Lua快速入门实例

注：以下例子选自LuaForWindows(LFW)组件QuickLuaTour，对其中做了一些主要的翻译并加上了个人的理解注释，没有安装过LFW的朋友可以一看，虽然例子很简单，但是对初学者快速入门会有所帮助。

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关键词：Lua、Lua实例、QuickLuaTour、LFW、Lua入门

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-- Example 1???-- First Program.

-- Classic hello program.

print("hello")

-------- Output ------

Hello

-- Example 2???-- Comments.??注释

--单行注释以双连字符“--”开头多行注释“—[[”以开始，以“]]”结束

-- Single line comments in Lua start with double hyphen.??

--[[ Multiple line comments start?????????????????

with double hyphen and two square brackets.

??and end with two square brackets. ]]

-- And of course this example produces no

-- output,since it's all comments!

-- Example 3???-- Variables.

-- Variables hold values which have types,variables don't have types.

--变量的值拥有类型，变量没有类型

a=1

b="abc"

c={}

d=print

print(type(a))

print(type(b))

print(type(c))

print(type(d))

number

string

table

function

-- Example 4???-- Variable names.?变量命名

-- Variable names consist of letters,digits and underscores.

-- They cannot start with a digit.

--?变量的名称由字母、数字、下划线组成，但是不能以数字开始

one_two_3 = 123 -- is valid varable name??--合法命名

-- 1_two_3 is not a valid variable name. --以数字开始，不合法

-- Example 5???-- More Variable names.

--[[?在Lua中以下划线”_”开始的参数命名通常代表特殊的值，如（“_VERSION”），所以尽量不用使用以下划线开始命名。当时通常单个“_”代表虚假的参数。注：这是Lua的一个语法，后面将讲到，如：local _,x = string.find(s,p)? ]]

-- The underscore is typically used to start special values

-- like _VERSION in Lua.

print(_VERSION)

-- So don't use variables that start with _,

-- but a single underscore _ is often used as a

-- dummy variable.

-- Example 6???-- Case Sensitive.??大小写敏感

-- Lua is case sensitive so all variable names & keywords

-- must be in correct case.

--?在Lua中所有的变量和关键字都是大小写敏感的

ab=1

Ab=2

AB=3

print(ab,Ab,AB)

1???????2???????3

-- Example 7???-- Keywords.???Lua关键字

--[[ Lua的关键字大家可以去参考“Lua Reference Manual”，附：5.1版本的参考手册在线地址：http://www.lua.org/manual/5.1/index.html???变量命名的时候应避免使用关键字,应Lua是大小写敏感的，所以“and”是关键字，但“AND”不是是合法的命名，尽管如此，建议大家尽量不要用关键词(各种大小写版本)]]

-- Lua reserved words are: and,break,do,else,elseif,208)"> --?????end,false,for,function,if,in,local,nil,not,or,208)"> --?????repeat,return,then,true,until,while.

-- Keywords cannot be used for variable names,208)"> -- 'and' is a keyword,but AND is not,so it is a legal variable name.

AND=3

print(AND)

3

-- Example 8???-- Strings.

--[[字符串可以用双引号（“”）也可以用单引号（‘’），类似于JavaScript语法，对于多行字符串，使用“[[ ]]”括起来?]]

a="single 'quoted' string and double "quoted" string inside"

b='single 'quoted' string and double "quoted" string inside'

c= [[ multiple line

with 'single'

and "double" quoted strings inside.]]

print(a)

print(b)

print(c)

single 'quoted' string and double "quoted" string inside

?multiple line

and "double" quoted strings inside.

-- Example 9???-- Assignments.??赋值

--[[可以一次对多个变量赋值，规则：如果等号（“=”）右边多了，则舍弃，左边多了，则赋值为空（nil）?]]

-- Multiple assignments are valid.?

--??var1,var2=var3,var4

a,b,c,d,e = 1,2,"three","four",5

print(a,e)

1???????2???????three???four????5

-- Example 10???-- More Assignments.

-- Multiple assignments allows one line to swap two variables.

--?表达式?a,b=b,a表示a和b的值交换

1???????2

2???????1

-- Example 11???-- Numbers.

-- Multiple assignment showing different number formats.

-- Two dots (..) are used to concatenate strings (or a

-- string and a number). –?在Lua中两点“..”表示字符串连接，对应其他语言中的“+”连接

print("a="..a,"b="..b,"c="..c,"d="..d,"e="..e)

a=1?????b=1.123 c=1000000000????d=-123??e=0.0008

-- Example 12???-- More Output.

-- More writing output.??–多种输出方式或写法

print "Hello from Lua!"????--?不带括号

print("Hello from Lua!")???--?带括号，两者等价

Hello from Lua!

--[[什么时候可以省略括号???这是以种特殊的情况，只有当函数的参数只有一个，而且这个参数是字面上的字符串串（a literal string:即直接传字符串，而不是值为字符串的参数变量）或者蚕食是table结构。这两种情况才可以省略圆括号]]

-- Example 14???-- Tables.

