Codectionary / Developer documentation / Lua

Lua Functions & Closures

Functions are first-class values in Lua: they can be stored, passed, and returned. A nested function can close over a local variable from its surrounding scope.

Syntax

local function add(left, right)
  return left + right
end

Examples

Creating a counter closure

A small, runnable example of this syntax.

local function make_counter()
  local count = 0
  return function()
    count = count + 1
    return count
  end
end

local next_count = make_counter()
print(next_count())  -- 1
print(next_count())  -- 2

Best practices

  • Prefer local function declarations for named helpers so they do not leak into the global environment.
  • Keep examples small while learning, then combine the idea with a real project.

At a glance

Purpose
Lightweight scripting and embedding
File extension
.lua
Runs in
Lua interpreter or a host application
Usually used with
Host APIs and Lua modules

Specifications & further reading

Related Lua documentation

Lua multiple return values
Lua reference for lua multiple return values.Lua closures
Lua reference for lua closures.Lua varargs
Lua reference for lua varargs.Lua colon methods
Lua reference for lua colon methods.