Lua语法学习笔记

1. 注释符–
2. nil 表示变量还没有赋值。如果给一个变量赋值为nil，表示删除该变量。
3. Number：Lua中数字只有双精度类型，不区分浮点和整型。
4. 局部变量用local声明，Lua默认变量是全局的。
5. 不等于~=

6. while和repeat

   indx = 1while indx < 10 do    indx = indx + 1endrepeat    indx = indx + 1until indx > 10

7. for语句:Lua中的for语句循环次数在第一次就确定了，后面不改变

   for indx = 1,10 do    print(indx)endfor indx = 1,10,-1 do    print(indx)end

8. 函数

   function SetName(myString)endfunction SetName(...)    if arg.n >0 then        for indx = 1,arg.n do        local myString = string.format("%s%d","Argument ",indx,":")        end    else        print(myString,arg[indx]);    endendfunction Multiply(val1,val2,...)    local myString    if arg.n == 0 then        myString = string.format("%d%s%d%s%d",val1,"*",val2,"=",val1*val2)    else        local val3 = val1*val2*arg[1]        myString = tring.format("%d%s%d%s%d%s%d",val1,"*",val2,"*",arg[1],"=",val3)    end    print(myString)end

9. 返回值return

   function TimesTwo(myValue)    myValue = myValue*2    return myValueenda = 24 + TimesTwo(12)print(a)function ThreeDice()    d1 = math.random(1,6)    d2 = math.random(1,6)    d3 = math.random(1,6)    myTotal = d1 + d2 +d3    return d1,d2,d3,myTotalenda,b,c,d = ThreeDice()

10. assert函数

    a = "hello world"b = "print(a)"assert(loadstring(b))()

    输出：
    helloworld

11. math.floor:向下取整，四省五入的话先加0.5在向下取整

12. math.random()

    myDie = math.random(1,6)--设置随机数发生种子\math.randomseed(os.date(%d%H%M%S))

13. math.min()：判断table里的数据最小值，与loadstring配合

    myTable = {7,1,13,6,89,4,56,2,54,6}function GetMin(theTable)    myString = "myValue = math.min("    for index,value in ipairs(theTable) do        myString = string.format("%s%d%s", myString, value, ",")    end    --remove final comma    myString = string.sub (myString, 1, string.len(myString) - 1)    myString = string.format("%s%s", myString, ")")    loadstring(myString)() --run the chunk    print(myString) -- see the string    print(myValue) --see the result    return myValueend

14. tonumber()
    tostring()
    string.char(10)换行
    string.len()
    string.sub(myString,start,end)截取子串,start可以为负数，从末尾开始截取string.sub(myString,start)
    string.format(“%d..”,int,..)
    string.find(myString,”…”)
    eg:
    myString = “My name is John Smith”
    sStart,sEnd = string.find(myString,”John”)
    print(sStart,sEnd)–12,15

15. 字符和格式：

    myString = "The price is $17.50."filter = "$%d%d.%d%d"print(string.sub(myString,string.find(myString,filter)))--$17.50

    string.gsub(sourceString,pattern,replacementString)--返回一个字符串，sourceString字符中，满足pattern格式的字符都会被替换成replacementString参数的值eg:

    myString = "My name is John Smith. My phone is 555-3257"newString = string.gsub(myString,"%d","*")--My name is John Smith. My phone is ***-***a = "[phone]"print(string.gsub(a,"%(%d%d%d%)","(781)"))--[phone]a = "happy, hello, home, hot, hudson"print(string.gsub(a,"h%a+","An H world!",2))--An H world!, An H world!, home, hot, hudson--查找以h开头的字符，%a+表示任意长度的字母，并在遇到空格和标点符号时为止，最后的参数2表示只替换最先遇到的两个string.gfind(string,pattern)注意是遍历字符串，只要满足指定格式就返回该子串a = "This is my rather long string."for v in string.gfind(a,"%a+") do    print(v)end--This  is  my  rather  long  string

16. table数据结构
    table.getn()
    table.sort()

    --sort有可选的参数, 此参数是一个外部函数, 可以用来自定义sort函数的排序标准.此函数应满足以下条件: --接受两个参数(依次为a, b), 并返回一个布尔型的值, 当a应该排在b前面时, 返回true, 反之返回false.--下面是一个逆序排序，当direction=1时逆序function Sort(theTable, direction)    if direction ~= 1 then        table.sort(theTable)    else        function Reverse(a, b)            if a < b then                return false            else                return true            end        end        table.sort(theTable, Reverse)    endend

    table.insert(myTable,position,value)默认是末尾table.remove(myTable,position) 默认是末尾，且返回去除值多维table

    widget = {}widget.name = {}widget.cost = {}widget.name[1] = "Can opener"widget.cost[1] = "$12.75"widget.name[2] = "Scissors"widget.cost[2] = "$8.99"

    pairs()：遍历table中的每一个元素

    myName = {"Fred","Ethel","lucy","Ricky"}for index,value in pairs(myName) do    print(index,value)endfor index = 1,table.getn(myNames) do    print(index,myName[index])end

17. I/O基础

    利用io可以生成可运行的lua文件，可以用于游戏数据或者游戏进度的保存

    myFile = io.open("xxx.lua","w")--文件不存在则新建 w代表写入if myFile ~= nil then    myFile:write("--Test lua file")    myFile:write(string.char(10))--换行    myFile:write(string.format("%s%s","--File created on:",os.date()))    myFile::write("print(\"helloworld!\")")    io.close(myFile)end