Operators

Operators such as addition +, string concatenation .., and even the assignment operator = have been used throughout this book. Let's take some time to cover in detail what operators are and how they work. Operators fall into one of the following categories:

• Arithmetic operators do math.
• Relational operators always return a Boolean value: true or false. Relational operators are used to compare the relationship between two things, for example, by checking whether one number is smaller than another number.
• Logical operators express complex relations such as and/or. For example, logical operations can be used to check whether a number is less than seven AND greater than two.
• Misc operators: All other operators, such as assignment, fall into this category.

Operators can be unary or binary. A unary operation works on only one operand. For example, the minus sign (-) is the unary negation operator. It returns the negative value of a number:

x = -7 -- negation operator applied to the constant 7
y = -x -- negation operator applied to the x variable
-- x: -7, y: 7

A binary operator on the other hand operates on two operands. The binary subtraction operator also uses the minus sign (-), but it is a completely different operator from its unary counterpart. An example of the binary subtraction operator would be:

x = 7 - 3 -- Operand 1 is the constant 7, Operand 2 is the constant 3
y = x - 1 -- Operand 1 is the variable x, Operand 2 is the constant 1
z = x - y -- Operand 1 is the variable x, Operand 2 is the variable y

Most operators will be binary, that is, they will work on two operands.