Lua 简易教程

print('Hello World!')

lua foo.lua

-- comment
--[[
    multi-line
    comment
]]

num = 42
fnum = 42.2
b = true
s = 'string'
t = "This is a immutable string."
u = [[ This is a multi-line
       string. ]]
t = nil -- undefines t

thisIsGlobal = 5 -- global by default
local localVal = 6

foo = undefinedVal -- foo -> nil
space = ' '
io.write('Hello' .. space .. 'World!')

while num < 50 do
    num = num + 1 -- no += or ++
end

if num > 40 then
    print('over 40')
elseif s ~= 'string' then
    io.write('less than 40')
else 
    local line = io.read()
    print('You typed: ' .. line)
end

aBoolValue = false
-- This is similar to the a?b:c operator in C/js:
aBoolValue = aBoolValue and 'yes' or 'no'  --> 'no'
if not aBoolValue then print('it was false') end

karlSum = 0
for i = 1, 100 do  -- includes 1 and 100
  karlSum = karlSum + i
end

-- begin, end[, step]
fredSum = 0
for j = 100, 1, -1 do fredSum = fredSum + j end

repeat
  print('the way of the future')
  num = num - 1
until num == 0

function fib(n)
  if n < 2 then return 1 end
  return fib(n - 2) + fib(n - 1)
end

function makeCounter()
    local count = 0 -- 局部变量，闭包捕获
    return function()
        count = count + 1
        return count
    end
end
local counter = makeCounter() -- 返回一个闭包
print(counter()) -- 输出 1
print(counter()) -- 输出 2
print(counter()) -- 输出 3

function adder(x)
  return function (y) return x + y end
end
a1 = adder(9)
a2 = adder(36)
print(a1(16))  --> 25
print(a2(64))  --> 100

m, n, j, k = 1, 2, 3 -- k = nil
x, y, z = 1, 2, 3, 4 -- 4 is thrown away.

function bar(a, b, c)
  print(a, b, c)
  return 4, 8, 15, 16, 23, 42
end

print("Hello")
print "Hello" -- works fine

local function g(x) return math.sin(x) end
local g; g = function (x) return math.sin(x) end

t = {key1 = 'value1', key2 = false}

print(t.key1)
t.newKey = {}
t.key2 = nil

u = {['@!#'] = 'Hello', [{}] = 1729, [6.28] = 'World'}
print(u['@!#'] .. ' ' .. u[6.28])
x = u[{}] -- x = nil

-- A one-table-param function call needs no parens:
function h(x) print(x.key1) end
h{key1 = 'Sonmi~451'}  -- Prints 'Sonmi~451'.

for key, val in pairs(u) do  -- Table iteration.
  print(key, val)
end

x = 42             -- 创建一个全局变量 x
print(_G.x)        -- 输出 42
_G.y = "Hello"     -- 创建一个全局变量 y
print(y)           -- 输出 "Hello"
local varName = "x"
print(_G[varName]) -- 输出 42
print(_G.varName)  -- 输出 nil
print(_G['_G'] == _G) -- true

v = {'value1', 'value2', 1.21, 'gigawatts'}
for i = 1, #v do  -- #v -> size of v
  print(v[i])  -- Indices start at 1 !! SO CRAZY!
end

t = {}
function t:func(x, y)
  self.x = x
  self.y = y
end
t:func(1, 1)
print(t.x) -- 1

-- same as
function t.func(self, x, y)
  self.x = x
  self.y = y
end

t.func(t, 1, 1)

-- mod.lua
local M = {}

local function sayMyName()
  print('Hrunkner')
end

function M.sayHello()
  print('Why hello there')
  sayMyName()
end

return M

-- Another file can use mod.lua's functionality:
local mod = require('mod')  -- Run the file mod.lua. (run once)
local mod2 = require('mod')  -- mod2 = mod, but not run mod.lua (cached)

--[[ require acts like:
local mod = (function ()
  <contents of mod.lua>
end)()
--]]

mod.sayHello() -- Prints: Why hello there Hrunkner
-- mod.sayMyName()  -- error

-- dofile is like require without caching:
dofile('mod2.lua')  --> Hi!
dofile('mod2.lua')  --> Hi! (runs it again)

-- loadfile loads a lua file but doesn't run it yet.
f = loadfile('mod2.lua')  -- Call f() to run it.

-- load is loadfile for strings.
-- (loadstring is deprecated, use load instead)
g = load('print(343)')  -- Returns a function.
g()  -- Prints out 343; nothing printed before now.

package.path = package.path .. ';../?.lua'
require("folder.subfolder.file")