string 字符串库
- len(s) 长度
- rep(s,n) sn次 print( string.rep( "" , 5 ) ) --> *****
- lower(s) 将 s 字符串中的大写字母转为 小写
- upper(s) 将 s 字符串中的小写字母转为 大写
- sub(s,i,j) 复制 s 字符串 从第i位 到 第j位结束
- char(n) 将 acs码转化为字符 print( string.char( 97 , 98 , 99 ) ) --> abc
- byte(s,i,j) 将 s(字符串)中从 第i个字符到第j个 转为acs码
- print( string.byte( "sadfsadfsad" ) ) --> 115
- print( string.byte( "sadfsadfsad" , 1 ) ) --> 115
- print( string.byte( "sadfsadfsad" , 1 , 3 ) ) --> 115 97 100
- format -- c语言 printf("%s",v)
- print( string.format( "pi=%.4f" , math.pi ) ) --> pi=3.1416
示例代码
print( string.rep( "*" , 5 ) )
print( string.lower( "KLJKiuiouioKLJK") )
a = { "ax" , "Dy" , "pk" , "bJlLk" }
table.sort(
a ,
function(a,b)
return string.lower(a) < string.lower(b)
end
)
print( table.concat(a,",") )
s = "[asdfjsalfksajflsa]"
print( string.sub( s , 2 , #s-1 ) )
print( string.char( 97 , 98 , 99 ) )
print( string.byte( "sadfsadfsad" ) )
print( string.byte( "sadfsadfsad" , 1 ) )
print( string.byte( "sadfsadfsad" , 1 , 3 ) )
print( string.format( "pi=%.4f" , math.pi ) )
d = 5 ; m = 11 ; y = 1990
print( string.format("%02d/%02d/%04d",d,m,y) ) --> 05/11/1990
tag , title = "h1" , "a titile"
print(string.format("<%s>%s<%s>",tag,title,tag)) --> <h1>a titile<h1>
- 模式匹配函数
- string.find
- string.match
- string.gsub
- string.gmatch
示例代码 :
s = "hello world"
print( string.find(s,"hello") ) --> 1 5
print( string.find(s,"world") ) --> 7 11
print( string.find(s,"l" ) ) --> 3 3
print( string.find(s,"l",4 ) ) --> 4 4
print( string.find(s,"lasfsaf") ) --> nil
local t = {} -- 存储索引的table
local i = 0
while true do -- 将 s 中所有的换行符位置保存在t中
i = string.find(s,"\n",i+1) -- 查找下一个换行符
if i == nil then break end
t[#t+1] = 1
end
-----------------------
print( string.match("hello world" ,"hello") ) --> hello
date = " today is 17/7/1990"
print( string.match(date,"%d+/%d+/%d+") ) --> 17/7/1990 类似正则
------------------------
print( string.gsub( "Lua is cute" , "cute" , "greate" ) ) --> Lua is greate 1
s = string.gsub("all lii" , "l" , "x")
print(s) --> axx xii
s = string.gsub("Lua is great" , "Sol" , "Sun" )
print(s) --> Lua is great
s = string.gsub("all lii" , "l" , "x" , 1)
print(s) --> axl lii
------------------------
string.gmatch
words = {} -- 将 s 的所有字母存放到 words 中
for w in string.gmatch(s,"%a+") do -- %a 表示一个字母
words[#words + 1 ] = w
end
注意 :
模式:
字符分类:
%a 字母 %A(表示所有非字母的字符) (大写是小写的补集)
%c 控制字符 %C(表示非控制字符)
%d 数字零到九
%l 小写字母
%p 标点符号
%s 空白字符
%u 大写字母
%w 字母和数字
%x 十六进制数字
%z 内部表示为0的字符
魔法字符: ( ) . % + - * ? ^ $
%. 匹配一个 .
%% 匹配一个 %
...
字符集:
[%w_] 同时匹配 字母数字和下划线
nvow = select( 2 , string.gsub( text , "[AEOUaeiou]" ,"" ) ) -- 文本text中 元音字符的数量
[0-9] %d
^ 表示 非 [^0-7] 表示所有非八进制数字的字符
修饰符:
+ 一个以上 %a+ print(string.gsub("one, and two ; and three ", "%a+","word")) -- 把所有单词变成 word
* 0个以上
- 和*一样 , 但会匹配最短的子串 "[_%a][_%w]-"
? 匹配一个 [-+]? + 或 -
^ string.find(s,"^%d") 匹配 以数字开头的字符串
$ string.find(s,"%d$") 匹配 以数字结束的字符串
常用方法
- 多个捕获,需要加上小括号 %s表示空格
pair = "name=Anna"
key , value = string.match(pair,"(%a+)%s*=%s*(%a+)") -- 可多个捕获,需要加上小括号 %s表示空格
print(key , value)
date = "Today is 17/7/1990"
d , m , y = string.match(date,"(%d+)/(%d+)/(%d+)")
print(d,m,y) --> 17 7 1990
- %加数字表示捕获序号
s = [[then he said:"it's all right"!]]
