Types

Lua has eight base types and one composite. Values carry their type; variables do not. type(x) returns the type tag as a string.

For the syntax of literals, see Syntax. For operators that act on these values, see Operators.

The catalog

Type	What it holds
nil	The absence of a value.
boolean	true or false.
number	5.3+ distinguishes integer and float subtypes.
string	Immutable byte sequence.
function	First-class; Lua and C functions are both this type.
table	The one composite type.
userdata	Opaque blob owned by C code.
thread	A coroutine handle.

Pages

nil

The absence of a value.

nil

boolean

Falsy is only false and nil.

boolean

number

Integer vs float subtypes (5.3+).

number

string

Immutable byte sequences; not Unicode.

string

table

The one composite type; array, map, record.

table

function

First-class values; Lua and C functions.

function

userdata

Opaque host-side blob.

userdata

thread

Coroutine handle.

thread

Casting

tostring / tonumber and the few implicit conversions.

Casting

References

• Syntax for the literal forms behind each type.

• Operators for arithmetic, comparison, and concat semantics per type.

• Data Structures for the patterns tables support.

• Functions for first-class functions and closures.

• Concurrency for the thread type and coroutines.

• Lua 5.4 Reference Manual, The Type System.