add.lua:

function add(x, y)
    return x + y
end

average.lua:

avg, sum = average(10, 20, 30, 40, 50)

print("The average is ", avg)
print("The sum is ", sum)

> luac -o test.luac test.lua

a = 18
print("hello world")

local _class = {}

function class(super)
    local class_type = {}
    class_type.ctor = false
    class_type.super = super
    class_type.new = function(...)
        local obj = {}
        do
            local create
            create = function(c, ...)
                if c.super then create(c.super, ...) end
                if c.ctor then c.ctor(obj, ...) end
            end

            create(class_type, ...)
        end
        setmetatable(obj, {__index = _class[class_type]})
        return obj
    end
    local vtbl = {}
    _class[class_type] = vtbl

    setmetatable(class_type, {__newindex = function(t, k, v) vtbl[k] = v end})

    if super then
        setmetatable(vtbl, {
            __index = function(t, k)
                local ret = _class[super][k]
                vtbl[k] = ret
                return ret
            end
        })
    end

    return class_type
end

base_type = class() -- 定义一个基类 base_type

function base_type:ctor(x) -- 定义 base_type 的构造函数
    print("base_type ctor")
    self.x = x
end

function base_type:print_x() -- 定义一个成员函数 base_type:print_x
    print(self.x)
end

function base_type:hello() -- 定义另一个成员函数 base_type:hello
    print("hello base_type")
end

test = class(base_type) -- 定义一个类 test 继承于 base_type

function test:ctor() -- 定义 test 的构造函数
    print("test ctor")
end

function test:hello() -- 重载 base_type:hello 为 test:hello
    print("hello test")
end

a = test.new(1) -- 输出两行，base_type ctor 和 test ctor 。这个对象被正确的构造了。
a:print_x() -- 输出 1 ，这个是基类 base_type 中的成员函数。
a:hello() -- 输出 hello test ，这个函数被重载了。

function A()
    collectgarbage("collect") -- 进行垃圾回收，减少干扰
    PrintCount()
    local a = {}
    for i = 1, 5000 do
        table.insert(a, {})
    end
    PrintCount()
    collectgarbage("collect")
    PrintCount()
end

A()
PrintCount()
collectgarbage("collect")
PrintCount()

function A()
    collectgarbage("collect") -- 进行垃圾回收，减少干扰
    PrintCount()
    a = {} -- 修改1
    for i = 1, 5000 do
        table.insert(a, {})
    end
    PrintCount()
    collectgarbage("collect")
    PrintCount()
end

A()
PrintCount()
collectgarbage("collect")
PrintCount()

-- 修改2
a = nil
collectgarbage("collect")
PrintCount()

function obj:fun()
  print(self.x)
end

等价于

function obj.fun(self)
  print(self.x)
end

-- pairs: 迭代表。
t = { a = "apple", b = "baby", c = "cool" }
for k, v in pairs(t) do print(k, v) end
b   baby
a   apple
c   cool

-- ipairs: 迭代数组。遇到nil退出。
t = {"one", "two", "three"}
for i, v in ipairs(t) do print(i, v) end
1   one
2   two
3   three

-- 获取长度
t1 = {1, 2, 3}
t2 = {1, nil, 2}
t3 = {1, 2, nil, 3}
print(#t1) -- 3 ok
print(#t2) -- ? undefined
print(#t3) -- ? undefined

-- 非空判断
function isTableEmpty(t)
    return t == nil or next(t) == nil
end

-- string转table
s = "{1, 2, 3}"
t = load("return " .. s)()
print(t) -- table: 0x...

-- pcall
> =pcall(function(i) print(i) error('error..') end, 33)
33
false        stdin:1: error..

-- xpcall
> =xpcall(function(i) print(i) error('error..') end, function() print(debug.traceback()) end, 33)
33
stack traceback:
stdin:1: in function <stdin:1>
[C]: in function 'error'
stdin:1: in function <stdin:1>
[C]: in function 'xpcall'
stdin:1: in main chunk
[C]: in ?
false        nil

-- 暴力热更
function reload_module(module_name)
  package.loaded[module_name] = nil
  require(module_name)
end

-- 优化热更
function reload_module(module_name)
  local old_module = _G[module_name]

  package.loaded[module_name] = nil
  require(module_name)

  local new_module = _G[module_name]
  for k, v in pairs(new_module) do
    old_module[k] = v
  end

  package.loaded[module_name] = old_module
end

-- Lume实现
lume.hotswap("lume") -- Reloads the lume module
assert(lume.hotswap("inexistant_module")) -- Raises an error

-- 官方实现 http://lua-users.org/wiki/TableUtils
function table.val_to_str ( v )
  if "string" == type( v ) then
    v = string.gsub( v, "\n", "\\n" )
    if string.match( string.gsub(v,"[^'\"]",""), '^"+$' ) then
      return "'" .. v .. "'"
    end
    return '"' .. string.gsub(v,'"', '\\"' ) .. '"'
  else
    return "table" == type( v ) and table.tostring( v ) or
      tostring( v )
  end
end

function table.key_to_str ( k )
  if "string" == type( k ) and string.match( k, "^[_%a][_%a%d]*$" ) then
    return k
  else
    return "[" .. table.val_to_str( k ) .. "]"
  end
end

function table.tostring( tbl )
  local result, done = {}, {}
  for k, v in ipairs( tbl ) do
    table.insert( result, table.val_to_str( v ) )
    done[ k ] = true
  end
  for k, v in pairs( tbl ) do
    if not done[ k ] then
      table.insert( result,
        table.key_to_str( k ) .. "=" .. table.val_to_str( v ) )
    end
  end
  return "{" .. table.concat( result, "," ) .. "}"
end

t = {['foo']='bar',11,22,33,{'a','b'}}
print( table.tostring( t ) )
-- {11,22,33,{"a","b"},foo="bar"}

-- Lume实现
lume.serialize({a = "test", b = {1, 2, 3}, false})
-- Returns "{[1]=false,["a"]="test",["b"]={[1]=1,[2]=2,[3]=3,},}"

lume.random([a [, b]])
lume.randomchoice(t)
lume.weightedchoice(t)
lume.shuffle(t)
lume.sort(t [, comp])
...