--?表结构在Lua中特别常见，可以存储任何类型，很灵活。非常类似于JS中的一个对象。

-- Simple table creation.

a={} -- {} creates an empty table

b={1,3} -- creates a table containing numbers 1,3

c={"a","b","c"} -- creates a table containing strings a,c

table: 00410A58 table: 00410E90 table: 00410FB8

-- Example 15???-- More Tables.

-- Lua中表结构和JS中的对象一样可以随时增加或删除（直接赋值nil）属性。

--[[?读取有多种方式，可以用点“.”的方式，也可以用索引index,不过在Lua有点特殊，首先索引是从一开始，其次index=1并不一定是第一个元素值，比如下面的address[1]=nil，而不是“Wyman Street”,具体的以后在讲]]

-- Associate index style.

address={} -- empty address

address.Street="Wyman Street"

address.StreetNumber=360

address.AptNumber="2a"

address.City="Watertown"

address.State="Vermont"

address.Country="USA"

print(address.StreetNumber,address["AptNumber"])

360?????2a

-- Example 16???-- if statement.??if语句

-- Lua中的语句块语法有点类似VB都是以end结束

-- Simple if.

if a==1 then

????print ("a is one")

end

a is one

-- Example 17???-- if else statement.

b="happy"

if b=="sad" then

????print("b is sad")

else

????print("b is not sad")

b is not sad

-- Example 18???-- if elseif else statement

--?需要注意的是“elseif”?是连在一起的，这个和C#的?else if?不同

c=3

if c==1 then

????print("c is 1")

elseif c==2 then

????print("c is 2")

????print("c isn't 1 or 2,c is "..tostring(c))

c isn't 1 or 2,c is 3

-- Example 19???-- Conditional assignment.?条件语句

-- value = test and x or y

--注：value = test and x or y?等价于我们平时写的三元运算符（“？:”)的效果?value= test?x:y

b=(a==1) and "one" or "not one"

-- is equivalent to

????b = "one"

????b = "not one"

one

-- Example 20???-- while statement.

--?while语句

while a~=5 do -- Lua uses ~= to mean not equal

????a=a+1

????io.write(a.." ")

2 3 4 5

-- Example 21???-- repeat until statement.

a=0

repeat

????print(a)

until a==5

1

2

4

5

-- Example 22???-- for statement.

--?for语句有两种变体，一种叫?Numeric for?,一种叫?Generic for?就是例23中的for…in结构

--[[ Numeric for?的语法为：

for var=exp1,exp2,exp3 do something end

??等价于C#中的：for(int i=exp1; i<=exp2; i+=exp3) { something }

??]]

-- Numeric iteration form.

-- Count from 1 to 4 by 1.

for a=1,4 do io.write(a) end

print()

-- Count from 1 to 6 by 3.

1234

14

-- Example 23???-- More for statement.

--?for语句的Generic for变体

-- Sequential iteration form.

for key,value in pairs({1,3,4}) do print(key,value) end

1???????1

2???????2

3???????3

4???????4

-- Example 24???-- Printing tables.

--?用简单的方式遍历table结构，并输出

-- Simple way to print tables.

a={1,4,"five","elephant","mouse"}

for i,v in pairs(a) do print(i,v) end

5???????five

6???????elephant

7???????mouse

-- Example 25???-- break statement.

-- break is used to exit a loop.?

--?break关键字用于跳出循环，当然return也可以，不过有区别

while true do

????if a==10 then

????????break

????end

10

-- Example 26???-- Functions.

--?最简单的函数调用

-- Define a function without parameters or return value.

function myFirstLuaFunction()

????print("My first lua function was called")

-- Call myFirstLuaFunction.

myFirstLuaFunction()

My first lua function was called

-- Example 27???-- More functions.

--[[?带返回值的函数调用，大家注意a=mySecondLuaFunction("string")带了一个参数，但是mySecondLuaFunction定义并没有带参数，这个在Lua比较松，会直接忽略，即使你多写几个也没关系。]]

-- Define a function with a return value.

function mySecondLuaFunction()

????return "string from my second function"

-- Call function returning a value.

a=mySecondLuaFunction("string")

string from my second function

-- Example 28???-- More functions.

--[[?使用函数返回值对多个变量赋值，规则和多参数赋值一样，如果函数返回值多了，则抛弃，少了则少的赋值为nil??]]

