LUA Documentation

print(type(nil), type(true), type(10), type(1.5), type('x'), type({}), type(print))
-- nil boolean number number string table function

local count = 0              -- local to the block: always prefer this
globalVar = 1                -- global: shared by every file of the resource, avoid
local a, b = 1, 2            -- multiple assignment
a, b = b, a                  -- swap
local max <const> = 100      -- constant (5.4): assignment is an error

local label = player and player.name or 'unknown'
local half = total // 2

if hp <= 0 then
    die()
elseif hp < 30 then
    limp()
else
    walk()
end

for i = 1, 10 do end            -- 1..10
for i = 10, 1, -1 do end        -- counting down
for i, v in ipairs(list) do end -- array part, in order, stops at the first nil
for k, v in pairs(map) do end   -- every key, order not guaranteed
while cond do end
repeat until cond

local function add(a, b) return a + b end

local function stats(list)
    return #list, list[1]           -- several return values
end
local n, first = stats({4, 5, 6})

local function log(fmt, ...)       -- variable arguments
    print(string.format(fmt, ...))
end

local fn = function(x) return x * 2 end   -- anonymous function / closure

local list = { 'a', 'b', 'c' }          -- list[1] == 'a'  (Lua starts at 1)
local map = { name = 'Arthur', cash = 12.5 }
local set = { police = true, doctor = true }   -- fast membership test: set[job]

list[#list + 1] = 'd'                   -- append
table.insert(list, 'e')
table.insert(list, 1, 'first')          -- insert at position
table.remove(list, 1)                   -- remove at position
print(#list)                            -- length of the array part

local function deepCopy(v)
    if type(v) ~= 'table' then return v end
    local out = {}
    for k, x in pairs(v) do out[k] = deepCopy(x) end
    return out
end

local s = 'Hello'
print(s:upper(), s:lower(), s:len(), s:sub(2, 4), s:rep(2, '-'))
print(('%s has $%.2f'):format('Arthur', 12.5))
print(('a,b,c'):find(',', 1, true))      -- plain search: start, end
for word in ('one two'):gmatch('%a+') do print(word) end
print(('x=1'):gsub('%d', '9'))           -- replace, returns text and count

local Vec = {}
Vec.__index = Vec

function Vec.new(x, y) return setmetatable({ x = x, y = y }, Vec) end
function Vec:len() return math.sqrt(self.x ^ 2 + self.y ^ 2) end
Vec.__add = function(a, b) return Vec.new(a.x + b.x, a.y + b.y) end
Vec.__tostring = function(v) return ('(%s, %s)'):format(v.x, v.y) end

local v = Vec.new(3, 4) + Vec.new(0, 0)
print(v:len(), tostring(v))   -- 5.0  (3, 4)

local ok, err = pcall(function() error('boom') end)
if not ok then print('failed:', err) end

local ok2, res = xpcall(risky, debug.traceback)   -- keeps the stack trace
assert(type(x) == 'number', 'x must be a number')

local function round(n, places)
    local m = 10 ^ (places or 0)
    return math.floor(n * m + 0.5) / m
end

local co = coroutine.create(function(a)
    local b = coroutine.yield(a + 1)
    return b * 2
end)
print(coroutine.resume(co, 1))    -- true 2
print(coroutine.resume(co, 10))   -- true 20