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 [0,5];

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

Example 2:

_arrayA = [1,2];
_arrayB = +_arrayA;
_arrayA set [0,5];

_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.

Binary string operators

Operator	Name	Example
+	Concatenation	myString1 + myString2

• + concatenates adds the second operand on the end of the first operand

Example:

_stringA = "Hello ";
_stringB = "World!";

_stringC = _stringA + _stringB;

_stringC => "Hello World!"