q,quotedPart = string.match(s,"([\"'])(.-)%1")
print(q,quotedPart)
p = "%[(=*)%[(.-)%]%1%]"
s = "a=[[[ something]]]==]]=];print(a)"
print( string.match(s,p) )
local s = "abcdefg"
print(string.gsub(s,"(%w)(%w)(%w)","%3%2%1")) --cbafedg %加数字表示捕获序号
print(string.gsub("hello lua ! " , "%a" , "%O-%O" ))
print(string.gsub("hello lua","(.)(.)","%2%1"))
function trim(s)
return (string.gsub(s,"^%s*(.-)%s*$","%1"))
end
- 去除字符串两端的空格 trim(s)
s = " safdsaf "
print( trim(s) .. "aa" )
- $varname varname 利用属性值修改字符串
function expand(s)
return ( string.gsub(s,"$(%w+)",_G) )
end
name = "Lua"
status1 = "great"
print( expand( "$name is $status , isn't it ? " ) )
function expand(s)
return ( string.gsub(s,"$(%w+)",function(n)
return tostring(_G[n])
end
) )
end
status1 = "great"
print( expand( "$name is $status , isn't it ? " ) )
- "()" 空捕获应用
print( string.match("hello" , "()ll()" ) ) --> 3 5 分别是 e 和 o 的位置
URL编码 \ tab扩展
- URL编码解码
function unescape(s)
s = string.gsub( s , "+" , " " )
s = string.gsub( s , "%%(%x%x)" , function(h)
return string.char( tonumber( h , 16 ) ) -- tonumber( h , 16 ) 把16进制的h 转为 10进制的数字
end
)
return s
end
s = "a%2Bb+%3D+c"
print( unescape(s) )
cgi = { key1 = "1" , key2 = "2" , key3 = "3" }
function decode(s)
for name , value in string.gmatch( s , "([^&=]+)=([^&=]+)") do
name = unescape(name)
value = unescape(value)
cgi[name] = value
end
end
print( decode(cgi) )
function escape(s)
s = string.gsub( s , "[&=+%%%c]" , function(c)
return string.format("%%%02X",string.byte(c))
end)
s = string.gsub( s , " " , "+" )
return s
end
function encode()
local b = {}
for k , v in pairs(t) do
b[#b+1] = ( escape(k) .. "=" .. escape(v) )
end
return table.concat(b,"&")
end
t = { name = "al" , quer = "a+b=c" , q = "yes or no" }
print( encode(t) )
- tab 扩展
-- 需求 : 将字符串中的 制表符 转为 tab 个 空格 (默认为8个)
function expandTabs( s , tab )
tab = tab or 8 -- 制表符的大小默认为8
local corr = 0
s = string.gsub( s , "()\t" , function(p)
local sp = tab - (p-1+corr)%tab
corr = corr - 1 + sp
return string.rep(" ", sp)
end)
return s
end
s = "This is a book." -- this 和 is 之间 \ a 和 book 之间 有制表符
print( expandTabs(s) )
小技巧
test = [[char s[] = "a/*here";/*a tricky string */]]
-- 将 c 语言代码中的 注释代码 改为 <COMMENT>
print( string.gsub(test,"/%*.-%*/" , "<COMMENT>") ) --> char s[] = "a<COMMENT> 1 理想是 char s[] = "a/*here";<COMMENT>
-- "(.-)%$" -- (.-)匹配一个任意字符 -- 时间复杂度 n^2 n为字符串长度
-- "^(.-)%$" -- 时间复杂度 n
-- 小心空模式的使用
-- "%a*"
i , j = string.find(";$% **#$hello13" , "%a*")
print( i , j ) --> 1 0
-- "-" ".*" "[^\n]"
pattern = string.rep("[^\n]" , 70 ) .. "[^\n]*"
-- print( pattern )
-- x "[xX]"
function nocase(s)
s = string.gsub( s , "%a" , function(c)
return "[" .. string.lower(c) .. string.upper(c) .. "]"
end)
return s
end
print( nocase("Hi there!") ) --> [hH][iI] [tT][hH][eE][rR][eE]!
-- 对字符串进行预处理
s = [[follows a typical string:"This is \"great\"!.]] -- "\x" \ddd
function code(s)
return (string.gsub(s,"\\(.)",function(x)
return string.format("\\%03d",string.byte(x))
end))
end
function decode(s)
return (string.gsub(s,"\\(%d%d%d)" , function(d)
return "\\" .. string.char(d)
end))
end
s = code( s )
print(s)
s = string.gsub( s , '".-"' , string.upper )
print(s)
s = decode(s)
print(s)
