Lua语法学习笔记

注释符–

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。

Number：Lua中数字只有双精度类型，不区分浮点和整型。

局部变量用local声明，Lua默认变量是全局的。

不等于~=

while和repeat

indx = 1
while indx < 10 do
indx = indx + 1
end

repeat
indx = indx + 1
until indx > 10

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)
end

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

函数

function SetName(myString)

end

function 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]);
end
end

function 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

返回值return

function TimesTwo(myValue)
myValue = myValue*2
return myValue
end

a = 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,myTotal
end

a,b,c,d = ThreeDice()

assert函数

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

输出：

helloworld

math.floor:向下取整，四省五入的话先加0.5在向下取整

math.random()

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

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 myValue
end

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

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 = "(309) 555-1234"
print(string.gsub(a,"%(%d%d%d%)","(781)"))
--(781) 555-1234

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

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)
end
end

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)
end

for index = 1,table.getn(myNames) do
print(index,myName[index])
end

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