In the last section, you were introduced to the concepts of a variable and a value. This section explores the concept of what a value is. Every value has a data type, which intuitively describes what kind of data the value holds. Lua supports eight basic value types:
- nil: The absence of data. This type represents literal nothingness. If a certain piece of data is invalid or unknown, nil is usually the best way to represent that it is invalid or unknown.
- Boolean: A value of true or false. A Boolean value is binary and can only ever be in one of two states, true or false.
- number: A number can represent any real number: 0, -1, 5, or even decimals such as 3.14159265359.
- string: A string is an array of characters. When declaring a string literal, it must be "enclosed within quotation marks."
- function: A function is some code that is referred to by a name and can be executed any time.
- table: A table contains information using key-value pairs. Tables will be covered in depth in Chapter 3, Tables and Objects.
- userdata: Complex data structures defined in the C programming language.
- thread: Threads can be used to execute code in parallel. Instead of your code running one set of commands, it can run several sets of commands at the same time.
This section will explore the nil, Boolean, and number types. The string and function types will get their own sections in this chapter. The table type is so important it will have its own chapter.
Lua uses loose, implicit types. That means a variable can have any type. Once a variable is assigned a type, it can be assigned any other type. For example, it is valid to assign a number to a variable that holds a string. After the assignment, the variable will simply hold a number.