are the same, outcome is true
  • != // it they are not the same, true
  • ! // it have one operand on left side. Outcome is operands negated value
  • <
  • >
  • >=
  • =<

Changing variable type

This operation is there limited, you can only retype to string with help of format command. Its primary function is similar to printf command in C - it replace %1, %2, %3... if occur in string given as 0. element of given array with outcome of expressions in first (%1), second(%2)... array elements - there is one different: it returns created array, not print it.

text = format ["Player side: %1 - Human players on that side: %2", side player, playersNumber side player]

Now we have string about situation in game. If you are confused you don't see expression in our example, know that 'value of expression where is only variable or number without operators is the same as variable or number value, howgh'.

What's next?

control structures

<< Variables | Control Structures >>