Types and Values

Lua is a dynamically typed language. There are no type definitions; This means that each value contains its own value.

Lua doesn’t have variable data types, but weirdly enough its values carries the type with it. Here is a table listing all eight Lua value types.

Value Type	Description
`nil`	The absence of a useful value
`boolean`	`true` or `false`
`number`	Real (double-precision floating-point) numbers
`string`	Array of characters
`function`	Compute and return values
`table`	Ordinary arrays (key->value pairs)
`userdata`	Arbitrary C data
`thread`	Independent coroutines (lightweight threads)

Detecting Types

Lua has a function named type which enables us to know the type of a value. Here are some examples of how to use the type(value: any) -> string function.

print(type("Hi World"))  --> string
print(type(5.4*2))      --> number
print(type(print))       --> function
print(type(type))        --> function
print(type(true))        --> boolean
print(type(nil))         --> nil
print(type(type(X)))     --> string

Output
When you run the following code above you get these results:

string
number
function
function
boolean
nil
string

Variables have no predfine types in Lua; this means that any variable you define can use the value of any type.

print(type(a))   --> nil   (`a' is not initialized)
a = 10
print(type(a))   --> number
a = "a string!!"
print(type(a))   --> string
a = print        -- yes, this is valid!
a(type(a))       --> function

Output

nil
number
string
function

tip

When you write Lua code it is highly recommanded that you do not use a single variable for many diffrent types--as this makes the code a mess and may end up confusing you or new people trying to learn from your code.

This wraps up this very valuable tutorials on types and values. For more information, reference the offical Lua manual on basic types: Lua 5.4 Reference Manual

Detecting Types​

Detecting Types