-- Define function with multiple parameters and multiple return values.

function myFirstLuaFunctionWithMultipleReturnValues(a,c)

????return a,"My first lua function with multiple return values",1,true

1???????2???????three???My first lua function with multiple return values

1????????????????????????true

-- Example 29???-- Variable scoping and functions.?变量作用域

--[[?在Lua中，默认声明的变量为全局变量，以local?为修饰符的为局部变量，局部变量只在所属的语句块内有效]]

-- All variables are global in scope by default.

b="global"

-- To make local variables you must put the keyword 'local' in front.

function myfunc()

????local b=" local variable"

????a="global variable"

????print(a,208)"> myfunc()

global variable??local variable

global variable global

-- Example 30???-- Formatted printing.??字符串格式

--[[?字符串格式大家可以去参考Lua参考手册“Lua Reference Manual”http://www.lua.org/manual/5.1/index.html?这里重点说明一下在这些例子中第一次见到三个点“…”的作用，在Lua中在函数的参数列表中，表示参数的格式是可变不固定的，当这个函数在被调用时，函数的所有参数都被存储在一个名为arg的表结构中，同时arg还有一个n属性，代表实际传人的可变参数的个数，那么可以通过arg来访问所有的可变参数了，细节的以后再讲]]

-- An implementation of printf.

function printf(fmt,...)

????io.write(string.format(fmt,...))

printf("Hello %s from %s on %sn",208)"> ???????os.getenv"USER" or "there",_VERSION,os.date())

Hello there from Lua 5.1 on 08/11/11 16:48:19

-- Example 31???--[[

?Standard Libraries

??Lua has standard built-in libraries for common operations in

??math,string,table,input/output & operating system facilities.

?External Libraries

??Numerous other libraries have been created: sockets,XML,profiling,208)"> ??logging,unittests,GUI toolkits,web frameworks,and many more.

]]

-- Example 32???-- Standard Libraries - math.??Lua中标准的数学函数

--[[详细请参考Lua参考手册“Lua Reference Manual”?http://www.lua.org/manual/5.1/index.html??]]

-- Math functions:

-- math.abs,math.acos,math.asin,math.atan,math.atan2,208)"> -- math.ceil,math.cos,math.cosh,math.deg,math.exp,math.floor,208)"> -- math.fmod,math.frexp,math.huge,math.ldexp,math.log,math.log10,208)"> -- math.max,math.min,math.modf,math.pi,math.pow,math.rad,208)"> -- math.random,math.randomseed,math.sin,math.sinh,math.sqrt,208)"> -- math.tan,math.tanh

print(math.sqrt(9),math.pi)

?

3???????????3.1415926535898

-- Example 33???-- Standard Libraries - string.??Lua中string类库

-- String functions:

-- string.byte,string.char,string.dump,string.find,string.format,208)"> -- string.gfind,string.gsub,string.len,string.lower,string.match,208)"> -- string.rep,string.reverse,string.sub,string.upper

print(string.upper("lower"),string.rep("a",5),string.find("abcde","cd"))

LOWER???aaaaa???3???????4

-- Example 34???-- Standard Libraries - table.??Lua中的table类库

-- Table functions:

-- table.concat,table.insert,table.maxn,table.remove,table.sort

a={2}

table.insert(a,3);

table.sort(a,function(v1,v2) return v1 > v2 end)

1???????4

2???????3

3???????2

-- Example 35???-- Standard Libraries - input/output.??输入输出

--[[其中：io.write函数和print函数的功能相同都是输出显示，只是io.write输出后不换行]]

-- IO functions:

-- io.close,io.flush,io.input,io.lines,io.open,io.output,io.popen,208)"> -- io.read,io.stderr,io.stdin,io.stdout,io.tmpfile,io.type,io.write,208)"> -- file:close,file:flush,file:lines,file:read,208)"> -- file:seek,file:setvbuf,file:write

???????print(io.open("file doesn't exist","r"))

nil?????file doesn't exist: No such file or directory???2

-- Example 36???-- Standard Libraries - operating system facilities.?操作系统中类库

-- OS functions:

-- os.clock,os.date,os.difftime,os.execute,os.exit,os.getenv,208)"> -- os.remove,os.rename,os.setlocale,os.time,os.tmpname

print(os.date())

08/11/11 17:07:30

-- Example 37???-- External Libraries.?扩展类库

-- Lua has support for external modules using the 'require' function

-- INFO: A dialog will popup but it could get hidden behind the console.

require( "iuplua" )

ml = iup.multiline

????{

????expand="YES",208)"> ????value="Quit this multiline edit app to continue Tutorial!",208)"> ????border="YES"

????}

dlg = iup.dialog{ml; title="IupMultiline",size="QUARTERxQUARTER",}

dlg:show()

print("Exit GUI app to continue!")

iup.MainLoop()

-- Example 38???--[[

--??后续学习lua-users wiki

?To learn more about Lua scripting see

?Lua Tutorials:?http://lua-users.org/wiki/TutorialDirectory

?"Programming in Lua" Book:?http://www.inf.puc-rio.br/~roberto/pil2/

?Lua 5.1 Reference Manual:

?????Start/Programs/Lua/Documentation/Lua 5.1 Reference Manual

?Examples: Start/Programs/Lua/Examples

]]