Core library

print(math.sqrt(true))

luascript: Type "boolean" could not be converted into "number" at line 1

print(type(10), type(2.5), type("hi"), type({}), type(print))
print(typeof(10), typeof(2.5), math.type(10))
print(sizeof("hello"), sizeof({ 1, 2, a = 3 }), sizeof(10))
print(tostring(3), tostring(3.0), tostring(nil))
print(tonumber("42"), tonumber("0x1F"), tonumber("ff", 16), tonumber("nope"))
print(_VERSION)

number	number	string	table	function
integer	float	integer
5	3	8
3	3.0	nil
42	31	255	nil
Lua 5.4

local t = { "a", "b", "c", name = "letters" }
for i, v in ipairs(t) do io.write(i, "=", v, " ") end
print()
for k, v in pairs(t) do io.write(tostring(k), "=", tostring(v), " ") end
print()
print(next({}))                         -- an empty table has no first key
print(select("#", 1, nil, 3))           -- counts trailing nils too
print(select(2, "x", "y", "z"))

1=a 2=b 3=c 
1=a 2=b 3=c name=letters 
nil
3
y	z

local ok, err = pcall(function() error("boom") end)
print(ok, err)
 
local ok3, e = pcall(error, { code = 42 })  -- error values need not be strings
print(ok3, e.code)
 
local ok2, msg = xpcall(function() error("deep") end, function(e)
  return "handled: " .. e
end)
print(ok2, msg)
 
print(assert(1 + 1 == 2, "math is broken"))
print(pcall(assert, false, "assertion message"))

false	errors.lsc:1: boom
false	42
false	handled: errors.lsc:7: deep
true	math is broken
false	assertion message

local defaults = { color = "red", size = 1 }
local item = setmetatable({ size = 3 }, { __index = defaults })
print(item.color, item.size, rawget(item, "color"))
print(getmetatable(item).__index == defaults)
 
local f = load("return 1 + ...")
print(f(41))
print(load("return +"))

red	3	nil
true
42
nil	unexpected '+' at start of expression at line 1, column 8.

local s = "Hello, LuaScript"
print(#s, s:upper(), s:sub(1, 5), s:sub(-6))
print(s:find("Lua"))                        -- start and end index
print(("1.5"):find("."), ("1.5"):find(".", 1, true))  -- pattern vs plain
print(s:match("(%a+), (%a+)"))
print(("a,b,,c"):gsub(",", ";"))
print(string.format("%-6s|%5.2f|%04d|%q", "id", math.pi, 42, "a\"b"))
print(("ab"):rep(3, "-"), ("abc"):reverse(), ("A"):byte(), string.char(72, 105))
 
for word in ("one two three"):gmatch("%a+") do io.write(word, ".") end
print()
 
local packed = string.pack(">I2 s1", 513, "hi")
print(#packed, string.unpack(">I2 s1", packed))

16	HELLO, LUASCRIPT	Hello	Script
8	10
1	2	2
Hello	LuaScript
a;b;;c	3
id    | 3.14|0042|"a\"b"
ab-ab-ab	cba	65	Hi
one.two.three.
5	513	hi	6

local t = { 5, 2, 8 }
table.insert(t, 1)                 -- append
table.insert(t, 1, 9)              -- insert at position 1
print(table.concat(t, ", "))
print(table.remove(t), table.remove(t, 1))
table.sort(t)
print(table.concat(t, " "))
table.sort(t, function(a, b) return a > b end)
print(table.concat(t, " "))
 
local p = table.pack(10, nil, 30)
print(p.n, table.unpack({ "x", "y", "z" }, 2))
print(table.concat(table.move({ 1, 2, 3 }, 1, 3, 2, {}), ",", 2, 4))

9, 5, 2, 8, 1
1	9
2 5 8
8 5 2
3	y	z
1,2,3

local mathx = require("math")   -- the module: keep it under its own name
 
print(math.type(3), math.type(3.0), math.maxinteger)    -- global only
print(mathx.cbrt(-27), mathx.clamp(15, 0, 10))          -- module only
print(mathx.mean({ 2, 4, 9 }), math.deg(math.pi))       -- deg/rad: both

integer	float	9223372036854775807
-3.0	10.0
5.0	180.0

print(math.floor(3.7), math.ceil(3.2), math.abs(-3), math.sqrt(16))
print(7 // 2, 7 / 2, 7 % 3, 2 ^ 10)
print(math.max(2, 9, 4), math.min(2, 9, 4), math.tointeger(5.0))
print(math.fmod(-7, 3), -7 % 3)

3	4	3	4.0
3	3.5	1	1024.0
9	2	5
-1	2

local gen = coroutine.wrap(function()
  for i = 1, 3 do coroutine.yield(i * 10) end
end)
print(gen(), gen(), gen())
 
local co = coroutine.create(function(a)
  local b = coroutine.yield(a + 1)
  return b * 2
end)
print(coroutine.resume(co, 1))
print(coroutine.status(co))
print(coroutine.resume(co, 10))
print(coroutine.status(co))

10	20	30
true	2
suspended
true	20
dead

local home: number = os.getenv("HOME")

luascript: Type "string | nil" could not be converted into "number" at line 1

print(os.date("!%Y-%m-%d %H:%M", 86400 * 365))     -- "!" formats in UTC
 
local t = os.time({ year = 2026, month = 1, day = 1, hour = 12 })
print(os.date("%Y-%m-%d %H:%M", t))                -- round-trips in local time
 
local d = os.date("*t", t)
print(d.year, d.month, d.day, d.wday)
 
print(os.difftime(t + 90, t))
print(os.getenv("NO_SUCH_VARIABLE"))
 
local start = os.clock()
for _ = 1, 1e5 do end
print(os.clock() - start >= 0)

1971-01-01 00:00
2026-01-01 12:00
2026	1	1	5
90.0
nil
true

local f = assert(io.open("notes.txt", "w"))
f:write("first line\n", "second line\n", 42, "\n")
f:close()
 
for line in io.lines("notes.txt") do
  io.write("[", line, "] ")
end
print()
 
local r = assert(io.open("notes.txt", "r"))
print(r:read("l"))         -- one line, without the newline
print(r:read("n"))         -- nil: "second" is not a number
print(r:seek("set", 0))    -- back to the start; returns the position
print(#r:read("a"))        -- the whole file
r:close()
print(io.type(r), io.type(io.stdout), io.type(42))
os.remove("notes.txt")

[first line] [second line] [42] 
first line
nil
0
26
closed file	file	nil

local s = "héllo, wörld"
print(#s, utf8.len(s))                        -- bytes vs characters
print(utf8.char(72, 233, 8364))
print(utf8.codepoint(s, 2))
for pos, cp in utf8.codes("aé") do print(pos, cp) end
print(utf8.offset(s, 3))                      -- byte where the 3rd char starts
for ch in s:gmatch(utf8.charpattern) do io.write(ch, "|") end
print()

14	12
Hé€
233
1	97
2	233
4
h|é|l|l|o|,| |w|ö|r|l|d|