LUA: Variables

A variable is a name given to a storage area that our programs can manipulate. It can hold different types of values including functions and tables.

The name of a variable can be composed of letters, digits, and the underscore character. It must begin with either a letter or an underscore. Upper and lowercase letters are distinct because Lua is case-sensitive. There are eight basic types of values in Lua −

In Lua, though we don't have variable data types, we have three types based on the scope of the variable.

Global variables − All variables are considered global unless explicitly declared as a local.

Local variables − When the type is specified as local for a variable then its scope is limited with the functions inside their scope.

Table fields − This is a special type of variable that can hold anything except nil including functions.

Variable Definition in Lua

A variable definition means to tell the interpreter where and how much to create the storage for the variable. A variable definition have an optional type and contains a list of one or more variables of that type as follows −

type variable_list;

Here, type is optionally local or type specified making it global, and variable_list may consist of one or more identifier names separated by commas. Some valid declarations are shown here −

local    i, j

local    i

local    a,c

The line local i, j both declares and defines the variables i and j; which instructs the interpreter to create variables named i, j and limits the scope to be local.

Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of an equal sign followed by a constant expression as follows:

type variable_list = value_list;

Some examples are

local d , f = 5 ,10     --declaration of d and f as local variables. 

d , f = 5, 10;          --declaration of d and f as global variables. 

d, f = 10               --[[declaration of d and f as global variables. Here value of f is nil --]]

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